Dynamic MRI analysis of @entity5 and organ motion during rest and @entity1282 and margin assessment for radiotherapy of XXXX .

@entity1 @entity135 @entity5 @entity343 @entity1282
PURPOSE: To quantify swallowing frequency and @entity5 and normal structure displacements during @entity1282 using dynamic magnetic resonance imaging (MRI) and to determine planning target volume ( @entity343 ) margins to account for resting and @entity1282 in @entity1 with @entity135 ( @entity135 ). METHODS AND MATERIALS: Twenty-two @entity1 with @entity135 were imaged in the treatment position using dynamic MRI. Sagittal images were acquired. Two-dimensional displacement was analyzed using contours of normal structures and GTV drawn for one swallowing event. Deglutition-induced displacements were quantified based on position change during @entity1282 relative to preswallow structure location for anterior (A), posterior (P), superior (S), and inferior (I) directions. Additional long-time MRI series were obtained from a subset of 11 @entity1 while they were resting in order to determine swallowing frequency and duration. @entity343 margins to account for setup error, frequency and duration of @entity1282 , and resting and @entity1282 -induced GTV motion were calculated. RESULTS: Mean maximum resting displacements ranged from 1.5 to 3.1 mm for combined GTV subsites. Mean maximum swallowing GTV displacement for combined subsites ranged from 4.0 to 11.6 mm. Swallowing was nonperiodic, with a frequency ranging from 0 to 19 swallows over 12.8 min and mean swallow duration of 3.5 s. Based on the average swallowing characteristics in this cohort, the average @entity343 margins to account for setup error and @entity5 motion are estimated to be 4.7 mm anteriorly, 4.2 mm posteriorly, 4.7 mm inferiorly, and 6.0 mm superiorly. CONCLUSIONS: The measurable mean maximum resting displacement for the GTV indicates that @entity5 motion occurs even when the @entity1 is not swallowing. Nonuniform margins should be used as a standard @entity343 margin that accounts for setup error and @entity5 motion in radiotherapy of @entity135 unless adaptive radiotherapy with respect to intrafraction @entity5 motion is performed. The @entity343 margin can be individualized to a single @entity1 's swallowing characteristics or calculated as an average based on the swallowing data from the cohort.
