Biomedical subjects

D Felsenberg

Publications and source records attributed to D Felsenberg.

At least 73 records · Page 4Linked to original sources

PubMed1995

European semi-anthropomorphic spine phantom for the calibration of bone densitometers: assessment of precision, stability and accuracy. The European Quantitation of Osteoporosis Study Group.

Up to now it has not been possible to reliably cross-calibrate dual-energy X-ray absorptiometry (DXA) densitometry equipment made by different manufacturers so that a measurement made on an individual subject can be expressed in the units used with a different type of machine. Manufacturers have adopted various procedures for edge detection and calibration, producing various normal ranges which are specific to each individual manufacturer's brand of machine. In this study we have used the recently described European Spine Phantom (ESP, prototype version), which contains three semi-anthropomorphic "vertebrae" of different densities made of stimulated cortical and trabecular bone, to calibrate a range of DXA densitometers and quantitative computed tomography (QCT) equipment used in the measurement of trabecular bone density of the lumbar vertebrae. Three brands of QCT equipment and three brands of DXA equipment were assessed. Repeat measurements were made to assess machine stability. With the large majority of machines which proved stable, mean values were obtained for the measured low, medium and high density vertebrae respectively. In the case of the QCT equipment these means were for the trabecular bone density, and in the case of the DXA equipment for vertebral body bone density in the posteroanterior projection. All DXA machines overestimated the projected area of the vertebral bodies by incorporating variable amounts of transverse process. In general, the QCT equipment gave measured values which were close to the specified values for trabecular density, but there were substantial differences from the specified values in the results provided by the three DXA brands. For the QCT and Norland DXA machines (posteroanterior view), the relationships between specified densities and observed densities were found to be linear, whereas for the other DXA equipment (posteroanterior view), slightly curvilinear, exponential fits were found to be necessary to fit the plots of observed versus specified densities. From these plots, individual calibration equations were derived for each machine studied. For optimal cross-calibration, it was found to be necessary to use an individual calibration equation for each machine. This study has shown that it is possible to cross-calibrate DXA as well as QCT equipment for the measurement of axial bone density. This will be of considerable benefit for large-scale epidemiological studies as well as for multi-site clinical studies depending on bone densitometry.

Absorptiometry, Photon↗

PubMed1995

The European Spine Phantom--a tool for standardization and quality control in spinal bone mineral measurements by DXA and QCT.

The lack of standardization in bone mineral measurements of the lumbar spine and other skeletal sites is generally recognized as an important and unresolved issue. We report and discuss efforts at standardization and cross-calibration of DXA and QCT equipment. We have designed and tested a geometrically defined, semi-anthropomorphic phantom, the European Spine Phantom (ESP). It contains a spine insert consisting of three vertebrae of increasing bone mineral densities and thicknesses of cortical structures; the respective parameters are given in tabular form for the final phantom design. Results for cross-calibration with the ESP compare well with patient results. Measurements on the first 30 phantoms confirmed that the ESP can be manufactured with a variation of about 1%. We conclude that the ESP is suitable for daily quality assurance, cross-calibration of instruments and universal standardization. The ESP was used to establish standardized BMD (sBMD) units for DXA equipment going into effect in late 1995. Its acceptance by manufacturers as a calibration standard for DXA and QCT measurements appears imminent.

Absorptiometry, Photon↗

PubMed1995

Recent developments in DXA. Quality of new DXA/MXA-devices for densitometry and morphometry.

The introduction of new devices demands the assessment of their capabilities in established terms. The accuracy, reproducibility and spatial resolution of in vitro (phantom) osteodensitometric and morphometric measurements of QDR 2000 Plus and EXPERT are presented. Design details of these DXA/MXA-devices are listed and discussed in combination with the data acquired in the test measurements and calculations. The image quality will improve with further software developments. The long-term reproducibility and in vivo reliability remains to be evaluated.

Absorptiometry, Photon↗

PubMed1995

Dual X-ray absorptiometry--cross-calibration and normative reference ranges for the spine: results of a European Community Concerted Action.

