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.     

Comparative study of bone mineral density estimated by various methods of single- and dual-energy quantitative computed tomography: the capability of the four-equation four-unknown method

A dual-energy (DE) quantitative computed tomography (QCT) method, the four-equation four-unknown method (DEQCT 4E-4U), was assessed and compared to single-energy (SE) QCT and standard DEQCT (two-line method). The results of this study indicate that bone mineral density (BMD) was more accurately estimated by the present method than by the SEQCT or standard DEQCT techniques on the basis of a phantom study when a large fat content was present. The results of both the phantom study and a human study also showed that the present method corrected for fat in estimating BMD in the presence of high-fat content. These findings suggest that use of this method for estimating BMD can provide useful information in studies assessing the metabolic state of bone. We propose that CT numbers estimated from excised vertebral bone marrow can serve as a soft-tissue correction for the present method.     

Dual-energy X-ray absorptiometry for histologic bone sections

In fundamental osteoporosis research precise and accurate assessment of the mineral quantity in histological bone sections is of particular importance when studying the local effects of implants releasing bone modulating agents. A potentially useful technique to estimate the bone mineral density (BMD) is dual-energy X-ray absorptiometry (DXA). A highly collimated (0.13 mm) Hologic 2000 with a line spacing and point resolution of 0.13 mm was used. The mineral content was measured in regions of 3.1 mm(2). A ceramic hydroxyapatite (CHA) phantom was developed as a reference standard. The phantom was made of a single-phase hydroxyapatite starting powder by compressing and sintering at 1000 degrees Celsius. The true density was 3.14 + or - 0.001 g/cm(3). The calcium/phosphorus ratio was close to the theoretical one of 1.67. The mean precision error expressed as the coefficient of variation (CV) of the mineral density (MD) measurements of the phantoms with thicknesses of 1, 2, and 3 mm was 0.2%. Embedded undecalcified alveolar bone sections of dogs (0.0015-1 mm in thickness) were scanned simultaneously with a phantom 1 mm in thickness. The precision error (CV) of the BMD measurements calculated by DXA for sections > or = 0.1 mm and with a BMD > or = 0.14 g/cm(2) was 0.81%. There was a linear relationship between the BMD calculated by DXA and the estimated BMD in the histological bone sections by means of the true density of the phantom. It is concluded that DXA using a standard CHA phantom is a precise and accurate method to measure MD changes as small as 1% in histological bone areas of 3.1 mm(2) provided that the loss or gain in BMD is > or = 0.14 g/cm(2).     

Software upgrading in a CT scanner. Influence on quantitative CT

PURPOSE: In an attempt to improve field uniformity and CT number stability, the software in a CT scanner was replaced with a new version. The purpose of the present study was to investigate the influence of the software upgrading on density measurements. MATERIAL AND METHODS: The upgrading influence was investigated by means of a torso phantom (European spinal). The phantom simulates a torso which contains 3 vertebrae of different densities. RESULTS: Despite the use of a reference standard under the phantom, the software change resulted in: a) improved short-term precision; b) increased density values at 80 and 100 kVp, decreased at 130 kVp; and c) increased influence of the kVp on the values. CONCLUSION: The results of the present study suggest that conversion factors have to be used in density values for reference populations as well as in the values of patients undergoing follow-up studies.     

The effect of retinal cryoapplication on the vitreous

Long-term clinical trials using bone mineral density (BMD) measurements are now commonplace. It is important to maintain a high standard of quality control. In this study two methods of monitoring quality control measurements of dual-energy X-ray absorptiometry (DXA) equipment have been compared using receiver operating curve (ROC) analysis: Shewhart multi-rule charts and Cusum charts. Computer-generated faults within daily spine phantom measurements were used. The Charts were then applied to 3 years of quality control data from one machine and the results related to hardware faults, random events and changes in the underlying BMD measurement. In the ROC analysis the Shewhart multi-rule chart performed as well or better than the cusum chart, but the stringency of the rules must be tightened to obtain optimal performance.     

