The aim of this study was to evaluate the relationship between different quantification methods used for the measurement of bone plasma clearance (Ki) using 18F-PET at the hip and lumbar spine.
Twelve healthy postmenopausal women aged 52–71 years were recruited. Each participant underwent 60-min dynamic 18F-PET scans at the lumbar spine and hip on two separate occasions with an injected activity of 90 and 180 MBq, respectively. Image-derived input functions were obtained at the aorta from the lumbar spine scans. Ki was evaluated using a three-compartment four-parameter model (Ki-4k), three-compartment three-parameter model (Ki-3k), Patlak analysis (Ki-Pat), spectral analysis (Ki-Spec) and deconvolution (Ki-Decon). Standardized uptake values (SUVs) were also measured.
The Pearson correlation between Ki-4k and Ki-3k, Ki-Pat, Ki-Spec, Ki-Decon and SUV were 0.91, 0.97, 0.94, 0.95 and 0.93, respectively, with a significance of P less than 0.0001. The differences between the correlations measured using Fisher’s Z-test were not significant (P>0.05). Bland–Altman analysis showed that the limits of agreement for Ki measured as the SD of the differences were 0.0082 (25.9%), 0.0062 (11.7%), 0.0098 (20.1%) and 0.0056 (25.5%) ml/min/ml, respectively, and the biases were −0.0081 (−23.8%), −0.0075 (−23.7%), −0.0107 (−29.5%) and −0.0015 (0.8%) ml/min/ml, respectively.
All five methods of quantification (Ki-3k, Ki-Pat, Ki-Spec, Ki-Decon and SUV) strongly correlated with Ki-4k. Although systematic differences of up to 29% were found between Ki-4k and the other methods (Ki-3k, Ki-Pat, Ki-Spec and Ki-Decon), these should not affect the conclusions of clinical studies, provided the methods are applied consistently. However, care should be taken when comparing reports that use different methods of quantification.
aPET Imaging Centre, St Thomas’ Hospital, King’s College London
bOsteoporosis Screening and Research Unit, Guy’s Hospital, London, UK
cSchool of Medicine and Medical Sciences, University College Dublin, Dublin, Ireland
Correspondence to Tanuj Puri, PhD, PET Imaging Centre, St Thomas’ Hospital, King’s College London, Westminster Bridge Road, London SE1 7EH, UK Tel: +44 20 7188 997; fax: + 44 20 7188 0103; e-mail: email@example.com
Received October 23, 2011
Accepted January 8, 2012