Abstract
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Introduction: Computed tomography (CT) is an imaging modality which plays a major role in radiology and nuclear medicine, including PET/CT and SPECT/CT hybrid imaging, and continues to see increasing use worldwide [1]. Robust, dependable, and accessible tools for tracking patient CT doses are clearly important. Assessment of organ doses and effective dose using dosimetry tools is an important factor in medical imaging as it provides key indicator quantities for health care professionals to manage the technology, and forms a basis for development, standardization, and optimization of imaging protocols. Such metrics are also requisite for the consideration of radiation risks associated with a technology’s use and application.
As part of the MIRDsoft.org community software development project, MIRDct has been developed to provide organ model-based CT dosimetry. The software enables quick estimation of absorbed doses to organs and effective dose given user input of scan parameters. Additionally, as an optional output, the software calculates risk evaluation quantities such as lifetime attributable risk [2] and risk index [3].
Methods: MIRDct is built in Microsoft excel platform, providing accessibility, intuitive navigation and an easy to use interface.
Key components of MIRDct include the following.
Realistic anatomical models: State-of-art refence models, with 12 ICRP mesh-type family phantoms initially available. (additional phantoms currently being generated). Graphical user interface: a single-screen, user-friendly and intuitive interface provides the functionality required for dosimetry evaluations. Dosimetric models: Dose engine and Tube Current Modulation (TCM) is included. Uncertainty evaluation: Software identifies and quantitates sources of error and allows users to propagate these into the calculational results, if desired. CT models database: CT-slice-specific organ dose coefficients, CT manufacturer, model, collimations, kVp, and bowtie filters.
In MIRDct all processing is available for review to users in spreadsheet format (i.e. open source). All the calculations are transparent and can be used for quality assurance and/or education. MIRDct can ideally be utilized by students, educators, and professionals in the field.
Results: MIRDct software allow easy and fast calculations for effective dose (using ICRP 103 tissue weighting factors) and organ absorbed dose. Currently the software is undergoing benchmarking and testing, which will be completed before release. MIRDct is part of the MIRDsoft radiation dosimetry community platform which has been endorsed by the SNMMMI MIRD committee, the software is projected to be ready and be freely distributed in fall 2022. The novelty, and accessibility of the tool for model-base CT dosimetry and radiation risk assessment open the space for future innovation and updates.
It is intended that MIRDct will be integrated with other MIRDsoft tools such MIRDcalc [4] and MIRDfit for hybrid imaging dosimetry and may ideally serve as a tool to help with protocol standardization.
From the results displayed in the graphical interface, the user can see several graphics with useful information about the absorbed dose in organs, effective dose percentage of contribution and slide-by-slice dose profile. These are valuable indicators for results communication and for educational purposes.
Conclusions: In preliminary development and testing, MIRDct has shown to provide a user-friendly and intuitive interface for calculation and reporting CT organ absorbed doses. The software provides robust processing, graphical quality control checks, innovative supporting features, integration of latest generation/emerging computational phantom models, instant numeric and graphical results. MIRDct is slated to be a modern software for CT dosimetry, and freely available for the community. In the future, the MIRDct and MIRDcalc projects will be integrated together, to provide hybrid dosimetry analyses.
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