Ionizing particle detection device

Abstract

The invention relates to an intraoperative probe for guiding an excision tool, comprising a detection head, said detection head comprising a plurality of optical fibers each coupled to a photodetector characterized in that said optical fibers are transparent and scintillator-free, the proximal end of each of said transparent fibers is optically coupled with a single continuous scintillator optically coupled to a light guide, capable of capturing beta and / or gamma particles and emitting light in response to this interaction, the distal end of each of said transparent fibers is coupled to a photodetector, and in that said intraoperative probe is associated with a signal processing system, configured to analyze the signals delivered by said photodetectors.comprising: a means for temporal coincidence analysis of said signals delivered by said photodetectors to discriminate real events from thermal noise; a processing means enabling the reconstruction of the interaction position of particles in said continuous scintillator from the distribution of light transmitted by said optical fibers. Figure of the abstract: 1,

Description

Title of the invention: Ionizing particle detection device Scope of the invention

[0001] The present invention relates to the field of ionizing particle detectors, and more particularly to the field of detection systems using scintillators to capture beta and gamma particles. Devices of this type are used in various sectors, including nuclear medicine, particle physics, radiation protection, and industrial radiation monitoring applications.

[0002] The invention relates in particular to the application of such detectors for the creation of a probe capable of guiding surgeons during the surgical treatment of solid tumors. The TRIOP probe (acronym for 'Tumor Resection Intraoperative Probe') integrates the coupling between a detection head and a surgical tool, such as a modular aspirator, an ultrasonic aspirator, or any other excision device, to improve the accuracy of tumor resection by providing real-time feedback on the tumor margins.

[0003] The probe is designed to be placed close to the tumor during surgery. It detects all types of cancerous tissue in real time based on specific imaging or detection techniques (e.g., fluorescence or ionizing particle detection). This allows for the identification of the exact tumor boundaries. The associated excision devices are used to precisely cut and aspirate the tumor tissue. When coupled with the probe, they allow the surgeon to remove only the cancerous tissue, following the probe's indications.

[0004] The coupling allows the surgeon to be guided with high precision, improving the quality of the surgical procedure and reducing the risk of leaving tumor remnants. By rapidly identifying cancerous tissue, the probe accelerates the surgical process, allowing the surgeon to progress more efficiently through the intervention. The ability to define the margins of tumor resection in real time minimizes the risk of damage to surrounding healthy tissue. State of the art

[0005] In the field of ionizing particle detection, devices using scintillators coupled with optical collection systems, such as optical fibers and silicon photomultiplier tubes (SiPMs), are well established. These systems exploit the ability of scintillators to emit light when they interact with ionizing particles, such as beta particles and gamma rays. The light The emitted light is then captured by optical fibers and guided to photodetectors which transform this light into electrical signals, which are then processed to identify and analyze interaction events.

[0006] Prior art patent US9775573 is known for a probe comprising a detection head, an optical fiber for receiving and guiding a signal emitted by radioactive tracers and fluorescent molecules in a tissue area, a photodetector for converting the emitted signal into an electrical signal, a transmitter for transmitting the information carried by the electrical signal to analytical equipment, and a fastening element for attaching the probe to the manual excision tool. The detection head is formed by a bundle of radioactive tracer detection fibers comprising a scintillating terminal portion and a transparent main portion, the scintillating terminal portion being fused to the transparent main portion, for example by heating.The scintillating terminal is adapted to interact with radioactive [3] particles ([3+] or [3-] particles) emitted by tissue previously labeled with radioactive tracers and to convert them into a light signal. The main part is adapted to guide the light signal emitted by the terminal. The scintillating part is typically about 1 mm long and the transparent part is typically about 10 cm long. Both the scintillating and transparent parts have a diameter of approximately 1.5 mm.

[0007] Patent EP1933747Bl proposes an intraoperative probe for guiding an excision tool, comprising a detection head, said detection head comprising:

[0008] - at least one optical fiber capable of receiving and guiding a signal emitted by tracers radioactive particles in a tissue area, to an analysis device, means for attaching the head to the excision tool so that the excision tool is capable of extracting a portion of tissue in the signal-emitting tissue area, characterized in that the optical fiber comprises a scintillating portion capable of interacting with radioactive particles emitted by the tissue to generate a light signal

[0009] US patent 5014708 describes another example of a surgical tool, comprising a detection head for detecting radioactive rays and providing signals by which to direct an operator to guide said therapeutic means to labeled cancerous tissues. The radioactive rays emitted by the cancerous tissues enter a scintillator which generates fluorescence directed to the photoelectric multiplier tube by a detection fiber. Disadvantages of prior art

[0010] Current devices have several drawbacks.

