Screening for women with increased risk of fragility fractures in a general female population using digital X-ray radiogrammetry (DXR).

OBJECTIVE: To evaluate the predictive ability of digital X-ray radiogrammetry (DXR) for fracture in women attending general mammography screening. STUDY DESIGN: In a nested case-control study, women aged between 40 and 75 years, who attended the regional mammography screening program, had their bone mass assessed with DXR and provided information regarding clinical risk factors for osteoporosis. Follow-up was done through cross-referencing with National Patient Registers. Associations between DXR, clinical risk factors and fracture risk were examined. Receiver operating characteristics curves for DXR T-score and different fracture types were plotted, and their respective AUC calculated. MAIN OUTCOME MEASURES: Fractures (hip, major osteoporotic and any clinical facture). Fracture diagnoses were retrieved from National Patient Registers. RESULTS: 14,841 women had their bone mass examined in conjunction with mammography. Of these women, 10,967 returned fully completed questionnaires regarding clinical risk factors. In total 605 fractures (including 355 major osteoporotic fractures and 18 hip fractures) occurred during the follow-up period (median follow-up time was 3.3 years). Women with fractures were older and had lower DXR T-score compared with those without. DXR T-score correlated with fracture risk. HR/SD T-score decrease was 2.15 (CI 1.55-3.00) for hip, 1.47 (CI 1.36-1.59) for major osteoporotic and 1.33 (CI 1.26-1.42) for any clinical fracture. The AUCs for the different fracture types were 0.79 (hip), 0.69 (major osteoporotic) and 0.65 (any clinical). CONCLUSIONS: DXR T-score is negatively correlated with risk of fracture in a general female population. This indicates a potential use of DXR in population-based screening for osteoporosis.

Long-term outcome after spinal fusion for isthmic spondylolisthesis in adults.

BACKGROUND CONTEXT: Data on the long-term outcome after fusion for isthmic spondylolisthesis are scarce. PURPOSE: To study patient-reported outcomes and adjacent segment degeneration (ASD) after fusion for isthmic spondylolisthesis and to compare patient-reported outcomes with a control group. STUDY DESIGN/SETTING: A prospective study including a cross-sectional control group. PATIENT SAMPLE: Patients with isthmic spondylolisthesis underwent posterior lumbar interbody fusion (PLIF) (n=86) or posterolateral fusion (PLF) (n=77). Patient-reported outcome data were available for 73 patients in the PLIF group and 71 in the PLF group at a mean of 11 (range 5-16) years after baseline. Seventy-seven patients in the PLIF group and 54 in the PLF group had radiographs at a mean of 14 (range 9-19) years after baseline. One hundred thirty-six randomly selected persons from the population served as controls for the patient-reported outcomes. OUTCOME MEASURES: Patient-reported outcomes include the following: global outcome, Oswestry Disability Index, Disability Rating Index, and Short Form 36. The ASD was determined from radiographs using the University of California Los Angeles (UCLA) grading scale. METHODS: The chi-square test or analysis of covariance (ANCOVA) was used for group comparisons. The ANCOVA was adjusted for follow-up time, smoking, Meyerding slippage grade, teetotaler (yes/no) and, if available, the baseline level of the dependent variable. RESULTS: There were no significant patient-reported outcome differences between the PLIF group and the PLF group. The prevalence of ASD was 42% (32/77) in the PLIF group and 26% (14/54) in the PLF group (p=.98). The patient-reported outcome data indicated lower physical function and more pain in individuals with surgically treated isthmic spondylolisthesis compared to the controls. CONCLUSIONS: PLIF and PLF groups had similar long-term patient-reported and radiological outcomes. Individuals with isthmic spondylolisthesis have lower physical function and more pain several years after surgery when compared to the general population.

Texture analysis of computed tomography data using morphologic and metabolic delineation of esophageal cancer-relation to tumor type and neoadjuvant therapy response.

