HEPATOBILIARY
SYSTEM
Clinical indication
1. Functional
assessment of the hepatobiliary sytem
2. Integrity
of the hepatobiliary tree
a. Evaluation
of suspected acute cholecystitis
b. Evaluation
of suspected chronic biliary tract disorders
c. Evaluation
of common bile duct obstruction
d. Detection
of bile leak
e. Evaluation
of congenital abnormalities of the biliary tree
Patient preparation
1. Patient
should fast 2–4 hours before tracer administration
2. Narcotics,
sedatives or other drugs that relax the sphincter of Oddi, the muscle between
the common bile duct and the duodenum, should be continued for 6–12 hours prior
to hepatobiliary imaging.
Acquisition parameters
1. Images
are acquired at 1 min / frame for 1 hour
2. After
1 hour, obliques and lateral projections should be obtained to delineate bowel
activity or other structures such as kidneys.
Interventional procedure
1.
Sincalide
pretreatment
a. Sincalide
is a synthetic form of cholecystokinin (CCK) given in a dose of 0.01–0.02
µg/kg infused over 3 minutes, 30–60 minutes prior to tracer injection.
b. Used
for patients who have fasted for prolonged periods (>24 hours)
c. Used
for patients who are on hyperalimentation (the gallbladder is full at the
beginning of imaging)
2.
Morphine
sulfate
a. Morphine
causes contraction of the sphincter of Oddi which in turn increases the
pressure in the bile ducts.
The increased
pressure forces tracer through the cystic duct, if it patent, into the
gallbladder.
b. Non–visualization
of the gallbladder following administration of morphine increases the
likelihood that the patient has acute cholecystitis.
c. By
using morphine, the length of the study is shortened and the specificity of the
findings is increased.
3.
Phenobarbital
a. In
jaundiced infants, in whom biliary atresia is suspected, pretreatment with
Phenobarbital, 5 mg/kg/day is usually given orally in two divided doses daily
for a minimum of 3–5 days prior to the hepatobiliary imaging study.
b. Mebrofenin
is preferred for biliary atresia
Image findings
1. Normal
findings
a. Visualization
of the tracer within the hepatic ducts and gallbladder occurs by 15–30 minutes.
The gallbladder is well visualized by 45–60 minutes and tracer activity appears
in the small intestine by 30 minutes after injection.
2. Acute
cholecystitis
a. Persistent
gallbladder non–visualization post–morphine or on the 3–4 hours delayed image.
b. Pericholecystic
hepatic band of increased activity (the rim sign) is often associated with
severe phlegmonous / gangrenous acute cholecystitis, a surgical emergency is
needed.
3. Chronic
cholecystitis
a. Reduced
gallbladder ejection fraction is responsible to sincalide.
4. Common
bile duct (CBD) obstruction
a. Partial
common bile duct obstruction is there is delayed biliary to bowel transit
beyond 60 minutes
b. High
grade CBD obstruction should be suspected when neither the intrahepatic biliary
tree, gallbladder on the small bowel are seen within 18 –24 hours post
injection
5. Biliary
leak
a. When
tracer is found in localization other than liver, gallbladder, bile duct, bowel
or urine.
6. Biliary
atresia
a. Demonstration
of the tracer in the bowel.
Sources of error
1.
False positive
error:
a. Insufficient
fasting (<2 – 4 hours)
b. Prolonged
fasting (>24 – 48 hours)
c. Severe
hepatocellular disease
d. High
grade common bile duct obstruction
e. Severe
intercurrent illness
f.
Pancreatitis
g. Rapid
biliary–to–bowel transit
h. Severe
chronic cholecystitis
i.
Previous cholecystectomy
2.
False negative
error:
a. Bowel
loop simulating gallbladder
b. Acute
calculous cholecystitis
c. Presence
of “dilated cystic duct” sign simulating GB
d. Bile
leak due to GB perforation
e. Congenital
anomalies simulating gallbladder
Radiopharmaceuticals used:
1. Disofenin
(DISIDA–2,6 diisopropylacetanilido iminoacetic acid)
2. Mebrofenin
(BRIDA–bromo–2,4,6–trimethylacetanildo iminoacetic acid)
3. The
usual dose is 1.5 to 5.0 mCi for adults or higher in case of hyperbilirubinemia
LIVER AND
SPLEEN IMAGING
Clinical indication
1. Liver
and Spleen Imaging
a. For
suspected focal nodular hyperplasia of the liver
b. Assess
the function of the reticuloendothelial system in patient with suspected liver
disease.
