Effective dose to the patient undergoing superior vena cava stent.

Metallic stents have been recently introduced for treating superior vena cava (SVC) obstruction. Dose data, in terms of dose-area product (DAP), from 44 patients referred for SVC stent placement on a digital unit have been retrospectively analysed in terms of their fluoroscopic and radiographic components. The mean DAP for the 44 examinations was 42 Gy cm2 and the effective dose was estimated to be 5.8 mSv. The fluoroscopic component was approximately 80%, with a mean screening time for these examinations of 17 min. The mean number of digital exposures was 86.

Radiation dose and in vitro precision in paediatric bone mineral density measurement using dual X-ray absorptiometry.

Dual X-ray absorptiometry (DXA) is one of the most widely used techniques for non-invasive assessment of bone integrity. There is a growing demand for measurement of paediatric bone status. In DXA the principal radiation risks to patients are the carcinogenic and genetic effects. Radiation dosimetry is well established for DXA in adults, but there are limited paediatric data available. We report on a study to estimate the effective doses (EDs) received by typical 5- and 10-year-old children using the paediatric scan mode on the Lunar DPX-L bone mineral density scanner. Entrance surface doses (ESDs) and percentage depth doses for the total body and PA spine scan modes were measured using lithium borate thermoluminescent dosemeters (TLDs) located at the surface and distributed at various organ locations in anthropomorphic child phantoms. The EDs were calculated from the percentage depth doses, amount of each organ irradiated and tissue weighting factors. The ESDs were measured to be 6.0 and 0.12 microGy for the posteroanterior (PA) spine and total body, respectively. PA spine EDs were calculated as 0.28 and 0.20 microSv for the 5- and 10-year-old, respectively. Total body EDs were 0.03 and 0.02 microSv for the 5- and 10-year-old children, respectively. These results compare with an adult ED of 0.21 microSv for the PA spine. They are also more than two orders of magnitude lower than reported ESDs and EDs for paediatric chest X-rays. Bone mineral density (BMD) short-term in vitro precision was 0.5% and 1% in the 5- and 10-year-old phantoms, respectively. In conclusion, the Lunar DPX-L in the paediatric mode has a high precision and very low radiation doses, similar to those reported for the adult mode.

The development of a technique to measure bone aluminium content using neutron activation analysis.

The accumulation and toxicity of aluminium in patients with chronic renal failure is a well recognized hazard, and there is a need for a non-invasive technique to assess Al tissue load in these patients. The technique of in vivo neutron activation analysis, using a thermal neutron beam from a reactor, has been employed by previous workers, who measured Al in the hand with a detection limit of 0.4 mg for a dose equivalent of 20 mSv. However, the application of this technique is restricted by the very limited availability of nuclear reactors. We report the modification of an existing 252Cf-based instrument and construction of a shielded, high-efficiency counting system for the in vivo measurement of Al in the hand. Phantoms containing tissue-equivalent solutions of Ca, P, Na and Cl with various Al loadings were used for validation of the technique. The Al/Ca ratio in the hands of seven patients with renal failure was measured using a cyclic activation technique to compensate for the relatively low neutron output of the 252Cf source, and a detection limit of approximately 2.2 mg Al was achieved for a dose equivalent of 36 mSv. The results were compared with the Al content of iliac crest bone biopsy specimens measured using electrothermal atomic absorption spectrophotometry.