Security system with ferromagnetic sensing

Abstract

A safety system for policing a doorway comprising a door to an MRI room.

Description

[0001] Security System with Ferromagnetic Sensing

[0002] Field of the invention

[0003] The invention relates to a safety system for policing a doorway leading to an MRI room, where the system generates an alert if an unwanted or dangerous ferromagnetic object is about to enter the MRI room. In particular, though not exclusively, the invention relates to reducing the number of false, unnecessary or unwanted alarms generated by the safety system.

[0004] Background of the invention

[0005] Magnetic Resonance Imaging (MRI) is a well-known technique used to produce images useful in medical diagnosis. The MRI scanner used in this imaging technique produces extremely strong magnetic fields, which extend out from the MRI scanner. Ferromagnetic objects (e.g. keys, tools, medical implements, cylinders, gurneys, wheelchairs etc.) in the vicinity of these strong magnetic fields become strongly attracted to the MRI scanner, and in the process these ferromagnetic objects may become mobile or even dangerous projectiles.

[0006] If there is a person between the mobile and / or projectile ferromagnetic object and the MRI scanner, that person could be hit by the ferromagnetic object and so in the process may be harmed or even killed.

[0007] Additionally, mobile and / or projectile ferromagnetic objects can also damage the MRI scanner. MRI scanners are sensitive and expensive machines and if damaged patients lose access to a valuable medical resource, which may in turn delay diagnosis and follow-on medical treatments.

[0008] In view of these dangers, access to MRI scanners is strictly controlled. MRI scanners are typically located in special rooms in hospitals. Typically, there is only one doorway into the MRI room. Often that doorway is policed by a machine capable of detecting ferromagnetic objects and raising an alert if a ferromagnetic object is detected.

[0009] However, these safety systems can produce unnecessary alerts (hereafter 'false alarms'). For example a false alarm / alert may be generated when a person passes near the MRI doorway, but is not intending to enter the MRI room; or when a person entering the MRI room is only carrying a small ferromagnetic object that is in effect tethered / tied to the person (e.g. the metal wire in an underwire bra), and so does not present a threat.

[0010] An excessive number of false alarms can lead to 'alarm fatigue'.

[0011] Alarm fatigue is dangerous because it can cause people to ignore, or incorrectly override, the safety system. This re-introduces the risk of dangerous ferromagnetic items being allowed to enter the MRI room, leading to the possibility of damage being caused to sensitive and expensive medical equipment, or the possibility that anyone inside the MRI room could be injured or killed.

[0012] One important source of alarm fatigue is due to equipment entering the MRI room. MRI equipment is generally labelled "MR Conditional" meaning that it has been tested and found to be safe in MR, under defined and specified conditions. Such equipment is special to an MRI department. For example, one type of gurney may be labelled 'MR Conditional' and therefore is safe to use in an MRI room because it is constructed from non-magnetic materials and so won't get attracted to the MRI magnet. However, standard hospital gurneys are usually made of magnetic material (steel in particular), and these can cause major accidents if they are close enough to be attracted to an MRI magnet. These are usually unlabeled or labelled as 'MR Unsafe.' This kind of labeling is (or should be) applied to all equipment in or proximate to an MRI room area. Other common items that are regularly used in MRI rooms are wheelchairs, linen carts, docking tables, patient monitors, IV poles, and infusion pumps amongst others. Generally, 'MR Conditional' equipment may be used safely in MRI rooms whereas 'MR unsafe' equipment is dangerous, and unlabeled equipment is not known, but should be presumed to be dangerous. It should be noted that MR Conditional equipment is weakly magnetic, albeit not magnetic enough to be a hazard in an MRI room, yet often magnetic enough to trigger a ferromagnetic detection system. They are therefore a common source of false alarms.

[0013] It is against this background that the present invention has arisen.

[0014] Summary of the invention

[0015] In an aspect of the invention, there is provided a safety system for policing a doorway comprising a door to an MRI room, the system comprising:

[0016] (i) a passive ferromagnetic detector arranged to measure an ambient magnetic field within a ferromagnetic detection zone, and configured to identify temporal variations in the ambient magnetic field which indicate the presence of a target-sized or larger ferromagnetic object in the ferromagnetic detection zone, and to produce a corresponding ferromagnetic assessment output;

[0017] (ii) a door register arranged to identify if the door is closed, and to produce a corresponding door assessment output;

[0018] (iii) a person register arranged to identify the intended path of travel for each person traveling in a person detection zone and to determine if the intended path of travel is through the doorway into the MRI room, and to produce a corresponding person assessment output;

[0019] (iv) an end-user alert arranged to receive the ferromagnetic assessment output, the door assessment output and the person assessment output;

[0020] and wherein in use, the end-user alert is configured to raise an alert when

[0021] • the ferromagnetic assessment output indicates the presence of a target-sized or larger ferromagnetic object in the ferromagnetic detection zone,

[0022] • the door assessment output indicates the door is not closed, and

[0023] • the person assessment output indicates that the intended path of travel for a person in the person detection zone is through the doorway into the MRI room. Advantageously, the safety system provides reduced instances of false alarms, which may lead to alert fatigue. Alarm fatigue is a serious problem because it can lead to users ignoring the generated safety alerts, or even temporarily or permanently turning off the associated safety warning systems. Ultimately, alert fatigue puts users and patients in danger by inadvertently permitting ferromagnetic objects to enter the MRI room. Ferromagnetic objects may become dangerously mobile when exposed to the very strong magnetic field of the MRI scanner. Flying metal objects may harm any person struck by the object and / or may damage the MRI equipment. MRI equipment is very expensive, and while any equipment is replaced or repaired, patients will lose access to vital medical procedures. In an embodiment the system determines if the person in the person detection zone who is about to pass through the doorway is carrying the ferromagnetic object that has been detected.

[0024] In this aspect of the invention an alert is generated only when:

[0025] a. the ferromagnetic assessment output indicates the presence of a target-sized or larger ferromagnetic object in the ferromagnetic detection zone (i.e. the system has detected a threat sized (or larger) metal object moving in the detection zone) and

[0026] b. the door assessment output indicates the door is not closed, (i.e. the system recognizes that it is possible for the threat object to enter the MRI room because the door is not closed) and

[0027] c. the person assessment output indicates that the intended path of travel for a person in the person detection zone is through the doorway into the MRI room (i.e. the system recognizes that it is possible and indeed likely that a person is about to enter the MRI room).

[0028] So, if any of the above conditions (a) to (c) are not met, then the system will not produce an alert. For example, no alert is generated if only the below conditions are met:

[0029] only (a)+(b) - i.e. there is no person about to enter the MRI room; or

[0030] only (a)+(c) - i.e. the door is closed; or

[0031] only (b)+(c) - i.e. there is no threat object in the detection zone.

[0032] The same is true when even fewer conditions are met, e.g. if just condition (a) is met and the rest of the conditions are unmet, then an alert will not be generated.

[0033] In an embodiment, further the end-user alert is configured to raise the alert when

[0034] • the ferromagnetic assessment output indicates the presence of a larger than target sized ferromagnetic object in the ferromagnetic detection zone,

[0035] • the door assessment output indicates the door is not closed, • the person assessment output indicates that the intended path of travel for a person in the person detection zone is through the doorway into the MRI room,

[0036] • the person intending to enter the MRI room has been provided with

[0037] an end-user alert exception, optionally the person is an MRI approved operator and / or an MRI approved qualified hospital worker.

[0038] Advantageously, in some situations a person may be granted an exception to the generation of the alerts. This exception may be temporary or time limited. The exemption may change the nature of the alert, which for example may be less strident. For example, the person entering the room may be a trained / qualified user. Training for example may include how to ensure that target (or larger) sized ferromagnetic objects are suitably tethered / restrained before entering the MRI room, so that the object cannot become mobile or airborne in the presence of the strong MRI magnetic field. Sparing false alarms in this situation may lessen any alert fatigue. That said, the system may be arranged such that the end-user alert exception does not extend to the situation where very large ferromagnetic objects (e.g. larger than target sized) are about to enter the MRI room. This is because large ferromagnetic objects are particularly problematic and dangerous. So, when these larger objects are about to enter the MRI room, the end-user alert exception may be revoked, or a different kind of alert is generated. As a general rule detectable ferromagnetic objects (e.g. objects detectable by a suitably setup / calibrated ferromagnetic screening device, e.g. target sized objects) should not be allowed into an MRI room, in particular ones that could harm a person or equipment if they should become a projectile threat (e.g. projectile objects). The exception to this is where those objects are not too large and they are secured (e.g. secured target-sized objects; low threat objects; threat manageable objects; securable threat objects). A trusted and trained user may be given permission to enter the MRI room with those secured / tied target sized objects and without generating an alert. However, when the object is large enough so that they could pose a very serious threat to life and equipment and / or it is unrealistic to be able to secure these objects from moving under the influence of the MRI's strong magnetic field (e.g. larger than target sized objects; high threat objects; threat unmanageable objects; non-securable threat objects), then those objects should not be allowed to enter the MRI room when in operation; unless active precautions are taken to ensure that it is certain that those objects are safely secured.