The remineralization of the vertebral metastases of breast carcinoma after radiotherapy

BACKGROUND: The early detection of effects caused by radiotherapy on bone mineralisation has influence on clinical treatment. Usually the follow-up is done by conventional X-rays, presenting a loss of calcification of at least 30%. Quantitative CT-measurements are much more sensitive. PATIENTS AND METHODS: In a prospective study we evaluated the CT-scans of 14 patients with multiple vertebral metastases of mamma carcinoma. Our patients underwent SEQCT (one 10 mm slice in each affected vertebral body, 80 kV, 250 mAs) before and immediately after radiation therapy (total dose 30 Gy to 36 Gy) followed by further examinations 6 weeks and 3 months later. RESULTS: While there is no significant change in increased BMD (bone mineral density) of osteosclerotic and decreased BMD of osteolytic metastases just after therapy, the following examinations present an increase of BMD in osteolytic metastases 6 weeks after therapy more distinct 3 months after. Osteosclerotic metastases show a decline in bone density. In mixed metastases is no significant change while normal bone lying in the irradiation field demineralizes. Additive chemotherapy is very important especially for mineralisation of lytic metastases. Referring to mixed metastasis in one vertebral body we suggest a separate evaluation of the left and right side. CONCLUSION: Mineralizing effects of radiation therapy depend on the characteristics of the metastases. Supported by QCT histopathological change can be documented and exactly demonstrated to the clinician.     

Monophosphoryl lipid A induces delayed preconditioning against cardiac ischemia-reperfusion injury

Quantitative ultrasound (QUS) bone measurement is a promising, relatively new technique for the diagnosis of osteoporosis. Unlike to the more established method of bone densitometry [measurement of bone mineral density (BMD) e.g. using dual X-ray absorptiometry (DEXA)], QUS does not use ionizing radiation. It is cheaper, takes up less space and is easier to use than densitometry techniques. The two QUS parameters currently measured are broadband ultrasound attenuation (BUA) and speed of sound (SOS). The reported age-related changes for healthy women range from -0.27% to -1.62% per year for BUA and from -0.06% to -0.19% per year for SOS. Precision ranges from 1.0 to 3.8% (CV) for BUA and from 0.19 to 0.30% (CV) for SOS. The new method of imaging ultrasound has improved the precision of QUS measurements. QUS is significantly correlated with BMD. Studies with the latest equipment have shown r-values between 0.6 and 0.9 in site-specific measurements, and QUS is thus believed to reflect mainly BMD. However, other studies indicate that QUS measures something other than the actual mineral content of bone, namely bone quality, e.g. in vitro studies have shown that QUS reflects trabecular orientation independently of BMD. In both cross-sectional and prospective studies, QUS seems to be as good a predictor of osteoporotic fractures as BMD. In two large prospective studies, QUS also predicted fracture risk independently of BMD. QUS has just begun to be used systematically for monitoring the response to anti-osteoporotic treatments in prospective trials. In the studies performed, QUS has been found to be useful in the follow-up of patients. QUS is thus a promising new technique for bone assessment.     

Evaluation of peripheral dual energy X-ray absorptiometry: comparison with single photon absorptiometry of the forearm and dual energy X-ray absorptiometry of the spine or femur

An evaluation of the Osteoscan peripheral dual energy X-ray absorptiometer (pDXA) was carried out to compare its performance with those of a single photon absorptiometer (SPA) (Molsgaard Medical ND1100A) and a dual energy X-ray absorptiometer (DXA) (Lunar DPX alpha) of the spine or femur. In 57 patients, correlation between bone mineral content (BMC) of the forearm at the ultradistal (UD) site by pDXA and by SPA was high (r = 0.94). Comparisons were also made with spine and femur bone mineral density (BMD) DXA measurements. The correlation of z-scores of UD BMD with z-scores for lumbar spine L2-L4 was r = 0.63 (n = 73 patients); and with z-scores for neck of femur was r = 0.72 (n = 33). With the Osteoscan the measurement error coefficient of variation in vivo was 2.6% for BMC, 1.8% for BMD at the ultradistal site; 2.1% for BMC and 1.9% for BMD at the mid-distal site. Repeat measurements were made of the European forearm phantom; precision for SPA was slightly better than either pDXA or Lunar DXA. The Osteoscan has the potential for a rapid throughput of patients and is not affected by calcification and degenerative changes that can corrupt DXA measurements on the anteroposterior spine in older women.     

