Apparatus and respective method for improved determination of the fine location of at least one tracer within a body part of a patient - Patents.com

Abstract

The present invention relates to a method and apparatus for simultaneously monitoring several body parts of a patient by high-resolution and high-sensitivity detection techniques for detecting radiation emitted by tracers. The object of the present invention is to provide an apparatus for improved determination of the fine location of at least one tracer within a body part of a patient, comprising a first pair of high-resolution detectors of opposing detectors and a second pair of high-sensitivity detectors of movable opposing detectors, the apparatus being configured to determine a coarse location based on signals from the first pair of opposing detectors, determine a location of the second pair of opposing detectors based on the coarse location, and determine the fine location of the tracer based on signals from the second pair of opposing detectors, so as to be able to determine the location of the tracer with high spatial resolution and high sensitivity.

Description

[Technical field]

[0001] The present invention relates to a method and device for simultaneously monitoring several body parts of a patient by high resolution and high sensitivity detection techniques for detecting radiation emitted by a tracer, for example by Positron Emission Tomography (PET).

[0002] The device and method according to the invention can preferably be used in the field of nuclear medicine, in particular for determining the position of an injected tracer administered to a patient. [Background technology]

[0003] Positron Emission Tomography (PET) has high clinical potential as a functional imaging modality of the patient's body, where simultaneous imaging of the whole body is particularly promising since organs interact with each other. Here, one or more tracers, such as radioactive contrast agents, are injected into the patient's body. Those tracers have a higher affinity for certain cells that may be located in distant parts of the patient's body.

[0004] The radioactive tracer emits a positron, which annihilates with an electron in the patient's body after a certain range. After annihilation, a pair of consecutive photons is emitted, which eventually exits the patient's body. The photon pair is detected by two opposing detectors. In the case of scintillator crystals, there is a possibility of interaction of the photons with the detector, which depends on the density and number of atoms in the detector. High light output and short decay time are desired for optimal signal. In addition to the possibility of interaction, in gas detectors such as resistive plate chambers (RPC), electrons can be extracted from the resistive material. A compromise between the two is desirable for optimal signal.

[0005] Scintillator-based systems are discrete, either in the form of pixelated crystals connected one-to-one to a photomultiplier tube (PMT), or in the form of monolithic crystals read out by multiple PMTs. RPC-based systems are continuous, since the collision position is determined from the charge weight between the readout channel and the interaction depth of the collision. The latter detectors are essentially parallax-free and therefore perform better in terms of spatial resolution. The former detectors perform better in terms of sensitivity.

[0006] Both concepts have been proposed for PET systems with a large axial field of view (AFOV). Such systems would allow imaging of the whole body in a single scan with increased sensitivity. This would reduce the dose injected into the patient, decrease the total acquisition time, and open the possibility of tracking tracers moving through the patient's body in real time.

[0007] Scintillator-based systems with large AFOV are rather expensive since the total cost increases linearly with the number of detectors. RPC-based systems are more cost-effective since they aim to cover a large area. However, their sensitivity is smaller compared to scintillator-based systems.

[0008] Scintillator crystals, on the other hand, have poorer spatial resolution at large acceptance angles because their interaction depth plays a strong role for photons that hit the detector obliquely, but they are more flexible than RPCs and can assume different geometries for photons that hit perpendicularly, thus reducing parallax effects and improving spatial resolution.

[0009] US9632187B2 discloses a system and method for a PET kit. The detector kit may include a gantry, a plurality of PET detector modules, and an event processing device. The PET detector modules may include a housing. Such housing may include a connection element configured to removably and adjustably couple the PET detector module to the gantry. The detector module includes a crystal arranged in the housing and a photodetector configured to detect light by the crystal. The detector module further includes a communication component configured to communicate data from the at least one photodetector to the event processing device to determine coincidence events based on the received data. The disclosure also relates to a method for adjusting the position of the PET detector module relative to a first gantry and for decoupling the PET detector module relative to the first gantry via the connection element. The method further includes coupling the PET detector module to a second gantry.

[0010] WO2012 / 087171A1 discloses an apparatus for PET with time-of-flight and whole-body scanning in a single bed position and a corresponding readout method. The apparatus includes at least four detector modules arranged around an apparatus axis forming a polygon. The modules include resistive plate chambers (RPCs) as gamma photon detectors. Such an apparatus further includes electronic readouts coupled to both ends of the apparatus within the modules. The disclosure also relates to a readout method.

