Quality Assurance/Quality Control

chapter 10 Quality Assurance/Quality Control



Susan L. McClanahan



CHAPTER OUTLINE


Quality Assurance/Quality Control in Veterinary Radiography


OBJECTIVES


Upon completion of this chapter, the reader should be able to do the following:


• Define quality assurance

• Define quality control

• Understand the reasons for quality assurance/quality control

• Describe the various quality control tests

• List the equipment necessary to complete the quality control tests

• Describe how to interpret the results of the quality control tests

• Describe how to keep the necessary records to track the results of the quality control tests

• Understand when to call for service personnel to correct a problem


GLOSSARY


Quality assurance: A system of activities, the purpose of which is to provide assurance that overall quality control is being done effectively. The system involves continuing education on the adequacy and effectiveness of the overall quality control program and initiates corrective measures where necessary.


Quality control: The overall system of activities, the purpose of which is to provide a quality product or service that meets the needs of the users. The aim of quality control is to provide quality that is satisfactory, adequate, dependable, and economic.



INTRODUCTION


Quality assurance is an area that has become more recognized by the medical industry as a necessary tool for overall control of diagnostic radiographs. Quality assurance is defined as follows:




A system of activities whose purpose is to provide assurance that the overall quality control job is in fact being done effectively. The system involves a continuing evaluation of the adequacy and effectiveness of the overall quality control program with a view to having corrective measures initiated where necessary (Thomas, 1973).


The activities of a quality assurance program are numerous including (1) preventive maintenance, (2) quality control, (3) equipment calibration, (4) in-service education of the personnel responsible for radiography, and (5) other items such as the evaluation of new products.




Quality control, being just one aspect of the quality assurance program, is defined as the overall system of activities whose purpose is to provide a quality of product or service that meets the needs of the users; also the use of such a system. The aim of quality control is to provide quality that is satisfactory, adequate, dependable and economic (Thomas, 1973).


If the quality assurance program is the “umbrella” or management portion, then the quality control segment covers the integrity and function of the equipment and the measurement of image quality (Fig. 10-1).


image

Figure 10-1 Umbrella of quality assurance/quality control.


The purpose of a quality assurance/quality control (QA/QC) program is threefold. First, it provides a way to minimize the dose of radiation not only to the patient but also to the persons who are assisting with the radiograph. Second, it allows production of quality radiographs that provide information for an accurate diagnosis. Third, its use leads to a decreased number of repeated films and thereby reduces overall cost per examination.



QUALITY ASSURANCE/QUALITY CONTROL IN VETERINARY RADIOGRAPHY


Questions have been raised regarding the validity of a quality assurance program and quality control tests in a veterinary practice. The basis for these questions has been that the patients being radiographed are not human, and therefore the question of repeated radiographs and unnecessary radiation becomes moot. However, the consideration should be for the persons assisting in positioning the animal or otherwise involved with the procedure during the radiographic exposure. The issue is not whether the patient is human but the protection of any involved personnel from unnecessary ionizing radiation.


A veterinary technician is an important part of any quality assurance program. It is the technician’s job to do most of the quality control tests, interpret the data, and keep the records. The remainder of this chapter addresses these tests, their interpretation, and the records that should be kept.


For these quality control tests, the data gathered are objective. We are not dealing with opinions or personal preferences of contrast and image quality. The technician measures, plots, and analyzes the data. This information is gathered at a point that is not yet visible to the eye on the radiograph.



Equipment


The actual equipment used to perform quality control testing depends on the size of the facility or practice. For a small facility, the equipment listed following is sufficient for an informative quality control testing protocol.


These items should be stored within easy access—and together—to eliminate confusion and delay when it is time to conduct the tests. Most of these tests are done only annually; if this is not the case, it is noted in the test procedure.



Tracking Charts


The purpose of tracking charts is to provide a means to record the data for ease in interpretation and tracking of results. There is no right or wrong way to keep this information except for the sensitometry/densitometry tests. The charts that the technician makes and relies on for tracking the equipment parameters are the mainstay of the quality assurance program. With charting, it is easy to inspect the data from the measurements and assess any changes. Changes that do occur can be brought to the attention of the veterinarian before they cause a problem that necessitates a second radiograph. When the charts indicate to the technician that the control limits have been reached or exceeded, action should be taken immediately.



Procedures


The procedures for using the test equipment are described in detail with each test. The following tests can be conducted frequently, as they are easy to do and provide the practice with a quick look at the physical nature of the radiographic equipment and the environment.



