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Intended learning outcome. The student should learn at the end of this lecture principles of G astrointestinal Radiology. GASTROINTESTINAL RADIOLOGY. Topics to be covered. 1. Liver Lesions – Haemangioma and HCC 2. CT Colonography 3. Small bowel - CT, MRI or fluoroscopy?
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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
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
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
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
Incomplete air column -Excess fluid Supine Prone Can rotate image volume to view as a Ba enema in 3D
Ileo-caecal valve Caecal pole Arrow points To caecum Residual tagging
Dirty Caecum- not fully open on supine or prone views 54 yr Recomm optical colonoscopy
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
Follow-throughtime-consumingflocculationStrictures may be hiddenIs superseded by other tests
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
Cutaneous fistula Post Gadolinium T1 fat sat
Normal FAT SATURATION
Normal anal canal - sagittal Puborectalis Internal sphincter Subcutaneous External sphincter
Normal anal canal - axial at PR mucosa Internal sphincter Fat in inter- sphincteric space Pubo-rectalis = upper external sphincter