[0011] "Imaging Techniques in RPC-PET" PhD Thesis by Paulo Martins, University of Coimbra, 2014, describes an apparatus for PET imaging of small animals. Such an apparatus includes an RPC detector and a readout system. The paper also describes a method to determine the fine position of gamma ray photon impingement on the detector. A method to reconstruct whole-body images using a graphics processing unit is also shown. The reconstruction method includes a time-of-flight based method to remove scattering events in the human body. Clinically relevant reconstruction times were demonstrated. Summary of the Invention [Problem to be solved by the invention]

[0012] The present invention provides a cost-effective solution that still allows for determining the location of a tracer within a patient's body with high spatial resolution and high sensitivity. [Means for solving the problem]

[0013] The mentioned problem is solved by an apparatus and a method for determining the position of a tracer in a patient's body, as well as a computer program product comprising executable instructions for carrying out the method according to the subject matter of the independent claims. Preferred embodiments of the invention, which may be realized in an isolated manner or in any combination, are disclosed in the dependent claims.

[0014] As used herein, the term "comprising" or grammatical variations thereof is understood to specify the presence of stated features, integers, steps, or components or groups thereof, but does not exclude the presence or addition of one or more other features, integers, steps, components or groups thereof. The same applies to the term "having" or grammatical variations thereof, which are used as synonyms of the term "comprising".

[0015] According to one aspect of the present invention, an apparatus is provided for improved determination of the fine location of at least one tracer within a patient's body, particularly a body part.

[0016] The apparatus includes a first pair of opposing detectors that are high resolution detectors and a second pair of opposing detectors that are moveable and that are high sensitivity detectors.

[0017] In a further aspect, the apparatus comprises: a) acquiring one or more first signals from a first pair of opposing detectors, the one or more first signals including spectral information corresponding to radiation emitted by the tracer; b) determining a general location of the tracer based on the one or more first signals; c) positioning a second pair of opposing detectors based on the determined coarse location; d) acquiring one or more second signals from the second pair of opposing detectors, the one or more second signals including electromagnetic spectrum information corresponding to radiation emitted by the tracer; e) determining a fine location of the tracer based on the one or more second signals.

[0018] Thus, the device for determining the location of a tracer in a patient's body may preferably be used to image the function of a body part of a patient, where the body part of the patient includes tumor tissue, where the tumor tissue may include a neoplastic mutation that may have been introduced into the patient's tissue by a cancer.

[0019] Using a first pair of opposing detectors to determine a coarse position and, based on such coarse position, positioning a second pair of opposing detectors from which to determine a fine position allows for a reduction in the number of detectors, particularly detectors offering high sensitivity, compared to prior art solutions.

[0020] Alternatively or additionally, the device for determining the position of a tracer within a patient's body may also be used to correlate images acquired from two body parts simultaneously (images corresponding to signals acquired from opposing pairs of detectors).

[0021] As indicated above, the device is used in situations where a patient's body is scanned following injection of a tracer. As used herein, the term "tracer" refers to a radioactive imaging agent such as 18F-fluorodeoxyglucose (FDG).

[0022] According to the present invention, the device has at least two pairs of opposing detectors, the term "opposing detectors" referring to detectors facing each other with the patient's body between them.

[0023] According to the invention, the device includes a detector with high spatial resolution and a detector with high sensitivity. As used herein, the detector is assigned to determine gamma radiation generated by the annihilation of positrons in the patient's body. As used herein, the term "detector" refers to a device assigned to generate a measurable signal from incident gamma rays. For this purpose, the measurable signal may preferably be selected from an electrical signal, in particular a voltage or a current. In particular, the detector element may be selected from at least two of the following: resistive plate chambers (RPC), micropattern gas detectors (MPGD), fast timing MPGD (FTM), gas electron multipliers (GEM), photomultiplier tubes (PMT), solid-state single photon sensitive devices (silicon photomultipliers; SiPM), position sensitive photomultiplier tubes (PSPMT), avalanche photodiodes (APD), charge-coupled devices (CCD), complementary metal oxide semiconductors (CMOS), or quantum image sensor (QIS) chips. However, other types of detector elements may also be possible. In particular, it is particularly preferred that opposing detectors are of the same type and variety to enhance comparability of signals measured between individual detectors.

