Effect of patient positioning on carbon-ion therapy planned dose distribution to pancreatic tumors and organs at risk

Kentaro Miki; Mai Fukahori; Motoki Kumagai; Shigeru Yamada; Shinichiro Mori

doi:10.1016/j.ejmp.2016.12.001

Effect of patient positioning on carbon-ion therapy planned dose distribution to pancreatic tumors and organs at risk

Phys Med. 2017 Jan:33:38-46. doi: 10.1016/j.ejmp.2016.12.001. Epub 2016 Dec 18.

Authors

Kentaro Miki¹, Mai Fukahori¹, Motoki Kumagai², Shigeru Yamada¹, Shinichiro Mori³

Affiliations

¹ Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan.
² Particle Therapy Division, Research Center for Innovative Oncology, National Cancer Center East, 6-5-1 Kashiwa, Chiba 277-8577, Japan.
³ Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan. Electronic address: [email protected].

PMID: 28003135
DOI: 10.1016/j.ejmp.2016.12.001

Abstract

Purpose: Pancreatic tumor treatment dose distribution variations associated with supine and prone patient positioning were evaluated.

Methods: A total of 33 patients with pancreatic tumors who underwent CT in the supine and prone positions were analyzed retrospectively. Gross tumor volume (GTV), planning target volume (PTV), and organs at risk (OARs) (duodenum and stomach) were contoured. The prescribed dose of 55.2Gy (RBE) was planned from four beam angles (0°, 90°, 180°, and 270°). Patient collimator and compensating boli were designed for each field. Dose distributions were calculated for each field in the supine and prone positions. To improve dose distribution, patient positioning was selected from supine or prone for each beam field.

Results: Compared with conventional beam angle and patient positioning, D2cc of 1st-2nd portion of duodenum (D1-D2), 3rd-4th portion of duodenum (D3-D4), and stomach could be reduced to a maximum of 6.4Gy (RBE), 3.5Gy (RBE), and 4.5Gy (RBE) by selection of patient positioning. V10 of D1-D2, D3-D4, and stomach could be reduced to a maximum of 7.2cc, 11.3cc, and 11.5cc, respectively. D95 of GTV and PTV were improved to a maximum of 6.9% and 3.7% of the prescribed dose, respectively.

Conclusions: Optimization of patient positioning for each beam angle in treatment planning has the potential to reduce OARs dose maintaining tumor dose in pancreatic treatment.

Keywords: Carbon ion radiotherapy; Dose distribution; Pancreatic cancer; Patient positioning.

MeSH terms

Adult
Aged
Aged, 80 and over
Female
Heavy Ion Radiotherapy / adverse effects*
Heavy Ion Radiotherapy / methods*
Humans
Male
Middle Aged
Organs at Risk / radiation effects*
Pancreatic Neoplasms / radiotherapy*
Patient Positioning*
Prone Position
Radiation Dosage*
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted / methods*
Retrospective Studies
Supine Position