Search the BPG

Image quality


Images are assessed for quality and completeness prior to submitting for reporting or where appropriate, adjusting treatments


+ Importance of image quality

  • The quality of the image should be such that the professional interpreting the image is able to answer the clinical question being asked.
    • In diagnostic imaging, this implies the image is of sufficient diagnostic quality
    • In radiation therapy, this implies the image is of sufficient quality to direct planning and treatment


  • Submitting suboptimal images affects the interpretation of the image and may impact the patient’s care and outcomes:1
    • An image of poor diagnostic quality may lead to misdiagnosis, suboptimal decisions or delays in care for the patient
    • Repeat images may result in unnecessary exposure to radiation for the patient and/or MRT, and increased costs for the healthcare system

+ Judging the quality of an image

  • MRTs are responsible for the critical evaluation of images, including:2
    • Review of images for positioning and quality
    • Decisions on acceptability of images, including whether or not to repeat imaging

  • A judgment on image quality requires an understanding of the clinical question that is being investigated.
    • “Does this image clearly demonstrate the information necessary to answer the clinical question?”

  • Image quality is best judged using a logical and analytical process, with consistent standards across a department and facility.1,3,4
    • The overall density/signal to noise and contrast/weighting of the image is verified
    • The appropriate anatomy is demonstrated
    • Correct patient positioning (angles, planes and coverage) is verified

  • MRTs evaluate common issues affecting image quality:5
    • Sharpness
    • Exposure
    • Image artefacts

  • In addition, MRTs verify processing, labeling and annotation:
    • Correct patient demographic information
    • All required post processing is complete
    • Images are labeled correctly
    • Image markers are correctly placed

+ Dealing with suboptimal images

  • If an image is not of the required diagnostic quality to answer the clinical question, then repeat imaging may be necessary.
    • Images that are diagnostic, with clearly identifiable pathology, should not be repeated because of suboptimal image quality


  • Before an imaging procedure is repeated, an MRT considers:
    • Have factors that contributed to suboptimal image been identified and corrected?
    • Are there any specific patient factors or circumstances that affect the appropriateness of repeat imaging?
    • Is there a need to consult another healthcare provider?


  • Suboptimal images are retained for quality control activities such as the reject analysis.

+ Image quality control

  • Each suboptimal image is an opportunity for analysis and reflection on technique used.3
    • A critical approach to image quality provides an opportunity to improve the quality of care for future patients


  • Reject analysis, using ‘rejected’ images to determine the cause of the rejection and repeat imaging, is performed periodically to formalize analysis.1,6,7
    • The objective of reject analysis is to reduce the number of repeated examinations by correcting problems and improving skills6
    • Images of suboptimal quality are sorted according to the reason for rejection
    • Trends are identified and analyzed in an attempt to identify the source of the problem
    • Health Canada suggests that guidelines for an effective reject-repeat analysis program are formally documented within the department's quality control protocol manual8


  • Each identified problem requires an appropriate corrective action and reasons for decreased image quality are determined and corrected so future patients are not affected.
  • All action taken is reported and documented so that MRTs may benefit from the learnings of the reject analysis in the future.1
  • MRTs are familiar with the policy concerning repeat imaging and reject analysis at their own facility.

+ References

  1. International Atomic Energy Agency. IAEA Training Material on Radiation Protection in Diagnostic and Interventional Radiology. Part 23: Organizing a QA in diagnostic radiology.
  2. Canadian Association of Radiologists. CAR Standards for General (Plain) Radiography. 2000. Available at: Accessed February 21, 2013.
  3. Carlton RR, Adler AM, eds. Principles of Radiographic Imaging: An Art and a Science, 4th Ed. Canada: Thomson; 2006.
  4. Campeau FE. Radiography: Technology, Environment, Professionalism. Philadelphia, PA: Lipincott, Williams and Wilkins; 1999.
  5. Papp J. Quality Management in the Imaging Sciences, 4th Ed. St. Louis, MO: Mosby Elsevier; 2011.
  6. International Atomic Energy Agency website. Radiation protection of patients. Available at: Accessed February 21, 2013.
  7. European Commission. European Guidelines on Quality Criteria for Diagnostic Radiographic Images. Available at: Accessed February 21, 2013.
  8. Health Canada. Diagnostic X-Ray Imaging Quality Assurance: An Overview. Available at: April 29, 2013.

Related guidelines

>Quality assurance
>Markers and annotation



May 10, 2013


Canadian Association of Medical Radiation Technologists
85 Albert St, Suite 1000, Ottawa, ON, K1P 6A4
phone: 613 234-0012 / 800 463-9729
fax: 613 234-1097