Patent Publication Number: US-2023161056-A1

Title: Directional gamma detector

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is the U.S. national phase of International Application No. PCT/IB2021/052428 filed Mar. 24, 2021 which designated the U.S. and claims priority to IT 102020000007978 filed Apr. 15, 2020, the entire contents of each of which are hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     This invention relates to a directional gamma detector which can be widely applied in the field of radio-guided surgery (intraoperative and laparoscopic) for locating lymph nodes and tumors and/or other diseases. 
     Description of the Related Art 
     As is known, gamma detectors are instruments used to locate tumor cells or specific diseased parts in a patient by picking up the radiation emitted by a radiopharmaceutical previously administered to the patient and which tends to concentrate in the diseased cells. 
     Generally speaking, gamma detectors comprise a detection head equipped with a single crystal or a plurality of crystals suitably oriented and configured to absorb the gamma rays emitted by the radiopharmaceutical. The prior art scintigraphic detection devices also comprise a rod configured to receive at one end the detection head and at a further end a handgrip configured for suitably directing the detection head during the medical application. In the prior art gamma detection devices, the handgrip usually contains all the control electronics configured for converting the data coming from the detection head and for transmitting it to a processing system in such a way as to be subsequently displayed by an operator. 
     In more detail, there are currently prior art detectors with a large range of action also known as “goniometric detectors” comprising a first detection element which is hollow and tubular in shape and which is divided into at least three sectors, each consisting of a scintillation crystal, and a second detection element consisting of a scintillation crystal housed inside the tubular structure of the first detection element. 
     In other words, the detectors with a large range of action have a detection head divided into a central part, configured to impart an axial directionality, and a series of angular sectors which are able to indicate the directionality of the radiation. The directionality of the radiation is obtained by making the above-mentioned crystals using materials having different optical properties. 
     As is known, the detectors with a large range, thanks to this arrangement of the crystals, can analyze zones not facing directly the front surface of the detector, allowing the identification of lymph nodes and tumors even delocalized with respect to the front portion of the instrument. The detectors with a large range are not, however, provided with structures for collimation of the gamma rays incident on the crystals and they therefore have a low spatial resolution to identify the tumor or more generically the part of the patient affected by the disease. 
     Gamma probes are also known which are equipped with a detection head made of a material with a high atomic number and having a plurality of detection elements, each comprising a scintillation crystal. These crystals are distinct from each other and aligned according to respective different collimation axes for simultaneously detecting gamma radiation directed in different directions. Each detection element is associated with a collimator made of a material with a high atomic number and designed to block the gamma rays incident upon the detection element at a predetermined external solid angle. Usually, these detectors have an axial collimator and at least two lateral collimators, inclined relative to the axial collimator in such a way that the central crystal acts as a true and proper detector whilst the lateral crystals act as direction sensors to indicate to the operator where to direct the instrument during the medical analysis. 
     Disadvantageously, the above-mentioned types of scintigraphic detectors have drawbacks linked in particular to their precision and their cost. 
     The detectors with a large range of action, as they are free of collimators, have low spatial resolutions which make these detectors not very reliable and not very precise. Moreover, these detection devices are large in size due to the tubular configuration of the crystals which do not adapt well to the miniaturization characteristics required by the current detection instruments. 
     One disadvantage of the detectors with a head made of a material with a high atomic number is that the dimensions of the detection head crystals are equivalent to each other but, since they have a different orientation within the detection head itself, they have different solid angles of view. 
     In other words, even though the scintillator crystals have the same size, they are able to absorb gamma rays according to different angles of view since they are positioned on the detection head at different angles from each other. More specifically, the lateral scintillator crystals have a visible angle greater than that of the scintillator crystal positioned coaxially to the detector. This results in an analysis which basically favors the detection of the lateral crystals which have a greater angular opening but for this reduced collimation, thus obtaining an imprecise detection. 