Spatial distribution of femoral bone mineral in dual energy X-ray absorptiometry images: a possible technique to improve discrimination between normal and osteoporotic patients

The measurement of bone mineral density (BMD) using dual energy X-ray absorptiometry (DXA) provides an indicator of subsequent risk of hip fracture, but because of the significant overlap of measurements obtained from osteoporotic and control groups its predictive power is limited. The radiographic technique of Singh grading for the assessment of femoral osteoporosis utilizes information about the distribution of trabecular bundles, but the morphological information available in the DXA image has not previously been analysed. In this study of DXA images from 64 individuals (32 controls and 32 classified as osteoporotic) a subjective grading technique analogous to Singh grading is proposed, and quantitative measurements are made of image features corresponding to two of the categories. Discrimination was assessed using receiver operating characteristic (ROC) curves: the best discrimination was by spinal BMD (Az = 0.85 +/- 0.05) a performance equalled by one of the new parameters; the subjective grading method (Az = 0.79 +/- 0.07) performed as well as measurements of BMD in the femur. These results suggest that although the alternative measures do not improve on the discrimination possible using spinal BMD, morphological information from the hip itself may in the future have a place in the assessment of bone quality.     

Low-dose spiral computed tomography for measuring abdominal fat volume and distribution in a clinical setting

OBJECTIVES: Computed tomography (CT) has been used to measure body composition, however, a technique with reduced radiation exposure has not yet been introduced. This study tested a low-dose spiral CT technique on a phantom to determine its validity and reproducibility. The method was then applied for volume and distribution measurements in patients. DESIGN: Construction and measurement of a phantom followed by measurement of patients referred to CT for clinical indications. SETTING: Radiology Department, University Hospital. SUBJECTS: Twenty-four post-gastrectomy patients. INTERVENTION: A 22 cm phantom with a known amount of water and fat was scanned using high- and low-dose technique, standard and double table speed during a volumetric scan. The low-dose technique was implemented in the patient group. Total volume, total fat and four defined compartmental fat volumes in the truncal area were measured. RESULTS: The mean fat volume measured using the low-dose CT technique in the phantom was 0.2% above the actual fat content. The coefficient of variation for this method was 5%. By using low-dose, double speed instead of standard-dose technique, radiation exposure to the skin was decreased by more than 90% (equivalent to 4 mGy) of what is used in diagnostic imaging. The patient scans showed that no significant differences in BMI and total measured volume existed between female and male patients, but percent fat and percent subcutaneous fat were significantly larger in women (P = 0.006 and 0.002, respectively), as were percent intraabdominal and mediastinal fat in men (P = 0.002 and 0.003 respectively). CONCLUSIONS: Low-dose spiral CT accurately measures fat volume in vitro, and can be used in vivo for compartmental fat measurements.     

Effectiveness of screening for osteoporosis by bone density measurement for the prevention of fractures: a review of the evidence]

To review evidence on the benefits of screening women and men for osteoporosis, a Pub Med search was performed in English papers published between 1990 and 2002. We used data from a cohort study to estimate risk of fracture from bone mineral density. Bone mineral density measured by dual X-ray absorptiometry (DXA) can predict bone fracture among elderly women, peri- and early post-menopausal women, and elderly men. It is recommended that all white women older than 65 years be screened routinely for osteoporosis. We suggest that Japanese elderly women should receive BMD measurements as a screening, but we have still issues to be solved including age from when the screening should be started, methods, and how to treat the women found to have osteoporosis at the screening. For peri- and postmenopausal women and elderly men, it might be beneficial to measure BMD as a screening and start treatment for those patients found to have osteoporosis. However, incidence of fractures for these people is lower than that for elderly women. One bone mass measurement can predict bone fracture risk for as long as over 10 years or more, but predictive ability of BMD decreases with time. Therefore, cost effectiveness needs to be reviewed to determine the benefits of screening among peri-menopausal women and men. Although bone assessment by quantitative ultra sound (QUS) method by ultrasound can also predict future fractures, only a relatively small number of longitudinal studies have been conducted in the Western countries, and there is no established evidence by means of longitudinal studies among Japanese. It is necessary in Japan to seek such evidence, however, since this method is widely used for an osteoporosis examinations.     

