Basic quality control tests in medical radiography Finals Topics.

Basic quality control tests in medical radiography

Finals Topics

-DARKROOM QUALITY CONTROL

-QUALITY CONTROL FOR X-RAY EQUIPMENT AND ACCESSORIES

DARKROOM QUALITY CONTROL

FilmsDetermination of the Optimum Developing

TimeCheck for the consistency of the

generator outputCheck for mAs linearityCheck for Timer Accuracy

QUALITY CONTROL FOR X-RAY EQUIPMENT AND ACCESSORIES

Collimator CheckCheck for Alignment of the X-ray Tube

Column and the X-ray TableTest for GridsTest for Bucky MovementTest for Lead Rubber Aprons and Gloves

DARKROOM QC

FILMS

Checking for: - Expiry date * “FIFO” method should be observed

- Storage conditions * temperature at about 20-25 C * away from sources of heat and where chemical vapors may leak and fog the film * boxes of films should not be stored on the floor; should be stacked vertically to avoid pressure marks

DARKROOM QC

DETERMINATION OF THE OPTIMUM DEVELOPING TIME

Objective - To determine the developing time that will give the film’s

maximum density without an increase in base + fog.

Procedure - Expose the loaded cassette in strips (6 strips) using the lowest

kVp and mAs setting at 100cm SID. The exposure factors may be adjusted until we are able to produce a density of 1.0 on the middle strip. The last strip is not exposed to radiation.

5 exposures

4 exposures

3 exposures

2 exposures

1 exposure

No exposure

PRODUCTION OF SENSITOMETRIC STRIPSX-ray film

Lead sheet

Cut into a number of strips

DARKROOM QC


Procedure - Inside the darkroom, cut the film into strips and process them

using different developing times, e.g. 30s, 60s, 90s, 120s, 150s & 180s.

DARKROOM QC


Evaluation - Examine the film strips, look at the middle step and determine which strip exhibit the maximum density at an acceptable basic fog. The time used to develop this strip is considered the optimum developing time.

1(30s)

2(60s)

3(90s)

4(120s)

5(150s)

6(180s)

QC FOR X-RAY EQUIPMENT AND ACCESSORIES

CHECK FOR THE CONSISTENCY OF THE GENERATOR OUTPUT

Objective - To determine whether the generator produces the same

density every time the same exposure factors are selected.

Procedure - Position the water phantom on the loaded cassette and expose

the film with set factors. Process the film the usual way.


CHECK FOR THE CONSISTENCY OF THE GENERATOR OUTPUT

10cm H2O

Exposure 1

10cm H2O

Exposure 2

10cm H2O 10cm H2O

Exposure 1 Exposure 2

A. Consistent generator output B. Inconsistent generator output


CHECK FOR mAs LINEARITY

Objective - To determine any differences in photographic density when

different mA settings are used for equal mAs value.

Procedure - Position the water phantom on the loaded cassette and expose

the film with set factors. Process the film the usual way.



10cm H2O

Exposure 150mA & 0.2s

10cm H2O 10cm H2O



GoodLinearity



10cm H2O


10cm H2O 10cm H2O



PoorLinearity


CHECK FOR TIMER ACCURACY

Objective - To determine the accuracy of the x-ray timer.

Procedure - Position the spinning top on the loaded cassette and expose

the film using the clinically used exposure times. Process the film the usual way.





For mains supply with 60Hz frequency:

1. One-pulse (self rectified) unit Set time (sec) No. of dots 0.05 3 0.10 6 0.50 30 1.00 602. Two-pulse (full wave rectified) unit Set time (sec) No. of dots 0.05 6 0.10 12 0.50 60 1.00 120


COLLIMATOR CHECK

Objective - To check if the radiation field is the same as the area illuminated by the light from the collimator.

Procedure - Center the loaded cassette in the useful beam at a commonly

used SID. Collimate the field to approximately half the film’s size and place a metal marker at the center of the illuminated area and mark the inside edges with lead wires. Make an exposure using appropriate technique factors. Make a second exposure with the collimator fully opened. Process the film the usual way.


COLLIMATOR CHECK

1st exposure

2nd exposure


COLLIMATOR CHECK

Radiation field

Light field

The misalignment should not exceed 2% of the SID


CHECK FOR THE ALIGNMENT OF THE X-RAY TUBE COLUMN AND THE X-RAY TABLE• Check for table alignment with the x-ray beam


CHECK FOR THE ALIGNMENT OF THE X-RAY TUBE COLUMN AND THE X-RAY TABLE

• Check whether the column is vertical - Using a plumb bob, hold the string’s end against the tube column making sure that the string hangs unobstructed. If the column is parallel to the string, the column is vertical.

• Check whether the table top is horizontal - Place a bowl of water on top of the table at different locations and measure the depth of water around the edge of the bowl. If the table is horizontal, the depth of the water will not vary across the bowl.

• Check whether the horizontal arm is still horizontal - Measure the distance between the cross-arm and the table top in front of the cross-arm and from the back. The arm is horizontal if the distance is the same from both ends.


TEST FOR GRIDS

Objective - To check whether the grid gives a uniform density over its area.

Procedure - Place the loaded cassette on the cassette tray or under the

loose stationary grid. Place metal markers on the cassette to indicate the position of the grid on the film. Expose the film using the recommended SID and process the film the usual way.


TEST FOR BUCKY MOVEMENT

Objective - To check whether the grid bucky is moving throughout the whole exposure.

Procedure - Place the loaded cassette on the cassette tray. Place metal

markers on the cassette to indicate the position of the grid on the film. Expose the film in the bucky mode and process the film the usual way. Check for presence of grid lines on the radiograph.


LEAD RUBBER APRONS AND GLOVESCare

-clean with soap and water, weekly or as necessary -should not be stored near a heat source -aprons should be hung up using hangers; should not be fold -gloves should be stored flat or upright on a custom holder

Checking for damage

-to surface covering, seams and fasteners of aprons (if any) -check for flexibility, feeling for cracks


LEAD RUBBER APRONS AND GLOVESTest to detect cracks on aprons and gloves Method

-place the apron or gloves to be tested on the table top -use fluoroscopy system to examine the whole article *if radiography is to be used, placed cassettes under test articles and make separate exposures, ensuring that the whole article is examined

Evaluation

-Look for cracks or other abnormal variations of density in the

image

Basic quality control tests in medical radiography Finals Topics.

Documents

s exposure

accessories slide

accessories check

xray equipment

h2o exposure

s good linearity slide

optimum developing time

exposure factors