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Gastrointestinal Imaging |
1 From the Diagnostic Radiology Unit and Center for Anatomical, Functional and Molecular Imaging Research (L.H., I.L.A., L.A., B.E.V.B.) and Department of Surgery (J.L.), Université Catholique de Louvain, Saint-Luc University Hospital, Ave Hippocrate 10, B-1200 Brussels, Belgium; and Departments of Biomedical Engineering (Z.C.) and Electrical Engineering and Computer Science (B.M.D.), Vanderbilt University, Nashville, Tenn. Received November 7, 2003; revision requested January 28, 2004; final revision received April 13; accepted May 12. Supported in part by grant 3.4578.00 from the Fonds National de la Recherche Scientifique (Belgium) and by NIH grant 4R33CA09135203. Address correspondence to L.H. (e-mail: hermoye@rdgn.ucl.ac.be).
PURPOSE: To compare the accuracy and repeatability of a semiautomatic segmentation algorithm with those of manual segmentation for determining liver volume in living liver transplant donors at magnetic resonance (MR) imaging.
MATERIALS AND METHODS: The institutional review board approved this retrospective study and waived the requirement for informed consent. The semiautomatic segmentation algorithm is based on geometric deformable models and the level-set technique. It entails (a) placing initialization circle(s) on each image section, (b) running the algorithm, (c) inspecting and possibly manually modifying the contours obtained with the segmentation algorithm, and (d) placing lines to separate the liver segments. For 18 living donors (eight men and 10 women; mean age, 34 years; age range, 2546 years), two observers each performed two semiautomatic and two manual segmentations on contrast materialenhanced T1-weighted MR images. Each measurement was timed. Actual graft weight was measured during surgery. The time needed for manual and that needed for semiautomatic segmentation were compared. Accuracy and repeatability were evaluated with the Bland-Altman method.
RESULTS: Mean interaction time was reduced from 25 minutes with manual segmentation to 5 minutes with semiautomatic segmentation. The mean total time for the semiautomatic process was 7 minutes 20 seconds. Differences between the actual volume and the estimated volume ranged from 223 to +123 mL for manual segmentation and from 214 to +86 mL for semiautomatic segmentation. The 95% limits of agreement for the ratio of actual graft volume to estimated graft volume were 0.686 and 1.601 for semiautomatic segmentation and 0.651 and 1.957 for manual segmentation. Semiautomatic segmentation improved estimation in 15 of 18 cases. Inter- and intraobserver repeatability was higher with semiautomatic segmentation.
CONCLUSION: Use of the semiautomatic segmentation algorithm substantially reduces the time needed for volumetric measurement of liver segments while improving both accuracy and repeatability.
© RSNA, 2004
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