Transcript INTRODUCTION TO MEDICAL IMAGING

HETI SPONSORED
RADIOLOGY
ESSENTIALS TEACHING
Dr Noel Young
Department of Radiology
Westmead Hospital
BASIS OF THIS TALK

Recommendations to HETI by
Intern / RMO advisory group.
OTHER CONSIDERATIONS


Should follow your University Imaging
teaching.
Key points of:
a.
b.
c.
d.
recognising key pathologies,
understanding clinical contexts for
radiology requesting
understanding context of reports per
individual patient requirements / status,
keeping your boss happy.
 With
PACS in all NSW public
hospitals, seeing all patients’ images
is easy.
 But interpretation is still the big issue.
DIFFERENTIAL FORCES IN
RADIOLOGY
Cost to Government
 Cost to patient
 Radiation cost to patient
VS
 Keeping patients happy
 Keeping lawyers at bay
 Differential clinical needs

TALK DIVIDED INTO THREE
PARTS
 Part
I – CT Brain
 Part
II – CT Abdomen and Pelvis
 Part
III – Abdominal Ultrasound (A)
– + Doppler Ultrasound (B)
PART I: CT BRAIN
Key Learning Objectives

When / what to request 



contrast issues
sedation issues
How to look at a CT Brain.
Common pathologies.
Question: When to request?
 Answer: When your boss wants it.
(Side issue – 4 hour Emergency objectives)




Real test – how to get Radiology to do it.
Answer: Communicate
(best done by going to the Department)


Question: When to sedate?
Answer:
1.
2.
Whenever you want nice pictures and patient
non-cooperative.
When patient is crashing.
(n.b. - be nice to your anaesthetist! – you
have little that anaesthetists need!)


Question: How to interpret?
Answers:
1.
2.
Remember normal anatomy
Look systematically – ask key questions 



3.
is there raised ICP
is there blood
is there an infarct
is there normal white / grey differentiation
Go ask someone more experienced (n.b. Your university should have taught this stuff –
you have already paid for it!).
COMMON PATHOLOGIES TO
RECOGNISE



Raised ICP
Recent territorial infarct
Blood - EDH (be careful!)
- SDH
- SAH
- focal haematomas
Right old middle cerebral artery infarct. 1. No mass effect. 2. Margins of the infarct are
well defined.
CT – recent left PICA infarct involving the cerebellum. 1. Ill defined low density
change. 2. Mass effect with compression of the 5th ventricle.
CT – Acute right posterior cerebral artery infarct, involving the occipital lobe. 1. The
area of low density is ill-defined. 2. Local mass effect is present.
CT – Acute infarct of right cortical hemisphere. 1. Loss of grey-white differentiation. 2.
Compression of right lateral ventricle.
Small extra-dural – right temporal region. Note the lentiform shape
Small left acute extra-dural haemorrhage. Local mass effect with cortical sulcal
effacement is present.
CT – Large right extra-dural haematoma. Significant mass effect.
CT – Acute left subdural haematoma. Massive mass effect. Significant shift of midline
structures to the right. Note crescent shape of haematoma.
Diffuse intraventricular blood and subarachnoid haemorrhage. There is effacement of
sulcal spaces globally indicating raised intracranial pressure.
Diffuse intraventricular blood and subarachnoid haemorrhage. There is ventricular
dilatation.
Subarachnoid haemorrhage involving the basal cisterns.
Left sylvian fissure and traumatic subarachnoid haemorrhage. A subtle finding. Due to
a small, ruptured, left MCA aneurysm.
1. Right subdural chronic haematoma. It is low density. 2. Small amount of more
recent blood (higher density) anteriorly.
IV CONTRAST ISSUES



Iodinated, isotonic contrast used.
Beware bad renal function (when premed with NAC, don’t forget the
saline).
Beware history iodine allergy
a.
b.
YES – allergy exists (anaphylaxis!)
Every hospital has a pre-med protocol
CT BRAIN (SURVIVAL KIT)
 Is
there white stuff around (blood)?
 Is there dark stuff around (infarct)?
 Is there raised intracranial pressure (can’t
see sulci or cisterns)?
PART II:
CT ABDOMEN / PELVIS
Key Learning Objectives

When / what to request 


contrast (IV and oral) issues
How to look at a CT abdomen.
Common pathologies.
 Question:
When to request?
 Answer: When your boss tells you.
 Question: What to request?
 Answer: Go ask your friendly
neighbourhood radiologist
(n.b. - please supply relevant clinical
information).
HOW TO INTERPRET
 Actually,
CTs of the abdomen are
a lot more complex than CTs of
the brain.
 Need best images to have a
fighting chance.
HOW TO INTERPRET
 Remember
what they taught you
at University.
 Be
systematic, follow the
anatomy.
HOW TO INTERPRET
General principles
 Does the liver look OK 


is there a tumour
are the bile ducts dilated
is there a collection
 Does



the pancreas look OK -
is there a mass
is it swollen
is there fluid around it
HOW TO INTERPRET
General principles continued
 Is there free peritoneal gas
 Is there free peritoneal fluid
 Is there a peritoneal collection
 Are there renal collecting systems
dilated
 Is the aorta too big
 Is there blood around the place
COMMON PATHOLOGIES
a. Perforation




