A cinematic magnetic resonance imaging study of milk of magnesia laxative and an antiflatulent diet to reduce intrafraction prostate motion.
OBJECTIVE
To determine the reduction of prostate motion during a typical radiotherapy (RT) fraction from a bowel regimen comprising an antiflatulent diet and daily milk of magnesia.


METHODS
Forty-two patients with T1c-T2c prostate cancer voided the bladder and rectum before three cinematic magnetic resonance imaging scans obtained every 9 s for 9 min in a vacuum immobilization device. The MRIs were at baseline without bowel regimen (MRI-BL), before CT planning with bowel regimen (MRI-CT), and before a randomly assigned RT fraction (1-42) with bowel regimen (MRI-RT). A single observer tracked displacement of the posterior midpoint (PM) of the prostate. The primary endpoints were comparisons of the proportion of time that the PM was displaced >3 mm (PTPM3) from its initial position, and the secondary endpoints were comparisons of the reduction of initial rectal area, with and without the bowel regimen.


RESULTS
The mean rectal area was: 13.5 cm(2) at MRI-BL, 12.7 cm(2) at MRI-CT, and 12.3 cm(2) at MRI-RT (MRI-BL vs. MRI-CT, p = 0.11; MRI-BL vs. MRI-CT, p = 0.07). Moving rectal gas alone (56%) and moving gas and stool (18%) caused 74% of intrafraction prostate motion. The PTPM3 was 11.3% at MRI-BL, 4.8% at MRI-CT, and 12.0% at MRI-RT (MRI-BL vs. MRI-CT, p = 0.12; MRI-BL vs. MRI-RT, p = 0.89).


CONCLUSIONS
For subjects voiding their rectum before imaging, an antiflatulent diet and milk of magnesia laxative did not significantly reduce initial rectal area or intrafraction prostate motion.
Radiation Medicine Program, Princess Margaret Hospital and University of Toronto, Toronto, Canada.
Alan M
AM
Nichol
Padraig R
PR
Warde
Gina A
GA
Lockwood
Anna K
AK
Kirilova
Andrew
A
Bayley
Robert
R
Bristow
Juanita
J
Crook
Mary
M
Gospodarowicz
Michael
M
McLean
Michael
M
Milosevic
Tara
T
Rosewall
David A
DA
Jaffray
Charles N
CN
Catton
D000368:Aged; D003672:Defecation; D005243:Feces; D005414:Flatulence / Q000178:diet therapy*; D005740:Gases; D006801:Humans; D054368:Laxatives / Q000627:therapeutic use*; D008277:Magnesium Oxide / Q000627:therapeutic use*; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009068:Movement; D011467:Prostate; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D012007:Rectum / Q000033:anatomy & histology / Q000502:physiology; D014554:Urination
D005740:Gases; D054368:Laxatives; D008277:Magnesium Oxide