(Tuesday, 7/16/2019) 1:15 PM - 1:45 PM
Room: Exhibit Hall | Forum 1
Purpose: MIM SurePlan (MIM Software, Cleveland OH) allows for voxel based 3D Y-90 treatment planning and dose calculation. This is a paradigm shift from the partition model using diagnostic CT scans and planar Tc-99m MAA images. Here we present lessons learned for implementing this software clinically.
Methods: Similar to the current clinical workflow, the physician contours the liver and treatment volume on a diagnostic contrast CT. These contours are transferred to the Tc-99m MAA SPECT/CT and their accuracy is verified. A pre-defined workflow in SurePlan guides the user in contouring the left and right liver lobes, the lungs and finally returns an injected activity used a dose distribution calculated using the local deposition model (LDM). SurePlan assumes the MAA activity distribution mimics the final Y-90 distribution. The planner can adjust the injected activity to increase the tumor dose while maintaining liver tolerance. Following the procedure, the contours are transferred to the Y-90 bremsstrahlung SPECT/CT and the deposited dose is calculated using the LDM.
Results: Twelve patients were retrospectively processed. Initial observation revealed significant differences in liver morphology between diagnostic and SPECT CTs necessitating extra care when transferring contours. Treatment volumes must also be carefully defined using a combination of the contrast diagnostic CT, angiographic CBCT and MAA SPECT/CT. In the process of determining dose distribution using LDM, one must be careful when increasing injected activity as MAA distributions may not accurately represent Y-90 distributions. Finally, for post dosimetry, the final dose needs to be scaled by a factor to account for lung shunting given that SurePlan restricts activity to the liver since there is noise in the bremsstrahlung SPECT.
Conclusion: The paradigm shift from 2D to 3D planning for Y-90 microspheres poses many challenges but allows for individualized treatment plans with the ability to better estimate doses to patients.
Keywords
Brachytherapy, SPECT, Dosimetry
Taxonomy
TH- Brachytherapy: Dose optimization and planning
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