Biomedical subjects

C Glüer

Publications and source records attributed to C Glüer.

7 recordsLinked to original sources

PubMed2002

Bone densitometry in children: a critical appraisal.

Due to the introduction of new therapeutic regimen aimed at increasing and maintaining bone mass, bone densitometry in children has gained interest. As in all new fields of medicine we expect the interest in bone densitometry in children to increase in the coming years. Children pose a unique problem for those involved in the field of bone densitometry, because as time progresses the measured subject changes in shape and volume. It is therefore of importance that radiologists and clinicians gain insight in the available techniques. It is also important to keep in mind that all bone densitometry techniques have been exclusively designed, developed and validated for use in an adult population. In this article we give an overview of the available techniques and discuss the specific problems that can be expected when these techniques are used in children. In the discussion section general problems regarding bone densitometry in children are presented.

Absorptiometry, Photon↗

PubMed2000

Quantitation of renal perfusion using arterial spin labeling with FAIR-UFLARE.

Quantitative perfusion imaging of human kidneys was performed using arterial spin labeling MRI with a fast spin echo readout-sequence. Perfusion maps of centrally located single slices were obtained in axial and coronal orientations. In ten healthy volunteers, the mean value of perfusion was 213+/-55 mL/(100g min) with a range from 140 to 319 mL/(100g min). These results are in accordance with literature data, considering the fact that FAIR only measures the perfusion component normal to the imaging plane. Intra-individual reproducibility errors of +/-11% were smaller than the natural interindividual variability of renal perfusion (SD = +/- 25%). Perfusion in the cortex was approximately 3-4 times higher compared to the medulla. Considering the relatively high resolution of 2x2x10 mm3, the ability to quantify perfusion, and the lack of ionizing radiation and contrast media, this technique should prove useful in diagnosing renal pathologies that are associated with reductions in tissue perfusion.

Adult↗

PubMed1998

Ultrasound characterization of bone demineralization.

Quantitative ultrasound (QUS) assessment of bone may permit an assessment of bone properties currently not available by bone densitometry techniques. To explore the effects of the quantity of bone mineral on acoustic parameters, we carried out an in vitro study of the impact of demineralization on attenuation of ultrasound in trabecular bone. Ten fresh cubes of trabecular bone obtained from bovine distal femurs were progressively demineralized using formic acid solution. The progression of demineralization was controlled by monitoring the specimen bone mineral density (BMD) using dual x-ray absorptiometry (DXA). At five stages of demineralization-0% (baseline), 25%, 50%, 75%, and 100% (all mineral removed)-the US properties of the specimens were assessed (Walker Sonix UBA 575+). The US parameters investigated were broadband ultrasound attenuation (BUA) and ultrasound attenuation in bone (UAB). Both DXA and QUS measurements were made along the three orthogonal axes of each cube. Our results demonstrated significant variability in both BUA and UAB along the three principle axes of the cubes whereas BMD did not differ in the different directions. A strong but nonlinear correlation was found between BMD and US attenuation. A reduction in BMD to 50% of the baseline values resulted in BUA (UAB) reduction to 25% and 19%, respectively. A random effect model analysis supported a multiplicative relationship between BMD and the US parameters. US attenuation is a sensitive indicator of bone mineral changes with nonlinear dependence on bone mineral loss. Bone collagen structure reinforced by hydroxyapatite crystal accounts for fundamental US characteristics. Ultrasound attenuation associated with trabecular orientation is basically dominated by the mineral spread in a collagen framework.

Absorptiometry, Photon↗

PubMed1997

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.

Absorptiometry, Photon↗

PubMed1996

Advances in the noninvasive assessment of bone density, quality, and structure.

Recent advances in the development of methods to assess the skeleton noninvasively have contributed to screening for risk of osteoporosis, early detection of the disease, and effective monitoring of its progression and response to therapy. The capability now exists to evaluate the peripheral, central, or entire skeleton as well as the trabecular bone or cortical bone envelopes accurately and precisely, with the capacity to determine bone strength and predict fracture risk. In this article we examine the current and future capabilities of quantitative computed tomography (QCT), quantitative ultrasound (QUS), and magnetic resonance microscopy (muMR) to assess architectural and densitometric properties of the skeleton to enhance the prediction of fracture risk.

Female↗

PubMed1992

[Radiologic diagnosis of osteoporosis. Current methods and outlook].

Osteoporosis is defined as a decrease in bone mass and structural changes in bone leading to an increase in fractures. Early diagnosis as quantification of prophylaxis and treatment are of great interest. A number of non-invasive techniques are available for measuring bone mass at multiple sites of the skeleton. This article reviews basic methodology and developments in radiography as in x-ray or gamma photon absorptiometry, quantitative computed tomography, ultrasound velocity and attenuation and magnetic resonance imaging. Clinical applications of these methods are discussed. The still experimental use of ultrasound and MRI in assessment of bone-mineral content may also give information on bone quality.

Absorptiometry, Photon↗

PubMed1991

Osteoporosis. Current techniques and recent developments in quantitative bone densitometry.

Knowledge about the proper use and interpretation of bone densitometry studies and an understanding of appropriate medical interventions are not universal among physicians, nor are instrumentation and technical performance of bone density studies of uniformly high quality. Indeed, this deficiency of medical and technical expertise is the principal deterrent to widespread implementation of our recommended clinical applications at this time. Nonetheless, given the current impetus to disseminate information about osteoporosis, to make newer instrumentation more readily available, and to limit the cost of these techniques, we anticipate that our recommendations may soon become standard medical practice.

Absorptiometry, Photon↗