Radiology - Quality Assurance & Fault Analysis

Question 1

what is the purpose of quality assurance?

Answer 1

To ensure consistently adequate diagnostic information with radiation exposure being ALARP.

Question 2

why should digital receptors be checked?

Answer 2

Since they are reusable they undergo wear & tear and mishandling – This impacts the image quality.

Question 3

when should digital receptors be checked?

Answer 3

Every 3 months (or sooner if required)

Question 4

what are we assessing in digital receptors?

Answer 4

The receptor: ensure no visible damage to casing/wiring and check if its clean.

The image uniformity: by exposing it to an unattenuated x-ray beam and check if the resulting image is uniform (shows a consistent shade of grey – it is damaged it will be different shades of grey)

The image quality: take a radiograph of a test object and assess the resulting image against what an ideal image would look like (baseline)

Question 5

what damage are we looking for in digital phosphor plates? (3)

Answer 5

(white areas)

Scratches – white lines

Cracking – network of white lines

Delamination – white areas around the edge

Question 6

what damage are we looking for in digital Solid state sensors?

Answer 6

less damage occurs since theyre encased.

Sensor damage – white squares or straight lines

Question 7

what colour is damage to digital receptors?

Answer 7

white

Question 8

what colour is damage to film receptors?

Answer 8

black - due to sensitisation of the silver halide crystals

Question 9

what types of damage are commonly see in film receptors?

Answer 9

Nail marks, bite marks and fingerprints

Question 10

how do we test image quality?

Answer 10

using the step wedge technique

Question 11

describe the step wedge technique used to test image quality. (when, how, damage)

Answer 11

• This is carried out every morning for film, done regularly with digital just not every morning.
• Expose to a normal clinical exposure (i.e. a tooth) and then compare the image to a baseline.
• The baseline image must be able to identify all 6 steps of the overlapping layers of lead foil.
• A damaged receptor would have poor contrast between the layers

Question 12

using the step wedge technique how could you tell that the receptor was damaged?

Answer 12

A damaged receptor would have poor contrast between the layers

Question 13

what are the 3 components of quality assurance?

Answer 13

1. Image quality rating – grade each image
2. Image quality analysis – carried out periodically: calculating the success rate of images and identify trends of suboptimal (non-diagnostic) images.
3. Reject analysis – Record and analyse every unacceptable/non-diagnostic image

Question 14

how do we rate the image quality in quality assurance?

Answer 14

An image can either be A – acceptable or N – not acceptable; (use this instead of grading)

Acceptable = no/minimal error and can answer the clinical question.

Question 15

what is the target for diagnostically acceptable digital radiographs we have to meet?

Answer 15

95% acceptable

Question 16

what is the target for diagnostically acceptable film radiographs we have to meet?

Answer 16

90% acceptable

Question 17

What must we know before determining whether a radiograph is diagnostically acceptable?

Answer 17

We must know what teeth we should be analysing

We must know what parts of the tooth/teeth we want to analyse

We must know what other structure should be present

We must know the extend of the pathology we are wanting to see

Question 18

What should diagnostically acceptable bitewings show?

Answer 18

• Upper and lower crowns (all of the crown)
• The mesial aspect of the first posterior tooth (1st premolar) and the distal aspect of the last standing tooth (this may require > 1 radiograph)
• Approximal surfaces/contact points without overlap (impossible in crowding)

Question 19

What should diagnostically acceptable periapicals show?

Answer 19

• The entire tooth and root
• The periapical bone
• The crown

Question 20

What is fault analysis?

Answer 20

Identifying and explaining fault so they can be resolved.

Question 21

what are potential faults that can occur? (6)

Answer 21

• Too dark/pale
• Poor contrast
• Unsharp
• Distorted
• Over-collimated
• Receptor marks/damage

Question 22

what causes cone cutting?

Answer 22

Incorrect assembly of the receptor holder

Incorrect alignment of the x-ray tube and the receptor holder

Incorrect orientation of the rectangular collimator

Question 23

what exposure factors cause an image to have the incorrect radiodensity (too dark/light)? (3)

Answer 23

Incorrect exposure settings

The patient’s tissues are too thick

Faulty timer on the unit

Question 24

what developing factors cause an image to have the incorrect radiodensity (too dark/light)?

Answer 24

Incorrect duration of development
- short time = pale

Incorrect temp
- cold = pale

Incorrect concentration
- dilute = pale

Question 25

what VIEWING FACTORS cause an image to have the incorrect radiodensity (too dark/light)? (3)

Answer 25

Inappropriate light source for film i.e not using light box

Inappropriate display screen/monitor (digital)

Excessive environmental light