[0039] By way of example, a radiographer may be permitted to carry target sized objects that are safe near an MRI scanner due to them being tethered, such as an underwired bra, wristwatch, or shoes with metal sole reinforcements. The safety-trained radiographer will know not to carry untethered target sized objects such as cell phones, haemostats, stethoscopes and small tools which are not safe. It is desirable, therefore, for the safety-trained radiographer to enter an MRI room without causing alerts whilst carrying tethered target sized objects. This avoids invoking a strict and undesirable clothing policy as a means to avoid alarm fatigue. It is important that for all other people, i.e., non-safety-trained people with target sized objects, tethered or not, that they should always trigger an alert. This is the purpose of the end-user exemption, which may be issued to safety-trained radiographers / personnel. However, even safety-trained radiographers / personnel should not take in larger than target sized objects (e.g. steel cylinders, MR Unsafe gurneys, wheelchairs, linen carts, patient monitors, IV poles, infusion pumps, floor buffers, or pallet carts; which generate significantly larger signals in a ferromagnetic detector (FMD) as compared to those of target sized objects) into an MRI room. In this case the full alert should be given despite the safety-trained radiographer / personnel having an end-user exemption. So, in particular, an alert may be raised even when a person bearing an end-user alert exception is about to enter the MRI room, if a larger than target sized ferromagnetic object has been detected. So, for example, in one case the alert will not be generated if the person bearing an end-user alert exception (e.g. a trained person) is wearing an underwired bra (i.e. target sized or smaller object) and is about to enter the MRI room, but in another example the alert will be generated if the trained person is instead carrying a metal wrench (i.e. a larger than target sized ferromagnetic object). Advantageously, the system can be configured to preserve the option to raise an alert when the trained person is potentially doing something a bit more risky than normal, e.g. by bringing into the MRI room a larger than target sized ferromagnetic object. The benefit is to reduce alert fatigue by only raising alerts in respect of a trained person in the potentially most risky scenarios.

[0040] The safety system may need to be calibrated such that target-sized ferromagnetic objects are detectable by the system, and further when larger than target sized ferromagnetic objects are detected by the system. This may be a simple matter of walking / moving such objects through the doorway and adjusting the corresponding alert triggering thresholds. The skilled person would be able to do this with their general skill and knowledge and may, if necessary, do this with the aid of a ferromagnetic safety system engineer.

[0041] In an embodiment, further the end-user alert is configured to raise an alternative alert when

[0042] • the ferromagnetic assessment output indicates the presence of a target-sized ferromagnetic object in the ferromagnetic detection zone,

[0043] • the door assessment output indicates the door is not closed, • the person assessment output indicates that the intended path of travel for a person in the person detection zone is through the doorway into the MRI room and

[0044] • the person intending to enter the MRI room has been provided with

[0045] an end-user alert exception, optionally the person is an MRI approved operator and / or an MRI approved qualified hospital worker.

[0046] Advantageously, it may be beneficial to have more than one kind of alert. For example, it may be useful to have an alternative alert raised when a person with an end-user alert exception is about to take a target sized ferromagnetic object into the MRI room, as compared to a (standard) alert when somebody else is about to do the same. In that way the response by the system and / or any nearby staff / person can be adjusted to suit the situation. For example, the alternative alert may be less conspicuous and / or less strident than the (standard) alert. For example, if the alert was a sound, the alternative alert may be a soothing musical tone / note as compared to the standard alert which might be a strident siren / buzzer. In that way, beneficially, the alternative alert may produce less overall alert / alarm fatigue with the trained users that must routinely enter the MRI room. The sound and its volume are both variables that may be pre-set or selectable by the users of the invention. The alternative alert may be to have no sound but just a visual warning or no visuals and only a sound. Alternatively, the alternative alert may have no visual and no sound component. Alternatively, the alternative alert may be no alert at all depending on need. In a further aspect of the invention, there is provided a safety system for policing a doorway comprising a door to an MRI room, the system comprising:

[0047] (i) a passive ferromagnetic detector arranged to measure an ambient magnetic field within a ferromagnetic detection zone, and configured to identify temporal variations in the ambient magnetic field which indicate the presence of a target-sized or larger ferromagnetic object in the ferromagnetic detection zone, and to produce a corresponding ferromagnetic assessment output;

[0048] (ii) a door register arranged to identify if the door is closed, and to produce a corresponding door assessment output;

[0049] (iii) a person register arranged to identify the intended path of travel for each person traveling in a person detection zone and to determine if the intended path of travel is through the doorway into the MRI room, and to produce a corresponding person assessment output;

[0050] (iv) a tagging register arranged to identify if any person in the person detection zone is bearing an authorisation tag, and to produce a corresponding tagging assessment output;

[0051] (v) an end-user alert arranged to receive the ferromagnetic assessment output, the door assessment output, the person assessment output and the tagging assessment output;

[0052] and wherein in use, the end-user alert is configured to raise an alert when

[0053] • the ferromagnetic assessment output indicates the presence of a target-sized or larger ferromagnetic object in the ferromagnetic detection zone,

[0054] • the door assessment output indicates the door is not closed, • the person assessment output indicates that the intended path of travel for a person in the person detection zone is through the doorway into the MRI room and

[0055] • the tagging assessment output indicates that the person intending to enter the MRI room is not bearing an authorisation tag. Advantageously, the safety system provides reduced instances of false alarms, which may lead to alert fatigue. Alarm fatigue as mentioned hereinabove is a serious problem because it can lead to users ignoring the generated safety alerts, or even temporarily or permanently turning off the associated safety warning systems. This puts users and patients in danger by inadvertently permitting ferromagnetic objects to enter the MRI room, and / or could lead to the damage the MRI equipment. In an embodiment the system determines if the person in the person detection zone who is about to pass through the doorway is carrying the ferromagnetic object that has been detected. In this aspect of the invention an alert is generated only when:

[0056] a. the ferromagnetic assessment output indicates the presence of a target-sized or larger ferromagnetic object in the ferromagnetic detection zone (i.e. the system has detected a threat sized (or larger) metal object moving in the detection zone) and

[0057] b. the door assessment output indicates the door is not closed, (i.e. the system recognizes that it is possible for the threat object to enter the MRI room because the door is not closed) and

[0058] c. the person assessment output indicates that the intended path of travel for a person in the person detection zone is through the doorway into the MRI room (i.e. the system recognizes that it is possible and indeed likely that a person is about to enter the MRI room) and

[0059] d. the tagging assessment output indicates that the person intending to enter the MRI room is not bearing an authorisation tag.

[0060] So, if any of the above conditions (a) to (d) are not met, then the system will not produce an alert. For example, no alert is generated if only the below conditions are met:

[0061] only (a)+(b)+(c) - i.e. the person about to enter the MRI room is bearing an authorisation tag; or

[0062] only (a)+(b)+(d) - i.e. there is no person about to enter the MRI room; or

[0063] only (a)+(c)+(d) - i.e. the door is closed; or

[0064] only (b)+(c)+(d) - i.e. there is no threat object in the detection zone.

[0065] The same is true when even fewer conditions are met, e.g. if just condition (a) is met and the rest of the conditions are unmet, then an alert will not be generated.

[0066] In a further aspect of the invention, there is provided a safety system for policing a doorway comprising a door to an MRI room, the system comprising:

[0067] (i) a passive ferromagnetic detector arranged to measure an ambient magnetic field within a ferromagnetic detection zone, and configured to identify temporal variations in the ambient magnetic field which indicate the presence of a target-sized or larger ferromagnetic object in the ferromagnetic detection zone, and to produce a corresponding ferromagnetic assessment output;

[0068] (ii) a door register arranged to identify if the door is closed, and to produce a corresponding door assessment output; (iii) a person register arranged to identify the intended path of travel for each person traveling in a person detection zone and to determine if the intended path of travel is through the doorway into the MRI room, and to produce a corresponding person assessment output;

[0069] (iv) a tagging register arranged to identify if any person in the person detection zone is bearing an authorisation tag, and to produce a corresponding tagging assessment output;

[0070] (v) an alert override register arranged to identify if an alert override has been activated when any person bearing an authorisation tag is proximate to an alert override activator, and to produce a corresponding override assessment output;

[0071] (vi) an end-user alert arranged to receive the ferromagnetic assessment output, the door assessment output, the person assessment output, the tagging assessment output and the override assessment output;

[0072] and wherein in use, the end-user alert is configured to raise an alert when

[0073] • the ferromagnetic assessment output indicates the presence of a target-sized or larger ferromagnetic object in the ferromagnetic detection zone,

[0074] • the door assessment output indicates the door is not closed, • the person assessment output indicates that the intended path of travel for a person in the person detection zone is through the doorway into the MRI room,

[0075] • the tagging assessment output indicates that the person intending to enter the MRI room is not bearing an authorisation tag, and

[0076] • the alert override was not activated when a person bearing an authorisation tag was proximate to the alert override activator.

[0077] Advantageously, the safety system provides reduced instances of false alarms, which may lead to alert fatigue. Alarm fatigue as mentioned hereinabove this is a serious problem because it can lead to users ignoring the generated safety alerts, or even temporarily or permanently turning off the associated safety warning systems. This puts users and patients in danger by inadvertently permitting ferromagnetic objects to enter the MRI room and / or could lead to the damage the MRI equipment. In an embodiment the system determines if the person in the person detection zone who is about to pass through the doorway is carrying the ferromagnetic object that has been detected. In an embodiment the alert override activator is portable and may be carried by an authorized person.

[0078] In this aspect of the invention an alert is generated only when:

[0079] a. the ferromagnetic assessment output indicates the presence of a target-sized or larger ferromagnetic object in the ferromagnetic detection zone (i.e. the system has detected a threat sized (or larger) metal object moving in the detection zone) and

[0080] b. the door assessment output indicates the door is not closed, (i.e. the system recognizes that it is possible for the threat object to enter the MRI room because the door is not closed) and

[0081] c. the person assessment output indicates that the intended path of travel for a person in the person detection zone is through the doorway into the MRI room (i.e. the system recognizes that it is possible and indeed likely that a person is about to enter the MRI room) and

[0082] d. the tagging assessment output indicates that the person intending to enter the MRI room is not bearing an authorisation tag and

[0083] e. the alert override was not activated when a person bearing an authorisation tag was proximate to the alert override activator.

