TWI380801B - Dual photons emission computed tomography system - Google Patents

Description

Two-photon emission tomography system

The present invention relates to a dual photon emission computed tomography (DuPECT) system, in which certain isotopes can emit at least two photons during decay to serve as a source localization.

Positron emission tomography (PET) and single photon emission computed tomography (SPECT) are the two most commonly used Nuclear Medicine Imaging technologies. The advantage of SPECT is that the radiopharmaceuticals that can be used are more extensive and are also lower in price relative to PET.

The SPECT system uses a collimator to limit the photons incident direction and uses gamma ray projection imaging in different directions to create a three-dimensional tomographic image. The biggest problem with the collimator is that the spatial resolution varies with the distance between the source and the collimator, resulting in inconsistent system spatial resolution.

Traditional SPECT systems require a heavy collimator and a dectector to scan around the object under test, which requires a complex mechanical gantry to hold the detector to achieve the desired Accuracy. In addition, attenuation correction is an important issue in the quantitative analysis of SPECT systems. Since the explicit source position cannot be obtained from the projection data, attenuation correction has always been an unanswered problem.

The SPECT system is used to determine the concentration of radioisotope in the injected body to assess the physiological function. A scintillation camera is rotated around the periphery of the object to be detected to detect the addition of the radioactive agent. The photon spatially distributed image detected at an angle constitutes a planar image called a scintigram, and the scintillation graph obtained from a plurality of angles forms a full circle. Then, these scintillation curves are subjected to image recombination to calculate the three-dimensional spatial distribution of the radioisotope. Due to the influence of tissue attenuation, the gamma-ray image reconstructed by this SPECT system is not linearly related to the activity distribution of radioisotopes in patients. As a result, the tomographic slice cannot be accurately reflected. A true internal distribution.

The present invention provides a two-photon emission tomography system. It uses certain radioisotopes ( ¹¹¹ In, ¹²⁵ I) to emit more than two photons during the decay process to aid in the localization of the source.

The two-photon emission tomography system of the present invention comprises a plurality of modular detectors connected by a coincidence circuit. Each modular detector includes a collimator that defines the signal path of the incident photons. Slit-type collimators and hole-type collimators are available in two applications. The bore-type collimator includes a parallel collimator, a pinhole collimator, or a focusing collimator. In simple terms, the detector with a hole collimator is a hole detector, and the detector with a slit collimator is a slit detector.

The two-photon emission tomography system of the present invention has the following advantages:

1. Resting: In the traditional SPECT system, the scanner rotates 360° around the object to be measured to obtain projection information. Generally, the collimator is quite heavy, so the SPECT system will inevitably rotate when rotating. Causes the displacement of the center point, causing errors. The DuPECT system of the present invention calculates the geometric intersection to locate the source location, and does not require projection information of all angles for image reconstruction. Therefore, the DuPECT system is a fixed system and does not require a mechanical construction station for rotation.

2. Adaptability: The DuPECT system uses the module detector as a detection unit, and each detection unit can operate independently and can be placed anywhere around the object to be tested. Therefore, the DuPECT system can be placed very close to the object to be tested to enhance the sensitivity.

3. Scalability: Each detection unit operates independently, and each detection unit can be added or removed from the DuPECT system according to the needs of use.

4. No image reconstruction is required.

5. Can do quantitative analysis.

Since the source position is the focus of the line and the face, when each event is detected, the image can be updated at the same time. When the source location of an event is known, the attenuation coefficient and geometric efficiency can be calculated and updated directly on the image.

The above and other objects and advantages of the present invention will be described in detail with reference to the accompanying drawings.

Referring to the first figure, the first figure is a schematic diagram of an embodiment of the two-photon emission tomography system of the present invention. The two-photon emission tomography system 10 of the present invention includes a plurality of module detectors 11 connected by a homomorphic circuit 20. The module detector 11 includes a collimator that defines the signal path of the incident photons. The module detector 11 can be combined in accordance with the external shape of the object 21 to be scanned for scanning the object to be tested 21. The module detector 11 detects the photon signal P of the isotope 22 in the object 21 and feeds it back to the homolog circuit 20. The number of module detectors is not limited to any number. The module detector adds or removes this system in different applications. Five module detectors are used in the embodiment of the present invention.

