Nuclear Medicine Technology

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 (2^nd ed). pages 520 to 522.

Thank you for your patience and understanding.

Lyle

Review of Pathology

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:

• Achalasia
• Diffuse Esophageal Spasm
• Scleroderma
• Systemic Lupus Erythematosus (SLE).

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Principle

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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Indications

To identify presence of and quantify severity of esophageal motility disorders including:

• achalasia
• scleroderma
• diffuse esophageal spasm.

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Procedure

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
  • serves as background.

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 = ((E_max - E_time) / E_max) x 100
  • where:
    • E_max is the maximum activity (in mouth at beginning of study)
    • E_time is the activity at time "t" during the study.

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Interpretation

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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Common Technical Difficulties and Artifacts

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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Other Modalities for Determining the Same or Similar Information

Assessment of esophageal motility is best performed with radiographic procedures (static and dynamic).

Nuclear mecicine procedures permit a quantitative assessment.

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Case Studies

Normal Esophageal Images

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.

Esophageal Transit - Global technique

Illustration of the esophageal region of interest when esophageal transit is measured as a global function.

Normal Esophageal Transit - Graphs

Three equal-sized rectangular regions of interest are used to generate time - activity curves through each of three esophageal regions.

Time - Activity Curves (Normal and Achalasia)

Time -activity curves of percent transit versus the number of swallows for 10 min.

Patient with Achalasia

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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Specific References

Pathology

Texts

Internet URL's

Esophageal Disorders in The Merck Manual of Diagnosis and Therapy (17th edition). The manual is posted by Merck & Co., Inc.

text

Procedure

Texts

Journals

Videos

Internet URL's

Radionuclide Esophagram in Nuclear Medicine Review Manual edited by Dr. Scott C. Williams

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Quiz

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