Quantitative high-resolution magnetic resonance imaging reveals structural implications of renal osteodystrophy on trabecular and cortical bone.
OBJECTIVE
To explore the potential role of micro-magnetic resonance imaging (micro-MRI) for quantifying trabecular and cortical bone structural parameters in renal osteodystrophy (ROD), a multifactorial disorder of bone metabolism, traditionally evaluated by bone biopsy.


METHODS
Seventeen hemodialysis patients (average PTH level = 502 +/- 415 microg/liter) were compared with 17 age-, gender-, and body mass index (BMI)-matched control subjects. The average dialysis duration for the patients was 5.5 years (range = 0.96-18.2 years). Three-dimensional (3D) fast large-angle spin-echo (FLASE) MR images of the distal tibia (voxel size = 137 x 137 x 410 microm(3)) were processed to yield bone volume fraction (BV/TV). From a skeletonized representation of the trabecular bone network, the topology of each bone voxel was determined providing surface and curve voxel densities (SURF and CURV) and the topological erosion index (EI). Further, high-resolution two-dimensional (2D) spin-echo images were collected at the tibial midshaft for measurement of cortical bone cross-sectional area (CCA), relative CCA expressed as a percentage of total bone area (RCA), and mean cortical thickness (MCT).


RESULTS
The data show both RCA and MCT to be lower in the patients (61.2 vs. 69.1%, P = 0.008, and 4.53 vs. 5.19 mm, P = 0.01). BV/TV and SURF were lower, while EI was increased in the patients, although these differences were not quite significant (P = 0.06-0.09). All of the cortical and trabecular findings are consistent with increased bone fragility.


CONCLUSIONS
The data suggest that micro-MRI may have potential to characterize the structural implications of metabolic bone disease, potentially providing a noninvasive tool for the evaluation of therapies for ROD.
Wehrli
Felix W
FW
Laboratory for Structural NMR Imaging, Department of Radiology, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania 19104, USA. wehrli@uphs.upenn.edu
Leonard
Mary B
MB
Saha
Punam K
PK
Gomberg
Bryon R
BR
D000328:Adult; D015992:Body Mass Index; D001842:Bone and Bones / Q000473:pathology*; D012080:Chronic Kidney Disease-Mineral and Bone Disorder / Q000175:diagnosis*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male