Is the Image Quality of I-124-PET Impaired by an Automatic Correction of Prompt GammasReport as inadecuate

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The aim of this study is to evaluate the quality of I-124 PET images with and without prompt gamma compensation PGC by comparing the recovery coefficients RC, the signal to noise ratios SNR and the contrast to F-18 and Ga-68. Furthermore, the influence of the PGC on the quantification and image quality is evaluated.


For measuring the image quality the NEMA NU2-2001 PET-SPECT-Phantom was used containing 6 spheres with a diameter between 10 mm and 37 mm placed in water with different levels of background activity. Each sphere was filled with the same activity concentration measured by an independently cross-calibrated dose calibrator. The -hot- sources were acquired with a full 3D PET-CT Biograph mCT®, Siemens Medical USA. Acquisition times were 2 min for F-18 and Ga-68, and 10 min for I-124. For reconstruction an OSEM algorithm was applied. For I-124 the images were reconstructed with and without PGC. For the calculation of the RCs the activity concentrations in each sphere were determined; in addition, the influence of the background correction was studied.


The RCs of Ga-68 are the smallest 79%. I-124 reaches similar RCs 87% with PGC, 84% without PGC as F-18 84%. showing that the quantification of I-124 images is similar to F-18 and slightly better than Ga-68. With background activity the contrast of the I-124 PGC images is similar to Ga-68 and F-18 scans. There was lower background activity in the I-124 images without PGC, which probably originates from an overcorrection of the scatter contribution. Consequently, the contrast without PGC was much higher than with PGC. As a consequence PGC should be used for I-124.


For I-124 there is only a slight influence on the quantification depending on the use of the PGC. However, there are considerable differences with respect to I-124 image quality.

Author: Veronika Preylowski, Susanne Schlögl, Frédéric Schoenahl, Gerhard Jörg, Samuel Samnick, Andreas K. Buck, Michael Lassmann



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