Measuring bone metabolic activity in dialysis patients with renal osteodystrophy using [18F]-Sodium Fluoride positron emission tomography- comparison between static and dynamic measurements

AUTHORS

Louise Aaltonen, Niina Koivuviita, Marko Seppänen, Vesa Oikonen, Anna K. Kirjavainen, Heikki Kröger, Eliisa Löyttyniemi, Kaj Metsärinne

ABSTRACT

Background

Dynamic [18F]NaF PET has shown promising results in the measurement of bone metabolism in patients with renal osteodystrophy. Dynamic PET scans are challenging in clinical practice, and the objective of this study was to evaluate whether standardized uptake values measured by [18F]NaF PET could be a feasible method.

Methods

Twenty-eight patients on maintenance dialysis with confirmed renal osteodystrophy underwent a dynamic [18F]NaF PET scan. As a reference for bone metabolism, a bone biopsy was obtained from the anterior iliac crest (AIC). Tracer activity in bone was measured using Patlak analysis and standardized uptake values (SUV). SUV was also adjusted to tracer activity measured from the aorta 48–60 min after injection (SUVR).

Results

SUV measured in the lumbar spine (L1-L4) and at the AIC did not correlate with histomorphometric parameters obtained by bone biopsy. There was no statistically significant difference between SUV in different turnover groups. When adjusting the mean bone uptake of fluoride in the lumbar spine, there was a strong correlation with the blood clearance of tracer to bone (Ki). SUVR also correlated significantly with histomorphometric markers obtained by bone biopsy.

Conclusions

These results suggest that measurements of tracer activity in the blood 48–60 min after tracer injection could be used to correct SUVs from static [18F]NaF PET scans. However, further research and validation of the method is needed.

Effect of vitamin D metabolites on bone histomorphometry in healthy black and white women: An attempt to unravel the so-called vitamin D paradox in blacks

AUTHORS

Shijing Qiu, George Divine, Sudhaker D.Rao

ABSTRACT

An apparent vitamin D paradox, characterized by lower serum 25-hydroxyvitamin D (25(OH)D) levels and higher bone mineral density, is present in black population. In contrast, blacks have higher serum 1,25-dihydroxyvitamin D (1,25(OH)2D) levels. The effect of 1,25(OH)2D on the skeleton is not fully understood. We examined serum 25(OH)D, 1,25(OH)2D and bone histomorphometry in 50 black and white women (25 each) matched for age, menstrual status, and BMI. Histomorphometric indices related to bone structure, remodeling and mineralization were measured in cancellous bone in iliac bone biopsies. Data analyses led to the following results: 1) serum 25(OH)D was significantly lower and 1,25(OH)2D was significantly higher in black than in white women, but neither blacks nor whites revealed significant correlation between these two vitamin D metabolites. 2) there was no significant difference in PTH levels between blacks and whites. 3) except for greater trabecular thickness (Tb.Th) in blacks, there were no significant differences in other histomorphometric variables between the two ethnic groups. 4) osteoid surface (OS/BS), unlabeled osteoid surface (ulOS/BS), and osteoblast surface (ObS/BS) significantly correlated with serum 1,25(OH)2D levels. We conclude that lower serum 25(OH)D levels in blacks do not impair bone structure and remodeling, nor decrease bone mineralization. Higher serum 1,25(OH)2D levels in blacks may help preserve bone mass by stimulating bone formation via increasing osteoblast number and function, but moderately inhibit terminal bone mineralization as shown by higher ulOS/BS.