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NM 4203Scanning & Imaging

Gastrointestinal System

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Alimentary Canal

Mouth Pharynx Esophagus Stomach Small intestine Large intestine (colon)

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Accessory Organs

Salivary glands Pancreas Liver Gallbladder

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Stomach Anatomy & Physiology

Three Regions:– Fundus : controls liquid emptying– Corpus (body)– Antrum : controls solid emptying

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Gastric Emptying Study

Indications– Nausea, vomiting– Weight loss– Abdominal bloating

Mechanical causes– Ulcer, tumor, post-radiotherapy, pyloric stenosis,

post-surgical Nonmechanical causes

– Diabetes, hypo or hypertension, neuropathy, gastroparesis, anorexia, amyloidosis

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Gastric Emptying Study

Each lab must standardize meal type and size.

Solid phase could be meat, chicken liver, eggs, french toast, etc (99mTc Sulfur Colloid)

Liquid phase could be water, orange juice, apple juice. (111In DTPA)

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Gastric Emptying Study

Patient fasting for at least 8 hrs. Medium energy collimator (if doing

liquid phase with In111DTPA) Should eat meal within 5 minutes,

followed by liquid.

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Liver Anatomy & Physiology

Right upper quadrant of abdomen Right lobe generally larger than left Composed of:

– Kupffer cells– Hepatocytes

• Conversion of bilirubin to bile

Spleen: not part of the GI system

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Liver – Spleen imaging

99mTc Sulfur Colloid or 99mTc Albumin Colloid

Can do a flow (looking at vascularity of some defects)

No pt. prep Static images 15 min. after injection

– Anterior, RAO, Rt lat, RPO, posterior, LPO, Lt lat, LAO

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Liver – Spleen Colloid Image

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Liver Hemangioma

99mTc – Labeled Red Blood Cells No pt. prep Bolus 15 – 25 mCi with immediate flow

imaging Followed by pool images per facility

protocol SPECT usually 2-3 hours after injection.

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Liver Hemangioma

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Liver Hemangioma

Little or no blood flow to the lesion on early flow images

Delayed imaging usually shows increased uptake in hemangioma.

Other types of lesions will retain RBC’s, but only hemangiomas retain RBC’s for over 2 hrs.

Some consider this test to be 100% accurate for Hemangioma detection.

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Gallbladder Anatomy & Physiology Concentrates and stores bile Stimulated by fatty meal to contract and

release bile into the duodenum Bile is useful to breakdown fats during

digestion.

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Extrahepatic biliary anatomy

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Hepatobiliary Imaging

Radiopharmaceuticals– 99mTc HIDA, 99mTc DISIDA, 99mTc Mebrofenin

Pt. should fast at least 2 hrs. before study, no more than 24 hrs.

Pain medications (opium or morphine based) should not be taken prior to imaging.

Rt. Lateral image is helpful to separate Gb (Gallbladder should be anterior to other structures)

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Acute Cholecystitis

Usually due to cystic duct obstruction Visualization of GB with

radiopharmaceutical excludes diagnosis of acute cholecystitis

No GB visualized in 4 hrs, high probability of acute cholecystitis

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Acute Cholecystitis

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Gallbladder Imaging: other medications

Cholecystokinin (CCK)– Causes gb contraction– Relaxes the sphincter of Oddi– Used for GB Ejection Fraction– Peptide hormone, naturally secreted by duodenum

Morphine– Decreases peristalsis– Constricts the sphincter of Oddi– Used when Gb is not visualized to “force”

radiopharmaceutical into the gb.

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Biliary Leak

Usually requested after surgery or trauma

Subtle leaks that may accumulate in the pelvis

May mimic a gb ~ labeled bile in the gallbladder fossa

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Intestine anatomy & physiology

Small intestine– Duodenum, jejunum, and ileum– 20 feet long– Digestion and absorption of nutrients

Large intestine – Cecum, ascending colon, transverse colon,

descending colon,sigmoid colon, and rectum.– Resorption of water

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GI Bleed Imaging

Radiopharmaceutical– 99mTc Sulfur Colloid or 99mTc –labeled

RBC’s (each facility may have different labeling method)

Bolus injection with immediate flow imaging

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GI Bleed

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Causes of GI Bleeding

Diverticular disease Angiodysplasia Neoplasms Inflammatory bowel disease

Not uncommon to never find a reason

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Meckel’s Diverticulum

Common cause of GI bleeding in children.

Most are located

in the ileum 99mTc Pertechnetate

~ concentrates in

gastric mucosa

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Meckel’s Diverticulum

Painless rectal bleeding More common in children Some Meckel’s do not contain gastric

mucosa, won’t show on scan Glucagon – given i.v. 10 minutes after

Tc injection or Zantac given i.v. prior to Tc injection– Decrease small bowel activity

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Schilling Test

GI absorption of vitamin B12

57Co vitamin B12 given orally Followed by IM injection of non-labeled

vitamin B12 (saturates the liver) Urine collected for 24 hrs.