[0084] So, if any of the above conditions (a) to (e) are not met, then the system will not produce an alert. For example, no alert is generated if only the below conditions are met:

[0085] only (a)+(b)+(c)+(d) - i.e. the alert override was activated when a person bearing an authorisation tag was proximate to the alert override activator; or

[0086] only (a)+(b)+(c)+(e) - i.e. the person about to enter the MRI room is bearing an authorisation tag; or

[0087] only (a)+(b)+(d)+(e) - i.e. there is no person about to enter the MRI room; or

[0088] only (a)+(c)+(d)+(e) - i.e. the door is closed; or

[0089] only (b)+(c)+(d)+(e) - i.e. there is no threat object in the detection zone.

[0090] The same is true when even fewer conditions are met, e.g. if just condition (a) is met and the rest of the conditions are unmet, then an alert will not be generated.

[0091] The concept of having an alert override button on a safety alarm system may seem counterintuitive in the context of this invention. MR Unsafe or unlabelled equipment should always be subject to a full alert if it is detected to be magnetic. However, this invention is intended to also reduce alarms when 'MR Conditional' equipment is entering an MRI room. This is because most MR Conditional equipment contains enough ferromagnetic material to trigger an FMD - so an alarm is inevitable, despite the equipment being safe to enter an MRI room. It may therefore seem prudent to include a means to identify MR Conditional equipment and automatically override the alarm. However, this is not safe because MR Conditional equipment may in some way be holding / transporting other ferromagnetic objects (e.g. other MR Unsafe or unlabelled equipment). So, if the alarm is automatically overridden, the system may inadvertently allow any loose ferromagnetic objects carried in, on, or under the MR Conditional equipment to pass into the MRI room without triggering an alarm. This can and does easily occur e.g., gurneys with a gas bottle cradle underneath it may be carrying an MR Unsafe cylinder. Alternatively, scissors, haemostats, clipboards or other ferrous objects may be on the gurney but covered by bedsheets and so easily missed. It is currently intractable to magnetically distinguish the presence of a haemostat (small but dangerous in an MRI room), under the sheets of a MR Conditional MRI docking table or gurney (which are larger magnetically but safe in an MRI room). Thus, current FMD technology cannot determine whether an MR Conditional piece of equipment is safe or not to enter the MRI room because it cannot be certain if the MR Conditional equipment may be inadvertently transporting other MR Unsafe equipment into the MRI room.

[0092] It is contemplated that in the context of the present invention, when MR Conditional equipment is about to enter an MRI room / area, a responsible person should perform a stop and check (Full-Stop-Final-Check). This is a recommended safety procedure, and should be conducted regardless of whether an FMD is present. Ideally, this procedure should require the responsible person to inspect the equipment and (any accompanying people) for dangerous items prior to entering the MRI room. Beneficially, the present invention allows the alarm to be overridden once the Full-Stop-Final-Check has been performed by the responsible person, and so ensures that this final check is not accidentally forgotten. In practice this may comprise a button (physical or touchscreen) that the responsible person pushes once the procedure is completed and the situation deemed safe. For example, in one embodiment the presence of some equipment may be detected by a camera. This may cause a prompt to appear on a screen requesting a Full-Stop-Final-Check. The override button also appears. If the person most proximate to the button is carrying an authorization tag and they push the button, then the override will be invoked. If the person most proximate to the button is not wearing an authorization tag, if they press the button then the override will not be invoked. It is also contemplated, that a passcode / passkey provided to safety-approved personal could be used (a digital authorisation tagging) to invoke the override. In this specific scenario, the passcode / passkey would operate as (or in place of) the authorization tag or it could be used as a further safety measure. Helpfully, in an embodiment, the display may indicate that this person is not authorized to activate an override. There are many detailed variations on this concept that may be achieved and encompassed by the present invention. It may be considered that the system allows only authorized users to override the alarm, and this should only be actioned after a final inspection of the equipment. Beneficially, as part of an auditing system, the action of the override button may be considered a declaration, on record by the responsible person, that the final inspection has taken place. Beneficially, additional training can be provided if for some reason a responsible person has incorrectly actioned the override.

[0093] In an embodiment, further the end-user alert is configured to raise the alert when

[0094] • the ferromagnetic assessment output indicates the presence of a larger than target sized ferromagnetic object in the ferromagnetic detection zone,

[0095] • the door assessment output indicates the door is not closed, • the person assessment output indicates that the intended path of travel for a person in the person detection zone is through the doorway into the MRI room and

[0096] • the tagging assessment output indicates that the person intending to enter the MRI room is bearing an authorisation tag. Advantageously, as mentioned hereinabove, in some situations a person may be granted an exception to the generation of the alerts. This exception may be temporary or time limited, and the exemption may change the nature of the alert, as was previously described hereinabove. Again, the system may be arranged such that the end-user alert exception does not extend to the situation where very large ferromagnetic objects (e.g. larger than target sized) are about to enter the MRI room. This is because, as discussed hereinabove, large ferromagnetic objects are particularly problematic and dangerous. So, when these larger objects are about to enter the MRI room, the end-user alert exception may be revoked, or a different kind of alert is generated.

[0097] By way of illustrative example, reference is made to the passage hereinabove comparing a safety-trained a radiographer who will know not to carry untethered target sized objects (such as cell phones, haemostats, stethoscopes and small tools) into an MRI room, as compared to non-safety-trained people. This is the purpose of the end-user exemption that may be issued to safety-trained personnel. However, even safety-trained personnel should generally not take in larger-than-target-sized objects (such as steel cylinders, MR Unsafe gurneys etc., that provide significantly larger signals in the FMD than target sized objects) into an MRI room. Again, in this case the full alert should be given despite trained personnel having some form of end-user exemption.

[0098] In this embodiment the system may be configured to also raise an alert when the above conditions are met. So in particular, an alert may be raised even when a person bearing an authorisation tag is about to enter the MRI room, if a larger than target sized ferromagnetic object has been detected. So, for example, in one case the alert will not be generated if the person bearing an authorisation tag (i.e. an authorised person) is wearing an underwired bra (i.e. target sized or smaller object) and is about to enter the MRI room, but in another example the alert will be generated if the authorised person is instead carrying a metal wrench or cylinder (i.e. a larger than target sized ferromagnetic object). Again, this is because large ferromagnetic objects are particularly problematic and dangerous. Advantageously, the system can be configured to preserve the option to raise an alert when the authorised person is potentially doing something a bit more risky than normal, e.g. by bringing into the MRI room a larger than target sized ferromagnetic object. The benefit is to reduce alert fatigue by only raising alerts in respect of authorised persons in the potentially most risky scenarios.

[0099] Again, in such situations, the safety system may need to be calibrated such that target-sized ferromagnetic objects are detectable by the system, and further when larger than target sized ferromagnetic objects are detected by the system. Again, as described hereinabove, this may be a simple matter of walking such objects through the doorway and adjusting the corresponding alert triggering thresholds.

[0100] In an embodiment, further the end-user alert is configured to raise an alternative alert when

[0101] • the ferromagnetic assessment output indicates the presence of a target-sized ferromagnetic object in the ferromagnetic detection zone,

[0102] • the door assessment output indicates the door is not closed, • the person assessment output indicates that the intended path of travel for a person in the person detection zone is through the doorway into the MRI room and • the tagging assessment output indicates that the person intending to enter the MRI room is bearing an authorisation tag.

[0103] As with the embodiment hereinabove, the benefit of this embodiment is to reduce alert fatigue by only raising alerts in respect of authorised persons in the potentially most risky scenarios.

[0104] Advantageously, it may be beneficial to have more than one kind of alert. For example, it may be useful to have an alternative alert raised when a person bearing an authorisation tag is about to take a target sized ferromagnetic object into the MRI room, as compared to a (standard) alert when somebody else is about to do the same (or if the object is a larger than target sized ferromagnetic object, where optionally a further alternative alert could be used). In that way the response by the system and / or any nearby staff / person can be adjusted to suit the situation. Reference is made to the passage hereinabove where examples of alternative alerts are described, e.g. they may be less conspicuous and / or less strident than the (standard) alert etc. Again, beneficially, the alternative alert may produce less overall alert / alarm fatigue with the trained users that must routinely enter the MRI room.

[0105] A passive ferromagnetic detector, commonly abbreviated to FMD, typically works by measuring the ambient (local) magnetic field, and is typically configured to identify temporal variations in this ambient magnetic field. As a general rule, the more ferromagnetic material (e.g. iron) present in / on an object, the greater the magnetic field generated by the object when it is moving. This generated magnetic field interacts and changes the surrounding local (ambient) magnetic field. All things being equal, the bigger the change detected in the local magnetic field, the bigger the ferromagnetic object. The passive ferromagnetic detector in essence works by measuring the change in the local magnetic field caused by the ferromagnetic object. There are various ways that passive ferromagnetic detectors can be set up and these will be known to the skilled person.

[0106] In an embodiment, the passive ferromagnetic detector comprises one or more of fluxgates, magneto-restive, induction, hall effect, optically pumped, SQUIDs; optionally arranged as one or more of single sensors, ID, 2D, or 3D arrays or magnetic gradiometers of first order, second order or third order. Advantageously, it can be useful to monitor if the MRI door is closed, fully open, or any position therebetween (not closed). This is because it can be useful to know if it is possible for a person to enter the MRI room at any given stage (or not). Advantageously, it can be useful to monitor if the door is in a state of motion. This is because the door position, especially when in motion, will affect the local magnetic field and so this can be taken into account when determining if any other (ferromagnetic) objects are also in motion locally.

[0107] There are various ways in which a door register can be configured to monitor if the door is closed, fully open or any position therebetween (not closed), and / or if it is moving.

