Cross calibration of Hologic QDR2000 and GE lunar prodigy for whole body bone mineral density and body composition measurements.

The objective of this study was to undertake an in vivo cross calibration of body composition, whole body bone mineral content (BMC) and bone mineral density (BMD) between a Hologic QDR2000 and a GE Healthcare Lunar Prodigy. Twenty-one subjects attending for routine bone densitometry were recruited to the study (19 female and 2 male, aged 30-79 yr). Phantom cross calibrations were carried out using the Bio-Imaging Variable Composition Phantom (VCP) for percentage fat (%fat) and the Bona Fide Phantom (BFP) for BMD. There was no significant difference in whole body lean body mass between the QDR2000 and the Prodigy. Fat mass (FM) and %fat were significantly higher on the QDR2000. BMC and whole body BMD were significantly higher on Prodigy. As the BMC increased, so did the difference between the 2 instruments. The VCP did not provide an adequate cross calibration of %fat compared with in vivo. The BFP provided a good cross calibration of whole body BMD compared with in vivo. The results suggest that the partitioning of the soft tissue component between lean and fat in the 2 instruments is systematically different. The variation between instruments from the same and different manufacturers reported in the literature varies widely, as does the comparison with criterion methods. This makes it difficult to generalize the results of this study to other centers and it is recommended that each center would have to cross calibrate when changing equipment.

Heat-insoluble cryoglobulin in a patient with essential type II cryoglobulinemia and cryoglobulin-occlusive membranoproliferative glomerulonephritis: case report and literature review.

BACKGROUND: A type of heat-insoluble cryoglobulin has been rarely reported and poorly understood. We report the case of a 79 y-old female who was admitted to hospital due to edema and renal failure. METHODS: Serial biochemical, immunological, and histological investigations were conducted. RESULTS: This patient had elevated serum urea and creatinine with positive rheumatoid factor and low serum C3 and C4. Her serum was positive for cryoglobulin at 4 degrees C. The precipitate did not dissolve at 37 degrees C until it was heated to 56 degrees C. Electrophoresis of the cryoglobulin demonstrated a monoclonal spike in the gamma region characterized as IgG-kappa and polyclonal IgM by immunofixation. Bone marrow aspiration showed presence of 5% plasma cells. Histological examination of renal biopsy revealed a diffuse increase in mesangial matrix, cellularity and endocapillary proliferation. Numerous monocyte/macrophages were present within mesangium and capillary lumina. Focal double contouring of glomerular basement membrane with subendothelial deposits and "hyaline thrombi" were noted. Accordingly, a type II heat-insoluble cryoglobulinemia associated with membranoproliferative glomerulonephritis and monoclonal gammopathy of undetermined significance was made. CONCLUSIONS: The unusual heat-insoluble cryoglobulins may indicate severe clinical consequence. Proper laboratory procedure and careful examination of cryoglobulin will assure early recognition and detection of heat-insoluble cryoglobulins.

Mobile PET in the UK: legislative, regulatory and cost-effectiveness considerations.

Mobile PET/CT or mobile stand alone PET, is becoming more widely available throughout the developed world, allowing many small and medium-sized hospitals that do not have the scale or financial resources to purchase the static diagnostic equipment, to benefit from this imaging technology. Before embarking on such a service, a number of legislative, logistical and administrative issues have to be addressed to ensure that a mobile PET/CT service is run with optimal efficiency and safety and in compliance with the regulations governing the use of radioactive substances. Some of these issues are similar to those encountered in operating a mobile magnetic resonance imaging scanner but there are important differences owing to the use of both sealed and open radioactive sources. This article highlights the legislative, administrative and practical issues relevant to the UK and also discusses some of the practical issues that need to be addressed to ensure the operation of a safe and effective PET service.

Cross calibration of DXA as part of an equipment replacement program.

The purpose of this study was to develop cross calibrations when replacing three dual-energy X-ray absorptiometers (GE Lunar DPXL [Madison, WI], DPXL, GE Lunar Expert [Madison, WI], Expert, Hologic QDR2000 [Waltham, MA]) with two new GE Lunar Prodigy instruments. Subjects previously scanned on the Expert or QDR2000 were transferred to Prodigy 1 and those previously scanned on the DPXL to Prodigy 2. A cohort of subjects was recalled for each old instrument, and approximately 20 subjects had lumbar spine and hip scans on each old instrument and the appropriate new instrument. An in vitro calibration was carried out using a Bona Fide Phantom (Bio-Imaging Technologies, Inc., Newtown, PA). Calibrations were fitted using a standardized principal components method. A Bland and Altman plot was used to calculate the mean difference and limits of agreement between instruments. Standardized bone mineral density (BMD) was also used to calibrate the Hologic to Prodigy 1. There was good agreement between instruments from the same manufacturer. As expected, BMD measured on the Prodigy was about 15% higher than the Hologic. Using standardized BMD to cross calibrate gave a mean difference of 3% at the lumbar spine. The limits of agreement following calibration are clinically significant, so it is not possible to apply a calibration to an individual subject for trending purposes, as the error is similar to the expected annual change in BMD, but can be used for cross calibration in clinical trials. The in vivo calibration gave better agreement than using standardized BMD. The phantom calibration was close to the in vivo calibrations at the spine, but not in some hip regions. When introducing a new instrument, a new baseline BMD has to be obtained for each subject.

Vertebral morphometry by DXA: a comparison of supine lateral and decubitus lateral densitometers.

