Biomedical subjects

B Kempers

Publications and source records attributed to B Kempers.

4 recordsLinked to original sources

PubMed1993

Phantom studies in osteoporosis.

Differences in measurement results of bone densitometry are an obvious disadvantage of this method. The differences are mainly due to the calibration procedures for bone densitometry systems employed by the manufacturers, the software algorithms for defining the region of interest or edge detection, and the physiological inhomogeneity of body composition. Whereas intra-unit variation of reproducibility is acceptable, inter-unit variation may reach up to 20%. This paper discusses the problems of designing measurement phantoms and underlines the need for standardisation of phantoms for calibration, cross-calibration, and quality control in bone densitometry. A general phantom used for cross-calibration should handle all parameters influencing measurement of bone minerals to yielded dynamic reference values. One has to note that densitometry systems do not measure the absolute bone mineral content but a model-related equivalent of the calibration material.

Absorptiometry, Photon↗

PubMed1990

[Comparative measurements of bone mineral content using DPA and DPX--initial clinical experiences].

A technically satisfactory method with adequate precision and reproducibility is necessary for accurate determination of bone mineral content. To the previously described techniques (SPA, DPA, QCT and SQCT) a new method has been added based on the absorption of a filtered x-ray beam (DPX). Comparison of DPA/DPX measurements of the mineral contents of vertebrae and femora in 126 patients showed a high correlation between the results (r = 0.97 for vertebrae and 0.93 for femoral necks). Ten measurements of a vertebral phantom and ten measurements of a normal male showed significantly higher accuracy of the DPX method. Other advantages of the DPX method are increased speed of the procedure by a factor 3-5, lower radiation dose and better spatial resolution. Measurements of the upper and lower extremities are possible in addition to whole body scans. In summary, the DPX technique is a significant improvement on the conventional DPA method, whereas the data obtained from DPA measurements remain valid.

Absorptiometry, Photon↗

PubMed1988

[Nuclear medicine methods for the determination of bone mineral content].

Osteoporosis is becoming recognized as a major social and economical health problem. Bone mineral content (BMC) depends on many hormonal and metabolic factors. The pathophysiological mechanism of the loss of bone mass is still unclear. For preventive diagnosis and treatment of osteoporosis, quantitative technology is required that will measure BMC with high precision and reproducibility. Nuclear medical methods permit the BMC of the appendicular skeleton to be measured by single photon absorptiometry. Whole-body BMC, as well as spine and femur BMC, can be measured by dual photon absorptiometry. The results from both procedures are reasonably precise and correlate well with the ash weight of isolated bone. The radiation exposure level in both SPA and DPA is low. SPA and DPA may be used for cost-effective screening of high-risk patients to predict the likelihood of future fractures and control osteoporosis therapy.

Bone and Bones↗

PubMed1986

[Distribution of textile fibers in the path of a bullet].

Twenty-one blocks consisting of 20% gelatin were fired at using firearms of the long rifle caliber .22 and .357 Magnum. The frontal area of these blocks was prepared with textile coverings marked with technetium 99m. Two gunshot series of each type were fired at summer, interseasonal, and winter clothing, using different ammunition. The radioactivity of the bombarded blocks was measured by single photon emission computed tomography (SPECT). The results of these gun shot series were presented graphically and compared. Initially (at 2 cm depth), high radioactivity is always detected, which among other things is caused by the defilement of the bullet's surface when shot through the textile covering marked by technetium. The higher radioactivity in the middle and deeper block areas is the result of fiber infiltration. Accordingly, there are greater fiber accumulations in the middle and deeper areas of the path of the bullet. This is the case mainly in thinner clothing (summer). Heavier clothing (autumn, winter) presents a greater obstacle for bullets with greater impact as well. Here, only projectiles having a lesser tendency to deform, as well as a high impact, transport a considerable proportion of textile fibers into the deeper parts of the blocks.

Clothing↗