[0108] In an embodiment, the door register comprises a camera arranged to determine if the door is closed, and optionally if the door is open or moving. The information generated from the camera can be fed into a decision-making component of the door register and the door register can make an assessment. This assessment can be assisted / facilitated by software, computer processor, historical data, computer learning and / or artificial intelligence etc. The decision-making component may comprise one or more processors. The location of any of the cameras in the embodiments of the invention when set up would be determined by various factors, e.g. the location of the MRI room doorway, the shape of the room housing the doorway, any structural features / obstructions (e.g. columns / walls / lighting), other doorways etc. A suitable location may be at a relatively high elevation (near the ceiling), on a wall opposite the doorway to the MRI room, and with a good unobstructed view of the doorway to the MRI room.

[0109] In an embodiment, the door register comprises a RGB (Red, Green and Blue) camera. RGB cameras are conventionally used and can easily be adapted to monitor the MRI door / doorway.

[0110] In an embodiment, the door register comprises an IR / UV camera arranged to determine if the door is closed, and optionally if the door is open or moving, wherein the door is to be equipped to comprise an IR / UV reflector or emitter. One way to monitor the door (it should be understood that monitoring the 'door' may be inclusive of monitoring the doorway that contains the door) is to move away from the visible light spectrum and use IR / UV light. IR / UV cameras can be used to monitor the door if the door can in effect transmit UV / IR light which the camera can pick up. For example, one or more IR / UV reflectors can be placed on the door, e.g. placed along the edge of the door and the relative movement of these reflectors can be tracked by an IR / UV camera. Advantageously, this can simplify the process of monitoring the door as typically there is not much IR / UV light in most indoor environments, and this can free up the visible light channel for use of a RGB camera. In an embodiment the system comprises an IR / UV transmitter, which transmits IR / UV light, and which optionally may be on (or part of) the IR / UV camera.

[0111] In an embodiment, the door register comprises a door contact, or sensor to measure the angular position of the door. Advantageously, this can provide information about the door position in the doorway / frame.

[0112] The invention makes use of a person register. This is arranged to identify people in the person detection zone, and the intended path of travel of each person traveling in the person detection zone. The person register can then determine if the intended path of travel is through the doorway (assuming the door is open and) into the MRI room, and to produce a corresponding person assessment output.

[0113] In an embodiment, the person register comprises a camera, optionally a RGB camera, or a time-of-flight imaging / camera system, to track the path of travel for each person traveling in the person detection zone. RGB cameras are conventionally used and can easily be adapted using software to recognize and monitor people in a person detection zone. Restricting the person register to monitoring a person detection zone can simplify matters where for example some areas in a camera's field of view may not be of interest, e.g. a doorway or corridor leading to an adjacent office and so defining these areas to be outside of the person detection zone can advantageously save on computational power and false alerts.

[0114] In an embodiment, the person register comprises a camera to track the path of travel for each nonhuman object traveling in the person detection zone. It can be useful to know and monitor the position and motion of other objects in the person detection zone. It is useful to know, for example, if a person is pushing or pulling some equipment toward the MRI room. The response of the system can be different between whether a person is on their own or moving equipment. Such equipment may be wheelchairs, gurneys, patient monitors, linen carts, IV poles etc.

[0115] In an embodiment, the person register comprises a camera to track the position, speed and direction of travel for each person traveling in a person detection zone. The information generated from the camera(s) can be fed into a decision-making component of the person register and the person register can make an assessment. This assessment can be assisted / facilitated by software, computer processor, historical data, computer learning and / or artificial intelligence etc. The decision-making component may comprise one or more processors. In an embodiment, a camera tracks the head, neck, torso, spine, hips, shoulders, arms, elbows, hands, legs, knees, ankles and / or feet of each person traveling in the person detection zone; optionally the person register comprises the camera. Understanding the relative position and / or motion of body parts of a person can assist in identifying individuals, the direction they are facing, and their ongoing direction of travel.

[0116] In an embodiment, the person register assigns a temporary ID to each person in the person detection zone; optionally wherein the person register periodically refreshes the ID of each person and / or intended path of travel in the person detection zone. It can be useful to determine how many people are in the person detection zone, their relative positions, and identify who they are, or at least give each an ID. These IDs can help when determining if they are intending to enter the MRI room by moving through the MRI room doorway. For example, a first person may change their motion relative to a second person who is also moving in the detection zone. This change in motion may indicate only a temporary change in the person's overall direction of travel towards (or away from) the MRI doorway. In an embodiment, the end-user alert comprises a visual and / or audible alert; optionally comprising one or more of: visible coloured lights, display screen showing colours, words, icons, pictures and / or symbols, single audible tones, poly-tones, music, spoken word or words. Advantageously, the alert can be selected for best use and may be customised by the user. There may be a balance to strike between the need to warn people of a potential danger, and alert fatigue cause by false alarms, in particular where these alerts are too frequent and / or too strident.

[0117] In an embodiment, the ferromagnetic detection zone is partitioned into two or more policing zones, wherein a first policing zone is arranged to be closest to the doorway and the other policing zones are successively more remote from the doorway.

[0118] The system of the invention may be configured to track a person on a trajectory towards the MRI doorway. As the person gets closer to the doorway, it becomes more likely that the person intends to enter the MRI room, and there is less time to prevent this from happening. As such, it can be advantageous to ramp up the warning level as the person gets closer to the MRI doorway. To do this, the ferromagnetic detection zone (and / or the person detection zone) can be partitioned into one or more policing zones. This might be imagined to be concentric arches radiating out from the MRI room doorway. Of course, other zone arrangements can be selected to suit the space in which the MRI doorway is located. The zone closest to the doorway would represent the most serious risk and the zones furthest from the doorway would represent the least serious risk. In this situation, it would be advantageous if the level of the alert could be proportional / commensurate with the potential risk of that person passing through the MRI doorway into the MRI room.

[0119] So, the alert in a lower risk policing zone may be less conspicuous and / or less strident than an alert generated in a higher risk zone (e.g. directly adjacent to the MRI room doorway; the first policing zone). For example, if the alert was a sound, the initial alert may be a soothing musical tone / note as compared to a strident siren / buzzer in the first policing zone, and / or the pitch of the note may rise as the person approaches the doorway. Similarly, if the alert is a light source the light may brighten as the person approaches the doorway and / or the light may change from green to amber to red to a flashing red light etc.

[0120] In that way, beneficially, the alerts may produce less overall alert fatigue, because the alerts can be relatively lowkey when for example a person is merely passing near to the MRI room, but must cross over a portion of a low risk policing zone.

[0121] In an embodiment, the nature of the end-user alert is changed / adjusted to depend on which policing zone the person who has the intended path of travel through the doorway into the MRI room is located in when the end-user alert is raised.

[0122] In an embodiment, the end-user alert is more conspicuous and / or strident when the person who has the intended path of travel through the doorway into the MRI room is located in a zone that is closer to the doorway when the end-user alert is raised.

[0123] In an embodiment, the end-user alert is most conspicuous and / or strident when the person who has the intended path of travel through the doorway into the MRI room is located in the first policing zone when the end-user alert is raised.

[0124] In an embodiment, the end-user alert can be set / adjusted by the user. This may include a trained medical practitioner and / or maintenance engineer.

[0125] In an embodiment, the passive ferromagnetic detector and the end-user alert are housed together in housings to be located adjacent to the doorway, optionally the housing is an elongate housing, further optionally the elongate housing is a wall mountable pillar.

[0126] It should be noted that the passive ferromagnetic detector is for monitoring a doorway comprising a door leading to an MRI room (which in some situations may have an associated passageway that connects the doorway and the MRI room). In that way ferromagnetic objects can be detected before the object passes through the doorway leading to the MRI room (or can be detected before the object passes through the doorway leading to the passageway that connects to the MRI room). Similarly, the person register also monitors the doorway leading to the MRI room (which again in some situations may have an associated passageway that connects the doorway and the MRI room), so the person register would have means to track people / objects prior to them entering the doorway. It will be appreciated that the door of the doorway is a significant physical barrier which prevents unfettered access to the MRI room, and importantly, is one of the best places to intercept any person who might be taking ferromagnetic objects into the MRI room.

[0127] So, the present system generates an alert before a person bearing a ferromagnetic object passes through the doorway leading to the MRI room (or before the person passes through the doorway leading to the passageway that (directly) connects to the MRI room). Again, this is important because the door of the doorway is a significant physical barrier which prevents unfettered access to the MRI room, and so importantly, is the best place to intercept any person who might be taking inappropriate ferromagnetic objects into the MRI room.

[0128] Once a person passes beyond the doorway (and potentially into a passageway between the doorway and the MRI room), it becomes more difficult to intercept that person, not least because the door may act to prevent any such intervention. If for example these parts of the safety system were located in a passageway leading to an MRI room (e.g. the passive ferromagnetic detector and / or person register were located in this corridor), then undesirable false alarms would become more inevitable. This is because the ability to intercept the person becomes more difficult and so the alert criteria must be more stringently applied to prevent ferromagnetic objects entering the MRI room, consequently and inevitably leading to increased incidences of false alarms.

[0129] Conveniently, the passive ferromagnetic detector is located on either side of the doorway. This is an optimum location to detect ferromagnetic objects that might enter the MRI room. This also allows the detector to contain a series of sensors which together can form ID, 2D, or 3D arrays or magnetic gradiometers of first order, second order or third order.

[0130] In an embodiment, the person register is arranged to be able to be remote from the MRI doorway. In an embodiment, the person register is arranged not to be integrated into, or attached, to the MRI doorway. In an embodiment, the person register is not physically integrated with the passive ferromagnetic detector. In an embodiment, the safety system is a dispersible / dislocated system. In an embodiment, the safety system is a dispersible / dislocated system wherein at least the person register and passive ferromagnetic detector are not (physically) integrated. In an embodiment, the safety system is a dispersible / dislocated system wherein at least the person register and passive ferromagnetic detector are not (physically) integrated in a single housing. In an embodiment, the safety system is a dispersible / dislocated system wherein at least the person register and passive ferromagnetic detector are not physically connected around a doorway. In an embodiment the person register is arranged to be located on a wall opposite or adjacent to the MRI doorway. In an embodiment the person register is arranged to be located on the same wall as the MRI doorway, but arranged to be located remotely from the doorway. In an embodiment the person register comprises a camera arranged to be located on a wall opposite or adjacent to the MRI doorway.

