Imaging the GI tract

Introduction

•  The GI tract is one of the most complex organs in the body

•  It is uni-directional •  It has a very complex immune system •  There are more neurones in the gut than

the brain

What can go wrong •  Movement

–  Too fast –  Too slow –  Not at all

•  Congenital –  Atresia –  Fistulae –  Ectopic tissue

•  Malabsorption

What can go wrong

•  Infection •  Inflammation •  Leak •  Bleed •  Trauma •  Tumour

–  Benign –  Malignant

Why functional imaging

•  A functional organ should be imaged functionally

•  NM offers quantifiable and reproducible results

•  Other radiological techniques involve multiple images and often high radiation dose

•  Often very simple but underused

What do we cover

•  The GI Tract includes developmentally the following – Salivary glands – Gut from mouth to anus – Biliary tract – Pancreas – The renal tract – The lungs

Starting our journey

Lets follow this lot

Salivary gland

•  Can be inflammed – sarcoid

•  Can have duct obstruction – Tumour – Stone

•  Most common tests – Ga-67 citrate – Salivary scintigraphy

Ga-67 in sarcoid

•  Disseminated granulomatous disease

•  Salivary glands frequently involved

•  Can be biopsied •  Imaged with Ga-67

citrate

Salivary gland scintigraphy •  Indication •  Dry mouth •  Pain in salivary glands especially with

silalgogue (lemon juice) •  Commonly stones but could be due to

tumour •  Also inflammation reducing uptake

Salivary gland scintigraphy •  Use of up to 700MBq of Tc-99m

pertechnetate •  Anterior image •  Dynamic 1 second frames for 60 seconds

and the 10 second frames for 30 minutes statics may also be taken

Salivary gland scintigraphy •  Looking at uptake into glands •  Clearance from gland •  If no movement of tracer from salivary gland(s)

by 15 minutes give silogogue (such as lemon juice)

•  Draw ROIs over the sub-mandibular and parotid glands

•  Draw time/activity curves for each gland

Summary of results

Pathology Flow Uptake Washout

Tumour Normal Reduced Normal

Cyst Reduced Reduced Reduced

Sjorgren’s Reduced Reduced Normal

Sarcoid Reduced Reduced Increased

Stone Reduced Normal Reduced

Normal salivary scintigraphy Lemon juice

Left sided tumour Lemon juice

The osephagus

•  Tube into stomach •  Can be affected by tumour •  Also neurological disease •  Inflammatory disease

– Sjogren’s – Systemic sclerosis

•  Fistula

Oesophageal cancer

•  Normally at lower end •  Locally invasive •  Often presents with dysphagia •  Risk factor hot drinks, alcohol, smoking •  Can be cured if found early

– Surgery – Radical chemoradiation

•  Staged with FDG PET-CT

Ca Oesophagus – PET staging •  Describe extent of disease •  Look for extent of disease

–  Nodal disease may be better seen with EUS –  Metastatic disease

•  Use standard classification such as TNM8 •  Supraclavicular – coeliac nodes N stage •  Outside these nodes metastatic as is other disease •  N1 2 nodes or less, N2 2-6 nodes, N3 >6 nodes •  Only N1-N2 operable

Ca oesophagus N1 staging

Use all imaging eg sagittals show extent of disease

Ca oesophagus TxN0M1

Oseophageal scintigraphy

•  Looks at transit •  Can use liquids and solids •  Liquids imparied in neurological disease •  Solids in inflammation or tumour •  Or use semi-solid

Imaging technique •  Add 20MBq to a semi-solid meal such as cooked

apple or puree baby food •  Small volume of food put into patient’s mouth by

a plastic spoon •  Patient hold food in mouth •  Camera started an patient asked to swallow •  1 second frames for 30 seconds •  Patient washes out activty with sip of water can

re-start •  Can be done erect and supine

Camera layout

As spine lies behind oesophagus there will be marked attenuation in a pure posterior image so a 30 degree RPO or LPO used

Oesophagus

Spine Camera

Displaying data

•  How to show the data in a meaningful way •  Can look at dynamic imaging •  Time activity curves difficult as multiple

perstaltic waves •  Compressed imaging used

Compressed image-Siraj

Gastro-oesophageal reflux

Stomach

•  Main studies gastric emptying •  Normally looking for poor gastric emptying

due to dysmotility •  Can look at liquid and solid or both •  Also PET-CT for gastric cancer staging

(similar to Ca oesophagus)

Gastric emptying

•  Liquids –  Tc-99m colloid milk –  In-111 chloride milk

•  Solids –  The famous chicken liver test –  Mince meat –  Egg –  Mashed potato –  Toast

Liquid In-111 DTPA

The chicken liver diet Inject chicken with Tc-99m sulphur collid

Cook liver

Feed to patient

RFH method

Mix 20MBq Tc-99m colloid with some yummy mashed potato

What can I eat?