free intraperitoneal gas
can see on CT little as 5 ml
look in anterior abdomen
look in region falciform ligament of liver
(n.b. - post abdomen surgery, free
gas can persist up to three weeks)
COMMON PATHOLOGIES
b.
Obstruction
•
•
•
•
when large bowel >5 cm diameter
when small bowel >3 cm diameter
actually better seen on plain AXR
CT better to define
•
•
masses
bowel wall thickening
COMMON PATHOLOGIES
b.
Obstruction continued
•
•
•
if caecum >9 cm diameter – risk of
perforation
beware toxic megacolon (gas and
wall thickening in transverse colon)
look for other lesions
COMMON PATHOLOGIES
c. Collection
•
•
•
fluid densities
round, walled
main scenarios
•
•
•
around pancreas in pancreatitis
in subphrenic spaces
in pelvis after bowel surgery
CT – very dilated intrahepatic bile ducts.
CT - Metastases – gross ascites with tumour in peritoneum.
CT – 1. Ascites – due to peritoneal metastases. 2. Metastasis to right lobe liver.
CT - acute cholecystitis. 1. Thickened gallbladder wall. 2. Fluid around gallbladder.
Subphrenic collection and percutaneous drain.
Subphrenic collection and percutaneous drain.
Severe, acute pancreatitis. 1. Diffuse pancreatic necrosis. 2. Calcified gallstones.
Acute pancreatitis & gallstones. Severe pancreatic necrosis.
CT – small pancreas pseudocyst, following previous pancreatitis.
CT - Rectus haematoma – on Warfarin. The blood is layered.
CXR – 1. Right subphrenic abscess. 2. Right subpulmonic pleural fluid.
CT – Mild appendicitis. Thickened wall of appendix.
CT – 1. Recto-sigmoid carcinoma, mass-like lesion. 2. Metastases to liver.
CT – Severe appendicitis
CT ABDO / PELVIS
(SURVIVAL KIT)
 Is
there free gas?
 Are bowel loops dilated?
 Is there a lump in the liver?
 Is the pancreas swollen?
 Are the renal collecting systems too big?
(these are >90% of conditions you need to
identify)
PART III (A):
ABDOMINAL ULTRASOUND
Key Learning Objectives


When to do Ultrasound VS
When to do a CT
Patient considerations 


fasting
size
How to interpret
 Question:
When to do an Ultrasound?
 Answers:
a. if
looking at gallbladder and biliary
tree pathology
b. if pregnant
c. in Emergency - portability
 Question:
What can’t be seen on
Ultrasound?
 Answer: Actually quite a lot.
Particularly a. AAA (rupturing)
b. free gas
c. pancreatitis
Question: ? Fasting
 Answer: if looking for gallstones (otherwise
gallbladder is contracted). Fasting for at least
6 hours.
 Question: When too big to bother?
 Answer: If over 100 kg
 Question: When to not bother asking for
Ultrasound?
 Answer: Pretty much anytime after sun sets
(n.b. – you can always get a CT)

HOW TO INTERPRET (1)
 Really
quite hard
 Go do a course
BUT ……..
 You are going to be expected to do it
in the future …….in Emergency
HOW TO INTERPRET (2)
Key things to look for
 Is the CBD too big – normal ≤7 mm
 Has the liver a “smooth” appearance
 Are there GB calculi
 Are the renal collecting systems
diluted
 Is there an aortic aneurysm – normal
≤3 cm
Ultrasound – mild appendicitis. 1. The wall of the appendix is thickened. 2. No fluid
around appendix.
Ultrasound - dilated biliary tree.
Ultrasound - dilated biliary tree. 1. The channel in front is the dilated CBD. 2. The
channel in the back is the portal vein.
Ultrasound – 1. CBD. 2. CBD is dilated at 1 cm.
Ultrasound – Acute cholecystitis. 1. Gallbladder is thickened. 2. The gallbladder lumen
is filled with material.
Ultrasound - dilated renal collecting system.
Ultrasound - ureteric calculus causing the collecting system obstruction.
ABDOMINAL ULTRASOUND
(SURVIVAL KIT)
 Is
the bile duct dilated?
 Is there stuff in the gall bladder?
 Is the aorta too big?
 Are the renal collecting systems dilated?
(these are >90% of conditions you need to
identify).
PART III (B):
ULTRASOUND DOPPLER
Key Learning Objectives


Indications
Interpretation

Question: What are indications to request?
I will change the question – What are the
usual clinical scenarios?




Presence of DVT in leg veins (most
common)
Presence of thrombus in arm veins (postlines)
Looking for abdominal AAA (CT is better)
Looking for arterial ischaemia 

leg arteries
neck arteries
INTERPRETATION VASCULAR
ULTRASOUND



Very difficult
Only for expert operators
Best advice to you a.
b.
Read the reports (not always
done!)
Go ask the reporter if you have a
query.
Ultrasound of abdominal aortic aneurysm – transverse view.
Ultrasound of abdominal aortic aneurysm – longitudinal view.
Doppler ultrasound – right femoral vein – thrombus.
Doppler ultrasound – right femoral vein – thrombus in long view.
Doppler ultrasound – right ICA – plaque with stenosis.
Doppler ultrasound – right ICA – stenosis – colour flow image.
CLOSING COMMENTS


This is a teaching file on subjects
considered priority by previous
RMOs
OK
BUT ……
Plain AXR interpretation far more
important for you guys early in your
medical career.