Quantitative Measurement of Regional Bone Metabolism at the Hip Using 18 F-fluoride Positron Emission Tomography: 2008-2011

Research output: ThesisDoctoral Thesis

Abstract

Osteoporosis is a bone disease associated with decreased bone mass leading to high fracture risk at the hip and lumbar spine, which is a major cause of morbidity, mortality, and medical costs worldwide. Bone metabolism is an independent predictor of fracture risk at these clinically important sites. Bone biopsy is considered the gold standard for quantifying regional bone metabolism. However, it is invasive and limited to a single biopsy site at the iliac crest. A common non-invasive clinical solution is to measure biochemical markers of bone metabolism, which assesses the metabolism of the whole skeleton and masks the regional information. 18 F-fluoride positron emission tomography ( 18 F-PET) offers a non-invasive method to quantify regional bone metabolism and has been validated by comparison with bone biopsy. Quantitative measurement of bone metabolism requires dynamic PET data acquisition and complex kinetic analysis for instance, compartmental modelling and non-linear regression. Arterial plasma input functions derived by measuring tracer counts over the aorta offers an alternative to invasive arterial blood sampling and has previously been validated at the lumbar spine. The principal aim of this project was to develop methods to measure bone metabolism at the hip using non-invasive 18 F-PET techniques by validating an image-derived arterial input function (IDAIF) at the femoral artery by direct comparison with the IDAIF at the aorta, by developing and validating a semi-automatic procedure whereby regions of interest at the proximal femur are defined on the CT-component of an 18 F-PET-CT scan. The procedure allows quantitative measurements of bone metabolism at the hip to be obtained with a straightforward PET-CT protocol without the need for additional scans. The bone metabolism at the hip showed 3-fold lower results than those at the lumbar spine (p<0.001) showing that this phenomenon is region specific which might be due (but not limited to) variations in the proportion of trabecular and cortical bone, bone perfusion, loading patterns between these sites and the amount and characteristics of haematopoietic tissue. The bone metabolism measured using six different quantification techniques showed strong correlation of r > 0.88; p < 0.0001. However, the use of standardized uptake value as a measure of bone metabolism remains questionable until its simple values are shown to correlate with the rate of bone formation measurements from the bone histomorphometry data.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • University College Dublin
Award date15 Jul 2012
Publication statusUnpublished - 2011

Keywords

  • osteoporosis
  • PET
  • input function
  • bone metabolism
  • sodium fluoride
  • modeling
  • spine
  • hip
  • validation
  • quantitative
  • methods

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