[0024] Preferably, the first pair of opposing detectors are continuous detectors and the second pair of opposing detectors are discrete detectors.

[0025] In a preferred embodiment, the device may include at least one first pair of opposing detectors and / or at least one second pair of opposing detectors, more preferably 2, 4, 8, 12, 16, 20 or more pairs of first and second opposing detectors, where the detectors of each pair are spaced apart from each other and therefore closer to the patient's body can be determined with increased spatial resolution.

[0026] Furthermore, the device may further comprise an evaluation device. As generally used, the term "evaluation device" relates to a device assigned to determine the obtained first and second signals, which contain information about gamma radiation, acquired by the first and second pairs of opposing detectors and which may in particular be based on measurable signals provided to the evaluation device by the first and second pairs of opposing detectors. For this purpose, a wire-based connection between the first and second pairs of opposing detectors and the evaluation device or, alternatively or additionally, a wireless connection may be provided.

[0027] The evaluation device according to the invention may be designed in particular for determining the position of the tracer in the patient's body, where such information may be based on measurable signals provided to the evaluation device by at least two detectors. For this purpose, the evaluation device may include a high-speed analog-to-digital converter, preferably having a sampling rate of 10 ns, more preferably 4 ns, more preferably 1 ns or less. Here, the high-speed analog-to-digital converter may preferably be selected from at least one of a flash analog-to-digital converter (FADC), a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), a versa module eurocard (VME) digitizer, a time readout board (TRB) or an oscilloscope. However, other types of high-speed analog-to-digital converters are also conceivable.

[0028] Additionally, the evaluation device may further comprise a clock which assigns a timestamp to each detector signal and provides time synchronization of the detector signals, preferably with nanosecond or picosecond level precision, more preferably with an accuracy of 100 ps or better.

[0029] Additionally, the assessment device may further include a motion sensor for monitoring motion, such as subject motion. The motion sensor may include monitoring of physiological parameters, such as cardiac motion and respiratory motion.

[0030] In a further aspect of the invention, a method is provided for improved determination of the fine location of a radiation-emitting tracer within a body part of a patient.

[0031] The method according to the invention comprises at least the following steps, but can further perform additional steps. In a preferred embodiment, the steps shown may be performed in a sequential approach, however, subsequent steps may be performed at least partially simultaneously with the previous steps. Alternatively, in a preferred embodiment, the steps mentioned may be performed in an integrated or mixed approach, in particular by combining a sequential approach and an integrated approach, in order to minimize the time and / or storage space required to perform the method. Furthermore, further steps not shown here may also be performed.

[0032] It is understood that the method of the present invention, in any of its embodiments, is carried out by the device of the present invention, said method comprising the following steps: a) acquiring one or more first signals acquired sequentially from a first pair of opposing detectors, the one or more first signals including spectral information corresponding to radiation emitted by the tracer; b) determining a general location of the tracer based on the one or more first signals; c) positioning a second pair of opposing detectors based on the determined coarse positions; and d) acquiring one or more second signals from the second pair of opposing detectors, the one or more second signals comprising electromagnetic spectrum information corresponding to radiation emitted by the tracer; e) determining a fine location of the tracer based on the one or more second signals; Includes.

[0033] Such a method allows a coarse position to be determined based on signals obtained from a first pair of opposing detectors, and a second pair of opposing detectors to be positioned based on such coarse positions, from which a fine position is determined, thus allowing a reduction in the number of detectors (especially detectors offering high sensitivity) compared to prior art solutions.

[0034] Furthermore, a computer program product comprising executable instructions for carrying out the method of the present invention in any of its embodiments is an object of the present invention. [Brief description of the drawings]

