Imaging Flashcards
Appropriateness of Imaging Scores
1-3 = not appropriate, 4-6 = may be appropriate, 7-9 = appropriate
How does the heart look on a PA view, how do you deal with that?
Heart always looks bigger, always order a lateral view as well
How is the quality of an oblique X-Ray?
Poor quality, can be used as a guide but not for dx
ABCDEFGH Mneumonic for CXR
Airway, Bone and soft tissue, Cardiac Silhouette and Mediastinum, Diaphragm, Effusions/Extras (lines, tubes, devices, surgeries), Fields (lung), Gastric bubble, Hilum
Fluoroscopy Uses
Functional information, PO contrast is required, evaluates the mucosa of the bowel
Angiography Uses
Reveals veins and arteries
Non-Contrast CT Uses
Evaluation of acute and subacute blood products, pre-surgical planning complex fractures, acute onset pain multi-joint arthropathy with no changes on plain radiographs, lung parenchyma, renal stones
Does contrast effect the dose of radiation administered?
Yes, contrast absorbs radiation at a higher rate and more radiation must be administered
What are the advantages of contrast?
Evaluation of solid organs and soft tissue
Why would you use oral contrast?
Suspicion of bowel pathology, abcess or lymphadenoapthy
When to use and avoid Gastrograpffin
More expensive, tastes terrible, can cause pneumonitis if aspirated, only used with suspected perforation
Benefits of Barium over Gastrograpffin
Well tolerated, inexpensive, can cause peritonitis
When would you use IV contrast
Evaluation of solid organs, vascular system, enhancement, patterns of masses, advanced function such as organ perfusion
Definition of Contrast Nephropathy
0.5 mg or 25% increase in serum creatinine at 48-72 hours after exposure
Risk Factors for Contrast Nephropathy
Cardiovascular disease, DM
What do you have to test before you send a patient for a CT with contrast?
BUN and SCr
Mild Contrast Rxn
Nausea, vomiting, urticaria, injection site warmth, injection site pain. Tx with observation 20-30 min
Moderate Contrast Rxn
Hives, vasovagal rxn, bronchospasm, mild laryngeal edema. Tx Saline, oxygen, leg elevation, Diphenhydramine, beta agonists, epinephrine
Severe Contrast Rxn
Severe bronchospasm, severe laryngeal edema, loss of consciousness, seizures, cardiac arrest. Tx life support equipment and CPR
CT Pre-Imaging Allergy Treatment
Prednisone 50 mg at 13, 7 and 1 hour. Diphenhydramine 50 mg oral, IV or IM 1hr prior. Methylprednisolone 32 mg orally 12 and 2 hours prior - optional Benadryl
Normal SCr
0.5 - 1.2 mg/dL
Metformin
Hold for 48 hours AFTER the exam (some say 48 hours before as well)
Nephrogenic Systemic Fibrosis
Vessels become fibrotic, no longer work. All vasculature in the kidney is scarred. Irreversible. Avoid MRI contrast if GFR <30
When do you use High resolution CT?
Lung inflammation and scarring. Ex) Pulmonary fibrosis
SOB after surgery think…?
Embolism
What is the well’s Criteria used for?
Evaluating risk of DVT
If you have a suspected PE with a wells score of <4
D-dimer assay. If it is normal, PE is excluded. If it is abnormal PE cannot be excluded, do CT with pulmonary angiography
If you have a suspected PE with a wells score of >4
CT with pulmonary angiography
Advantages of MRI
Excellent soft tissue contrast resolution, imagines in any plan, no radiation
Limitations of MRI
No dense bone detail or calcification, limited resolution
What is MRI the imaging of choice for?
Pelvic disease
When do you need a contrast MRI?
Neoplastic lesions, vasculature (not blood flow), inflammatory or infectious processes
Myelopathy
Cord compression - medical emergency, risk of paralysis
When to use Ultrasound
Reproductive organs, peripheral venous and arterial, biliary system, fetal assessment, heart structure, renal stones, liver, spleen, pneumonia/pleural effusions
PET scan isotope
Radioisotope 18-fluorodeogyglucose
How does PET work?
FDG transported across cell membrane of actively metabolizing cells. Tumors are visualized because they have greater glucose metabolism
Where do you see false positive PET?
Highly metabolic normal tissue (brain, bowel, GU, uterus)
Where do you see false negative PET
Tumor <1cm, low metabolic tumors