[0131] Advantageously, when the person register is able to be flexibly positioned, i.e. not necessarily just designed to be fixed on the MRI doorway, it can be moved to the best position to monitor the doorway. Indeed, it should be noted that in general the worst place for the person register to be located is on the MRI doorway itself, because it is more difficult to view the approach of a person moving head on, and this is even more problematic when there is a group of people in the space outside the MRI room. This is more so the case when these people are moving around in the space outside the MRI room. Time-of-flight type sensors (in effect a range finder) located on an MRI doorway are especially vulnerable in this regard. When a time-of-flight sensor is attached to an MRI doorway it will in effect record a single distance regardless of who is moving in the space outside an MRI room, i.e. the distance of the closest object to the doorway. In this way, time of flight sensors when located on an MRI doorway can in effect get confused when two or more people are moving around the doorway. This is because each can be moving in different directions, have different speeds and may crossover for a period of time. As an example, if a first person is stationary and near the MRI doorway, they could mask a second person approaching the doorway until the second person passes the first person, at which time it would give little or no time to react to the second person's approach. A false alarm could also be triggered if the first person then moves away from the doorway carrying a triggering object (an object that would give a signal above a threshold limit for a ferromagnetic object moving in the detection space).

[0132] In the context of the invention, a camera by comparison is better and more versatile than time-of-flight sensors. This is because a camera can be arranged to in effect understand the whole scene in the space outside the MRI room. It is better to have a downward looking view where obscuration is minimised. A camera can be arranged to distinguish between different people, their direction of motion, their speed and their likely intended destination. In short, a camera is better than a time-of-flight sensor because it can be used to understand what is really happening in the space outside the MRI room, especially when placed in a location that is sympathetic to obtaining this information, e.g. up high, near the ceiling (for a better vantage point) on a wall opposite the doorway (for a better field of view of the space outside the MRI room), and / or on a wall adjacent to the doorway (perhaps for capturing a side entrance into the space outside the MRI room), and / or is on the same wall as the MRI doorway, but is spaced apart, preferably higher, from the MRI doorway. So, a camera (e.g. RGB camera) observing the detection area in place of a range finder (e.g. time-of-flight sensor) that is forward looking from the periphery of the MRI door, allows for an overall better understanding of the ground truth, is less prone to giving misleading interpretations when overlapping / crossing people are moving in the space outside the MRI room, and so overall a camera can give more time to react to any potential dangers. In an embodiment, the person register does not comprise a range finder or time of flight sensor used to identify the intended path of a person traveling in a person detection zone. In an embodiment, the person register does not comprise a range finder or time of flight sensor. In an embodiment, the person register does not comprise a range finder or time-of-flight sensor used to identify the intended path of a person traveling in a person detection zone. In an embodiment the person register comprises / does not comprise a range finder or time-of-flight sensor arranged to be integrated on the MRI doorway. In an embodiment, the safety system is a dispersible / dislocated system and does not comprise a range finder or time of flight sensor. In an embodiment, the safety system is a dispersible / dislocated system wherein at least the person register does not comprise a range finder or time of flight sensor. Whereas range finder time-of-flight sensors are not very suitable, time-of-flight imaging devices, cameras, are. These are (normally) downward looking cameras that use the time-of-flight principle to form height maps of the scene below. Time-of-flight camera (as opposed to a time-of-flight range finder) could be used as an alternative to, or in addition to, RGB / IR / UV cameras as disclosed herein.

[0133] It should be noted that the safety system of the invention is also not reliant on any detailed knowledge of the motion of the ferromagnetic object moving in the ferromagnetic / person detection zone or otherwise. More detailed knowledge of the motion of the ferromagnetic object moving in the ferromagnetic / person detection zone could in theory be used to further reduce false alarms with the aid of more complex systems / algorithms. However, this solution to false alarm reduction (i.e. determining the motion of the ferromagnetic object) would require more computer processing power and / or is slower, is more complex, and more costly to integrate into a safety system than compared to the solution embodied in the present invention. So, in the context of the present invention this more complex solution is not required, and so in effect represents a different less desirable solution to reducing false alarms.

[0134] In an embodiment, the alert is a beacon located at the top of the pillar-like housing and / or at the bottom of the pillar. This is an optimum location so as to be visible to a person about to enter the MRI room through the doorway. The top lights can be located at about eye height. The location at the bottom of the pillar also allows the floor to be illuminated, so as to cast a light area effect on the floor, that may be arranged to carry the light into the MRI room to warn people within the MRI room of a potential incoming risk. The light on the floor may even be used to project a warning image, word, symbol, icon, shape etc onto the floor. It should be noted that because the MRI room in effect defines a Faraday cage (to prevent electromagnetic fields entering the MRI room), it can be difficult to transmit electronic warnings into the room from outside. Advantageously, an image cast on the floor, can be seen from within the MRI room. Similarly, the top warning lights can be used to project a warning image, word, symbol, icon, shape etc onto the ceiling. This can be useful to warn everyone in the room, especially those who do not have a direct line of sight of the pillars that may be adjacent to the doorway. In an embodiment, the tagging register comprises a camera.

[0135] The information generated from the camera can be fed into a decision-making component of the tagging register and the tagging register can make an assessment. This assessment can be assisted / facilitated by software, computer processor, historical data, computer learning and / or artificial intelligence etc. The decision-making component may comprise one or more processors. In an embodiment, the tagging register comprises an IR / UV camera and the authorisation tag is to comprise an IR / UV reflector or emitter.

[0136] One way to monitor if a person is bearing an authorisation tag is to move away from the visible light spectrum and use IR / UV light. IR / UV cameras can be used to monitor if the person can in effect transmit UV / IR light which the camera can pick up. For example, one or more IR / UV reflectors can be placed on the person, e.g. the person could be wearing or holding an IR / UV reflective surface, patch, sticker, wristband, lanyard, sash, hat or garment, and the presence (or even relative movement of) these reflectors can be noted and tracked by the IR / UV camera and provided to the tagging register. The person bearing the authorisation tag is noted by the tagging register. Advantageously, this can simplify the process of identifying and monitoring the authorisation tag as typically there is not much IR / UV light in most indoor environments, and this can free up the visible light channel for use of a RGB camera. In an embodiment the system comprises an IR / UV transmitter, which transmits IR / UV light, and which optionally may be on (or part of) the IR / UV camera.

[0137] In this way, advantageously, the system can recognise people who have gained certain privileges (e.g. a trained member of staff, technician or supervisor) and so the system may grant those people special alarm exceptions, or those people may be given different (e.g. alternative) alerts, or different levels of the same alert or those people may not be given an alert at all.

[0138] In that way, beneficially, the people bearing the authorisation tags may experience less overall alert fatigue, because the alerts can be comparatively lowkey or even suppressed for those people. This is done to reflect their training and may be commensurate with the level of trust they have attained through training and experience. Such authorisation tags may be temporary, renewable and / or time limited. As a general rule, patients or other visitors would not have these authorisation tags. That said, it is conceived that a tag could be created for special users, such that alternative / special or preferential alerts are generated for them. For example, a blind or deaf person could be given a special tag that generates a haptic alert for them (e.g. an armband with a vibrating buzzer), or preferential alerts are generated for visiting prisoners who may be inclined to acquire dangerous metal objects. The tag could be used to trigger the alerts in a language to best suit the user. The tag could be used to trigger an alert message that uses the person's name.

[0139] In an embodiment, the tagging register comprises a RGB camera and the authorisation tag is to comprise coded information readable by the tagging register, optionally the coded information is to comprise a QR or barcode or an ArUco marker.

[0140] RGB cameras are conventionally used and can easily be adapted to monitor coded information (including visible biometric information). Optionally, the information may be located in a convenient place, such as on a person's arm, shoulder or back, where the RGB camera would be able to collect the coded information. The camera may provide the information (e.g. Q.R code or biometric information) to a decision-making component of the tagging register and the assessment of the code (or biometric information) can be assisted / facilitated by software, computer processor, stored data, computer learning and / or artificial intelligence etc. The decision-making component may comprise one or more processors.

[0141] In an embodiment, the tagging register comprises a RGB camera and the authorisation tag is to comprise the persons face, or other visible biometric information. RGB cameras are conventionally used and can easily be adapted to monitor biometric information that would be visible to the camera. The ability to gather more information than simply the presence / absence of a tag associated with a person or piece of equipment is useful. The system may be programmed to give different responses according to the type of tag or the specific identification of a person or piece of equipment. For example, the system may classify people as radiographers, radiologists, doctors, nurses, cleaners etc. and present different behaviours for each.

[0142] In an embodiment, the tagging register and the door register share a RGB camera, and / or the IR / UV camera of the tagging register and door register share an IR / UV camera.

[0143] Advantageously, in an embodiment the system may use one camera, or more than one camera, these cameras may provide / feed information to one or more decision-making component of the more than one of the registers of the system.

[0144] There are situations where a large ferromagnetic object must be permitted into the MRI room (e.g. an MRI approved gurney) and in these situations a responsible / qualified person can be permitted to actively allow that object into the MRI room, so long as they have checked that all ferromagnetic objects that might be dangerous are suitably tethered / restrained before entering the MRI room. It is also contemplated that within the scope of the tagging register there are other means to do this which include but are not limited to electronic tagging, acoustic tagging which have the aim of providing the physical location associated with a person in the detection zone.

[0145] In an embodiment, the system determines if the alert override was activated by a person bearing a suitable authorisation tag.

