Quantitative accuracy of

backgroundRing-shaped systems based on CZT are promising for quantitative imaging, but their accuracy may be affected by septal penetration of high-energy photons-given the fixed collimator-and by limitations in scatter correction due to low-energy tailing. This study compares the quantitative performance of a ring-shaped CZT system with that of a conventional dual-head NaI SPECT/CT system (StarGuide™ and NM/CT 870 DR, both GE HealthCare) using the 208 keV photopeak of

methodsA NEMA phantom with 3D-printed anthropomorphic inserts, including kidneys and lumbar vertebrae, as well as standard spherical inserts, was filled with activity concentrations mimicking the distribution observed in patients 1 day post-injection of 7.4 GBq of [

resultsThe total activity measured within the phantom deviated from the expected value by means of 13% for the StarGuide™ and 0% for the NM/CT 870 DR. After partial-volume-effect correction based on recovery coefficients, the activity concentration in kidney inserts was measured with ~ 5% accuracy on both systems. For the StarGuide™, mean errors in tumour inserts (volumes: 2.6-28 ml) ranged from - 8% to 3%, whereas a consistent underestimation by an average of - 11% was observed for the NM/CT 870 DR. The StarGuide™ significantly overestimated the background activity concentration (59%), while the NM/CT 870 DR showed a smaller error (- 8%). Reproducibility was lower for the StarGuide™, with maximum CV values of 7%, compared with 3% for the NM/CT 870 DR. Clinical findings were consistent with phantom results.

conclusionsThe StarGuide™ provided slightly more accurate activity quantification in regions of high relative uptake, such as tumours and kidneys, compared with the NM/CT 870 DR. However, quantification in regions of low relative uptake and total activity estimation were less accurate, likely due to septal penetration. The lower reproducibility suggests that longer scan durations may be considered.