The prognostic values of image-based tumor texture analysis based on computed tomography (CT) and of limiting the segmented tumor volume to metabolically active regions using fludeoxyglucose-positron emission tomography (FDG-PET) were studied in 25 patients with esophageal adenocarcinoma and 11 patients with squamous cell carcinoma. The aims of this study are to describe their CT-image-based texture characteristics before and after neoadjuvant therapy and to evaluate whether limiting the examined tumor volume to metabolically active regions detected with FDG-PET image data would further improve their value. Textural parameters (homogeneity, energy, entropy, contrast, and correlation) based on gray-level co-occurrence matrices (GLCM) were calculated for 3D volumes of segmented esophageal tumors before and after neoadjuvant chemotherapy or radiochemotherapy. Histopathological data after surgical resection and textural parameters before and after neoadjuvant treatment were compared using the Mann-Whitney U test. Significant differences in the textural parameters were observed between adenocarcinoma and squamous cell carcinoma for homogeneity, energy, inertia, and correlation. The use of contrast media during scanning resulted in significant differences in homogeneity, energy, entropy, and inertia for adenocarcinoma but not squamous cell carcinoma. There was also a significant difference in all textural parameters between pathological T status for ypT0-ypT2 and ypT3-ypT4 adenocarcinomas, but not in squamous cell carcinoma patients. No additional value was found from using PET image data to aid segmentation of CT images.

Glucocorticoids and Sarcoidosis: A Longitudinal Study on the Effects on Cortical and Trabecular Bone.

BACKGROUND: Glucocorticoid induced osteoporosis is a well-known side effect of glucocorticoid treatment. In sarcoidosis the impact on bone by glucocorticoid treatment is complex due to hormonal disturbances of calcium and vitamin-D, which by itself may cause bone loss. In this study we aimed to investigate the longitudinal impact of glucocorticoids on cortical and trabecular bone in patients with mild, recently diagnosed sarcoidosis. METHODS: Ten patients (8 females; mean age 44 (±13)) were studied during one year of glucocorticoid treatment. The assessment of mainly cortical to purely trabecular bone was made by dual X-ray absorptiometry (DXA) of the spine and hip, quantitative ultrasound of the calcaneus, and magnetic resonance relaxometry of the spine and calcaneus. Bone and hormonal measurements were performed at baseline, after 3, 6, and 12 months, and baseline, 3 weeks and 3 months, respectively. RESULTS: DXA of the spine, decreased from baseline at 6 months (P=0.01). R2' of the calcaneus decreased with time (B: -3.6;P=0.03). In the females (n=8) there was a significant decrease in DXA of the spine when comparing 3 months and 6 months (P=0.03), and 3 months and 12 months (P=0.02) and a decrease in R2'of the calcaneus from baseline to 12 months (P=0.01). There was no change in hormonal levels. CONCLUSION: Treatment of initial mild sarcoidosis with dose tapered glucocorticoid therapy only mildly affects the final trabecular and cortical bone and hormone levels. Dose tapering is an important part in glucocorticoid therapy, likely contributing to the mild effects on bone observed in this study.

Trabecular bone histomorphometric measurements and contrast-to-noise ratio in CBCT.

OBJECTIVES: The aim of this study was to evaluate how imaging parameters at clinical dental CBCT affect the accuracy in quantifying trabecular bone structures, contrast-to-noise ratio (CNR) and radiation dose. METHODS: 15 radius samples were examined using CBCT (Accuitomo FPD; J. Morita Mfg., Kyoto, Japan). Nine imaging protocols were used, differing in current, voltage, rotation degree, voxel size, imaging area and rotation time. Radiation doses were measured using a kerma area product-meter. After segmentation, six bone structure parameters and CNRs were quantified. Micro-CT (µCT) images with an isotropic resolution of 20 µm were used as a gold standard. RESULTS: Structure parameters obtained by CBCT were strongly correlated to those by µCT, with correlation coefficients >0.90 for all studied parameters. Bone volume and trabecular thickness were not affected by changes in imaging parameters. Increased tube current from 5 to 8 mA, decreased isotropic voxel size from 125 to 80 µm and decreased rotation angle from 360° to 180° affected correlations for trabecular termini negatively. Decreasing rotation degree also weakened correlations for trabecular separation and trabecular number at 80 µm voxel size. Changes in the rotation degree and tube current affected CNR significantly. The radiation dose varied between 269 and 1153 mGy cm(2). CONCLUSIONS: Trabecular bone structure can be accurately quantified by clinical dental CBCT in vitro, and the obtained structure parameters are strongly related to those obtained by µCT. A fair CNR and strong correlations can be obtained with a low radiation dose, indicating the possibility for monitoring trabecular bone structure also in vivo.