[0035] Further optional details and features of the invention can be derived from the following description of preferred embodiments, preferably in combination with the dependent claims, in which each feature can be realized in an isolated manner or in any combination. The invention is not limited to the preferred embodiments. The same reference numbers in the figures refer to identical elements, or elements with the same or similar function, or elements that correspond to each other in terms of their function. [Figure 1] FIG. 1 shows a side view of a preferred embodiment of an apparatus for determining the location of a tracer within a patient's body according to the present invention, the apparatus including two opposing planar detectors with high spatial resolution and two adaptive opposing detectors with high sensitivity. [Diagram 2]FIG. 13 further illustrates a preferred embodiment of the device for determining the location of a tracer in a patient's body in a perspective view, in which the parallel high-resolution detectors are fixed and the high-sensitivity detectors can be moved by a mechanical unit in axial and horizontal and vertical transverse axes relative to the site of interest, and positioned around an axis intersecting the tracer such that gamma rays strike perpendicularly to their front faces. The device further includes an actuator along a radial axis intersecting the rough location of the tracer such that the distance of the second pair of opposing detectors relative to the rough location of the tracer is minimized. The device can further assume a configuration in which the entire device rotates ±90 degrees, the high-resolution detectors are below and above the patient platform, and the high-sensitivity detectors move laterally relative to the patient. [Diagram 3] FIG. 1 shows a perspective view of a further preferred embodiment of an apparatus for determining the location of a tracer within a patient's body, the apparatus including a pair of detectors that can be used to image a part of the body (e.g., the brain) and another pair of detectors that are used to image another part of the body (e.g., the pelvis). [Figure 4] FIG. 1 shows a further preferred embodiment of an apparatus for determining the location of a tracer in a patient's body in a perspective view, the apparatus including a pair of detectors that cover the whole body and can track the location of the tracer in the body. Once the regions of interest are determined, the highly sensitive detectors move to those regions to obtain large statistics. [Diagram 5] 5A and 5B further illustrate a preferred embodiment of the method for determining the position of a tracer within the patient's body of FIG. 2 in a side view, with the high sensitivity detector moving between FIGS. 5A and 5B to adjust the spatial resolution according to the area of ​​interest provided by the parallel high resolution detector. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] Detailed description of the embodiments: In an embodiment of the device (110) of the present invention, a first pair of opposing detectors (116) are fixed.

[0037] In a further aspect of the device of the present invention, the device further includes a patient platform (124) adapted to receive a reclined patient, and the first pair of opposing detectors and the second pair of opposing detectors are positioned to detect radiation (123) emitted by a tracer in a body portion (112) of a patient (114) reclined on the patient platform (124).

[0038] In an advantageous embodiment of the apparatus of the present invention, the second pair of opposing detectors is movable at least about an axis of rotation (126) parallel to the patient platform (124) and / or a plane perpendicular to the patient platform (124).

[0039] In another advantageous aspect of the device of the present invention, the first pair of opposing detectors (116) and the second pair of opposing detectors (118) are positioned such that a plane perpendicular to the patient platform (124) intersects both the first pair of opposing detectors (116) and the second pair of opposing detectors (118), thereby allowing for improved alignment between the detectors.

[0040] In a further aspect of the device of the present invention, the first pair of opposing detectors (116) and the second pair of opposing detectors (118) are positioned to cover the entire patient platform (124) thereby enabling tracking of the position of the tracer within the entire body of the patient (114). In a preferred embodiment, the device of the present invention includes multiple pairs of first pair of opposing detectors (116) positioned along the patient platform (124) and / or multiple pairs of second pair of opposing detectors (118) positioned along the patient platform (124), thereby providing full body coverage of the patient (114) by being positioned along the patient platform (124), preferably the entire patient platform (124).

[0041] In one embodiment of the apparatus of the present invention, each of the first pair of opposing detectors (116) is associated with a single second pair of opposing detectors (118).

[0042] In an advantageous embodiment of the device of the present invention, each first pair of opposing detectors (116) is associated with multiple second pairs of opposing detectors (118), each first pair (116) having a length such that it covers a section of the patient platform (124) along which the multiple second pairs of opposing detectors (118) correspond. Such a solution makes it possible to reduce the number of first pairs of opposing detectors (116) by taking advantage of the continuity of such high resolution detectors.

[0043] In an embodiment of the apparatus of the present invention, the first pair of opposing detectors (116) and the second pair of opposing detectors (118) comprise positron emission tomography detectors.

[0044] In an advantageous embodiment of the device of the invention, it further comprises an evaluation device (128) consisting of a calculation device (129), which evaluation device (128) is adapted to determine the coarse position (121) according to step c) and to determine the fine position according to step e).

