A gamma probe for localization of sentinel lymph nodes

Abstract

The invention relates to a gamma probe for locating sentinel lymph nodes in nuclear medicine and surgical procedures, which, in addition to being capable of counting in proportion to the frequency of interaction with the gammas emitted from the radioactive material, is capable of angularly determining the location of the gammas emitted from the vicinity of the measurement region where the radiopharmaceutical used is involved, and thus the location of the involvement points.

Description

[0001] A GAMMA PROBE FOR LOCALIZATION OF SENTINEL LYMPH NODES

[0002] Technical Field of the Invention

[0003] The invention relates to a gamma probe for localizing sentinel lymph nodes where radiopharmaceutical involvement occurs in nuclear medicine and surgical procedures.

[0004] State of the art regarding the invention

[0005] Gamma probes are categorized into two main groups depending on their operating principle: semiconductor and scintillation-based. While semiconductor gamma probes offer good energy resolution, they operate with low efficiency in terms of detection sensitivity. On the other hand, scintillation-based gamma probes are relatively poor in energy resolution compared to semiconductor detectors but provide high detection efficiency. Scintillation detectors are more cost-effective and have higher sensitivity for various gamma energies than semiconductor detectors, and many commercial gamma probes are scintillation-based.

[0006] Scintillation-based gamma probes consist of a scintillator, photodetector coupled to the scintillator, data processing and acquisition electronics, collimator, and shielding components used in environmental radiation shielding. Since only the gammas reaching the scintillator from the limited region in front of the probe will interact with the scintillator by shielding the environmental radiation, the position of the probe front face is changed in the treated area, and the position where the involvement of the radiopharmaceutical occurs. To determine the location accurately, environmental radiation is prevented from reaching the scintillator located at the center of the probe, usually with shields made of lead or tungsten material due to its high gamma absorbition. Passive shielding made with these materials provides effective radiation shielding, and by ensuring the interaction of the scintillator with the gammas within the field of view (FOV) of the gamma probe, the counting process is carried out in proportion to the interaction statistics.

[0007] If there is a region where the radiopharmaceutical is involved in the area corresponding to the front face of the gamma probe, the involvement region is determined by considering the count number, as the gammas emitted from this region will give high count statistics. This feature of the gamma probe allows its use in the localization, marking, or biopsy of sentinel lymph nodes in breast cancer treatment. During surgical intervention, accurate localization of sentinel lymph nodes must be made, and this process must be carried out efficiently and quickly. In some cases, removing multiple sentinel lymph nodes requires a relatively large area to be scanned and localized with a gamma probe with a limited field of view, followed by surgical intervention. The narrow field of view of gamma probes makes this process difficult and requires careful scanning of the application area.

[0008] The patent with publication number EP1596223A1 describes a gamma probe design for detecting the position of radioactive sources and high-energy gammas. The gamma probe in this patent uses crystals of different principles, preferably CsI(Tl), Nal(Tl), LSO, CdTl, CZT, preferably CsI(Tl), Nal(Tl), LSO, CdTl, CZT, etc., arranged sequentially in various geometrical structures to determine the position of the gamma interaction within the detector array. The size of the crystals used in the detector and the spacing between them can be varied to optimize the performance of the detector array. The emission direction is determined by comparing the data from the crystals arranged in a row, the signals from the crystal where the signal is detected, and the crystals in its neighborhood (shadow detector). The method proposed here requires collecting, processing, and comparing many signals from array units. This requires complex signal-processing electronics consisting of many units.

[0009] The patent with publication number EP 2542916A1 describes a gamma probe that can perform counting and emission direction-finding functions together with a scintigraphic goniometric probe proposal. This gamma probe consists of a four-piece scintillator array scanning a cylindrical plane and a cylindrical scintillator in the center. The scintillator in the center is preferably selected from crystals that will provide relatively high light output, such as cerium-doped lanthanum bromide (LaBr3:Ce), thallium-doped sodium iodide Nal(Tl), thallium or sodium-doped cesium iodide (CsI(Tl), CsI(Na)). The four-part scintillators surrounding this scintillator are formed with either high atomic number bismuth germanate (BGO: Bi4Ge3O12 or Bil2GeO22) or cerium-doped lutetium oxyorthosilicate (LSO(Ce) Lu2SiO5:Ce) or cerium-doped lutetium yttrium orthosilicate (LYSO - Lu2(l-x)Y2xSiO5:Ce) crystals. When nested cylindrical structures are selected from different scintillators, they will produce characteristic signal output, and the signals received from photodetectors coupled to these scintillators will be structurally different. Thus, the signals from the central scintillator are used in the counting process. In contrast, the signals collected from the four outer scintillators determine the direction of the environmental radiation sources. There is no passive radiation shielding element in the proposed structure. The efficiency of this operation is highly dependent on the characteristic properties of the scintillation crystals. The lack of passive shields, such as lead and tungsten, which provide high radiation shielding, necessitates the selection of scintillators with high effective atomic numbers for the gamma probe.