     A further disadvantage derives from the fact that the lateral crystals, which are inclined relative to the central crystal, due to the respective collimator, have detection angles which are insufficient in size to carry out an angular detection over a large area, thus adversely affecting the detection speed which requires a greater skill of the operator or implies a greater number of maneuvers carried out by the operator to determine the correct position of the central crystal aligned with the source of emission. 
     In other words, only the rays whose angle is within the size of the angle of view delimited by a crystal are actually detected; all the other rays, on the other hand, fall in a blind zone in which they are not detected. Since the solid angles described by prior art scintillator crystals do not intersect each other, certain rays will have directions such as to fall into the space between two solid angles and will not therefore be analyzed, thus reducing the detection speed. 
     More generally speaking, prior art detectors do not have geometries and arrangements of the detection elements which are favorable to a precise and rapid analysis of the part of the patient affected by the disease. 
     A further disadvantage derives from the fact that both of the detection configurations described above have a poor operational flexibility, since their application is limited to the specific use and, in the case of different uses, it is necessary to provide additional instruments with a considerable increase in costs. Consider, for example, investigations using rectilinear probes, investigations which require the use of angular detection heads or laparoscopic investigations. In these situations, the operator must have different probes each designed for the respective use, with obvious increases in costs. In fact, it is known that the greatest incidence of cost in these probes is the complex electronic control circuitry configured for converting the data coming from the detection head and for transmitting it to the processing system. 
     SUMMARY OF THE INVENTION 
     The technical purpose of the invention is therefore to provide a directional gamma detector which is able to overcome the drawbacks of the prior art. 
     The aim of the invention is to provide a directional gamma detector which is extremely precise and reliable. 
     A further aim of the invention is to provide a directional gamma detector having a limited cost. 
     A further aim of the invention is to provide a directional gamma detector which is extremely versatile in use. 
     A further aim of the invention is to provide a directional gamma detector having a particular production geometry which is able to speed up the localization of the tumor or, more generally, of the lesion. 
     The technical purpose indicated and the aims specified are substantially achieved by a directional gamma detector comprising the technical features described in one or more of the appended claims. More specifically, the technical purpose is achieved by a directional gamma detector comprising a detection probe and a handgrip, where the detection probe comprises a supporting rod and a detection head coupled or integrated with a first end (distal) of the supporting rod and a plurality of detection elements distinct from each other for simultaneously detecting gamma rays directed in different directions to each other. Each detection element comprises at least one scintillation crystal and a corresponding first electronic conversion circuitry to receive an optical signal from the crystal and convert it into an electrical signal, each of the detection elements is associated with a respective collimator made of a material with a high atomic number and suitable for screening the gamma rays incident upon the detection element with a predetermined external angle and a solid angle, the handgrip can be manually gripped by an operator and is equipped internally with a second electronic circuitry for converting the signals. 
     The detector according to the invention is characterized in that detection probe, and in particular a second end (proximal) of the supporting rod, is reversibly connectable to the handgrip by means of a mechanical connector equipped with electrical contacts for transferring the signals from the first electronic conversion circuitry to the second electronic conversion circuitry. 
     Preferably, the mechanical connector is a bayonet coupling, a quick coupling, a snap-on coupling or a threaded connection or threaded ring nut. 
     Preferably, the handgrip has a transversal dimension greater than that of the supporting rod and even more preferably between the handgrip and the supporting rod there is a variation of transversal cross-section on which the mechanical connector is positioned. 
     Advantageously, thanks to the mechanical connector, the handgrip is a shared component applicable to each detection probe, quickly and easily, as a function of the specific use necessary each time. 
     Advantageously, the costs relative to the detector are considerably reduced since a single handgrip is necessary (which is usually the most costly part of the entire detector since it contains the majority of the operating electronics) to operate with different detection probes. 