[0045] In one embodiment of the device of the present invention, the device further comprises a mechanical unit (130) configured to move and thereby position the second pair of opposing detectors (118). The evaluation device (128) is preferably further configured to provide the rough position (121) to the mechanical unit (130) for moving and thereby positioning the second pair of opposing detectors (118). The evaluation device (128) may further comprise a motion sensor, such sensor further configured to provide the patient movement to the mechanical unit (130) and thereby move the second pair of opposing detectors (118) in a manner synchronous with the patient movement.

[0046] In yet another advantageous aspect, the device of the present invention further comprises a first communication module (132) associated with the first pair of opposing detectors (116) and a second communication module (134) associated with the second pair of opposing detectors (118), each of the communication modules configured to transmit one or more first signals (120) and one or more second signals (122), respectively, to the evaluation device (128), and optionally the communication modules configured to operate via cable communication or wireless communication.

[0047] In an inventive embodiment of the method, step a) comprises determining the detector gap (136) in the horizontal transverse axis direction (133) where the radiation is detected in the first pair of opposed detectors (116), whereby step b) comprises determining the axial (131) direction of the radiation emitted by the tracer impinging on the first pair of opposed detectors (116) and the rough position (121) in the horizontal (133) and vertical (140) transverse axes. A disadvantage of scintillator detectors is the lack of depth of interaction (DOI). Apart from complex solutions based on polycrystals organized in two or three layers and algorithms that allow to measure the rough position of the impingement in the transverse axis direction in a monolithic scintillator, scintillator detectors cannot provide information about the transverse direction. Moreover, the more oblique the incident photon, the higher the possibility of energy deposition in several detectors. This is the so-called parallax effect. Many detectors have a small pitch (0.25 mm to 6 mm) and a large thickness (1 mm to 30 mm), which increases the probability that a photon will traverse several crystals and increases the angle of incidence of the photon on the detector.

[0048] In an additional inventive aspect of the method of the present invention, the positioning of the second detector in step c) is such that the detector can be moved along the axis (131) and along the horizontal (133) and vertical (140) transverse axes.

[0049] In another inventive aspect of the method of the invention, step e) comprises determining the time difference between the emission of the radiation emitted by the tracer and the arrival time of the radiation at each detector of the first pair (116) and reconstructing one or more second signals by a low-statistic time-of-flight reconstruction routine. The time difference in the arrival times of the photons at the opposing detectors, also called the time-of-flight (TOF), limits the so-called line of response (LOR) between the two detectors to a line segment. The TOF is thereby associated with accelerating the reconstruction routine and increasing the signal-to-noise ratio.

[0050] In one embodiment of the method of the invention, in the arrangement of step c), the detectors of the second pair of opposing detectors (118) are arranged with respect to an axis of rotation (126) transverse to the general location (121) of the tracer such that radiation emitted by the tracer strikes a detector of the second pair of opposing detectors perpendicular to the front face (135) of such detector. Events striking the detector perpendicularly with high resolution and sensitivity provide a more reliable means of measuring actual activity in the tracer since only those emitted by the tracer are detected.

[0051] In another aspect of the method, the positioning of step c) is such that the second pair of opposing detectors (118) are positioned by the actuator (144) along a radial axis (146) intersecting the approximate location (121) of the tracer such that the distance from the second pair of opposing detectors (118) to the approximate location (121) of the tracer is minimized and the sensitivity of the second pair of opposing detectors (118) is increased.

[0052] In one embodiment, step e) includes reconstructing one or more second signals based on the determined rough location (121) of the tracer using a maximum a posteriori (MAP) estimation algorithm. The use of PET-MR is to use the prior knowledge of the fine location of the anatomical structures provided by MRI and to model it in the reconstruction of the PET image. That is the so-called maximum a posteriori (MAP) estimation. MAP can be used to obtain point estimates of observed quantities based on empirical data. It is similar to maximum likelihood estimation (MLEM), but employs an optimization objective that incorporates a prior distribution for the quantity we want to estimate. This is considered as a regularization of MLEM. So far, MAP has not been used for PET data based on a prior PET distribution. It is mostly used with a prior MRI distribution. Its advantage is that it does not require MRI, since the prior knowledge is already provided by the high-resolution detector. This process can occur iteratively, feeding alternately PET distributions from both high-resolution and high-sensitivity detectors.

