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.
Nichol
Alan M
AM
Radiation Medicine Program, Princess Margaret Hospital and University of Toronto, Toronto, Canada.
Warde
Padraig R
PR
Lockwood
Gina A
GA
Kirilova
Anna K
AK
Bayley
Andrew
A
Bristow
Robert
R
Crook
Juanita
J
Gospodarowicz
Mary
M
McLean
Michael
M
Milosevic
Michael
M
Rosewall
Tara
T
Jaffray
David A
DA
Catton
Charles N
CN
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