The module detector 11 can be a hole detector or a slot detector. In this embodiment, the first, third, and fifth module detectors are aperture detectors, and the second and fourth module detectors are slot detectors. The second figure illustrates a schematic diagram of an implementation example in which a hole detector or a slot detector is used as a module detector. As shown in the second figure, the hole type detector 11a and the slit type detector 11b are arranged in an interlaced manner, for example, the hole type detector 11a is next to the slit type detector 11b. The aperture detector 11a includes a hole collimator 110. The slit detector 11b includes a slit collimator 120. The hole collimator 110 can be a parallel collimator, a pinhole collimator, or a focused collimator.

The third figure is an embodiment of a two-photon emission tomography system in accordance with the present invention. This system uses certain isotopes ( ¹¹¹ In, ¹²⁵ I) to emit at least two photons during decay. For example, the isotope ¹¹¹ In emits two additions of E-rays during electron capture (EC) decay. ₁ , Eγ ₂ , the energy is 171keV and 245keV, respectively, as shown in the second figure. The isotope ¹²⁵ I has a 35.5 k _e V addition ray, accompanied by some characteristic x-ray (x-ray) photons, whose energy ranges from 27 keV to 32 keV, although the photon energy emitted by ¹²⁵ I is too low. The patient is not the most ideal isotope, but it is very suitable for small animal or human local organs research, and the half life of ¹²⁵ I is 59.4 days, so it is also very suitable for long-term research.

The fourth figure is an example showing a schematic view of the incident photon position on the detection of the slit module detector. The trajectory signal point of the aperture detector 11b detecting the incident photon P is at the interaction point of the crystal 41 and the center point 43 of the aperture of the slit collimator 120.

Please refer to the fifth figure. For an example, a schematic diagram of the position of the source of the slot module detector and the hole module detector is described. The position of the photon detected by the slit detector 11b falls on the surface defined by the slit collimator 120 and the photon is detected. If the aperture detector 11a and the slot detector 11b simultaneously detect the source position of the two-photon, the source S is located just above the line defined by the aperture detector 11a and defined by the slot detector 11b. flat.

The sixth figure is a working example illustrating a schematic diagram of retrofitting a conventional PET system into a DuPECT system. Referring to the sixth diagram, a standard PET system can be converted to DuPET by using a collimator system in combination with a plurality of slit collimators 120 and a plurality of pinhole collimators 110. In a conventional PET system, a plurality of pinhole collimators 110 and a plurality of slit collimators 120 are disposed between the object to be tested 63 and the detecting ring 64, so that the photon signal P can be aligned through the pinholes. Instrument 110 and slit collimator 120 are fed back to detection ring 64.

The seventh figure shows the detection method of the DuPECT system modified by the pinhole collimator in the conventional PET system. Referring to the seventh figure, the hole collimator 110 is designed and arranged, and the object 63 is projected to the detection ring 64 through the pinholes of the hole collimator 110 and does not overlap each other. By placing the hole collimator 110 as close as possible to the object to be tested 63, the probability of escape of the photon can be improved. This embodiment is suitable for the study of humans and animals.

The eighth and eighth figures are working examples illustrating a schematic diagram of a merged slit module detector that converts an off-the-shelf SPECT into a two-photon emission tomography system. The slot module detector is combined on the SPECT to transform it into a two-photon emission tomography system. The slit module detector 11b and the SPECT 81 are connected by a homogenous circuit 20. The slot module detector 11b is placed next to the detection projection (non-coplanar) and does not interfere with the rotation of the SPECT construction station 82. Two modes of obtaining data: one is the still mode, the SPECT and the slit module detector are both stationary, and the image is generated by directly calculating the SPECT and the slit module detector simultaneously detecting the double The intersection of the paths between photons.

