Lecture 3: Diagnostic Imaging Overview Flashcards
Which imaging modality uses high frequency sound waves to generate an image?
Ultrasound
What are the pros and cons of using ultrasound?
- Pros = no radiation, cheaper, and non-invasive
- Cons = bowel gas and lung tissue hinder US image; dependence of skills of techni
What is a FAST exam for diagnostic imaging and it’s primary views or windows?
- Focused Assessment w/ Sonography in Trauma
- Subxiphoid
- RUQ
- LUQ
- Suprapubic
A FAST exam diagnostic study is used to assess for what?
Free fluid in body
What are the 5 radiographic densities and how do each appear?
- Metal - BRIGHT WHITE
- Air - BLACK
- Soft tissue - LIGHT GRAY
- Fat - DARK GRAY
- Mineral - OFF WHITE
What are the 2 GI contrasts that can be used with X-ray?
- Barium
- Gastrograffin
After giving contrast to patient for XR, how long should you wait for best visualization?
45 mins s/p ingestion
Move to what type of XR has decreased costs?
Digital XR
What are the cons of using XR for imaging?
- 2D pic
- Radiation exposure
- Poor detail of soft tissue
Which imaging modality is used for mammograms and line/tube placement?
XR
How does fluoroscopy imaging work?
Allows for what type of imaging?
Uses continually emitted x-rays and allows for real-time visualization
How do the images and radiation exposure differ btw fluoroscopy and XR?
- Images are intensified = decreased radiation exposure
- Images are attenuated differently than XR
What are 6 uses for Fluoroscopy?
- Esophagram
- Upper GI study
- Small bowel follow-thru
- Barium enema
- Cardiac
- Vascular
What are 3 cons associated with using CT imaging?
- Potential contrast rxn
- Exposure to radiation
- Diagnosis limitations
What type of contrast is used with CT scans?
IV iodinated
What are the best uses of contrast with CT?
- Vessels
- Visualize tissue changes
- Urinary tract
- Fallopian tubes
Any suspicion of what 3 complications should make you think about using contrast with a CT?
- Bleed
- Renal stone
- Retroperitoneal hematoma
Neuro contrast with CT is good for visualizing what?
- Veno/angiogram
- Abscess
- Malignancy
One of the strengths of using MRI is that it provides greater detail of what structures?
Soft tissues
MRI uses a magnetic field to manipulate what?
Polarity of H+ ions
In regards to T1 vs. T2 weighted MRI images which has a higher signal intensity of water and is therefore more suitable for visualizing pathology?
T2
In regards to T1 vs. T2 weighted MRI images which gives better views of normal anatom (anatomical details, fat containing structures, subacute hemorrhages)?
T1
When using MRI what are 4 patient situations you must be aware of and take precaution to?
- Cardiovascular devices = pacemakers, stents, mechanical valves, IVC filters
- Unstable pts
- Claustrophobic and agitated pts
- Large body habitus
What is the preferred type of contrast used with MRI?
Gadolinium
Using gadolinium with T1-weighted MRI improves the visibility of what?
- Inflammation
- Tumors
- Blood vessels and some organs
- Blood supply
Nephrogenic systemic fibrosis is a possible adverse effect associated with what contrast agent?
Gadolinium
Although generally well tolerated, what are some of the risks associated with the use of gadolinium as a contrast agent?
Especially in which pt populations?
- Contrast induced nephropathy
- Nephrogenic systemic fibrosis
- Advanced renal failure or dialysis pt (GFR <30 mL)
When is the onset of nephrogenic systemic fibrosis following gandolinium exposure?
Signs/Sx’s?
- Onset: 2 days - 18 weeks s/p exposure!
- Sx: thickening and hardening of skin. Spares head. Mimics scleroderma!
- Stiffen extremities involved, flexion contractures
What are the pros associated with using MRI?
- Safe
- NO radiation
- Extremely precise w/ incredible soft tissue detail
What are 4 cons associated with using MRI?
- Not widely available
- Costly
- Body habitus
- Pts must have extreme patience (30-90 mins)
What are 3 systems that MRI is used for?
- Neuro
- MSK
- Repro
Which type of imaging modality uses the injection of contrast media directly into artery or vein via needle or catheter?
Angiography
What 3 systems is angiography utilized in?
- Neuro
- Pulmonary
- Cardiovascular
What are 3 deterministic effects (acute) associated with ionizing radiation exposure?
- Burns
- Sterility
- Radiation sickness
What are 2 stochastic effects (chronic) associated with ionizing radiation exposure?
- Cancer
- Hereditary
Which patient populations are at greatest risk from ionizing radiation exposure?
- Children
- Young adults
- Women of repro. age (always get urine β-hCG)
The cells most sensitive to radiation damage have what 3 characteristics?
- Rapidly dividing
- Undifferentiated
- Have a long mitotic figure
What 4 imaging modalities use ionizing radiation?
- Radiograph (XR)
- CT
- Fluoroscopy
- Nuclear medicine
Contrast is used with medical imaging to increase the differences in?
Density between anatomic structures
Special consideration for using contrast and radiation imaging techiques should be taken in renal patients with what serum Cr?
Cr ≥ 1.5
Which days during pregnancy are considered critical and should be considered when selecting an imaging modality with contrast or radiation?
Days 16-45!
Special consideration while using contrast and radiation imaging modalities need to be taken in pts on what medication?
Need to beware of what?
Metformin –> beware of lactic acidosis
What are the signs/sx’s of hypersensitivity rxns to contrast agents?
Hives, anaphylaxis, urticaria, pruritus, and angioedema
What are the signs/sx’s of chemotoxic rxns to contrast agents?
Self limited: N/V and flushing
What are the signs/sx’s of vasovagal rxns to contrast agents?
- Increased vasovagal tone
- ↑ vagal tone -> ↓ SA and AV node conduction = bradycardia w/ vasodilation
