detector dose indicator monitoring and uniformity test

Question 1

what is detector dose indicator monitoring

Answer 1

baseline levels can be calculated and used to monitor the long-term decline of the system and plates
- a test performed by MPE upon installation to set a baseline value and then repeated by radiographers

Question 2

frequency of detector dose indicator monitoring

Answer 2

monthly

Question 3

set up detector dose indicator monitoring

Answer 3

• table and tube level
• place image receptor onto table
• centre tube to receptor using 100cm
• open collimation to cover the entire receptor
• place 1mm copper filter on LBD
• expose using 70kVp and 3mAs
• repeat steps 1-6 using other image receptors
• process image using correct software parameters

Question 4

what should you ensure

Answer 4

• ensure the collimators are opened to entire image receptor , preferably before you attach the filter
• copper filter attached under the collimators in primary beam
• spirit level to ensure the table is flat

Question 5

evaluating our results

Answer 5

• using the images that are acquired an average exposure indicator
• this is then compared to the baseline with a tolerance level of 20% +-

Question 6

uniformity

Answer 6

to check for artefacts
- spots ? –> plate needs to be cleaned
- lines? –> CR reader optics need to be cleaned
- cracks? –> plate should be removed from service

Question 7

the setup for uniformity

Answer 7

• ensure table and tube level
• place image receptor on table
• 100cm SID
• open collimation to cover entire receptor
• place 1mm copper filter to LBD
• expose using 70kVp and 3mAs
• repeat using other image receptors

Question 8

evaluation the image for uniformity

Answer 8

• there should be uniform brightness and no artefacts
• ROIs should be drawn in each corner of image and in the centre
• if the pixel values change the test should be repeated 2 times