Digital X-ray radiogrammetry of hand or wrist radiographs can predict hip fracture risk--a study in 5,420 women and 2,837 men.

OBJECTIVES: To assess whether digital X-ray radiogrammetry (DXR) analysis of standard clinical hand or wrist radiographs obtained at emergency hospitals can predict hip fracture risk. METHODS: A total of 45,538 radiographs depicting the left hand were gathered from three emergency hospitals in Stockholm, Sweden. Radiographs with insufficiently included metacarpal bone, fractures in measurement regions, foreign material or unacceptable positioning were manually excluded. A total of 18,824 radiographs from 15,072 patients were analysed with DXR, yielding a calculated BMD equivalent (DXR-BMD). Patients were matched with the national death and inpatient registers. Inclusion criteria were age ≥ 40 years, no prior hip fracture and observation time > 7 days. Hip fractures were identified via ICD-10 codes. Age-adjusted hazard ratio per standard deviation (HR/SD) was calculated using Cox regression. RESULTS: 8,257 patients (65.6 % female, 34.4 % male) met the inclusion criteria. One hundred twenty-two patients suffered a hip fracture after their radiograph. The fracture group had a significantly lower DXR-BMD than the non-fracture group when adjusted for age. The HR/SD for hip fracture was 2.52 and 2.08 in women and men respectively. The area under the curve was 0.89 in women and 0.84 in men. CONCLUSIONS: DXR analysis of wrist and hand radiographs obtained at emergency hospitals predicts hip fracture risk in women and men. KEY POINTS: • Digital X-ray radiogrammetry of emergency hand/wrist radiographs predicts hip fracture risk. • Digital X-ray radiogrammetry (DXR) predicts hip fracture risk in both women and men. • Osteoporosis can potentially be identified in patients with suspected wrist fractures. • DXR can potentially be used for selective osteoporosis screening.

Quantifying differences in hepatic uptake of the liver specific contrast agents Gd-EOB-DTPA and Gd-BOPTA: a pilot study.

OBJECTIVES: To develop and evaluate a procedure for quantifying the hepatocyte-specific uptake of Gd-BOPTA and Gd-EOB-DTPA using dynamic contrast-enhanced (DCE) MRI. METHODS: Ten healthy volunteers were prospectively recruited and 21 patients with suspected hepatobiliary disease were retrospectively evaluated. All subjects were examined with DCE-MRI using 0.025 mmol/kg of Gd-EOB-DTPA. The healthy volunteers underwent an additional examination using 0.05 mmol/kg of Gd-BOPTA. The signal intensities (SI) of liver and spleen parenchyma were obtained from unenhanced and enhanced acquisitions. Using pharmacokinetic models of the liver and spleen, and an SI rescaling procedure, a hepatic uptake rate, K (Hep), estimate was derived. The K (Hep) values for Gd-EOB-DTPA were then studied in relation to those for Gd-BOPTA and to a clinical classification of the patient's hepatobiliary dysfunction. RESULTS: K (Hep) estimated using Gd-EOB-DTPA showed a significant Pearson correlation with K (Hep) estimated using Gd-BOPTA (r = 0.64; P < 0.05) in healthy subjects. Patients with impaired hepatobiliary function had significantly lower K (Hep) than patients with normal hepatobiliary function (K (Hep) = 0.09 ± 0.05 min(-1) versus K (Hep) = 0.24 ± 0.10 min(-1); P < 0.01). CONCLUSIONS: A new procedure for quantifying the hepatocyte-specific uptake of T (1)-enhancing contrast agent was demonstrated and used to show that impaired hepatobiliary function severely influences the hepatic uptake of Gd-EOB-DTPA. KEY POINTS: • The liver uptake of contrast agents may be measured with standard clinical MRI. • Calculation of liver contrast agent uptake is improved by considering splenic uptake. • Liver function affects the uptake of the liver-specific contrast agent Gd-EOB-DTPA. • Hepatic uptake of two contrast agents (Gd-EOB-DTPA, Gd-BOPTA) is correlated in healthy individuals. • This method can be useful for determining liver function, e.g. before hepatic surgery.

Liver vessel enhancement by Gd-BOPTA and Gd-EOB-DTPA: a comparison in healthy volunteers.