[0146] In an embodiment, the override register comprises a camera.

[0147] The information generated from the camera can be fed into a decision-making component of the override register and the override register can make an assessment, e.g. to determine if a person bearing an authorisation tag was proximate to an alert override activator when the alert override was activated. This assessment can be assisted / facilitated by software, computer processor, historical data, computer learning and / or artificial intelligence etc. The decision-making component may comprise one or more processors. In this way, the intent of the system is to determine if a person with an authorisation tag triggered the override (as opposed to someone else). So, if the override was triggered and a person with an authorisation tag was not close enough to have done this, then the override would not be deemed to be valid.

[0148] That is, in an embodiment, an alert that otherwise would be generated by the system can be overridden by an authorised person who uses an alert override activator.

[0149] In this way, advantageously, the system can recognise people who have gained certain privileges (e.g. a trained member of staff, technician or supervisor) and so the system may grant those people special alarm exceptions or exemptions, or those people may be given different alerts, or different levels of the same alert or those people may not be given an alert at all.

[0150] In that way, beneficially, the people bearing the authorisation tags in these situations may experience less overall alert fatigue, because the alerts can be optionally suppressed for those people. This is done to reflect their training and may be commensurate with the level of trust they have attained through training and experience. Such authorisation tags may be temporary, renewable and / or time limited. In an embodiment, the override activator comprises an override switch actionable by a person proximate to the override switch, optionally wherein the override switch comprises one or more of a physical button, touch button(s) on a touch screen, a device adapted to receive a passcode, a device adapted to receive biometric information (e.g. fingerprint reader, device for face / voice recognition etc.) an RFID proximity reader, a microphone to receive a voice command, or camera to receive a gesture.

[0151] In an embodiment, the override activator requires the user to confirm that all safety checks have been conducted by the user and that it is safe to enter the MRI room through the doorway.

[0152] In an embodiment, the override register is capable of overriding the alert for a period of time, optionally for 5, 10, 15, 30, 45, 60, 120, 180, 240 or 300 seconds.

[0153] In an embodiment, the override register comprises an IR / UV camera and the authorisation tag is to comprise an IR / UV reflector or emitter, optionally a wearable IR / UV reflective patch, sticker, wristband, lanyard, sash, hat or garment.

[0154] As mentioned hereinabove, one way to monitor if a person is bearing an authorisation tag is to move away from the visible light spectrum and use IR / UV light, e.g. IR / UV cameras can be used to monitor if the person can in effect transmit UV / IR light which the camera can pick up. For example, one or more IR / UV reflectors can be placed on the person, e.g. the person could be wearing or holding an IR / UV reflective surface, patch, sticker, wristband, lanyard, sash, hat or garment, and the presence (or even relative movement of) these reflectors can be noted and tracked by the IR / UV camera and provided to the decision-making component of tagging register. The person bearing the authorisation tag is noted by the tagging register. Advantageously, this can simplify the process of identifying and monitoring the authorisation tag as typically there is not much IR / UV light in most indoor environments, and this can free up the visible light channel for use of a RGB camera. In an embodiment the system comprises an IR / UV transmitter, which transmits IR / UV light, and which optionally may be on (or part of) the IR / UV camera.

[0155] In an embodiment, the override register comprises a RGB camera and the authorisation tag is to comprise coded information readable by the tagging register, optionally the coded information is a QR or barcode.

[0156] As mentioned hereinabove, RGB cameras are conventionally used and can easily be adapted to monitor coded information (including visible biometric information). Again, optionally, the information may be located in a convenient place, such as on a person's arm, shoulder or back, where the RGB camera would be able to collect the coded information. Again, the camera could provide the information (e.g. QR code or biometric information) to the decision-making component of tagging register and the assessment of the code (or biometric information) can be assisted / facilitated by software, computer processor, stored data, computer learning and / or artificial intelligence etc. In an embodiment, the override register comprises a RGB camera and the authorisation tag is to comprise the persons face or other visible biometric information. RGB cameras are conventionally used and can easily be adapted to monitor biometric information that would be visible to the camera. In an embodiment, the RGB camera of the tagging register and the override register share the same RGB camera, and / or the IR / UV camera of the tagging register and override register share the same IR / UV camera. Advantageously, in an embodiment the system may use one camera, or more than one camera, these cameras may provide / feed information to more than one of the registers of the system. In an embodiment, the override register and the door register share a RGB camera, and / or the IR / UV camera of the override register and door register share a same IR / UV camera. Advantageously, in an embodiment the system may use one camera, or more than one camera, these cameras may provide / feed information to more than one of the registers of the system.

[0157] In an embodiment, the door register, tagging register and override register share a RGB camera, and / or the IR / UV camera of the door register, tagging register and override register share an IR / UV camera. Advantageously, in an embodiment the system may use one camera, or more than one camera, these cameras may provide / feed information to more than one of the registers of the system.

[0158] In an embodiment, the passive ferromagnetic detector, door register, person register, tagging register, and / or the alert override register comprise one or more processors to provide their respective assessment outputs. Advantageously, in an embodiment the system may use one processor, or more than one processor, where the various registers may provide / feed information to more than one of these processors of the system.

[0159] In an embodiment, the safety system comprises a non-magnetic sensor to determine the presence of a piece of equipment in the ferromagnetic detection zone, and wherein when this happens, this causes the override register to display the override switch actionable by a person proximate to the override switch; optionally the non-magnetic sensor is a RGB camera ; further optionally the RGB camera is a RGB camera forming part of the door register, person register and / or tagging register.

[0160] In a further aspect of the invention there is provided a safety system for policing a doorway comprising a door to an MRI room, the safety system comprising:

[0161] (i) a passive ferromagnetic detector arranged to measure an ambient magnetic field within a ferromagnetic detection zone, and configured to identify temporal variations in the ambient magnetic field which indicate the presence of a target-sized or larger ferromagnetic object in the ferromagnetic detection zone, and to produce a corresponding ferromagnetic assessment output;

[0162] (ii) a person register arranged to determine if a person is about to enter,

[0163] or is entering the MRI room, and to produce a corresponding person assessment output;

[0164] (iii) an end-user alert arranged to receive the ferromagnetic assessment output, and the person assessment output; and wherein in use, the end-user alert is configured to raise an alert wherein the alert comprises a floor illumination source arrange to illuminate at least a portion of the floor of the MRI room when

[0165] • the ferromagnetic assessment output indicates the presence of a target-sized or larger ferromagnetic object in the ferromagnetic detection zone, and

[0166] • the person assessment output indicates that a person is about to enter, or is entering the MRI room.

[0167] In an embodiment, the floor illumination source floods the doorway threshold to the MRI room with light. In an embodiment, the passive ferromagnetic detector and the floor illumination source are housed together in housings to be located adjacent to the doorway to the MRI room, optionally the housing is an elongate housing, further optionally the elongate housing is a wall mountable pillar. Optionally, or additionally, a portion of the ceiling, wall or walls of the MRI room may be illuminated in this way.

[0168] In an embodiment, the system of the invention is provided as a kit of parts.

[0169] Herein disclosed, the disclosure made herein may find utility in any location with a strong magnetic field, such as a location comprising an NMR room. Herein disclosed, the disclosure made herein may further surprisingly find utility in non-MRI applications, such as in security applications (e.g. for detection of weapons in private / public areas, or for the detection of contraband items such as improvised knives like 'prison shanks', or for the detection of the removal of information stored on portable data storage devices (e.g. pen drives) from a controlled / secure location). In this context, there may not be a (MRI) door and hence there may not be a need for a door register. It should of course be recognised that applying the technology disclosed herein to other / security applications moderates the specialist restrictions incumbent with this unique technical field, e.g. those associated with the powerful magnetic fields generated by the powerful magnets used in MRI scanning, and those associated with the resultant Faraday-type cages (inclusive of the MRI door) that must confine the MRI scanners in the MRI rooms.

[0170] Embodiments of the invention relate to ways in which the invention may be implemented, and may be combine / substituted with other embodiments of the invention. Herein disclosed, any aspect of the invention, and embodiment(s) of any one aspect of the invention, may be used, adapted, combined or employed in / with any aspect or embodiment(s) of the invention, or in / with any other disclosure made herein.

[0171] Brief description of the drawinqs

[0172] Figure 1A to Figure 1C show schematic representations of embodiments of the invention.

[0173] Figures 2A to Figure 2C show alternative schematic representations of embodiments of the invention.

[0174] Figure 3 shows a schematic representation of an embodiment of a processor useful in an embodiment of the invention. Figure 4 shows a schematic representation of the respective location of one or more cameras with respect to a doorway leading to an MRI room useful in an embodiment of the invention.

[0175] Figure 5 shows a schematic representation of the policing zones useful in an embodiment of the invention.

[0176] Like, corresponding, equivalent or substantially equivalent features have been given like reference numerals.

[0177] Detailed description of the invention

[0178] Figure 1A shows a schematic representation of an embodiment of the safety system (100) for policing a doorway comprising a door to an MRI room (not shown).

[0179] The system (100) comprises:

[0180] a passive ferromagnetic detector (10) which is arranged to measure an ambient magnetic field within a ferromagnetic detection zone (not shown), and configured to identify temporal variations in the ambient magnetic field which indicate the presence of a target-sized or larger ferromagnetic object in the ferromagnetic detection zone, and to produce a corresponding ferromagnetic assessment output (11);

[0181] a door register (20) which is arranged to identify if the door (not shown) is closed, and to produce a corresponding door assessment output (21);

[0182] a person register (30) which is arranged to identify the intended path of travel for each person traveling in a person detection zone (not shown) and to determine if the intended path of travel is through the doorway into the MRI room, and to produce a corresponding person assessment output (31); an end-user alert (80) which is arranged to receive the respective assessment outputs mentioned herein above (e.g. 11, 21, and 31) and wherein in use, the end-user alert (80) is configured to raise an alert (90) when:

[0183] the ferromagnetic assessment output (11) indicates the presence of a target-sized or larger ferromagnetic object in the ferromagnetic detection zone,

[0184] the door assessment output (21) indicates the door is not closed,

[0185] the person assessment output (31) indicates that the intended path of travel fora person in the person detection zone is through the doorway into the MRI room.