     Further features and advantages of the invention are more apparent in the non-limiting description which follows of a non-exclusive embodiment of a directional gamma detector. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The description is set out below with reference to the accompanying drawings which are provided solely for purposes of illustration without restricting the scope of the invention and in which: 
         FIGS.  1 A and  1 B  show, respectively, an exploded view and an operating configuration view of a directional gamma detector according to the invention; 
         FIG.  2    shows a perspective view of a portion of the directional gamma detector according to the invention in an alternative embodiment; 
         FIGS.  3 A and  3 B  show respective embodiments of a cross-section according to a longitudinal plane of the portion of the directional gamma detector of  FIG.  2   ; 
         FIG.  4    shows a front view of a kit for configuring a directional gamma detector according to the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the accompanying drawings, the “R” denotes a directional gamma detector according to the invention, according to a first embodiment. 
     As shown in  FIG.  1 A , the detector “R” comprises a detection probe “S” and a handgrip “I”, aligned along a main axis of extension “A” of the detector “R”. 
     The detection probe “S” comprises a supporting rod  10 , extending along the main axis of extension “A” of the detector “R”, and a detection head  20  coupled or integrated with a first end  10   a  of the supporting rod  10 . 
     Advantageously, according to the invention, the handgrip “I” is reversibly connectable to the detection probe “S” by a mechanical connector  12 , as described in detail below, in such a way as to obtain a detector “R” made of at least two functionally different components and which can be physically separated from each other as shown in  FIG.  1 B . 
     The detection probe “S” comprises a supporting rod  10  and a detection head  20  coupled or integrated with a first end  10   a  of the supporting rod  10 . 
     According to the embodiment of  FIG.  2   , the supporting head  20  is of the type removably connectable to the supporting rod  10  by means of a further mechanical connector  12  (for example of the same configuration and/or size as that defining the connection between the supporting rod  10  and the handgrip “I”). However, according to an alternative embodiment, the supporting head  20  is integrated with the supporting rod  10 , that is to say, made as one piece. 
     As shown in detail in  FIG.  2   , the supporting head  20  is made in the form of a solid body having a cylindrical shape preferably extending along the main axis of extension “A”. The term “solid body” is used to mean a block made of a single material. In the preferred embodiment, the detection head  20  is made of a material with a high atomic number, for example lead, designed to absorb and screen the gamma rays emitted by a radiopharmaceutical. 
     The solid body comprises a plurality of detection elements  21   a,    21   b  distinct from each other for simultaneously detecting gamma rays directed along respective directions different to each other. In the embodiment shown in the accompanying drawings, the detection head  20  comprises a central detection element  21   a  aligned with a main collimation axis “X”, preferably parallel or coaxial with the main direction of extension “A” of the supporting rod  10 , and a pair of lateral detection elements  21   b  aligned along respective collimation directions “Y” transversal to the main collimation axis “X” and preferably diverging away from the handgrip “I”. 
     Preferably, the collimation directions “Y” transversal to the main axis of collimation “X” lie in a plane of symmetry “I” of the detection head  20  passing through the central collimation axis “X” ( FIG.  2   ). 
     Even more preferably, the transversal collimation directions “Y” are inclined at an angle of between 20° and 90° relative to the main axis of collimation “X”, this angle being measured in the above-mentioned plane of symmetry “I”. 
     As shown in  FIG.  2   , the lateral detection elements  21   b  are opposite each other, diametrically opposite the central detection element  21   a  and lie at the same height on the detection head  20 . In other words, the lateral detection elements  21   b  are positioned symmetrically about a longitudinal plane passing through the above-mentioned main direction of extension “A” of the supporting rod  10  and/or through the main axis of collimation “X”. 
     Alternatively, the lateral detection elements  21   b  are opposite each other, diametrically opposite the central detection element  21   a  and lie at different heights on the detection head  20 , that is to say, in such a way as to be axially offset. 
     Preferably, the lateral detection elements  21   b  are shaped and/or positioned in such a way that at least a part of the central detection element  21   a,  and in particular at least the rear part, is in a region of the detection head  20  positioned radially between the lateral detection elements  21   b  and/or between the respective channels in which the lateral detection elements  21   b  are positioned. In other words, the lateral detection elements  21   b  and/or the channels in which they are housed enclose laterally and at least partly the central detection element  21   a,  in particular at least the rear of the latter (in particular thanks to the divergent shape “forwards” of the axes “Y” of the lateral detection elements  21   b.  In this configuration, shown in  FIGS.  3 A to  3 B , a particular compactness of the detection head  20  is obtained in an axial direction. 
