Quality Assurance

Quality assurance is a series of planned and systematic actions necessary to provide adequate confidence that a piece of hospital equipment will meet the requirements for quality. It involves providing a list of equipment capabilities, acceptance testing after purchase, commissioning by the site physicist and ongoing quality control tests.

Quality control for hospital equipment plays a role in improving the diagnostic quality, reducing dose, reducing medical costs and improving departmental management. Thus, QA programs contribute to the delivery of high quality health care.

Quality assurance helps to:

  • Prevent accidents or errors
  • Increase the chance that an accident or error will be detected prior to incidence
  • Reduce uncertainties
  • Provide reliable inter comparison between centres
  • Provide full exploitation of improved technology and more complex treatments in radiology and radiotherapy
In radiotherapy, quality assurance programs are of particular importance because dose delivered to tumours and surrounding healthy tissue must be accurate. Only with rigorous QA can this be consistent for all patients.

Testing

Acceptance testing is done by the supplier immediately after purchase, to demonstrate the baseline performance of the equipment to the satisfaction of the buyer. This baseline performance must encompass essential aspects of equipment operation, e.g. baseline running parameters, safety etc. The equipment is only accepted when the customer is satisfied. 

Commissioning is undergone by the site physicist to fully characterise the equipment before clinical use begins. It tests the equipment in a range of different clinical tasks, e.g. preparation of procedures, protocols, instructions, data etc. Clinical use can only begin when the physicist responsible for commissioning is satisfied.

Acceptance testing and commissioning can partially overlap. They will together establish the baseline performance requirements the equipment must meet in follow up monthly and annual check. They establish the requirements upon which future testing will be referred.

Taking Action
  • If the measurement falls within the tolerance level, no action is required
  • If the measurement exceeds the action level, immediate action is required
  • If the measurement falls in between the tolerance and action levels, this may be considered acceptable until the next day measurement
  • If the measurement falls consistently between the tolerance and action levels, adjustment is required.
Monthly and Annual Quality Control Tests for a Linac (with tolerance level)

Monthly
  • X-ray output constancy, 2%
  • X-ray beam flatness constancy, 2%
  • Back up monitor constancy, 2%
  • Wedge position, 2% or 2mm
Annual
  • X-ray output calibration constancy, 2%
  • Off-axis factor constancy, 2%
  • Wedge transmission factor constancy, 2%
  • Central axis parameter constancy, 2%

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