Practical approaches to four-dimensional heavy-charged-particle lung therapy.
We have developed new design algorithms for compensating boli to facilitate the implementation of four-dimensional charged-particle lung therapy in clinical applications. Four-dimensional CT (4DCT) data for eight lung cancer patients were acquired with a 16-slice CT under free breathing. Six compensating boli were developed that may be categorized into three classes: (1) boli-based on contoured gross tumor volumes (GTV) from a 4DCT data set during each respiratory phase, subsequently combined into one (GTV-4DCT bolus); (2) boli-based on contoured internal target volume (ITV) from image-processed 3DCT data only [temporal-maximum-intensity-projection (TMIP)/temporal-average-intensity-projection (TAIP)] with calculated boli (ITV-TMIP and ITV-TAIP boli); and (3) boli-based on contoured ITV utilizing image-processed 3DCT data, applied to 4DCT for design of boli for each phase, which were then combined. The carbon beam dose distribution within each bolus was calculated as a function of time and compared to plans in which respiratory-ungated/gated strategies were used. The GTV-4DCT treatment plan required a prohibitively long time for contouring the GTV manually for each respiratory phase, but it delivered more than 95% of the prescribed dose to the target volume. The TMIP and TAIP treatments, although more time-efficient, resulted in an unacceptable excess dose to normal tissues and underdosing of the target volume. The dose distribution for the ITV-4DCT bolus was similar to that for the GTV-4DCT bolus and required significantly less practitioner time. The ITV-4DCT bolus treatment plan is time-efficient and provides a high-quality dose distribution, making it a practical alternative to the GTV-4DCT bolus treatment plan.
Mori
Shinichiro
S
Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Anagawa, Chiba, Japan. shinshin@nirs.go.jp
Wu
Ziji
Z
Folkert
Michael R
MR
Kumagai
Motoki
M
Dobashi
Suguru
S
Sugane
Toshio
T
Baba
Masayuki
M
D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D002244:Carbon / Q000627:therapeutic use; D056973:Four-Dimensional Computed Tomography; D063193:Heavy Ion Radiotherapy; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology / Q000532:radiotherapy*; D008875:Middle Aged; D058958:Organs at Risk / Q000528:radiation effects; D011879:Radiotherapy Dosage; D011881:Radiotherapy, Computer-Assisted / Q000379:methods*; D012119:Respiration; D047368:Tumor Burden
D002244:Carbon
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