[0186] Figure IB shows schematic representation of an embodiment of the safety system (200) for policing a doorway comprising a door to an MRI room (not shown).

[0187] The system (200) comprises:

[0188] a passive ferromagnetic detector (10) which is arranged to measure an ambient magnetic field within a ferromagnetic detection zone (not shown), and configured to identify temporal variations in the ambient magnetic field which indicate the presence of a target-sized or larger ferromagnetic object in the ferromagnetic detection zone, and to produce a corresponding ferromagnetic assessment output (11);

[0189] a door register (20) which is arranged to identify if the door (not shown) is closed, and to produce a corresponding door assessment output (21);

[0190] a person register (30) which is arranged to identify the intended path of travel for each person traveling in a person detection zone (not shown) and to determine if the intended path of travel is through the doorway into the MRI room, and to produce a corresponding person assessment output (31);

[0191] a tagging register (40) which is arranged to identify if any person in the person detection zone is bearing an authorisation tag (not shown), and to produce a corresponding tagging assessment output (41); an end-user alert (80) which is arranged to receive the respective assessment outputs mentioned herein above (e.g. 11, 21, 31, and 41) and wherein in use, the end-user alert (80) is configured to raise an alert (90) when:

[0192] the ferromagnetic assessment output (11) indicates the presence of a target-sized or larger ferromagnetic object in the ferromagnetic detection zone,

[0193] the door assessment output (21) indicates the door is not closed,

[0194] the person assessment output (31) indicates that the intended path of travel fora person in the person detection zone is through the doorway into the MRI room,

[0195] the tagging assessment output (41) indicates that the person intending to enter the MRI room is not bearing an authorisation tag.

[0196] Figure 1C shows a schematic representation of an embodiment of the safety system (300) for policing a doorway comprising a door to an MRI room (not shown).

[0197] The system (300) comprises:

[0198] a passive ferromagnetic detector (10) which is arranged to measure an ambient magnetic field within a ferromagnetic detection zone (not shown), and configured to identify temporal variations in the ambient magnetic field which indicate the presence of a target-sized or larger ferromagnetic object in the ferromagnetic detection zone, and to produce a corresponding ferromagnetic assessment output (11);

[0199] a door register (20) which is arranged to identify if the door (not shown) is closed, and to produce a corresponding door assessment output (21);

[0200] a person register (30) which is arranged to identify the intended path of travel for each person traveling in a person detection zone (not shown) and to determine if the intended path of travel is through the doorway into the MRI room, and to produce a corresponding person assessment output (31);

[0201] a tagging register (40) which is arranged to identify if any person in the person detection zone is bearing an authorisation tag (not shown), and to produce a corresponding tagging assessment output (41); an alert override register (50) which is arranged to identify if an alert override has been activated when any person bearing an authorisation tag is proximate to an alert override activator (not shown), and to produce a corresponding override assessment output (51); and

[0202] an end-user alert (80) which is arranged to receive the respective assessment outputs mentioned herein above (e.g. 11, 21, 31, 41 and 51) and wherein in use, the end-user alert (80) is configured to raise an alert (90) when:

[0203] the ferromagnetic assessment output (11) indicates the presence of a target-sized or larger ferromagnetic object in the ferromagnetic detection zone,

[0204] the door assessment output (21) indicates the door is not closed,

[0205] the person assessment output (31) indicates that the intended path of travel fora person in the person detection zone is through the doorway into the MRI room,

[0206] the tagging assessment output (41) indicates that the person intending to enter the MRI room is not bearing an authorisation tag and

[0207] override assessment output (51) indicates that the alert override was not activated when a person bearing an authorisation tag was proximate to the alert override activator.

[0208] Figure 2A shows an alternative schematic representation of an embodiment of the invention (101) where two of the registers are combined. For example, these may be a single camera feeding information to a single processor which produces an output assessment in respect of each register.

[0209] Figure 2B shows an alternative schematic representation of an embodiment of the invention (201) where two of the registers are combined. For example, these may be a single camera feeding information to a single processor which produces an output assessment in respect of each register.

[0210] Figure 2C shows an alternative schematic representation of an embodiment of the invention (301) where two of the registers are combined. For example, these may be a single camera feeding information to a single processor which produces an output assessment in respect of each register.

[0211] Figure 3 shows a schematic representation of an embodiment of a processor useful in an embodiment of the invention. The embodiment shows a single processor receiving information from magnetic sensors (10) and receiving information from video camera(s) from the camera which forms part of the door register (20). In each case a processor processes the information and produces a respective ferromagnetic assessment output (11) and door assessment output (21) to the end-user alert (80), which in turn considers these outputs in light of any other salient register outputs (e.g. the person assessment output (31); not shown) and raises an alert if all the criteria for raising an alert are satisfied.

[0212] Figure 4 shows a schematic representation of the location of a camera (32) with respect to the doorway (900) leading to the MRI room (902) useful in an embodiment of the invention. The figure shows that the camera (32) forming part of the person register (30) is located on the ceiling with a good unobstructed view of the door (901) in the doorway (900) leading to the MRI room (903).

[0213] Figure 5 shows a schematic top-down view representation of the policing zones useful in an embodiment of the invention. The figure shows a person (indicated by shoe icons) walking towards the open doorway (900) into an MRI room (902). The camera (32) forming part of the door register (20; not shown) and forming part of the person register (30; not shown) notes that the door (901) is open and that the person is intent on entering the MRI room through the doorway (900) which is flanked on either side by two pillar-like housings (12) forming part of the passive ferromagnetic detector (10). The system has been configured to identify three policing zones, an outermost policing zone (803), and intermediate policing zone (802) and a first policing zone ((801), i.e. nearest the doorway). In this schematic representation, the system determines that the person has the intent to enter the MRI room through the doorway (the system generates an intent flag (1)). Next the system determines that the person has continued to approach the doorway, and now is in the intermediate policing zone (the system now generates an early warning flag (2)). Finally, the system determines that the person has entered the first policing zone and is still intent on entering the MRI room through the open doorway (the system has generated a final warning flag (3)). In the situation where the person has been determined to be carrying a threat sized ferromagnetic object using the passive ferromagnetic detector (10), then a series of progressively more strident alerts will be raised by the system as the person approaches the doorway. Of course, if the person has been authorised to enter the MRI room in some way (e.g. the system recognizes that the person possesses an alert exception or exemption or authorization tag), then the alerts will not be generated, or an alternative overall less strident alert may be generated.

Claims

Claims1. A safety system for policing a doorway comprising a door to an MRI room, the safety system comprising:(i) a passive ferromagnetic detector arranged to measure an ambient magnetic field within a ferromagnetic detection zone, and configured to identify temporal variations in the ambient magnetic field which indicate the presence of a target-sized or larger ferromagnetic object in the ferromagnetic detection zone, and to produce a corresponding ferromagnetic assessment output;(ii) a door register arranged to identify if the door is closed, and to produce a corresponding door assessment output;(iii) a person register arranged to identify the intended path of travel for each person traveling in a person detection zone and to determine if the intended path of travel is through the doorway into the MRI room, and to produce a corresponding person assessment output;(iv) an end-user alert arranged to receive the ferromagnetic assessment output, the door assessment output and the person assessment output;and wherein in use, the end-user alert is configured to raise an alert when• the ferromagnetic assessment output indicates the presence of a target-sized or larger ferromagnetic object in the ferromagnetic detection zone,• the door assessment output indicates the door is not closed, and• the person assessment output indicates that the intended path of travel for a person in the person detection zone is through the doorway into the MRI room.

2. The safety system of claim 1, wherein further, the end-user alert is configured to raise the alert when• the ferromagnetic assessment output indicates the presence of a larger than target sized ferromagnetic object in the ferromagnetic detection zone,• the door assessment output indicates the door is not closed, • the person assessment output indicates that the intended path of travel for a person in the person detection zone is through the doorway into the MRI room,• the person intending to enter the MRI room has been provided withan end-user alert exemption, optionally the person is an MRI approved operator and / or an MRI approved qualified hospital worker.

3. The safety system of claim 1 or 2, wherein further, the end-user alert is configured to raise an alternative alert when• the ferromagnetic assessment output indicates the presence of a target-sized ferromagnetic object in the ferromagnetic detection zone,• the door assessment output indicates the door is not closed, • the person assessment output indicates that the intended path of travel for a person in the person detection zone is through the doorway into the MRI room and• the person intending to enter the MRI room has been provided withan end-user alert exemption, optionally the person is an MRI approved operator and / or an MRI approved qualified hospital worker.

4. A safety system for policing a doorway comprising a door to an MRI room, the safety system comprising:(i) a passive ferromagnetic detector arranged to measure an ambient magnetic field within a ferromagnetic detection zone, and configured to identify temporal variations in the ambient magnetic field which indicate the presence of a target-sized or larger ferromagnetic object in the ferromagnetic detection zone, and to produce a corresponding ferromagnetic assessment output;(ii) a door register arranged to identify if the door is closed, and to produce a corresponding door assessment output;(iii) a person register arranged to identify the intended path of travel for each person traveling in a person detection zone and to determine if the intended path of travel is through the doorway into the MRI room, and to produce a corresponding person assessment output;(iv) a tagging register arranged to identify if any person in the person detection zone is bearing an authorisation tag, and to produce a corresponding tagging assessment output;(v) an end-user alert arranged to receive the ferromagnetic assessment output, the door assessment output, the person assessment output and the tagging assessment output;and wherein in use, the end-user alert is configured to raise an alert whenthe ferromagnetic assessment output indicates the presence of a target-sized or larger ferromagnetic object in the ferromagnetic detection zone,• the door assessment output indicates the door is not closed, • the person assessment output indicates that the intended path of travel for a person in the person detection zone is through the doorway into the MRI room and• the tagging assessment output indicates that the person intending to enter the MRI room is not bearing an authorisation tag.

