In vitro assessment of a 3D segmentation algorithm based on the belief functions theory in calculating renal volumes by MRI.
OBJECTIVE
Renal volumetry is an essential part of split renal function assessment in MR urography. The aim of this study was to assess the accuracy and repeatability of a 3D segmentation algorithm based on the belief functions theory for calculating renal volumes from MR images.


METHODS
The true volumes of 20 animal kidneys of various sizes were obtained by fluid displacement. Each kidney was examined using two different MR units. Three-dimensional proton density-weighted acquisitions with an incremental slice thickness were performed. The MR volume was then measured with a segmentation algorithm based on the belief functions theory. Two independent observers performed all segmentations twice. Accuracy, intraobserver variability, and interobserver variability were evaluated by the Bland-Altman method. The number and type of manual corrections were recorded as well as the entire processing time.


RESULTS
The mean renal volume estimated by fluid displacement was 114 mL (range, 38-224 mL). With regard to the renal volumes obtained from assessments of adjacent axial MR images, the maximal SDs of the difference were 2.2 mL (accuracy), 0.6 mL (intraobserver variability), and 1.8 mL (interobserver variability). Segmentation of axial slices provided better accuracy and reproducibility than coronal slices. Overlapped coronal slices yielded poor results because of the partial volume effect. The mean processing time including optional manual modifications was less than 75 seconds.


CONCLUSIONS
The belief functions theory can be considered an accurate and reproducible mathematic method to assess renal volume from MR adjacent images.
Vivier
Pierre-Hugues
PH
Department of Radiology, University Hospital of Rouen, Irue de Germont, Rouen Cedex F-76031, France.
Dolores
Michael
M
Gardin
Isabelle
I
Zhang
Peng
P
Petitjean
Caroline
C
Dacher
Jean-Nicolas
JN
D000465:Algorithms; D000818:Animals; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D066298:In Vitro Techniques; D007668:Kidney / Q000033:anatomy & histology*; D009929:Organ Size; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012756:Sheep; D013552:Swine