Positron Coincidence Detection Research Articles

Practical assessment of myocardial viability with a positron coincidence gamma camera using 18F-fluorodeoxyglucose in acute myocardial infarction: Comparison with dedicated positron emission tomography and 201Tl single photon emission computed tomography

2-[(18)F] fluoro-2-deoxy-D-glucose ((18)F-FDG) began to be supplied commercially to our hospital, which does not have a cyclotron, in autumn of 2005. The purpose of this study was to compare the utility of a dual-head positron coincidence detection (PCD) gamma camera in the detection of myocardial viability using (18)F-FDG with that of dedicated positron emission tomography (PET) and with that of thallium-201 ((201)Tl) single photon emission computed tomography (SPECT). A total of 15 patients (14 men and 1 woman, mean age: 60+/-7 years, range: 46-73) with a large acute myocardial infarction (AMI) underwent (18)F-FDG PET, (18)F-FDG PCD imaging after oral glucose loading (75 g) and (201)Tl SPECT imaging. We divided the SPECT and PET images into a total of 20 segments, and semiquantitative visual analysis was performed by assessing regional tracer activities on a 4-point scoring system (DS): 0=normal uptake, 1=mildly reduced uptake, 2=severely reduced uptake, and 3=no uptake. We summed the DS in each patient as the total DS (TDS). The TDS of the (18)F-FDG PET image was 14.4+/-7.7. The TDS of the (18)F-FDG PCD image was 18.7+/-7.7. The TDS of the (201)Tl SPECT image was 24.1+/-11.5. The TDS of the (18)F-FDG PET image was significantly smaller than that of the (18)F-FDG PCD image. The TDS of the (18)F-FDG PET image was significantly smaller than that of the (201)Tl SPECT image. The TDS of the (18)F-FDG PCD image was significantly smaller than that of the (201)Tl SPECT image. The findings of the project suggest that (18)F-FDG PCD is a good modality based on its accuracy, convenience, and cost-performance for detecting myocardial viability in hospitals that do not have a PET system.

Determination of three-dimensional voxel sensitivity for two- and three-headed coincidence imaging

Recently, SPECT and positron emission tomography imaging modalities have been hybridized so that positron coincidence detection can be accomplished with SPECT systems. Originally, only systems with two opposing camera heads were employed. Recent developments to improve sensitivity include the addition of a third camera head. Several authors have developed methods to calculate line-of-response and voxel sensitivities, known as rotational and geometric weights, respectively. These weights are important for use as normalization factors in iterative image reconstruction, as well as to provide insight into the nonuniformity of voxel sensitivity across the reconstructed field-of-view. Although their formulations use analytic expressions, the equations derived for the voxel sensitivities involve an integral which cannot be computed in closed form; that is, one must use a numerical approximation. This may affect the voxel sensitivity in that the accuracy and speed of such a discrete calculation are heavily dependent on the mesh size used. The authors' alternative approach, that does not rely on the numerical approximation, is to directly calculate the solid angle subtended by each voxel with the detectors over all detector positions. They include results for two camera heads 180/spl deg/ apart (DUAL), three camera heads 120/spl deg/ apart (TRI), and three camera heads 90/spl deg/ and 180/spl deg/ apart (C-SHAPE), with and without axial collimation.

Detection of lung cancer with positron coincidence gamma camera using fluorodeoxyglucose in comparison with dedicated PET

