Topic outline

  • General

    • Welcome to QUALITY ASSURANCE IN DIAGNOSTIC IMAGING/MEDICAL IMAGING!

      We hope you will have a wonderful time and learn a lot about quality assurance and quality control in diagnostic imaging.  We will show basic tests needed in complying the quality assurance in diagnostic imaging department.

      The aim of this course is to provide the student the principles of quality control program applied in Diagnostic Imaging and enable them to implement the quality control test in order to maintain the optimum quality of radiographic images and keep the radiation dose as low as practicable. Quality assurance programs directed at equipment and operator performance can be of great value in improving the diagnostic information, reducing radiation exposure, reducing medical cost and improving departmental management

      Course Information

      • By the end of the course you should be able to:
        • apply the knowledge of quality assurance and quality control in diagnostic imaging and translate the theoretical concepts into practice.
        • perform basic technical procedure of quality control tests using the equipments.
      • Identify and solve the basic problems of QA in diagnostic imaging.


  • Introduction

    • Quality control is specific actions designed to keep measurable aspects of the process involved in manufacturing a product or providing a service within specified limits.

      • These actions typically involve measurement of a process variable, checking the measured value against a limit, and performing corrective action if the limit is exceeded.
      • Quality control is the aspect of quality assurance that monitors technical equipment to maintain quality standards.
      • The concept of quality control is rooted in the need to stabilize the various equipment components of the radiographic imaging chain.


      There are handful of tests to be considered in QC of general x-ray machine.

      For this online course, we demonstrated 3 tests :

      1. kVp accuract test.
      2. exposure reproducibility test.
      3. beam collimation and beam perpendicularity test.

  • Technical QC protocol Handbook

    • EXPOSURE REPRODUCIBILITY TEST

      • X-ray generator should always produce the same intensity of radiation each time the same set of technical factors are used to make an exposure.

        This test is to check the exposure produced for the same mA, time, and kVp is the same from exposure to exposure.

        e.g. 80kVp, 500mA and 0.02s produce 100mR of radiation

        If you make exposures at any future time using the same technical factor/parameter, the exposure produced should be 100mR.

        For this test, we use a multifunction meter or exposure meter / Roentgen meter.



      • EXPOSURE REPRODUCIBILITY TEST RESULT

        formula for result calculation:


        NCRP Report #99 recommends that exposure reproducibility be maintained within ±5% (tolerance limit).


    • BEAM ALIGNMENT AND PERPENDICULARITY

        • BEAM ALIGNMENT AND PERPENDICULARITY

        The area of illumination by the positioning light and the area exposed on radiographs must be the same.

        The collimator is made up of two sets of lead shutters that can be opened and closed, along with a small light bulb mounted on the outer edge and mirror mounted in the center to reflect the light from the bulb through the shutter opening.  The mirror might shift or the mechanism moving the shutters can malfunction that causes the misalignment of light beam.

         

        Proper alignment of the collimator light field with the x-ray field is essential in radiographic quality control because misalignment of light beam and/or improper beam perpendicularity will distort a radiographic image.

        BEAM ALIGNMENT AND PERPENDICULARITY TEST

        The area of illumination by the positioning light and the area exposed on radiographs must be the same.

        The collimator is made up of two sets of lead shutters that can be opened and closed, along with a small light bulb mounted on the outer edge and mirror mounted in the center to reflect the light from the bulb through the shutter opening.  The mirror might shift or the mechanism moving the shutters can malfunction that causes the misalignment of light beam.

        Proper alignment of the collimator light field with the x-ray field is essential in radiographic quality control because misalignment of light beam and/or improper beam perpendicularity will distort a radiographic image.


      • BEAM ALIGNMENT AND PERPENDICULAR TEST RESULT

        STANDARD GUIDANCE:

        Collimation Test:

        According to National Council on Radiation Protection (NCRP), the collimator light to x-ray field light must be within ± 2 % of the SID. At a 100cm SID, the light field should be within ± 2 cm.

         

        Beam Alignment Test:

        For beam alignment, the upper steel ball should be within 5 mm of the lower ball. When the steel balls are positioned over one another and at a right angle to the film, their images will appear as one if the central ray is truly perpendicular to the film (0⁰). If the image of upper steel ball intersects the second ring, the beam is approximately 1.5⁰ away from perpendicular. If the image of upper steel ball intersects the second ring, the beam is approximately 3.0⁰ away from perpendicular. The acceptance level should be less than 2.0⁰.

         

        NOTE:

        • There are few ways to determine the alignment and perpendicularity of x-ray beam.  The older method is using the eight coins, thus named as '8-penny test'. 

    • kVp ACCURACY TEST

      • kVp is the driving FORCE that attracts electrons from the cathode to the anode.

        kVp accuracy is an important contribution in terms of the DENSITY and the CONTRAST on a radiograph.

        kVp quality control test is to determine the accuracy of the TUBE VOLTAGE. To ENSURE that the kVp produced by the x-ray generator is as indicated on the control panel.

        The required kVp accuracy is ±5% or ±5 kVp whichever is the lesser of the indicated value.

         

        you may use kVp meter or multifunction meter to measure.

         


        Multifuntion meter.


      • KVP ACCURACY TEST PROCEDURE.


      • let's discuss! Forum

        let's discuss what is the importance of this test?

        what if the kVp is not accurate?


      • kVp accuracy test result

        Deviation % is calculated using the formula:

         


         

        Average deviation % = (add all readings of deviation %)  ÷ no. of readings

         

        Tolerance limit  is +5% or +5 kV.


    • Topic 6

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