Technical note: factors affecting dose distribution in the overlap region of two-segment total body irradiation by helic
- PDF / 1,410,146 Bytes
- 7 Pages / 595.276 x 790.866 pts Page_size
- 12 Downloads / 139 Views
Open Access
METHODOLOGY
Technical note: factors affecting dose distribution in the overlap region of two‑segment total body irradiation by helical tomotherapy HaiYang Wang1†, JunQi Liu1†, YiFei Pi1, Qi Liu2, Yang Mi3, XiangXiang Yang1, YueXin Guo1* and RuiTai Fan1*
Abstract Objective: To assess the effects of various treatment planning parameters to identify the optimal gap distance for precise two-segment total body irradiation (TBI) using helical tomotherapy (HT) with fixed jaw mode. Methods and materials: Data of a treatment plan for 8 acute leukemia patients (height range: 109–130 cm) were analyzed. All patients underwent total-body computed tomography (CT) with 5-mm slice thickness. A lead wire, placed at 10 cm above the patella, was used to mark the boundary between the two segments. Target volumes and organs at risk were delineated using a Varian Eclipse 10.0 physician’s workstation. Different distances between the lead wire and the boundary of the two targets were used. CT images were transferred to the HT workstation to design the treatment plans, by adjusting parameters, including the field width (FW; 2.5 cm, and 5 cm), pitch (0.287 and 0.430), modulation factor (1.8). The plans were superimposed to analyze the dose distributions in the overlap region when varying target gap distances, FWs, pitches to determine the optimal combinations. Results: The pitch did not affect the dose distribution in the overlap region. The dose distribution in the overlap region was mostly homogeneous when the target gap distance was equal to the FW. Increased FW diminished the effect of the target gap distance on the heterogeneous index of the overlap region. Conclusions: In two-segment TBI treatments by HT with Helix mode, a gap distance equal to the FW may achieve optimal dose distribution in the overlap region. Keyword: Helical tomotherapy, Gap distance, Field width, Pitch, Total body irradiation Background Total body irradiation (TBI) is a radiation therapy technique that forms an important component of the pretreatment of patients for hematopoietic stem cell or bone marrow transplantation [1–4]. TBI in conjunction with chemotherapy serves as the preparative regimen to *Correspondence: [email protected]; [email protected] † HaiYang Wang and JunQi Liu are the Co-first authors 1 Department of Radiation Oncology, The First Affiliated Hospital of Zhengzhou University, Zhengzhou 450000, People’s Republic of China Full list of author information is available at the end of the article
avoid immunologic rejection of transplanted donor blood stem cells or bone marrow, by suppressing the immune system of recipients before transplantation. Moreover, it can eradicate residual disease cells in patients and empty space in the spinal cord, thereby increasing the success rate of bone marrow and stem cell transplantation [2, 4–7]. Helical tomotherapy (HT) is an intensity modulated radiation therapy (IMRT) applied using megavoltage computed tomography (MVCT), which can deliver radiation in a slice-by-slice pattern, rather than as
Data Loading...