     In another possible embodiment not illustrated, the detection head  20  comprises a single central detection element  21   a  and a plurality of lateral detection elements  21   b  aligned along respective collimation directions “Y” transversal to the main collimation axis “X” and angularly positioned at predetermined angular distances around the central detection element  21   a.    
     As shown in  FIGS.  3 A and  3 B , each detection element  21   a,    21   b  comprises at least one scintillation crystal  22  and a corresponding first electronic conversion electronics (not illustrated) for receiving an optical signal from the scintillation crystal  22  and converting it into an electric signal. Preferably, the scintillation crystals  22  are sensitive to gamma rays of strength between 30 keV and 1 MeV, which emit light at peak wavelength as a function of their composition in a range from 300 nm-600 nm. 
     With reference to the embodiment shown in the accompanying drawings, each detection element  21   a,    21   b  is also associated with a respective collimator  24 . 
     Preferably, each collimator  24  is made in the form of a blind channel, made in the material of the detection head  20 , on the bottom of which the respective scintillation crystal  22  lies in such a way that a portion of the lateral wall of the channel, included between the crystal  22  and the outer opening of the channel, defines a solid detection angle a, b, and therefore determines the collimation of the radiation directed towards the crystal  22 . 
     Still more preferably, each collimator  24  is made of a material with a high atomic number and is therefore suitable for blocking the gamma rays incident upon the detection element  21   a,    21   b  with an external solid angle a, b, defined by the respective collimator  24 . In this way, only gamma radiation having an angle inside the solid detection angle a, b, can be actually absorbed by the scintillation crystal  22  and converted, by the first electronic converter circuitry, into an electrical signal. 
     According to variant embodiments, the collimators  24  can be made in the form of inserts applied to a load-bearing structure defining the detection head  20 . 
     The amplitudes of the solid detection angles a, b may vary depending on the positioning of the scintillation crystal  22  inside the collimator  24 . More specifically, the opening of the solid detecting angles a, b decreases the more the scintillation crystal  22  is inserted deep in the collimator  24 . 
     In the preferred embodiment, the scintillation crystal  22  of the central detection element  21   a  is inserted in the respective collimator  24  at a position behind the outlet point of the collimator  24 , while the lateral detection elements  21   b  are inserted close to an outlet point of the respective collimators  24 . 
     As shown in  FIGS.  3 A and  3 B , the solid angle a relative to the central detection element  21   a  has a greater or lesser amplitude (measured in the plane of symmetry “I”) depending on how much the scintillation crystal  22  is inserted in the collimator  24 . In  FIG.  3 B , the scintillation crystal  22  is inserted further in depth than the scintillation crystal  22  shown in  FIG.  3 A  and therefore the solid detection angle a associated with it has a smaller opening than that shown in  FIG.  3 A . Consequently, the radiation is more focused, that is to say, the spatial resolution associated with the central detection element  21   a  is greater than that associated with the central detection element  21   a  shown in  FIG.  3 A . 
     The scintillation crystals  22  associated with the lateral detection elements  21   b  are, on the other hand, inserted in the respective collimators  24  in such a way as to be preferably flush with an outer lateral surface of the detection head  20 . 
     In other words, the scintillation crystals  22  associated with the lateral detection elements  21   b  have a flush edge of the outer surface of the detection head  20  and have a flat front surface inclined forwards from the edge. In this configuration, thanks to the flush wall arrangement of the scintillation crystals  22 , the solid angle b, described by them starts from a generatrix of the outer wall as shown in  FIGS.  3 A and  3 B . In this way, the detection elements  21   a,    21   b  define respective solid detection angles a, b, g which do not overlap at least within a distance of between 1 and 7 cm from a front surface of the detection head  20 . 
     Advantageously, the above-mentioned arrangement of the scintillation crystals  22  inserted in the collimators  24  makes it possible to increase the precision and reliability of the detector “R” reducing the blind detection zones “W”, that is to say, those zones not included in any solid detection angle a, b, g. 