[0010] Kolcu et al. proposed a gamma probe based on the principle of active shielding with trapezoidal (Kolcu, O.B., Yetkin, T. & Iren, E. "Development of active shielding gamma probe") nested five-part scintillators. In this model, all scintillators are selected BGO due to their high atomic number, and the signals received from the scintillators in the outer layer are compared with the signals received from the central scintillator, and active shielding is applied with the anti-coincidence algorithm. With this proposed structure, if the signals received from the center and peripheral scintillator are not simultaneous, counting is performed with the signals received from the scintillator in the center. The signals from the environmental scintillators are weighted to determine the direction of the radiation sources around the probe. In this model, there is no unit responsible for passive radiation shielding, and radiation shielding is applied by using simultaneous signals.

[0011] The patent with publication number US6643538B1 designed an intraoperative surgical probe sensitive to beta / gamma radiation. The front end of the probe is optically coupled to a CCD camera at the rear end of the probe via optical fibers located at the center of the probe. The direction of environmental radiation sources around the probe is determined by scintillators located around the fibers centrally positioned at the front end of the probe. Optical photons collected by optical fibers connected to the scintillators are transmitted to the CCD camera located at the back of the probe, aiming to provide visual information about the physical condition of the incision area without the surgeon having to move or change the probe's location. The relevant invention operates based on imaging.

[0012] The gamma probe described in patent numbered US20230161056A1 comprises scintillators with different fields of view placed in radiation shielding material at the front end and facing in different directions. This structure allows simultaneous detection of gammas emitted from radiation sources in different directions. In the invention, the field of view of scintillators placed with different curvatures enables scanning an area of more than 180° around the probe. In this system, the direction of environmental radiation sources can be determined within a limited angle.

[0013] As a result, all the abovementioned problems have made it necessary to improve in the relevant technical field.

[0014] Objects and Brief Description of the Invention

[0015] The main object of the present invention is to provide a gamma probe structure to accelerate the location detection of radiopharmaceuticals injected into the body in nuclear medicine and surgical procedures and involvement in the sentinel lymph nodes around the tumoral area.

[0016] The object of the present invention is to increase the accuracy rate in the localization of lymph nodes and to make the localization process easier and faster.

[0017] Another object of the present invention is to determine the direction of environmental radiation sources while performing counting-based location determination.

[0018] The present invention relates to constructing a gamma probe with a unique structure capable of counting and emission direction finding (the direction of environmental radiation sources relative to the gamma probe) in two different operating arrangements. Thus, depending on the number of counts at the measurement point, the sentinel lymph node can be localized, and the direction of the following measurement point can be determined. Including these functions together will speed up and facilitate the localization process.

[0019] In this context, instead of the single scintillator located at the end of the gamma probe and the passive shielding surrounding the lateral region of the gamma probe in conventional gamma probes, the central scintillator responsible for the counting process, a passive shielding mesh around this scintillator to surround the scintillator, and scintillators (peripheral scintillators) in a spaced array in the outermost layer are positioned. The peripheral scintillators in the outer layer, together with the shielding mesh, provide additional contribution to the radiation shielding of the central scintillator and are used to find the direction of the peripheral radiation.

[0020] Preferably, the direction of the radioactive sources around the probe center axis is found in angles by weighting the signals collected from the environmental scintillators in the outer layer to find the direction of the environmental radiation. Preferably, two separate processing units carry out the counting and finding the direction of radioactive sources. The gamma probe created with this structure can simultaneously use two different operating modes. The first one is to accurately localize the radiation source using only the count information obtained from the interactions recorded in the central scintillator, which benefits from high shielding. The second one is to determine the direction of the peripheral radiation source, specifically the next sentinel lymph node to be treated, by weighing the signals obtained from the scintillator array in the outer layer of the probe.

[0021] Furthermore, in one embodiment of the present invention, by means of shielding mesh parts between the peripheral scintillators, the passage of radiation between these scintillators is limited. Accordingly, one scintillator is not affected by gamma rays incident on the other scintillator, and the accuracy rate is increased by preventing possible incorrect direction determinations.

[0022] Definitions of the Figures Describing the Invention

[0023] The figures and related explanations used to explain better the device developed with the present invention are given below.