BACKGROUND: A thorough understanding of magnetic resonance (MR) contrast media dynamics makes it possible to choose the optimal contrast media for each investigation. Differences in visualizing hepatobiliary function between Gd-BOPTA and Gd-EOB-DTPA have previously been demonstrated, but less has been published regarding differences in liver vessel visualization. PURPOSE: To compare the liver vessel and liver parenchymal enhancement dynamics of Gd-BOPTA (MultiHance) and Gd-EOB-DTPA (Primovist). MATERIAL AND METHODS: The signal intensity of the liver parenchyma, the common hepatic artery, the middle hepatic vein, and a segmental branch of the right portal vein was obtained in 10 healthy volunteers before contrast media administration, during arterial and portal venous phases, and 10, 20, 30, 40, and 130 min after intravenous contrast medium injection, but, due to scanner limitations, not during the hepatic venous phase. The doses of contrast media were 0.1 mmol/kg for Gd-BOPTA and 0.025 mmol/kg for Gd-EOB-DTPA. RESULTS: Maximum enhancement of liver parenchyma was observed from the portal venous phase until 130 min after Gd-BOPTA administration and from 10 min to 40 min after Gd-EOB-DTPA. There was no difference in maximum enhancement of liver parenchyma between the two contrast media. When using Gd-BOPTA, the vascular contrast enhancement was still apparent 40 min after injection, but had vanished 10 min after Gd-EOB-DTPA injection. The maximum difference in signal intensity between the vessels and the liver parenchyma was significantly greater with Gd-BOPTA than with Gd-EOB-DTPA (P<0.0001). CONCLUSION: At the dosage used in this study, Gd-BOPTA yields higher maximum enhancement of the hepatic artery, portal vein, and middle hepatic vein during the arterial and the portal venous phase and during the delayed phases than Gd-EOB-DTPA does, whereas there is no difference in liver parenchymal enhancement between the two contrast agents.

Calcaneus BMD short-term precision in young and elderly subjects using the DXL Calscan.

In this study, the short-term reproducibility and agreement between individual units of dual X-ray and laser (DXL) Calscan (version 2), a new bone densitometry device based on dual X-ray absorptiometry and Laser technique, were evaluated. The variations in bone mineral density (BMD) and T-score between the right and the left foot were also studied retrospectively in 334 individuals. The short-term CV%, based on 19 healthy individuals scanned twice on 4 different units, was 2.1%, and the average CV% per scanner ranged from 1.1% to 1.8%. The short-term CV% in 33 elderly individuals (aged 83+/-6 yr) was 3.9% and in a subgroup with a calcaneal T-score of -2.5 or below (n=16) 5.1%. There was no statistical difference between the average BMD of the right and left foot, and (r2) between the right and left side was 0.84. The observed short- and long-term reproducibilities, as well as the acceptable variation between individual machines, show that this version of Demetech DXL Calscan is suitable for measuring BMD.

Contrast-enhanced magnetic resonance cholangiography with Gd-BOPTA and Gd-EOB-DTPA in healthy subjects.

PURPOSE: To evaluate the biliary enhancement dynamics of the two gadolinium chelates Gd-BOPTA (MultiHance) and Gd-EOB-DTPA (Primovist) in normal healthy subjects. MATERIAL AND METHODS: Ten healthy volunteers were evaluated with both agents by magnetic resonance (MR) imaging at 1.5T using a breath-hold gradient-echo T1-weighted VIBE sequence. The relative signal intensity (SI) differences between the common hepatic duct (CHD) and liver parenchyma were measured before and 10, 20, 30, 40, 130, 240, and 300 min after contrast medium injection. RESULTS: Biliary enhancement was obvious 10 min post-injection for Gd-EOB-DTPA and was noted at 20 min for Gd-BOPTA. At 40 min delay, Gd-BOPTA reached its peak biliary enhancement, but at neither 30 nor 40 min delay was there any significant difference compared with that of Gd-EOB-DTPA. At later delays, the contrast between CHD and liver continued to increase for Gd-EOB-DTPA, whereas it decreased for Gd-BOPTA. CONCLUSION: The earlier onset and longer duration of a high contrast between CHD and liver for Gd-EOB-DTPA facilitates examination of hepatobiliary excretion. Therefore, Gd-EOB-DTPA may provide adequate hepatobiliary imaging within a shorter time span than Gd-BOPTA and facilitate scheduling at the MR unit. Further studies in patients are required to compare the imaging advantages of Gd-EOB-DTPA and Gd-BOPTA in clinical practice.

