Differences in abdominal organ movement between supine and prone positions measured using four-dimensional computed tomography.
OBJECTIVE
To analyze the differences in intrafractional organ movement throughout the breathing cycles between the supine and prone positions using four-dimensional computed tomography (4D CT).


METHODS
We performed 4D CT on nine volunteers in the supine and prone positions, with each examinee asked to breathe normally during scanning. The movement of abdominal organs in the cranio-caudal (CC), anterior-posterior (AP) and right-left (RL) directions was quantified by contouring on each phase between inspiration and expiration.


RESULTS
The mean intrafractional motions of the hepatic dome, lower tip, pancreatic head and tail, both kidneys, spleen, and celiac axis in the supine/prone position were 17.3/13.0, 14.4/11.0, 12.8/8.9, 13.0/10.0, 14.3/12.1, 12.3/12.6, 11.7/12.6 and 2.2/1.8mm, respectively. Intrafractional movements of the liver dome and pancreatic head were reduced significantly in the prone position. The CC directional excursions were major determinants of the 3D displacements of the abdominal organs. Alteration from the supine to the prone position did not change the amount of intrafractional movements of kidneys, spleen, and celiac axis.


CONCLUSIONS
There was a significant reduction in the movements of the liver and pancreas during the prone position, especially in the CC direction, suggesting possible advantage of radiotherapy to these organs in this position.
Department of Radiation Oncology, Asan Medical Center, University of Ulsan, 388-1 PoongNap-Dong, SongPa-Gu, Seoul, Republic of Korea.
Young Seok
YS
Kim
Sung Ho
SH
Park
Seung Do
SD
Ahn
Jeong Eun
JE
Lee
Eun Kyung
EK
Choi
Sang-wook
SW
Lee
Seong Soo
SS
Shin
Sang Min
SM
Yoon
Jong Hoon
JH
Kim
D000005:Abdomen / Q000502:physiology*; D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D009068:Movement; D016684:Prone Position; D011860:Radiography, Abdominal; D012119:Respiration; D016683:Supine Position; D014057:Tomography, X-Ray Computed / Q000379:methods*