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Matheoud R.,Azienda Ospedaliero Universitaria Maggiore della Carita | Goertzen A.L.,University of Manitoba | Vigna L.,Azienda Ospedaliero Universitaria Maggiore della Carita | Ducharme J.,Great West Life Imaging Center | And 2 more authors.
Physica Medica | Year: 2012

PET scanners require routine monitoring and quality control (QC) to ensure proper scanner performance. QC helps to ensure that PET equipment performs as specified by the manufacturer and that there have not been significant changes in the system response since acceptance. In this work we describe the maintenance history and we report on the results obtained from the PET system QC testing program over 5 years at two centers, both utilizing a Siemens Biograph 16 HiRez PET/CT system. QC testing programs were based on international standards and included the manufacturer's daily QC, monthly uniformity and sensitivity, quarterly cross-calibration and annual resolution and image quality.For the Winnipeg and Novara sites, two and one PET detector blocks have been replaced, respectively. Neither system has had other significant PET system related hardware replacements. The manufacturer's suggested daily QC was sensitive to detecting problems in the function of PET detector elements. The same test was not sensitive for detecting long term drifts in the systems: the Novara system observed a significant deterioration over five years of testing in the sensitivity which exhibited a decrease of 16% as compared to its initial value measured at system installation. The measure of the energy spectrum, showed that the 511. keV photopeak had shifted to a position of 468. keV. This shift was corrected by having service personnel perform a complete system calibration and detector block setup.We recommend including tests of system energy response and of sensitivity as part of a QC program since they can provide useful information on the actual performance of the scanner. A modification of the daily QC test by the manufacturer is suggested to monitor the long term stability of the system. Image quality and spatial resolution tests have proven to be of limited value for monitoring the system over time. © 2011 Associazione Italiana di Fisica Medica. Source

Elhami E.,University of Manitoba | Samiee M.,University of Manitoba | Samiee M.,Health Science Center | Demeter S.,University of Manitoba | And 5 more authors.
Molecular Imaging and Biology | Year: 2011

Introduction: Clinical positron emission tomography (PET) systems based on block detector designs suffer occasional block detector failures, which can result in patient scan cancelations. In this study, we examine the effect of defective block detectors on measurements of maximum standard uptake value (SUV max) and clinical image quality in 3D 2-deoxy-2-[ 18F]fluoro-D-glucose (FDG) PET/computed tomography (CT) imaging. Methods: A Data Spectrum anthropomorphic torso phantom (4.7 kBq/ml FDG concentration, defined as SUV of 1.0) was imaged in a normally functioning Siemens Biograph 16 HiRez PET/CT scanner using a whole-body imaging protocol. Spherical lesions with SUVs ranging from 10.0 to 13.5 were placed in the phantom. Defective block detectors were simulated by zeroing the appropriate lines of response in the sinograms. Eleven one-block and seventeen two-block defect configurations were simulated in the phantom sinograms. The images were reconstructed, and the measured SUV max was compared with the SUV max for the images without detector defects. Twelve clinical PET scans were evaluated before and after simulated detector defects cases ranging from a single block up to 12 blocks (bucket). The reconstructed images were independently scored for image quality and clinical diagnosis by two nuclear physicians blinded to the presence and severity of defects in the images. Results: The mean change in phantom SUV max was -2% (range, -6% to +3%) in the presence of a single defective block detector and -3% (range, -11% to +7%) in the presence of two defective block detectors, respectively. For the clinical patient studies, there was no significant decline in image quality score from one to two defective block detectors. In the case of 3-4 defective block detectors, image quality became marginal, and image degradation was significant with a defective bucket (12 blocks). Conclusion: For one or two defective block detectors in a 3D PET camera, while waiting for the repair service, routine patient scans can proceed with the proviso that the reading physician is made aware of the detector failure. © Academy of Molecular Imaging and Society for Molecular Imaging, 2010. Source

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