Biomedical subjects

C-C Glüer

Publications and source records attributed to C-C Glüer.

8 recordsLinked to original sources

PubMed2006

A method for the estimation of femoral bone mineral density from variables of ultrasound transmission through the human femur.

Quantitative ultrasound (QUS) measurements at peripheral sites can be used to estimate osteoporotic fracture risk. However, measurements at these sites are less suitable to predict bone mineral density (BMD) or fracture risk at the central skeleton. We investigated whether direct QUS measurements at the femur would allow to estimate dual X-ray absorptiometry (DXA) BMD of the total proximal femur with errors comparable to established DXA accuracy errors. Two independent sets of femora were measured in Kiel (6 f, 4 m, age: 55-90) and Paris (19 f, 20 m age: 45-95) using different benchtop systems in the two laboratories. The femora were scanned in transverse transmission mode using focused US transducers of 500 kHz center frequency. The QUS values were averaged over a region similar to the total hip region of dual X-ray absorptiometry (DXA) measurements. BMD was measured using DXA. SOS and BMD correlated significantly (p<0.0001) in both data sets (R2=0.81-0.93). Correlations between BUA and BMD were also significant at p<0.001, but correlation coefficients were lower (R2=0.61-0.75). Residual errors for the estimation of BMD were 8%-10% for SOS as predictor, and 14%-16% for BUA as predictor. The residual error of 8 to 10% for the estimation of BMD from SOS is comparable to variabilities among different DXA femur subregions and accuracy errors of femoral DXA measurements caused by the impact of soft tissue. It is substantially smaller than the errors of 13% for the estimation of total femur BMD from spine BMD, 14% for the estimation of total femur BMD from calcaneus SOS or 16% for the estimation of ash weight from DXA. The results of the study show that SOS is able to predict total BMD with adequate accuracy. If femoral BMD could be obtained in vivo with comparable accuracy, femoral QUS would be suited for the assessment of bone status at one of the main osteoporotic fracture sites.

Absorptiometry, Photon↗

PubMed2006

Quality and performance measures in bone densitometry: part 1: errors and diagnosis.

INTRODUCTION: Bone densitometry is one of the main pillars in the assessment of osteoporosis. The most important modalities are dual x-ray absorptiometry (DXA), quantitative computed tomography (QCT), and quantitative ultrasound (QUS). MATERIALS AND METHODS: For each modality a variety of technical solutions and numerous commercial devices are available and widely used for patient measurements. While the field of bone densitometry may be considered mature, new modalities and devices are being introduced. Consequently, there is a constant need to assess and compare the quality of bone densitometry approaches and devices in a rigorous way. RESULTS: The International Commission on Radiation Units has commissioned a report on bone densitometry to address some of these issues, in particular to provide clear definitions of quantities and units used and to describe parameters and methods that can be used to compare and standardize densitometric equipment and measurements. One of the core chapters of the report summarizes quality and performance measures in bone densitometry. It is divided into four sections: physical performance measures, diagnosis, fracture risk, and monitoring. Here we publish part 1 of this chapter containing the first two sections: physical performance measures and issues in diagnosing osteoporosis. CONCLUSION: Following the international standard (ISO 5725-1), trueness, bias, repeatability, and reproducibility are defined along with terms common to osteoporosis research, such as accuracy and precision. Building on the conceptual definition of osteoporosis, diagnostic criteria are defined and discussed including criteria for reference data. Based on this, clinical performance measures commonly used for the diagnosis of osteoporosis are reviewed and discussed.

Absorptiometry, Photon↗

PubMed2006

[Quantitative ultrasound].

Methods of quantitative ultrasound (QUS) can be used to obtain knowledge about bone fragility. Comprehensive study results exist showing the power of QUS for the estimation of osteoporotic fracture risk. Nevertheless, the variety of technologies, devices, and variables as well as different degrees of validation of the single devices have to be taken into account. Using methods to simulate ultrasound propagation, the complex interaction between ultrasound and bone could be understood and the propagation could be visualized. Preceding widespread clinical use, it has to be clarified if patients with low QUS values will profit from therapy, as it has been shown for DXA. Moreover, the introduction of quality assurance measures is essential. The user should know the limitations of the methods and be able to interpret the results correctly. Applied in an adequate manner QUS methods could then, due to lower costs and absence of ionizing radiation, become important players in osteoporosis management.

Fractures, Spontaneous↗

PubMed2006

[Parametric biomedical imaging--what defines the quality of quantitative radiological approaches?].

Quantitative parametric imaging approaches provide new perspectives for radiological imaging. These include quantitative 2D, 3D, and 4D visualization options along with the parametric depiction of biological tissue properties and tissue function. This allows the interpretation of radiological data from a biochemical, biomechanical, or physiological perspective. Quantification permits the detection of small changes that are not yet visually apparent, thus allowing application in early disease diagnosis and monitoring therapy with enhanced sensitivity. This review outlines the potential of quantitative parametric imaging methods and demonstrates this on the basis of a few exemplary applications. One field of particular interest, the use of these methods for investigational new drug application studies, is presented. Assessment criteria for judging the quality of quantitative imaging approaches are discussed in the context of the potential and the limitations of these methods. While quantitative parametric imaging methods do not replace but rather supplement established visual interpretation methods in radiology, they do open up new perspectives for diagnosis and prognosis and in particular for monitoring disease progression and therapy.

