应用定量CT测定胸椎骨矿密度

目的对行心脏CT检查的病人应用定量CT进行胸椎骨矿密度(BMD)测定,获得标准值,并将该值(来自各亚组)与行腰椎定量CT检查所获得的骨矿密度值进行比较。材     

Fractional quantitative computed tomography for bone mineral density evaluation: accuracy, precision, and comparison to quantitative computed tomography

OBJECTIVE: To evaluate bone mineral density considering its distribution, fractional quantitative computed tomography (fQCT) was designed and verified. METHODS: Quantitative computed tomography (QCT) was performed at 64 areas in 10 swine long bones. Fractional quantitative computed tomography was measured at the identical areas as the proportion of pixels showing a bone density higher than 130 mg/mL equivalent. All target areas were extracted and incinerated to measure apparent ash bone density. Based on standard references, the accuracy and precision of fQCT were evaluated and the results were compared with conventional QCT results. RESULTS: The correlation coefficient between fQCT and apparent ash bone density was 0.843 (P < 0.0001). The fQCT showed good correlation with volume fraction (r = 0.88, P < 0.0001). The coefficient of variation of fQCT was 0.42%. The fQCT revealed higher accuracy and precision than the results of QCT. CONCLUSION: Fractional quantitative computed tomography was designed and verified as a reliable method to measure bone mineral density.     

Assessment of the bone mineral density in the lumbar vertebrae of newborns by quantitative computed tomography

 Objective. To assess the true mineral density (BMD, in g/cm³) of the lumbar spine in newborns. Design and patients. A post-mortem analysis of five infants with gestational ages ranging from 35 to 40 weeks, and birth weights from 2765 to 3200 g, was conducted using dual-energy quantitative computed tomography (QCT; Siemens Somatom DR). A 2 or 4 mm thick slice was obtained for each lumbar vertebra from L1 to L4. The density measured in these vertebrae was corrected by reference to a solid phantom (Osteo-CT) measured simultaneously. A three-dimensional image of the spine (Elscint CT Twin), as well as a photomicrograph of histological preparation from L2 vertebra, were also obtained in another term baby for comparison with the CT results. Results and conclusions. In the range of values studied, the vertebral densities were not dependent on birth weight. BMD values measured in L2, L3 and L4 were not significantly different, but were 10% lower than in L1 in four of five infants. The spatial resolution of the QCT protocol used (0.4 mm) did not permit the differentiation of trabecular and cortical bone, and the vertebral bodies appeared very homogeneous and dense, with a mean density value of 210±30 mg Ca/cm³, which is 2.5 times higher than the mean maximum value found in young normal adults. These preliminary results highlight the potential of QCT in neonatology. Special protocols will, however, need to be developed for in vivo measurements in this particular paediatric field.     

Reference values for trabecular and cortical vertebral bone density in single and dual-energy quantitative computed tomography

The validity of reference values for vertebral bone mineral density (BMD) reported in the literature has frequently been questioned. The introduction of dual-energy methods, new calibration systems, and automated image evaluation algorithms, has also made it necessary for us to re-evaluate BMD values in a normal population. We present patient selection criteria, CT measurement and evaluation protocols and results of single energy (SEQCT) and dual energy quantitative CT (DEQCT) for trabecular (tBMD) and cortical (cBMD) bone density in 135 males and 139 females. For SEQCT, tBMD loss rates of 1.7 and 1.8 mg/ml per year for males and females, respectively, were determined by linear regression. The respective DEQCT data show smaller decrements with age. Different statistical models for tBMD in females were tested; models based on a multiphase variation of tBMD yielded an improvement of the fit. For cBMD the percent rate of loss with age is much smaller than for tBMD; females showed a significantly higher loss rate than males, however. A comparison of our results with published data is included.     

Modified method of spinal computed tomography for trabecular bone mineral measurements

Quantitative CT of vertebral trabecular bone is established as a sensitive technique for assessing bone mineral mass in the axial skeleton. We have adapted this technique for use in a standard third generation whole body CT scanner without requiring any extra equipment or software. By utilizing a maximum area of interest in the vertebral trabecular bone, we have developed a method of bone mineral content estimation that is precise, accurate, and a more representative measurement of the vertebral trabecular bone. Measurements in 70 healthy postmenopausal women have shown that our results compare favourably with those from other centres. Our findings demonstrate that the technique of quantitative CT of bone can be adapted for advanced CT scanners without any modifications being required. This should lead to an increase in availability of such measurements, resulting in improvements both in the diagnosis of metabolic bone diseases and in the efficacy of treatment.     

