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Magnetic resonance imaging-based radiation-absorbed dose estimation of 166Ho microspheres in liver radioembolization
Peter R Seevinck1, Gerrit H van de Maat, Tim C de Wit
1Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands. p.seevinck@umcutrecht.nl
Purpose:
To investigate the potential of magnetic resonance imaging (MRI) for accurate assessment of the three-dimensional (166)Ho activity distribution to estimate radiation-absorbed dose distributions in (166)Ho-loaded poly (L-lactic acid) microsphere ((166)Ho-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 (166)Ho-PLLA-MS. Three-dimensional radiation-absorbed dose distributions were estimated at the voxel level by convolving the (166)Ho activity distribution, derived from quantitative MRI data, with a (166)Ho 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 (166)Ho-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 (166)Ho-PLLA-MS in an ex 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 (166)Ho-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 (166)Ho-PLLA-MS activity distributions, enabling localized intrahepatic radiation-absorbed dose estimation by convolution with a (166)Ho dose point-kernel for liver radioembolization treatment optimization and evaluation.
Insights
Magnetic resonance imaging (MRI) accurately assesses Holmium-166 microsphere distribution for liver radioembolization. This enables precise radiation dose estimation, optimizing treatment planning and evaluation.
Area of Science:
- Nuclear Medicine
- Medical Imaging
- Radiotherapy
Background:
- Liver radioembolization uses Holmium-166 loaded poly (L-lactic acid) microspheres ((166)Ho-PLLA-MS).
- Accurate assessment of (166)Ho activity distribution is crucial for estimating radiation-absorbed dose.
- Current imaging techniques may have limitations in precise 3D activity quantification.
Purpose of the Study:
- To evaluate the potential of magnetic resonance imaging (MRI) for precise 3D assessment of (166)Ho activity distribution.
- To estimate radiation-absorbed dose distributions in (166)Ho-PLLA-MS liver radioembolization using MRI data.
Main Methods:
- Experiments were conducted on phantoms and an ex vivo human liver containing (166)Ho-PLLA-MS.
- Quantitative MRI was used to derive (166)Ho activity distribution.
- Three-dimensional radiation-absorbed dose distributions were calculated using MCNP-generated dose point-kernels.
- MRI-based dose distributions were compared with CT, SPECT, and autoradiography.
Main Results:
- MRI accurately assessed local (166)Ho-PLLA-MS mass and activity distributions with high correlation to dose calibrator measurements.
- MRI-based dose distributions showed strong visual correspondence with SPECT-based distributions in an ex vivo human liver.
- Quantitative analysis indicated that MRI, SPECT, and dose calibrator estimations of (166)Ho-PLLA-MS amounts agreed within 10%.
Conclusions:
- Quantitative MRI provides accurate 3D (166)Ho-PLLA-MS activity distributions.
- This enables localized intrahepatic radiation-absorbed dose estimation for liver radioembolization.
- MRI facilitates optimization and evaluation of liver radioembolization treatments.
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