Radiographic evaluation Flashcards
What is a diagnostically acceptable image?
A
No errors or minimal errors in:
-Pt prep
-Exposure
-Pt / image receptor positioning
-Image processing
-Image reconstruction
There is sufficient image quality to answer the clinical question.
Digital quality: not <95%.
What is a diagnostically not acceptable image?
N
Errors in:
-Pt prep
-Exposure
-Pt / image receptor positioning
-Image processing
-Image reconstruction
Errors render the image diagnostically not acceptable.
Digital quality: not >5%.
What are the first things to assesses on a radiographic image?
- Correct pt ID on image: name, D.o.B, image study date (should match the day image was taken).
- Check that image is correctly oriented - silver dot on image receptor usually towards the crowns on a PA. On BW’s it will be positioned away from area of interest - either anterior or posterior. For OPT: appears on image L or R.
- Also look for roots pointing upwards on upper PA, and roots pointing downwards on lower PA. For BW’s the curvature of mandible is visible on lower arch.
BW’s: most anterior teeth on the corresponding side on the screen.
Other features:
Floor of antrum on upper PA’s.
No. of roots: 3 on upper, 2 on lower.
OPT: border of mandible visible on lower arch
What happens if the image receptor is back to front? So black side not facing collimator beam?
Copper dot will appear white and visible in middle of image as a circle.
- How is exposure checked on an image?
Under-exposure - image appears pale, or only some structures visible.
Over-exposure - image appears dark
Double exposure - an image over-lapping another image as film exposed without being processed the first time.
4.
What comments can be made about the patient preparation?
When an object obscures the field of exposure: e.g. any jewellery which was not removed, or dentures/ orthodontic appliances / hair clips etc.
Some appliances are fixed and cannot be removed e.g. surgical metal splints in jaw.
- Patient positioning errors can cause errors in the image. What causes this?
When the image receptor is not in line with the X-ray beam
Incorrect equipment assembly, collimator alignment or orientation.
Pt may move out of x-ray beam, image receptor may be displaced from holder.
5.
What are the IO image artefacts that may appear on the film?
Cone cutting - some parts of the image may be white or missed e.g. if pt not biting on the bite block.
What happens if the image receptor is back to front?
*So black side not facing collimator beam
Copper dot will appear white and visible in middle of image as a circle.
What happens if the occlusal plane is not horizontal?
When the bite block is not parallel, some areas of the image may not be visible.
When the bite block is twisted anteriorly/posteriorly rather than being directly parallel onto the area of interest, this causes ______________.
Overlapping contact points >50% into enamel
When the x-ray beam is not parallel to the image receptor this can cause ______ or _________ on the image.
Elongation or foreshortening.
IF the patient moves during exposure, what happens to the image?
Image appears blurred.
If the plate is bent, how does this affect the image?
Image can appear stretched or white marks on image can be created.
What errors can be visible on an OPT?
Unsatisfactory spinal shadowing if pt hunched/slumped. Feet should be forward and shoulders relaxed.
Chin up - creates a smile appearance on image
Chin down - creates a frown appearance on image
Anterior / posterior to focal trough & canine line: Frankfurt lines:
Chin too far forward: dentition narrow
Chin too far back: dentition big and broad
Asymmetry/ rotated positioning:
Mid-saggital line - if off centre, image on one side appears large and broad, whilst on other side appears small and narrow.
Tongue - should be pressed on palate the whole time- otherwise get a moustache shaped radiolucency on upper anterior apical region.
Lips - need to be pursed around bite block otherwise radiolucency appears on crowns of anterior teeth.
Blurring - if pt moves. Film can appear stretched to one side.
