Single-energy Quantitative Computed Tomography Research Articles

Independent changes in bone mineralized and marrow soft tissues following acute knee injury require dual-energy or high-resolution computed tomography for accurate assessment of bone mineral density and stiffness

Musculoskeletal injuries often induce local accumulation of blood and/or fluid within the bone marrow, which is detected on medical imaging as edema-like marrow signal intensities (EMSI). In addition to its biological effects on post-injury recovery, the displacement of low-attenuating, largely adipocytic marrow by EMSI may introduce errors into quantitative computed tomography (QCT) measurements of bone mineral density (vBMD) and resulting bone stiffness estimates from image-based finite element (FE) analysis. We aimed to investigate the impact of post-injury changes in marrow soft tissue composition on CT-based bone measurements by applying CT imaging at multiple spatial resolutions. To do so, dual energy QCT (DECT) material decomposition was used to detect EMSI in the tibiae of nineteen participants with a recent anterior cruciate ligament tear. We then measured bone density and FE-based apparent modulus within the EMSI region and in a matched volume in the uninjured contralateral knee. Three measurement methods were applied: 1.) standard, QCT density calibration and density-based FEM; 2.) a DECT density calibration that provides density measurements adjusted for marrow soft tissues; and 3.) high-resolution peripheral QCT (HR-pQCT) density and microFE analyses. When measured using standard, single-energy QCT, vBMD and apparent modulus were elevated in the EMSI compared to the contralateral. After adjusting for marrow soft tissue composition using DECT, these measurements were no longer different between the two regions. By allowing for high-resolution, localized density analysis, HR-pQCT indicated that trabecular tissue mineral density was 9 mgHA/cm3 lower, while density of marrow soft tissues was 18 mgHA/cm3 higher, in the EMSI than the contralateral region, suggesting that EMSI have opposite effects on the measured density of trabecular bone and the underlying soft marrow. Thus, after an acute injury, altered composition of marrow soft tissues may artificially inflate overall measurements of bone density and apparent modulus obtained using standard QCT. This can be corrected by accounting for marrow soft tissue attenuation, either by using DECT-based density calibration or HR-pQCT microFE and measurements of local density of trabeculae.

Correction of QCT vBMD using MRI measurements of marrow adipose tissue.

Quantitative computed tomography (QCT) measurements of volumetric bone mineral density (vBMD) are subject to errors due to variations in the amount of bone marrow adipose tissue (BMAT). The purpose of our study was to describe and validate a novel method to correct lumbar spine trabecular vBMD measurements for BMAT using chemical shift-encoded magnetic resonance imaging (CSE-MRI). CSE-MRI measurements of proton density fat fraction (PDFF) were used to correct QCT spine vBMD measurements for BMAT based on the H2O and K2HPO4 basis set equivalent densities of bone, red and yellow bone marrow. BMAT corrected and uncorrected vBMD measurements of the L1 vertebra were compared with dual-energy QCT (DEQCT) measurements in 18 subjects (mean age: 68 y, range 60 to 93 y). A further 400 subjects (mean age: 53 y, range 21 to 82 y) had 120 kVp single-energy QCT and CES-MRI scans of L2-L4 and the data used to simplify the adipose tissue correction by deriving a linear equation between the CSE-MRI vBMD correction and fractional BMAT content. Application of the CSE-MRI derived vBMD correction changed the bias (95% limits of agreement) compared with DEQCT from 26.7 (11.0 to 42.4) mg/cm3 to 2.2 (-9.5 to 13.9) mg/cm3 at 80 kVp, and from 22.4 (3.3 to 41.6) mg/cm3 to 2.9 (-12.6 to 18.4) mg/cm3 at 120 kVp. Data for the 400 subjects gave the following relationship valid at 120 kVp: vBMD correction (mg/cm3) = -12.96 + 75.76 × BMAT. CSE-MRI measurements of PDFF can be used to correct for BMAT content and improve the accuracy of lumbar spine QCT vBMD measurements calibrated using a K2HPO4 phantom.

Evaluation of cross-sectional and longitudinal changes in volumetric bone mineral density in postmenopausal women using single- versus dual-energy quantitative computed tomography.

