Accuracy of cartilage and subchondral bone spatial thickness distribution from MRI.
OBJECTIVE
To assess three-dimensional measurement accuracy of articular cartilage (AC) and subchondral bone (SB) thickness from MRI.


METHODS
A computer program was used to calculate AC and SB thickness from MRI (three-dimensional spoiled gradient echo (SPGR),.31-mm resolution, 1-mm slice thickness) of six adult femoral heads. Specimens were imaged in five anatomical planes ranging between +30 degrees to -30 degrees from neutral and cut into 2-mm thick sections along the five anatomical planes. Faxitron x-ray was used to produce microradiographic (.05-mm resolution) images of the sections.


RESULTS
In-plane measurement accuracy was.165 +/-.108 mm for AC thickness and.387 +/-.174 mm for SB thickness. Taking into account chemical-shift misregistration in SB thickness, accuracy of measurements improved to.213 +/- 128 mm. Out-of-plane (three-dimensional) thickness accuracy of the model, assessed by numerical simulation, was.015 mm. However, three-dimensional thickness errors in specimens were.319 +/-.256 mm for AC and.253 +/-.183 mm for SB thickness.


CONCLUSIONS
Errors in three-dimensional AC thickness were attributed to volume-averaging effects caused by oblique intersection of the image plane with the joint surface. Errors in three-dimensional SB thickness were attributed to chemical-shift artifact. We conclude that accuracy of AC thickness is within clinically acceptable standards but that more sophisticated pulse sequences are needed to improve the measurement of SB thickness.
McGibbon
Chris A
CA
Department of Orthopaedic Surgery, Biomotion Laboratory and MGH Institute of Health Professions, Graduate Programs in Physical Therapy, Harvard Medical School, Massachusetts General Hospital, Boston, Massachusetts 02114, USA. cmcgibbon@partners.org
Bencardino
Jenny
J
Yeh
Eren D
ED
Palmer
William E
WE
D000328:Adult; D002356:Cartilage / Q000033:anatomy & histology*; D005270:Femur Head / Q000033:anatomy & histology*; D006801:Humans; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008954:Models, Biological; D015203:Reproducibility of Results; D012984:Software