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Biomedical subjects

C F Njeh

Publications and source records attributed to C F Njeh.

40 records · Page 3Linked to original sources
PubMed1996

The non-linear relationship between BUA and porosity in cancellous bone.

There is growing interest in assessing the clinical value of ultrasound in the prediction and management of osteoporosis. However, the mechanism of ultrasound propagation in cancellous bone is not well understood. The Biot theory is one approach to modelling the interaction of sound waves with cancellous structure, and porosity is one of its input parameters. In this paper we report the relationship between broadband ultrasonic attenuation (BUA) corrected for specimen thickness (nBUA) and porosity in a porous Perspex cancellous bone mimic, a stereolithography cancellous bone mimic and in natural human and bovine tissue. nBUA and porosity have a non-linear parabolic relationship. The maximum nBUA value (nBUAmax) occurs at approximately 30% porosity in the Perspex mimic, approximately 70% in the stereolithography mimic and approximately 75% in natural cancellous bone. We discuss the effect of structure on the form of the nBUA-porosity relationship.

Animals↗
PubMed1996

Radiological assessment of a new bone densitometer--the Lunar EXPERT.

Dual energy X-ray absorptiometry (DXA) is one of the most widely used techniques in the management of osteoporosis and other skeletal diseases. Although patient doses from DXA are generally low, it is still necessary to measure them to assess the risk of radiation injury. We report on a study to estimate the effective dose (ED) to patients and staff from a new DXA scanner--the Lunar EXPERT, and make a comparison with a similar study carried out on a Lunar DPX-L. The entrance surface doses were measured to be 895 microGy and 10.25 microGy for the EXPERT and DPX-L, respectively. The EXPERT maximum EDs were calculated to be 74.7 microSv and 44.9 microSv for the anteroposterior (AP) lumbar spine and the proximal femur, respectively. More than 50% reduction in ED could be achieved by using a smaller scanning width. The maximum EDs for the DPX-L were calculated to be 0.21 microSv and 0.15 microSv for the AP lumbar spine and the proximal femur, respectively. The scattered dose rates (ambient dose equivalent) were measured to be less than 2 and less than 1 microSv h-1 at 50 cm and 100 cm, respectively, for the DPX-L, and the equivalent values for the EXPERT were 240 and 64 microSv h-1. Although both the patient dose and scattered dose rates are quite low relative to other radiological examinations, good practice aimed at dose reduction should still be implemented. Whilst protection for the operator is not needed for the DPX-L system, it may be (depending on the size of the room) for the EXPERT system.

Absorptiometry, Photon↗
PubMedDate not supplied

Variation in bone mineral density between different anatomical sites in a normal local population.

Bone mineral density (BMD) measured using dual energy X-ray absorptiometry (DXA) can be expressed in terms of standard deviations, above or below mean young adult T-scores and above or below age-matched Z-scores. The differences between the left neck of the femur (LN), right neck of the femur (RN) and lumbar spine (L2-L4) were statistically significant, irrespective of whether expressed as T-scores or Z-scores. Therefore skeletal status assessment should involve as many sites as practically possible. Considering the low radiation dose and short scanning time, it is suggested that at least the two femurs and lumbar spine BMD be used in routine osteoporosis risk assessment.

Absorptiometry, Photon↗