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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
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