Bremsstrahlung radiation exposure from pure beta-ray emitters.

UNLABELLED: With increasing therapeutic use of radionuclides that emit relatively high-energy (>1 MeV) beta-rays and the production in vivo of bremsstrahlung sufficient for external imaging, the potential external radiation hazard warrants evaluation. METHODS: The exposure from a patient administered beta-ray-emitting radionuclides has been calculated by extending the National Council on Radiation Protection and Measurement model of a point source in air to account for biologic elimination of activity, the probability of bremsstrahlung production in vivo and its mean energy and the absorption by the patient's body of the bremsstrahlung thus produced. To facilitate such calculations, a quantity called the "specific bremsstrahlung constant" (in C/kg-cm2/MBq-h), betaBr, was devised and calculated for several radionuclides. The specific bremsstrahlung constant is the bremsstrahlung exposure rate (in C/kg/h) in air at 1 cm from a 1 MBq beta-ray emitter of a specified maximum beta-ray energy and frequency of emission in a medium of a specified effective atomic number. RESULTS: For pure beta-ray emitters, the retained activities at which patients can be released from medical confinement (i.e., below which the effective dose equivalent at 1 m will not exceed the maximum recommended value of 0.5 cSv for infrequently exposed members of the general public) are extremely large: on the order of hundreds of thousands to millions of megabecquerels. CONCLUSION: Radionuclide therapy with pure beta-ray emitters, even high-energy beta-ray emitters emitted in bone, does not require medical confinement of patients for radiation protection.

Scintigraphic criteria for the diagnosis of renal arteriovenous fistulas.

Visualization of the inferior vena cava (IVC) on renal perfusion imaging occurs in cases of renal arteriovenous (AV) fistulas. A review of consecutive renal scans demonstrated IVC visualization in three of 217 patients without AV fistulas. IVC visualization occurred 3-6 seconds after peak aortic activity in normal patients. With renal AV fistulas, an intrarenal focus of increased activity is seen and IVC visualization occurs coincident with peak aortic activity.

Assessment of bone grafts used for acetabular augmentation in total hip arthroplasty. A study using roentgenograms and bone scintigraphy.

Total hip arthroplasty was performed in 13 hips with acetabular bone grafts for secure component fixation. The incorporation and healing of acetabular bone grafts were investigated with the aid of roentgenograms, planar bone scans, and a newer scintigraphic technique, three-dimensional single photon emission computed tomography (SPECT). Conventional roentgenograms proved unreliable in evaluating bone graft reconstitution because of overlapping trabecular bone patterns of the graft and iliac wing. There was no evidence of graft failure or acetabular loosening. Bone grafts in the late follow-up group (four to seven years postoperation) exhibited normal radionuclide activity, whereas grafts less than one year postsurgery demonstrated patterns of increased activity. SPECT was helpful in producing an anatomic reconstruction of the acetabulum. The observation that bone grafts exhibited normal biological viability is crucial for ensuring secure acetabular component fixation on a long-term basis.