G.H. van de Maat, P.R. Seevinck, M. Elschot, M.L.J. Smits, H. de Leeuw, A.D. van het Schip, M.A.D. Vente, B.A. Zonnenberg, H.W.A.M. de Jong, M.G.E.H. Lam, M.A. Viergever, M.A.A.J. van den Bosch, J.F.W. Nijsen & C.J.G. Bakker
OBJECTIVES: To demonstrate the feasibility of MRI-based assessment of the intrahepatic Ho-PLLA-MS biodistribution after radioembolisation in order to estimate the absorbed radiation dose.
METHODS: Fifteen patients were treated with holmium-166 ((166)Ho) poly(L-lactic acid)-loaded microspheres (Ho-PLLA-MS, mean 484 mg; range 408-593 mg) in a phase I study. Multi-echo gradient-echo MR images were acquired from which R (2) maps were constructed. The amount of Ho-PLLA-MS in the liver was determined by using the relaxivity r (2) of the Ho-PLLA-MS and compared with the administered amount. Quantitative single photon emission computed tomography (SPECT) was used for comparison with MRI regarding the whole liver absorbed radiation dose.
RESULTS: R (2) maps visualised the deposition of Ho-PLLA-MS with great detail. The mean total amount of Ho-PLLA-MS detected in the liver based on MRI was 431 mg (range 236-666 mg) or 89 ± 19 % of the delivered amount (correlation coefficient r = 0.7; P < 0.01). A good correlation was found between the whole liver mean absorbed radiation dose as assessed by MRI and SPECT (correlation coefficient r = 0.927; P < 0.001).
CONCLUSION: MRI-based dosimetry for holmium-166 radioembolisation is feasible. Biodistribution is visualised with great detail and quantitative measurements are possible.