Standardized volume rendering for magnetic resonance angiography measurements in the abdominal aorta.

PURPOSE: To compare three methods for standardizing volume rendering technique (VRT) protocols by studying aortic diameter measurements in magnetic resonance angiography (MRA) datasets. MATERIAL AND METHODS: Datasets from 20 patients previously examined with gadolinium-enhanced MRA and with digital subtraction angiography (DSA) for abdominal aortic aneurysm were retrospectively evaluated by three independent readers. The MRA datasets were viewed using VRT with three different standardized transfer functions: the percentile method (Pc-VRT), the maximum-likelihood method (ML-VRT), and the partial range histogram method (PRH-VRT). The aortic diameters obtained with these three methods were compared with freely chosen VRT parameters (F-VRT) and with maximum intensity projection (MIP) concerning inter-reader variability and agreement with the reference method DSA. RESULTS: F-VRT parameters and PRH-VRT gave significantly higher diameter values than DSA, whereas Pc-VRT gave significantly lower values than DSA. The highest interobserver variability was found for F-VRT parameters and MIP, and the lowest for Pc-VRT and PRH-VRT. All standardized VRT methods were significantly superior to both MIP and F-VRT in this respect. The agreement with DSA was best for PRH-VRT, which was the only method with a mean error below 1 mm and which also had the narrowest limits of agreement (95% of cases between 2.1 mm below and 3.1 mm above DSA). CONCLUSION: All the standardized VRT methods compare favorably with MIP and VRT with freely selected parameters as regards interobserver variability. The partial range histogram method, although systematically overestimating vessel diameters, gives results closest to those of DSA.

Three-dimensional drip infusion CT cholangiography in patients with suspected obstructive biliary disease: a retrospective analysis of feasibility and adverse reaction to contrast material.

BACKGROUND: Computed Tomography Cholangiography (CTC) is a fast and widely available alternative technique to visualise hepatobiliary disease in patients with an inconclusive ultrasound when MRI cannot be performed. The method has previously been relatively unknown and sparsely used, due to concerns about adverse reactions and about image quality in patients with impaired hepatic function and thus reduced contrast excretion. In this retrospective study, the feasibility and the frequency of adverse reactions of CTC when using a drip infusion scheme based on bilirubin levels were evaluated. METHODS: The medical records of patients who had undergone upper abdominal spiral CT with subsequent three-dimensional rendering of the biliary tract by means of CTC during seven years were retrospectively reviewed regarding serum bilirubin concentration, adverse reaction and presence of visible contrast media in the bile ducts at CT examination. In total, 153 consecutive examinations in 142 patients were reviewed. RESULTS: Contrast media was observed in the bile ducts at 144 examinations. In 110 examinations, the infusion time had been recorded in the medical records. Among these, 42 examinations had an elevated bilirubin value (>19 micromol/L). There were nine patients without contrast excretion; 3 of which had a normal bilirubin value and 6 had an elevated value (25-133 micromol/L). Two of the 153 examinations were inconclusive. One subject (0.7%) experienced a minor adverse reaction - a pricking sensation in the face. No other adverse effects were noted. CONCLUSION: We conclude that drip infusion CTC with an infusion rate of the biliary contrast agent iotroxate governed by the serum bilirubin value is a feasible and safe alternative to MRC in patients with and without impaired biliary excretion. In this retrospective study the feasibility and the frequency of adverse reactions when using a drip infusion scheme based on bilirubin levels has been evaluated.

Volume rendering of three-dimensional drip infusion CT cholangiography in patients with suspected obstructive biliary disease: a retrospective study.

The purpose of this study was to evaluate the diagnostic potential of prolonged drip infusion CT cholangiography (DIC-CT) using meglumine iotroxate (Biliscopin) and 3D volume rendering in patients with suspected obstructive biliary disease. From a material of 142 patients who had undergone a drip infusion CT, all cases with a verified surgical or endoscopic retrograde cholangiography (ERC) diagnosis (n=33) were selected. Age-matched controls were selected from the remaining examinations. Three radiologists reviewed all 66 examinations in retrospect, independently as well as in consensus. The image quality and the estimated diagnostic quality were rated as good or moderate in 91% of the 198 reviews. The consensus sensitivity and specificity for diagnosing biliary stones was 88% and 94%, respectively (with sensitivities ranging from 88% to 94% for individual observers, and specificities from 86% to 96%). Two out of three strictures were observed. No false positive strictures were described. The use of volume rendering technique (VRT) improved diagnostic certainty in 28/198 (14%) of the evaluations. The visualization of ductal stones was improved in 18/48 (38%). No differences in diagnostic quality between single and multislice CT were observed. We conclude that a detailed image of the biliary tree with good sensitivity and specificity can be obtained by means of bilirubin-governed infusion time DIC-CT with volume rendering reconstruction.

