DE-102019215437-B4 - Device for calibrating a PET system

Abstract

Device (1) for calibrating a PET system (S), wherein the PET system (S) has a plurality of detectors, wherein the PET system (S) has an opening (O) into which an element to be measured can be inserted, the device (1) comprising • at least one radiation source (Q), • at least one first collimator (K1) so that radiation from the radiation source (Q) can exit through a provided first opening (A1) at the collimator (K1). • wherein the device (1) defines an axial direction (R) with which the device (1) can be inserted into the PET system (S) for measurement, wherein the device (1) furthermore has a radial extension about the axial direction (R) thus defined, • wherein the device (1) can be moved radially and/or axially in the opening (O) in a predetermined manner so that detectors of the PET system (S) can be calibrated, • characterized in that the first collimator (K1) has a second opening (A2) for the emission of radiation, wherein the second opening (A2) is designed in the same way as the first opening (A1), and wherein the second opening (A2) is arranged at the same axial position as the first opening (A1) and opposite it on the radial extent.

Inventors

• Thomas DEY
• David Schug
• Patrick Hallen
• Volkmar Schulz
• Florian Müller

Assignees

• RHEINISCH-WESTFÄLISCHE TECHNISCHE HOCHSCHULE (RWTH) AACHEN

Dates

Publication Date

20260513

Application Date

20191009

Claims (12)

1. Device (1) for calibrating a PET system (S), wherein the PET system (S) comprises a plurality of detectors, wherein the PET system (S) has an opening (O) into which an element to be measured can be inserted, the device (1) comprising: • at least one radiation source (Q), • at least one first collimator (K1) such that radiation from the radiation source (Q) can exit from a provided first opening (A1) at the collimator (K1), • wherein the device (1) defines an axial direction (R) with which the device (1) can be inserted into the PET system (S) for measurement, wherein the device (1) further comprises a radial extension about the axial direction (R) thus defined, • wherein the device (1) can be displaced radially and/or axially in the opening (O) in a predetermined manner so that detectors of the PET system (S) can be calibrated, • characterized in that the first collimator (K1) has a second opening (A2) for the emission of radiation, wherein the second opening (A2) is designed in the same way as the first opening (A1), and wherein the second opening (A2) is arranged at the same axial position as the first opening (A1) and opposite it on the radial extent.
2. Device according to Claim 1 , characterized in that the device has a second collimator (K2), wherein the second collimator (K2) is arranged axially offset to the first collimator (K1).
3. Device according to Claim 3 , characterized in that the second collimator (K2) has a first hole opening (A3) as an opening for the exit of radiation.
4. Device according to Claim 3 , characterized in that the second collimator (K2) has a first strip opening (A3) as an opening for the emission of radiation.
5. device according to one of the preceding Claims 3 or 4 , characterized in that the second collimator (K2) has a second opening (A4) for the emission of radiation, wherein the second opening (A4) of the second collimator (K2) is designed in the same way as the first opening (A3) of the second collimator (K2), and wherein the second opening (A4) is arranged at the same axial position but opposite it on the radial extent.
6. Device according to Claim 5 , characterized in that the first opening (A3) of the second collimator (K2) is arranged offset from the second opening (A4) of the second collimator (K2) by an angle (α), wherein the angle is greater than 0° and less than 180°.
7. device according to one of the preceding Claims 2 until 6 , characterized in that the openings (A1, A2, A3, A4) in the first collimator (K1) and in the second collimator (K2) are designed in the same way, wherein the opening(s) (A1, A2) of the first collimator (K1) is arranged offset by an angle to an opening (A3, A4) of the second collimator (K2) on the axial extent, wherein the angle is greater than 0° and less than 180°.
8. Device according to one of the preceding claims, characterized in that the first collimator (K1) comprises a material with an atomic number of 70 or more, preferably 74 or 82.
9. Device according to one of the preceding claims, characterized in that the radiation emitted is gamma radiation or beta radiation.
10. Device according to one of the preceding claims, characterized in that the first collimator (K1) has a first hole opening as an opening (A1) for the emission of radiation.
11. Device according to one of the preceding claims, characterized in that the first collimator (K1) has a first strip opening (A1) as an opening for the emission of radiation.
12. Device according to Claim 11 , characterized in that the strip opening (A1) allows a radial exit of radiation.

