NABL 136 Diagnostic X-Ray QA Testing 2026: Accreditation, AERB Requirements and Test Parameters
Updated: 13 September 2026
Diagnostic X-ray quality assurance is not only an image-quality exercise.
A radiography, CT, mammography, dental or fluoroscopy system has to perform consistently enough to support useful diagnosis while controlling unnecessary radiation exposure.
That means QA testing has to examine both imaging performance and radiation-related parameters.
NABL 136 provides the accreditation framework for facilities that perform this work.
What is NABL 136?
NABL 136 is titled:
Specific Criteria for Accreditation of Quality Assurance Testing Facilities for Diagnostic Radiology X-Ray Equipment.
NABL's current Accreditation Documents register lists:
- Issue: 02
- Issue date: 24 August 2021
- Amendment: 01
- Amendment date: 4 April 2025
NABL announced the amended document on 4 April 2025. It remains the current published NABL 136 version in September 2026.
The document supplements ISO/IEC 17025:2017 with diagnostic-radiology-specific requirements.
What type of work can fall within NABL 136?
The current criteria state that an accredited QA Testing Facility may seek scope for one or more of the following:
- QA testing for type-approval demonstration by a manufacturer or supplier;
- QA testing of X-ray equipment at a manufacturer's premises;
- acceptance testing, including pre-commissioning and post-commissioning situations;
- periodic QA;
- QA after major repair, servicing or maintenance.
This is important because "X-ray QA" can describe several different stages in an equipment life cycle.
Which diagnostic X-ray systems are included?
NABL 136 identifies equipment used in several imaging applications, including:
- fixed radiography;
- mobile radiography;
- portable and hand-held radiography;
- fluoroscopy;
- C-arm and O-arm systems;
- interventional radiology;
- DEXA or bone-density equipment;
- computed tomography;
- dental radiography;
- OPG;
- RVG;
- CBCT;
- mammography;
- X-ray equipment mounted on vehicles;
- other medical diagnostic X-ray equipment where applicable.
The exact accredited scope should identify the equipment categories and QA activities that the facility has demonstrated competently.
NABL accreditation and AERB regulation are different
This distinction is central.
NABL accredits the competence of the QA Testing Facility against ISO/IEC 17025 and NABL 136.
AERB is the competent regulatory authority for radiation safety and regulatory control of diagnostic X-ray facilities in India.
A laboratory can therefore need both:
- technical competence under the applicable NABL accreditation framework;
- compliance with AERB requirements applicable to the equipment, facility or QA activity.
How often is periodic QA required?
AERB's current diagnostic-radiology guidance states that periodic QA of X-ray equipment should be carried out at least once in two years and also after repairs having radiation-safety implications.
AERB's public RTI guidance similarly states that routine QA tests for diagnostic X-ray equipment should be carried out once in two years.
Hospitals and diagnostic centres should still follow the current AERB licence, equipment-specific requirements and any more stringent applicable instruction.
Why QA is more than preventive maintenance
Preventive maintenance asks whether the equipment is operating and serviced.
QA testing asks whether important technical parameters remain within defined performance and safety requirements.
A machine can be mechanically operational while still having unacceptable:
- tube-potential accuracy;
- timer accuracy;
- output reproducibility;
- beam alignment;
- field congruence;
- image quality;
- leakage radiation;
- dose-related performance.
Core QA test parameters
NABL 136 lists example QA parameters that are also reflected in AERB training material.
| QA test | Why it matters |
|---|---|
| Central beam alignment | Checks whether the X-ray beam is correctly aligned with the intended imaging geometry. |
| Radiation and optical field congruence | Checks whether the visible light field accurately represents the radiation field. |
| Effective focal spot size | Supports image-resolution and equipment-performance evaluation. |
| Timer accuracy | Checks whether exposure duration corresponds with the selected value. |
| Accelerating tube-potential accuracy | Checks whether actual kVp corresponds with the selected setting. |
| Linearity of radiation output | Checks output behaviour across relevant loading settings. |
| Reproducibility of radiation output | Checks whether repeated exposures under the same conditions are consistent. |
| Total filtration | Helps assess removal of low-energy radiation that does not contribute efficiently to useful imaging. |
| Tube-housing leakage | Checks radiation leakage around the X-ray tube housing and collimator area. |
| Exposure or dose-rate related test | Assesses radiation output under defined equipment conditions. |
| Image quality | Checks whether the imaging system provides adequate diagnostic performance. |
The actual test set depends on the equipment category and applicable AERB, IEC, IAEA or other recognized protocols.
Why kVp accuracy matters
Tube potential affects both image formation and radiation output.
If the actual kVp differs materially from the selected value, image contrast, beam penetration and patient dose can be affected.
A QA Testing Facility therefore needs a suitable kVp measurement system for the equipment category being tested.
Why timer accuracy matters
Exposure time influences the amount of radiation delivered.
A timing error can contribute to inconsistent image quality or radiation output.
The test should be performed using a suitable controlled method and appropriate QA instrumentation.
Why beam alignment and field congruence matter
The operator positions the patient using visible alignment information.