[0011] The use of fiber elements ensuring both the detection of ionizing particles and the transmission of scintillation light introduces dead zones between each detection element and therefore limits the sensitivity of the device.

[0012] Moreover, the use of fiber elements ensuring both the detection of ionizing particles and the transmission of scintillation light imposes a compromise between spatial resolution, sensitivity and number of electronic channels.

[0013] Thermal noise generated by photodetectors (such as Silicon SiPM photomultipliers) introduces significant interference which can distort the detection of real events, particularly when it comes to detecting low-energy beta particles.

[0014] In general, there is a need for a system significantly improved in terms of sensitivity and resolution, capable of quantifying the contribution of detected beta and gamma particles, while optimizing light collection and reducing detection limitations due to thermal noise in photodetectors. Solution provided by the invention

[0015] In order to overcome these drawbacks, the present invention relates to an intraoperative probe for guiding an excision tool, comprising a detection head, said detection head comprising a plurality of optical fibers each coupled to a photodetector characterized in that: • said optical fibers are transparent and free of scintillator, • the proximal end of each of said transparent fibers is optically coupled to a light guide itself coupled to a single continuous scintillator, for example annular in shape, designed to capture beta and / or gamma particles and emit light in response to this interaction, said single continuous scintillator being optically coupled to a light guide • the distal end of each of said transparent fibers is coupled to a photodetector (for example, a silicon photomultiplier) • said intraoperative probe is associated with a signal processing system, configured to analyze the signals delivered by the photodetectors, comprising: • a means of temporal coincidence analysis of said signals delivered by the photodetectors to discriminate real events from thermal noise, • a processing means enabling the reconstruction of the interaction position of the particles in the continuous scintillator from the distribution of the light transmitted by said optical fibers.

[0016] According to a first variant, this probe further comprises a control detector, consisting of a transparent optical fiber fused to a section of scintillating fiber, said scintillating section being covered with an absorbing material, preventing beta particles from penetrating the scintillating fiber while allowing the detection of gamma rays; said single continuous scintillator optically coupled to a light guide, having a cutout of a portion of its active surface to make room for the surface associated with the scintillating fiber of the control detector, said processing means enabling a reference measurement of the gamma noise level in the environment from the signal from the control detector, which can then be used to estimate by weighted subtraction the count associated only with beta particles in the continuous scintillator.

[0017] Preferably, the probe comprises a control detector consisting of a transparent optical fiber fused to a scintillating fiber segment. This scintillating fiber segment is coupled to a light guide and shielded from beta particles by the continuous scintillator and the light guide. Thus, the scintillating fiber segment serves both as a guide for the light from the continuous scintillator and as a detector for gamma rays. The time-coincidence analysis means makes it possible to discriminate the signals from the continuous scintillator and therefore to obtain a reference measurement of the gamma background noise from the signal from the control detector.

[0018] According to a second embodiment, this probe includes a witness detector, consisting of a transparent optical fiber fused to a scintillating fiber segment, said scintillating fiber segment being coupled to the light guide, so that said scintillating fiber segment serves both as a guide for the light from the continuous scintillator and as a detector for gamma rays; said time-coincidence analysis means performing an event discrimination system, configured to separately analyze the signals from the continuous scintillator and the scintillating fiber of the witness detector, and thus obtain a reference measurement of the gamma noise level in the environment from the signal from the witness detector.

[0019] Advantageously, said signal processing system is configured to perform time-coincidence analysis of signals captured by several photodetectors, so that signals received simultaneously by several optical fibers indicate a real event, while isolated signals received by a single photodetector are rejected as thermal noise (with the exception of the signal associated with the control fiber for the first variant).

[0020] Preferably, said continuous scintillator, the light guide and said optical fibers are surrounded by a reflective coating to optimize the collection of light emitted by the scintillator and maximize the transmission of light to the photodetectors.

[0021] According to a particular embodiment, said signal processing system is configured to apply discrimination based on temporal coincidence and comparison of the amplitudes of the signals from the different photodetectors, in order to obtain a reference measurement of the gamma background noise.

[0022] Advantageously, said signal processing system includes a neural network or a machine learning algorithm configured to analyze the distribution of light captured by the optical fibers and reconstruct the interaction position of the particles in the continuous scintillator.

