Control of low-level radiation exposure: time for a change?

The carcinogenic risks of exposure to low-level ionising radiation used by the ICRP have been challenged as being, at the same time, both too high and too low. This paper explains that the epidemiological evidence will always be limited at low doses, so that understanding the cellular mechanisms of carcinogenesis is increasingly important to assess the biological risks. An analysis is then given of the reasons why the challenges to the ICRP, especially about the linear non-threshold response model, have arisen. As a result of considering the issues, the Main Commission of the ICRP is now proposing a revised, simpler, approach based on the concept of what is being called 'controllable dose'. This is an individual-based philosophy and represents a shift in emphasis by the Commission from societal-oriented criteria using Collective Dose. Finally the paper speculates on the consequences for radiological protection of such a change in policy. The Commission wishes its ideas to be discussed as part of its reconsideration of its recommendations.     

Choice of phantom material and test protocols to determine radiation exposure rates for fluoroscopy.

The image intensifier entrance exposure rate (IIEER)) and entrance skin exposure rate (ESER) are two characteristics that can be used to determine whether a fluoroscope is adjusted to operate at an optimal dose rate level. This article presents solutions to some of the practical problems that are encountered when measuring these parameters. Because the energy response of the ion chamber used to measure exposure rates is different from that of the image intensifier, a fluoroscope with a perfect automatic exposure rate control will have an IIEER that depends on the phantom composition, phantom thickness, and x-ray tube potential. The authors developed a simple mathematic model to investigate the relationship of ion chamber response to image intensifier response and to determine the effects of phantom composition and thickness. Results from this model were compared with measurements made with two C-arm fluoroscopes. Variations of 40% or more in the IIEER and ESER can be ascribed to these phenomena.     

Public Health and Policy Issues of Hernia Surgery in Africa

Inguinal hernia repair has been overlooked as a public health priority in Africa, with its high prevalence largely unrecognized, and traditional public health viewpoints assuming that not enough infrastructure, human resources, or financing capacity are available for effective service provision. Emerging evidence suggests that inguinal hernias in Ghana are approximately ten times as prevalent as in high-income countries, are much more long-standing and severe, and can be repaired with low-cost techniques using mosquito net mesh through international collaboration. Outcomes from surgery are comparable to published literature, and potential exists for scaling up capacity. Special attention must be paid to creating financing systems that encourage eventual local self-sustainability. Andrew Kingsnorth, Michael Clarke, and Samuel Shillcutt conceived the idea. SS led the paper drafting, with contributions and editing from AK and MC. An erratum to this article can be found at     

A double-blind crossover study of oral xamoterol in postural hypotension due to diabetic autonomic neuropathy

Recent reports have suggested that xamoterol, a beta₁ adrenoceptor partial agonist with 43% intrinsic sympathomimetic activity improves symptomatic postural hypotension in patients with primary autonomic failure. To evaluate the use of xamoterol in eleven insulin dependent patients with diabetes mellitus who had postural hypotension (over 20 mmHg systolic blood pressure) secondary to autonomic neuropathy, we performed a double-blind, randomized, placebo controlled crossover study with xamoterol (200 mg bd orally) for 1 month. Treatment with xamoterol raised supine systolic blood pressure by 11 mmHg but a reduced standing systolic blood pressure by 11 mmHg with an increase in the standing-supine systolic blood pressure difference. No significant differences were observed in symptom score, HbA₁ or plasma glucose. We conclude that oral xamoterol raises supine systolic blood pressure but paradoxically lowers standing systolic blood pressure further in insulin dependent diabetes mellitus, Xamoterol is unlikely to be of value in the management of postural hypotension in diabetic patients with autonomic neuropathy.     

Femoral capital osteonecrosis: MR finding of diffuse marrow abnormalities without focal lesions

Six painful hips in five patients were examined with magnetic resonance (MR) imaging and were found to have diffuse signal abnormalities in the marrow of the femoral head and neck, which extended into the intertrochanteric area in five cases. The abnormal regions were low in signal intensity on images obtained with a short repetition time (TR) and a short echo time (TE) and were isointense or hyperintense on long TR/TE images--findings that have been attributed by others to bone marrow edema. Edema was also seen in marrow just above the acetabulum in two cases. No focal abnormalities characteristic of osteonecrosis were seen. Osteonecrosis was subsequently shown to be present in all six femoral heads at core biopsy (three cases) or by subsequent development of focal MR abnormalities reported to be highly specific for osteonecrosis (three cases). The affected hips had been radiographically normal or subtly osteopenic and had shown intense radionuclide uptake in the femoral head at scintigraphy, with lesser abnormality in the neck and intertrochanteric region. Follow-up MR examinations of five of the six femoral heads showed the diffuse abnormalities to have been transient. Although diffuse MR abnormalities in the proximal femur are not specific, they may indicate the presence of osteonecrosis of the femoral head.