Large prostate motion produced by anal contraction.
OBJECTIVE
The aim of this study was to define the effects of voluntary anal contraction on prostate motion in an experimental setting.


METHODS
Thirty-eight patients (median age, 76 years) with prostate cancer underwent thin-slice computed tomography (CT) in the vicinity of the prostate before and after active anal contraction. Three-dimensional displacement of the pelvis and prostate was measured.


RESULTS
Mean (±standard deviation, SD) overall displacement of the prostate due to anal contraction was 0.3±1.4 mm to the right, 9.3±7.8 mm to the anterior, and 5±4 mm to the cranial direction. Mean displacement of the pelvis was 0.5±1.8 mm to the right, 4.1±7.1 mm to the anterior, and 1±3 mm to the cranial direction. Mean displacement of the prostate relative to the pelvis was 0.1±1.1 mm to the left, 5.2±3.3 mm to the anterior, and 4±4 mm to the cranial direction.


CONCLUSIONS
Voluntary anal contraction within an experimental setting induces large prostate and bone motion, mainly in the anterior and cranial directions. The frequency and magnitude of actual anal contractions during radiotherapy for prostate cancer need to be determined.
University of Yamanashi, Japan. honishi@yamanashi.ac.jp
Hiroshi
H
Onishi
Kengo
K
Kuriyama
Takafumi
T
Komiyama
Kan
K
Marino
Masayuki
M
Araya
Ryo
R
Saito
Shinichi
S
Aoki
Yoshiyasu
Y
Maehata
Licht
L
Tominaga
Naoki
N
Sano
Mitsuhiko
M
Oguri
Kojiro
K
Onohara
Iori
I
Watanabe
Tsuyota
T
Koshiishi
Kazuhiko
K
Ogawa
Tsutomu
T
Araki
D000368:Aged; D000369:Aged, 80 and over; D001003:Anal Canal / Q000503:physiopathology*; D006801:Humans; D008297:Male; D009038:Motion; D009119:Muscle Contraction; D011467:Prostate / Q000502:physiology*; D011471:Prostatic Neoplasms / Q000503:physiopathology / Q000532:radiotherapy*