Task 2. Surveys of Image Quality and Patient Doses

Surveys of image quality and patient doses in simple radiographic examinations: establishing guidance levels and comparison with international standards

Background: The Basic Safety Standards require attention to the image quality, by considering corrective actions "if … the exposures do not provide useful diagnostic information and do not yield the expected medical benefit to patients". If the benefit were lost, the exposure would not be justified. There is tremendous amount of wastage of resources, particularly in developing countries, on images of poor quality. In many situations poor quality images constitute as much as 15-40%. These results in unnecessary radiation exposure to patients, loss of diagnostic information, increased social costs besides the economical aspects on health care. Further, BSS requires that Guidance levels (GLs) for medical exposure shall be established and these are intended to give reasonable indication of doses for averaged sized patients. Many countries have not established GLs. Experience from national surveys in some countries such as UK has shown the possibility of large variation in patient doses for common examination s to the tune of 20 or more in different hospitals or even in different rooms in the same hospital.

Unfortunately, more often that not, quality assurance (QA) in diagnostic radiology is commonly meant to imply testing X ray equipment to evaluate malfunction and that is all. This does not at all lead to quality assurance (QA). QA without consideration of image quality is absolutely NOT QA. The complete quality cycle has to be gone through with feedback mechanism for rectification of malfunction and of operator performance. Any program lacking in attention to totality of the problem will obviously miss the goal and will have peripheral coverage. The emphasis has to be on image quality and patient dose rather than testing equipment performance. Most countries have the potential (with little training) to cover significant step(s) in QA, that is, of evaluating image quality, finding causes for poor quality and thus forming the base for developing a QA program. This step can lead to development of a rational QA program based on the need of the country, which will give emphasis to parameter depending upon its contribution to image quality. Few countries have the capability of directly going over to patient dose assessment and contribute towards guidance level. Most countries need to get initiated into this program and cross the threshold to be able to proceed in the direction of improving the situation and produce results, which can be useful. This requires modular approach such as:

Action recommended:

Phase I. Pilot project: Image quality

  1. Identification of centres. To identify the Hospitals and X ray rooms which will participate in the pilot project. The motivation on the part of radiologist is essential.
  2. Supply of EC image quality criteria to all the centres – May be translated in national language if necessary.
  3. Step 1. Evaluation of base-line data on film retake (at radiographer level) and image quality to be graded as A, B & C (by radiologist) as follows:
  1. Select at least 2 radiography rooms in each hospital. Select two weeks for data collection in (specify the month).
  2. Radiographer to keep daily record of films used and films repeated- to get repeat rate at radiography room and dark room level.
  3. Radiologist to assign A, B, C grade to films (A- clearly accepted without any remark or reservation, B- accepted with some remark/reservations and C- should be rejected. Please estimate the number of films in each category on daily basis for two weeks. (Format of form is given below. May draw number of rows to fill whole page). Please assign the cause for B & C grade film (under/over exposed, artefact, field size misplacement, processing problem).

Date:
Hospital:
Room No.

X-ray/ Patient number Organ/Site/View Image quality grading Cause
A B C
(enter data) (enter data) (grade?) (grade?) (grade?) (enter text)
(enter data) (enter data) (grade?) (grade?) (grade?) (enter text)
(enter data) (enter data) (grade?) (grade?) (grade?) (enter text)

Analysis of daily data separately in every room

Total images (films) =

A = ………….(……….%); B = ………….( ……%); C = ………….(…….%)

Causes for B & C grade films Number of films/ Total no. of films
Over- & underexposure (enter numbers)
Artifacts (enter numbers)
Field size misplacement (enter numbers)
Processing problems (enter numbers)


  1. Step 2. Note the exposure parameters (kVp, mAs, time) used for chest-PA, abdomen LS-AP, LS-Lat, Skull, Pelvic for at least 10 patients for each projection. Measure air kerma under standardised conditions and calculate entrance skin dose using backscatter factor. In case dosimeter for air kerma is not available, available tools (NERO or RadCheck) may be used and air kerma may be estimated either by ensuring calibration of the tool for air kerma or finding calibration factor using calibrated air kerma dosimeter.
  2. Step 3. QC checks on X ray machines in the rooms included in the project for identification of malfunction coupled with rectification/repair of malfunction by the engineer.
  3. Step 4. QC Programme: Staff instructed to improve image quality based on cause analysis resultsas described in step 3, to reduce patient dose by proper adjustment of field size and exposure factors (kVp, mAs, time) and machines should have been repaired.
  4. Step 5. Repeat image quality checks for two weeks in same 2 rooms as above
  5. Step 6. Consolidate data and prepare report to indicate changes in image quality

Phase II. Patient doses and GL

  1. Step a. After step 3 above, perform patient dosimetry using entrance air kerma of X ray unit and then taking into account the exposure factors for selected examinations for average-sized patient 60 kg( Asian) and 70 kg (Western). Estimate ESAK. This will require assistance of physicist.
  2. Step b. Repeat patient dosimetry along with Step 5 above and consolidate data and prepare report to indicate changes in patient doses for selected examinations. Compare results with GLs of BSS.
Phase IAEA’s Inputs Action by Member State

I. Image quality

1. Supply of EC image quality criteria

2. Work plan for retake and image quality

3. Expert’s guidance through email

1. Select few hospitals

2. Collect retake & image quality data

3. Corrective actions followed by repeat assessment

4. Estimate improvement

5. Prepare report and publish

II. Patient dose

1. Supply of dosimeter

2. Quality control tools if not already available

3. Technical assistance

4. Technical documents

5. Fellowship/Scientific visit

6. ESAK calculation software

1. Availability of Medical Physicist to do quality control tests,

   measure output ESAK and compare with GL

2. Report and publish results


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