[0023] Detailed description of a non-limiting example of embodiment

[0024] The present invention will be better understood upon reading the following description, concerning a non-limiting example of an embodiment illustrated by the accompanying drawings where:

[0025] [Fig-1] [Fig. 1] shows a three-quarter front perspective view of the detection head according to a first embodiment

[0026] [Fig.2] [Fig.2] represents another perspective view of the detection head, rotated 90° relative to the previous figure

[0027] [Fig.3] [Fig.3] represents another side perspective view of the head of detection of the detection head according to said first embodiment

[0028] [Fig.4] [Fig.4] represents a three-quarter front perspective view of the head of detection according to a second embodiment variant

[0029] [Fig. 5] [Fig. 5] represents another perspective view of the detection head, rotated 90° relative to the previous figure

[0030] [Fig.6] [Fig.6] represents another side perspective view of the head of detection of the detection head according to said second embodiment.

[0031] [Fig.7] [Fig.7] represents a schematic diagram of the processing of the delivered signals by each photodetector. General principle of the invention

[0032] The invention relates to a detection system using a continuous scintillator (10) in combination with an optical fiber array (20) to capture the scintillation light emitted during the interaction of ionizing particles with the scintillator (10). The light thus captured is guided to photodetectors, for example silicon photomultiplier tubes (30), which convert the light signals into usable electrical signals.

[0033] Each of the optical fibers (20) of the transmission beam is a transparent fiber, without a doped area interacting by scintillation with the ionizing particles. Each of the optical fibers (20) of the beam extends from the continuous scintillator (10) to a dedicated photodetector (30).

[0034] Optionally, several adjacent fibers (20) can be coupled to the same photodetector, provided, however, that the head comprises a plurality of photodetectors (30) each coupled to a limited number of adjacent fibers (20), preferably three adjacent fibers (20) at most.

[0035] This system is optimized to provide accurate detection of ionizing particles (1) while reducing thermal noise and interference from gamma background radiation.

[0036] The invention also relates to the use of a witness detector coupled to the continuous scintillator configuration (10), enabling effective discrimination between beta particles and gamma radiation. The various proposed variants aim to improve the sensitivity of the system, optimize light collection, and ensure high accuracy in the reconstruction of particle interaction events, while minimizing thermal noise.

[0037] The technical field covered by the present invention relates to ionizing particle detection technologies, with applications in radiation detection, environmental monitoring, radiological safety and medical imaging. Description of the single scintillator (10)

[0038] The operation of the continuous detection head is based on an annular scintillator (10), which can be organic or inorganic. This scintillator (10) captures beta (electron or positron) or gamma particles and emits light in response.

[0039] The scintillator (10) is, for example, an annular scintillator designed in the form of a ring (hollow cylinder) that detects ionizing particles (such as gamma rays or beta particles) by emitting light when it interacts with these particles. The annular scintillator (10) is preferably associated with an annular light guide (11) ensuring diffusion of the light towards several optical fibers (20).

[0040] The scintillating part typically has a length of about 500 µm and 2 mm for the control fiber, and a length of about 15 cm for the transparent fibers.

[0041] The annular scintillator (10) takes the form of a ring or a hollow cylinder with a recess (15), which allows the passage of an instrument or a suction tube or even an additional optical fiber, for example, for visual inspection through the hole (15) formed in the center of the ring. This shape provides 360-degree coverage around the object or area of ​​interest to be detected.

[0042] The annular scintillator (10) can be designed with different radii and thicknesses depending on the application and the type of radiation to be detected.

[0043] When ionizing particles (1), such as beta particles or gamma rays, interact with the annular scintillator (10), the latter emits light photons. The emitted light is then collected by optical fibers (20), preferably arranged perpendicular to the inner or outer surface of the ring scintillator (10). These fibers (20) carry the light to detectors (30) such as silicon photomultipliers (SiPM).

[0044] The fabrication of an annular scintillator (10) relies on several technical steps, which vary depending on the materials used and the application specifications. Scintillators can be made from organic or inorganic materials, each having specific properties in terms of luminous efficacy, scintillation time, and optical transparency.

[0045] Inorganic scintillators (for example, Nal(Tl), LaBr3, or BGO) are generally preferred for their high density and high luminous efficiency.

[0046] For an annular scintillator (10) according to the invention, it is important that the material be homogeneous and capable of emitting isotropic light in response to ionizing radiation.

[0047] In the case of organic scintillators, such as plastic scintillators, such an annular scintillator (10) can be manufactured by molding into specific annular shapes using vacuum molding techniques. This makes it possible to form a homogeneous ring without air inclusions, which improves light transmission.

[0048] Plastic scintillators, such as polystyrene doped with fluorophores, can also be extruded into a ring shape. This method allows for easier manufacturing of organic scintillators.

