The gamma camera

Nuclear cardiology imaging is traditionally performed on an Anger gamma camera. Its key component is a large, flat, circular or rectangular sodium iodide crystal, activated by non-radioactive thallium (NaI(Tl)). The side of the crystal facing the patient is covered with a lead collimator, while the side away from the patient is viewed by an array of photomultiplier tubes (PMTs). This chapter provides detail on the gamma camera, including information on crystals and collimators, PMTs, and electronics. Important measures of gamma camera performance parameters and quality control are covered in detail, and a section on dedicated solid-state cardiac gamma cameras is included.

Detection of a gas region in a human body across a therapeutic carbon beam by measuring low-energy photons

We studied feasibility of detection of a gap which is located across a beam track by measuring low-energy (63–68 keV) photons generated by beam irradiation. An experiment was performed with the Heavy Ion Medical Accelerator in Chiba (HIMAC). A 12C beam having 290 MeV/u was injected on a target consisting of two acrylic blocks. These two blocks were placed with a 10 mm gap along the beam axis. A detection system consisting of a semiconductor detector, a lead collimator having a slit, and borated polyethylene blocks was placed on a movable stage to detect low-energy photons emitted perpendicularly to the beam axis. The position of the detection system was moved at 2 mm intervals along the beam axis. It was found that the yield of 63–68 keV photons was clearly correlated with the position of the detection system. The position at which the yield curve had the lowest value agreed with the gap position. We also confirmed that the experimental result was well reproduced by a Monte Carlo simulation that includes generation of secondary electron bremsstrahlung.

The gamma camera

Crystals and collimators 32Photomultiplier tubes and electronics 34Gamma camera performance parameters and quality control (1) 36Gamma camera performance parameters and quality control (2) 38Nuclear cardiology imaging is performed on an Anger gamma camera. Its key component is a large flat circular or rectangular sodium iodide crystal, activated by non-radioactive thallium (NaI(Tl)). The side of the crystal facing the patient is covered with a lead collimator, whilst the side away from the patient is viewed by an array of photomultiplier tubes (PMTs)....

A 2D Positioning Application in PET Using ANNs

Positron Emission Tomography (PET) is a radiotracer imaging technique based on the administration (typically by injection) of compounds labelled with positron emitting radionuclides to a patient under study. When the radio-isotope decays, it emits a positron, which travels a short distance before annihilating with an electron. This annihilation produces two high-energy (511 keV) gamma photons propagating in nearly opposite directions, along an imaginary line called Line of Response (LOR). In PET imaging, the photons emitted by the decaying isotope are detected with gamma cameras. These cameras consist of a lead collimator to ensure that all detected photons are propagated along parallel paths, a crystal scintillator to convert high-energy photons to visible light, photo-multiplier tubes (PMT) to transform light signals into electric signals, and associated electronics to determine the position of each incident photon from the light distribution in the crystal (Ollinger & Fessler, 1997). We have researched on how Artificial Neural Networks (henceforth ANNs or NNs) could be used for bias-corrected position estimation. Small-scale ANNs like the ones considered in this work can be easily implemented in hardware, due to their highly parallelizable structure. Therefore, we have tried to take advantage of the capabilities of ANNs for modelling the real detector response.

Use of single planar Ge(Li) detectors as gamma-ray polarimeters

The polarization sensitivity of a single rectangular Ge(Li) detector 40 × 25 × 3.5 mm has been studied as a function of energy using gamma rays of known linear polarization produced in (p,p′γ) reactions. The counting rates in the total absorption peaks were measured with the 40 × 25 mm face perpendicular [Formula: see text] and parallel [Formula: see text] to the plane defined by the ion beam and gamma-ray direction. The asymmetry ratio [Formula: see text] was measured using E2 gamma rays with known polarization. From these results the following values of Q for complete polarization were deduced for a series of energies: 0.847 MeV (16.4 ± 1.0)%, 1.368 MeV (13.1 ± 1.0)%, 1.779 MeV (12.4 ± 1.5)%, and 4.43 MeV (6.4 ± 1.0)%. These results were in quantitative agreement with calculations made using the Klein–Nishina formula. A large volume detector 60 × 35 × 6.5 mm was studied in a similar manner. The corresponding results for complete polarization are: 0.847 MeV (16.4 ± 1.0)%, 1.368 MeV (14.3 ± 2.0)%, 1.779 MeV (11.6 ± 1.2)%, and 4.43 MeV (5.8 ± 1.5)%. These values are slightly higher than those obtained in calculations. Tests were also made with a lead collimator 6.25 cm long with an aperture of 1 cm in front of the larger polarimeter. The results for complete polarization are: 1.779 MeV (14.0 ± 1.5)% and 4.43 MeV (9.0 ± 1.0)%. Some recent applications of high-resolution Ge(Li) linear polarimeters are briefly discussed.