Purpose: To compare the contours and dose volume histograms (DVH) parameters of the high-risk clinical target volume (HRCTV) contoured on computed tomography (CT) using clinical findings at brachytherapy, clinical findings at brachytherapy with magnetic resonance imaging (MRI) at diagnosis and HRCTV defined on MRI at brachytherapy in cervical cancer patients.
Materials and methods:Fifteen patients undergoing MRI-guided image-based brachytherapy underwent both CT and MRI after applicator insertion. Two sets of contours were defined on CT. In the first set, the HRCTV was defined with the help of clinical findings at brachytherapy (CT-HRCTV). In the second set, HRCTV was defined with MRI at diagnosis and clinical findings at brachytherapy (CT-HRCTVdmri). This was compared with the HRCTV defined on MRI at brachytherapy (MR-HRCTV). The doses to the organs at risk (OARs) were compared for CT and MRI.Results: A significant overestimation of the maximum width and width at point A was observed for CT-HRCTV (p 20?00; 0?00) and CT-HRCTVdmri (p 20?03; 0?01), respectively. The height was underestimated with CT-HRCTV in patients with intrauterine disease extension. For a single fraction, the mean difference in the D90 for the CT contours was ,1 Gy. The doses to the OARs were comparable.Conclusions: CT may be an alternative when facilities for MRI image-based brachytherapy are lacking, provided at least one MRI is available before brachytherapy.
Both electrons and 3DCRT can be used for boost planning to the tumor bed in post-lumpectomy patients. Though there was slightly increased acute skin toxicity with 3DCRT photon which led to interruption of therapy, overall cosmesis at 2 years is similar in both modalities. 3DCRT boost is a better option than electrons dosimetrically, considering the fact that conformality; PTV coverage and OAR dosimetry were superior with photons. Thus in centers where electron beam therapy is not available, 3DCRT photon can be used effectively for tumor bed boost.
The purpose of this study is to find the uncertainties in the reconstruction of MR compatible ring‐tandem intracavitary applicators of high‐dose rate image‐based brachytherapy treatment planning using rigid registration of 3D MR and CT image fusion. Tandem and ring reconstruction in MR image based brachytherapy planning was done using rigid registration of CT and MR applicator geometries. Verifications of registration for applicator fusion were performed in six verification steps at three different sites of tandem ring applicator set. The first site consists of three errors at the level of ring plane in (1) cranio–caudal shift (Cranial Shift) of ring plane along tandem axis, (2) antero–posterior shift (AP Shift) perpendicular to tandem axis on the plane containing the tandem, and (3) lateral shift (Lat Shift) perpendicular to the plane containing the tandem at the level of ring plane. The other two sites are the verifications at the tip of tandem and neck of the ring. The verification at the tip of tandem consists of two errors in (1) antero–posterior shift (AP Shift) perpendicular to tandem axis on the plane containing the tandem, and (2) lateral shift (Lat Shift) perpendicular to the plane containing the tandem. The third site of verification at the neck of the ring is the error due to the rotation of ring about tandem axis. The impact of translational errors from −5 mm to 5 mm in the step of 1 mm along x‐, y‐, and z‐axis and three rotational errors about these axes from −19.1° to 19.1° in the step of 3.28° on dose‐volume histogram parameters (normalD2cc,normalD1cc,normalD0.1cc, and normalD5cc of bladder, rectum, and sigmoid, and D90 and D98 of HRCTV were also analyzed. Maximum registration errors along cranio–caudal direction was 2.2 mm (1 case), whereas the errors of 31 out of 34 cases of registration were found within 1.5 mm, and those of two cases were less than 2 mm but greater than 1.5 mm. Maximum rotational error of ring about tandem axis was 3.15° (1.1 mm). In other direction and different sites of the ring applicator set, the errors were within 1.5 mm. The impacts of registration errors on DVH parameters of bladder, rectum, and sigmoid were very sensitive to antero–posterior shift. Cranio‐caudal errors of registration also largely affected the rectum DVH parameters. Largest change of 17.95% per mm and 20.65% per mm in all the DVH parameters of all OARs and HRCTV were observed for ϕ and normalΨ rotational errors as compare to other translational and rotational errors. Catheter reconstruction in MR image using rigid registration of applicator geometries of CT and MR images is a feasible technique for MR image‐based intracavitary brachytherapy planning. The applicator registration using the contours of tandem and neck of the ring of CT and MR images decreased the rotational error about tandem axis. Verification of CT MR image fusion using applicator registration which consists of six steps of verification at three different sites in ring applicator set can report all the errors due to translation and rota...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.