[0049] Inorganic scintillators can also be cut or machined from a block to obtain the desired annular shape. Machining scintillators such as Nal(Tl) is delicate because this material is hygroscopic and brittle.

[0050] Once the annular shape is obtained, the scintillator can be coated with a reflective material, such as aluminium or Teflon, to improve the internal reflection of photons and maximize the light guided towards the optical fibrees.

[0051] The scintillator can be coated with a thin transparent protective layer to protect against moisture (for hygroscopic scintillators such as Nal(Tl)). The interface with the transparent optical fibers (20) is preferably provided by an annular diffuser (11).

[0052] The optical coupling surfaces (where the optical fibers are connected) are polished to minimize photon loss and optimize coupling with the optical fibers.

[0053] The optical fibers are preferably arranged perpendicular to the external surface of the diffuser (11) or the annular scintillator (10). They capture the scintillation light produced during the interaction with the ionizing particles and guide it towards photodetectors (such as SiPMs, photodiodes or PMT photomultipliers).

[0054] The optical coupling between the scintillator (10), the diffuser (11) and the optical fibers (20) is optimized by applying optical gels or adhesives to maximize light transmission.

[0055] Once the ring scintillator is manufactured and the optical fibers are coupled, it is integrated into the detection head. The scintillator is mounted in a mechanical structure that ensures the stability and protection of the scintillating ring (10) and the optical fibers (20).

[0056] The optical fibers (20) are then connected to photodetectors (30), for example SiPMs or PMTs, to convert the light into an electrical signal, which is then analyzed to determine the characteristics of the detected ionizing particles (interaction position and energy).

[0057] Transmission of photons emitted by the annular scintillator.

[0058] The ring scintillator (10) emits light isotropically. To capture this light efficiently, several optical fibers (20) are arranged around or near the scintillator. The light is then collected by several optical fibers (20) simultaneously.

[0059] The light emitted by the scintillator (10) is guided towards the optical fiber bundle (20). To improve the amount of light captured, the scintillator, the light guide, and the optical fibers are advantageously coated with a reflective coating that reflects the photons back towards the fibers. This maximizes the light available to the detectors.

[0060] The optical fibers (20) are physically in contact with the surface of the scintillator (10) or with the surface of the annular diffuser (11). The light emitted by the scintillator (10) enters the optical fibers through direct optical coupling or a material with a suitable refractive index, such as an optical adhesive, to improve light collection. The optical fibers carry this light to the photodetectors, where the light is converted into an electrical signal.

[0061] By means of the light distribution measured on several fibers, the interaction position of the particles in the scintillator is reconstructed. A neural network can be used for this task.

[0062] At the output of the optical fibers, the light is detected by photodetectors (photomultiplier tubes (PMTs) or SiPMs). These devices transform the light photons into an electrical signal proportional to the intensity of the light captured. The SiPM is a very compact, sensitive semiconductor device that can detect very low levels of light, even from just a few photons. Each optical fiber can be coupled to its own photodetector, or several fibers (20) (preferably no more than three) can be directed to a single detector (30) for collective processing.

[0063] If several optical fibers (20) and several photodetectors (30) are used, the distribution of light on the fibers makes it possible to precisely locate where the particle interacted with the scintillator (10). By analyzing the light on several fibers and the temporal coincidences, the system can reconstruct the position of the interaction event and discriminate real particles from thermal noise. Thermal noise reduction

[0064] To improve detection sensitivity, a noise discrimination mechanism is integrated to eliminate thermal noise from the photodetectors.

[0065] Thermal noise is a spurious signal generated by the photodetectors (30), even in the absence of radiation. This thermal noise originates from the thermal agitation of charge carriers inside the photodetectors, which generates signals similar to those generated by ionizing particles.

[0066] To partially eliminate thermal noise from SiPMs, a temporal coincidence analysis of optical signals on several fibers is performed: scintillation light created by a real detection event (a beta or gamma particle) will simultaneously activate several optical fibers (20) and therefore several photodetectors (30), whereas a thermal noise event will activate only one photodetector. By using temporal coincidence techniques, it is possible to significantly reduce photodetector noise and thus improve detection sensitivity.

[0067] Temporal coincidence: when several optical fibers (20) capture scintillating light at the same time, there is a high probability that this event is real (radiation). On the other hand, a signal emanating from only one SiPM without activation of the others is very likely due to thermal noise.

[0068] Filtering: By measuring the temporal coincidence between the signals of the different fibers, it is possible to discriminate between real events (where several fibers or SiPMs are activated simultaneously) and thermal noise signals that activate only a single SiPM. This makes it possible to effectively reduce thermal noise by considering only the events where several fibers show a signal simultaneously.

