MSc Defence: EVALUATING THE STABILITY OF HYDROXYAPATITE PHANTOMS AND THE POTENTIAL OF CALCIUM PHOSPHATE GLASSES AS PHANTOM MATERIALS FOR THE CALIBRATION OF IN VIVO X-RAY SPECTROMETRY-BASED SYSTEM OF BONE STRONTIUM QUANTIFICATION

Student: Matthew Micsa

Supervisor: Dr. Eric Da Silva

Abstract

Strontium in bone can be quantified using an 125I-induced in vivo X-ray fluorescence (IVXRF) spectrometry-based system. The standard plaster of Paris phantoms used to calibrate IVXRF bone metal quantification systems have introduced numerous complications in terms of their suitability. Hydroxyapatite phantoms have been proposed as being an alternative choice for calibration such that the required coherent conversion (correction) factor is removed from the protocol. The chemical stability of hydroxyapatite, however, has been brought to question when calculating the correction factor. An experimental study was conducted to assess the long-term chemical stability of hydroxyapatite phantoms. A simulation study was carried to evaluate if calcium phosphate glasses can be used a replacement for hydroxyapatite. It was concluded that using hydroxyapatite phantoms as calibrators requires acknowledgement of its chemical conversion and a possible introduction of uncertainty into the calibration procedure. Conventional calcium phosphate glasses, although desirable substitutes, were found to be unsuitable as calibrators on the basis of removing the coherent conversion factor from the calibration protocol.