Identification of vertebral fracture has become increasingly important in the diagnosis and management of osteoporosis. This study compares the morphometric techniques on a fan beam dual-energy X-ray absorptiometry (DXA) GE-Lunar Expert system (Expert) using a supine lateral position and a narrow fan beam GE-Lunar Prodigy system (Prodigy; GE Lunar, Madison, WI) that requires lateral decubitus positioning. Patient acceptability, image quality, observer, and equipment variability were determined. Study subjects were recruited from clinical referrals sent for a routine DXA study that included vertebral morphometry. Twenty-five patients underwent lateral vertebral assessment on both machines and completed a questionnaire on comfort and tolerability. Analysis was undertaken by two trained observers. Vertebral height, anterior/posterior height (A/P) and mid/posterior height (M/P) ratios, image quality, and prevalent fractures were assessed. There were no significant differences in patient comfort or image quality scores. More upper thoracic vertebrae could be assessed on the Expert, and good radiographic positioning was easier to achieve on the Expert. Inter-observer coefficients of variance percentage (CV%) of vertebral height was lower on the Prodigy (3.5% in the lumbar spine rising to 12.8% in the thoracic spine) than the Expert (4.2% to 16.9%). Inter-observer CV% for A/P and M/P ratios varied from 2.5% to 10.5% on the Prodigy compared with 3.5% to 12.3% on the Expert, depending on vertebral level. The variation between instruments was similar to the inter-observer CV% (anterior height: -0.11+/-1.65 mm; mid height: 0.54+/-1.51 mm; posterior height: 0.43+/-1.46 mm). There was good agreement between observers and between the Expert and Prodigy in identifying severe fractures, but lack of agreement in identifying moderate fractures. In conclusion, there was no clinically significant difference in patient comfort and image quality between the Expert and the Prodigy. The inter-observer variations in vertebral height and A/P and M/P ratios are similar to the variations between instruments. In making the change from the supine lateral to the decubitus lateral positioning, measurements of vertebral height are reproducible and patient comfort is not compromised.

The relationship between social deprivation, osteoporosis, and falls.

The aim of this study was to assess the relationship between heel BMD, risk factors for osteoporosis, falls history, and the Jarman Underprivileged Area Score in an older community population. From the general practice register, 1,187 women (mean age 70, range 60 to 94) were recruited. BMD of the heel was measured using the GE Lunar PIXI densitometer. A T-score cutoff for predicted osteoporosis at the spine or hip of -1.7 was used. A risk factor questionnaire was completed that included fracture history and falls history. The odds ratio (OR) with a 95% confidence interval (CI) was calculated for each risk factor for each quartile of Jarman score and for the diagnosis of osteoporosis. Logistic regression was used to identify the risk factors that predict lone bone mass in the heel. There were no significant differences between women in different quartiles of Jarman score in terms of age and body mass index (BMI). Women in the highest two quartiles of Jarman score (i.e., most deprived) had a significantly higher likelihood of osteoporosis (OR=1.82; 95% CI, 1.03 to 1.63; and OR=1.85; 95% CI, 1.04 to 1.64, respectively) and significantly lower BMD ( p=0.008). Women in these two quartiles were significantly more likely to have had a history of previous fracture (OR=1.66; 95% CI, 1.01 to 1.53), but there was no difference in falls history. Women in the lowest quartile (least deprived) were also significantly less likely to smoke ( p=0.011) but were not significantly different in terms of other risk factors (e.g., dietary calcium and activity). BMI, age, kyphosis, significant visual problems, and quartile of Jarman score were significant risk factors for low bone mass. Risk factors identified those with low bone mass at the heel with a sensitivity and specificity of 72%. In conclusion, women in the lowest quartile of Jarman score (i.e., least deprived) have significantly higher heel BMD compared with the rest of the population.

Changes in serum markers of bone turnover during normal pregnancy.

BACKGROUND: Maternal calcium homeostasis adapts during pregnancy to provide for the needs of the growing fetal skeleton. Wide selections of bone turnover markers are currently available to assess the changes taking place; here, data are presented on two serum-based markers. METHODS: The use of serum-based biochemical bone turnover markers during pregnancy was assessed in a cohort of 41 women recruited prior to conception. Serum N-terminal extension peptide of procollagen (P1NP) was used to monitor bone formation and serum beta-crosslaps (S-CTX) used to assess resorption. Blood samples were measured at five time points from a pre-conceptual baseline, through pregnancy, to the final sample, which was taken within 1 week of delivery. RESULTS: An initial decrease from the baseline in both P1NP and S-CTX was observed at 12 weeks; however, it is suggested that this may be due to the haemodilutional effect of pregnancy rather than a true change in bone turnover. Significant increases from the baseline of both analytes were observed by 36 weeks (P1NP, P = 0.013; S-CTX, P = 0.002), when the calcium demands of the fetus are greatest. CONCLUSIONS: This study illustrates the use of serum-based bone turnover markers to assess turnover during normal pregnancy, a time when ionizing radiation cannot be used to assess bone turnover.

A comparison of calcaneal dual-energy X-ray absorptiometry and calcaneal ultrasound for predicting the diagnosis of osteoporosis from hip and spine bone densitometry.

Peripheral densitometry is increasingly being used in the management of osteoporosis, but the optimal diagnostic thresholds have not been defined. The aim of this study was to determine the optimal T-score for peripheral dual-energy X-ray absorptiometry (pDXA) of the heel using a GE Lunar PIXI and quantitative ultrasound (QUS) of the heel using a GE Lunar Achilles Plus when compared with dual-energy X-ray absorptiometry (DXA) of central sites (spine, femoral neck, or total hip). Ninety-nine women (mean age 69 +/- 8, range 33-86 yr) referred from the metabolic bone clinic were studied. The optimal T-score for pDXA from ROC analysis was -1.7 and for QUS was -2.5. The pDXA T-score that defined the same prevalence of osteoporosis at any central site was also -1.7 and for QUS was -2.4. These results are similar to the manufacturer's recommendations. There is no significant difference in performance between the PIXI and QUS.