Magnetic Resonance Imaging-Based Radiation-Absorbed Dose Estimation of ¹⁶⁶Ho Microspheres in Liver Radioembolization

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• 作者：Peter R. Seevinck ; Ph.D.^&lowast ; ; ^{p.seevinck@umcutrecht.nl} ; Gerrit H. van de Maat ; M.Sc.^&lowast ; ; Tim C. de Wit ; Ph.D.^&Dagger ; ; Maarten A.D. Vente ; D.V.M. ; Ph.D.^&dagger ; ; Johannes F.W. Nijsen ; Ph.D.^&dagger ; ; Chris J.G. Bakker ; Ph.D.^&lowast ; ; ^&dagger ;
• 关键词：Radioembolization ; Holmium microspheres ; Dosimetry ; Magnetic resonance imaging ; Radiation-absorbed dose
• 刊名：International Journal of Radiation Oncology*Biology*Physics
• 出版年：2012
• 期刊代码：136_03603016
• 类别：med
• 出版时间：1 July, 2012
• 卷：83
• 期：3
• 页码：e437-e444
• 文件大小：941 K

摘要

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Purpose

To investigate the potential of magnetic resonance imaging (MRI) for accurate assessment of the three-dimensional ¹⁶⁶Ho activity distribution to estimate radiation-absorbed dose distributions in ¹⁶⁶Ho-loaded poly (L-lactic acid) microsphere (¹⁶⁶Ho-PLLA-MS) liver radioembolization.

Methods and Materials

MRI, computed tomography (CT), and single photon emission CT (SPECT) experiments were conducted on an anthropomorphic gel phantom with tumor-simulating gel samples and on an excised human tumor-bearing liver, both containing known amounts of ¹⁶⁶Ho-PLLA-MS. Three-dimensional radiation-absorbed dose distributions were estimated at the voxel level by convolving the ¹⁶⁶Ho activity distribution, derived from quantitative MRI data, with a ¹⁶⁶Ho dose point-kernel generated by MCNP (Monte Carlo N-Particle transport code) and from Medical Internal Radiation Dose Pamphlet 17. MRI-based radiation-absorbed dose distributions were qualitatively compared with CT and autoradiography images and quantitatively compared with SPECT-based dose distributions. Both MRI- and SPECT-based activity estimations were validated against dose calibrator measurements.

Results

Evaluation on an anthropomorphic phantom showed that MRI enables accurate assessment of local ¹⁶⁶Ho-PLLA-MS mass and activity distributions, as supported by a regression coefficient of 1.05 and a correlation coefficient of 0.99, relating local MRI-based mass and activity calculations to reference values obtained with a dose calibrator. Estimated MRI-based radiation-absorbed dose distributions of ¹⁶⁶Ho-PLLA-MS in an ex聽vivo human liver visually showed high correspondence to SPECT-based radiation-absorbed dose distributions. Quantitative analysis revealed that the differences in local and total amounts of ¹⁶⁶Ho-PLLA-MS estimated by MRI, SPECT, and the dose calibrator were within 10%. Excellent agreement was observed between MRI- and SPECT-based dose-volume histograms.

Conclusions

Quantitative MRI was demonstrated to provide accurate three-dimensional ¹⁶⁶Ho-PLLA-MS activity distributions, enabling localized intrahepatic radiation-absorbed dose estimation by convolution with a ¹⁶⁶Ho dose point-kernel for liver radioembolization treatment optimization and evaluation.