Central quantitative computed tomography (QCT) is increasingly used in clinical trials and practice to assess bone mass or strength and to evaluate longitudinal changes in response to drug treatment. Current studies utilize single-energy (SE) QCT scans, which may be confounded both by the amount of bone marrow fat at baseline and changes in marrow fat over time. However, the extent to which marrow fat changes either underestimate volumetric BMD (vBMD) measurements at baseline or under-/overestimate longitudinal changes in vivo in humans remains unclear. To address this issue, 197 early postmenopausal women [median age (IQR) 56.7 (54.4-58.7) years] underwent spine and hip QCT scans at baseline and 3 years using a 128-slice dual-source dual-energy (DE) scanner. The scans were analyzed as either SE scans (100 kVp) or DE scans (100 kVp and 140 kVp), with the latter accounting for bone marrow fat. At baseline, vertebral trabecular vBMD was (median) 17.6% lower (P < 0.001) while femur neck (FN) cortical vBMD was only 3.2% lower (P < 0.001) when assessed by SE vs DE scanning. SE scanning overestimated the 3 year rate of bone loss for trabecular bone at the spine by 24.2% (P < 0.001 vs DE rates of loss) but only by 8.8% for changes in FN cortical vBMD (P < 0.001 vs DE rates of loss). The deviation between SE and DE rates of bone loss in trabecular vBMD became progressively greater as the rate of bone loss increased. These findings demonstrate that SE QCT scans underestimate trabecular vBMD and substantially overestimate rates of age-related bone loss due to ongoing conversion of red to yellow marrow. Further, the greater the rate of bone loss, the greater the overestimation of bone loss by SE scans. Although our findings are based on normal aging, recent evidence from animal studies demonstrates that the skeletal anabolic drugs teriparatide and romosozumab may markedly reduce marrow fat, perhaps accounting for the disproportionate increases in trabecular vBMD by SE QCT as compared to dual-energy X-ray absorptiometry with these agents. As such, future studies using recently available DE scanning technology that has satisfactory precision and radiation exposure are needed to evaluate changes in trabecular vBMD independent of changes in marrow fat with aging and drugs that may alter marrow fat composition.

A novel dual energy method for enhanced quantitative computed tomography

Accurate assessment of bone mineral density (BMD) is critically important in clinical practice, and conveniently enabled via quantitative computed tomography (QCT). Meanwhile, dual-energy QCT (DEQCT) enables enhanced detection of small changes in BMD relative to single-energy QCT (SEQCT). In the present study, we aimed to investigate the accuracy of QCT methods, with particular emphasis on a new dual-energy approach, in comparison to single-energy and conventional dual-energy techniques. We used a sinogram-based analytical CT simulator to model the complete chain of CT data acquisitions, and assessed performance of SEQCT and different DEQCT techniques in quantification of BMD. We demonstrate a 120% reduction in error when using a proposed dual-energy Simultaneous Equation by Constrained Least-squares method, enabling more accurate bone mineral measurements.

The measurement of liver fat from single-energy quantitative computed tomography scans.

Studies of soft tissue composition using computed tomography (CT) scans are often semi-quantitative and based on Hounsfield units (HU) measurements that have not been calibrated with a quantitative CT (QCT) phantom. We describe a study to establish the water (H2O) and dipotassium hydrogen phosphate (K2HPO4) basis set equivalent densities of fat and fat-free liver tissue. With this information liver fat can be accurately measured from any abdominal CT scan calibrated with a suitable phantom. Liver fat content was measured by comparing single-energy QCT (SEQCT) HU measurements of the liver with predicted HU values for fat and fat-free liver tissue calculated from their H2O and K2HPO4 equivalent densities and calibration data from a QCT phantom. The equivalent densities of fat were derived from a listing of its constituent fatty acids, and those of fat-free liver tissue from a dual-energy QCT (DEQCT) study performed in 14 healthy Chinese subjects. This information was used to calculate liver fat from abdominal SEQCT scans performed in a further 541 healthy Chinese subjects (mean age 62 years; range, 31-95 years) enrolled in the Prospective Urban Rural Epidemiology (PURE) Study. The equivalent densities of fat were 941.75 mg/cm3 H2O and -43.72 mg/cm3 K2HPO4, and for fat-free liver tissue 1,040.13 mg/cm3 H2O and 21.34 mg/cm3 K2HPO4. Liver fat in the 14 subjects in the DEQCT study varied from 0-17.9% [median: 4.5%; interquartile range (IQR): 3.0-7.9%]. Liver fat in the 541 PURE study subjects varied from -0.3-29.9% (median: 4.9%; IQR: 3.4-6.9%). We have established H2O and K2HPO4 equivalent densities for fat and fat-free liver tissue that allow a measurement of liver fat to be obtained from any abdominal CT scan acquired with a QCT phantom. Although radiation dose considerations preclude the routine use of QCT to measure liver fat, the method described here facilitates its measurement in patients having CT scans performed for other purposes. Further studies comparing the results with magnetic resonance (MR) measurements of liver fat are required to validate the method as a useful clinical tool.