Description

The invention relates to a device for calibrating a PET system. background Positron emission tomography (PET) is a well-known imaging technique in nuclear medicine and represents a variant of emission computed tomography. PET can generate cross-sectional images of living organisms by visualizing the distribution of a radioactive substance, known as a tracer. This allows for the imaging of biochemical and physiological functions. PET is based on the simultaneous detection of two gamma radiation photons that are produced after the decay of a positron-emitting radionuclide (β+ decay). When a positron interacts with an electron (annihilation) in the body, two high-energy photons (e.g., several hundred keV, especially 511 keV) are emitted in opposite directions. This radiation is also known as annihilation radiation. The PET scanner typically contains many photon detectors arranged in a ring around the patient. The principle of the PET scan is to record coincidences between any two opposing detectors. The temporal and spatial distribution of these recorded decay events is used to infer the spatial distribution of the radioactive substance within the body, and a series of cross-sectional images is generated. Since the absorption of photons depends only on the thickness of the tissue through which the photons are irradiated, and not on the point of origin of the photons, this also allows for an accurate quantification of the distribution of the radioactive substance in the volume under investigation. Most existing PET scanners work by stopping two high-energy photons (gamma photons) in crystals where a scintillation process generates optical photons. These crystals are therefore often called scintillation crystals. The photons are then detected by optical sensors and converted into electrical impulses. Typically, these crystals and the photosensors are arranged in a ring-like structure, also known as a detector ring. It is true that with increased spatial resolution, a better or more precise delineation of tissues becomes possible. However, it turns out that parallax errors occur at measurement points outside the center, which are also referred to as radial astigmatism. In order to better control parallax errors and improve spatial resolution, methods have been developed that determine the depth of interaction in the scintillation crystal (DOI). Small detector rings are frequently used for certain examinations of body parts (e.g., organ-specific PET scanners for mammography and neuroimaging) as well as for examining smaller organisms. The aforementioned improvement is most pronounced with these small detector rings and with PET scanners that have a large axial field of view. However, this requires finely structuring the scanners, and especially the scintillation crystals and associated photosensors, in the spatial directions so that gamma interaction with a resolution of 1-2 mm or less in the plane of the photosensors is enabled, as well as the detection of multiple DOI planes in the scintillation crystal. To make this possible, scintillation crystals are segmented, for example. This segmentation is extremely expensive and, due to the interposed layers, also reduces the resolution sensitivity, as less material is now available for scintillation processes. Therefore, systems with monolithic scintillation crystals have been developed in the past. Such systems have the capability to provide continuous DOI information. Regardless of the type of scintillation crystals used, i.e., segmented or unsegmented, position calibration is a problem. From the prior art according to US patent US 5 021 667 A A movable calibration collimator is known. Likewise, it is known from the prior art according to a US patent application. US 2006 / 0 180 766 A1 A scanner system is known. However, these systems are complex in design and are not suitable for rapid measurements. Against this background, the object of the invention is to provide a means of quick and easy position calibration for PET scanners. The problem is solved by a device according to claim 1. Further advantageous embodiments are in particular the subject of the dependent claims, the description and the figures. The invention is explained in more detail below with reference to the figures. These show: 1 a schematic perspective representation of elements of a PET system with a device according to the invention, 2 a view into the opening of the PET system with a device according to the invention, 3 a view of one side of a PET system with a device according to the invention, 4 a schematic top view of elements of a device according to the invention in embodiments of the invention, 5 a schematic top view of elements of a device according to the invention in embodiments of the invention, 6 a schematic top view of elements of a device according to the invention in embodiments of the invention, 7 a schematic top view of elements of a device according to the invention in embodiments o