Detection of gadolinium deposition in cortical bone with ultrashort echo time T1mapping: an ex vivo study in a rabbit model

Objectives To investigate the capacity of ultrashort echo time (UTE) T(1)mapping to non-invasively assess gadolinium deposition in cortical bone after gadolinium-based contrast agent (GBCA) administration. Methods Twenty-eight New Zealand rabbits (male, 3.0-3.5 kg) were randomly allocated into control, macrocyclic, high-dose macrocyclic, and linear GBCA groups (n= 7 for each group), and respectively given daily doses of 0.9 ml/kg bodyweight saline, 0.3 mmol/kg bodyweight gadobutrol, 0.9 mmol/kg bodyweight gadobutrol, and 0.3 mmol/kg bodyweight gadopentetate dimeglumine for five consecutive days per week over a period of 4 weeks. After a subsequent 4 weeks of recovery, the rabbits were sacrificed and their tibiae harvested. T(1)value of cortical bone was measured using a combination of UTE actual flip angle imaging and variable repetition time on a 7T animal scanner. Gadolinium concentration in cortical bone was measured using inductively coupled plasma mass spectrometry (ICP-MS). Pearson's correlation between R(1)value (R-1= 1/T-1) and gadolinium concentration in cortical bone was assessed. Results Bone T(1)values were significantly lower in the lower-dose macrocyclic (329.2 +/- 21.0 ms,p< 0.05), higher-dose macrocyclic (316.8 +/- 21.7 ms,p< 0.01), and linear (296.8 +/- 24.1 ms,p< 0.001) GBCA groups compared with the control group (356.3 +/- 19.4 ms). Gadolinium concentrations measured by ICP-MS in the control, lower-dose macrocyclic, higher-dose macrocyclic, and linear GBCA groups were 0.04 +/- 0.02 mu g/g, 2.60 +/- 0.48 mu g/g, 4.95 +/- 1.17 mu g/g, and 13.62 +/- 1.55 mu g/g, respectively. There was a strong positive correlation between R(1)values and gadolinium concentrations in cortical bone (r= 0.73,p< 0.001). Conclusions These results suggest that UTE T(1)mapping has the potential to provide a non-invasive assessment of gadolinium deposition in cortical bone following GBCA administration.