[0024] Figure 1. Isometric view of the gamma probe.

[0025] Figure la. A transparent, detailed view of the probe head and housing is in Figure 1.

[0026] Figure 2. Upper isometric view of the probe head.

[0027] Figure 2a. Bottom isometric view of the probe head.

[0028] Figure 2b. Side view of the probe head.

[0029] Figure 2c. Top view of the probe head.

[0030] Definitions of Elements / Sections / Parts that Constitute the Invention

[0031] The parts and parts in the figures are enumerated, and the corresponding number is given below to better explain the device developed with this invention:

[0032] 1. End portion

[0033] 2. Handle portion 10. Probe head

[0034] 11. Central scintillator

[0035] 12. Peripheral scintillator

[0036] 13. Photodetector

[0037] 14. Collimator

[0038] 15. Collimator aperture

[0039] 16. Shielding mesh

[0040] 20. Housing

[0041] A. Gamma probe

[0042] FOV. Field of view

[0043] Detailed Description of the Invention

[0044] The present invention relates to a gamma probe for localizing sentinel lymph nodes where radiopharmaceutical involvement occurs in nuclear medicine and surgical procedures.

[0045] With reference to FIGS. 1 and la, said gamma probe (A) comprises an end portion (1) and a handle portion (2), wherein said gamma probe (10) comprises a probe head (10) at its tip, wherein gamma interactions take place, and a housing (20) made of a material preferably having minimal interaction with gammas, which surrounds said probe head (10). Preferably, said gamma probe (A) is arranged in portable sizes.

[0046] With reference to Figure 2-2c, said probe head (10) consists of a central scintillator (11), peripheral scintillators (12), photodetectors (13) connected to the central scintillator (11), and peripheral scintillators (12), collimator (14), collimator aperture (15) and shielding mesh (16).

[0047] Said probe head (10) comprises a central scintillator (11). The central scintillator (11) is used to localize the lymph node where radiopharmaceutical involvement occurs. Here, the central scintillator (11) generates optical photons by scintillation as a result of interaction with the gammas emitted from the radioactive source in the front region of the probe head (10), and the photodetector (13) to which it is connected generates an electrical response to the visible light it detects. The signals collected by photodetectors (13) are used to obtain counts proportional to the frequency of interaction, and the position of the radiation source (lymph node) is thus determined on a non-imaging basis according to the counts obtained.

[0048] The outer layer of the probe head (10) is preferably provided with evenly spaced peripheral scintillators (12). In a preferred embodiment, a shielding mesh (16) having a radiationisolating mesh structure surrounding the central scintillator (11) and between the peripheral scintillators (12), preferably eight peripheral scintillators (12) disposed of in the cavities of the shielding mesh (16). Each peripheral scintillator (12) is connected to photodetectors (13). Peripheral scintillators (12) are positioned in the lateral regions of the probe head (10) to interact with gammas from radiation sources around the gamma probe (A). The collimator (14) on the front face of the probe head (10), preferably made of lead or tungsten material, ensures that the peripheral scintillators (12) do not interact with the radioactive sources in the front region of the probe head (10). Thus, the peripheral scintillators (12) are only open to interaction with radiation sources located around the probe head (10). Therefore, peripheral scintillators (12) are used to find the direction of the lymph nodes located around the gamma probe (A), which act as point radiation sources.

[0049] The probe head (10) comprises two parts responsible for radiation shielding, a collimator (14) and a shielding mesh (16), preferably made of lead or tungsten, used in radiation shielding.

[0050] The collimator (14) has a collimator aperture (15) having a diameter equal to the width of the central scintillator (11). The collimator (14) prevents or limits the interaction of the peripheral scintillators (12) with the gammas from the front face of the probe head (10). In contrast, the collimator aperture (15) serves the function of sensitizing only the central scintillator (11) to the gammas from the front face of the probe head (10). The field of view (FOV) of the central scintillator (11) can be changed, and spatial resolution gain can be achieved by changing the diameter of the collimator aperture (15). The collimator (14) is arranged with sufficient thickness and material selection.

[0051] The shielding mesh (16) functions in the radiation shielding of the central scintillator (11) against gammas incident in the direction of the probe head (10) lateral region. In addition, the mesh structure extending between the peripheral scintillators (12) prevents or limits the gamma transmission between the peripheral scintillators (12). Said mesh structure refers to a structure in which at least two plates parallel to each other are intersected by multiple intersections of plates positioned perpendicular to each other with respect to these plates. In response to gamma interactions in peripheral scintillators (12), photodetectors convert scintillation-generated optical photons into processable signals (13). Since these signals will be dominant in the region where the radioactive source is located, the direction of the point radioactive source around the probe head (10) is determined by weighting the signals received from each photodetector (13) coupled to the peripheral scintillators (12).

