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  • 1
    In: Medical Physics, Wiley, Vol. 50, No. 2 ( 2023-02), p. 935-946
    Abstract: Transarterial radioembolization (TARE) is a treatment modality for liver tumors during which radioactive microspheres are injected into the hepatic arterial system. These microspheres distribute throughout the liver as a result of the blood flow until they are trapped in the arterioles because of their size. Holmium‐166 ( 166 Ho)‐loaded microspheres used for TARE can be visualized and quantified with MRI, as holmium is a paramagnetic metal and locally increases the transverse relaxation rate . The current 166 Ho quantification method does not take regional differences in baseline values (such as between tumors and healthy tissue) into account, which intrinsically results in a systematic error in the estimated absorbed dose distribution. As this estimated absorbed dose distribution can be used to predict response to treatment of tumors and potential toxicity in healthy tissue, a high accuracy of absorbed dose estimation is required. Purpose To evaluate pre‐existing differences in distributions between tumor tissue and healthy tissue and assess the feasibility and accuracy of voxelwise subtraction‐based calculation for MRI‐based dosimetry of holmium‐166 transarterial radioembolization ( 166 Ho TARE). Methods MRI data obtained in six patients who underwent 166 Ho TARE of the liver as part of a clinical study was retrospectively evaluated. Pretreatment differences in distributions between tumor tissue and healthy tissue were characterized. Same‐day pre‐ and post‐treatment maps were aligned using a deformable registration algorithm and subsequently subtracted to generate voxelwise maps and resultant absorbed dose maps. Image registration accuracy was quantified using the dice similarity coefficient (DSC), relative overlay (RO), and surface dice (≤4 mm; SDSC). Voxelwise subtraction‐based absorbed dose maps were quantitatively (root‐mean‐square error, RMSE) and visually compared to the current MRI‐based mean subtraction method and routinely used SPECT‐based dosimetry. Results Pretreatment values were lower in tumors than in healthy liver tissue (mean 36.8 s −1 vs. 55.7 s −1 , P = 0.004). Image registration improved the mean DSC of 0.83 (range: 0.70–0.88) to 0.95 (range: 0.92–0.97), mean RO of 0.71 (range 0.53–0.78) to 0.90 (range: 0.86–0.94), and mean SDSC ≤4 mm of 0.47 (range: 0.28–0.67) to 0.97 (range: 0.96–0.98). Voxelwise subtraction‐based absorbed dose maps yielded a higher tumor‐absorbed dose (median increase of 9.0%) and lower healthy liver‐absorbed dose (median decrease of 13.8%) compared to the mean subtraction method. Voxelwise subtraction‐based absorbed dose maps corresponded better to SPECT‐based absorbed dose maps, reflected by a lower RMSE in three of six patients. Conclusions Voxelwise subtraction presents a robust alternative method for MRI‐based dosimetry of 166 Ho microspheres that accounts for pre‐existing differences, and appears to correspond better with SPECT‐based dosimetry compared to the currently implemented mean subtraction method.
    Type of Medium: Online Resource
    ISSN: 0094-2405 , 2473-4209
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 1466421-5
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  • 2
    In: European Journal of Nuclear Medicine and Molecular Imaging, Springer Science and Business Media LLC, Vol. 49, No. 13 ( 2022-11), p. 4705-4715
    Abstract: Transarterial radioembolization (TARE) is a treatment for liver tumours based on injection of radioactive microspheres in the hepatic arterial system. It is crucial to achieve a maximum tumour dose for an optimal treatment response, while minimizing healthy liver dose to prevent toxicity. There is, however, no intraprocedural feedback on the dose distribution, as nuclear imaging can only be performed after treatment. As holmium-166 ( 166 Ho) microspheres can be quantified with MRI, we investigate the feasibility and safety of performing 166 Ho TARE within an MRI scanner and explore the potential of intraprocedural MRI-based dosimetry. Methods Six patients were treated with 166 Ho TARE in a hybrid operating room. Per injection position, a microcatheter was placed under angiography guidance, after which patients were transported to an adjacent 3-T MRI system. After MRI confirmation of unchanged catheter location, 166 Ho microspheres were injected in four fractions, consisting of 10%, 30%, 30% and 30% of the planned activity, alternated with holmium-sensitive MRI acquisition to assess the microsphere distribution. After the procedures, MRI-based dose maps were calculated from each intraprocedural image series using a dedicated dosimetry software package for 166 Ho TARE. Results Administration of 166 Ho microspheres within the MRI scanner was feasible in 9/11 (82%) injection positions. Intraprocedural holmium-sensitive MRI allowed for tumour dosimetry in 18/19 (95%) of treated tumours. Two CTCAE grade 3–4 toxicities were observed, and no adverse events were attributed to treatment in the MRI. Towards the last fraction, 4/18 tumours exhibited signs of saturation, while in 14/18 tumours, the microsphere uptake patterns did not deviate from the linear trend. Conclusion This study demonstrated feasibility and preliminary safety of a first in-human application of TARE within a clinical MRI system. Intraprocedural MRI-based dosimetry enabled dynamic insight in the microsphere distribution during TARE. This proof of concept yields unique possibilities to better understand microsphere distribution in vivo and to potentially optimize treatment efficacy through treatment personalization. Registration Clinicaltrials.gov, identifier NCT04269499, registered on February 13, 2020 (retrospectively registered).
    Type of Medium: Online Resource
    ISSN: 1619-7070 , 1619-7089
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2022
    detail.hit.zdb_id: 2098375-X
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  • 3
    In: Gastroenterology, Elsevier BV, Vol. 160, No. 6 ( 2021-05), p. 1970-1985
    Type of Medium: Online Resource
    ISSN: 0016-5085
    RVK:
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2021
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