OP0233 QCT indicates locally increased bone mineral density (BMD) in regions of bone marrow lesions (BML) segmented on MR images

BackgroundWhile the association of BMLs with joint space narrowing and pain in knee OA is verified, the correlation between BMLs and local BMD is a topic of major interest with...

Bone marrow lesions identified by MRI in knee osteoarthritis are associated with locally increased bone mineral density measured by QCT

Bone marrow lesions (BMLs) in the knee are associated with pain and compartment-specific joint space narrowing. However, the correlation of BMLs with bone mineral density (BMD) has rarely been investigated. The aim of the present study was to examine whether BMD in BMLs is altered compared to the surrounding bone. Thirty-four BMLs detected in osteoarthritis (OA) knees (KL grade 2 and 3) of 26 patients were investigated. A 3D-segmentation was used to determine BML volumes of interest (VOI) and their surrounding bone in MR images. These VOIs were registered to corresponding single-energy QCT images and a BMD analysis was performed. The same VOIs were transferred to control datasets (19 OA patients without BMLs) by an elastic registration, where the BMD analysis was repeated. To account for the dependence of bone marrow composition on BMD measures derived using single-energy QCT, simulations were performed to evaluate how changing fat-water compositions likely occurring with BML development may influence BMD measures and observed BMD differences between patients with and without BMLs. The association between loading in the knee and the occurrence of BMLs was investigated by medial to lateral (M:L) BMD ratios. BMD was significantly increased at BML locations, even with a fat-to-water conversion rate of 39%. The M:L BMD ratio was significantly increased in bones with medial BMLs. BMD was examined exactly at BML locations and surrounding bone using highly accurate segmentation and registration methods. BMD was significantly increased at BML locations (P<0.05).

Quantitative computed tomography is unreliable for measurement of bone mineral density in inadequately chelated adolescent patients with β-thalassemia major: A case-control study

Utility of quantitative computed tomography (QCT) for assessment of bone mineral density (BMD) in patients with thalassemia is not fully established. Majority of patients with thalassemia in India receive suboptimal iron chelation. There is paucity of data on BMD in this population. Aim was to assess BMD by lumbar QCT in adolescent patients with transfusion dependent β-thalassemia major and compare with controls. Study was conducted prospectively, over 15 months. Single energy QCT was performed through first three lumbar vertebrae. Forty-five patients were enrolled (age: 10-19 years). Thirty-eight normal siblings of patients with thalassemia patients served as controls. Forty percent patients weighed <3rd percentile, 64% were stunted, and 40% had suboptimal sexual maturity scores. Eighteen (40%) patients were on iron chelation with deferiprone. Mean serum ferritin was 2,800 ± 1,473 ng/ml. Mean BMD (mg/cu mm) of cases and controls was 194.5 ± 27.1 and 170.4 ± 28.84, respectively (P = 0.0002). The mean BMD of patients with ferritin <2,000 ng/ml and those with a higher ferritin was 181.2 ± 14.9 and 196.7 ± 25, respectively (P = 0.07). The finding of increased BMD in patients with thalassemia is in stark contrast to published reports. Patients had several risk factors for low BMD, including growth retardation, delayed puberty, and iron overload. Single energy QCT of lumbar vertebrae is not reliable for measurement of BMD in inadequately chelated patients with β-thalassemia major. The deposition of iron in bone tissue may result in increased X-ray attenuation values of trabecular bone.

