Influence of CT/MRI image fusing technique on target volume and dosimetrics of normal tissues in intensity modulated radiotherapy for prostate carcinoma

Abstract

Objective To explore the influence of computed tomography (CT) and magnetic resonance imaging (MRI) fusing technique on target volume and dosimetrics of normal tissues in intensity modulated radiotherapy (IMRT) for prostate carcinoma.Methods Ten patients with pathologically diagnosed moderate-high risk localized prostate carcinoma were enrolled in this study.CT and MRI images were collected.Same image slices of the prostate, seminal vesicles, rectum and bladder were anatomically delineated using image fusing software.Clinical target volume (CTV) was defined as the prostate plus seminal vesicles.IMRT treatment planning was designed basing on CT and MRI images, respectively.Differences of CTV volume and dose volume histogram of rectum and bladder between the two image groups were analyzed.Results The mean volume of CTV on CT and MRI images was 84.03 cm3 and 53.53 cm3,respectively (t =2.47,P=0.024).The V50, V60 and V70 of rectum were 30.28%, 19.13%, 9.53% on MRI and 37.03%, 24.99% and 14.55% on CT images, respectively, with significent difference (t =2.71,P=0.014 for V50; t =2.83,P=0.011 for V60; t=3.19,P=0.005 for V70).The maximal dose of bladder was 81.10 Gy on MRI and 82.45 Gy on CT, respectively(t=2.41,P=0.027).Conclusions By using image fusing technique, the mean volume of the prostate plus seminal vesicles delineated on MRI image is smaller as compared to CT image.The volume of the rectum receiving high irradiation dose can be reduced when MRI was used to delineate CTV compared to CT image. Key words: Image fusion; Tomography, X-ray computed; Magnetic resonance imaging; Prostate neoplasms/intensity modulated radiotherapy; Dosimetry