Combined ultrasound and cone beam CT improves target segmentation for image guided radiation therapy in uterine cervix cancer.
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PURPOSE: Adaptive radiation therapy strategies could account for interfractional uterine motion observed in cervix cancer patients, but the current CBCT-based treatment workflow is limited by poor soft tissue contrast. The goal of the present study was to determine if ultrasound (US) could be used to improve visualisation of the uterus, either as a single modality or in combination with CBCT. METHODS AND MATERIALS: Interobserver uterine contour agreement and confidence were compared on 40 corresponding CBCT, US, and CBCT-US-fused images from 11 cervix cancer patients. Contour agreement was measured using the Dice Similarity Coefficient (DSC) and mean contour-to-contour distance (MCCD). Observers rated their contour confidence on a scale from 1 to 10. Pairwise Wilcoxon signed-rank tests were used to measure differences in contour agreement and confidence. RESULTS: CBCT-US-fused images had significantly better contour agreement and confidence than either individual modality (p < 0.05), with median [interquartile range (IQR)] values of 0.84 [0.11], 1.26 [0.23] mm, and 7  for the DSC, MCCD, and observer confidence ratings, respectively. Contour agreement was similar between US and CBCT, with median [IQR] DSCs of 0.81 [0.17] and 0.82 [0.14], and MCCDs of 1.75 [1.15] mm and 1.62 [0.74] mm. Observers were significantly more confident in their US-based contours than their CBCT-based contours (p < 0.05), with median [IQR] confidence ratings of 7 [2.75] versus 5 . CONCLUSIONS: CBCT and US are complementary, and improve uterine segmentation precision when combined. Observers could localize the uterus with a similar precision on independent US and CBCT images.
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uterine cervix cancer
Clinical Academic Radiotherapy (Dearnaley)
Imaging for Radiotherapy Adaptation
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Int J Radiat Oncol Biol Phys, 2019