Improving Health Through Medical Physics

AAPM Newsletter — Volume 42 No.5 — September|October 2017

SCIENCE COUNCIL REPORTCynthia McCollough, PhD, Rochester, MN

Picture of Cynthia McCollough

The CT Subcommittee resides under the Imaging Physics Committee, which is under Science Council. In this month's Science Council Report, we provide an update on the many activities underway within the CT Subcommittee. The CT Subcommittee is comprised of 17 members with deep interest and expertise in CT imaging. In addition, we have a close working relationship and undertake joint initiatives with representatives of industry, DICOM, IEC, ACR, ASRT, and FDA. The work of the Subcommittee includes clinical, educational, and research projects. Current projects and their objectives and progress are summarized here.

Task Group No. 200 - CT Dosimetry Phantoms and the Implementation of AAPM Report Number 111

This report is undergoing final review and approval and will be issued shortly. This comprehensive report translates the theoretical framework developed in Report 111 into a practical set of tests and phantoms. The task group is charged with implementing the methodology of the report of TG111, The Future of CT Dosimetry, into practical recommendations for the acceptance and subsequent periodic testing of computed tomography machines. Included in the work performed by this group has been the design of phantoms and the development of testing methodology.

TG233 - Performance Evaluation of Computed Tomography Systems

This report is also undergoing final review and approval. This report briefly summarizes existing performance evaluation tests in CT and then introduces a series of advanced performance evaluation methods. Some of the topics addressed include advanced image quality assessment techniques including task-based metrology, performance evaluation of iterative reconstruction techniques, and performance assessment of automatic tube current modulation techniques.

TG291 - Task Group on Educational Report on Multi-Energy CT

The purpose of this task group is to prepare a comprehensive educational primer on multi-energy CT. The topics covered include the rationale for and fundamental physics of multi-energy CT, the different commercial implementations of dual-energy CT, dual-energy post-processing, and dosimetric considerations. The report will be completed by the end of 2017.

TG293 - Task Group on Size Specific Dose Estimate (SSDE) for Head CT

This task group is evaluating the relationship between mean dose in the center of the scan volume (SSDE) and the applied radiation (CTDIvol). That is, they are determining the conversion factors for head that parallel those produced in Report 204 for the torso. This report is also nearing completion.

TG299 - Quality Control in Multi-Energy Computed Tomography (MECT)

The rapid adoption of multi-energy CT into clinical practice demands that physicists be provided guidance regarding quality control of these systems and techniques. The charge for this task group is to develop a quality control program for performance evaluation of MECT systems and to define the appropriate tests, frequency, and tolerance limits for MECT system evaluation.

TG300 - Image Quality Registry for CT

This new task group was jointly formed by both the CT Subcommittee and the Imaging Informatics Subcommittee. It seeks to establish a framework for creating a national computed tomography (CT) image quality index registry. Recommendations for specific image quality indices to be collected and methods of data collection, storage, access, analysis, and reporting will be made.

WGCTNP - Alliance for Quality CT

This longstanding working group is officially located within the committee structure under the Technology Assessment Committee but provides routine reports to the CT Subcommittee. The Alliance for Quality CT produces educational documents and protocols for common CT exams, as well as a terminology lexicon and links to manufacturer education information. If you've not visited this site, please explore it. There is a lot of great information can be found here.

DICOM WG 21 Supplement on Multi-Energy CT (Leng)

The CT Subcommittee has regular interactions with the individuals working on CT-related DICOM standards, which recently have included a new DICOM standard on CT protocols (approved) and another on multi-energy CT (nearing completion). It has been extremely valuable to the CT Subcommittee provide the CT-specific expertise in these initiatives to complement the DICOM working groups' expertise in informatics.

IEC Maintenance and Project Teams

The CT Subcommittee receives frequent updates from AAPM members serving on the maintenance and project teams of the International Electrotechnical Committee, which is an international standards organization that creates standards that affect all of the medical imaging and therapy devices relevant to the work of AAPM members. The maintenance team is nearing completion of a revised Acceptance and Constancy testing standard and the project team is moving forward with a standard for calculating Size Specific Dose Estimates.

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