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6 April 2007 Reproducibility of MRE shear modulus estimates
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A significant effort has been expended to measure the accuracy of the shear modulus estimates. Conversely, very little effort has been expended to establish the reproducibility of the method in a clinical context. Previously we established the reproducibility in phantoms to be 3% for repeated measurements without moving the phantom and 5% when the phantom was moved,however, the clinical reproducibility has not been demonstrated. The reproducibility of the method was estimated by scanning subjects' heels repeatedly on a GE 1.5T scanner using previously described methods. Three subjects were scanned three times on different days (termed non-consecutive) and three subjects were scanned three times in the same session without changing the position of the foot (termed consecutive). The average difference between mean values within the field of view for the non-consecutive group was 7.75% ± 3.76% and for the consecutive group it was 5.30% ± 4.16%. These values represent remarkably good reproducibility considering the 20% variation in shear modulus observed within individual heels and the several hundred percent changes observed between normal and pathologic tissues. The variation in repeated examinations was caused by four factors: positioning error between examinations accounted for 4.8%, computational noise 3.0%, and the combination of MR noise and patient motion during the examination, 5.3%. Each of these sources of variation can be reduced in relatively straightforward ways if necessary but the current level of reproducibility is sufficient for most current applications.
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John B. Weaver, Timothy B. Miller, Marvin D. Doyley, Huifang Wang, Phillip R. Perrinez, Yvonne Y. Cheung, Francis E. Kennedy, and Keith D. Paulsen "Reproducibility of MRE shear modulus estimates", Proc. SPIE 6511, Medical Imaging 2007: Physiology, Function, and Structure from Medical Images, 65111T (6 April 2007); doi: 10.1117/12.713772;

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