2. Liver
Blood Pool Imaging
a. Highly
specific for cavernous hemangiomas of the liver of up to >2 – 3 cm.
3. Hepatic
Perfusion Imaging
a. Useful
in demonstrating hepatic artery catheters used to infuse chemotherapeutic
agents.
4. Splenic
Imaging
a. In
children, to rule out congenital asplenia or polyspenia
b. In
adults, whose thrombocytopenia has been previously treated with splenectomy
c. For
characterizing an incidentally noted mass as functionally noted mass as
functional splenic tissue.
Radiopharmaceuticals used
1. Liver
and Spleen imaging – 5–10 mCi sulfur colloid
2. Liver
Blood Pool Imaging – 20–25 mCi Tc99m RBC
3. Hepatic
Artery Perfusion Imaging – 1–3 mCi Tc99m MAA
4. Splenic
Imaging – 1–3 mCi Tc99m heat damaged RBC’s
Image acquisition
1. Liver
and Spleen Imaging
a. Imaging
is done after 10–15 minutes post–injection at 500k to 1M counts
b. Obtain
anterior and posterior images with oblique and laterals
c. Breath
holding views may sometimes help clarify ambiguous findings by eliminating
image degradation by respiratory motion
d. Lead
markers should be placed as imprints to measure the liver
2. Hepatic
Blood Pool Imaging
a. Images
at 1 seconds/ frame for 60 seconds should be obtained on the site of the lesion
previously located by MRI or CT.
b. Blood
pool images and anterior, posterior, oblique and laterals should be acquired 1–2
million counts
c. 45–180
minutes post–injection delayed images should be acquired
d. SPECT
should be done if 0.5 cm lesion is suspected
3. Hepatic
Perfusion Imaging
a. Tc99m
MAA should be infused very slowly at a measure rate through the catheter.
b. Imaging
is done immediately at 500k – 1million counts
c. Imaging
of the lung is required to identify intrahepatic arteriovenous fistulas
4. Splenic
Imaging
a. Imaging
is done 30–120 minutes after injection of the tracer.
b. If
ectopic splenic tissue is a concern, the entire abdomen should be imaged
c. If
the patient has had prior trauma that may have resulted in a diaphragmatic
rupture, the chest should also be imaged.
C–14 UREA BREATH
TEST
Clinical indication
1. Detection
of the presence of Helicobacter pylori in the stomach
Patient preparation
1. Patient
should be fasting for 6 hours before the test
2. No
medication from the following before the test
a. Antibiotics
–
30 days
b. Sucrasulfate
and omeprazole – 7 days
c. Histamine
H2 receptor antagonist – 24 hours
(ramitidine,
nizatidine, antacids)
Radiopharmaceutical used
1. C–14
urea
a. A
pure beta–emitter with a physical half–life of 5730 years
b. It
has a maximum energy of 160 keV
c. Because
of the beta emissions, it has to be counted in a liquid scintillation counter
d. Can
be purchased in a lyophilized form
e. Dosage
is 0.001 – 0.01 mCi orally
Procedure of the test
1. The
lyophilized C–14 urea is reconstituted with sterile water to the desired
activity concentration. It has to be refrigerated to prevent
thermodecomposition or bacterial contamination.
2. A
breath collection vial composed of exact concentration of hyamine in methanol
is used as CO2–trapping solution. A pH indicator should be added
prior to sampling.
3. Breath
sample collection
a. Patient
should be asked to brush their teeth or remove dentures to prevent
contamination of normal flora.
b. The
patient is asked to take a deep breath and hold it for approximately 10 seconds
and then exhale it through a straw until pH indicator changes color.
c. The
patient may also be asked to exhale through a mylar balloon and later expelled
in a trapping solution. (Alternate collection technique)
d. The
patient then receives an oral dose of C–14 urea (20–30 ml). The patient has to
clean his / her teeth and gums to prevent contamination.
e. Breath
samples are then collected into separate vials at 5–10 minute intervals for 20–30
minutes.
f.
10 ml of scintillation fluid is
added to each vial immediately after breath collection.
4. Breath
sample counting
a. All
timed breath samples, background, sample, standard and C–14 quenched standards
are counted for 5 – 10 minutes in a liquid scintillation counter.
