Transcript Slide 1

Intended learning outcome
 The student should learn at the end of this
lecture principles of Gastrointestinal
Radiology.
GASTROINTESTINAL RADIOLOGY
Topics to be covered
 1. Liver Lesions – Haemangioma and HCC
 2. CT Colonography
 3. Small bowel - CT, MRI or fluoroscopy?
 4. Rectal tumor – MRI staging
 5. Anal fistula – MRI imaging
Liver – Haemangioma (US)
Atypical
Liver Haemangioma CT
A) Pre-contrast
B) Arterial phase
C) Portal venous phase
D) Delayed phase
CT – we will not do delayed phase unless haemangioma suspected.
Please specify “? haemangioma” on request form.
Haemangioma Summary
 Common- often incidental
 US – Echogenic -no halo. No colour flow.
Aytpical – hypo-echoic in fatty liver
- mixed echotexture
 CT – C- low density
C+ peripheral vessels (uneven)
C+ PV /delay progressive fill-in
Small haemangioma fill in immediately and
cannot be distinguished from metastates.
 MRI features similar to CT post Gadolinium
CT -HCC
pre contrast
Arterial enhancement
(central and early)
Washout on portal venous
indicates fast flow
HCC Summary
 US - usually heterogeneous Usually HepB +ve with
raised alpha FP
 CT – C- low density
C+A – central early contrast (high flow rate)
C+PV – washout cf with liver
– may have a capsule
 MR – intracellular fat on T1 out of phase
- similar perfusion characteristics to CT
MRI IMAGES of LIVER
 Look at CSF first to tell if T1 or T2
 T1-in/out.
 T1 are grey. Fluid is dark. Black outline
 T2-incl HASTE.
 More definition. Fluid is bright.
 Gadolinium – always with T1
Fatty liver with sparing
Same pt - out of phase T1 MRI
Same patient - CT non-contrast
CT COLONOGRAPHY
Dissection
Strip, anus
to caecum
Endoluminal
(for fun only)
Orientation
Overview
800/40 window
Axial to loops
Advantages / disadvantages
 Sensitivity and specificity is of the order of 90 %








for 10 mm polyps.
Easy, quick and well tolerated.
Beats barium enema hands down.
Safer than optical colonoscopy
Approx. half the price of optical colonoscopy
No intervention possible as in optical Cy
At present for “Ba enema” indications, but is likely
to be used for screening in future.
Radiology manpower training required.
Radiation dose equivalent to Ba Enema
Incidence of Colonic Perforation at CT Colonography: Review of
Existing Data and Implications for Screening Asymptomatic Adult
Source: International Working Group on Virtual Colonoscopy
Total VC studies considered
21,923
Symptomatic Perforation Rates for VC*
0.005%
Total Perforation Rates for VC
0.009%
Perforation Rates for Conventional Colonoscopy
0.1-0.2%
Pickhardt 2007
Longer tube and patient can apply air
themselves
Lateral topogram
workstation layout
Incomplete air column -Excess fluid
Supine
Prone
Diverticular disease
4 mm Polyp
Ileo-caecal valve
Arrow points
To caecum
Residual
tagging
Caecal
pole
Dirty Caecumnot fully open on supine or prone views
54 yr
Recomm optical
colonoscopy
The dirty caecum
Complex Folds at flexures
Radiation
 Barium enema 6 – 8 mSv
 CTC estimate of 7.6 mSv with low mAs.
Increased noise, but high resolution
improves definition of small polyps
 Thin slice, limit tube current
 Background radiation is 2.4 MSv/year
Small Bowel Imaging
 < 35 yrs – MRI for radiation reasons
 However if pre-surgical workup–fluoroscopy
 CT Enteroclysis – only difference from CT is
negative contrast in bowel. No advantage to
do if recent normal CT.
 MR Small bowel – breath-hold sequences,
dynamic change between sequences. Good
soft tissue differentiation. +/- Gadolinium
Normal Fluoroscopic Enteroclysis
Jejunal intubation
Low density barium
Pumped in to distend
Intubation 10 min
Study 20 min
Terminal ileum
Skip lesions - Proximal
Follow-through
time-consuming
flocculation
Strictures may
be hidden
Is superseded
by other tests
Enteroclysis- same patient
Intra-luminal mass
CT Enteroclysis
Histo- GIST
Tumor shows up against negative contrast in bowel. Positive contrast could hide it
CT ENTEROCLYSIS
Jejunum often thick-walled
Can evaluate bowel wall due to
negative contrast in lumen and
IV contrast in wall.
Evaluates stomach well also
Plus standard CT
Reserved for older patients due
to radiation dose
MRI Small Bowel
 Good for Crohns patients with multiple studies





and large radiation dose over time.
Coronal TRUFI
Coronal TRUFI fat saturation
Coronal HASTE
Axial HASTE
Coronal T1
MRI
ENTEROCLYSIS
TRUFI
Normal- HASTE sequence
Terminal ileum
Cutaneous fistula
Post Gadolinium T1 fat sat
Caecum / TI
Crohns disease
Normal
FAT SATURATION
Sag, axial and coronal
Normal anal canal - sagittal
Puborectalis
Internal sphincter
Subcutaneous
External sphincter
Normal anal canal - axial at PR
mucosa
Internal
sphincter
Pubo-rectalis
= upper external
sphincter
Fat in intersphincteric space
Normal anal canal - coronal
Puborectalis
Internal
Sphincter
External
Sphincter
Post Gad fat saturation T1
Drain in situ
ANTERIOR
POSTERIOR
UC - mucinous tumour
UC - mucinous tumour
Anal canal tumour
Text Book
 David Sutton’s Radiology
 Clark’s Radiographic positioning and
techniques
Assignment
 Two students will be selected for
assignment.
Question
 Describe role of adequate preparation in
CT colonoscopy?

Thank You