Dual-isotope procedures using 3D-ring CZT StarGuide SPECT/CT: first clinical results from parathyroid acquisitions and head-to-head comparison with a conventional camera

Aim: The StarGuide 3D-ring CZT-camera (GE Healthcare, Haifa, Israel) is equipped with 12 swiveling high-resolution CZT detectors and a CT in a hybrid system. This system allows dual isotope acquisitions. In this preliminary work, we report the first clinical examples of parathyroid scintigraphy with the new StarGuide 360-degree CZT SPECT/CT system, compared to a conventional camera.

Methods: 5 patients (2 men; 3 women) referred for parathyroid scintigraphy were double scanned on a conventional camera (Discovery 670 Pro, GE Healthcare, Haifa, Israel) and on the new StarGuide CZT system, after mean injection of 12.8 MBq 123-iodine and 734 MBq of 99mTc-MIBI. SPECT duration was 22 and 15 minutes respectively for the conventional and the StarGuide systems. Patients acquired spectra on the conventional camera and on StarGuide were compared. Energy Resolution for 99mTc was calculated and expressed as the ratio of FWHM to the peak. Spill-over of 99mTc into the 123I energy window was defined as the percentage of 99mTc counts in the 123I energy window. Clinical data were visually analyzed by 3 board-certified Nuclear Medicine Physicians to score image quality, resolution and final diagnosis.

Results: StarGuide expressed a significant improvement in energy resolution compared to the conventional camera, with 5.1% versus 9.5% at 140.5keV respectively for StarGuide and the conventional system. Spillover of 99mTc towards the 123I imaging window in StarGuide was less than 2.5%, resulting in a nearly pure 123I thyroid image, whereas it was ~85% on the conventional camera. Using a 5-point Likert scale, StarGuide mean image quality and resolution were respectively 4.3 and 4.4. The new system provided clearer delineation of parathyroid uptake, especially in pathological patients, compared to the conventional camera and a better image quality for 123I showing only thyroid gland without background. For all raters and patients, StarGuide provided same or better images and information relative to the reference camera.

Conclusions: Using StarGuide, 3D-ring CZT parathyroid dual isotope SPECT acquisitions become feasible in short acquisition time, with a great image quality and energy resolution, and also in some cases better clinical information relative to the conventional SPECT/CT camera.

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