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  • Purpose
  • FDA Award
  • Questions
  • Role of the QMP
  • CT Dose-Check
  • Protocols
  • Lexicon
  • Education Slides

Statement of Purpose

The American Association of Physicists in Medicine (AAPM) is a professional organization whose members include board-certified medical physicists who specialize in the safe and effective use of radiation in medicine. Medical physicists partner with radiologists, technologists, regulators, manufacturers, administrators and others to ensure that CT scans are performed using the minimum amount of radiation required to obtain the diagnostic information for which the CT scan was ordered.

The collection of settings and parameters that fully describe a CT examination is referred to as the exam protocol. These protocols specify how data collection and reconstruction, patient positioning and contrast administration are to be performed. The effect of these settings on the final exam quality or dose can be dramatic; a number of the settings are inter-related, where changing one parameter can require adapting several other parameters if image quality and/or dose are to be maintained at a specified level. Thus, the quality and dose of a CT exam are largely predetermined by the protocol used. In CT, there is however no single protocol that is "the correct protocol"; acceptable image quality and dose can be achieved using many different combinations of scan parameters.

In light of the increase in the number of CT exams performed in the US, concerns about variability in doses and/or image quality used by different practices or scanner models to accomplish similar diagnostic tasks, and several unfortunate cases of patient injury due to the use of improper scan protocols, the AAPM is committed to the publication of a set of reasonable scan protocols for frequently performed CT examinations, summarizing the basic requirements of the exam and giving several model-specific examples of scan and reconstruction parameters. This work is the charge of the Working Group on Standardization of CT Nomenclature and Protocols, whose membership includes academic and consulting medical physicists who specialize in CT imaging, representatives of each of the major CT scanner manufacturers, and liaisons to the American College of Radiology, American Society of Radiology Technologists, and the Food and Drug Administration.

The provided protocols are considered by the Working Group to be reasonable and appropriate to the specified diagnostic task. The settings provided are representative of typical clinical values and they may not always match default protocols.

The provided protocols represent a sampling of currently available scanner models. They are not intended to provide comprehensive information for all available scanner models.

American Association of Physicists in Medicine (AAPM) Working Group Recognized by the FDA

On June 10, 2013, the Director of the Center for Devices and Radiological Health (CDRH) of the Federal Drug Administration (FDA), Jeffrey Shuren, M.D., J.D., awarded the AAPM Working Group on Standardization of CT Nomenclature and Protocols the CDRH Director’s Special Citation Award.  This award was presented “For developing CT imaging radiation safety instructional materials through a collaboration of end-users, CT manufacturers, and the Food and Drug Administration.”

AAPM WGCTNP representative members just after FDA award ceremonyThe FDA award stated:

In 2010, FDA released an "Initiative to Reduce Unnecessary Radiation Exposure from Medical Imaging", which targets high dose imaging modalities, including CT. A key partner in following through on the goals of this Initiative has been the American Association of Physicists in Medicine (AAPM) Working Group on Standardization of CT Nomenclature and Protocols. Meeting bi-weekly since 2010, the group has worked tirelessly to advance CT radiation safety through publication of publicly available resources on the AAPM website (http://www.aapm.org/pubs/CTProtocols/).

The effect of these efforts has been to improve public health by optimizing the dose of ionizing radiation during CT scans and by helping to eliminate accidental radiation overdoses during CT scanning.

The group is an outstanding example of what can be accomplished through collaboration of key stakeholders. The group includes medical physicists, radiologists, radiologic technologists, industry representatives, and regulators, from AAPM, the American College of Radiology (ACR), the American Society of Radiologic Technologists (ASRT), the Society for Pediatric Radiology (SPR), the Image Gently Alliance, the Medical Imaging and Technology Alliance, from all 7 U.S. CT manufacturers, and from the FDA.

Additional Scanner Model Questions

Users with questions specific to a certain manufacturer or scanner model should contact the applications support line for that product. The AAPM cannot respond to requests for specific customer support.

How to reach Applications Support for:

  • GE Healthcare:

  • Hitachi:

    • CT Help Desk: 877-228-2777
  • NeuroLogica Corporation:

  • Neusoft:

  • Philips Healthcare:

  • Siemens Healthcare:

    • UPTIME Applications Support: 800-888-7436 (Option 3)
    • Website
  • Toshiba Medical Systems:

Equipment Performance Questions

Users experiencing problems in performing an exam, or that have questions on the operation or performance of their systems, should contact their service provider. The AAPM cannot respond to requests for specific customer support.