Computerized radiographic analysis of osteoporosis: preliminary evaluation

Measurement of bone mass is important in determining the risk for fracture and in following the course of patients undergoing therapy for osteoporosis. Bone mineral densitometry (BMD) is a good predictor of fracture risk, but there is considerable overlap in BMD measurements between individuals with fracture risk and those without. In this study, computerized texture analysis of the trabecular pattern on conventional spine radiographs was used to evaluate bone structure as a determinant of fracture risk. Standard lumbar spine radiographs of 43 individuals were analyzed and compared with BMD measurements obtained with dual-photon absorptiometry. This method was more effective than BMD in differentiation of patients with fractures elsewhere in the spine from those with no fracture. These preliminary results suggest that this method of bone structure analysis, combined with BMD, may lead to a more sensitive and specific predictor of osteoporosis and risk of fracture.     

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

PURPOSE: 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. METHOD: 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). RESULTS: 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). CONCLUSION: 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.     

Bone ultrasound and diagnosis of osteoporosis: correlation of 2 quantitative ultrasound methods with bone density

In this study, 96 women (mean +/- SD, 65.3 +/- 13.2 years) were investigated by bone mineral densitometry (DXA, Hologic QDR 2000) and quantitative ultrasound (QUS) of the tibia (n = 96; Sound-Scan2000, Myriad) and phalanges (n = 84: DBM Sonic 1200, IGEA). We observed a good correlation of QUS measurement with bone mineral content (BMD) on lumbar spine and both hips (Ward and Neck). Correlation of the two QUS-techniques measuring at different skeletal sites within the same patient was good. QUS instruments measuring at the various skeletal sites and their suitability for screening patients at risk of osteoporosis are discussed. The usefulness of the different QUS methods and the best measuring site for the assessment of fracture risk in osteoporotic patients still have to be established.     

A comparison of bond strengths of complete crowns using two types of cements and three cleaning agents

In the past, biomechanical investigations on the dorsal pelvic ring have generally been performed on a small number of cadaveric pelves in various non-standardized procedures. Significant differences in stability between different internal fixation methods of unstable pelvic ring fractures were not found. The experimental design presented here was based as closely as possible on the physiological loading of the pelvis in one-leg stance. This method made it possible to carry out standardized, reproducible tests on different osteosytheses of the sacroiliac joint. Furthermore, the suitability of artificial bones for such investigations can be assessed on the basis of a larger number of similar experiments on artificial and human pelves and the number of human pelves required for such studies could be reduced.     

Neuroepithelial bodies in relatively mature lungs: an investigation in prenatal and newborn lambs

Total body and leg bone mineral densities (BMD) were measured in 42 severely handicapped children and adults using a dual energy X-ray absorptiometry (DEXA) (LUNAR Radiation Corp., DPX). Despite the differences in motor ability and nursing history, about 95% of patients, except for 2 cases, were diagnosed as having osteopenia. The degree of osteopenia was dependent on the motor disabilities of their original disease. Therefore we should bear in mind a precaution and therapy from early period. Because BMD of the legs in females were less than -3 SD of the age-matched control values, we should be careful for a possible fracture of femur. Since X-ray hazard of DEXA for patients is considerable to be negligible, this will provide an effective means for quantifying bone mineral in severely handicapped patients.     