Bone density measurements by dual X-ray absorptiometry (DXA) of the spine can now be made precisely, but there is no uniformity in reporting results and in presenting reference data. A European Union Concerted Action therefore devised a uniform procedure for cross-calibrating and standardizing instruments, using the European spine phantom (ESP) prototype. This phantom differs in a number of respects from the final version of the ESP. Eighteen centers in nine countries obtained 1619 records (1035 women) from Caucasian subjects, aged 20-80 years, drawn from normal populations. The DXA machines used were made by the Hologic, Lunar, and Norland companies. Highly statistically significant differences were evident between populations, both in apparent rates of bone loss with age and in the spread of values about the age-adjusted means. There were small residual differences in the results obtained with the three machine brands which could have been due to the relatively large between-center population differences we observed. The alternative or additional explanation that they were attributable, in part, to the design differences between the ESP prototype and the definitive ESP, which became available after this study was completed, was shown to be a valid possibility. Results from postmenopausal women reported in relation to the years that have elapsed since menopause showed reduced population variance when compared with conventional reporting in relation to age. After cross-calibration, the center with the highest age-adjusted normal density value averaged 23% more than the center with the lowest. It is therefore crucially important to select appropriate reference data in clinical and epidemiological studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗

PubMed1995

Vertebral fractures in men and women: how discriminative are bone mass measurements?

Vertebral fractures are associated with osteoporosis. This study examined men and women with vertebral deformation/fractures, as defined by vertebral morphometry. These were compared with a population derived group measured contemporaneously who were defined as having no vertebral deformation/fracture by the radiographs. All patients underwent a dual energy X-ray absorptiometry (DXA) scan of the spine and hip, and a broadband ultrasound attenuation (BUA) scan of their os calcis. The abilities of these two techniques were compared for their discriminatory powers in this type of fracture. The results showed that DXA hip and spine had a better discriminatory power in the female vertebral group compared with BUA. In males none of the bone measurements could discriminate between the fracture and non-fracture groups.

Absorptiometry, Photon↗

PubMed1995

[Value of transdermal hormone substitution for postmenopausal osteoporosis].

The osteoporosis is a major public health problem occurring primarily among the postmenopausal women. The relationship to the loss of ovarian function is undoubtful. The consequence of this knowledge is to substitute the hormone deficiency. Hormone replacement therapy (HRT) is effective with oral, subcutaneous, parenteral, and transdermal application. The transdermal hormone replacement therapy for prevention and therapy (early phase) of postmenopausal osteoporosis is effective and sure. The osteoprotective effect was demonstrated in multiple studies. The effectiveness of the HRT can be demonstrated by osteodensitometry and measuring markers of bone resorption.

Administration, Cutaneous↗

PubMed1994

Variation in vertebral height ratios in population studies. European Vertebral Osteoporosis Study Group.

Vertebral height ratios are used to define vertebral deformity in clinical and epidemiologic studies of vertebral osteoporosis. However, few data have been obtained on the variation in these ratios in different populations using standard methods. We examined vertebral morphometric measurements obtained in a population survey from three centers: Malmö (Sweden), Montceau-les-Mines (France), and Graz (Austria), to study the influence of sex and the population center on vertebral height ratios. Radiographs were obtained according to a standardized protocol, and morphometric measurements, anterior height Ha, central height Hc, and posterior height Hp, made in Berlin. The height ratios anterior, Ha/Hp, central, Hc/Hp, posterior I, Hp/Hp', and posterior II, Hp/Hp" (Hp' = posterior height of vertebrae above, Hp" = posterior height of vertebrae below) were calculated for each vertebra from T4 to L4. The mean and standard deviation of these ratios for each sex and each center were derived using a statistical trimming procedure to normalize the distribution. Threshold values for defining grade 1 and grade 2 deformities, wedge, biconcavity, and compression, were calculated using these parameters. Anterior and central vertebral height ratios were smaller in males than females (p < 0.01). There were significant differences between the three centers (p < 0.01) both in the trimmed mean values for anterior and central vertebral height ratios and in the thresholds derived using standard criteria for defining wedge and biconcavity deformity. The data confirm the impression from single-center studies that vertebral height ratios vary between populations and suggest that reference values for vertebral height ratios should be derived separately for males and females within individual populations whenever possible.

