S. Hagiwara

Accuracy and precision study in vitro for peripheral quantitative computed tomography.

We evaluated the accuracy and precision of a peripheral quantitative computed tomography (pQCT) scanner, the Stratec XCT-960, using 12 human cadaveric forearms. The accuracy was determined by comparing the total bone mineral content (BMC) with the ash weight (AW). We scanned and ashed three consecutive slices (thickness 2.5 mm) at the standard position (s-position) and at 2.5 mm both proximal and distal to the s-position. The correlation coefficient between the AW and total BMC using slices at the s-position wasr=0.87 with an accuracy error (random component) of 15.5%. The correlation coefficient using all slices wasr=0.90 with an accuracy error of 14.3%. The correlation coefficient improved tor=0.95 with an accuracy error of 9.7% after averaging the results of all three slices for each forearm. The short-term precision error expressed as the coefficient of variation (CV) of bone mineral density (BMD) and BMC was determined by measuring the forearms five times either with repositioning or without repositioning. The CVs with repositioning were 2.77 and 1.15 for total BMD and BMC, 1.85 for trabecular BMD; without repositioning they were 0.29, 0.58 and 0.69 respectively. To further evaluate the influence of positioning, additional scans were performed at 1, 2 and 5 mm proximal, and 1 and 2 mm distal to the s-position. BMD and BMC were greatly influenced by the scan location; for example, the percentage differences in trabecular BMD 1 mm distal and proximal relative to the s-position were 2.5%±5.1% and 0.18%±6.3%, respectively. The Stratec XCT-960 appears to be a moderately accurate and highly precise scanner with potential usefulness for evaluating BMC and BMD of ultradistal radius.

Accuracy and diagnostic sensitivity of radiographic absorptiometry of the second metacarpal.

The accuracy of a radiographic absorptiometry (RA) technique called digital image processing (DIP), discriminative ability of RA for osteoporotic fracture, and the relationship between RA and dual X-ray absorptiometry (DXA) of the spine and forearm were evaluated. We measured 16 cadaver hands, 32 healthy non-black premenopausal women, 39 healthy non-black postmenopausal women, and 35 non-black osteoporotic postmenopausal females. The overall correlation between the ash weights of the entire metacarpal and the DIP values was excellent (r = 0.954, P < 0.001, SEE = 0.14, CV = 6.4%). Short-term precision error of DIP was 3.5%. Age-related bone loss determined by DIP is comparable to that of spinal and forearm DXA: annual BMD decreases were 0.46% for DIP, 0.45% for forearm, and 0.32% for the spine. DIP of the 2nd metacarpal shows a gradient of risk for spinal fracture only slightly below that of forearm DXA, but substantially below that of spinal DXA. Age-adjusted odds ratios were 1.81 for RA, 2.45 for spinal DXA, and 1.94 for forearm DXA.

Perspectives on bone densitometry: Past/present/future

Osteoporosis is defined as a decrease in bone mass and structural changes in bone leading to an increased fracture incidence. Therefore, early diagnosis in terms of prophylaxis and treatment are of great interest. Over the past several decades there has been considerable progress in the development and application of non-invasive methods of bone mass measurements or bone densitometry. This article reviews basic methodology and developments in bone densitometry including the early approaches like radiogrammetry, photo densitometry, neutron activation analysis and compton scattering techniques, present methods like single and dual x-ray absorptiometry and quantitative computed tomography, and recent developments like quantitative ultrasound, magnetic resonance techniques and structural analysis. The widespread interest in bone densitometry will initiate further improvement of established methods and development of new applications.