     Advantageously, this arrangement of the detection elements  21   a,    21   b  makes it possible to increase the size of the investigation zone while maintaining the miniaturized dimensions of the detection head  20 . 
     Advantageously, this arrangement of the scintillation crystals  22  makes it possible to obtain a detector “R” which is able to speed up the localization of the part of the patient affected by the tumor or disease since the lateral detection elements  21   b  form a solid detecting angle b, g which is large and suitable to act as a “directionality sensor” for the directing of the detector “R”, whilst the central detection element  21   a  defines a solid detection angle a designed to act as an actual detector. In other words, the lateral detection elements  21   b,  defining a larger solid detecting angle b, probe a large area of analysis with a smaller spatial resolution so as to indicate from where the majority of gamma radiation comes. The central detection element  21   a,  on the other hand, defining a smaller solid detecting angle a, has a better spatial resolution and is therefore directed on the basis of the information deriving from the lateral detection elements  21   b  in such a way as to perform the actual detection operation. 
     In order to further increase the precision and speed of identifying the zone affected by tumor cells (or by specific pathologies), the central detection element  21   a  has a larger volume than each of the lateral detection elements  21   b  and an angular opening which is less than each of the lateral detection elements  21   b,  as mentioned above. Preferably, the solid detection angle a, defined by the central detection element  21   a  has an amplitude, measured in the plane of symmetry “I” of the detection head  20 , of between 30° and 65°. 
     Preferably, the solid detection angle b, defined by the lateral detection elements  21   b,  has an amplitude, measured in the above-mentioned plane of symmetry “I”, greater than 90°. 
     Thanks to these geometrical and structural characteristics, the central detection element  21   a  has a greater focusing of the gamma radiation and therefore a greater spatial resolution, whilst the lateral detection elements  21   b  act as directionality sensors of the detector “R” since they have a low spatial resolution but a large detection angle and therefore a wide field of analysis. 
     In other words, the opening of the solid angle a of the central detection element  21   a  allows the latter to focus more closely the incident gamma radiation increasing the resolution of the detector “R” whilst the opening of the solid angle b, g described by the lateral detection elements  21   b  also allows the lateral zones to be scanned relative to that covered by the central detection element  21   a  in such a way as to allow immediate identification of the high radiation emission zones and hence affected by tumorous diseases. 
     Advantageously, the volumetric size of the detection elements  21   a,    21   b  and their position makes it possible to extend the entire investigation zone, that is to say, increasing the solid detecting angles a, b, g but at the same time allows miniaturized dimensions of the entire detection probe “S” to be maintained. This is particularly advantageous in the case of laparoscopic probes “S 3 ”, “S 4 ”, that is to say, probes which must be inserted in trocars. 
     Advantageously, the ratio between the dimensions of the detection elements  21   a,    21   b  and the respective solid detecting angles a, b makes it possible to perform a reliable and precise analysis. In particular, the detection probe “S” has a geometry allowing only one or a maximum of two detection elements  21   a,    21   b  on three to be involved simultaneously in a scintigraphy detection operation in such a way that it can be clearly understood towards which direction it is necessary to orient the detector “R” to identify the positioning of tumor. In fact, the third detection element  21   b,  especially in the presence of a single source of gamma radiation, that is to say, in the presence of a single tumor, only registers background events which have no contribution in locating the tumor and do not therefor influence the effectiveness of the analysis. 
     According to alternative embodiments, not illustrated, the scintillation crystals  22  associated with the lateral detection elements  21   b  are positioned further behind the above-mentioned flush position, however preferably defining respective solid detecting angles b, g which are greater than the solid detecting angle a of the scintillation crystal  22  associated with the central detection element  21   a.    
     The orientation of the detection probe “S”, and hence the detection head  20 , during the medical analysis is performed manually by an operator who directs the detection probe “S” by means of the handgrip “I”. The handgrip “I” has a transversal dimension greater than the transversal dimension of the supporting rod  10  and it is equipped internally with a second electronics circuitry for converting the signals (not illustrated) configured for converting the analogue signals deriving from the first electronic converter circuitry into digital signals and, if necessary, for performing a first processing of these signals. 
