1 Quality Control Rad T 110. 2 Aim : The purpose of QC to achieve high quality images with the least amount of radiation. The purpose of QC to achieve

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Quality ControlQuality Control

Rad T 110Rad T 110

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Aim :Aim :

The purpose of QC to achieve high The purpose of QC to achieve high quality images with the least amount of quality images with the least amount of radiation.radiation.

Quality Control is a part of Quality Quality Control is a part of Quality Assurance programAssurance program

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Test Types:Test Types:

Acceptance testAcceptance test Monitoring testMonitoring test Annual Test Annual Test After repair or tube After repair or tube

replacementreplacement

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Acceptance Test:Acceptance Test:

Performed upon newly Performed upon newly installed equipment installed equipment to verify purchase to verify purchase specification and to specification and to establish performance establish performance base line.base line.

Frequency:Frequency:• To be performed To be performed

once only when once only when new machine is new machine is installedinstalled

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Monitoring Test:Monitoring Test:

Performed for vital Performed for vital parameter on parameter on routine basis. routine basis.

Frequency:Frequency:• Every 2-3 monthsEvery 2-3 months

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Annual Test:Annual Test:

Performed for Performed for vital parameter vital parameter

Frequency:Frequency:• once a yearonce a year

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Parameters to be checkedParameters to be checked

1.1. Beam Alignment and Collimator AccuracyBeam Alignment and Collimator Accuracy

2.2. Radiation output and linearity of mR/mAs Radiation output and linearity of mR/mAs versus kVversus kV (Large and small FS(Large and small FS

3.3. Assessment of Total Beam Filtration (HVL)Assessment of Total Beam Filtration (HVL)

4.4. Assessment of Focal Spot size Assessment of Focal Spot size

5.5. Accuracy and constancy of Exposure TimerAccuracy and constancy of Exposure Timer

6.6. Measuring of Scattered Radiation (using Measuring of Scattered Radiation (using Water Phantom)Water Phantom)

7.7. Leakage Radiation from X-Ray tubeLeakage Radiation from X-Ray tube

1-5 Monitoring test, 2- Annual Test

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1. Beam Alignment and Collimator Accuracy1. Beam Alignment and Collimator Accuracy

Beam Alignment Test Tool

Small hole

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X-ray TubeX-ray Tube

Test ToolTest Tool

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Improper central ray alignment will distort a Improper central ray alignment will distort a radiographic image. radiographic image.

When used with the Collimator Test Tool, this device When used with the Collimator Test Tool, this device provides a simple means of determining if the X-ray provides a simple means of determining if the X-ray beam is perpendicular to the image receptor and beam is perpendicular to the image receptor and centered with respect to the light field.centered with respect to the light field.

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2. Constancy of Radiation output and linearity of mR/mAs 2. Constancy of Radiation output and linearity of mR/mAs versus kVversus kV2 2 (Small & Large focus) (Small & Large focus)

Victoreen Kv Meter

Displays kVp maximum, kVp average, kVp effective, dose and time

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Parameters to be checkedParameters to be checked2.2. Constancy of Radiation output and linearity of mR/mAs versus kVConstancy of Radiation output and linearity of mR/mAs versus kV2 2 (Small & Large focus) (Small & Large focus)Set mAs=20 for LF & 10 for SFSet mAs=20 for LF & 10 for SF


Table top Table top

Measure kVp & Output

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Radiation output and linearity of mR/mAs versus kVRadiation output and linearity of mR/mAs versus kV

•The mR/mAs relationship must be linear and acceptable

•kVp measured by the kV Meter must be within the acceptable range ( i.e. + 10% of kVp indicated by machine)

•The exposure dose (Output) must be within acceptable limits .

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3. Assessment of Total Beam Filtration / (HVL) 3. Assessment of Total Beam Filtration / (HVL)

HVL(Half Value Layer): is the most frequently used factor for describing both the penetrating ability and the penetration through specific objects.

Defined: thickness of material penetrated by one half of the radiation

Unit: mm or cm

Filtration: attenuation of photon according to their Energy ( simply the ability to get rid of unnecessary radiation)

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3. Assessment of Total Beam Filtration (HVL) 3. Assessment of Total Beam Filtration (HVL)

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Table top Table top

Measure Output only

Put Aluminum Shield with

different thickness 1,2,3,4

mm

Put Aluminum Shield with

different thickness 1,2,3,4

mm

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AL mm Output (+ 2)Xi/X2

0 112.1

1 83

2 65.2

3 57.1

4 49.1 0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

1.10

0 1 2 3 4 5Al mm

x/xi

HVL=3.0 mm (acceptable limit > 2.5 mm Al)

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4. Assessment of Focal Spot size4. Assessment of Focal Spot size

Focal Spot area: is the surface area of the anode that is bombarded by electron beam.

For Radiography units from 0.6 to 2.0 mm

For Mammo units 0.3 –to 0.6

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Focal Spot Test Tool

Fine Parallel line

2121

CouchCouch




Low Speed film

Low Speed film

Test Tool60 cm from

the tube

Test Tool60 cm from

the tube

Focal Spot Area( level)Focal Spot Area( level)

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• A small focal spot size is used to obtain x-ray image with minimum blur.

•Small focal spot tend to concentrates heat and gives load on focal spot area.

•If the quantity of heat delivered during an individual exposure exceeds the track capacity, the anode surface can melt.

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• so … it is necessary to measure the focal spot size and compare it with the original focal spot size with the machine.

•Focal spot size of any machine is written on the top of X-ray Tube.

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5. Accuracy and constancy of Exposure Timer5. Accuracy and constancy of Exposure Timer


Table top Table top

Measure the time compare it with time of exposure from the machine

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6. 6. Measuring of Scattered Radiation (using Water Measuring of Scattered Radiation (using Water Phantom)Phantom)

When x-ray beam or gamma radiation passes through an object it can either

1. Penetrate the object without interacting

2. It can interact with matter and be completely absorbed.

3. It can interact and scattered or deflected from original direction.

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6. 6. Measuring of Scattered Radiation (using Water Measuring of Scattered Radiation (using Water Phantom)Phantom)

X-r

ay T

ube

X-r

ay T

ube

Water or Chest

Phantom

X-ray Chest Bucky

Ionization Chamber 1 m from center

Ionization chamber

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7. 7. Leakage Radiation from X-Ray tubeLeakage Radiation from X-Ray tube

Rarely done.Rarely done. Typically for very old units.Typically for very old units. To test if there is any leakage of radiation from the x-ray tube. To test if there is any leakage of radiation from the x-ray tube.

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Fluoroscopic Unhappiness and spatial ResolutionFluoroscopic Unhappiness and spatial Resolution


•The test pattern should be placed on the input window of the II and oriented so that the bar patterns are imaged perpendicular to the raster lines of the monitor display.

Documents

1 Quality Control Rad T 110. 2 Aim : The purpose of QC to achieve high quality images with the least amount of radiation. The purpose of QC to achieve