Volume rendering compared with maximum intensity projection for magnetic resonance angiography measurements of the abdominal aorta.

PURPOSE: To compare the volume rendering technique (VRT) with maximum intensity projection (MIP) for aortic diameter measurements in MR angiography (MRA) data sets. MATERIAL AND METHODS: Existing contrast-enhanced 3-dimensional MRA and digital subtraction angiography (DSA) data sets from 20 patients were analyzed. In each MRA data set, two aortic diameters were measured using MIP and VRT. Agreement with DSA measurements, dependence on rendering parameters, and interobserver agreement were assessed. RESULTS: Diameters measured on MIP with fixed parameters showed no significant difference compared with DSA and with freely selected parameters a slight overestimation relative to DSA. Diameters measured on VRT were larger than on DSA. For both MIP and VRT, the measurements depended on the chosen parameters. The error relative to DSA was larger for VRT than for MIP with fixed parameters but not with freely chosen parameters. Interobserver agreement did not differ significantly. CONCLUSIONS: VRT is not suitable for diameter measurements of the abdominal aorta with fixed parameter settings but may be useful with user-selected settings.

MR relaxometry of lumbar spine, hip, and calcaneus in healthy premenopausal women: relationship with dual energy X-ray absorptiometry and quantitative ultrasound.

This study evaluates if the reversible transverse relaxation rate (R2') assessed in vivo by MR of lumbar vertebrae, hip, and calcaneus is correlated with dual energy X-ray absorptiometry (DXA) and to quantitative ultrasound (QUS) of the calcaneus. Fifteen healthy premenopausal women aged 23-47 years were studied by DXA, QUS, and MR relaxometry. The GESFIDE sequence was used to separate the FID rate (R2*) into its two components, the non-reversible transverse relaxation rate (R2) and the reversible transverse relaxation rate (R2'). Long-term reproducibility was obtained by repeated measurements of hip and calcaneus in nine individuals after 300+/-89 days. R2' and R2* of the calcaneus had a relationship to broad-band ultrasound attenuation (BUA; r = 0.46, both p<0.05), but not to other US or DXA parameters of the calcaneus. Both R2' and R2* were correlated with bone mineral per area (BMA) of the hip (r>0.73, p<0.001 and r>0.66, p<0.01, respectively). R2 was correlated with BMA(L1-L4) (r = 0.52, p<0.05). R2' and R2* were not correlated with BMA(L1-L4). When the right and left sides were compared in calcaneus and hip the correlation coefficient for R2' and R2* ranged from 0.76 to 0.86 (p<0.001). The long-term reproducibility expressed in coefficient of variation (CV%) was approximately 5 % for R2' and approximately 4% for R2*. Differences in R2 between individuals were not reproducible. The results of this study indicate that R2' and R2* measurements are reproducible and might be of value when evaluating bone quality of the hip and foot.

Orientation of trabecular bone in human vertebrae assessed by MRI.

The aim of the study was to assess the relative number of bone trabeculae in different orientations by using magnetic inhomogeneity measurements by MR imaging. Twelve defatted human vertebrae (L2-L4) were studied by MR imaging and CT. In the MR measurements the reversible transaxial decay rate, R2', was determined using the GESFIDE sequence. The relative contribution to R2' of bone trabeculae oriented along the x (R2'x), y (R2'y) and z (R2'y) axes was assessed, by rotation of the specimen in the magnetic field. The results were validated by CT measurements of trabecular structure at a resolution of 0.2 x 0.2 x 1 mm. using custom-made software. R2' ranged from 4.9 to 32 s-1. After separation, theoretical R2'x ranged from 2.3 to 10.7 s-1, R2'y ranged from 2.6 to 14.0 s-1 and R2'z ranged from 4.7 to 17.9 s-1. The number of bone trabeculae per millimeter identified in axial CT images ranged from 0.15 to 0.38 and from 0.039 to 0.22 per millimeter in sagittal images. The difference between axial and sagittal CT images was statistically significant and due to anisotropic voxels. The correlation between R2' and the number of bone trabeculae per millimeter was statistically significant (r = 0.83, p < 0.001 for x orientation: r = 0.63 for y orientation, and r = 0.59 for z orientation, p < 0.05 for both). The relative amount of bone trabeculae in different orientations can be assessed in vitro using R2' measurements.