5. Calculation
% dose exhaled
= A
x B x 100
(C
x D) x (E x F)
Where:
A = dpm of
sample
B = patient
weight in kg
C = dpm of
standard
D = 1/fraction
of dose in standard
E = volume (ml)
of trapping solution
F = concentration
of trapping solution (mmol/ml)
MECKEL’S
DIVERTICULUM
1. A
Meckel’s Diverticulum is an outpouching of the intestine, usually located in
the distal ileum. It is a remnant of an embryonic duct at the point where the
yolk sac is attached to the intestine of the fetus. It is formed when the duct
fails to close completely during fetal development.
2. The
diverticulum may contain gastric mucosa. Just as the gastric mucosa lining of
the stomach secretes hydrochloric acid and pepsin so does the ectopic gastric
mucosa of the diverticulum.
3. Gastrointestinal
bleeding can result when the secretions of the gastric mucosa cause ulceration
of the adjacent normal intestine. Patient may experience lower abdominal pain
as well as GI bleeding.
Radiopharmaceutical used
1. Tc99m
pertechnetate, 5 mCi
Clinical procedure
1. The
patient should be fasting for 6 hours and should not have receive any laxatives
or diagnostic test that might irritate the intestinal tract for at least 3 days
prior to imaging.
2. Pentagastrin
stimulates gastric secretions, thereby increasing pertechnetate secretion in
the stomach and diverticulum. It is administered subcutaneously 15 minutes
before the tracer.
3. Cimetidine
may be administered as it helps retain pertechnetate in the gastric mucosa. The
patient receives cimetidine orally every 6 hours for 24 hours before imaging.
Imaging
1. Imaging
should be acquired 5–10 minute intervals for 1 hour with the camera centered
between the xyphoid and symphysis pubis.
Image findings
1. Meckel’s
diverticulum containing functioning gastric mucosa should be visualized by 10–15
minutes after injection, at the same time tracer activity appears in the
stomach. It is usually seen in the right lower quadrant but can appear anywhere
in the abdomen
GASTROINTESTINAL
BLEEDING LOCALIZATION
Radiopharmaceutical used
1. Tc99m–sulfur
colloid – is best used in cases of active bleeding, since it leaves the blood
pool rapidly and maybe cleared before the next bleeding episode, but bleeding
in the upper quadrant may be obscured by sulfur colloid.
2. Tc99m–labeled
red blood cell, 25 mCi – better choice when the bleeding is intermittent since
the tracer remains in the blood pool for a long period and allows delayed
imaging.
Clinical procedure
1. Rapid
sequential images are acquired as the tracer is administered. Following the
dynamic study, short static images are obtained at interval, up to 1 hour
following injection.
2. If
Tc99m red blood cells were used, delayed imaging may be obtained at intervals
but will be normally taken up by liver, spleen, abdominal vessels, kidneys,
bladder, genitals and stomach.
3. If
Tc99m sulfur colloid were used, area of active bleeding is demonstrated within
the first 5 minutes of imaging and may become more intense as background
activity decreases.
GASTROESOPHAGEAL
REFLUX
Background
1. In
adults, recurring or continual reflux of gastric or duodenal contents into the
esophagus can lead to esophagitis and dysphagia
2. In
infants, chronic reflux may cause failure to thrive and aspiration pneumonia
Clinical procedure
1. For
adults, 300 µCi Tc99m sulfur colloid is mixed with 150 ml orange juice and 150
ml 0.1 N dilute hydrochloric acid and administered orally.
2. For
infants, the tracer is mixed with infant formula and administered through a
nasogastric tube or orally through a baby bottle.
3. Imaging
begins after tracer administration with stomach, esophagus and lungs included
in the field of view.
4. Serial
images are obtained as varying amounts of pressure are applied to the abdomen
using abdominal binder.
5. Delayed
images of the lung field up to 24 hours after tracer administration are useful
for detecting intermittent reflux, which leads to aspiration of the tracer into
the lung.
Image findings
1. Esophageal
reflux is confirmed by presence of activity in the esophagus or in the lungs.
GASTRIC
EMPTYING
Background
Abnormal gastric emptying rates can be
caused by disease or surgical procedures. Patients experience nausea, vomiting,
weight loss or abdominal fullness or distention.
Radiopharmaceuticals used:
1. Tc99m
sulfur colloid, 1 mCi
2. Indium–111
DTPA
Clinical procedure:
1. 8
hours fasting before the procedure
2. Meal
consists of solid and liquid with radiopharmaceutical should be consumed within
5 minutes.
3. Imaging
is acquired at 15 minutes intervals for 2 hours.
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