Effect of Bone Strontium on BMD Measurements

Strontium ranelate is a new treatment for osteoporosis that is of interest for, among other reasons, its unusual effect on measurements of bone mineral density (BMD). When some of the calcium in bone is replaced by strontium, X-ray absorptiometry measurements of BMD are overestimated because strontium attenuates X-rays more strongly than calcium. In this study, we report the first theoretical estimation of this effect for measurements made using axial (spine and hip) dual-energy X-ray absorptiometry (DXA), peripheral DXA (pDXA), and single-energy quantitative computed tomography (SEQCT). Tables of X-ray attenuation coefficients were used to calculate values of the strontium ratio defined as the ratio of the percentage overestimation of BMD to the molar percentage of strontium (%Sr/[Ca + Sr]) in bone. For DXA measurements, the theoretical value of the strontium ratio increased slightly with increasing effective photon energy of the X-ray beam with figures of 9.0 for Osteometer DTX200 and G4 pDXA devices (Osteometer Meditech Inc., Hawthorne, CA), 10.0 for GE-Lunar DPX and Prodigy DXA systems (GE-Lunar, Madison, WI), 10.4 for Hologic QDR1000 and QDR2000, and 10.8 for Hologic QDR4500 and Discovery (Hologic Inc., Bedford, MA). Results for SEQCT also varied with the effective photon energy with strontium ratios of 6.2 at 60 keV and 4.4 at 80 keV. The results of the theoretical study are in good agreement with the experimental value of 10 reported by Pors Nielsen and colleagues for a variety of different axial DXA systems. A reliable figure for the strontium ratio is important for adjusting BMD measurements in strontium ranelate treated patients for the effect of bone strontium content. This latter correction will be required for the interpretation of future DXA scans in patients who have discontinued strontium ranelate treatment.

Ankylosing spondylitis and bone mineral density—what is the ideal tool for measurement?

Ankylosing spondylitis (AS) is characterised by chronic inflammation and partial ossification, yet vertebral fractures due to osteoporosis, although common, are frequently unrecognised. The aim of this study was to (1) show the frequency of changes in the progress of osteopenia/osteoporosis in AS depending on duration and stage of the disease and (2) assess the ranking of two different methods of bone density measurement in this clinical pattern. We measured bone density in 84 male and female patients with both dual X-ray absorptiometry (DXA) and single energy quantitative computed tomography (SE-QCT). In the initial and advanced stages of the disease, a high decrease in axial bone density could be verified (DXA: osteopenia in 5% and osteoporosis in 9.2%; SE-QCT: osteopenia in 11.8% and osteoporosis in 30.3%). Peripheral bone density decrease as in osteopenia could be proven in 17.6% by DXA measurement. With SE-QCT, a decrease in vertebral trabecular bone density could already be observed in the initial stage and continued steadily during the course of the disease; cortical bone displayed the same trend up to stages of ankylosis. With DXA, valid conclusions are more likely to be expected in less marked ankylosing stages of AS. In stages of advanced ankyloses in the vertebral region (substantial syndesmophytes), priority should be given to SE-QCT, due to the selective measurement of trabecular and cortical bone. The DXA method often yields values that are too high, and the replacement of vertebral trabecular bone by fatty bone marrow is not usually recorded as standard. There may already be an increased risk of bone fracture in AS in osteopenia on DXA along with an osteoporosis already established on SE-QCT.

Correlation of bone density and geometric parameters to the mechanical strength of the femoral neck

Bone density in six different regions along the axis of the femoral neck was studied by single energy-quantitative CT (SE-QCT) and simple geometric parameters were measured in 42 proximal cadaveric femora. Mechanical testing of the proximal femur was performed simulating the peak load direction during the double support phase of gait. This load direction was maintained until femoral neck fracture occurred. The structural stiffness of the proximal femur was approximated by dividing the peak load by the deflection of the setup at peak load. Bone mineral density determined in the femoral head (r=0.74, p< 0.01), the femoral neck (r=0.51, p< 0.01) and the centre of the trochanteric area (r=0.30, p<0.05) significantly correlated with the mechanical strength of the femoral neck as found by statistical analysis (Pearson test). Considering geometric data, the best result was yielded by correlation of fracture load to the diameter of the femoral neck (r=0.53, p<0.01) and the collodiaphysis angle (CDA) (r=0.37, p<0.05). Bone stiffness was defined as the ratio of fracture load and amount of deformation of the proximal femur. The best correlation of density and stiffness were found in the femoral head (r=0.48, p<0.01) and the femoral neck (r=0.27, p<0.05). Statistical correlation could be improved by combining geometric parameters as lever arm (r=0.7714, p<0.01) and diameter of femoral neck (r=0.7557, p<0.01) with fracture pressure. In conclusion, the findings of this study contribute to the establishment of clinical guidelines for the identification and treatment of patients at high risk of a proximal femoral fracture.