The correlation between R2' and bone mineral measurements in human vertebrae: an in vitro study.

The aim of this study was to investigate whether MR imaging of trabecular bone structure using magnetic inhomogeneity measurements is related to the amount of bone mineral in human vertebrae. Weight, bone mineral content (BMCDXA), bone mineral per area (BMADXA) and bone mineral density (BMDCT) were determined in 12 defatted human lumbar vertebrae (L2-L4) by weighing, dual X-ray absorptiometry (DXA) and CT. Inhomogeneity caused by susceptibility differences between trabecular bone and surrounding water was studied with MR imaging at 1.5 T using the GESFIDE sequence. The pulse sequence determines the transverse relaxation rate R2(*) and its two components, the non-reversible transverse relaxation rate (R2) and the reversible transverse relaxation rate (R2'; i. e. relaxation rate due to magnetic susceptibility) in a single scan. Voxel size was 0.9 x 1.9 x 5.0 mm. Positive significant correlations between R2' and weight, BMCDXA, BMADXA and BMDCT were observed (r > 0.61 and p < 0.05 for all). Unexpectedly, R2 was also positively correlated with weight, BMCDXA and BMDCT (r > 0.66 and p < 0.05 for all), but not with BMADXA. Thus, R2' measurements are related to the amount of bone mineral, but they also provide information which is not obtainable from bone mineral measurements.

Total body bone mineral measurements in children with Prader-Willi syndrome: the influence of the skull's bone mineral content per area (BMA) and of height.

Background. The aim of this study was to investigate the influence of body height and growth on total body measurements with dual energy X-ray absorptiometry (DEXA) in children. Material and methods. Seventeen children with Prader-Willi syndrome were studied as part of a clinical investigation of the effect of growth hormone (Genotropin) treatment. Bone mineral areal mass (BMA), in g/cm2, was studied with DEXA at 0, 12, 24 and 30 months after the start of the study. The effect of increased bone volume on BMA was studied by making a rough estimate of bone width, which was correlated with BMA. Results. There was a weak correlation between total body BMA and body height (r = 0.58), which increased after exclusion of the head (r = 0.84). The BMA of the head was more than twice as high as that of the rest of the body. In the shortest children more than 50 % of the total bone mineral was contained in the skull, which decreased with height to below 20 % in the tallest children. The correlation between the so-called bone width and BMA (total body, head excluded) was 0.97. Conclusion. The results indicate that (a) the bone mineral content (BMC) of the head and (b) the bone volume and body height have a major influence on BMA measurements with DEXA in children. A theoretical method for evaluating the relative bone density (g/cm3) has also been described.

Experimental correlation between T2* and ultimate compressive strength in lumbar porcine vertebrae.

RATIONALE AND OBJECTIVES: The authors used magnetic resonance (MR) imaging to investigate the correlation between T2* measurements of trabecular bone and the ultimate compressive strength of lumbar porcine vertebrae. METHODS: Five pigs that weighted 25-32 kg were sacrificed and imaged with a 1.5-T MR system. T2* of the lumbar vertebrae was measured from gradient-echo images. The vertebrae were individually compressed at a fixed speed in the direction of the spine until crushed. The maximum load a vertebra could resist was recorded. RESULTS: T2* ranged from 7.1 to 14.5 msec. T2* determined from 5-mm coronal sections differed from that determined from axial and sagittal sections (P < .05). Between 2.9 and 5.4 kN of force (296-550 kg) was needed to crush a vertebra. A linear correlation between the ultimate compressive strength and T2* of all vertebrae was observed for all imaging planes and section thicknesses (P < .001, except for 10-mm sagittal images, for which P < .002). The T2* determined for the axial plane showed the best correlation with the ultimate compressive strength (r = -0.83). CONCLUSION: The correlation between T2* values and vertebral strength indicates that MR imaging may potentially be used to predict fracture risks in patients.