Aged↗

PubMed1994

European semi-anthropomorphic phantom for the cross-calibration of peripheral bone densitometers: assessment of precision accuracy and stability.

A semi-anthropomorphic 'distal radius like' phantom, developed by Kalender and Ruegsegger for use in peripheral bone densitometry using single photon (DPA) dual X-ray (DXA) and quantitative computed tomography (QCT) machines, has been studied with a view to cross-calibrating different types and brands of densitometers in current use. In the context of an EU 'Concerted Action' (second Framework Programme) the phantom was repeatedly measured on six SPA machines, three DXA machines and nine QCT machines (545 measurements). Linear regression equations were derived, individual to each machine, which allowed the derivation of 'standardized densities'. In this way we converted measurements made by machines of the same modality to a common scale of measurements. Two machines (one DXA, one SPA) showed statistically significant instability over time emphasising the need for rigorous quality control in the application of densitometry. In other respects these results provide an encouraging basis for the derivation of standardized normative ranges and the more effective use of peripheral densitometry in future clinical and epidemiological studies.

Absorptiometry, Photon↗

PubMed1994

[MRI of the knee joint of young soccer players. Are there early changes of the internal structures of the knee due to competitive sports?].

In a prospective study, the right knee of 21 symptom free juvenile footballers was examined by MRT (group I) and the results were compared with 12 juveniles of similar age but who did not take part in any special sporting activities (group II). A 1.5 Tesla Magnetome with an extremity coil was used. There were no abnormal changes in either group in the cruciate ligaments. The hyaline cartilage medially was about 10% thicker than laterally in both groups but in group I it was, on average, 24.8% thicker than in group II. Increased signals in the centre of the menisci were observed in 8 members of group I and two in group II. 5 of the 8 in group I, but none in group II, also showed an increase in the joint fluid.

Adolescent↗

PubMed1994

[The quantitative determination of bone mineral content--a system comparison of similarly built computed tomographs].

An intercomparison of 4 CT scanners of the same manufacturer was performed. The bone mineral content of 11 lumbar vertebral columns removed directly post mortem was determined in a specially constructed lucite-water phantom. Even devices of the same construction were shown to yield a variation in the quantitative evaluation markedly exceeding the annual physiological mineral loss. As long as scanner adjustment by physical calibration phantoms has not yet been established, a course assessment and therapy control of bone mineral content should always be carried out on the same QCT scanner.

Absorptiometry, Photon↗

PubMed1993

Comparison of computed tomography, endosonography, and intraoperative assessment in TN staging of gastric carcinoma.

From 1986 to 1990 a prospective comparative study was undertaken to compare the relative accuracy of computed tomography, endogastric ultrasonography, and intraoperative surgical assessment in evaluating the depth of invasion (T category) and involvement of lymph nodes (N category) of patients with gastric carcinoma. One hundred and eight consecutive patients, who were treated by total gastrectomy and previously evaluated with computed tomography, endogastric ultrasonography, and intraoperative surgical assessment, entered the study. Results (T and N category) were compared with those of histopathological staging (pT and pN category). T categories were correctly staged in 43% of cases with computed tomography, 86% with endogastric ultrasonography, and 56% with intraoperative surgical assessment. Computed tomography scanning correctly staged 51% of all N1 and N2 lymph nodes compared with 74% for endogastric ultrasonography and 54% for intraoperative surgical assessment. In general, computed tomography was more accurate for advanced stages of cancer and showed a tendency to overstage the T category and understage N category of gastric tumours. By contrast, endogastric ultrasonography was equally accurate for all T categories and showed an understaging for N categories. Intraoperative surgical assessment overstaged early T stages, understaged T4 tumours, and was equally accurate for all grades of N categories. Computed tomography scanning and intraoperative surgical assessment of T and N categories were of little value in staging of gastric carcinoma. Endogastric ultrasonography is more accurate than computed tomography scanning and intraoperative surgical assessment. Therefore endogastric ultrasonography should be introduced in the preoperative assessment of patients with gastric carcinoma.