[0052] Preferably, the central scintillator (11) and / or the peripheral scintillators (12) are of a non- hygroscopic type, in particular of the GAGG(Ce) type. GAGG(Ce) refers to scintillators with Ce-doped Gadolinium Aluminium Gallium Garnet (Gd3A12Ga30i2) crystal. GAGG(Ce) is advantageous because it is non-hygroscopic and does not undergo internal radiation.

[0053] The photodetectors (13) can be silicon photomultipliers (SiPM) or photomultiplier tubes (PMT) coupled individually to each scintillator, or a silicon photomultiplier array or a position-sensitive photomultiplier tube, depending on the number and size of the scintillators. In the case of array photodetectors (13), this array structure can simultaneously connect to all scintillators.

[0054] The present gamma probe (A) further comprises a processing unit (not shown in the figures) having at least one processing unit. The processing unit contains a processing unit or units configured to detect the electrical response of photodetectors (13), the localization of lymph nodes, and the direction of radioactive sources in the environment.

[0055] The processing unit obtains counting information to localize sentinel lymph nodes. The processing unit is configured to count the pulses generated by the photodetectors (13) based on the gamma rays collected by the central scintillator (11).

[0056] The processing unit is also used to obtain the directional information of the radioactive source. Here, the processing unit is configured to determine the signal amplitudes generated by the photodetectors (13) based on the gamma rays collected by the peripheral scintillators

[0057] (12) and to determine the direction of incidence of the gammas based on these amplitudes. The amplitudes are proportional to the amount of optical photons generated by scintillation and detected in the photodetectors (13). Here, the processing unit is configured to apply a center of gravity (COG) weighting method to the signals collected from all photodetectors

[0058] (13).

Claims

CLAIMS1. A gamma probe (A) for localization of sentinel lymph nodes, characterized in that it comprises the following;A central scintillator (11) that interacts with gamma rays emitted from the involved lymph nodes after injection of a radiopharmaceutical to generate optical photons as a result of scintillation, and a photodetector (13) coupled to the central scintillator (11) for detection of said photons,Peripheral scintillators (12) arranged on the outer layer of the probe head (10) and used to determine the direction of the radiation sources (lymph node) around the gamma probe (A) and photodetectors (13) coupled to each of these scintillators,Shielding mesh (16) surrounding the central scintillator (11) and extending between the peripheral scintillators (12) arranged in an array,Collimator (14) with collimator aperture (15) corresponding to the front face of the central scintillator (11) and a thickness and material to prevent the interaction of the peripheral scintillators (12) with the gammas coming from said front face,Processing unit with at least one processing unit configured to count the pulses generated by the photodetectors (13) in response to the optical photons generated in said central scintillator (11) and to be used in the localization of the radioactive source and to determine the direction of the radioactive source according to the signals generated by the photodetectors (13) in response to the optical photons generated in said peripheral scintillators (12).

2. A gamma probe (A), according to claim 1, is characterized in that it comprises a shielding mesh (16) with radiation shielding extending between the central scintillator (11) and the peripheral scintillators (12).

3. A gamma probe (A), according to claim 2, is characterized in that said shielding mesh (16) is in grid form.

4. A gamma probe (A), according to any of the preceding claims, is characterized in that said central scintillator (11) is positioned at the center of the array formed by the peripheral scintillators (12).

5. A gamma probe (A), according to claims 1 or 4, is characterized in that said peripheral scintillators (12) are identical scintillators arranged at equal intervals.

6. A gamma probe (A) according to claim 1 , characterized in that, said processing unit comprises a processing unit configured to count pulses and another processing unit configured to determine the direction of the radioactive source based on signal amplitudes.

7. A gamma probe (A) according to claim 1 or claim 6, characterized in that, the processing unit is a discrete positioning circuit configured to determine the radioactive source direction according to signal amplitudes.

8. A gamma probe (A) according to any one of claims 1, 6, 7, characterized in that, said processing unit is configured to determine the radioactive source direction by applying signal weighting.

9. A gamma probe (A) according to claim 1, characterized in that, said scintillators are of GAGG(Ce) type.

10. A gamma probe (A) according to claim 1, characterized in that, said photodetector (13) is a silicon photomultiplier.

11. A gamma probe (A), according to claim 1, is characterized in that said photodetectors (13) are photomultiplier tubes.

12. A gamma probe (A), according to claim 1, is characterized in that said photodetectors (13) are position-sensitive photomultiplier tubes.

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