Medical X-ray equipment does not degrade all at once. It drifts — imperceptibly, gradually, often invisibly to clinical users — until one day the images are subtly but consistently worse than they should be, or the radiation doses are higher than necessary to produce a diagnostic image. Quality Control (QC) testing exists to catch this drift before it affects patients. In the UAE, FANR requires QC testing at acceptance, after repair, and as part of the annual compliance review. This article explains what QC tests are performed, what they measure, and what the results mean for your facility.
Medical X-ray Quality Control is a systematic programme of measurements and assessments designed to verify that an X-ray system is operating within its specified performance parameters. The goal is to ensure that the system consistently delivers the diagnostic image quality it was designed to produce, at the radiation dose it was specified to use.
QC is distinct from routine maintenance. PPM checks mechanical and electrical condition. QC measures actual performance — how much radiation the tube is producing, whether the kVp is accurate, whether the image quality meets diagnostic standards.
The following tests form the core QC programme for a standard diagnostic X-ray system:
kVp (peak kilovoltage) accuracy: The kVp controls the energy of the X-ray beam — and therefore the beam's penetrating power and the contrast in the resulting image. A kVp that reads 70 on the control panel but actually delivers 66 or 74 kVp produces systematically different images than intended. Acceptance limits are typically ±5% of the stated value.
mAs (milliampere-second) linearity: The mAs controls the quantity of radiation produced. If mAs linearity is poor, identical mAs settings produce different doses in different exposures — unpredictable image brightness and variable patient dose.
Half-Value Layer (HVL): The HVL measures the penetrating quality of the X-ray beam and is used to assess beam filtration. Inadequate beam filtration means unnecessary low-energy X-rays are delivered to the patient without contributing to the image.
Radiation output (dose) measurement: The dose produced per mAs at a standard kVp and distance is measured. This confirms the generator and tube are functioning correctly and provides the baseline for patient dose optimisation.
AEC (Automatic Exposure Control) performance: Most modern X-ray systems use AEC to automatically terminate the exposure when sufficient radiation has reached the detector. AEC performance tests check that the system consistently terminates at the correct exposure level across different phantom thicknesses — the analogue of different patient sizes.
Spatial resolution: The system's ability to resolve fine detail is assessed using a resolution test pattern or line pair gauge. Resolution decline indicates detector degradation or focus drift.
Low-contrast detectability: The ability to distinguish subtle differences in tissue density — critical for diagnostic imaging — is assessed using a low-contrast test object. This measurement catches system changes that do not affect resolution but reduce the ability to detect subtle lesions.
CT scanners require all of the above tests plus additional CT-specific measurements:
CTDI (Computed Tomography Dose Index): The radiation dose per CT scan is measured using a pencil ionisation chamber inside a CTDI phantom. This measurement must be within ±20% of the manufacturer's stated value and must be used to set the facility's dose reference levels.
Slice thickness accuracy: The actual reconstructed slice thickness must match the nominal value.
CT number accuracy: Hounsfield unit values for standard materials (air, water, acrylic) must be within ±5 HU of expected values.
Image uniformity: CT number uniformity across the field of view must be within ±5 HU.
Noise: Image noise at the facility's standard scan parameters must be within the manufacturer's specification.
Mammography QC is more stringent than any other imaging modality because mammography is used to detect very small, low-contrast lesions — early-stage breast cancers — in a radiation-sensitive population. UAE facilities offering mammography should implement the full EUREF (European Reference Organisation for Quality Assured Breast Screening) QC programme, which includes daily, weekly, monthly and annual tests performed by a combination of the radiographer and a medical physicist.
Acceptance testing: Before any new X-ray system is used clinically, a full QC assessment must be performed to verify the equipment was installed correctly and is performing to specification. This is a FANR requirement.
After significant repair: Any repair that could affect radiation output, beam geometry or image quality requires QC testing before the equipment returns to clinical use. This includes X-ray tube replacement, generator servicing, detector replacement and collimator adjustment.
Annual QC review: All X-ray equipment in UAE healthcare facilities must undergo annual QC testing as part of the FANR compliance programme. The QC report is required for FANR licence renewal.
Whenever clinical concern arises: If clinical staff notice changes in image quality, equipment behaviour or patient positioning requirements, QC testing should be performed immediately rather than waiting for the next scheduled test.
FANR requires QC testing to be performed by or under the supervision of a qualified medical physicist. The physicist must have recognised qualifications in medical physics and sufficient experience with the specific equipment type. All QC measurements must be performed with instruments that are calibrated and traceable to national standards.
A full QC assessment for a single digital X-ray unit takes approximately 2–3 hours. A CT scanner QC assessment takes 4–6 hours. RevirzaMed schedules QC visits to minimise disruption to the clinical workload.
Some daily and weekly QC checks can be performed by trained radiographers using appropriate test tools. Annual QC assessments and acceptance testing must be performed by a qualified medical physicist with calibrated instruments.
If equipment fails a QC test, it should not be used for diagnostic imaging until the fault is identified and corrected. RevirzaMed's physicists provide a detailed report identifying which parameters failed and by how much, and advise on the corrective action required.
RevirzaMed Healthcare Solutions — Abu Dhabi's trusted FANR Approval and medical equipment specialists since 2015.