Algorithms↗

PubMed2005

Optimal prediction of bone mineral density with ultrasonic measurements in excised human femur.

Bone mineral density (BMD) measured with dual energy X-ray absorptiometry (DXA) techniques is the current gold standard for osteoporotic fracture risk prediction. Quantitative ultrasound (QUS) techniques in transmission measurements are, however, increasingly recognized as an alternative approach. It is feasible to select different QUS methods, one type being optimized to assess microarchitectural properties of bone structure and another to assess BMD. Broadband ultrasonic attenuation (BUA) and ultrasonic velocity (UV) measured on the proximal human femur have been shown to be both significantly correlated with BMD. However, a great diversity of algorithms has been reported to measure the time-of-flight used to derive UV values. The purpose of this study was to determine which procedure results in the optimal BMD prediction at the proximal femur from ultrasound measurements. Thirty-eight excised human femurs were measured in transmission with a pair of focused 0.5-MHz central frequency transducers. Two-dimensional scans were performed and radiofrequency (RF) signals were recorded digitally at each scan position. BUA was estimated and eight different signal processing techniques were performed to estimate UV. For each signal-processing technique UV was compared to BMD. We show that the best prediction of BMD was obtained with signal-processing techniques taking into account only the first part of the transmitted signal (r2BMD-SOS = 0.86). Moreover, we show that a linear multiple regression using both BUA and speed of sound (SOS) and applied to site-matched regions of interest improved the accuracy of BMD predictions (r2BMD-SOS/BUA = 0.95). Our results demonstrate that selecting specific signal-processing methods for QUS variables allows optimal assessment of BMD. Correlation is sufficiently high that this specific QUS method can be considered as a good surrogate of BMD.

Absorptiometry, Photon↗

PubMed2005

In vitro speed of sound measurement at intact human femur specimens.

Quantitative ultrasound has been recognized as a useful tool for fracture risk prediction. Current measurement techniques are limited to peripheral skeletal sites. Our objective was to demonstrate the in vitro feasibility of ultrasonic velocity measurements on human proximal femur and to investigate the relationship between velocity and bone mineral density (BMD). Sound velocity images were computed from 2-D scans performed on 38 excised human femurs in transmission at 0.5 MHz. Different regions-of-interest were investigated. Dual x-ray absorptiometry scans have been achieved for BMD measurements in site-matched regions. Our study demonstrates the feasibility of ultrasonic velocity measurements at the hip with reasonable precision (coefficient of variation of 0.3%). The best prediction of BMD was reached in the intertrochanter region (r(2) = 0.91, p < 10(-4)), with a residual error of 0.06 g/cm(2) (10%). Because BMD measured at the femur is the best predictor of hip fracture risk, the highly significant correlation and small residual error found in this study suggest that speed of sound measurement at the femur might be a good candidate for hip fracture risk prediction.

Absorptiometry, Photon↗

PubMed2004

[Quantitative ultrasound for the diagnosis of osteoporosis].

Quantitative ultrasound (QUS) methods are promising tools for the assessment of the bone status in osteoporosis. The techniques are based on changes in speed and amplitude of a broadband ultrasound signal propagating through the bone. However, ultrasound propagation through the anisotropic bone is complex and cannot be described in a simple way. The devices are easy to use, inexpensive, portable, do not use ionizing radiation, and therefore have advantages compared to conventional densitometry. This review discusses the technical basics, current research, clinical applications, points of weakness, and future prospects of QUS. For better understanding ultrasound propagation through bone is visualized with a simulation software.

Bone and Bones↗

PubMed2002

Detection of changes in cartilage water content using MRI T2-mapping in vivo.

OBJECTIVES: Osteoarthritis (OA) is the most prevalent chronic disease in the elderly, and it is generally diagnosed at an advanced state when treatment is difficult if not impossible. The early form of OA is characterized by an elevated water content in the cartilage tissue. The purpose of this study was to verify in vivo if changes in the water content of patellar cartilage typically occurring in early OA can be detected using T(2) mapping MRI methods. DESIGN: Twenty healthy volunteers performed 60 knee bends in order to compress their patellar cartilage thereby reducing its water content. MR images of the patellar cartilage were acquired immediately following exercise and after 45 min of rest. Patellar cartilage thickness and T(2) maps were determined and their difference between the time points evaluated. RESULTS: Cartilage thickness increased by 5.4+/-1.5% from 2.94+/-0.15 mm to 3.10+/-0.15 mm (P< 0.001) following 45 min of rest, while T(2) increased by 2.6+/-1.0% from 23.1+/-0.5 ms to 23.7+/-0.6 ms (P< 0.05). CONCLUSION: Small, physiologic changes in the water content of patellar cartilage and the concomitant change in proteoglycan and collagen density following exercise can be detected using MRI. The proposed T(2)-mapping method, together with other non-invasive MR cartilage imaging techniques, could aid in the early diagnosis of OA.

Adult↗