Anatomical deformation due to horizontal rotation: towards gantry-free radiation therapy.

This study aims to understand and quantify anatomical deformations caused by horizontal rotation with scan sequences sufficiently short to facilitate integration into an MRI-guided workflow.
 
 Rigid and non-rigid pelvic deformations due to horizontal rotation were quantified for a cohort of 8 healthy volunteers using a bespoke patient rotation system and a clinical MRI scanner. For each volunteer a reference scan was acquired at 0° followed by sequential faster scans in 45° increments through to 360°. All fast scans were registered to the 0° image via a 3-step process: First, images were aligned using MR visible couch markers. Second, the scans were pre-processed then rigidly registered to the 0° image. Third, the rigidly registered scans were non-rigidly registered to the 0° image to assess soft tissue deformation. The residual differences after rigid and non-rigid registration were determined from the transformation matrix and the deformation vector field, respectively.
 
 The rigid registration yielded mean rotations of ≤ 2.5° in all cases. The average 3D translational magnitudes range was 5.8 ± 2.9 mm - 30.0 ± 11.0 mm. Translations were most significant in the left-right direction. Smaller translations were observed in the anterior-posterior and superior-inferior directions. The maximum deformation magnitudes range was: 10.0 ± 0.9 mm - 28.0 ± 2.8 mm and average deformation magnitud...
Source: Physics in Medicine and Biology - Category: Physics Authors: Tags: Phys Med Biol Source Type: research

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Source: Radiotherapy and Oncology - Category: Radiology Authors: Tags: Original Article Source Type: research
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Source: Physics in Medicine and Biology - Category: Physics Authors: Tags: Phys Med Biol Source Type: research
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Source: Physics in Medicine and Biology - Category: Physics Authors: Tags: Phys Med Biol Source Type: research
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