[0069] When a beta or gamma particle enters the ring scintillator (10), it interacts with the material and generates scintillation photons. These photons are scattered through the scintillator and collected by several optical fibers (20) strategically placed around or near the scintillator. Each fiber guides the light to a photodetector, where the photons are converted into an electrical signal.

[0070] By using signal processing techniques, such as reconstruction of the interaction position based on the distribution of light on the different fibers and temporal coincidence to eliminate thermal noise, the system can determine the exact position of the detection and ensure high sensitivity with minimal interference due to thermal noise from the photodetectors. Gamma background noise reduction

[0071] Gamma noise refers to gamma radiation from the accumulation of the radiotracer in regions distant from the area of ​​interest, which can interfere with the detection of beta particles. This type of noise is particularly problematic when attempting to isolate beta events, as gamma rays can activate the scintillator and produce a similar signal. The control detector (40) is used to measure gamma noise in real time. The control detector (40) consists of a scintillating fiber, specially designed to capture gamma rays without being influenced by beta particles.

[0072] Using the signals from the control detector (40) as a reference, the system can estimate the gamma background noise. The main scintillator (10) captures both beta and gamma particles, while the control detector (40) is only sensitive to gamma rays.

[0073] By subtracting the signals measured by the control detector (40) (which only captures gamma rays) from those of the continuous scintillator (10), the signal due only to beta particles can be estimated.

[0074] On this principle, several configurations can be implemented to reduce the gamma background noise from the annihilation of positrons in matter, using a witness detector consisting of an additional scintillating fiber (40). First variant of implementation

[0075] In the first embodiment illustrated in Figures [Fig. 1], [Fig. 2], and [Fig. 3], a witness detector (40) is used to estimate the gamma background noise and improve the detection accuracy of events associated with beta particles (electron or positron). The witness detector consists of an optical fiber (41) fused to a thin layer of scintillator fiber (40). This scintillator fiber (41) also captures ionizing radiation, but it has a different function from that of the main scintillator (10).

[0076] The scintillating fiber (40) of the control detector is coated with an absorbing material (45) forming a shield that blocks beta particles but allows gamma radiation to pass through. Consequently, the control detector (40) is primarily sensitive to gamma radiation.

[0077] The main scintillator (10) is said to be "amputated" of the detection surface associated with the scintillating fiber of the control detector. This means that a small portion (12) of the surface of the annular scintillator (10) is not used for particle detection in the main system. This portion of the scintillator is dedicated to control detector. In other words, the active area of ​​the continuous scintillator (10) is reduced to allow the control detector (41) to act independently and capture exclusively the gamma background noise.

[0078] The continuous scintillator (10) captures beta or gamma particles (1), and the emitted light is transmitted to the optical fibers (20) for analysis. However, under certain operating conditions, it is necessary to be able to distinguish beta events from gamma background noise. The control detector (41) plays a crucial role here. Since it is primarily sensitive to gamma rays (because beta particles are blocked by the absorbing material), it can provide a reference measurement of the gamma noise level in the environment.

[0079] By subtracting this reference measurement of the gamma background noise from the signal detected by the continuous scintillator (10), it is possible to obtain an estimate of the pure beta signal. This improves the detection specificity of the system.

[0080] This configuration is useful in environments where it is essential to accurately detect beta particle activity without contamination from gamma radiation, for example in medical or industrial environments where gamma particles may be ubiquitous. The ability to accurately estimate gamma noise allows for a better interpretation of the actual events captured by the main detector.

[0081] Amputation of the surface of the continuous scintillator to integrate the witness detector allows for an accurate estimation of gamma noise and for discriminating with greater certainty the captured events, which is crucial in applications requiring fine detection of beta particles with a minimum of false detections. Second variant of implementation

[0082] The second embodiment of the continuous detection head illustrated by Figure [Fig.4], [Fig.5] and [Fig.6] features a design where the witness detector consists of an optical fiber (41) fused to a small thickness of scintillating fiber (40) which fulfills two roles: it guides the light from the continuous scintillator and serves as a detector for gamma radiation.

[0083]

[0084] While in the first variant the control detector is covered with an absorbing material (45) to block beta particles, here the scintillating fiber is made sensitive only to gamma radiation thanks to the continuous scintillator (10) and the light guide (11) which act as shielding for the control detector (40),

[0085] Unlike the first variant, the scintillating fiber (41) serves two functions: • Detecting gamma radiation: the scintillating fiber (41) detects gamma radiation and emits light in response. • Guiding the light: In addition to serving as a detector, the scintillating fiber (41) helps to guide the light emitted by the main continuous scintillator to the photodetectors.

