Comparison of computed tomography- and magnetic resonance imaging-based target delineation for cervical cancer brachytherapy

PURPOSE: The objective of this study was to compare and assess the accuracy of computed tomography (CT)-based target delineation with that of magnetic resonance imaging (MRI)-based on high-dose-rate brachytherapy (HDR-BT) for patients with cervical cancer. MATERIAL AND METHODS: Data of 20 patients with locally advanced cervical cancer were collected and evaluated. Dimensions, conformity, and dose parameters of high-risk clinical target volume (CTV(HR)) as well as D(0.1cc), D(1cc), and D(2cc) of organs at risk (OARs) based on MRI were compared with those based on CT. RESULTS: Average age of 20 patients included was 57.8 years. Width, thickness, and volumes of CT-based CTV(HR) (CTV(HR)-CT) were significantly overestimated compared with those of MRI-based CTV(HR) (CTV(HR)-MR). Mean values of dice similarity coefficient (DSC), Hausdorff distance (HD), and centroid distance (ΔV) of CTV(HR) were 0.82 cm, 0.96 cm, and 0.35 cm, respectively. Dose values of CTV(HR)-CT were significantly lower compared with those of CTV(HR)-MR. Concerning OARs, geometrical and dosimetric values on CT were comparable to those on MRI. CONCLUSIONS: The delineated ranges of CTV(HR) were significantly over-estimated on CT compared with MRI. D(98) and D(90) of CTV(HR)-CT were lower than CTV(HR)-MR. DSC and ΔV of CTV(HR) and CTV(IR) were similar to each other; however, there was a difference in terms of HD. CT images regarding pre-BT MR images for delineating were not enough and MRI fusion is still required.