Accumulation of bone strontium measured by in vivo XRF in rats supplemented with strontium citrate and strontium ranelate.

Strontium ranelate is an approved pharmacotherapy for osteoporosis in Europe and Australia, but not in Canada or the United States. Strontium citrate, an alternative strontium salt, however, is available for purchase over-the-counter as a nutritional supplement. The effects of strontium citrate on bone are largely unknown. The study's objectives were 1) to quantify bone strontium accumulation in female Sprague Dawley rats administered strontium citrate (N=7) and compare these levels to rats administered strontium ranelate (N=6) and vehicle (N=6) over 8 weeks, and 2) to verify an in vivo X-ray fluorescence spectroscopy (XRF) system for measurement of bone strontium in the rat. Daily doses of strontium citrate and strontium ranelate were determined with the intention to achieve equivalent amounts of elemental strontium. However, post-hoc analyses of each strontium compound conducted using energy dispersive spectrometry microanalysis revealed a higher elemental strontium concentration in strontium citrate than strontium ranelate. Bone strontium levels were measured at baseline and 8 weeks follow-up using a unique in vivo XRF technique previously used in humans. XRF measurements were validated against ex vivo measurements of bone strontium using inductively coupled plasma mass spectrometry. Weight gain in rats in all three groups was equivalent over the study duration. A two-way ANOVA was conducted to compare bone strontium levels amongst the three groups. Bone strontium levels in rats administered strontium citrate were significantly greater (p<0.05) than rats administered strontium ranelate and vehicle. ANCOVA analyses were performed with Sr dose as a covariate to account for differences in strontium dosing. The ANCOVA revealed differences in bone strontium levels between the strontium groups were not significant, but that bone strontium levels were still very significantly greater than vehicle.

Is Thyroid Screening Necessary for Nuclear Medicine Personnel Receiving and Administering Capsules Containing Large Doses of 131I?

The cost-effectiveness of a thyroid screening procedure for the detection of internal contamination of personnel working with large doses of encapsulated iodine-131 (131I) was examined by reviewing the results of screening measurements performed during 1 year. Thyroid burdens were measured by self-assessment using a sodium iodide (NaI) probe. Of 113 screening measurements, 101 indicated a negative thyroid content of 131I. The largest burden observed was statistically not different from zero. The count rate corresponding to the largest observed burden would represent an 131I content of 23 Bq, which is approximately 0.2% of the level at which results have to be reported to the Canadian Nuclear Safety Commission. Negative count rates arose because of a small overestimation of the background contribution that was measured with a neck phantom positioned in front of the thyroid probe. The cost of a thyroid screening program for personnel who handle encapsulated 131I is considerable, especially when the need for such measurements is questionable.

Radiation exposure for 'caregivers' during high-dose outpatient radioiodine therapy.

On 27 occasions, radiation doses were measured for a family member designated as the 'caregiver' for a patient receiving high-dose radioiodine outpatient therapy for differentiated thyroid carcinoma. For 25 of the administrations, patients received 3.7 GBq of (131)I. Radiation doses for the designated caregivers were monitored on an hourly basis for 1 week using electronic personal dosemeters. The average penetrating dose was 98 +/- 64 microSv. The maximum penetrating dose was 283 microSv. Measured dose rate profiles showed that, on average, one-third of the caregiver dose was received during the journey home from hospital. The mean dose rate profile showed rapid clearance of (131)I with three distinct phases. The corresponding clearance half-times were <1 h, 21 h and approximately 8 d. These components were associated, respectively, with the drive home, the clearance of radioiodine from an athyreotic patient and small quantities of (131)I contaminating the home.