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 °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. Received 12 July 1996; Revision received 17 January 1997; Accepted 10 March 1997     

Evaluation of bone mineral density with dual energy quantitative computed tomography (DEQCT)

Quantitative computed tomography (QCT) has been found useful in the evaluation of vertebral bone mineral density (BMD). It separates cortical from trabecular bone in the vertebral bodies. The accuracy of QCT, however, is limited because of the existence of unknown amounts of marrow fat in the trabecular bone. The purpose of this study is to investigate the precision and accuracy of QCT, with a particular emphasis on the advantage of dual energy technique over single energy technique, as well as to investigate age-related change of BMD in patients with no metabolic disorders. For evaluation of BMD, SOMATOM DR-H CT scanner was used, which provided dual energy scan with rapid kilovolt peak switching system. The lumbar vertebrae (L1-L3) were exposed at the middle portion together with the calibration phantom (Ca10(PO4)6(OH)2 200 mg/ml, 0 mg/ml). KV-separated images (KV-HI, KV-LO) and material-separated images (MAT-HI, MAT-LO) were calculated from dual-energy scan data. KV-separated data were considered as SEQCT data. In experiment, dipotassium hydrogen phosphate (K2HPO4) solution was used to simulate bone mineral, water to simulate lean soft tissue and ethanol (C2H5OH) to simulate fat. To investigate the variations originating from marrow fat, a series of phantoms (K2HPO4-C2H5OH-H2O mixtures) with a constant 10 gm% K2HPO4 concentration but with the various mixtures of C2H5OH ranging from 0-40% by volume was scanned with dual energy technique. The value of BMD obtained from KV-separated data was reduced about 12% per 10% fat by volume increase, while the value obtained by DEQCT technique was reduced 5.5% per 10% fat by volume increase. With the dual energy technique the error was greatly reduced. On the other hand, the higher precision of KV-separated images compared to MAT-HI images was obtained, as well as the relatively higher precision for determining high rather than low fraction of mineral. In conclusion, with the single energy technique, precision is high, and with the dual energy technique, accuracy is high. It was also noted that selection of the CT section was the most critical factor in clinical BMD analysis. Age-related change of BMD in vertebral trabecular and cortical bone was studied in 161 patients without bone metabolic disorders. There were two peaks of BMD in females in their 20s and 30s, and a single peak in males in their 20s.(ABSTRACT TRUNCATED AT 400 WORDS)     

Vertebral body trabecular density at the thoracolumbar junction using quantitative computed tomography. A post-mortem study

Quantitative computed tomography was used to assess vertebral trabecular density in 26 post-mortem spines from individuals aged between 14 and 80 years. All vertebrae from T10 to L1 were scanned transversely near the mid-vertebral level with calculations of trabecular density in HUs averaged and referenced to a mineral equivalent phantom. An age-related decline in trabecular density was recorded (r = 0.55, p less than 0.0001). Density measures from the anterior aspect of the vertebral body were significantly greater than from postero-lateral regions. From T10 to L1, there was a significant decrease in trabecular density, whereas density measures multiplied by vertebral body cross-sectional area were constant. Predictions of vertebral compressive strength using quantitative computed tomography may become more accurate by increasing the sampling area per scan and including vertebral body cross-sectional area as part of the radiologic assessment.     

Measurement of lumbar spine bone mineral: a comparison of dual photon absorptiometry and computed tomography

A comparison of computed tomography (CT) and dual photon absorptiometry (DPA) in the measurement of spinal bone mineral was made in 44 subjects of whom 26 had vertebral crush fractures. Although CT measures only trabecular bone within the vertebral body whilst DPA measures the whole vertebral segment, a good correlation was observed (r = 0.80) when these quantities were expressed in dimensionally similar units. Trabecular bone in the distal radius measured by CT correlated less well with vertebral CT (r = 0.65). Cortical bone in the radius correlated poorly with the spinal DPA measurement (r = 0.38).     

Influence of anthropometric parameters and bone size on bone mineral density using volumetric quantitative computed tomography and dual X-ray absorptiometry at the hip

PURPOSE: To evaluate the influence of anthropometric parameters (age, height, and weight) and bone size on bone mineral density (BMD) using volumetric quantitative computed tomography (QCT) and dual X-ray absorptiometry (DXA) in a group of elderly women. MATERIAL AND METHODS: BMD values were obtained with DXA and QCT at the spine and hip in a cohort of 84 elderly women (mean age 73 +/- 6 years). QCT measures included trabecular, integral, and cortical BMD assessed at the hip and spine as well as cross-sectional areas of the mid-vertebrae and proximal femora. Spinal integral and femoral neck BMD measures were well matched to the regions of bone quantified on anteroposterior (AP) spine DXA and the femoral neck region of hip DXA. RESULTS: When QCT parameters were linearly regressed against body height and weight, only the relationships with weight were found to be statistically significant. Except for cortical BMD at the femoral neck, all BMD and geometric parameters measured from both DXA and QCT showed statistically significant associations with body weight (r2 = 0.4, 0.0001 < P < 0.02). The strongest associations with weight were found for DXA Neck (DXA_NECK) and DXA lumbar spine (DXA_LSP) (r2 = 0.4, P < 0.0001). CONCLUSION: The relationship of DXA BMD is stronger than QCT BMD with body weight and it encompasses the response of both bone size and density to increasing body mass.     