How to reach Technical Support for:

  • GE Healthcare:

  • Hitachi:

    • CT Help Desk: 877-228-2777
  • NeuroLogica Corporation:

  • Neusoft:

  • Philips Healthcare:

  • Siemens Healthcare:

    • UPTIME Technical Support: 800-888-7436 (Option 2)
  • Toshiba Medical Systems:

Role of Qualified Medical Physicist (QMP)

Diagnostic medical physicists play an essential role in the delivery of high quality and safe CT examinations. For example, accreditation by the American College of Radiology in CT imaging requires the services of a qualified medical physicist, stating that the qualified medical physicist:

  • Must be familiar with the principles of imaging physics and of radiation protection; the guidelines of the National Council on Radiation Protection and Measurements; laws and regulations pertaining to the performance of the equipment being tested; the function, clinical uses, and performance specifications of the imaging equipment; and calibration processes and limitations of the instruments used for performance testing.
  • The qualified medical physicist should be available for consultation regarding patient dosimetry issues.
  • The qualified medical physicist is responsible for the conduct of all surveys of the CT equipment.

A primary motivation of this working group is to support and equip AAPM members in the performance of these important duties. These materials are therefore being developed specifically for the medical physics community. Although many radiologists and technologists are well educated in the technical aspects of protocol development, there are some users who may have a difficult time in understanding and correctly implementing the provided information. We fundamentally believe that patients are best served when radiologists, technologists and medical physicists work together, each bringing their unique skill set and perspective to the task of protocol optimization. Radiologists and technologists desiring access to these protocols should contact the qualified medical physicist who supports their practice. Many practices have initiated protocol review teams to individually review each protocol in their practice. A qualified medical physicist is a necessary member of this team and can facilitate comparison of a site's existing protocols with those recommended here.

Available Protocols

Adult Protocols

Your feedback regarding the content of this website is welcome. Feedback regarding this website will not be monitored daily. Users experiencing problems in performing an exam should contact their service provider.

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CT scan parameters: Translation of terms for different manufacturers

AAPM CT Lexicon version 1.3   04/20/2012


For the CT technologist who operates multiple scanner models, perhaps from multiple manufacturers, the variability in names for important scan acquisition and reconstruction parameters can lead to confusion, reduced comfort and an increased potential for error. The intent of this CT terminology lexicon is to allow users to translate important CT acquisition and reconstruction terms between different manufacturers' systems.

This represents a first step in the terminology standardization effort undertaken by this working group. Phase 2 of our work will:

  1. Identify relevant terms from established standard lexicons (e.g. RadLex and DICOM) and other relevant literature and publish an expanded lexicon including these terms.
  2. Form consensus recommendations on preferred terms.

This website will be updated as the terminology standardization work progresses.

The generic descriptions or terms in the first column are intended to orient the user to the relevant concepts; they are not consensus "preferred terms." The generic descriptions are not based on any single existing or pending terminology standard; however the references in the pdf attachment were consulted in developing the generic descriptions. Future efforts of this Working Group include making recommendations for standardized terminology.

A number of individuals and groups have advocated for terminology standardization in CT, including at a March 30-31, 2010 FDA public meeting entitled "Device Improvements to Reduce Unnecessary Radiation Exposure from Medical Imaging" (transcripts available here; see p. 153-155). Participants proposed a cooperative effort among professional organizations (AAPM, ASRT, ACR, etc.), industry, FDA, and standards organizations to accomplish this task, as is now being undertaken by this Working Group.

AAPM CT Lexicon version 1.3   04/20/2012

Computed Tomography Radiation Dose Education Slides

This section contains documents with information on how CT acquisition parameters and CT scanner features affect the radiation dose used for a given study and how the dose is reported and tracked. These slides are intended for educational purposes and may be distributed freely with proper acknowledgement ("Courtesy of the AAPM Working Group on CT Nomenclature and Protocols").

The "General Dose Education Slides" are available as a PowerPoint or PDF file and contains vendor-independent information on CT acquisition parameters, dose modulation and reduction and dose display. The entire slide set or pieces of it may be incorporated into any educational presentation as the user sees fit.

The Power Point slides that are accessible through the following link deal with factors that affect radiation dose in CT studies. They may be used as a resource for developing presentations on this topic.

General Dose Education Slides

The "Vendor Dose Education Slides" are available as PDF files only and individual slides may not be modified by the user. Each slide set follows the same outline as the General Dose Education Slides but includes vendor-specific screen shots and information on vendor specific parameters and features. The vendor specific slides were generated with the assistance of the vendor and screen shots of the scanner console/interface and descriptions of the vendor specific acquisition parameters are not representative of all scanners and software versions produced by the vendor. The slides are for instructional purposes only.

Vendor Dose Education Slides