Impact of Intrafractional Bowel Gas Movement on Carbon Ion Beam Dose Distribution in Pancreatic Radiotherapy

• Published in: International journal of radiation oncology, biology, physics Vol. 73; no. 4; pp. 1276 - 1281
• Main Authors: Kumagai, Motoki, Hara, Ryusuke, Mori, Shinichiro, Yanagi, Takeshi, Asakura, Hiroshi, Kishimoto, Riwa, Kato, Hirotoshi, Yamada, Shigeru, Kandatsu, Susumu, Kamada, Tadashi
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 15.03.2009
• Subjects: Aged; Aged, 80 and over; Bowel gas; BREATH; Carbon beam; CARBON IONS; Carbon Radioisotopes - therapeutic use; Computed tomography; COMPUTERIZED TOMOGRAPHY; Contrast Media; Female; Gases; Hematology, Oncology and Palliative Medicine; Humans; Intestines - diagnostic imaging; Intestines - physiology; Intrafractional motion; ION BEAMS; Male; Middle Aged; Movement; NEOPLASMS; PANCREAS; Pancreatic cancer; Pancreatic Neoplasms - diagnostic imaging; Pancreatic Neoplasms - radiotherapy; RADIATION DOSE DISTRIBUTIONS; RADIATION DOSES; Radiology; RADIOLOGY AND NUCLEAR MEDICINE; RADIOTHERAPY; Radiotherapy Dosage; Radiotherapy Planning, Computer-Assisted; Respiration; SMALL INTESTINE; Tomography, Spiral Computed - methods; Bowel gas; Computed tomography; Radiotherapy; Intrafractional motion; Pancreatic cancer; Carbon beam
• ISSN: 0360-3016; 1879-355X; 1879-355X
• DOI: 10.1016/j.ijrobp.2008.10.055

To assess carbon ion beam dose variation due to bowel gas movement in pancreatic radiotherapy. Ten pancreatic cancer inpatients were subject to diagnostic contrast-enhanced dynamic helical CT examination under breath-holding conditions, which included multiple-phase dynamic CT with arterial, venous, and delayed phases. The arterial–venous phase and arterial–delayed phase intervals were 35 and 145 s, respectively. A compensating bolus was designed to cover the target obtained at the arterial phase. Carbon ion dose distribution was calculated by applying the bolus to the CT data sets at the other two phases. Dose conformation to the clinical target volume was degraded by beam overshoot/undershoot due to bowel gas movement. The D95 for clinical target volume was degraded from 98.2% (range, 98.0–99.1%) of the prescribed dose to 94.7% (range, 88.0–99.0%) at 145 s. Excessive dosing to normal tissues varied among tissues and was, for example, 12.2 GyE/13.1 GyE (0 s/145 s) for the cord and 38.8 GyE/39.8 GyE (0 s/145 s) for the duodenum. The magnitude of beam overshoot/undershoot was particularly exacerbated from the anterior and left directions. Bowel gas movement causes dosimetric variation to the target during treatment for radiotherapy. The effect of bowel gas movement varies with beam angle, with greatest influence on the anterior–posterior and left–right beams.