     As shown in  FIGS.  1 A and  1 B , the handgrip “I” is reversibly connectable to the detection probe “S”, and in particular to a second end  10   b  of the supporting rod  10 , by means of a mechanical connector  12  equipped with electrical contacts in such a way that the signals, coming from the first electronic conversion electronics of the scintillation crystals  22 , are transferred to the second electronic conversion electronics. 
     Preferably, the mechanical connector  12  is positioned at a variation of transversal cross-section between the handgrip “I” and the supporting rod  10  in such a way that the second end  10   b  of the supporting rod  10  can be inserted inside the handgrip “I” and locked by the interaction of the mechanical connector  12  with the handgrip “I”. 
     In the preferred embodiment illustrated in the accompanying drawings, the mechanical connector  12  is made in the form of a bayonet coupling. 
     According to different embodiments, the mechanical connector  12  may be made in the form of a quick coupling, a Snap-On coupling, a threaded connection or a threaded ring nut. 
     Advantageously, thanks to the mechanical connector  12  it is possible to connect a plurality of different detection probes “S” to the handgrip “I” in a quick and easy manner. 
     Moreover, the possibility of connecting and removing the handgrip “I” from the supporting rod  10  considerably reduces the costs relative to the entire detector “R” since it is not necessary to have a handgrip “I” for each detection probe “S” but it is sufficient to have a single handgrip “I” connectable to several detection probes “S” having the mechanical connector  12 . 
     According to another aspect of the invention, in accordance with the embodiment of  FIG.  2   , the detection head  20  may also be associated with the first end  10   a  of the supporting rod  10  by means of a mechanical connector  12  equipped with electrical contacts for transferring the signal from the first conversion electronics to at least one electrical conductor inside the supporting rod  10 . 
     In other words, the detection head  20  can be reversibly coupled to the first end  10   a  of the supporting rod  10  in such a way that several different detection heads  20  can be applied to the end  10   a  of a same supporting rod  10 . This aspect is particularly advantageous in the case of laparoscopic probes “S 4 ” which may have telescopic extensions at the second end  10   b  of the supporting rod  10 , which are elongated or retracted according to the medical requirements or to replace the supporting rod  10  with another of different length. 
     Preferably, as described above, the mechanical connector  12  reversibly connecting the detection head  20  to the supporting rod  10  is identical to the mechanical connector  12  defining the connection between the supporting rod  10  and the handgrip “I”. 
     The detector “R” also comprises a control unit  30  connected to the second conversion electronics and capable of controlling the detection elements  21   a,    21   b  independently so that some of them can be switched on while the others are switched off. 
     In other words, by means of the control unit  30 , the individual detection elements  21   a,    21   b  can be used individually independently so as to have the possibility of working with solid detecting angles a, b, g according to the requirements. 
     Preferably, the control unit  30  is connected to the second electronic conversion circuitry of the handgrip “I” by Wi-Fi, Bluetooth or via cable in such a way that the signals are transmitted from the second electronic converter to the control unit  30 . 
     As shown in  FIG.  1 B , the control unit  30  comprises a monitor, which shows to the operator the processing of the signals coming from the detector “R” and the count parameters recorded, in particular by providing a graphical image representing in a graphical and easily legible manner the data contained in these signals. 
     Preferably, the control unit  30  also comprises, integrated thereto, a sound signaling device (not illustrated) configured to emit an acoustic signal which is directional or at a different intensity/frequency according to the detection element  21   a,    21   b  most affected by the radiation at a given instant. 
     Alternatively, or in addition to the sound signaling device, the control unit  30  also comprises a visual signaling device, for example a flashing LED, configured to emit a visual signal according to the detection element  21   a,    21   b  struck most by the radiation at a given instant. 
     The control unit  30 , following processing of the signals from the detector “R”, thus informs the operator about the direction of greatest origin of the gamma radiation and hence about the direction in which the detector “R” and, more specifically, the central detection element  21   a,  should be positioned. 
