Quantitative Measurements of Bone Remodeling Using 99mTc-Methylene Diphosphonate Bone Scans and Blood Sampling
Amelia E.B. Moore 1*,
Glen M. Blake 1,
and
Ignac Fogelman 1
1 School of Medicine, King's College London, London, United Kingdom
* To whom correspondence should be addressed. E-mail: amelia.moore{at}kcl.ac.uk.
 |
Abstract |
|---|
Quantitative studies of bone using 99mTc-methylene diphosphonate (99mTc-MDP) have a potentially valuable role in investigating the treatment of patients with metabolic bone disease. In this study we compared 3 different methods of measuring whole-skeleton 99mTc-MDP plasma clearance (Kbone) in 12 osteoporotic postmenopausal women (mean age, 67.3 y) before participation in a clinical trial of an osteoporosis therapy. The aim was to compare the consistency and accuracy of the 3 methods before their use in evaluating the subjects' response to treatment. Methods: Subjects were injected with 600 MBq 99mTc-MDP and 3 MBq 51Cr-ethylenediaminetetraacetic acid (51Cr-EDTA) and whole-body bone scan images were acquired at 10 min, 1, 2, 3, and 4 h. Two-minute static images of the thighs were acquired immediately after the 1- to 4-h whole-body scans. Six blood samples were taken between 5 min and 4 h, and free 99mTc-MDP was measured using ultrafiltration. The glomerular filtration rate (GFR) was estimated from the 51Cr-EDTA plasma curve. The methods used to evaluate Kbone were (a) the area-under-the-curve (AUC) method, in which the GFR measurement was subtracted from the total (bone plus renal) clearance (Ktotal) measured from the free 99mTc-MDP plasma curve; (b) the modified Brenner method, in which 99mTc-MDP renal clearance estimated from the whole-body counts was subtracted from the total clearance measured from the rate of elimination of tracer from soft tissue; and (c) the Patlak plot method, which was also used to derive regional values of Kbone for the skull, spine, pelvis, arms, and legs. Results: There was good agreement between the 3 methods of measuring Kbone. (mean Kbone ± SD: AUC method, 30.3 ± 6.4 mL·min-1; Brenner method, 31.1 ± 5.8 mL·min-1; Patlak method, 35.7 ± 5.8 mL·min-1). The correlation coefficients between the methods varied from r = 0.767 (P = 0.004) to r = 0.805 (P = 0.002). Regional measurements of 99mTc-MDP clearance gave the following percentages of the whole-skeleton clearance: skull, 13.3%; spine, 16.6%; pelvis, 17.2%; arms, 11.1%; legs, 23.7%. Conclusion: The 3 methods gave consistent and accurate measurements of Kbone. The Patlak method can be used to study regional as well as total-skeleton values of Kbone.
Key Words:
99mTc-methylene diphosphonate, bone remodeling, bone plasma clearance