Decreased Bone Density in Splenectomized Gaucher Patients Receiving Enzyme Replacement Therapy

ABSTRACTLittle is known about the effect of enzyme replacement therapy (ERT) on the bone abnormalities in Gaucher disease. Splenectomized Gaucher patients tend to suffer the most severe skeletal complications. We hypothesized that vitamin D supplementation would act synergistically with glucocerebrosidase infusions to increase bone density in splenectomized Gaucher patients. In a 24-month study, 29 splenectomized Gaucher patients were randomized to three groups: Group 1, calcitriol (1,25-dihydroxyvitamin D3; 0.25–3.0 μg/day) alone for the first 6 months with the addition of ceredase/cerezyme at 60 IU/kg every 2 weeks during months 7–12; Group 2, calcitriol together with ceredase/cerezyme at 60 IU/kg every 2 weeks during months 1–6; and Group 3, enzyme only at 60 IU/kg body wt every 2 weeks. In all three groups, enzyme dose was halved after the first 6 months of therapy. The primary outcome measure was bone mineral density of the lumbar spine measured by single-energy quantitative CT. Bone density by single-energy CT (P = 0.001) and by dual-energy CT (P = 0.06) declined overall, but there was no significant difference between the groups. Calcitriol had no significant effect on bone density. Fat fraction in lumbar spine increased (P = 0.000) and skeletal MRI scores improved. Bone-specific alkaline phosphatase (P = 0.002) and serum osteocalcin increased (P = 0.008), while blood cyclic AMP and urinary deoxypyridinoline did not change appreciably. Hemoglobin, platelet counts, and liver volume significantly improved. We conclude that ERT alone, or in combination with calcitriol, cannot repair the bone composition in splenectomized adult Gaucher patients. Alternatively, measuring trabecular bone density may be an inadequate marker of clinical efficacy for treating skeletal involvement in Gaucher disease.

The X-ray attenuation characteristics and density of human calcaneal marrow do not change significantly during adulthood

Changes in the material characteristics of bone marrow with aging can be a significant source of error in measurements of bone density when using X-ray and ultrasound imaging modalities. In the context of computed tomography, dual-energy computed techniques have been used to correct for changes in marrow composition. However, dual-energy quantitative computed tomography (DE-QCT) protocols, while increasing the accuracy of the measurement, reduce the precision and increase the radiation dose to the patient in comparison to single-energy quantitative computed tomography (SE-QCT) protocols. If the attenuation properties of the marrow for a particular bone can be shown to be relatively constant with age, it should be possible to use single-energy techniques without experiencing errors caused by unknown marrow composition. Marrow was extracted by centrifugation from 10 mm thick frontal sections of 34 adult cadaver calcanei (28 males, 6 females, ages 17–65 years). The density and energy-dependent linear X-ray attenuation coefficient of each marrow sample were determined. For purposes of comparing our results, we then computed an effective CT number at two GE CT/i scan voltages (80 and 120 kVp) for each specimen. The coefficients of variation for the density, CT number at 80 kVp and CT number at 120 kVp were each less than 1%, and the parameters did not change significantly with age ( p>0.2, r 2<0.02, power>0.8 where the minimum acceptable r 2=0.216). We could demonstrate no significant gender-associated differences in these relationships. These data suggest that calcaneal bone marrow X-ray attenuation properties and marrow density are essentially constant from the third through sixth decades of life.

EVALUATION OF OSTEOPOROSIS IN THALASSEMIA BY QUANTITATIVE COMPUTED TOMOGRAPHY: Is It Reliable?

