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Retrospective Reconstruction of 3D Radial MRI Data to Evaluate the Effect of Abdominal Compression On 4D Abdominal Organ Motion

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B Stemkens

B Stemkens1*, R Tijssen1 , B Denis de Senneville1,2 , J Lagendijk1 , C van den Berg1 , (1) University Medical Center Utrecht, Utrecht, the Netherlands (2) CNRS/University Bordeaux 1/INRIA, Bordeaux, France


TH-A-BRF-7 Thursday 7:30AM - 9:30AM Room: Ballroom F

To assess the immobilization effect of an abdominal corset on the spatial and temporal motion characteristics of the pancreas and kidneys using a novel 4D-MRI method.

Four healthy subjects were scanned with and without a fiberglass corset on a 1.5T clinical MRI. For each subject the best fitting corset was chosen from a range of available corsets. For one subject a custom-fit corset was used. The free-breathing 4D-MRI scan consisted of a balanced-TFE sequence with radial in-plane sampling (TE/TR=1.45ms/3.0ms, FA=30°, FOV=350x350x96mm³, voxelsize=2.0x2.0x4.0mm³, 30 dynamics, Tacq=10m17s). Turbo direction was along kz acquiring all kz lines within a single TFE shot (shot duration 93ms). A respiratory diaphragm navigator was interleaved with the TFE shots to acquire the breathing signal, which was used to retrospectively assign each k-space segment to one of the ten respiratory phases. A 3D optical flow algorithm was used to estimate the non-rigid displacement between the respiratory phases. The respiration frequency changes were assessed by means of power spectrum analysis (PSA) of the navigator signal.

Image quality was adequate for delineation and registration. Cranio-caudal motion calculated by the 3D optical flow algorithm correlated with the navigator signal, but inter-organ motion amplitude variation was observed between all organs. Motion reduction induced by the corset was primarily observed in the CC-direction, but varied substantially across the subjects. Our method additionally showed that the antero-posterior motion was slightly increased for both kidneys in all subjects (left: 1.2mm, right: 0.8mm). Visual inspection of PSA showed no trend in breathing frequency changes.

We have demonstrated a novel, navigator based, free-breathing 4D-MRI technique to assess the immobilization effect of abdominal compression in four healthy subjects. This technique can be clinically used to assess the effect of a custom-fit corset on the motion of both tumor motion and surrounding organs at risk.

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