Imaging Flashcards
Abdominal plain films
Uses: Obstruction series= supine abdominal, upright abdominal, upright chest Pros: - Assess gas, free intraperitoneal air - Determine position of devices - Detect calcification Cons: - Superimposition of structures - Lack of contrast resolution
Single contrast Upper GI series
Imaging of esophagus, stomach, duodenum. Multiple steps:
- IV glucagon (slows bowels)
- Liquid Barium suspension
- Fluroscopic guided imaging
Single contrast: large volume of thin barium–> distention
- Compess organs under fluoroscopic guidance
- Evaluate anatomy, detect large masses, assess organ caliber, presence/absence of obstruction, site of obstruction, motility/response to maneuvers
- Use water-soluble contrast (gastrografin- lower quality contrast) if perforation of concern- BUT do not use in small bowel obstruction, aspiration risk, or tracheoesophageal fistulas
Prep: NPO, no smoking, gum, oral meds with small sips of water
Double contrast UGI
Imaging of esophagus, stomach, duodenum. Multiple steps:
- IV glucagon (slows bowels)
- Thick barium= coats mucosal surfaces
- “Fizzies”= produce Carbon dioxide
Evaluate mucosal diseases, ulcers, tumors
- Use water-soluble contrast (gastrografin- lower quality contrast) if perforation of concern- BUT do not use in small bowel obstruction, aspiration risk, or tracheoesophageal fistulas
Prep: NPO, no smoking, gum, oral meds with small sips of water
Enteroclysis
Dilute contrast solution pumped into small bowel via oral or nasally inserted tube (b/c pt can’t drink fast enough to distend small bowel)
- Time consuming, uncomfortable
Cine-esophagram
Barium swallow Evaluate swallowing function in: - Recurrent aspiration - Recent C-spine surgery - Laryngectomy - Stroke - Myasthenia gravis - patients intubated for long periods
Barium Enema
Contrast exam of colon (fluoroscopic guidance)
Single contrast: only used in emergency with unprepped patient- exclude obstruction/diverticulitis
Air contrast: smaller amount of thicker Barium, air pumped into colon via rectal tube
- Use gravity to manipulate position of barium pool/air
- Detect mucosal colonic disease (IBD)
- More sensitive than single contrast < 1 cm in diameter
Contraindications= free air, extreme dilation on scout film, peritoneal signs (get surgical history!)
- Use water-soluble contrast (gastrografin- lower quality contrast) if perforation of concern (no barium in peritoneum)
Prep: Dietary restrictions, hydration, osmotic laxatives, contact laxatives
CT (Computed tomography)
Advantages: Good at detecting masses, determining origin, provide differential
- Used for percutaneous biopsy, drainage
- Assessing internal organ damage after trauma
- Detect extraluminal disease (inflammation, abscesses)
- Pancreas, retroperitoneal imaging
- Assess abdominal aortic aneurysms (AAA)
- Stage neoplastic disease
Limitations: expensive, not portable, uses radiation, doesn’t give overall picture (slices), oral contrast needed to distinguish bowel loops from other structures, direct imagining limited to axial plane
Patient:
- Needs intraperitoneal fat, but cannot weight more than 400 lbs
- Hold breat for few seconds, lay still
- NPO for 4 hours (avoid aspiration of vomit after IV contrast)
Ultrasound: Advantages and prep
Can assess movement (watching in real time)
- Portable
- More expensive than plain film (technician), but less expensive than CT/MRI
- No superimposition
- No radiation
Prep:
- Hepatic, biliary, complete abdominal ultrasound: NPO 6 hours
- Renal study: no prep
- Abdominal aorta, renal artery: NPO 6 hours
- Pelvic eval: drink 32 oz liquid before (no voiding)
Uses and disadvantages of ultrasound
Uses:
- Evaluate fluid-filled structures: bile ducts (rule out biliary ductal dilatation), gallbladder, blood vessels, renal collecting systems
- Focal liver lesions (less specific than MRI/CT)- follow-up known lesions
- Renal hypertension: define direction of blood in portal veins/collaterals
- Detect occlusion of hepatic veins
- Provide guidance for invasive procedures
- Pancreatic masses/collections, abdominal masses, abscesses, retroperitoneal adenopathy/hemorrhage
Cons:
- Suboptimal in obese patients
- Cannot penetrate air/bone
- Blind spots
- Less sensitive in detection of masses
- Operator dependent
MRI
Cross-sectional imaging
- No radiation
- Relies on chemical composition (molecular motion) of organs/structures
- Vascular contrast built-in (can be enhanced by gadolinium)
- Sensitive (Detects masses, dissection, invasion, thrombosis
Disadvantages:
- Most expensive
- Claustrophobia, lying still for long periods of time in enclosed environment
- Not portable
- Can’t administer in patients with any metal foreign bodies
Radiographs
Chest plain films
- X-ray image
Lung markings= blood vessels (overlays blackness of air in lungs)
- Completely black lung= pneumothorax
Air= black Fat= dark gray Water= light gray (soft tissue= organs, muscles, blood vessels, masses) Bone, Ca= white Metal= very white
- Problem: location in overlapping densities unclear- determined by perpendicular projection to localize object
Computed radiography
Produces digital radiographic images
Phosphor plate (vs films) exposed to x-rays
Viewed on monitor, transferred via networks
- Stored in PACS (picture archiving communication system)
Radiographic chest views
- Posteroanterior (PA)
- Anteroposterior (AP)
- Lateral- arms lifted out of way
- Decubitus (right or left side down)- determine pleural effusion by lying on side with effusion; pneumothorax- lie on other side
AP view used when patient too sick to be moved out of bed
- Heart appears larger when patient supine for film (farther from film–> more magnification)
Assessment of quality of chest x-ray
RIPPA:
- Rotation
- Inspiration: diaphragm should be down to ribs 9 to 11 (posterior)- vs expiration (8-10)
- Penetration: good lung detail, see bony spinal column, lung markings (over-penetrated= blackout, under-penetrated= white-out)
- Position
- Angulation: look at position of clavicle (leaning away: clavicles project back, ribs look straight; slumping forawrd: clavicles project forward)
Patterns of reading CXR
ABCDE
A= air (lungs, trachea, bronchi, gastric/splenic flexure gas)
B= bones (clavicles, ribs, shoulders, spine)
C= cardiomediastinal (no widening, extra densities)
D= diaphragm: check hemidiaphragms
E= Everything else (clips, lines, soft tissues: liver, spleen, breast, shadows, etc)