Measuring L-dopa in plasma and urine to monitor therapy of elderly patients with Parkinson disease treated with L-dopa and a dopa decarboxylase inhibitor

We have established a method for measuring L-dopa in plasma and urine, including the metabolites dopamine and L-dopac, using separation by ion-pair reversed-phase HPLC and quantification with an electrochemical detector. The assay was applied to the therapeutic monitoring of elderly patients with established Parkinson disease being treated with L-dopa plus a dopa decarboxylase inhibitor. Plasma L-dopa was evaluated in relation to dosage and postdose sampling time in 71 outpatients with Parkinson disease. L-Dopa concentrations were greatest in the patients taking the highest dosages prescribed and decreased significantly with increasing time after postdose sampling. Comparison of plasma L-dopa concentrations with a published therapeutic range established by intravenous administration of L-dopa was helpful in assessing the suitability of each patient's drug dosage, assessing patients' compliance, and avoiding overdosage but was not useful in the overall clinical assessment of progression of disease or of the long-term therapeutic response. Urine measurements confirmed the plasma concentrations but showed no further advantage. The recommended time for sample collection is between 1.5 and 3 h after the first morning dose. Plasma is the preferred matrix but if blood sampling is difficult, particularly from elderly/infirm individuals, an untimed urine collection could be used.     

Mitochondrial aspartate aminotransferase isoenzyme: a biochemical marker for the clinical management of alcoholics?

Serum mitochondrial and total aspartate aminotransferase activity was quantified by a characterized immunochemical method in 126 subjects, 44 healthy controls and 82 chronic alcoholics (51 outpatients and 31 monitored through 15 days). The monitored alcoholics were divided into actual abstinents (n = 21) and drinkers (n = 10) by blood ethanol concentration performed daily. The aims of the present study were: (a) to compare the diagnostic diagnostic usefulness of the mitochondrial isoenzyme and the mitochondrial/total aspartate aminotransferase ratio to detect problematic drinkers; (b) to evaluate the suitability of these indices to monitor abstinence, a difficulty not yet solved in the clinical management of alcoholics. The results demonstrated the mitochondrial isoenzyme to be more suitable to discriminate between controls and alcoholics (Kruskal and Wallis ANOVA, Bonferroni test, P < 10(-5) and mostly between actual drinkers and other alcoholics (P < 0.041). So acute alcohol consumption may be a significant, suggestive and until now inadequately examined factor in evaluating the suitability of mAST as a marker. The results, showing that mAST peaks quickly appear in the presence of a new alcohol intake, should indicate mAST as a possible marker of acute alcohol intake useful in checking self-claimed abstinence.     

Gadolinium-enhanced breath-hold three-dimensional time-of-flight MR angiography of the abdominal and pelvic vessels: the value of ultrafast MP-RAGE sequences

MR angiography (MRA) was performed in 50 consecutive subjects (mean age, 59 years), who had been referred for abdominal MRA, on a 1.5-T superconductive unit that used a body phased-array coil. Three breath-hold three-dimensional sequences were evaluated both in phantom and clinical studies: (a) standard fast three-dimensional gradient-echo sequence (TR = 15, TE = 6; imaging time, 32 seconds), (b) ultrafast three-dimensional gradient-echo sequence (TR = 8.2, TE = 3; imaging time, 18 seconds), and (c) ultrafast magnetization-prepared (MP) rapid acquisition gradient echo (RAGE) (TR = 5.8, TE = 2.9, inversion time [TI] = 20; imaging time, 15 seconds). The initial 30 patients were randomized into three groups by three separate sequences. For the remaining 20 patients, ultrafast-gradient-echo and ultrafast MP-RAGE sequences were performed. Conventional angiography was performed on 36 patients. Signal measurements of the phantom and clinical images of the aorta, visceral branches of the aorta, iliac arteries, inferior vena cavae, and portal veins were performed. The overall image quality and background fatty tissue contrast of the vessels were rated subjectively. Comparison of images between MRA and conventional angiography also was performed. The contrast between the vessels and background fatty tissue was significantly higher in the ultrafast MP-RAGE sequence in both quantitative and qualitative analysis, and image-quality ultrafast MP-RAGE was superior to the other two sequences (P < .01). The aorta and iliac arteries could be visualized in all pulse sequences, and abnormalities of these vessels were diagnosed correctly. The renal artery was visualized more clearly with the two ultrafast sequences.