Ex vivo evaluation of a coherent normalization procedure to quantify in vivo finger strontium XRS measurements
- Department of Medical Physics, McMaster University, Hamilton, Ontario L8S 4K1 (Canada)
Purpose: Energy dispersive x-ray fluorescence spectroscopy (XRS) measurements were performed on human cadaver index fingers to measure bone strontium content in the presence of intact overlying soft-tissue. This work assesses the feasibility of applying a normalization procedure including soft-tissue correction of x-ray absorption as a means to quantify an ex vivo bone strontium XRS measurement. Methods: Bone strontium measurements were made using an excitation-detection system incorporating an {sup 125}I x-ray excitation source and an Ortec registered Ametek-AMT Si(Li) detector in 180 deg. backscatter geometry. Spectral processing was accomplished using an in-house nonlinear least-squares Marquardt fitting routine. Bone strontium was quantified using an egs5 Monte Carlo based x-ray soft-tissue correction algorithm in conjunction with the normalization of strontium x-rays to the coherent scatter peaks of 35.5 keV {sup 125}I {gamma}-rays. Results: Comparison of tissue intact and bare bone finger XRS measurement quantification attempts revealed an overall discrepancy of 18.6% that is attributed primarily to the significant contribution of soft-tissue to coherent scatter of 35.5 keV source {gamma}-rays and to a lesser degree, inconsistencies with the simulated tissue correction model. Work toward the beginnings of an experimentally derived tissue correction model, as a means to validate the simulated model, have been reported. Two observations hinted at a systematic inflation of the observed K{beta} peak area. First, strontium concentrations estimated by K{alpha} peak areas were less than the K{beta} peak areas by 28.6% (p < 0.0001) and 10.5% (p < 0.001) for tissue intact and bare bone measurements, respectively. Second, the K{alpha}:K{beta} x-ray average ratios between tissue corrected (3.61 {+-} 0.55) and bare bone predicted (4.4 {+-} 0.4) did not agree (p < 0.0001) and pointed to shortcomings with the current processing treatment of strontium K x-ray peak area extraction. Through finger bone XRS measurements, bone strontium concentration in the Caucasian population was estimated at 95 {+-} 15 {mu}g Sr/g dry bone. Conclusions: The discrepancies observed: between quantification attempts of tissue corrected and bare bone measurements, the inflated estimates of K{beta} relative to K{alpha} peak concentrations and between observed and expected K{alpha}:K{beta} ratios, have indicated that shortcomings with the bone strontium coherent normalization and tissue correction procedure exist. Coherent scatter contribution of soft-tissue overlying bone, tissue correction model limitations, and spectra processing issues are all mentioned as sources of observed discrepancies.
- OSTI ID:
- 22098762
- Journal Information:
- Medical Physics, Vol. 39, Issue 2; Other Information: (c) 2012 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-2405
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
62 RADIOLOGY AND NUCLEAR MEDICINE
ABSORPTION
ALGORITHMS
BONE TISSUES
CORRECTIONS
EXTRACTION
FINGERS
IN VIVO
IODINE 125
KEV RANGE
LEAST SQUARE FIT
LI-DRIFTED SI DETECTORS
MONTE CARLO METHOD
SIMULATION
SKELETON
SPECTRA
STRONTIUM
X RADIATION
X-RAY FLUORESCENCE ANALYSIS
X-RAY SPECTROSCOPY