[0086] According to an alternative, the scintillating portion is covered with a reflective coating that prevents light from the continuous scintillator from passing through this fiber. The witness fiber is in this case self-contained, as in the first variant, but without encroaching on the surface of the continuous scintillator.

[0087] The scintillating fiber (41) is coupled to the light guide (11), which diffuses the light emitted by the continuous scintillator (10) and directs it towards the optical fibers (20).

[0088] In this configuration, the scintillating fiber (40) collects the light from the gamma rays directly via its own scintillation (31), but it also acts as part of the light guiding system for the light emitted by the continuous scintillator (10).

[0089] The scintillating fiber detects gamma radiation directly by capturing the photons emitted during the interactions of gamma particles with the fiber. When gamma rays pass through this thin layer of scintillating fiber, it scintillates and emits light. This light is then guided primarily along the fused optical fiber, which carries the light to a photodetector (30), capable of converting the photons into an electrical signal.

[0090] In addition to serving as a detector, the scintillating fiber (40) is also coupled to the light guide (11). The continuous scintillator (10) (which captures both beta and gamma particles) emits light when it interacts with these particles. This light is scattered by the light guide (11) and then transmitted to the optical fiber array (20), of which the scintillating fiber (41) is a part in the control detector (40), which helps guide this light to the associated photodetector, in addition to its own role in gamma detection.

[0091] In this embodiment, when ionizing particles (such as beta or gamma particles) interact with the continuous scintillator, several optical fibers simultaneously collect the emitted light. The photodetectors (30) coupled to these fibers (20) detect this light at the same time, and the signals are recorded in temporal coincidence.

[0092] Conversely, when a gamma ray interacts in the control detector, only the photodetector associated with the fused fiber will be triggered. It is thus possible to discriminate, by temporal coincidence, the signals from the continuous scintillator and the control scintillator. As with the first variant, this makes it possible to obtain a reference measurement of the gamma noise level in the environment from the signal from the control detector. Comparison between the two variants

[0093] Unlike the first variant, where the control detector (40) is isolated from beta particles using an absorbing material, in this second variant, the scintillation fiber of the control detector (40) is directly integrated into the light guiding system and participates in the collection of scintillation light. In addition to directly detecting gamma rays, the scintillation fiber helps guide the light emitted by the main scintillator, making the system more efficient by optimizing light capture in the optical fibers (20).

[0094] The use of a scintillating fiber integrated into the light guidance system for gamma detection not only allows for the quantification of gamma background noise, but also optimizes the collection of light emitted by the continuous scintillator. Another very important advantage is that the surface area of ​​the continuous scintillator is not reduced, resulting in a significant increase in the detection area and therefore in the sensitivity of the device. Improved light collection

[0095] Another key aspect of detection relies on improving the collection and guidance of scintillating light. This optimization makes it possible, in particular, to improve the detection of low-energy beta particles.

[0096] The scintillator, the light guide (11), and the optical fibers (20) are advantageously surrounded by a reflective coating that prevents the emitted light from escaping in unnecessary directions. This coating redirects the emitted photons toward the optical fibers (20), thus improving the efficiency of light collection.

[0097] In the second embodiment, the scintillating fiber coupled to the light guide also plays a role in improving light transport to the detectors by increasing the number of collection fibers. Improved light collection and guidance maximizes the amount of photons directed to the photodetectors while minimizing signal loss due to misdirected or uncaptured photons, thus increasing the signal-to-noise ratio.

[0098] The light guide (11) ensures diffusion of light towards several optical fibers (20) and therefore also optimizes the collection of scintillation light produced by the continuous scintillator (10),

[0099] Digital filtering and signal processing for noise suppression

[0100] Finally, a significant part of noise reduction in these systems relies on digital signal processing techniques. Once the signals are collected by the photodetectors, they can be analyzed and processed by digital algorithms that apply filters to eliminate spurious signals and enhance the reliability of the detected events.

[0101] Method for reducing thermal noise by analyzing the shape of signals: in addition to the temporal coincidence mentioned above, algorithms can These algorithms can be used to analyze the shape of signals over time. Thermal noise signals have a different shape than signals from real events, such as an interaction with a beta or gamma particle. Algorithms can filter out signals whose shape does not match that expected for an ionizing particle detection event.

