Comparison of Peripheral Low Dose with or without Flattening Filter in SABR and VMAT

• Main Authors: Wei-Lin Chen, 陳韋霖
• Other Authors: Pao-Shu Chang
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/97193939822510780825

碩士 === 高雄醫學大學 === 醫學影像暨放射科學系碩士在職專班 === 104 === Purpose: To investigate the flattening filter free (FFF) photon beam properties and assessing the impact of peripheral low dose in current mainstream radiotherapy in VMAT and SABR. Materials and Methods: In the same quality of treatment plans, we compare the convention and FFF beam modes, respectively. The T1 phase non-small cell lung cacer (NSCLC) treatment by stereotactic ablative radiotherapy (SABR) and the pediatric glioma treat by volumetric modulated arc therapy (VMAT), using optically stimulated luminescence dosimetry (OSLD) and anthropomorphic Rando phantom, measurement the out of field dose of normal tissues. Results: The NSCLC T1 phase treat by SABR FFF beam mode, total prescription dose was 60 Gy, peripheral dose including the lens, thyroid, apex, lung, esophagus, heart, lower lung, breast, liver, stomach, kidney, ascending colon, descending colon, ovarian and bladder show an average reduction was 27.03%, 8.23%, 14.11%, 17.40%, 17.85 %, 13.00%, 20.09%, 21.69%, 25.28%, 23.62%, 23.99%, 36.71%, 27.11%, 57.71% and 40.52% , respectively. The pediatric glioma treat by VMAT FFF beam mode, total prescription dose was 54 Gy, peripheral dose including the thyroid, apex, esophagus, heart, lung, breast, liver, kidney, intestine, ovarian and bladder show an average reduction was 22.64%, 27.20%, 21.33%, 22.78%, 22.36%, 22.35%, 24.25%, 22.54%, 31.10%, 46.98% and 45.76%, respectively. Compared to conventional beam, all the average absorbed dose of surrounding organs was lower when treat by FFF beam mode. Conclusion: Comparing with flattening filter beam and FFF beam, results showed that FFF beam decrease peripheral dose and reduced the risks of the radiation induced secondary malignancies, more obvious at 10 cm distance from field size edge and average reduces 47% (MAX), 32% (SABR) and 28% (VMAT). It need to be consider in patients with longer survival life after radiation therapy or pediatric patients.