[0053] In yet another inventive aspect of the method of the present invention, it further comprises relating the location of the tracer in the at least two body parts (112) of the patient (114) by enabling to correlate the signals obtained from the at least two body parts (112) of the patient (114), said relating being: - determining the fine location of the tracer within a body region at a given time during the uptake period; - determining the fine location of the tracer in another part of the body at the same time during the uptake period; - measuring standard uptake values ​​at both sites during a predefined period of time and extracting a time correlation of uptake at both sites; Includes.

[0054] A related advantage is the simultaneous spatial tracking of the tracer and its dynamics (activity over time) in different parts of the body. Quantification techniques require blood sampling as input to correlate activity of the brain, heart, tumor, etc. Thus, the aim of the present invention is to simultaneously assess the location and dynamics of the tracer in different parts of the body. One or more tracers may have a longer uptake time and different dynamics in some organs compared to others. This can be quantified in a single scan without moving the patient and without drawing blood to estimate the true activity in the body. The metabolism of the tumor can be imaged with FDG and the myocardial perfusion of the heart with 82 Rubidium. This is so-called parametric imaging, where multiple organs are monitored simultaneously and their uptake is correlated with each other.

[0055] In an advantageous embodiment of the method of the invention, it further comprises correlating the location of the tracer within the whole body of the patient (114), said correlation comprising: - determining the fine location of the tracer within the patient's (114) body at a given time during the uptake period; - measuring uptake in the whole body and in the area of ​​interest; - correlating standard uptake values ​​in the whole body and in the area of ​​interest; Includes.

[0056] Because the usual procedure images the body from the eye to the thigh to reduce scanning time, some tumors go undetected. The brain, feet, and legs are usually left unscanned. However, detection of tumors in such locations provides an assessment of disease progression. A tumor that has spread from a melanoma to the leg would change the staging and treatment strategy. If a tumor in an unexpected location can be found on a cost-effective whole-body scan, a second pair of detectors can confirm and improve the fine location of the tumor.

[0057] Additionally, unexpected activity in a particular part of the body can trigger a second pair of detectors to be moved to that site. For example, if one wishes to assess an individual's sexual response, different parts of the body may get higher uptake, such as the heart, brain, and pelvic regions, among other parts. A whole-body scan can determine the site of interest and correlate a particular tracer that has affinity for that site with a tracer that has affinity for whole-body metabolism, such as FDG.

[0058] In one embodiment, the patient can see their body's function in real time, thus simulating other neurofeedback therapies.

[0059] Other modifications and variations will also be apparent to one of ordinary skill in the art.

Claims

1. 1. An apparatus (110) for improved determination of the fine location of at least one tracer within a body part (112) of a patient (114), said apparatus (110) comprising: a first pair of opposing detectors (116); a second pair of opposing detectors (118) movable relative to the first pair of opposing detectors (116), wherein the first pair of opposing detectors (116) comprises a detector having a higher resolution than the second pair of opposing detectors (118), and the second pair of opposing detectors (118) comprises a detector having a higher sensitivity than the first pair of opposing detectors (116); a) acquiring one or more first signals (120) from the first pair of opposing detectors, the one or more first signals including electromagnetic spectrum information corresponding to radiation (123) emitted by the tracer; b) determining a general location (121) of the tracer based on the one or more first signals (120); c) positioning the second pair of opposing detectors (118) based on the determined coarse position (121); d) acquiring one or more second signals (122) from the second pair of opposing detectors (118), the one or more second signals (122) comprising electromagnetic spectrum information corresponding to radiation (123) emitted by the tracer; e) determining a fine location of the tracer based on the one or more second signals (122); The apparatus (110) is configured as follows.

2. The apparatus (110) of claim 1, wherein the first pair of opposing detectors (116) are fixed.

3. 3. The apparatus (110) of claim 1 or 2, further comprising a patient platform (124), the patient platform (124) being suitable for receiving a lying patient, and the first pair of opposing detectors (116) and the second pair of opposing detectors (118) being positioned to detect radiation (123) emitted by a tracer within a body portion (112) of the patient (114) lying on the patient platform (124).

4. The apparatus of claim 3, wherein the second pair of opposing detectors is movable about an axis of rotation that is parallel to at least the patient platform.

5. 5. The apparatus of claim 4, wherein the first pair of opposing detectors and the second pair of opposing detectors are positioned such that a plane perpendicular to the patient platform intersects both the first pair of opposing detectors and the second pair of opposing detectors.