Local differences in mineral content in vertebral trabecular bone measured by dual-energy computed tomography

Twelve lumbar vertebral bodies from cadavers were examined with dual-energy CT, to measure the calcium content in a big central region of interest (ROI). In each of five vertebrae the calcium content was also measured in six small ROI. After completed scanning, six small cylinders were drilled out from each vertebra, and the ash-density of each cylinder was measured. The dual-energy CT measurements correlated well with the ash-density. Both ash-density and dual-energy CT showed a significantly higher mineral content in the posterior part of the vertebrae than in the anterior part, and this difference might be responsible for problems encountered with the reproducibility of dual-energy CT.     

Quantitative bone mineral analysis using dual energy computed tomography

This preliminary evaluation indicates that CT scanning permits measurement of cancellous, cortical or integral bone. With the single energy technique, precision is high and with mode, CT scanning may prove an important tool for assessing the axial skeleton is osteoporotic conditions.     

Effects of titanium prosthesis, offset and size of field of view on bone mineral density measurements using quantitative computed tomography

To estimate the accuracy of quantitative computed tomography (QCT) as a method to measure bone mineral density (BMD) in the vicinity of a titanium prosthesis, we investigated the effects of (1) titanium prosthesis, (2) offset of the longitudinal axis of the bone to be examined from that of the gantry of the CT scanner, (3) size of the field of view (FOV) and (4) the combination of these effects on CT based measurements of mineral density of cortical and cancellous bone specimens. 14 bovine cortical bone parallelepipeds and 14 bovine cancellous bone parallelepipeds were used in this investigation. The bone specimens were scanned with and without a titanium prosthesis, when centered in the gantry of the CT scanner and offset from the axis of the gantry of the CT scanner at a distance of 14 cm. Image data were then reconstructed separately with a FOV of 10 cm and 30 cm. All BMD values taken from CT images obtained under different scanning condition were compared with the BMD values of the corresponding bone parallelepiped obtained under standard condition (centered in the gantry of the CT scanner, 10 cm FOV, without titanium prosthesis). When centered in the gantry of the CT scanner, the mean relative difference of BMD measurements caused by the presence of the titanium prosthesis was less than 1% for both cortical bone and cancellous bone. Size of the FOV had a negligible effect on BMD measurements. Offset at 14 cm, however, caused a significant difference in BMD measurements (p < 0.001). It was concluded that titanium prosthesis did not interfere with BMD measurements of cortical and cancellous bone when both the specimen and prosthesis were centered in the gantry of the CT scanner. However, the effect on BMD measurements of offset at 14 cm combined with the presence of a titanium prosthesis in bone was significant.     

Evaluation of mineral bone content using quantitative computerized tomography

The authors have evaluated bone mineral content in the vertebral spongiosa by means of Computed Tomography. The method proposed by Genant and Cann has been applied to examine 164 healthy volunteers and 108 patients. Both healthy males and females showed a progressive bone mineral loss increasing with age; the bone mineral loss was most severe in females during the 4th and 5th decade of life. Pathology included patients with osteoporotic fractures (vertebral and femoral neck), patients with partial gastrectomy, renal failure, primary hyperparathyroidism, Cushing syndrome, corticosteroid therapy. Bone mineral values were significantly lower in most pathologic groups. Computed Tomography proves thus to be a valuable method to assess bone mineral content and to identify patients at risk for fractures.     

Effect of Paget's disease of bone on areal lumbar spine bone mineral density measured by DXA, and density of cortical and trabecular bone measured by quantitative CT

Although bone density may be increased in bone that is affected by Paget's disease, density changes in cortical and trabecular bone and the effect on bone that is apparently unaffected by Paget's disease are relatively unexplored. We have investigated 81 vertebrae (28 affected, 53 unaffected) in 27 patients with Paget's disease, by dual X-ray absorptiometry (DXA) and by quantitative CT (QCT) bone density measurements of trabecular and cortical bone. DXA bone density was high (mean z-score = 1.62, p < 0.001) in vertebrae affected by Paget's disease, but not significantly different from normal in unaffected vertebrae (mean z-score = 0.07, ns). Mean QCT z-score in Paget's vertebrae was 2.07 (p = 0.009) for cortical bone and 1.37 (p = 0.008) for trabecular bone. DXA correlated with QCT cortical values in affected and unaffected bone (r = 0.8 and 0.56, respectively), and with QCT trabecular values (r = 0.72 and 0.48, respectively). There was no significant difference in the slopes for the correlations in affected or unaffected bone. Cortical QCT values are underestimated in Paget's disease compared with physical measurements of density, owing to the computer algorithm used. High DXA values may alert to the possibility of Paget's disease, especially if the value deviates from the expected normal sequence in lumbar vertebrae. Osteoporotic vertebrae may be overlooked if the average value of bone mineral density is taken in the lumbar spine without reviewing each vertebra.