Adult↗

PubMed1992

Compact and trabecular components of the spine using quantitative computed tomography.

A computer algorithm was employed to quantify separately cortical and trabecular bone mineral density (BMD) from single energy computed tomography (CT) scans of 139 vertebrae (L1-L3) of 50 normal female subjects. In addition, the trabecular-to-integral and cortical-to-integral mass ratios were determined using digital image segmentation techniques. They showed that for the central 8-mm vertebral slice, the mass of integral bone consists of about one-fifth trabecular and four-fifth cortical bone. The trabecular-to-integral volume ratios were 0.37 +/- 0.08 and 0.63 +/- 0.08, respectively. Based on cross-sectional data from this subject group, the average annual loss was -2.21 +/- 0.15 mg/cm3 or -1.84 +/- 0.12% for trabecular bone, -3.15 +/- 0.25 mg/cm3 or -1.01 +/- 0.08% for cortical bone, and -2.60 +/- 0.20 mg/cm3 or -1.09 +/- 0.09% for the integral bone. The proportions of the age-related loss of BMD from the integral bone which originated from trabecular and cortical bone were 29.5 and 70.5%, respectively.

Adult↗

PubMed1992

Long-term gonadal dysfunction and its impact on bone mineralization in patients following COPP/ABVD chemotherapy for Hodgkin's disease.

Only limited data is currently available on long-term gonadal toxicity and its impact on bone mineralization in men and women treated for Hodgkin's disease. The present study was therefore conducted to evaluate gonadal toxicity and bone loss in 49 patients with Hodgkin's disease 2-10 (median 5.37) years after chemotherapy. Most patients were treated with the COPP/ABVD regimen +/- irradiation according to the protocols of the German Hodgkin Study Group. Blood samples were tested for gonadotropins (FSH, LH), gonadal steroids, parathyroid hormone, osteocalcin, and calcitonin. Bone mineral density was measured using single- and dual-energy quantitative computed tomography as well as single-photon absorptiometry. FSH serum levels were significantly increased in 21/27 (80%) men demonstrating germ-cell aplasia. 13/15 (86%) men showed azoospermia after the COPP/ABVD regimen. In contrast, testosterone levels were within normal limits in all men tested, suggesting normal Leydig-cell function. 17/22 (77%) women exhibited increased FSH and LH levels, indicating premature ovarian failure. Women with therapy-induced ovarian failure had a significantly lower trabecular (98 +/- 34) and cortical (292 +/- 48 mg/cm3) spinal bone density than those with normal ovarian function. Men showed no evidence of bone loss after therapy. These data suggest severe gonadal toxicity in both men and women treated with the COPP/ABVD regimen. In female patients, drug-induced ovarian failure has a significant impact on bone mineralization.

Adolescent↗

PubMed1992

Determination of bone mineral density by quantitative computed tomography and single photon absorptiometry in subclinical hyperthyroidism: a risk of early osteopaenia in post-menopausal women.

