The Effect of Defective PET Detectors in Clinical Simultaneous [18F]FDG Time-of-Flight PET/MR Imaging.
The purpose of this study was to evaluate the effect of defective positron emission tomography (PET) detectors on clinical PET image quality in simultaneous PET/magnetic resonance imaging (MRI) for both time-of-flight (TOF) and non-TOF reconstructed images.



A total of six patients with various malignant tumors were included and underwent a 2-deoxy-2-[18F]fluoro-D-glucose PET scan in a fully functional simultaneous TOF PET/MRI. TOF and non-TOF PET images were reconstructed before and after simulating defective detector units. All images were clinically assessed and scored. In addition, a quantitative assessment was performed. Differences were ascertained and compared using the Wilcoxon matched pairs signed-rank test.



Without TOF, the image artifacts introduced by one defective detector unit already started to degrade the overall image quality. It reduced the confidence and could lead to a change in diagnosis. Simulating three or five defective detector units resulted in more artifacts and further reduced overall image quality and confidence. By including TOF information, the effects were mitigated: Images reconstructed with one defective detector unit had similar scores as the ones without defective units. The average absolute percentage error for one, three, and five defective detector units were respectively 8, 20, and 37 % for the non-TOF cases and only 5, 11, and 19 % for the TOF cases.



Our study indicates that PET image artifacts due to (simulated) defective detectors are significantly mitigated with the integration of TOF information in simultaneous PET/MR. One defective detector unit introduces, on average, a 5 % absolute percentage error. However, in TOF imaging, even in cases with one or three defective units for head and neck imaging and one defective unit for chest and abdominal imaging, overall image quality, artifact scoring, and reader confidence are not significantly degraded.
Department of Nuclear Medicine, University Hospital Zurich, Rämistrasse 100, 8091, Zurich, Switzerland. Edwin.terVoert@usz.ch.|University of Zurich, Zurich, Switzerland. Edwin.terVoert@usz.ch.
Edwin E G W
EEGW
Ter Voert
GE Healthcare, Waukesha, WI, USA.
Gaspar
G
Delso
Department of Nuclear Medicine, University Hospital Zurich, Rämistrasse 100, 8091, Zurich, Switzerland.|University of Zurich, Zurich, Switzerland.
Felipe
F
de Galiza Barbosa
Department of Nuclear Medicine, University Hospital Zurich, Rämistrasse 100, 8091, Zurich, Switzerland.|University of Zurich, Zurich, Switzerland.|Department of Neuroradiology, University Hospital Zurich, Zurich, Switzerland.
Martin
M
Huellner
Department of Nuclear Medicine, University Hospital Zurich, Rämistrasse 100, 8091, Zurich, Switzerland.|University of Zurich, Zurich, Switzerland.|Department of Diagnostic and Interventional Radiology, University Hospital Zurich, Zurich, Switzerland.
Patrick
P
Veit-Haibach
D000328:Adult; D000368:Aged; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000737:chemistry*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009928:Organ Specificity; D049268:Positron-Emission Tomography; D051598:Whole Body Imaging
D019788:Fluorodeoxyglucose F18
Clinical; Defective detectors; PET/MR; Simulation; Time-of-flight