Food Christian Jewish Hindu Islam* Just not sure

mince Yes Yes if not pork and Kosher

No Yes if not pork and Halal

Horrible

eggs Yes Sometimes Maybe Yes Disgusting

Chicken liver

Yes Yes if Kosher

No Yes if Halal Not likely

Mashed potato

Yes Yes Yes Yes At gun point

*Of course if Ramadan only at night!

What is normal

•  There is no normal •  Great variation not only between people but

within individuals •  Liquid faster than solids •  Half time should be 5-30 minutes •  Solids 14-15 minutes •  If slow gastropariesis •  If fast dumping

Barium swallow in DM

Images over 60 minutes

Time activity curves

The SNM/AGA meal

•  2 slices toast •  50g strawberry jam •  Egg white omelet •  Image at 1, 2, 3, 4 hours •  Defined normals •  Maybe too wide a normal range

Solid gastric emptying

Bilary disease

•  Atresia vs Gilberts •  Cholecystitis •  Gall bladder dysfunction •  All can be tested with HIDA imaging •  Tumours •  F-18 FDG in pancreatic cancer

Acute Cholecystitis

•  Tc-99m HIDA •  Simple test •  In Acute cholecystitis cystic duct blocked •  If no gall bladder by 60 minutes with 1st and 2nd

generation HIDAs give morphine or CCK •  Not needed with 3rd generation HIDA such as

Tc-99m mebrofenin

Whay are we not doing 10 a day!!

•  Well is some countries they do •  Need to be set up for test •  Same day or next day •  Problem as patient needs to be fasted for

4-8 hours (if more than 8 can get flase positive as GB collapsed)

•  Sensitivity 90%-US67% (Fink Bennet)

Acute cholecystits 1980

Acute cholecystitis 2010

Other conditions

•  Bile reflux •  Bile is very alkaline •  Very irritant to

stomach •  Can use HIDA if

activity in stomach then reflux causing symptoms

Inflammatory disease

•  Cholangitis can be infective post infective or spontaneous (PSC)

•  “Beeding” on HIDA •  Differential flow R-L

HIDA post transplant

•  Patients post transplant can have one of three main problems

•  Rejection •  Leak •  Ananastomotic obstruction •  Work by Kuzawinski et al BJS 1997 •  Patient only needed op if HIDA abnormal

ERCP unhelpful

Ca pancreas staged with F-18 FDG PET-CT

Moving down-small bowel

•  Meckel’s diverticulum •  GI Bleeding starts •  Absorption method •  Small bowel tumours-carcinoid •  Inflammatory bowel disease

Cell labelling

•  In-vitro •  Take 10mls blood into syringe with 500

units sodium heparin •  Incubate with stannous 30 minutes •  Add 700MBq Tc-99m pertechnetate •  Incubate 5 minutes •  Inject into patient

Imaging

•  Best to do 60x60 second images •  Remember bleeding intermittent so

bleeding sites will appear and disappear •  If blood enters gut will always go down hill

–comet tail •  Image stomach to anus (even if

endoscope negative)

Bleed in caecal carcinoma

Absorption tests

•  Not commonly needed but useful •  Se-75 SeChat looks at bile duct

malabsortion •  Give up to 400kBq Se-75 SeChat i.v. •  Set up a standard dose as well •  Image abdomen with collimators removed

with 200keV windows and 50% windows

Se-75 SeChat

•  If retention at day 7 is <10% of initial activity then patient has bile-salt malabsorption (normally in terminal ileum)

•  If retention >20% normal study •  10-20% equivocal

Whole bowel transit

•  Normally liquid •  Labelled with In-111 •  Scanning hourly for 6 hours •  Then 24 hourly till activity passed rectum •  Should be at caecum in 6 hours •  Should clear bowel 24-48 hours •  Check patient not had colectomy

Colonic transit 24 hours

Colonic transit-48 hours

Summary

•  The use of nuclear medicine in the GI tract is primarily looking at motility

•  More quantifiable than radiology •  Often low radiation dose •  Tests may take several days •  Often underused but easy to do