In vivo study of an X-ray fluorescence system to detect bone strontium non-invasively

Medical Physics and Applied Radiation Science, McMaster University, Hamilton, L8S 4K1, Canada.
Physics in Medicine and Biology (Impact Factor: 2.76). 04/2007; 52(8):2107-22. DOI: 10.1088/0031-9155/52/8/005
Source: PubMed


An x-ray fluorescence (XRF) system using 125I as the source was developed to measure strontium in bone in vivo. As part of an in vivo pilot study, 22 people were measured at two bone sites, namely the index finger and the tibial ankle joint. Ultrasound measurements were used to obtain the soft tissue thickness at each site, which was necessary to correct the signal for tissue attenuation. For all 22 people, the strontium peak was clearly distinguishable from the background, proving that the system is able to measure Sr in vivo in people having normal bone Sr levels. Monte Carlo simulations were carried out to test the feasibility and the limitations of using the coherently scattered peak at 35.5 keV as a means to normalize the signal to correct for the bone size and shape. These showed that the accuracy of the normalized Sr signal when comparing different people is about 12%. An interesting result arising from the study is that, in the measured population, significantly higher measurements of bone Sr concentration were observed in continental Asian people, suggesting the possibility of a dietary or race dependence of the bone Sr concentration or a different bone biology between races.

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Available from: David Robert Chettle, Jul 08, 2014
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    • "The IVXRF system has been shown to be sensitive and capable of measuring bone Sr levels, non-invasively, with neglible radiation risk. Further information on this IVXRF system and its comparison to other methods of determining bone Sr content is available in the literature [16] [17] [18]. "
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    ABSTRACT: Ten female volunteers were recruited as part of the Ryerson and McMaster University Strontium (Sr) in Bone Research Study to have their bone Sr levels measured as they self-supplemented with Sr supplements of their choice. Of the ten volunteers, nine were suffering from osteopenia and/or osteoporosis. Non-invasive bone Sr measurements were performed using an in vivo x-ray fluorescence (IVXRF) I-125 based system. Thirty minute measurements were taken at the finger and ankle, representing primarily cortical and trabecular bone, respectively. For analysis, the 14.2keV Sr K-alpha peak normalized to the Coherent peak at 35.5keV was used. Baseline readings, representing natural bone Sr levels were acquired since all volunteers had no previous intake of Sr based supplements or medications. Once Sr supplements were started, a 24hr reading was taken, followed by frequent measurements ranging from weekly, biweekly to monthly. The longest volunteer participation was 1535 days. The mean baseline Sr signal observed for the group was 0.42±0.13 and 0.39±0.07 for the finger and ankle, respectively. After 24hrs, the mean Sr signal rose to 1.43±1.12 and 1.17±0.51, for the finger and ankle, respectively, representing a statistically significant increase (p=0.0043 & p=0.000613). Bone Sr levels continued to increase throughout the length of the study. However the Sr signal varied widely between the individuals such that after three years, the highest Sr signal observed was 28.15±0.86 for the finger and 26.47±1.22 for the ankle in one volunteer compared to 3.15±0.15 and 4.46±0.36, for the finger and ankle, respectively in another. Furthermore, while it was previously reported by our group, that finger bone Sr levels may plateau within two years, these results suggest otherwise, indicating that bone Sr levels will continue to rise at both bone sites even after 4 years of Sr intake.
    Full-text · Article · Jan 2014 · Bone
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    • "Detection of the number of strontium X-rays emitted from a defined bone volume is directly dependent upon bone strontium. To date, bone strontium levels have been assessed in humans using this technique [35] [36] [37] [38], but not in animals. "
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    ABSTRACT: 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 8weeks, 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 8weeks 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.
    Full-text · Article · Sep 2012 · Bone
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    • "The baseline values we observed for this volunteer are in agreement with the baseline values found among the Caucasian individuals among the twenty-two healthy volunteers, measured in a previous 2006 study [11]. The average normalized K-alpha baseline values for the Caucasian individuals were reported to be 0.43 ± 0.08 and 0.40 ± 0.13 for the finger and ankle, respectively. "
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    ABSTRACT: A previously developed in vivo X-ray fluorescence (IVXRF) I-125 based system was used to measure bone strontium levels non-invasively in an osteoporotic female volunteer. The volunteer was recruited in December 2008, as part of the Ryerson and McMaster University Strontium in Bone Research Study and measured at twice weekly, weekly and monthly intervals. Thirty minute measurements were taken at the finger and ankle bone sites, representing primarily cortical and trabecular bone, respectively and the strontium K-alpha X-ray peak at 14.16 keV was used in the analysis. Since the volunteer had no prior history of strontium based medications or supplementation, baseline natural strontium levels were obtained followed by a 24h measurement of first intake of strontium citrate supplements (680 mg Sr/day). While the baseline levels of 0.38 ± 0.05 and 0.39 ± 0.10 for the finger and ankle, respectively, were on par with those previously reported in Caucasians among twenty-two healthy non-supplementing strontium individuals by our group, an increase began to be seen after 24 hrs of 0.62 ± 0.14 and 0.45 ± 0.12 for the finger and ankle, respectively. By 120 h, the increase was statistically significant at 0.68 ± 0.07 and 0.93 ± 0.05, respectively. Further increases occurred within an interval of 90-180 days, with the most recent, after 800 days, at the finger and ankle being 7 and 15 times higher than the initial baseline reading. The intriguing results show bone strontium incorporation and retention follow a pattern, suggesting strontium levels, at least in the ankle, do not plateau within two to three years and will continue to increase over time, as an individual takes strontium supplements. The ability of this IVXRF system to monitor and measure bone strontium levels over time provides a useful diagnostic tool to help gain insight into strontium bone kinetics.
    Full-text · Article · Apr 2012 · Bone
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