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X-Ray Calibration 101: Ensure Your Machine’s Accuracy with These Checks

Updated: Jun 21

Proper X-ray calibration is one of the things the Philippine Food and Drug Administration (FDA) requires when processing the license to operate (LTO) of medical X-ray facilities. Proof of this test is strictly needed to ensure the safety and quality of the equipment for efficient patient diagnosis.


Securing the FDA’s LTO for your own facility? Here’s everything you need to know about X-ray calibration.


What is X-ray calibration?


An X-ray calibration service, simply put, measures the accuracy of your X-ray equipment. Meticulous checks are done to test whether the mechanical installation is correct and to see if the electrical components of the unit are working properly.


X-ray calibration is one of the requirements in obtaining the FDA’s license to operate a medical x-ray facility.


Are X-ray calibrations really necessary?


Apart from being required by the FDA for first-time and renewal applicants, it’s important that you don’t forgo proper calibration of your unit. It is through these tests that you see that your equipment is performing at its peak. Furthermore, by showing potential issues with your unit prior to your facility’s operation, X-ray calibrations help you address safety hazards efficiently.


If your X-ray calibration service is not done properly by your provider, your device might show inaccurate results and ultimately expose the operators and patients to more radiation. With a machine that’s properly calibrated, you can rest assured you’re offering the best quality service for your patients.


What happens during calibration?


X-ray calibration involves a number of rigorous tests. For the calibration report, the FDA requires details on the following:


1. Mechanical checks


A collimator assessment performed with a Collimator Beam Alignment and Perpendicularity Test Tool.

  • Collimator Assessment

Improper collimator beam and X-ray tube alignment will distort radiographic images. To verify the proper alignment of the collimator beam (from X-ray tube) towards both the table bucky and bucky stand/VCH, there are three checks to be performed:



AlignmentThe total misalignment shall be within ±2% of SID. Each side shall be within ±1% of SID. The misalignment between the X-ray field and image receptor shall be within ±1% of the SID.PerpendicularityThe x-ray beam perpendicularity shall be within 1.5 degrees.CenteringThe center of the x-ray beam and the center of the indicator light beam to the center of the image receptor.


2. Generator checks

  • Overload Circuit Protection

During X-ray calibration, the overload circuit protection is checked to see if it is present and functioning properly.




Some of the most important generator checks are performed with a kVp/mAs meter.

  • kVp Accuracy

The peak voltage in kilovolt or kVp is checked to test the radiation quality. A lower kVp means the X-ray beam will penetrate less, resulting in higher contrast in the final radiograph. Meanwhile, a higher kVp will make the beam penetrate more and produce less contrast.


During the calibration, the following standards must be followed:


For 100 kVp and belowThe actual kVp shall be within ±6% of the set kVp. For 101 kVp and aboveThe actual kVp shall be within ±6% of the set kVp.


  • mA Linearity

An increase in mA should also show a linearly proportional increase in X-ray dose measured in microgray (µGy) or millirad (mRd)


X-ray calibration service providers will ensure that the overall coefficient of linearity must be less than or equal to 0.1 as required by the FDA.



X-ray Exposure Time Meters and Dose Meters are also used to ensure the safety of radiographic machines.

  • Exposure Time Accuracy

The time accuracy of the radiographic device is also important as the received radiation of the patient increases the more time they are exposed.


As per the FDA, the actual time shall be within ±10% of the set time. For exposure time of less than 100 milliseconds, the actual time should be ±20%.


What tools are needed for X-ray calibration?


To do the aforementioned checks thoroughly, the following devices are used:

  1. Collimator Beam Alignment and Perpendicularity Test Tool

  2. kVp/mAs Meter

  3. Dosimeter

  4. Exposure Time Meter

  5. Caliper

To be accepted by the FDA when you process your LTO, your X-ray calibration report should note the test tools used, including the model, manufacturer, serial numbers, and the date of calibration of said tools.

Where can you get your X-ray unit calibrated?


While the FDA doesn’t provide accreditation for X-ray calibration service providers, they only approve LTO applications whose calibration reports contain precise data. Your report must contain correct computations and details of the calibration test tools. To prove the test's validity, the FDA will also be requiring photo evidence of the tests performed


Considering all these and the fact that the calibration tests are required every time you apply for an LTO renewal, it’s important to find a calibration service provider you can trust to give an accurate assessment.



Provide accurate service for your patients by having proper X-ray calibration service done regularly.


Find hassle-free calibration services


Make obtaining an LTO for your medical X-ray facility a smoother process with Care 4 Life. Our accurate and complete X-ray calibration service has been recognized by the FDA, helping you meet the regulations required for operation.


With our technical expertise in radiography, we can assure the safety and quality of your radiography systems. Contact us today to learn more about our X-ray calibration service!





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