Diagnostic Imaging
Diagnostic imaging tests radiography, ultrasound, positioning, radiation safety, contrast studies, and basic computed tomography and magnetic resonance concepts. The exam expects you to obtain diagnostic images, protect personnel, and recognize when a second view or modality is needed.
Core rules and concepts
- Obtain at least two orthogonal radiographic views, such as lateral and ventrodorsal or dorsoventral. A single view can miss or mislocalize a lesion.
- Position accurately and collimate to the area of interest. Poor positioning causes rotation, foreshortening, and false interpretations.
- Radiation safety follows ALARA: as low as reasonably achievable. Use lead gloves and aprons, collimate, avoid holding patients when possible, and wear dosimeters. Ultrasound does not use ionizing radiation.
- Know common artifacts: motion, grid lines, dirt on the cassette, and summation. Label all images with patient identification, date, and view.
- Contrast studies require patient preparation, informed consent, and monitoring for adverse reactions. Ultrasound is useful for fluid, soft tissue, and real-time guidance.
Worked example
A dog is suspected of swallowing a foreign body. Survey radiographs include a right lateral and a ventrodorsal view. If both are unremarkable but vomiting continues, abdominal ultrasound can detect nonradiopaque material, bowel plication, or free fluid. Document the reasoning and do not treat a single negative radiograph as definitive.
Traps that cost marks
- Taking only a lateral view and missing a foreign body.
- Failing to collimate or shield, increasing unnecessary exposure.
- Ignoring a dirty cassette or motion artifact and calling it disease.
- Forgetting to label images and losing traceability.