Transition to Clerkship –
Radiology
Marc Gosselin, MD
What Penguins Fell Off The Iceberg
Since We Last Meet?
Introduction:
‘Medicine is the Science of Uncertainty and
the Art of Probability’ – Sir William Osler
• Goals
 Become familiar with and practice using the
webPACS system
 Gain a basic approach to interpreting chest images
 Gain a basic approach to interpreting bone images
 Understand the use of the abdominal film
 Understand the use of contrast
 Understand practical issues with MRI
Key Points
  Understand the need for clinical information
when ordering and interpreting radiological
studies
  Understand how consultation with a radiologist
before you order a study can help get the proper
study
  Try to learn about the tests that you are ordering
your patient to experience during your rotations.
You may never have another chance!
BEWARE:
The
‘Diamond
Algorithm’
is Very
Common!
Do NOT Be
Fooled!
Basics for Radiology
•
•
•
•
Contrast
MRI
Web sites
Images into a
presentation
Contrast
Contrast for x-ray related images is either:
Iodinated
Barium or Omni for Gastrointestinal tract
Contrast for MRI is gadolinium based
Some newer experimental agents are iron based.
Contrast
What it’s used for
•
•
•
•
Vessels
Tumor detection
Infection detection
Better anatomic detail
Contrast- When to order
• Brain (1st ? to ask - CT or just order MRI)
– Looking for tumor
– Infection
• Spine
– Rarely need
– Canal infection (epidural abscess, MRI better
choice)
– Minimal use in “bone” tumors/mets
• Chest, Neck, Abd, pelvis
– Very helpful and usually used (except Chest)
• Musculoskeletal system
– Ask Radiologist
– Mainly if need to know about vessels
Contrast - Risks
• Risk of death, at worst 1 in 130,000
• Renal failure, stroke, other severe
reaction is low as well
• Contrast Induced Nephropathy may be
more common than previously thought
Contrast – Risks – Allergy?
• Reaction to iodinated contrast agents are not
true allergies
– too small of agent to act as antigen
– no antibodies ever detected
• Even if the patient has had a previous reaction,
unlikely to have a reaction the next time
– Although a prior reaction remains the best predictor
of a future adverse event, the likelihood is in the range
of 8 – 25%
– If it were a true allergy the risk should approach
100%
Contrast – Risks – Allergy?
• Other allergies or asthma
– Only minimally predicts an increase risk
– Not a reason to avoid injection
– Asthma only predicts bronchospasm and then
only in active asthma cases
– Allergy to shellfish is not a predictor (organic
iodine)
Contrast-Induced Nephropathy
• Mainly a risk if there is some underlying
compromise of renal function
• BUN as a guide to state of hydration
• Creatinine as a guide to whether there is true
dysfunction
• Better test is creatinine clearance (calculated)
Alice Mitchell, MD et al: ACADEMIC EMERGENCY
MEDICINE 2012; 19:618–625
Nephropathy – Risk Factors
•
•
•
•
•
Diabetes
Recurrent renal stones
Recurrent UTI
Hx of bladder outlet obstruction
Recent events
– Major surgery
– Dehydration!! (Adequate hydration prior and after
administration is 1st step to prevent nephrotoxicity)
– Cardiogenic shock
• Other nephrotoxic agents
– Gentamycin etc.
– High-dose nonsteroidals
– Certain chemotherapy agents
Contrast – Risks – Allergy?
• Prior contrast reactions
– Urticaria to anaphylactoid process
– Use different agent (low osmolality, nonionic
isotonic dimmer (iodixanol))
– Have equipment and expertise available to
treat
– Pre-medicate with corticosteroids and/or
antihistamines
• Prevents minor reactions
• Not enough data to know if it prevents lifethreatening reactions
MRI Safety
•
•
•
•
Who can and can’t get scanned
What are the risks
What is the cost
What things to think/worry about
• Bottom line – risk vs. benefit vs. cost
MRI Safety Issues
• Metal
– Ferromagnetic
– Non-ferromagnetic
– Location
•
•
•
•
•
Orbit
Vessels/heart
Bones
Brain
Other
• Implantable devices
–
–
–
–
–
–
Pacemakers, ICDs
Pumps, stimulators
Wires, lines
Heart Valves
Aneurysm clips
Intravascular coils,
filters, & stents
MRI – other considerations
•
•
•
•
•
•
Claustrophobia
Noise
Heating (SAR – specific absorption rate)
Tattoos & permanent cosmetics
Pregnancy and Breast feeding
Magnetic Field Strength
Web Sites
• American College of Radiology
Appropriateness Criteria
– www.acr.org/dyna/?doc=departments/appropria
teness_criteria/text.html
• UpToDate (I Call it ‘FOX NEWS’)
– www.uptodate.com
• The Number Needed to Treat
– www.nnt.com
• OHSU Medical Student page
– http://sunweb1.ohsu.edu/radiology/med/
Web Sites
• Virginia Web Site (sections on head CT,
Cervical spine, ICU chest film, ER body CT,
Skeletal Trauma)
• http://www.med-ed.virginia.edu/courses/rad/
• Virtual Hospital, Introduction to Abdominal
Radiology.
http://www.vh.org/Providers/Lectures/icmrad/
abdominal/Abdominal.html
• University of Washington, Radiology Review:
http://uwcme.org/site/courses/legacy/threehourt
our/
rd
3
Year Tips
• Always try to helpful, in any way
• Search for evidence on the disease or treatment
regarding your patients each day
• Give presentations with literature from different
specialties…good career habit!
• Try to refer back to your basic science classes as
much as possible! (Don’t throw your books
away)
• Don’t rock the boat…at least not yet! (There
are serious “land mines” out there for
students…watch your step, watch what you say!)
rd
3
Year Tips
• Generate Questions (to Yourself) Every day!
• Generate Options for Work up or Therapy
Every day (to Yourself)
• Do NOT ‘Marry’ ANY Medical ‘Fact’
(Dogma) or ‘Standard of Care’! Watch out
for ‘They say…’ or ‘Everybody knows…’
• Be Outraged (Quietly) When You see any of
this: (I’ll likely get Vocal - you don’t…yet)
White Zinfandel is NOT a wine!
Scout for a CT of the
“Head, Chest, Abdomen,
Pelvis and Complete
Spine”
Has some abdomen and
low back pain…
Primary & Secondary
Survey were ‘Done’