Estimating mean glandular dose using proprietary mammography phantoms.

Screening mammography programs prescribe limits on the radiation dose to the glandular tissue of a compressed breast--the Mean Glandular Dose (MGD)--which may vary between 2 and 3 mGy for a 50% adipose and 50% glandular tissue compressed breast of 4.2 to 5.0 cm thickness. Commercially available breast phantoms offer a choice of equivalent tissue thicknesses and composition ranging typically from 30% adipose and 70% glandular tissue to 50% adipose and 50% glandular tissue. A number of these phantom were compared under clinical conditions and the MGD calculated for each using the factors developed by Wu et al. [Wu, X., Barnes, G.T. and Tucker, D.M. (1991) Spectral dependence of glandular tissue dose in screen film mammography, Radiology 179, 143-148].

A compliance testing program for diagnostic X-ray equipment.

Compliance testing is nominally that part of a quality assurance program dealing with those aspects of X-ray equipment performance that are subject to radiation control legislation. Quality assurance programs for medical X-ray equipment should be an integral part of the quality culture in health care. However while major hospitals and individual medical centers may implement such programs with some diligence, much X-ray equipment can remain unappraised unless there is a comprehensive regulatory inspection program or some form of compulsion on the equipment owner to implement a testing program. Since the late 1950s all X-ray equipment in the State of Western Australia has been inspected by authorized officers acting on behalf of the Radiological Council, the regulatory authority responsible for administration of the State's Radiation Safety Act. However, economic constraints, coupled with increasing X-ray equipment numbers and a geographically large State have significantly affected the inspection rate. Data available from inspections demonstrate that regular compliance and performance checks are essential in order to ensure proper performance and to minimize unnecessary patient and operator dose. To ensure that diagnostic X-ray equipment complies with accepted standards and performance criteria, the regulatory authority introduced a compulsory compliance testing program for all medical, dental and chiropractic diagnostic X-ray equipment effective from 1 January 1997.

Near-surface disposal of concentrated NORM wastes.

Naturally occurring radioactive material (NORM) in concentrated forms arises in nature and in industry where natural radioisotopes become mobile and then accumulate at particular sites. In industry this often occurs in an acidic environment, where precipitates containing radionuclides plate out onto pipe walls, filters, tank linings, etc. As the radionuclides are selectively deposited, they build up and there is a multiplying effect in terms of the radioactivity concentration. Conditions often tend to favour the build-up of radium, particularly when barium is present and can cause the co-precipitation of radium compounds. As radium is highly radiotoxic, the handling and disposal of such material requires careful management. The state of Western Australia currently has the only low level waste repository in Australia, located at Mt Walton East. To date this repository has been used predominantly to dispose of packaged radioactive waste containing artificial radioisotopes, but there is an increasing demand for the repository to accept bulk concentrated NORM wastes from mining and related industries. Already steelwork from a dismantled phosphoric acid plant and other items contaminated with NORM have been disposed of. The Mt Walton East repository is now proposed as the disposal site for 6000 tonnes per annum of gangue residue from the processing of monazite. The residue contains thorium and a small amount of radium. This paper looks at the technical and related considerations of these disposal operations.

The sonographically patent umbilical vein in portal hypertension.

A patent umbilical vein is a sonographic sign of portal hypertension. The specificity of the sign is not known. In a review of 12 patients with sonographically demonstrated patency of the umbilical vein, we found two patients in whom no clinical evidence existed to suggest the presence of portal hypertension. In six of 10 healthy subjects, the lumen of the proximal umbilical vein measured up to 3 mm in diameter. A review of the literature indicates that in normal injection-corrosion studies, a tiny vessel can be seen in noncirrhotic livers. A patient umbilical vein greater than 3 mm must be demonstrated, at least throughout the course of the intrahepatic portion of the ligamentum teres, to confirm portal hypertension.