Repeatability of functional MRI for conformal avoidance radiotherapy planning.

Purpose: To establish the repeatability of functional magnetic resonance imaging (fMRI) examinations in order to develop an appropriate margin for functional organs at risk (fOAR) in the radiotherapy planning process.
Materials and Methods: This work investigates the variability of motor cortex activation in the left and right hemispheres of 15 normal subjects. The uncertainty of the absolute position and volume of the activation was determined for each volunteer by repeating the fMRI examination three times in a single scan session.
Results: Our study proposes the use of 2.9 mm and 2.2 mm margins for the left and right motor cortices, respectively.
Conclusion: From the sample of 15 volunteers we established an appropriate planning margin that is considered to represent the uncertainty in spatially measuring the fOAR for a single fMRI examination. The work will be of interest to anyone investigating the clinical robustness of fMRI.
((c) 2006 Wiley-Liss, Inc.)