This study was conducted to quantify the degree of osteoporosis in thalassemic patients by single energy quantitative computed tomography (SEQCT) and to test the reliability of this method. On 38 thalassemic patients with osteoporosis and 38 normal control subjects, bone mineral density (BMD) measurements were done by SEQCT. BMD and standard deviation (SD) of the x-ray attenuation numbers of pixels within region of interest (ROI) of the measurement areas were compared between two groups. Mean BMD values for thalassemic patients and control group were 173.4 and 158.2 mg/cm3, respectively. Mean BMD value for thalassemic patient group was significantly higher. Mean SD values of ROI for control group and thalassemic patients were 41.4 and 71.1, respectively. The difference between the SD values was also statistically significant. Positive correlation was noted between SD values and patients' ages in the thalassemic group. Results of SEQCT method may not reflect the clinical and conventional radiographic findings of osteoporosis seen in thalassemic patient group and should be used cautiously. Other methods of BMD measurement, such as photon absorbsiometry and x-ray absorbsiometry, should also be investigated for their accuracy in this patient group.

An anthropomorphic phantom study on the effect of midvertebral slice placement and region-of-interest positioning on the reproducibility of single-energy quantitative CT (QCT) of the spine.

The purpose of our study was to develop an anthropomorphic phantom with a 3D external reference system capable of geometrically describing the region of interest (ROI) of single-energy quantitative CT (QCT) scans and to study the reproducibility of ROI placement (volume) and bone mineral density (BMD) after operator-defined and algorithm-supported midvertebral slice (MVS) placement. In three vertebrae (L1-3) of 10 human cadaveric spines placed in a water phantom, MVSs were defined by an operator and an algorithm-supported technique on lateral digital CT radiographs, and QCT scans were performed accordingly. The measurements were repeated once after repositioning the phantom on the CT table. ROIs of the trabecular bone were determined with a standard technique. The percentage of bone volume was calculated for one ROI not covered by the repetition (volume mismatch percent). Reproducibility with algorithm-supported MVS placement was superior to that of operator-defined positioning with regard to volume mismatch (mean +/- SD): 10.6+/-8.4 vs. 7.9+/-5.3%; and mean of paired BMDs (mean of three vertebral bodies): 2.7 vs. 1.5% (p < 0.05). The ROI volume mismatch of repeated QCT scans, which is approximately 10% of ROI volume, can be quantified with an external reference system. Automated placement is superior to the manual technique and should be used in clinical practice.

Contribution of the cortical shell of vertebrae to mechanical behaviour of the lumbar vertebrae with implications for predicting fracture risk.

In the diagnosis of osteoporosis using single energy quantitative CT (SE-QCT) on the axial skeleton, only spongy bone mineral density (BMD) is used at present. Although the density of cortical bone is also determined by most QCT methods, it is not used for evaluation. The objective of this study was to determine the extent to which the cortical bone of the lumbar vertebral bodies accounts for their load-bearing capacity and failure behaviour, and to use this information to suggest improvements in the differential diagnosis of osteoporosis. Investigations were conducted in a clinical, theoretical-numerical and biomechanical-experimental context. Cortical (BMDC) and spongy (BMDS) bone mineral density was measured by SE-QCT/85 kV on 179 patients (68 males, 111 females). These bone densities were matched with the vertebral body fractures previously determined from conventional X-rays. A finite element model was used to study the variation in structural and material parameters of the vertebral body. 19 vertebral bodies that had been removed post-mortem were available for the biomechanical-experimental investigations. Spongy and cortical bone densities were also determined by SE-QCT on these vertebral bodies. Their failure load was then measured in the axial compression test. These investigations show that, in addition to the spongiosa, the cortical shell plays an important role in the load-bearing capacity of the vertebral body. If the spongiosa is weakened due to a loss of BMD, the residual load-bearing capacity of the vertebral bodies is increasingly shouldered by the cortical bone. The lower susceptibility to fracture in men compared with women when spongy bone mineral density is reduced can thus be attributed to the lack of a reduction in cortical bone mineral density. It is recommended that the BMDC also be evaluated in future, especially in the diagnosis of bone mass losses in women, to improve the estimation of the individual fracture risk.

Accuracy of single-energy quantitative computed tomography in the assessment of bone mineral density of cervical vertebrae.