If the radiation field does not correspond adequately with the optical field, the exposed area may differ from the intended area.
Field congruence and beam-alignment testing therefore connect equipment geometry with radiation protection and image positioning.
Why output reproducibility matters
Repeated exposures under the same selected conditions should produce sufficiently consistent output.
Poor reproducibility can indicate unstable generator or tube behaviour and may lead to inconsistent imaging performance.
QA testing helps distinguish a one-time reading from a repeatable equipment characteristic.
CT QA has additional parameters
Computed tomography requires equipment-specific QA beyond basic radiography tests.
AERB's CT QA format includes parameters such as:
- kVp accuracy;
- timer accuracy;
- output linearity;
- output reproducibility;
- CT dose-index related tests;
- low-contrast resolution;
- high-contrast resolution;
- tube-housing leakage.
The exact applicable tests should follow the current AERB format and equipment configuration.
Mammography needs dedicated QA
Mammography uses lower-energy X-rays and requires strong control of image quality because the target structures can be subtle.
AERB maintains dedicated mammography QA training material and formats.
A facility seeking NABL accreditation for mammography QA should demonstrate the specific tools, methods and competence needed for that modality rather than relying only on general radiography experience.
Dental, OPG and CBCT systems also need modality-specific testing
Dental radiography includes different geometries and operating conditions from general radiography.
NABL 136 includes dental systems such as IOPA, OPG, RVG and CBCT within the possible accreditation scope.
The testing facility should use the appropriate current AERB, IEC or other accepted method for the specific equipment.
What equipment does a QA Testing Facility need?
The exact equipment depends on scope, but QA work can require tools such as:
- kVp meters;
- dosimeters;
- timing equipment;
- low-contrast resolution tools;
- high-contrast resolution tools;
- focal-spot test tools;
- optical and radiation-field congruence tools;
- beam-alignment tools;
- radiation survey meters;
- collimator test tools;
- other modality-specific phantoms and QA devices.
Having the tool is only the first step.
The laboratory also has to control calibration, handling, transport, storage, maintenance and fitness for use.
QA test tools need calibration and traceability
AERB states that prescribed QA test tools used to perform checks need calibration traceable to an acceptable national or international standard.
NABL 136 likewise requires the QA Testing Facility to maintain calibration requirements for QA equipment and comply with metrological-traceability requirements.
This is critical because a QA result is only as strong as the reference equipment used to generate it.
Why site testing needs additional control
Much X-ray QA work is carried out at hospitals, clinics, manufacturer sites or other user locations.
Site work introduces additional variables:
- transport of QA instruments;
- local radiation-safety arrangements;
- equipment availability;
- room layout;
- environmental conditions;
- access permissions;
- coordination with the user facility.
NABL 136 requires test witnessing during assessment at suitable permanent or site facilities for activities under the applied or accredited scope.
Who can perform QA testing?
NABL 136 includes explicit technical-personnel requirements.
It identifies relevant educational backgrounds such as:
- electrical engineering;
- electronics engineering;
- biomedical engineering;
- mechanical engineering;
- medical physics;
- radiological physics;
- science degrees with physics;
- medical imaging technology;
- other equivalent recognized disciplines.
The criteria also specify a minimum of six months' experience or work exposure in medical imaging or diagnostic X-ray equipment testing.
In addition, personnel are required to successfully complete training in QA of diagnostic radiology X-ray equipment from RP&AD, BARC or another equivalent testing facility recognized by AERB.
Technical staff and report authorization
NABL 136 treats personnel who perform QA testing, report results and review reports as technical staff.
The QA Testing Facility should nominate competent personnel who meet the applicable qualification requirements to review, report and authorize results.
This is important because report approval is a technical responsibility, not only an administrative signature.
Why raw data retention matters
The QA report should be reconstructable from the underlying measurements.
NABL 136 requires QA records to include raw data and test reports.
Strong records should make it possible to identify:
- equipment tested;
- equipment serial number or unique identity;
- test date;
- QA test tool used;
- tool calibration status;
- selected X-ray settings;
- raw observations;
- calculated results;
- acceptance criterion;
- person performing the test;
- person reviewing or authorizing the result.
QA after major repair
Repair can alter radiation output or imaging performance.
AERB states that periodic QA should also be carried out after repairs having radiation-safety implications.
NABL 136 likewise includes QA after major repair, servicing or maintenance within its possible scope.
Examples of changes that may justify targeted or broader QA review include work affecting:
- X-ray tube;
- generator;
- collimator;
- detector or imaging chain;
- dose-related systems;
- mechanical alignment.
The exact post-repair tests depend on the nature of the work and current regulatory guidance.
Acceptance testing vs periodic QA
| Acceptance testing | Periodic QA |
|---|---|
| Performed around installation or commissioning to establish whether the equipment meets applicable requirements. | Performed during the equipment life cycle to determine whether important performance parameters remain acceptable. |
| Helps establish baseline performance. | Helps identify deterioration or change over time. |
| May support commissioning and regulatory evidence. | Supports continued safe and reliable operation. |
Type approval testing is another distinct activity
NABL 136 includes QA testing for type-approval demonstration by manufacturers or suppliers.