     The use of the monitor together with acoustic and/or visual signals thus constitutes a “navigation system” inside a cavity of the patient since the operator can easily direct the detector “R” in the direction of greatest flow of gamma radiation thus tracing the part of the patient affected by the presence of the disease. 
     Advantageously, using the control unit  30 , locating the area affected by the presence of tumor cells or other specific diseases is simple, precise and fast. 
     In use, therefore, gamma radiation having different directions strikes the detection head  20  but only the radiations having directions inside the solid angles a, b, g, defined by the detection elements  21   a,    21   b  are effectively absorbed and converted into electrical signals by the first conversion electronics. These electrical signals are transmitted to the second electronic conversion circuitry contained in the handgrip “I” in such a way as to be transformed into digital signals. Subsequently, the signals are sent to the control unit  30  which analyses them, processes and displays them on a monitor in such a way as to provide a directing of the detector “R”. Since the position of the detection elements  21   a,    21   b  are correlated with each other, it is therefore possible, given the measured intensity of radiation, to provide the direction in which to direct the detector “R” by means of the handgrip “I”. 
     If most of the activity is detected by a transversal detection element  21   b,  on the right or left relative to the axial direction, then the signal to orient the detector “R” is provided by the luminous or audio signaling device of the control unit  30  which indicates the direction in which to orient the central detection element  21   a.    
     According to another aspect of the invention, the directional gamma detector “R”, as described above, can be assembled starting from a kit “K” designed to allow a plurality of different configurations. 
     As shown in  FIG.  4   , the kit “K” comprises a single handgrip “I” and a plurality of detection probes “S”, each selectively connectable to the handgrip “I” using the mechanical connector  12 . In detail, the plurality of detection probes “S” comprises at least one longitudinal probe “S 2 ” (that is to say, a probe with a main collimator coaxial with the longitudinal axis of extension of the probe), an angular probe “S 1 ” (that is to say, a probe with a main collimator which is inclined at an acute angle to the longitudinal axis of extension of the probe) and a laparoscopic probe “S 3 ”, “S 4 ”. Each of these probes may be provided at the second end  10   b  of the supporting rod  10  of the mechanical connector  12  or be integrated with the respective detection head  20 . 
     Preferably, at least the laparoscopic probe “S 4 ” has the detection head  20  removably connected or connectable to the respective supporting rod  10  by means of the further mechanical connector  12 . Advantageously, the mechanical connector  12  of the handgrip “I” acts as a “universal connection” in such a way that a plurality of different supporting rods  10  can be associated with a single handgrip “I”. Similarly, the further mechanical connector  12  allows a single detection head  20  to be used with two or more different supporting rods  10  (for longitudinal, angular or laparoscopic probes, respectively). 
     The invention achieves the preset aims eliminating the drawbacks of the prior art. 
     In effect, the structure of the detector “R” according to the invention allows an investigation on a three-dimensional zone encompassing, in a longitudinal plane of the detector “R”, a very large angle. 
     Moreover, the structure of the detection elements  21   a,    21   b  inserted at different depths in the collimators  24  makes it possible to achieve optimum collimation of the radiation with an increase in the overall resolution, in particular defining a large detection angle at the sides and a high spatial resolution in the front zone. 
     Moreover, the possibility of connecting/removing the handgrip “I” from the detection probe “S” makes it possible to reduce the costs relative to the detector “R” and to increase its versatility. 
     Furthermore, the arrangement and size of the detection elements  21   a,    21   b  means that the procedure for determining parts of the patient affected by tumor cells or specific disease cells is simplified, speeded up and more precise. In effect, the greater dimension (volume) or surface extension of the central crystal makes it possible to optimize the space inside the detection head, giving more space to the central crystal designed for high precision detection of the radiation source, with the lateral crystals only performing a single “directional” function without specific precision requirements. Lastly, the detector “R” according to the invention is compact and thus very easy to handle and suitable for intraoperative investigation inside the patient&#39;s body cavities.