Setup error analysis in helical tomotherapy based image-guided radiation therapy treatments

Abstract

The adequacy of setup margins for various sites in patients treated with helical tomotherapy was investigated. A total of 102 patients were investigated. The breakdown of the patients were as follows: Twenty-five patients each in brain, head and neck (H and N), and pelvis, while 12 patients in lung and 15 in craniospinal irradiation (CSI). Patients were immobilized on the institutional protocol. Altogether 2686 megavoltage computed tomography images were analyzed with 672, 747, 622, 333, and 312 fractions, respectively, from brain, H and N, pelvis, lung, and CSI. Overall systematic and random errors were calculated in three translational and three rotational directions. Setup margins were evaluated using van Herk formula. The calculated margins were compared with the margins in the clinical use for various directions and sites. We found that the clinical isotropic margin of 3 mm was adequate for brain patients. However, in the longitudinal direction it was found to be out of margin by 0.7 mm. In H and N, the calculated margins were well within the isotropic margin of 5 mm which is in clinical use. In pelvis, the calculated margin was within the limits, 8.3 mm versus 10 mm only in longitudinal direction, however, in vertical and lateral directions the calculated margins were out of clinical margins 11 mm versus 10 mm, and 8.7 mm versus 7.0, mm respectively. In lung, all the calculated margins were well within the margins used clinically. In CSI, the variation was found in the middle spine in the longitudinal direction. The clinical margins used in our hospital are adequate enough for sites H and N, lung, and brain, however, for CSI and pelvis the margins were found to be out of clinical margins.

Determination of optimal clinical target volume to planning target volume margins for conformal radiotherapy planning using image guidance system in rectal cancer in prone position

“…demonstrated that with a margin of 10 mm applied in both vertical and longitudinal direction, and a margin of 7 mm along the lateral direction has adequate target volume coverage in pelvic malignancies in the supine position. [6] Patni et al . also demonstrated a CTV-PTV margins expansion of 0.584, 1.036, and 0.566 cm in AP, SI, and ML directions, respectively, in pelvic malignancies in supine position.…”

“…have published and validated previously PTV margins specifically to their center for pelvis in the supine position. [67] In our radiotherapy center, 3DCRT and IMRT with image guidance is a routine practice. This study was conducted to assess the setup errors for rectal cancer patients being treated with 3DCRT in prone position, to determine the optimal CTV-PTV margin specific to our center.…”

Altered serum copper homeostasis suggests higher oxidative stress and lower antioxidant capability in patients with chronic hepatitis B

“…CHB was diagnosed following the 2015 guidelines for prevention and treatment of CHB. [ 11 ] Patients with acquired immunodeficiency syndrome, history of chemotherapy, or other chronic immune disorders were excluded. Written informed consent was obtained from all patients.…”

In regard to “Setup error analysis in helical tomotherapy based image-guided radiation therapy treatments”

“…in the latest issue of your journal. [ 1 ] The current rapid introduction of pretreatment (tomotherapy megavoltage computed tomography (CT) and cone-beam CT on Varian and Elekta linacs) and in-treatment (CyberKnife, ViewRay) image guidance (IG) needs a careful assessment of these technologies in order to establish their optimal usage. The authors investigated the position correction shifts for 102 patients treated with helical tomotherapy using megavoltage CT for matching the patient position of the day to the planning CT study.…”

“…The margins calculated by Thondykandy et al . [ 1 ] correspond only to a part of the total planning target volume (PTV) construction accounting for interfraction motion as explained in BIR publication. [ 3 ] These margin values can be used to account for positioning errors if no pretreatment IG is performed.…”