[0102] Gamma noise reduction method by energy filtering of signals: In addition to the use of the control detector mentioned above, energy filtering can be used to discriminate between the signals generated by the interaction of beta and gamma particles in the continuous scintillator. The energy distribution deposited by these two types of radiation is indeed different, and it is therefore possible to eliminate a significant portion of the gamma events without significantly degrading the detection of beta particles by applying a suitable energy threshold.

[0103] After recording a signal, the digital algorithm compares the shape of the signal to a database of typical events. If the shape of the signal corresponds to thermal noise, it is rejected, while a signal corresponding to an interaction with a particle is retained.

[0104] Noise reduction in detection systems using a continuous scintillator with optical fibers (20) relies on a combination of techniques: time coincidence to eliminate thermal noise, the use of a witness detector (40) to discriminate between gamma and beta events, improved light collection through a reflective coating and an optimized light guide, and digital filtering methods to refine the quality of the detected signals. Together, these techniques increase the signal-to-noise ratio and enable accurate detection of ionizing particles while minimizing interference.

[0105] Exploitation of the signal delivered by each photodetector

[0106] The exploitation of the signal delivered by each photodetector in a detection system using a scintillator and optical fibers (20) is a crucial step for interpreting the detection events of beta and gamma particles.

[0107] The photodetector converts the light emitted by the scintillator in response to the ionizing particles into an electrical signal, which is then processed to determine the characteristics of the detected event.

[0108] Schematic diagram of the signal processing system for signals delivered by each photodetector

[0109] Figure [Fig.7] illustrates the processing involved in the exploitation of the signal delivered by each photodetector:

[0110] Photon-to-electron conversion (51): The SiPM photodetector (30, 31) is a semiconductor detector designed to detect very small amounts of light (photons). Each optical fiber (20, 41) is coupled to a SiPM (30, 31) which captures the light originating from the scintillator. When photons from scintillation reach the surface of the SiPM (30, 31), they are converted into electrical charges by the photoelectric effect. The SiPM (30, 31) is composed of thousands of microcells, each behaving like an avalanche photodiode. Each incident photon can trigger an electron avalanche in a microcell. The total signal corresponds to the sum of the currents generated in the different microcells by the incident photons and is therefore proportional to the received light intensity.

[0111] Electrical signal amplification: The SiPM (30, 31) delivers an electrical current whose amplitude is proportional to the number of photons detected. This signal is then processed by electronics that integrate, amplify, and digitize the signals. This ensures that even very small amounts of light (such as a few photons) can be detected with high sensitivity.

[0112] Analog signal processing (52): The amplified signal is first processed in an analog manner to determine certain parameters, such as the charge collected at the output of the photodetectors, which is proportional to the energy of the detected event. • Measurement of the collected charge (53): The analog signal is integrated to determine the collected charge, which is proportional to the amount of light received by the SiPM (30, 31), which, in turn, is related to the energy deposited in the scintillator by the ionizing particle (beta or gamma). This collected charge makes it possible to quantify the energy of the detected event, to better distinguish different types of particles or to measure their energy. • Arrival time detection (54) (time-stamping): Another important piece of information is the time the event occurred. This is crucial for time-coincidence analysis and for discriminating real events from thermal noise (as described above). Therefore, a precise timestamp of the signal is performed for each SiPM (30, 31).

[0113] Digital signal processing (55): Once the analog signals have been captured and amplified, they are converted into digital signals for more complex processing. Here are the main steps of this digital processing:

[0114] a. Temporal analysis and coincidence (56) • The signal delivered by each SiPM (30, 31) is continuously analyzed to detect when it receives a signal (i.e., when a packet of photons from scintillation reaches the surface). The temporal coincidence between several SiPMs (30, 31) is analyzed. If several SiPMs (i.e., several optical fibers (20)) record a signal simultaneously, this indicates a real event (e.g., a beta or gamma particle). • Coincidence is an important criterion for discriminating real events from thermal noise, which generally activate only one SiPM (30, 31) at a time. • In the second variant, the temporal coincidence also makes it possible to discriminate between the signals from the control detector and the continuous scintillator. b. Reconstruction of the energy and interaction position of the detected events (57) • Information from each SiPM (30, 31), including arrival time and collected charge, is used to reconstruct the energy and position of the interaction event in the scintillator. • The sum of the charge collected by each SiPM in temporal coincidence is proportional to the energy of the detected particle. This measurement is useful in helping to differentiate between beta and gamma particles, as they generally have different energy signatures. • If the system uses several optical fibers (20) (as well as the control detector (40)) placed around the scintillator, the distribution of photons in these different fibers provides information on the position where the ionizing particle interacted with the scintillator. By comparing the amount of light received coincidentally by each SiPM (30, 31), the system can accurately estimate where the interaction occurred within the scintillator. • The annular light guide (11) allows the scintillation light to be diffused onto several optical fibers (20). Adjusting its thickness and optical coating therefore optimizes the distribution of light on the optical fibers (20) in order to reconstruct the interaction position of the detected particle with greater accuracy. • Neural network or other advanced algorithms: In some systems, sophisticated algorithms, such as neural networks, can be used to analyze the signals from the different SiPMs and perform an accurate reconstruction of the interaction position of the event. c. Thermal noise filtering (58) • As mentioned previously, digital processing applies filters to eliminate thermal noise and spurious gamma signals. Thermal noise, which typically activates only one SiPM, is rejected through time-coincidence analysis.