Earlier studies have shown that single-energy quantitative computed tomography (SEQCT) is a reliable method for bone mineral density (BMD) measurements in thoracic and lumbar vertebrae. Moreover, SEQCT has proved to be a useful parameter in the selection of appropriate implants in cervical spondylodesis. The aim of this study was to determine the accuracy of SEQCT in cervical vertebrae BMD measurement. BMD with reference to calcium hydroxyapatite (Ca10[PO4]6[OH]2) was assessed by SEQCT in 100 human vertebral bodies of the cervical spine. Bone cylinders were then cut from the appropriate region of interest. The cylinder volume was determined by the liquid displacement technique. The density of the mineral component was measured following incineration at 1100 degrees C for 24 h. The calculated BMD was correlated with the SEQCT values, resulting in a coefficient of r = 0.79 (P < 0.01). Mean SEQCT values were significantly lower than those determined by direct density assessment (t-test for coupled sampling, P < 0.02). This result was in agreement with studies on thoracic and lumbar vertebrae. These data suggest that SEQCT can reliably measure BMD in the cervical spine.

3 How can we measure bone quality?

Osteoporosis is a systematic skeletal disease characterized by low bone mass and microarchitectural deterioration of bone tissue. This leads to diminished biomechanical competence of the skeleton and is associated with low-trauma or atraumatic fractures. In the past decade, considerable progress has been made in the development of methods for assessing the skeleton non-invasively, so that osteoporosis can be better managed. While dual X-ray absorptiometry (DXA) is still the preferred methodology, several limitations will be addressed. Another densitometric technique which is widely accepted for diagnosis of spinal osteoporosis is single energy QCT. Measurements of vertebral trabecular bone mineral density (BMD) demonstrate larger percentage decrements between vertebrally-fractured subjects and normal controls, and confer higher relative risks for vertebral fracture than either anteroposterior or lateral DXA measurements. As an emerging alternative to photon absorptiometry techniques, there is a growing interest in the use of quantitative ultrasound (QUS) measurements for the non-invasive assessment of osteoporotic fracture risk in the management of osteoporosis. The attractiveness of QUS lies in the fact that indirect and in vitro experience has suggested that ultrasound may give information not only about BMD but also about architecture and elasticity. Whether or not combining QUS and DXA improve fracture prediction is still unclear and needs further analysis. Due to the growing evidence supporting the use of QUS in osteoporosis and the large number of QUS devices already on the market, a general clinical consensus on the application of QUS is urgently needed. Other techniques that are less widely used for the management of osteoporosis. For example, peripheral quantitative computed tomography, quantitative magnetic resonance (QMR) and magnetic resonance microscopy are promising tools for the evaluation of the skeleton. For example, the ability of QMR and high resolution magnetic resonance imaging has been explored and shows promise as a technique for assessing trabecular bone structure in osteoporosis.

The Relationship Between Developmental Lumbar Spinal Stenosis and its BMD Value: Comparison by Single Energy Quantitative CT

The Relationship Between Developmental Lumbar Spinal Stenosis and its BMD Value: Comparison by Single Energy Quantitative CT

Mineral content of vertebral trabecular bone: Accuracy of dual energy quantitative computed tomography evaluated against neutron activation analysis and flame atomic absorption spectrometry

The goal of this study was to evaluate the accuracy of preprocessing dual energy quantitative computed tomography (QCT) for assessment of trabecular bone mineral content (BMC) in lumbar vertebrae. The BMC of 49 lumbar vertebrae taken from 16 cadavers was measured using dual energy QCT with advanced software and hardware capabilities, including an automated definition of the trabecular region of interest (ROI). The midvertebral part of each vertebral body was embedded in a polyester resin and, subsequently, an experimental ROI was cut out using a Scanjet image transmission procedure and a computer-assisted milling machine in order to mimic the ROI defined on QCT. After low temperature ashing, the experimental ROIs reduced to a bone powder were submitted to either nondestructive neutron activation analysis ( n = 49) or to flame atomic absorption spectrometry ( n = 45). BMC obtained with neutron activation analysis was closely related ( r = 0.896) to that derived from atomic absorption spectrometry, taken as the gold standard, with, however, a slight overestimation. BMC values measured by QCT were highly correlated with those assessed using the two reference methods, all correlation coefficients being > 0.841. The standard errors of the estimate ranged 47.4–58.9 mg calcium hydroxyapatite in the regressions of BMC obtained with reference methods against BMC assessed by single energy QCT, 47.1–51.9 in the regressions involving dual energy QCT. We conclude that the trabecular BMC of lumbar vertebrae can be accurately measured by QCT and that the superiority in accuracy of dual energy is moderate, which is possibly a characteristic of the preprocessing method.