This document describes a series of tests to assess CR plate and reader performance. The tests are intended to monitor image quality and sensitivity.

All the tests described should be performed on all available reader systems. This document is intended as guidance. For more specific set-up details the local medical physics department should be consulted.

 *Adapted for local need from IPEM document

• List of equipment

• CR1 Sensitivity Index Monitoring

• CR2 Uniformity

• CR3 Threshold Contrast Detail Detectability

• CR4 Limiting spatial resolution

• Test Failure Report:

List of equipment

·        Tape measure

·        Adhesive tape

·        1 mm Copper filtration (>10 x 10 cm)

·        TOR RAD or TOR CDR test object

In all tests described the unique plate identification code should be recorded, and the same tube and generator should be used each time the tests are performed.

 TOR CDR test object

CR1 Sensitivity Index Monitoring
Purpose: To monitor system sensitivity, and consistency of relationship between cassette exposure and sensitivity index.

Frequency: 1 - 3 monthly

a)      Place a cassette (e.g. 24cm x 30cm - the same cassette should be used each time this test is performed) on the couch at 1m from the focus and centred in the x-ray beam. Set the collimation to cover the entire cassette. 

b)      Place filtration in the beam and set a kVp as indicated in below.

c)      Set a manual mAs (this value should be determined in consultation with medical physics) and expose.

d)      Read the plate immediately using the following parameters

Kodak: Pattern mode.

e) Record the sensitivity index, i.e.  

EI - Kodak

Tolerance: This sensitivity index should be compared to a baseline value obtained under the same conditions (i.e. same x-ray tube, distance, kV, filtration, mAs, plate).

Remedial level:

            Kodak: EI should lie between

            (Baseline +80)              and       (Baseline-100)

Suspension level:

            Kodak: EI should lie between

                        (Baseline+175) and       (Baseline-300) 
 

CR1 Sensitivity Index Monitoring Results.

Baseline Data

Date………………………………………

Exposure Index result…………………..

Remedial Levels        (Baseline +80) and       (Baseline-100)

=                                  ….………….                          ………………

Suspension Level       (Baseline+175) and       (Baseline-300)

=                                  ….………….                          ………………

CR2 Uniformity
 

Purpose:  To monitor image quality by assessing the uniformity of the system.

Frequency:  1-3 monthly

a)      Select any cassette (a different cassette should be tested each time this test is performed).

b)      Use as large a focus to detector distance as possible and open the collimators so that the X-ray field covers the entire detector.

c)      Expose the detector at as described for test 1.

d)      Visually inspect the images for non-uniformities.

Note:  Images acquired for the sensitivity index monitoring test should also be inspected for non uniformities.

Remedial level:  Images should not have obvious artefacts.

N.B.  This is a test of the reader. To test the whole system it would be necessary to test several plates at each 1-3 monthly interval
 

CR2 Uniformity Uniformity Results

Results (Frequency:  1-3 monthly )

CR3 Threshold Contrast Detail Detectability

Purpose:  To monitor image quality by assessing the visibility of low contrast details

Frequency:  3 - 6 monthly

a)      Place TOR RAD or TOR CDR test object on the table with a focus –receptor distance of 1-1.5m

b)      Collimate to the cassette.

c)      Place 1mmCu filter in the beam.

d)      Expose at 70kVp with a manual mAs (this value should be determined in conjunction with medical physics).

e)      Read the cassette using the following parameters

Kodak: Mode – ‘Pattern’ with raw data and no edge enhancement

f)        Record the sensitivity index.

g)      Make three more exposures under the same conditions.

h)      Window and level the images so that background noise is perceptible.

i)        Print the images onto the largest film size available.

j)        View the image on a masked light box, and score each detail size using fixed distance viewing (<1m). If no hardcopy printer is available, score the images on a reporting workstation, optimising window and level settings for each detail size.

k)      Calculate the mean number of visible details (average over all detail diameters)

Remedial level: Average number of visible details reduced by two from baseline     

TOR CDR test object

CR3 Threshold Contrast Detail Detectability Results

Baseline

Results (Frequency:  3 - 6 monthly)

CR4 Limiting spatial resolution

Purpose:  To monitor image quality by assessing the resolution of the system

Frequency:  3 - 6 monthly

a)      Place resolution test grid (e.g. TOR RAD or TOR CDR) on a 24 cm x 30 cm cassette at ~1 m. The bars should be angled at 45^o to the plate.

N.B. Remember to remove the copper filtration from the beam.

b)      Set 50kVp.

c)      Expose at ~ 1mAs.

d)      Read the image plate using the following parameters 

Kodak:       Mode – ‘Pattern’ with raw data and no edge enhancement

e)      Determine the number of resolvable groups of lines.

Remedial level:  Number of resolvable groups reduced by 2 from baseline.

N.B. Other plate sizes may give different resolutions and should ideally be tested.

CR4 Limiting spatial resolution Results

 Baseline

Results (Frequency:  3 - 6 monthly)