General CT and MRI Issues
- What are the patient weight and girth limits for different types of scanners?
- What are the indications for cervical spine CT in the setting of trauma?
- What is the recommended imaging study for evaluation of pulmonary embolus in pregnant patients?
- How do you decide if a patient is a suitable candidate for CT angiography examinations?
What are the patient weight and girth limits for different types of scanners?
|Hospital||CT Scanner||MR Scanner||PET-CT Scanner||Gamma Camera||Fluroscopy Table||Interventional Radiology|
|Skagit Valley Hospital||450 lb, 70 cm bore||350 lb, 60 cm bore||450 lb, 70 cm bore||400 lb||350 lb||440 lb|
|Island Hospital||440 lb, 70 cm bore||350 lb, 60 cm bore||NA||350 lb||500 lb||400 lb|
|Central Peninsula General Hospital||425 lb, 70 cm bore||350 lb, 60 cm bore||NA||400 lb||330 lb||NA|
What are the indications for cervical spine CT in the setting of trauma?
The following clinical predictors of injury are appropriate criteria to evaluate patients with CT, rather than radiography.
- High-speed motor vehicle accident: >35 mph combined
- Motor vehicle accident with death at scene
- Fall of >10 feet
- Known closed head injury
- Pelvic or multiple extremity fractures
- Neurologic symptoms on physical exam
- Cervical spine radiculopathy on physical exam
Reference: Julian A. Hanson, C. Craig Blackmore, Frederick A. Mann, and Anthony J. Wilson. Cervical Spine Injury: A Clinical Decision Rule to Identify High-Risk Patients for Helical CT Screening. Am. J. Roentgenol., Mar 2000; 174: 713 - 717.
What is the recommended imaging study for evaluation of pulmonary embolus in pregnant patients?
Computed tomography makes use of ionizing radiation, which should be avoided when possible, especially in pregnant patients, and especially in the first trimester of pregnancy. However, when absolutely necessary, pulmonary CTA (CT angiography) is the preferred method of radiologic evaluation for pulmonary embolus in pregnant patients, provided that no contra-indications to iodinated contrast are present. It is unlikely that a single CT examination will lead to serious adverse outcomes to the fetus. The use of iodinated contrast in pregnant patients has not been shown to be associated with adverse outcomes.
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How do you decide if a patient is a suitable candidate for CT angiography examinations?
Studies have shown that interpretation of CTA examinations is limited by vessel calcifications. Patients with diabetes, coexisting cardiac disease, and age greater than 80 have been shown to have a sufficient degree of vascular calcifications that would limit CTA. Also, patients with certain degrees of renal insufficiency may be better served by an MRA examination rather than CTA.