2007 Gastroreg Lecture

7/28/2019 2007 Gastroreg Lecture

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GASTROINTESTINAL RADIOLOGY

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

Topics to be covered


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Liver Haemangioma (US)

Atypical


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Liver Haemangioma CT

A) Pre-contrast


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B) Arterial phase


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C) Portal venous phase


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D) Delayed phase

CT we will not do delayed phase unless haemangioma suspected.

Please specify ? haemangioma on request form.


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Haemangioma Summary

Common- often incidental

US Echogenic -no halo. No colour flow.

Aytpical hypo-echoic in fatty liver

- mixed echotexture

CT C- low densityC+ peripheral vessels (uneven)

C+ PV /delay progressive fill-in

Small haemangioma fill in immediately andcannot be distinguished from metastates.

MRI features similar to CT post Gadolinium


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CT -HCC

pre contrast


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Arterial enhancement

(central and early)


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Washout on portal venous

indicates fast flow


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HCC Summary

US - usually heterogeneous Usually HepB +ve withraised 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


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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


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Fatty liver with sparing


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Same pt - out of phase T1 MRI


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Same patient - CT non-contrast


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CT COLONOGRAPHY

Dissection

Strip, anus

to caecum

Endoluminal(for fun only)

800/40 windowAxial to loops

OrientationOverview


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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


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Incidence of Colonic Perforation at CT Colonography: Review ofExisting Data and Implications for Screening Asymptomatic AdultSource: 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


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CTC vs Optical Colonoscopy

CTC for average risk and Fam Hx pts.

> 50 yrs (radiation)

Contraindicated if inflammatory bowel or on steroids(risk of perforation as inflation is done blind as

opposed to Ba enema).

Optical Colonoscopy if biopsy or polypectomy probneeded

All polyposis syndromes High risk

Inflammatory Bowel Disease

Consider Is intervention likely to be needed? (cf MRCP vs ERCP)


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Overview of CT colonography?

Process Currently Future

CLEANSE -Tagging -Subtraction

DISTEND -Air -CO2

COMPUTE -Workstation -new programs

VIEW -Time - CAD

REPORT -Issues

P d i


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Prep and tagging

Slide courtesy Dr Helen Moore


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Longer tube and patient can apply air

themselves

Slide courtes Dr Helen Moore


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Lateral topogram


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Philips workstation layout


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Incomplete air column -Excess fluid

Supine Prone

Can rotate ima e volume to view as a Ba enema in 3D


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Diverticular disease


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4 mm Polyp


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Ileo-caecal valve

Residual

tagging

Arrow points

To caecum

Caecal

pole

Dirty Caecum


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Dirty Caecum-not fully open on supine or prone views

54 yr

Recomm optical

colonoscopy


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The dirty caecum


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Complex Folds at flexures


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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

The worldwide average background dose for a human being is about 2.4

millisievert (mSv) per year.[1] This exposure is mostly from cosmic radiation andnatural isotopes in the Earth. This is far greater than human-caused background

radiation exposure, which in the year 2000 amounted to an average of about

0.01 mSv per year from historical nuclear weapons testing, nuclear power

accidents and nuclear industry operation combined,[2] and is greater than the

average exposure from medical tests, which ranges from 0.04 to 1 mSv per

year. Source Wikipedia.
http://en.wikipedia.org/wiki/Absorbed_dosehttp://en.wikipedia.org/wiki/Sieverthttp://en.wikipedia.org/wiki/Sieverthttp://en.wikipedia.org/wiki/Absorbed_dose


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Small Bowel Imaging

< 35 yrs MRI for radiation reasons

However if pre-surgical workupfluoroscopy

CT Enteroclysis only difference from CT isnegative 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


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Normal Fluoroscopic Enteroclysis

Jejunal intubation

Low density barium

Pumped in to distend

Intubation 10 min

Study 20 min


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Terminal ileum


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Skip lesions - Proximal


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Follow-through

time-consumingflocculation

Strictures maybe hidden

Is superseded

by other tests


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Enteroclysis- same patient


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Intra-luminal mass

CT Enteroclysis


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CT Enteroclysis

Tumor shows up against negative contrast in bowel. Positive contrast could hide it

Histo- GIST


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CT ENTEROCLYSIS

Volumen oral contrast for 45 min pre scan

IV Maxolon

IV contrast on table

CT to include anal canal and with sagittal.


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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


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MRI Small Bowel

Oral Volumen 30 45 min prior (or Ioscan)

+/- IM Buscopan for peristaltic movement Good for Crohns patients with multiple studies

and large radiation dose over time.

Coronal TRUFI

Coronal TRUFI fat saturation

Coronal HASTEAxial HASTE

Coronal T1


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MRIENTEROCLYSIS

TRUFI

N l HASTE


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Normal- HASTE sequence


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Terminal ileum


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Cutaneous fistula

Post Gadolinium T1 fat sat


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Caecum / TI


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Crohns disease


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Normal

FAT SATURATION

Sag axial and coronal


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Sag, axial and coronal

N l l l i l


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Normal anal canal - sagittal

Subcutaneous

External sphincter

Puborectalis

Internal sphincter

N l l l i l t PR


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Normal anal canal - axial at PR

mucosa

Internal

sphincter

Fat in inter-

sphincteric spacePubo-rectalis

= upper external

sphincter

N l l l l


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Normal anal canal - coronal

InternalSphincter

Puborectalis

External

Sphincter

Post Gad fat saturation T1


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Post Gad fat saturation T1

Drain in situ

ANTERIOR

POSTERIOR

UC i t


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UC - mucinous tumour

UC i t


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UC - mucinous tumour

A l l t


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Anal canal tumour


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2007 Gastroreg Lecture

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