SiPM-based vs LYSO-based ⁶⁸Ga-DOTA-TATE PET/CT: Comparison of Semi-Quantitative Measurements in Normal Tissues and Lesions

Purpose: To compare the performance of a silicon photomultiplier (SiPM)-based PET/CT scanner (DMI) and a LYSO-based PET/CT scanner (D690) used in our clinic and to determine any differences in semi-quantitative measurements. Methods: We prospectively enrolled patients referred for ⁶⁸Ga-DOTA-TATE PET/CT. All patients underwent a single ⁶⁸Ga-DOTA-TATE injection dual imaging protocol: they were randomly scanned first on the D690 or the DMI scanner. SUV_max of different normal tissues and all detectable lesions from data acquired using both scanners were measured and recorded. RESULTS: Data from 21 patients (35-79 year-old; 21 women, 6 men) was analyzed. The mean±SD ⁶⁸Ga-DOTA-TATE dosage was 5.9 ± 0.8 mCi (range 4 - 7 mCi). Eleven patients out of 21 (52%) underwent DMI as first scan and a total of 42 lesions were detected on both scanners; 10 patients out of 21 (48%) performed D690 PET/CT as first scan and a total of 33 lesions were seen on both scanners. Regardless of whether DMI was performed first or second, average SUV_max of lesions measured on DMI was higher. The agreement analysis for different normal tissues indicated that these measurements from the two scanners were similar regardless of scan order, except for pituitary and parotid (Table 1). CONCLUSIONS: We observed higher SUV_max values for lesions measured from DMI compared to D690 regardless of the order of the scan, while the measurements were similar for normal tissues. While delayed imaging can lead to higher SUV_max values in cancer lesions, in the series of lesions identified when DMI was performed as first scan this was not seen; therefore, the data suggests superior performance of the DMI scanner.

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