Equipment Needed



Graph paper or commercially prepared tracking charts

Pencil and ruler

Notebook or folder for retention of tracking charts

Sensitometer

Densitometer

Thermometer

Nine pennies

Tape measure

Carpenter’s level

Screen-film contact mesh

Simple instructions for use and interpretation



QA/QC TESTS FOR THE X-RAY APPARATUS



SOURCE-IMAGE DISTANCE (SID) MARKS



Equipment Needed


Tape measure


Carpenter’s level



Objective


To ensure the accuracy of the SID



Procedure



1. Using a steel measuring tape, measure from the focal spot mark on the tube housing to the tabletop. If there is no mark on the tube housing, simply divide the tube housing end cap into fourths. Using the bottom fourth as the focal spot, mark this on the end cap with a permanent marker and proceed with the measurement.

2. Measure from the tabletop to the top of the cassette in the Bucky tray.

3. Add these two numbers. They should equal the SID that is marked (Fig. 10-2).

4. Measure the marks on the tube stand for accuracy as well. Replace any “missing” marks with permanent marker, nail polish, or paint. If the collimator has a tape measure on it, check this for accuracy with the external tape measure. This information should be recorded for comparison and included in the quality control tests notebook or file.

image

Figure 10-2 A, With a tape measure, the source-image distance (SID) from the focal spot of the x-ray tube to the table is measured and recorded. B, With the same tape measure, the distance from the tabletop to the top of a cassette placed in the Bucky tray is measured. The two measurements are added and should match the SID marked on the tube stand.




QA/QC TESTS FOR THE X-RAY APPARATUS



PERPENDICULARITY



Equipment Needed


Carpenter’s level



Objective


To ensure that the x-ray beam is properly centered, we must be sure that the tube stand, collimator, and x-ray tube are perpendicular and properly aligned.



Procedure



1. When the x-ray tube is positioned in the normal position, use the level to confirm that the tube is level and parallel with the table (Fig. 10-3). Stand at the end of the table and look at the tube, collimator, and tube stand. Visually verify that they appear to be perpendicular.

2. Stand alongside the table and verify the same information regarding perpendicularity of the collimator, x-ray tube, and tube stand.

3. If the tube, the collimator, or the tube stand looks crooked or canted, adjust it or have it repaired before attempting any alignment tests or taking any radiographs. This information should be recorded along with whether the test was negative, what was canted, and how it was corrected. If the equipment was serviced, the repair report should be kept for future reference. The information should be recorded for comparison.

image

Figure 10-3 Perpendicularity. A level is used to ensure that the x-ray tube is level and parallel to the tabletop.




QA/QC TESTS FOR THE X-RAY APPARATUS



TUBE/TABLE/CRANE LOCKS



Equipment Needed


None



Objective


To check the function of the locks to eliminate any unnecessary motion from the x-ray tube, table, or crane.



Procedure



1. Physically place locks on and off to see whether they lock securely and unlock properly.

2. Check to make sure that the lock switch itself is not broken and that it functions properly. This should be recorded for future reference.



QA/QC TESTS FOR THE X-RAY APPARATUS



X-RAY FIELD LIGHT



Equipment Needed


Water and cloth



Objective


To ensure that the field light can be seen properly with the normal lights on in the radiographic room.



Procedure



1. Turn off the power to the machine. Wash the plastic covering of the x-ray collimator with warm water and mild soap. The plastic covering over the tube output area should be clean and free of debris and dirt. If not, artifacts can show up on the radiograph. (Note: On some older equipment, the plastic covering may be part of the filtering of the x-ray beam. If this is the case, do not damage or remove it without having a serviceperson correct the filtration on the equipment.)

2. Turn on the power to the machine. To check the brightness of the light, leave room lights on and turn on the collimator light. If there is no difficulty in seeing the edges of the field, there is no problem.

3. If the dimensions of the light field are difficult to see, there is a problem. A serviceperson should be called to increase the light intensity, and a record should be made for future comparison and reference.



QA/QC TESTS FOR THE X-RAY APPARATUS



LIGHT FIELD SIZE



Equipment Needed


Steel tape measure



Objective


To ensure that the light field determined by the collimator dials is accurate.



Procedure



1. Using the tape measure, verify the SID to the tabletop.

2. Set the collimator size indications at some field size. Remember to use the score for the SID you use routinely. An example of a field size to use is 8 × 10 inches (Fig. 10-4).

3. Turn on the collimator light.

4. Using the tape measure, measure the light field on the tabletop. This measurement should be within 2% of the SID for light field accuracy. This should be recorded for future comparison and reference.

Related posts:

  1. Radiographic Technique Evaluation
  2. Developing a Technique Chart
  3. Anatomy of the X-ray Machine
  4. Small Animal Forelimb

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May 27, 2016 | Posted by in ANIMAL RADIOLOGY | Comments Off on Quality Assurance/Quality Control

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