OBJECTIVE: There is evidence that treatment with L-thyroxine increases the risk of early osteopaenia. The aim of our study was to investigate the effect of subclinical hyperthyroidism in patients on TSH-suppressive L-thyroxine in view of the increased risk of decalcification. DESIGN: Measurements of bone mineral density were performed in patients with subclinical hyperthyroidism at different scanning sites of varying trabecular portion. Bone mineral values as well as biochemical data were compared to those of normal controls. PATIENTS: Fifty patients (nine men, 25 premenopausal and 16 post-menopausal women) on TSH-suppressive doses of L-thyroxine were investigated after removal of thyroid cancer. MEASUREMENTS: Dual energy quantitative computed tomography was used for osteodensitometry in the lumbar spine. Single photon absorptiometry from a 125I source was applied to the calcaneus, midshaft radius and distal as well as proximal scanning sites of the distal radius. Normal bone mineral values for each measurement site were taken from healthy reference populations. RESULTS: A significant decrease of bone mineral density in the calcaneus was found in 26 of 50 patients. Bone mass assessment yielded a 9.1% decrease of mean bone mineral content in all patients compared to controls (P less than 0.01). The decrease in post-menopausal women was 22% (P less than 0.001). In premenopausal women bone mineral density changes in the calcaneus were not statistically significant. Cortical measurement sites like the midshaft radius and the proximal scanning site of the distal forearm showed a 14.8% (P less than 0.05) and 10.8% (P = NS) decalcification in post-menopausal women but normal values at the distal scanning site. The lumbar spine was not affected by subclinical hyperthyroidism in either pre or post-menopausal women. In hypoparathyroid patients, bone density did not essentially differ from normals. There was no significant correlation between bone mineral values and duration of treatment or osteocalcin values. CONCLUSIONS: Our data suggest that TSH suppressive L-thyroxine treatment has a detrimental effect on the appendicular skeleton in post-menopausal women. Additional effects of oestrogen deficiency and subclinical hyperthyroidism might lead to accelerated bone loss requiring close supervision to determine the smallest dose needed for suppression of the pituitary-thyroid axis.

Absorptiometry, Photon↗

PubMed1992

[Diagnosis of pneumatosis intestinalis coli in CT].

Pneumatosis intestinalis coli seldom causes symptoms of an acute abdomen and is rarely diagnosed in CT. The origin of the gas collections in the wall of the bowel often remains unclear. As shown in our case, pneumatosis may involve any portion of the bowel, but usually spares the rectum. Due to extreme meteorism and coprostasis it can be difficult to recognize pneumatosis radiographically. In CT the gas collections beneath the serosa are well defined, discrete, oval or round.

Female↗

PubMed1991

Global and regional variations in the spinal trabecular bone: single and dual energy examinations.

Two hundred and sixty-eight vertebrae from 92 subjects (42 males and 50 females) were used to assess inter- and intravertebral variations in the mineral content of spinal trabecular bone from L1-L3. Using a computer-generated grid superimposed on the trabecular bone, the spatial distribution of the mineral content was computed for 48 subdivisions of the grid for single and dual energy computed tomographic examinations. In addition, the age dependence of the mineral content was assessed by regression analysis from each subdivision. The results demonstrated a nonhomogenous distribution of mineral density within the trabecular bone. The lateral and anterolateral subcortical regions show significantly lower mineral density than the posterolateral or anterior subcortical domains. Moreover, with increasing age, bone density was also lost in a nonuniform fashion. Finally, the analysis of regional intervertebral change for the L1-L3 vertebrae revealed a nonhomogeneous pattern of mineral distribution.

Adolescent↗

PubMed1990

[CT examinations using a reduced radiation dosage].

An experimental method was used to determine which diagnostic CT problems could be solved while using reduced radiation doses. The examinations were carried out using 85 kv and 1.7 to 3.0 mGy (instead of the usual 125 kv and 20 to 50 mGy). More than 500 patients have been investigated so far. The method has been used successfully for bone mineral estimations and for otorhinologic and orthopaedic problems. All examinations with high contrast (bones, sinuses) and small diameters (extremities) produced adequate images compared with the usual pictures. With the exception of cerebral CT for demonstrating the brain (structures with little contrast), the method can also be used for children and infants. During the first phase of this study the role of this method has been evaluated. Subjective impressions and demonstration of detail, when compared with a 'normal' image for a corresponding cut, were satisfactory. Signal-to-noise ratio was measured by a quantifiable parameter of image quality.

Humans↗

PubMed1989

[Computerized tomography determination of bone mineral content in quantitative diagnosis of osteoporosis].

Quantitative determination of bone mineral content has become important for the early diagnosis of osteoporosis prior to radiological evidence of vertebral deformities. Quantitative CT (QCT, computer tomometry), whether the single-energy (SE-QCT) or the dual-energy (DE-QCT) technique is used, yields volume-related values that can be used for accurate and reproducible assessment of spongious and cortical vertebral bone mineral. QCT seems to be superior to photon absorptiometry for early detection and follow-up of osteoporosis.

Adult↗