Too few x-ray photons (not enough mAs) = quantum noise

What is quantum mottle? Grainy appearance on an image caused by underexposure

What does quantum mottle look like? Black and white speckles

How is quantum mottle caused? not enough x-ray photons

How do you get rid of quantum mottle? Increase technique (kVp & mAs)

Positioning is based on body part being imaged, condition of patient, and suspected disease. Body positioning is important because many of the internal structures superimpose over each other, therefore, certain positions are required to get a clear view of the area of concern.

Ex. Chest X-ray: The heart lies more anterior and a little to the left, this is why the PA projection is preformed; so the heart will be closer to the IR. A perpendicular CR is used at 72 SID. If any of these factors are altered we have the possibility of size distortion.

Ex. Abdomen

Patient needs to be fully changed in gown for an abdomen study. A pillow under their head and support under their knees for support will enhance patient comfort. A key factor in quality abdominal imaging is the prevention of motion; this is why breathing instructions are required for this exam. Using the shortest exposure time possible will help in this case. Before taking the exposure, ensure that the patient is following the breathing instructions and that you are allowing time for them to make all breathing movements. Abdominal radiographs are taken during the expiration portion, this will result in the diaphragm in a superior position for better visualization of abdominal structures.

1. Was the correct SID used?
2. Does the projection demonstrate the least possible amount of size distortion?
3. Does the projection demonstrate undesirable shape distortion?
4. Was the part positioned with the least amount of OID possible?
5. Does the projection demonstrate signs of undesirable patient motion or respiration?
6. Are there anatomic artifacts demonstrated?
7. Was scatter controlled with grids/collimation?
8. Does the projection demonstrate quantum noise?
9. Is there a decrease in contrast and detail visibility caused by fogging?
10. Is the exposure indicator within the acceptable range for this system?

The technologist must be able to make an analysis of each radiographic image they take to determine if the image is acceptable. They must asses the following: Superimposition, adjacent structures, brightness, contrast, spatial resolution, magnification, and shape distortion. Although the technologist can not control involuntary motion such as a heartbeat, they can control voluntary motion such as discomfort by using sponges to keep their body in position to obtain the proper projection. When the technologist reviews their images they must be able to consider all normal appearances of the bodies structures.

Evaluating a projection after the exposure is made:

1. Demographic information is included
2. Projection is accurately displayed
3. Correct marker placement
4. Appropriate collimation
5. Relationships between the anatomic structures are accurate for the projection demonstrated
6. Projection demonstrates maximum spatial resolution
7. Radiation protection practice: Is gonadal shielding evident and accurately positioned when gonads are within the beam range?
8. Is the exposure indicator within acceptable range for this system?
9. Does this projection demonstrate quantum noise?
10. Contrast resolution is optimal?
11. No preventable artifacts are present