Abstract:
Objective To evaluate the accuracy of automated delineation of the maximum cut-off value of nuclear medicine tomography in the automatic delineation of kidney volume in 99Tcm-diethylene-triamine pentaacetic acid (DTPA) renal dynamic scintigraphy. CT volumetric measurements were used as the reference standard.
Methods A prospective study was conducted on 29 patients (20 males and 9 females, mean age (43.9±2.2) years) who underwent cadmium zinc telluride (CZT)-SPECT/CT renal dynamic imaging at the Department of Nuclear Medicine, Tianjin Medical University General Hospital from March 2024 to July 2024. A hollow kidney phantom, 3D printed to match adult renal anatomical morphology and volume parameters, was filled with 99Tcm-DTPA solution and scanned using CZT-SPECT/CT renal dynamic imaging. The optimal cut-off for renal region of interest (ROI) delineation was determined by applying gradient cut-off of 20% maximum standardized uptake (SUVmax), 30% SUVmax, 40% SUVmax, and 50% SUVmax of the clinical target volume. In the clinical validation phase, the absolute value of the difference between the kidney volumes measured by nuclear medicine tomography and CT-based delineation were compared. Paired t-tests were used for intergroup comparisons, and Pearson correlation analysis and Bland–Altman plots assessed correlation and agreement between the two methods. Intraclass correlation coefficient (ICC) was used to evaluate the agreement of the two measurement methods.
Results In the phantom experiment, the absolute value of the difference between the measured and actual kidney volumes was significantly smaller at the 30% SUVmax of the clinical target volume cut-off ((3.07±5.89) cm3) compared with those at 20% SUVmax ((28.83±5.49) cm3), 40% SUVmax ((21.70±2.35) cm3), and 50% SUVmax ((31.43±5.75) cm3) (t=3.961, 2.937, 3.444, respectively; all P<0.05). In the clinical validation experiment, no significant difference was observed between the nuclear medicine tomography and CT-delineated kidney volumes at 30% SUVmax of the clinical target volume cut-off (left kidney: (166.88±9.41) cm3 vs. (163.24±7.59) cm3, t=1.377; right kidney: (166.85±8.28) cm3 vs. (162.37±6.21) cm3, t=0.822; both P>0.05). The ICC values for kidney volume measured by nuclear medicine tomography and CT contouring were 0.866 for the left kidney and 0.809 for the right kidney (both P<0.001). The correlation coefficient between the volume of the kidneys measured by nuclear medicine tomography and CT delineation was high (left kidney: r=0.79; right kidney: r=0.88; both P<0.001), and the correlation was good. Bland–Altman analysis showed 95% limits of agreement within clinically acceptable ranges.
Conclusion Automatic delineation at the 30% SUVmax of ROI in nuclear medicine tomography provides accurate kidney volume measurements.