Until this section is complete, please refer to your methodology
text:
Wilson MA (ed). Textbook of Nuclear Medicine. pages 78 to 79
and 530.
Also see Early PJ & Sodee DB (eds). Principles and Practice of
Nuclear Medicine (2nd ed). pages 520 to 522.
Thank you for your patience and understanding.
Lyle 
The
esophagus:
- is a muscular tube
about 23 to 25 cm long
- propels food from the
mouth to the stomach by peristaltic waves
- ~1 sec for liquids
and very soft foods
- ~4 to 8 sec for
solid and semi-solid foods
- is slightly narrowed as
it passes through diaphragm just above stomach
- along with muscular
layer at diaphragm, narrowing constitutes physiological Lower Esophageal
Sphincter
- LES must relax
for food to enter stomach.
Disorders that can affect
the normal motility of the esophagus include:
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Determine
time required for a small bolus of tagged liquid
to traverse esophagus.
Determine
pattern of transit for a small bolus of tagged
liquid as it traverses esophagus.
Compare with normally
expected values.
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To identify
presence of and quantify severity of esophageal motility disorders
including:
- achalasia
- scleroderma
- diffuse esophageal
spasm.
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Patient
Preparation
NPO for at least four (4) hours prior to
study.
Significant patient
cooperation is required. Explain test procedure thoroughly.
Radiopharmaceuticals
99mTc sulphur
colloid:
- ~20 to 40 MBq in 10 to
15 mL of water in a test tube
- patient sips into mouth
through a straw and swallows bolus on command
- have patient
practice procedure with water before using 99mTc sulphur
colloid.
Equipment
LFOV gamma camera
with:
- LEHR
collimator
- analyzer set for 140
keV with 15% to 20% window.
Computer
system.
Image /
Data Acquisition Parameters
Computer system set to
acquire:
- two phase dynamic study
in 128 x 128 x word mode
- dynamic phase 1: 1
frame / second for 2 minutes
- dynamic phase 2: 1
frame / 15 seconds for 8 minutes.
Patient positioned supine
(eliminates gravity as a factor) with head turned to one side:
- nose to stomach in
field of view
- once acquisition is
started, radiopharmaceutical is sipped through a straw and swallowed as a bolus
on command
- patient "dry swallows" on command every 15 seconds as study
progresses.
Display /
Image Processing
A composite image is
created and ROIs are produced around:
- initial activity in
mouth
- represents "total" activity
- esophagus
- if a more detailed
regional analysis of transit is desired, ROIs may be created around proximal,
middle, and distal esophagus
- stomach
- right chest
Data may be reviewed in
cine mode.
Time - Activity curves are
created for the ROIs.
For esophageal ROI(s),
esophageal emptying is calculated as a percentage of the maximum
activity:
- % Emptying =
((Emax - Etime) / Emax) x 100
- where:
- Emax
is the maximum activity (in mouth at beginning of study)
- Etime is the activity at time "t" during the
study.
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Normal esophageal transit
should demonstrate a smooth progression of the bolus through each region of the
esophagus.
Esophageal emptying
calculations should demonstrate:
- ~90% clearance of
tracer by 30 seconds (second dry swallow)
- >95% clearance by 10
minutes (end of dynamic acquisition).
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The most significant
technical difficulty is obtaining good patient compliance. This is improved by
careful explanation of the study and with practice administering the oral
99mTc sulphur colloid bolus.
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Assessment of esophageal
motility is best performed with radiographic procedures (static and
dynamic).
Nuclear mecicine
procedures permit a quantitative
assessment.
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Images of esophagus are
acquired in the anterior projection at the initial swallow and then every 15
sec with each "dry swallow" for the next 10 min. Individual images are shown
for the initial swallow and fourth, eighth, sixteenth, thirty-second, and
fortieth swallows. Images are acquired on-line, stored on computer, and later
analyzed.
NOTE: Following initial swallow in normal subjects, no activity
is seen within esophagus.
Illustration of the
esophageal region of interest when esophageal transit is measured as a global
function.
Three equal-sized
rectangular regions of interest are used to generate time - activity curves
through each of three esophageal regions.
Time -activity curves of
percent transit versus the number of swallows for 10 min.
Anterior views of the
esophagus in a patient with achalasia. Note the poor passage of liquid bolus
within the esophagus (retention) despite repeated "dry swallows". Percent
transit is illustrated in the previous image.
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Pathology
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