5. A safety system for policing a doorway comprising a door to an MRI room, the safety system comprising:(i) a passive ferromagnetic detector arranged to measure an ambient magnetic field within a ferromagnetic detection zone, and configured to identify temporal variations in the ambient magnetic field which indicate the presence of a target-sized or larger ferromagnetic object in the ferromagnetic detection zone, and to produce a corresponding ferromagnetic assessment output;(ii) a door register arranged to identify if the door is closed, and to produce a corresponding door assessment output;(iii) a person register arranged to identify the intended path of travel for each person traveling in a person detection zone and to determine if the intended path of travel is through the doorway into the MRI room, and to produce a corresponding person assessment output;(iv) a tagging register arranged to identify if any person in the person detection zone is bearing an authorisation tag, and to produce a corresponding tagging assessment output;(v) an alert override register arranged to identify if an alert override has been activated when any person bearing an authorisation tag is proximate to an alert override activator, and to produce a corresponding override assessment output;(vi) an end-user alert arranged to receive the ferromagnetic assessment output, the door assessment output, the person assessment output, the tagging assessment output, and the override assessment output; and wherein in use, the end-user alert is configured to raise an alert when• the ferromagnetic assessment output indicates the presence of a target-sized or larger ferromagnetic object in the ferromagnetic detection zone,the door assessment output indicates the door is not closed, • the person assessment output indicates that the intended path of travel for a person in the person detection zone is through the doorway into the MRI room,• the tagging assessment output indicates that the person intending to enter the MRI room is not bearing an authorisation tag and• the alert override was not activated when a person bearing an authorisation tag was proximate to the alert override activator.

6. The safety system of claim 4 or 5, wherein further, the end-user alert is configured to raise the alert when• the ferromagnetic assessment output indicates the presence of a larger than target sized ferromagnetic object in the ferromagnetic detection zone,• the door assessment output indicates the door is not closed, • the person assessment output indicates that the intended path of travel for a person in the person detection zone is through the doorway into the MRI room and• the tagging assessment output indicates that the person intending to enter the MRI room is bearing an authorisation tag.

7. The safety system of any one of claims 4 to 6, wherein further, the end-user alert is configured to raise an alternative alert when• the ferromagnetic assessment output indicates the presence of a target-sized ferromagnetic object in the ferromagnetic detection zone,• the door assessment output indicates the door is not closed, • the person assessment output indicates that the intended path of travel for a person in the person detection zone is through the doorway into the MRI room and• the tagging assessment output indicates that the person intending to enter the MRI room is bearing an authorisation tag.

8. The safety system of any one of the preceding claims wherein the passive ferromagnetic detector comprises one or more of fluxgates, magneto-restive, induction, hall effect, optically pumped, SQUIDs; optionally arranged as one or more of single sensors, ID, 2D, or 3D arrays or magnetic gradiometers of first order, second order or third order.

9. The safety system of any one of the preceding claims wherein the door register comprises a camera arranged to determine if the door is closed, and optionally if the door is open or moving.

10. The safety system of any one of the preceding claims wherein the door register comprises a RGB camera.

11. The safety system of any one of the preceding claims wherein the door register comprises an IR / UV camera arranged to determine if the door is closed, and optionally if the door is open or moving, wherein the door is to be equipped to comprise an IR / UV reflector or emitter.

12. The safety system of any one of the preceding claims wherein the door register comprises a door contact, or sensor to measure the angular position of the door.

13. The safety system of any one of the preceding claims wherein the person register comprises a camera, optionally a RGB camera, or a time-of-flight imaging / camera system, to track the path of travel for each person traveling in the person detection zone.

14. The safety system of any one of the preceding claims wherein the person register comprises a camera to additionally track the path of travel for each non-human object traveling in the person detection zone.

15. The safety system of any one of the preceding claims wherein the person register comprises a camera to track the position, speed and direction of travel for each person traveling in a person detection zone.

16. The safety system of any one of the preceding claims wherein a camera tracks the head, neck, torso, spine, hips, shoulders, arms, elbows, hands, legs, knees, ankles and / or feet of each person traveling in the person detection zone; optionally the person register comprises the camera.

17. The safety system of any one of the preceding claims wherein the person register assigns a temporary ID to each person in the person detection zone; optionally wherein the person register periodically refreshes the ID of each person and / or intended path of travel in the person detection zone.

18. The safety system of any one of the preceding claims wherein the end-user alert comprises a visual and / or audible alert; optionally comprising one or more of: visible coloured lights, display screen showing colours, words, icons, pictures and / or symbols, single audible tones, poly-tones, music, spoken word or words.

19. The safety system of any one of the preceding claims wherein the ferromagnetic detection zone is partitioned into two or more policing zones, wherein a first policing zone is arranged to be closest to the doorway and the other policing zones are successively more remote from the doorway.

20. The safety system of any one of the preceding claims wherein the nature of the end-user alert is changed / adjusted to depend on which policing zone the person who has the intended path of travel through the doorway into the MRI room is located when the end-user alert is raised.

21. The safety system of claim 19 or 20 wherein the end-user alert is more conspicuous and / or strident when the person who has the intended path of travel through the doorway into the MRI room is located in a policing zone that is closer to the doorway when the end-user alert is raised.

22. The safety system of any one of claims 19 to 21 wherein the end-user alert is most conspicuous and / or strident when the person who has the intended path of travel through the doorway into the MRI room is located in the first policing zone when the end-user alert is raised.

23. The safety system of any one of the preceding claims wherein the end-user alert can be set / adjusted by the user.

24. The safety system of any one of the preceding claims wherein the passive ferromagnetic detector and the end-user alert are housed together in housings to be located adjacent to the doorway, optionally the housing is an elongate housing, further optionally the elongate housing is a wall mountable pillar.

25. The safety system of claim 24, wherein the alert is a beacon located at the top of the pillar and / or at the bottom of the pillar.

26. The safety system of claim 24 or 25, wherein a beacon located at the bottom of the pillar and is arranged to project light onto the floor and into the MRI room, optionally the light floods the floor around the MRI doorway threshold and at least part of the floor of the MRI room.

27. The safety system of any one of the preceding claims wherein the tagging register comprises a camera.

28. The safety system of any one of the preceding claims wherein the tagging register comprises an IR / UV camera and the authorisation tag is to comprise an IR / UV reflector or emitter.

29. The safety system of any one of the preceding claims wherein the tagging register comprises a RGB camera and the authorisation tag is to comprise coded information readable by the tagging register, optionally the coded information is to comprise a QR or barcode, further optionally, the tagging register comprises a RGB camera and the authorisation tag is to comprise the persons face, or other visible biometric information.

30. The safety system of any one of the preceding claims wherein the tagging register and the door register share a RGB camera, and / or the IR / UV camera of the tagging register and door register share an IR / UV camera.

31. The safety system of any one of the preceding claims wherein the override register comprises a camera.

32. The safety system of any one of the preceding claims wherein the override activator comprises an override switch actionable by a person proximate to the override switch, optionally wherein the override switch comprises one or more of a physical button, touch button(s) on a touch screen, a device adapted to receive a passcode, a device adapted to receive biometric information, an RFID proximity reader, a microphone to receive a voice command, or camera to receive a gesture.

33. The safety system of any one of the preceding claims wherein the override register comprises an IR / UV camera and the authorisation tag is to comprise an IR / UV reflector or emitter, optionally a wearable IR / UV reflective patch, sticker, wristband, lanyard, sash, hat or garment.

34. The safety system of any one of the preceding claims wherein the override register comprises a RGB camera and the authorisation tag is to comprise coded information readable by the tagging register, optionally the coded information is a QR or barcode.

35. The safety system of any one of claims 32 to 34 wherein a non-magnetic sensor determines the presence of a piece of equipment in the ferromagnetic detection zone, and wherein when this happens, this causes the override register to display the override switch actionable by a person proximate to the override switch; optionally the non-magnetic sensor is a RGB camera ; further optionally the RGB camera is a RGB camera forming part of the door register, person register and / or tagging register.

36. A safety system for policing a doorway comprising a door to an MRI room, the safety system comprising:(i) a passive ferromagnetic detector arranged to measure an ambient magnetic field within a ferromagnetic detection zone, and configured to identify temporal variations in the ambient magnetic field which indicate the presence of a target-sized or larger ferromagnetic object in the ferromagnetic detection zone, and to produce a corresponding ferromagnetic assessment output;(ii) a person register arranged to determine if a person is about to enter,or is entering the MRI room, and to produce a corresponding person assessment output;(iii) an end-user alert arranged to receive the ferromagnetic assessment output, and the person assessment output;and wherein in use, the end-user alert is configured to raise an alert wherein the alert comprises a floor illumination source arrange to illuminate at least a portion of the floor of the MRI room when• the ferromagnetic assessment output indicates the presence of a target-sized or larger ferromagnetic object in the ferromagnetic detection zone, and• the person assessment output indicates that a person is about to enter, or is entering the MRI room.

37. A safety system of claim 36 where the floor illumination source floods the doorway threshold to the MRI room with light.

38. A safety system of claim 36 or 37 wherein the passive ferromagnetic detector and the floor illumination source are housed together in housings to be located adjacent to the doorway tothe MRI room, optionally the housing is an elongate housing, further optionally the elongate housing is a wall mountable pillar.

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