[0115] Data communication: Once signal processing is complete, the data (position, energy, time, etc.) are sent to a data collection system for further analysis or for use in specific applications (such as radiation detection, medical imaging, etc.). The results may can also be used in real time for certain applications such as radio-guided surgery.

[0116] Nomenclature Ionizing particles (beta or gamma) (1) Single continuous scintillator (10) Light guide (H) Inactive surface of the scintillator (12) Central recess of the scintillator (15) Optical fiber (20) Photodetector (30), (31) Witness detector (scintillating fiber) (40) Absorbing material of the witness detector (45) Transparent optical fiber of the witness detector (41) Photon-to-electron conversion (SiPM module) (51) Analog signal processing (52) Measurement of the collected charge (53) Arrival time detection (54) Digital signal processing (55) Time analysis and coincidence (56) Energy and position reconstruction (57) Thermal noise filtering (58)

Claims

Demands

1. - Intraoperative probe for guiding an excision tool, comprising a detection head, said detection head comprising a plurality of optical fibers (20) each coupled to a photodetector characterized in that • said optical fibers (20) are transparent and free of scintillator, • the proximal end of each of said transparent fibers (20) is optically coupled with a single continuous scintillator (10) optically coupled to a light guide (11), capable of capturing beta and / or gamma particles and emitting light in response to this interaction, • the distal end of each of said transparent fibers (20) is coupled to a photodetector (30), • and in that said intraoperative probe is associated with a signal processing system, configured to analyze the signals delivered by said photodetector (30), comprising: • a means of temporal coincidence analysis of said signals delivered by said photodetector (30) to discriminate real events from thermal noise, • a processing means enabling the reconstruction of the interaction position of the particles in said continuous scintillator (10) from the distribution of the light transmitted by said optical fibers (20).

2. - Intraoperative probe to guide an excision tool, according to the Claim 1, characterized in that it further comprises a witness detector consisting of a transparent optical fiber (41) fused to a scintillating fiber segment (40), said scintillating segment (40) being coated with an absorbing material (45), preventing beta particles from penetrating the scintillating fiber while allowing the detection of gamma rays; said single continuous scintillator (10) optically coupled to a light guide (11) having a cutout (12) of a portion of its active surface for leaving room for the surface associated with the scintillating fiber of the control detector (40), said control detector allowing a reference measurement of the gamma background noise present in the signal detected by the continuous scintillator (10).

3. - Intraoperative probe to guide an excision tool, according to the claim 1 characterized in that it comprises a witness detector (40), consisting of a transparent optical fiber (41) fused to a scintillating fiber segment (40), said scintillating fiber segment being coupled to a light guide (11) and protected from beta particles by the continuous scintillator (10) and the light guide (H).

4. - Intraoperative probe to guide an excision tool, according to the claim 1 characterized in that said signal processing system is configured to perform time-coincidence analysis of signals captured by several photodetectors (30, 31), so that signals received simultaneously by several optical fibers (20) indicate a real event, while isolated signals received by a single photodetector (30) are rejected as thermal noise.

5. - Intraoperative probe to guide an excision tool, according to the claim 1 characterized in that said continuous scintillator (10), light guide (11) and said optical fibers (20) are surrounded by a reflective coating to optimize the collection of light emitted by the scintillator and maximize the transmission of light to the photodetectors (30, 31). 6 - Intraoperative probe for guiding an excision tool, according to claim 1 characterized in that said signal processing system is configured to apply discrimination based on temporal coincidence and comparison of the amplitudes of signals from the different photodetectors (30, 31), in order to obtain a reference measurement of the gamma background noise.

7. - Intraoperative probe to guide an excision tool, according to the claim 1 characterized in that said signal processing system comprises a neural network or a machine learning algorithm configured to analyze the distribution of light captured by the optical fibers (20) and reconstruct the interaction position of the particles in the continuous scintillator (11).