6. 6. The apparatus of claim 5, wherein the first pair of opposing detectors is positioned to cover the entire patient platform and is capable of tracking a position of a tracer within the entire body of the patient.

7. 6. The apparatus (110) of claim 5, comprising a first pair of opposing detectors (116) of a plurality of pairs positioned along the patient platform (124) and / or a second pair of opposing detectors (118) of a plurality of pairs positioned along the patient platform (124).

8. The apparatus (110) of claim 7, wherein each of the first pair of opposing detectors (116) is associated with a single second pair of opposing detectors (118).

9. 8. The apparatus of claim 7, wherein each of the first pair of opposing detectors is associated with a plurality of second pairs of opposing detectors, each first pair having a length that covers a portion of the patient platform corresponding to the plurality of second pairs of opposing detectors along the same plane.

10. The apparatus (110) of any one of claims 1 to 9, wherein the first pair of opposing detectors (116) and the second pair of opposing detectors (118) comprise positron emission tomography detectors.

11. The apparatus (110) according to any one of claims 1 to 10, further comprising an evaluation device (128) consisting of a calculation device (129), said evaluation device (128) being configured to determine said coarse location (121) according to step b) and to determine said fine location according to step e).

12. 12. The apparatus (110) of claim 11, further comprising a mechanical unit (130) configured to move in an axial (131) direction or in a horizontal (133) or vertical (140) transverse direction according to step c) to thereby position the second pair of opposing detectors (118).

13. 13. The apparatus (110) of claim 12, wherein the evaluation device (128) is further configured to provide the coarse position (121) to the mechanical unit (130) and to move the mechanical unit (130) in an axial (131) direction or in a horizontal (133) or vertical (140) transverse direction, thereby positioning the second pair of opposing detectors (118).

14. An apparatus (110) as described in claim 12 or claim 13, further comprising a first communications module (132) associated with the first pair of opposing detectors (116) configured to transmit the one or more first signals (120) to the evaluation device (128), and a second communications module (134) associated with the second pair of opposing detectors (118) configured to transmit the one or more second signals (122) to the evaluation device (128).

15. The apparatus (110) of claim 14, wherein the first communication module (132) is configured to operate via wired or wireless communication and / or the second communication module (134) is configured to operate via wired or wireless communication.

16. The apparatus (110) of any one of claims 1 to 15, comprising 2, 4, 8, 12, 16 or 20 pairs of first pairs of opposing detectors (116) and / or second pairs of opposing detectors (118).

17. A method for improved determination of the fine location of a tracer in a body part (112) of a patient (114), said tracer emitting radiation (123), said method being implemented by an apparatus (110) according to any one of claims 1 to 16, comprising the following steps: a) acquiring one or more first signals (120) acquired sequentially from a first pair of opposing detectors (116), the one or more first signals (120) including electromagnetic spectrum information corresponding to radiation (123) emitted by the tracer; b) determining a general location (121) of the tracer based on the one or more first signals (120); c) positioning a second pair of opposing detectors (118) based on the determined coarse position (121); d) acquiring one or more second signals (122) from the second pair of opposing detectors (118), the one or more second signals (122) comprising electromagnetic spectrum information corresponding to radiation (123) emitted by the tracer; e) determining a fine location of the tracer based on the one or more second signals (122); A method comprising:

18. 18. The method of claim 17, wherein in the positioning of step c), the second pair of opposing detectors (118) are positioned with respect to an axis of rotation (126) transverse to the general position (121) of the tracer such that the radiation (123) emitted by the tracer strikes the second pair of opposing detectors (118) perpendicular to a front face (135) of the second pair of opposing detectors (118).

19. The method of claim 18, further comprising associating two pairs of second detectors with positions of the tracer in at least two body parts (112) of the patient (114), said association comprising: - determining the fine location of the tracer in one body part (112) at a given time during the uptake period; determining the fine location of the tracer in another part of the body (112) at the same time during the uptake period; - measuring standard uptake values ​​at both sites during a predefined period and extracting a time correlation of uptake at both sites; 20. The method of claim 18, comprising:

20. 20. The method of claim 18, wherein the tracer comprises 18F-fluorodeoxyglucose (FDG).

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