Imaging Unzipped – Ordering Options

Xray

• Typically best for seeing bones and air     (ex acute abd series looking for free air)
• AIR is black, tissue/bone is white
• Gold Standard: orthopedic, screening initial cxr
  • Air in places we don’t want – KUB air under diaphragm (upright CXR) means perforated bowel or air in soft tissue with nec fasc
  • When air is not where it should be: lungs full of air, CXR shows white patch could be PNA or fluid or tumor
  • Air patterns : KUB  bowel gas patterns (only for infants) SBO
• Pro: Old as dirt (invented in 1895!), low cost, relatively low radiation
• Limitations: miss early dz (like PNA, they say it takes at least 1-2 days to show, so if you are suspicious despite normal CXR then get CT), anything that is radiolucent including things like wood fb won’t show, misses lots of stuff in soft tissue – very limited use
• Types: don’t xray the cervical neck anymore or the skull, fluoroscopy for caths, myelograms, swallow study, barium enemas
  • KUB (kidneys Ureters Bladder) looking for kidney stones. Many ppl use it for “constipation” – like reading tea leaves.

Radio-opaque (objects that do show up) or Radiolucent (objects that do NOT)
No: plastic (requires CT or US)
Sometimes: wood (US best, then CT)
Yes: Metal, glass, stone

CT or CAT scan

• Typically best for most things, go to for bone, tumors, internal organs, bleeding
• Pro: higher resolution than MRI (therefore the highest) & easier to get
• Limitations: 1 CT = 200 CXR (given children are more sensitve to radiation, only do CT on child if ABSOLUTELY necessary, this does increase their risk of cancer later in life) Don’t do more than 6 in 6 month period for same complaint, but can do more than one per day depending on risks involved.
• Types: all kinds depending on kinds of contrast and where we put it
• Ex. angiogram (CT PE or CT abd looking for mesenteric ischemia)
• Ex. PET special contrast used by oncologists to look for spread of cancer
• Gold Standard: CT cervical spine, bowel problems (appendicitis), CT head for skull fracture, tumor/cancer

Ultrasound

• Typically best for real time imaging, for body cavities, moving tissue, fluid/inflammation
• Pro:  NO radiation at all, cost, gives real time imaging
• Limitations: very user dependent, body habitus & bowel gas
• Types: bedside (cellulitis vs abscess), doppler, OB/GYN, IR, echo (heart), kidneys
• Gold Standard: fetal imaging, ovaries/testicles, gallbladders, sports injuries, thyroid, dopplers, and echo to determine heart squeeze (aka CHF or not)
• When to order: superifical or moving

MRI

• Typically best for soft tissue like cartilage, m connective tissue, swelling, any neuro dx
• Pro: the most indetail pictures we have
• Limitations: NO METAL (rips out of body) some pacers are ok and all joint replacements but stimulators and other medical devices are not, pt gets claustrophobic & just scary put in a small tube that makes a loud banging noise, you have to stay still for 30-60 minutes, PRICE, this is the most expensive test
• Types: any body part,  MRV (venous), MRA (arterial)
• Gold Standard for all strokes or other neuro dx. spine tissue, neuro, joints, muscle
• Know that you are NOT going to get an MRI in the ER Unless you have cauda equina

Resources for learning to read imaging: