Basics of Diagnostics Imaging

Question 1

Colors on x-ray

Answer 1

• Dependent on density of tissue they pass through
• Air = black
• Fat = light black
• Water = grey
• Bone or metal = white

Question 2

Radiography

what? Views? Indications

Answer 2

• X-ray waves pass through tissue onto cassette and form images
• Bones = good imaging
• NOT tendons, mm, soft tissue
• Need multiple views: Views: AP or PA (front → back) or (back → front); Oblique; Lateral
• Abd + GI = looking for air and feces

Question 3

Computed (Axial) Tomography (CT scan)

What? Angles? Purpose of contrast

Answer 3

• Good for: organs, soft tissues, bones, blood vessels
  
  • Especially Abd/pelvic CT (visualizing organs)
• Angles: Axial/transverse (top/bottom); Median/sagittal (side to side); Coronal (front/back cut)
• Done with or without contrast medium → Enhances density of blood vessels, vascular soft tissues, organs and tumors
  
  • Contrast → drink hour or two before scan
• Quicker than an MRI

Question 4

CT scan indications

ADDFITS

Answer 4

• Trauma
• Intracranial hemorrhage
• Abdominal injury
• Fracture detection/evaluation - get ortho consult
• Spine alignment
• Detection of foreign bodies
• Diagnosis of neoplasms
• Tumor staging
  
  • Serial CT scans to compare

Imaging of choice for internal organ damage

Question 5

Spiral CT

What and comparison to regular CT scan

Answer 5

• CT continuously circles patient → x-ray beam going around and scanning continuously
  
  • Faster than regular CT
  • Less radiation
  • Better resolution
  • Patients tolerate it better
  • Recommended for eval of PE as patient’s don’t have to hold breath as long

Question 6

Contrast media types and purpose of contrast

Answer 6

• Provide enhanced contrast between types of tissue and normal vs. diseased tissue
• IV
  
  • Iodinated
  • Gadolinium
• Oral - Barium

Question 7

Iodinated contrast

Answer 7

• IV
• Views vascular structures and solid abd/pelvic organs
  
  • High risk for allergy, may require premedication with antihistamine or steroid
  • Consider D/C metformin prior to scan due to renal risk, especially when older
    
    • Do kidney function tests prior; Cr < 60 at least 3d prior
    • Can take metformin when kidneys cleared of dye

Question 8

Gadolinium contrast

Answer 8

• IV
• MRI, must be a magnetically active compound
  
  • Low allergy risk but can rarely cause nephrogenic sclerosing fibrosis (NSF) in patients with severe renal disease

Question 9

Barium contrast

Answer 9

• Oral contrast
• Doesn’t taste good - patient has to drink this
• Good for Abd + Pelvic CT scans
• Fluroscopy (GI series)

Question 10

When would you do contrast vs non-contrast for CT scan?

Examples

Answer 10

• Contrast
  
  • Abd/pelvic
    
    • Unless looking for RENAL STONE → contrast hides stone
    • Diverticulitis
  • Brain tumors
• Non-contrast
  
  • Brain bleed (bleeding in general) → blood provides enough contrast
  • Renal stones

Question 11

MRI

what? Indiaction? views? disadvantages?

Answer 11

• Imaging in coronal, sagittal/median, axial planes
• Soft tissue imaging - better than CT or xray
• NO RADIATION - uses magnetic fields to image protons
  
  • Color of scan = [protons]
    
    • Fat = white
    • Bone cortex = dark
• Disadvantages: cost, length of exam (longer than CT), noise, claustrophobia (huge)

Question 12

CT scan vs. MRI imaging

Brain imaging

Answer 12

• CT
  
  • Emergent situation
  • Concern for acute bleeding, bone fractures, hydrocephalus (head CT); sudden loss of consciousness or seizure → CT scan (hit head, stroke) may later get MRI
  • Pt has contraindication for MRI
• MRI
  
  • Concern for tumors, degenerative neurologic disease, neurologic change
    
    • H/As, red flags for tumors
    • MS, ALS, dementia (lab and imaging workup) memory workup
  • Looking for subtle changes in brain itself
  • Contraindication to CT (I.e: contrast allergy0

Question 13

Ultrasonogrphay (U/S)

What? planes?

Answer 13

• Produces images in multiple planes - similar to CT and MRI
• Longitudinal and transverse planes
• REal-time imaging
• Can push on certain areas to enhance image

Question 14

U/S advantages and disadvantages

Answer 14

• Advantages
  
  • Multiple plane imaging - including obliques
  • Safe - no known biologic hard at dx sound frequency levels
  • Painless, noninvasive
  • Less expensive than CT and MRI
  • Equipment cost is less than that of CT and MRI
  • Real-time imaging, portable
• Disadvantages
  
  • Requires technical skill or is operator dependent
  • No good for bone or lung imaging

Question 15

U/S indications

A.C.J.L.O.P.T.T.V.

Answer 15

• Obstetrics
• Pediatric brain
• Testicle and prostate: 1st line for testicular pain or nodules
• Female pelvis
• Chest for pleural fluid drainage
• Abdomen (kidney, pancreas, liver, and gallbladder)
  
  • Vague abd p! (mass or inflamamtion)
• Vascular disease (rule out DVT)
• Rotator cuff of shoulder
  
  • Joint injections - point of care testing
• Thyroid - U/S imaging of choice
• Lymph nodes - adenopathy not painful; cystic mass unknown (growths)

Usually U/S → CT scan if not clear dx

Question 16

Abdominal imaging

Answer 16

• RUQ pain - liver and gallbladder - U/S
• LLQ, RLQ - CT scan
• Non urgent
  
  • Abd - U/S or CT scan
• Chronic generalized abd pain - U/S
• KUB (kidney, urinary, bladder U/S) - also imaging of intestines
  
  • See stool