This should not be confused with routine QA of an individual unit already installed at a hospital.
Type approval relates to demonstrating equipment conformity for a defined model or regulatory process.
Periodic QA evaluates an installed unit during its operating life.
Why image quality and dose have to be considered together
A very low radiation exposure is not useful if the resulting image cannot support the clinical task.
At the same time, increasing exposure unnecessarily is not acceptable merely to create a cleaner image.
AERB's QA training describes the purpose of the programme as supporting diagnostic accuracy while keeping radiation exposure appropriately controlled.
QA therefore aims at stable, suitable equipment performance rather than simply minimizing one parameter.
A practical accreditation-readiness checklist
- Obtain the current NABL 136.
- Define the exact X-ray modalities requested in scope.
- Identify all applicable AERB and technical protocols.
- Maintain qualified and trained technical personnel.
- Maintain calibrated QA test equipment.
- Document equipment transport and site-testing controls.
- Verify test methods and calculation sheets.
- Retain raw measurement data and final reports.
- Control report review and authorization.
- Prepare suitable sites for test witnessing during NABL assessment.
- Maintain radiation-safety arrangements applicable to the testing activity.
- Monitor current AERB and NABL revisions.
What should hospitals verify before accepting a QA report?
- Is the QA Testing Facility currently accredited for the relevant activity?
- Is the exact modality included in the accredited scope?
- Does the report identify the equipment tested?
- Are the required QA parameters included?
- Are the QA instruments traceably calibrated?
- Is the report reviewed and authorized by competent personnel?
- Does the report clearly state any nonconforming parameter?
- Does the facility also meet current AERB regulatory requirements?
Common mistakes
- Confusing NABL accreditation with AERB facility licensing.
- Using QA tools with expired calibration.
- Applying one generic QA checklist to every X-ray modality.
- Performing only image-quality tests while ignoring radiation-output parameters.
- Keeping only the final report without raw measurements.
- Allowing unqualified personnel to authorize reports.
- Assuming preventive maintenance replaces periodic QA.
- Ignoring QA after major repair.
- Claiming accreditation outside the actual approved scope.
Why this niche matters
India has a large installed base of diagnostic X-ray systems across hospitals, diagnostic centres, dental clinics, mobile facilities and specialty imaging centres.
Every system needs controlled performance over its life cycle.
NABL 136 creates a competence framework for the organizations that measure that performance.
The opportunity is therefore not simply "X-ray servicing."
It is a specialized testing activity combining:
- radiation physics;
- measurement;
- image-quality evaluation;
- equipment safety;
- traceability;
- regulatory compliance;
- ISO/IEC 17025 laboratory competence.
That makes diagnostic X-ray QA one of the clearest examples of metrology directly supporting patient safety and clinical reliability.
Frequently asked questions
What is NABL 136?
NABL 136 is the Specific Criteria for Accreditation of Quality Assurance Testing Facilities for Diagnostic Radiology X-Ray Equipment. The current NABL register lists Issue 02 with Amendment 01 dated 4 April 2025.
How often should diagnostic X-ray equipment undergo QA testing?
AERB currently states that routine periodic QA of diagnostic X-ray equipment should be performed at least once every two years and also after repairs having radiation-safety implications.
Which equipment can be covered under NABL 136?
The criteria include radiography, fluoroscopy, C-arm, O-arm, interventional radiology, DEXA, CT, dental radiography, OPG, RVG, CBCT, mammography and other medical diagnostic X-ray systems within the approved scope.
Does NABL accreditation replace AERB approval?
No. NABL accreditation demonstrates competence of the QA Testing Facility for its approved scope. AERB separately regulates radiation safety, diagnostic X-ray facilities and associated regulatory requirements.
Do X-ray QA test tools need calibration?
Yes. AERB states that prescribed QA tools used for testing require calibration traceable to an acceptable national or international standard, and NABL 136 requires control of calibration and metrological traceability for QA equipment.
Does ISO/IEC 17025 apply to X-ray QA testing facilities?
Yes. NABL 136 supplements ISO/IEC 17025:2017 with sector-specific requirements for diagnostic radiology QA testing facilities.
Sources checked
- NABL: Accreditation Documents register . The current register lists NABL 136, Issue 02, Amendment 01 dated 4 April 2025.
- NABL 136: Specific Criteria for Accreditation of Quality Assurance Testing Facilities for Diagnostic Radiology X-Ray Equipment .
- AERB: Regulatory Requirements and Guidelines for Upcoming Radiology Facility . The current guidance states that periodic QA should be performed at least once in two years and after repairs with radiation-safety implications.
- AERB: Diagnostic Radiology resources and QA formats .
- AERB: Quality Assurance Tests for Diagnostic X-ray Equipment .
Editorial note: Radiation-safety regulations, QA protocols and accreditation criteria can change. This article explains official public NABL and AERB information available as of 13 September 2026. QA Testing Facilities and diagnostic X-ray users should use the current NABL 136, current AERB requirements, applicable equipment-specific QA formats and current regulatory licences or approvals when making compliance decisions.
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