Objective: Dual-head gamma cameras with sodium iodide (NaI) detectors operated in coincidence mode provide a new approach for imaging with positron-labeled tracers. The purpose of this study was to evaluate the feasibility of FDG imaging with positron coincidence detection gamma camera (PCD) in detecting lung tumor in comparison with FDG imaging with the dedicated positron emission tomography (PET). Methods and material: Twenty-six lesions of 13 patients with suspected lung cancer were studied with both FDG PET and FDG PCD on the same day. Pulmonary lesions were analyzed visually and semi-quantitatively using the ratio of target-to-background counts (T/B ratio). Results and conclusions: FDG PCD and FDG PET could detect visually 21 lesions (80.8%) and 23 lesions (88.0%), respectively. The mean T/B ratio and standard deviation (S.D.) of FDG PCD was 4.6±3.9, significantly lower than that of FDG PET (11.4±6.6, P<0.001). When pulmonary lesions were no more than 2.0 cm in diameter, the sensitivity of FDG PCD was 37.5%, significantly inferior to that of FDG PET (62.5%, P<0.001). There was no statistically significant difference of the sensitivity between the FDG PCD and FDG PET in lesions of more than 2.0 cm in diameter. FDG PCD with uniform attenuation correction was clinically available in detecting lung cancer. However, the sensitivity for small lesions less than 2.0 cm was limited. The application of measured attenuation correction and scatter correction may to be needed to improve the detectability of FDG PCD, especially for detecting small lung cancer.

Oncological diagnosis using positron coincidence gamma camera with fluorodeoxyglucose in comparison with dedicated PET

The purpose of this study was to compare the utility of a dual-head positron coincidence detection gamma camera (PCD) with that of dedicated positron emission tomography (PET) in the imaging of various malignancies using (18)F-fluorodeoxyglucose (FDG). 25 patients with known or suspected malignancies at various sites underwent imaging with both methods, and diagnostic performance on a lesion basis was compared. Tumour lesions were analyzed visually and semi-quantitatively using the ratio of tumour-to-background counts (T/B ratio). FDG PCD and FDG PET visually detected 34 (72.3%) lesions and 37 (78.7%) lesions, respectively. The mean T/B ratio and standard deviation (SD) of FDG PCD was 3.5+/-3.3, significantly lower than that of FDG PET (8.4+/-7.1, p<0.001). When tumour lesions were less than 2.0 cm in diameter, the sensitivity of FDG PCD was 37.5%, significantly inferior to that of FDG PET (50.0%, p<0.01). Sensitivity between FDG PCD and FDG PET in lesions of more than 2.0 cm diameter showed no statistically significant difference. This study indicates that FDG imaging with a dual-head coincidence detection gamma camera can provide suitable diagnostic performance for lesions greater than 2.0 cm diameter, but performed significantly worse than dedicated PET for lesions smaller than this.

F-18-fluoro deoxyglucose SPECT (FDG)/positron coincidence detection (PCD) and endoscopic ultrasound (EUS) may be an ideal combination for further work-up of pancreatic adenocarcinoma when conventional imaging is either negative or equivocal

F-18-fluoro deoxyglucose SPECT (FDG)/positron coincidence detection (PCD) and endoscopic ultrasound (EUS) may be an ideal combination for further work-up of pancreatic adenocarcinoma when conventional imaging is either negative or equivocal

Positron detection: principles and instrumentation

Based on the technology of positron coincidence detection. PET (positron emission tomography) measures the 3D distribution of a radiotracer in the Human body. The basic detection unit consists of a scintillation crystal coupled to one or several photomultiplier tubes. The instrument performances depend on the intrinsic properties of the scintillator and on the tradeoff between image resolution, detection sensitivity and effective count rate. The major drawback in PET technology is the recording of random coincidences. Other sources of noise are related to campion scattering of the γ rays and on the kind of reconstruction algorithm usea. Up to now the filtered back projection algorithm has been mainly used for PET. The correct quantification of PET images allow to compare radiotracer uptake in follow-up studies or to compare a patient with a control population. Such quantification requires a correction for photon attenuation usually achieved with a transmission measurement. Research perspectives in PET technology include: 1) the development of hybrid detectors when can be used for both single photon or positron imaging; 3) the development of an instrument combining anatomical imaging using an X-ray scanner and functional imaging using a PET.

One-Nanosecond Overlap Coincidence Counting to Track PET Agents over Six Decades

Residue functions track the clearance of radio-labeled substrates through key metabolic pathways. Fast positron coincidence detection (BaF2, CsF) has a millihertz benchtop background. Subnanosecond resolution is preserved by delay-trimming NIM negative logic in a three-fold overlap "AND" circuit, enabling measurements over six decades of dynamic range on isolated animal preparations.