The second is the dynamic mode, only the SPECT is rotated, and the slit collimator module remains stationary. There are two sets of available data for this model: (1) data collected by SPECT alone; and (2) synchronized data collected by SPECT and slot module detectors. This SPECT data is a traditional sinogram that can be used to reconstruct and produce SPECT images. Since the relationship of two photons is required to arrive at the same time, the number of photons of the synchronized data will be less than that of the SPECT data, and the synchronization data can also be used to generate images. The SPECT image has attenuated artifacts, while the sync image has a more accurate source location, but more noise is mixed. The synchronized image is used to perform image reconstruction of the preliminary speculative SPECT data to produce a higher quality image. Synchronous detection between the SPECT and the slot module detector can be achieved without the same circuit. The SPECT and slot module detectors record the time, energy, and position of the photon arrival, respectively, and compare the two photon arrival times. If the arrival time is within a predefined time interval (eg, 12 ns), then two photons. For simultaneous detection.

Please refer to the ninth and tenth drawings at the same time. The ninth figure is a schematic diagram applied to the thyroid tomography, and the tenth is a schematic diagram applied to the breast tomography. The two examples are that the module detectors 11 are all connected by the same circuit 20, and are arranged and combined according to the shape of the thyroid 91 and the breast 101, and are disposed as close as possible to the thyroid 91 and the breast 101 as much as possible. Get the most sensitivity.

However, the above description is only the preferred embodiment of the invention, and the scope of the invention is not limited thereto. That is, the equivalent changes and modifications made by the scope of the patent application of the invention should remain within the scope of the invention.

10. . . DuPECT system

11. . . Module detector

11a. . . Hole detector

11b. . . Slit detector

110. . . Hole collimator

120. . . Slit collimator

20. . . Same circuit

twenty one. . . Analyte

twenty two. . . isotope

41. . . Crystal

43. . . Center point

63. . . Analyte

64. . . Detection loop

81. . . SPECT

82. . . SPECT construction platform

91. . . thyroid

101. . . breast

P. . . Photon signal

The first figure is a schematic diagram of an embodiment of a two-photon emission tomography (DuPECT) system of the present invention.

The second figure illustrates a schematic diagram of an implementation example in which a hole detector or a slot detector is used as a module detector.

The third figure is a schematic diagram of the isotope ¹¹¹ In emitting two gamma rays during the decay process.

The fourth figure is an example of a schematic diagram of a hole detector detecting the starting point of a photon.

The fifth figure is an example of a schematic diagram of the slot module detector and the hole module detector defining the position of the source.

The sixth figure is a working example illustrating a schematic diagram of retrofitting a conventional PET system into a DuPECT system.

The seventh figure shows the detection method of the DuPECT system modified by the pinhole collimator in the conventional PET system.

The eighth diagram is a working example illustrating a schematic diagram of incorporating a slot module detector to convert SPECT to a DuPECT system.

The ninth figure is a schematic diagram applied to thyroid tomography.

The tenth figure is a schematic diagram applied to a breast tomography.

10. . . DuPECT system

11. . . Module detector

20. . . Same circuit

twenty one. . . Analyte

twenty two. . . isotope

P. . . Photon signal

Claims (7)

A two-photon emission tomography system that uses an isotope to emit at least two photons during a decay process, the system comprising a plurality of module detectors connected by a same circuit; the module detector comprises a A collimator is used to define a signal trajectory of an incident photon; during scanning of an object, the module detector is disposed around the object according to the shape of the object. The two-photon emission tomography system of claim 1, wherein the module detector comprises a slit collimator as a slot module detector. The two-photon emission tomography system of claim 1, wherein the module detector comprises a hole type collimator as a one-hole module detector. The two-photon emission tomography system of claim 2, wherein the hole collimator is a pinhole collimator. The two-photon emission tomography system of claim 2, wherein the hole collimator is a focusing collimator. The two-photon emission tomography system of claim 2, wherein the hole collimator is a parallel collimator. The two-photon emission tomography system of claim 1, wherein the modular detector is a detection loop.