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SU‐GG‐J‐140: Online Re‐Planning Using Direct Machine Parameter Optimization: A Non‐Human Primate Lung Irradiation Study
Author(s) -
Lerma F,
Liu B,
Wang Z,
Yu C,
Yi B,
Koshy M,
Farese A,
Macvittie T
Publication year - 2008
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2961689
Subject(s) - nuclear medicine , radiation treatment planning , medicine , non human primate , radiation therapy , pneumonitis , lung , radiology , biology , evolutionary biology
Purpose: Establish the feasibility of CBCT‐based, online re‐planning using direct machine parameter optimization (DMPO) to irradiate the total lung parenchyma in non‐human primates (NHPs). A study of acute‐radiation‐exposure‐ induced pneumonitis in NHPs involves total lung irradiation (TLI) to 12.5 Gy in a single session, where acute radiation exposure may also lead to the lethal hematopoeitic and gastrointestinal subsyndromes. The latter syndromes occur at 7–8 Gy and at 12–14 Gy, respectively, 1 and 2 weeks after irradiation. Hence, high dose conformity is essential to spare bone marrow, cord and bowel. Method and Materials: An offline DMPO plan is created on a CBCT scan of the NHP several days prior to the TLI session; using seven, 6MV photon beams. TLI targets a PTV from a 1 cm expansion of lung contours, sparing tissues outside the PTV. On the day of the irradiation a new CBCT is acquired, loaded into the planning system, and contours and DMPO dose objectives are propagated from the offline plan. DMPO is executed online using the original off‐line plan as starting points and the resultant on‐line plan is compared to the offline plan, on a Philips Pinnacle 8.1v workstation. Results: Online‐ and offline‐planned DMPO plans achieve V95 > 95% coverage of the PTV, and excellent bowel sparing. However, offline‐planned DMPO delivers > 7 Gy to more than 50% of the cord volume, while online‐planned DMPO delivers < 6 Gy to more than 50 % of the cord. Online DMPO re‐optimization from scanning to the start of irradiation takes less than 45 minutes. Conclusion: Online DMPO‐based re‐planning of NHP total lung irradiations is established in support of a study of radiation‐induced pneumonitis in non‐human primates. Online‐planning on NHPs is valuable experience prior to clinical implementation in human patients.