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Quantitative Magnetic Resonance Imaging in the Calcaneus and Femur of Women With Varying Degrees of Osteopenia and Vertebral Deformity Status
Author(s) -
Wehrli Felix W.,
Hilaire Luna,
FernándezSeara Maria,
Gomberg Bryon R.,
Song Hee Kwon,
Zemel Babette,
Loh Louise,
Snyder Peter J.
Publication year - 2002
Publication title -
journal of bone and mineral research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.882
H-Index - 241
eISSN - 1523-4681
pISSN - 0884-0431
DOI - 10.1359/jbmr.2002.17.12.2265
Subject(s) - calcaneus , medicine , osteopenia , osteoporosis , bone mineral , femur , bone density , deformity , magnetic resonance imaging , vertebra , heel , tibia , anatomy , nuclear medicine , orthodontics , radiology , surgery
Quantitative magnetic resonance imaging (QMRI) allows measurement of two parameters that are related to the integrity of the trabecular bone: R 2 , the rate constant of the free induction signal, and trabecular bone volume fraction (BVF), the counterpart of apparent density. In this work, R 2 and BVF were measured in 68 women (mean age, 58.2 ± 9.5 years) of varying spinal bone mineral density (BMD) T scores (mean, −1.37 ± 1.54) and vertebral fracture status on a commercial 1.5 T whole‐body imager using customized image acquisition and processing techniques. Twenty‐five of the patients had vertebral fractures, characterized by the total cumulative deformity burden exceeding 200%. R 2 was measured in the calcaneus and proximal femur and BVF could be measured in the calcaneus only. On a pixel‐by‐pixel basis, calcaneal R 2 and BVF within each subject were highly positively correlated ( r 2 = 0.61 ± 0.11) but the correlation of region‐of‐interest (ROI) means for different calcaneal sites among patients was weaker ( r 2 = 0.34; p < 0.0001). The strongest discriminator of vertebral deformity was R 2 of the calcaneus, which was lower in the fracture group, consistent with lower trabecular density. Among the calcaneal sites examined, the subtalar region, a location characterized by dense nearly horizontal trabeculae that transmit the stresses imparted by body weight from the tibia to the heel, best discriminated the two groups ( p = 0.0001), with 77% diagnostic accuracy as determined from the area under the receiver operating characteristic (ROC) curve (compared with 66% for vertebral BMD). The cavum calcanei, an anterior site of low trabecular density, and the tuber calcanei (the location ordinarily used for ultrasound measurements) also had significantly reduced R 2 in the fracture group ( p < 0.005 and p = 0.01, respectively). The R 2av , computed as the average of all pixels in the calcaneus, was a strong discriminator as well ( p < 0.005). On the other hand, calcaneal BVF was only marginally discriminating ( p = 0.05). Among the BMD sites examined, the lumbar spine (average L1‐L4) was significant ( p = 0.005, 66% diagnostic accuracy), as was the femoral neck ( p = 0.01). The data suggest the calcaneus to be suited as a surrogate site to assess vertebral osteoporosis and that R 2 is sensitive to alterations in bone quality not captured by density.