الملخص
ViewRay magnetic resonance (MR) guided radiotherapy system not only solves the problem of imaging dose,but also can set up accurately,online adaptive radiotherapy and gated irradiation according to magnetic resonance imaging (MRI).The development of this system provides a new technical means of accurate radiotherapy.This review describes the main structure of the ViewRay system,and summarizes quality assurance (QA),dosimetric comparison,respiratory motion management,online adaptive radiotherapy,and preliminary treatment effect.
الملخص
Cone-beam computed tomography (CBCT)-guided radiotherapy has been widely used in radiotherapy, but it still has many limitations.Using magnetic resonance imaging (MRI) instead of CBCT for imaging-guided radiotherapy can not only make use of the advantages of MRI, but it also allows for online and real-time tracking of tumor motion and biological changes.This technique truly realizes the real-time MRI-guided adaptive radiotherapy (ART) in anatomy and biology, and sets another milestone in the advancement of radiotherapy.This review summarizes the technical advantages of MRI-guided radiotherapy, the basic structure and type of MR-Linac, and the technical difficulties and solutions of MRIgART.
الملخص
Objective To investigate the dose distribution and radiation risk of Varian thoracic cone beam computed tomography (CBCT) with default parameters with reference to Monte Carlo simulation and International Commission on Radiological Protection (ICRP) report 110.Methods EGSnrc/BEAMnrc code was used to simulate the material, thickness, and geometry of the kV CBCT source (kVS) to establish the kVS model.A benchmarked MCSIM code was applied to calculate the dose distribution in the ICRP phantom after the scan with the standard thoracic parameters (110 kV, 20 mA, and 262 mAs), and the conversion coefficient of absolute dose was obtained in a spherical phantom following the TG-61 protocol.The results of Monte Carlo simulation were validated by PDD and Profile in a water phantom and the measurement of the absolute dose in the computed tomography dose index (CTDI) phantom and Alderson phantom.The models including BEIR VⅡ were used to evaluate the radiation risks.Results With reference to the criterion of 3%/1 mm, the uncertainties of PDD and Profile were less than 2%.The difference between the measured and calculated values was<2.9% in the CTDI phantom and ≤0.05 cGy in the Alderson phantom.In the ICRP110 phantom, the doses to the left lung, right lung, left breast, right breast, heart, thyroid, trachea, cancellous bone, and cortical bone were 1.28, 1.39, 1.74, 1.80, 1.46, 0.48, 0.88, 0.85, and 1.84 cGy, respectively.The relative risks of ischemic heart disease, breast cancer, lung cancer, thyroid cancer, and tracheal cancer in a standard scan were1.001 , 1.009, 1.019, 1.000, and 1.008, respectively. Conclusions The accumulated dose and long-term risks of CBCT during image-guided thoracic radiotherapy cannot be neglected and should be effectively controlled.
الملخص
Objective To evaluate the impact of different anatomical landmarks on registration in imaging-guided radiation (IGRT) for lung cancer. Methods For 20 patients with non-small cell lung cancer receiving stereotactic body radiotherapy (SBRT) in Fudan University Cancer Hospital, 100 frames of kilo-voltage cone-beam computed tomography scanning were evaluated in this study. The spine, carina and tumor were selected as landmarks for registration, respectively. Results of registration using different landmarks were documented and compared. Results The average set-up errors in the left-right, superiorinferior and anterior-posterior directions were -0. 08 cm ±0. 32 cm, -0. 16 cm ±0. 45 cm and 0. 06 cm ±0. 23 cm with the spine for registration;0. 06 cm ±0. 34 cm, -0. 13 cm ±0. 45 cm and -0. 02 cm±0.23 cm with the carina;and -0. 17 cm ±0.25 cm, 0.03 cm ±0.47 cm and 0. 15 cm ±0.38 cm with tumor. The registration results between using the carina and tumor as landmarks were statistically significant different (q=4.61, P=0. 002 ;q = 2. 23 , P=0. 118;q=3.44, P=0. 017). The registration results were equal when using the spine and tumor as landmarks ( q = 1.85, P = 0. 195; q = 2. 54, P = 0. 075; q = 1.89,P=0. 185), as well as using the carina and tumor as landmarks (q=2.76, P=0. 054;q=0.31, P=0. 826 ;q = 1.55, P = 0. 276). Conclusions For early stage lung cancer, the spine and tumor can be used equally as registration landmarks in imaging-guided SBRT. The carina is not suggested for its poor reproducible position.