Feasibility of using intermediate x‐ray energies for highly conformal extracranial radiotherapy. Issue 4 (20th March 2014)

• Record Type: Journal Article
• Authors: Dong, Peng; Yu, Victoria; Nguyen, Dan; Demarco, John; Woods, Kaley; Boucher, Salime; Low, Daniel A.; Sheng, Ke
• Is Part Of: Medical physics. Volume 41:Issue 4(2014)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2014-03-20
• Subjects: Therapeutic applications, including brachytherapy -- Monte Carlo methods -- Dose‐volume analysis; brain -- dosimetry -- linear accelerators -- liver -- lung -- Monte Carlo methods -- radiation therapy; intermediate energy -- 4pi radiotherapy -- non‐coplanar -- inverse optimization; Radiation therapy -- Linear accelerators -- Scintigraphy; Dosimetry -- Lungs -- Linear accelerators -- Radiation therapy -- Cancer -- Liver -- Photons -- X‐rays -- Intensity modulated radiation therapy -- Heart; Medical physics -- Periodicals; Medical physics; Geneeskunde; Natuurkunde; Toepassingen; Biophysics; Periodicals; Periodicals; Electronic journals; 610.153
• DOI: 10.1118/1.4868464
• Languages: English
• ISSNs: 0094-2405

Abstract

Abstract : Purpose: : To investigate the feasibility of using intermediate energy 2 MV x‐rays for extracranial robotic intensity modulated radiation therapy. Methods: : Two megavolts flattening filter free x‐rays were simulated using the Monte Carlo code MCNP (v4c). A convolution/superposition dose calculation program was tuned to match the Monte Carlo calculation. The modeled 2 MV x‐rays and actual 6 MV flattened x‐rays from existing Varian Linacs were used in integrated beam orientation and fluence optimization for a head and neck, a liver, a lung, and a partial breast treatment. A column generation algorithm was used for the intensity modulation and beam orientation optimization. Identical optimization parameters were applied in three different planning modes for each site: 2, 6 MV, and dual energy 2/6 MV. Results: : Excellent agreement was observed between the convolution/superposition and the Monte Carlo calculated percent depth dose profiles. For the patient plans, overall, the 2/6 MV x‐ray plans had the best dosimetry followed by 2 MV only and 6 MV only plans. Between the two single energy plans, the PTV coverage was equivalent but 2 MV x‐rays improved organs‐at‐risk sparing. For the head and neck case, the 2MV plan reduced lips, mandible, tongue, oral cavity, brain, larynx, left and right parotid gland mean doses by 14%, 8%, 4%, 14%, 24%, 6%, 30% and 16%, respectively. For the liver case, the 2 MV plan reduced the liver and body mean doses by 17% and 18%, respectively. For the lung case, lung V20, V10, and V5 were reduced by 13%, 25%, and 30%, respectively. V10 of heart with 2 MV plan was reduced by 59%. For the partial breast treatment, the 2 MV plan reduced the mean dose to the ipsilateral and contralateral lungs by 27% and 47%, respectively. The mean body dose was reduced by 16%. Conclusions: : The authors showed the feasibility of using flattening filter free 2 MV x‐rays for extracranial treatments as evidenced by equivalent or superior dosimetry compared to 6 MV plans using the same inverse noncoplanar intensity modulated planning method.