Oesophageal Transit Scintigraphy

6.2.1 Radiopharmaceuticals

• ^99mTc-sulphur colloid

6.2.2 Uptake mechanism / biology of the tracer

Because there is no consensus on standardized Oesophageal Transit Scintigraphy (ETS), radioactive test-meals could be either semi-solid (50 mL of apple purée) or solid (1g of pâte) labelled respectively with 50 MBq (1MBq/mL) or 37 MBq of ^99mTc-sulphur colloid. Ten to 30 mL of water containing 3,7 to 37 MBq of ^99mTc-sulphur colloid could also be used.

The quality of the oesophageal transit is analysed after a single swallow of the meal (bolus transit). Multiple dry swallows following the single swallow of the meal could also be used to optimize oesophageal transit and to quantify total oesophageal emptying.

The examination is repeated in the upright and in the supine position. The same test-meal must be prepared for all patients and for repeated evaluations.

6.2.3 Indications

• Although the presence of a manometric tube itself may affect oesophageal transit, manometry is considered the gold standard for diagnosis of oesophageal transit disorders, in particular achalasia, scleroderma, and diffuse oesophageal spasm.
• Secondary oesophageal motility defects such as systemic sclerosis, myasthenia gravis and polymyositis.
• Gastro-oesophageal reflux (primary or following antireflux treatment).
• ETS could provide direct evaluation of peristalsis whereas the pressure waves registered by manometry provide only an indirect measure.

6.2.4 Contra-indications

• Pregnancy is a relative contra-indication.
• It is not recommended to interrupt breast feeding although an interruption of 4 h during which one meal is discarded can be advised to be on the safe side [3].

6.2.5 Clinical performances

• Safe, non-invasive and highly sensitive method.
• Minimal radiation exposure.
• The major indication is to diagnose and quantify oesophageal motility disorders:
  • Sensitivity 95% and Specificity 96% for detecting achalasia and scleroderma oesophageal motility disorders.
  • Lower performances for non-specific oesophageal motility disorder.
• Compared with manometry, ETS has similar sensitivity for detecting primary as well as non-specific oesophageal motility disorder.
• The ability of ETS to quantitate total oesophageal emptying is useful for assessing response to therapy in achalasia.

6.2.6 Activities to administer

For adults, the recommended administered activity ranges from 37-50 MBq.

In paediatric nuclear medicine, the activities should be modified according to the EANM paediatric dosage card (https://www.eanm.org/publications/dosage-calculator/). The minimum recommended activity to administer is 10 MBq.

6.2.7 Dosimetry

The effective dose per administered activity is [3]: ^99mTc-sulphur colloid: 9.1 µSv/MBq

The range of the effective doses for the suggested activity (normal liver condition) is 0.3-0.5 mSv.

Caveat

“Effective Dose” is a protection quantity that provides a dose value related to the probability of health detriment to an adult reference person due to stochastic effects from exposure to low doses of ionizing radiation. It should not be used to quantify the radiation risk for a single individual associated with a particular nuclear medicine examination. It is used to characterize a certain examination in comparison to alternatives, but  it should be emphasized that if the actual risk to a certain patient population is to be assessed, it is mandatory to apply risk factors (per mSv) that are appropriate for the gender, the age distribution and the disease state of that population."

6.2.8 Interpretation criteria/major pitfalls

Normally, nearly the entire meal transits through the oesophagus toward the stomach after the first swallow. Transit time is less than or equal to 30 sec.

Comparison of repeated measurements of transit time is made.

Direct visualization of the dynamics of swallowing and demonstration of transit disorders such as oesophageal level of bolus retention or gastro-oesophageal reflux are performed.

6.2.9 Patient preparation

The test should be performed in the morning after an overnight fast (at least 6 h).

Prokinetics should be discontinued for 3 days prior to the investigation. Unless the clinical query is oesophageal motility under prokinetic treatment.

6.2.10 Methods

The examination is repeated with the patient in the upright and/or in the supine position.

The same test-meal must be prepared for all patients and for repeated evaluations.

The test-meal is ingested in a single swallow followed by repetitive swallows (bolus or dry swallows).

Dynamic images of 0.5 sec each are recorded immediately after the bolus swallow for up to 30 or 60 sec, generally in anterior view, followed by images of 30 to 60 sec up to 10 min.

Time Activity Curves (TAC) are generated by considering the total oesophagus and its upper, middle, and lower thirds.

Make a composite image over time summarizing the oesophageal transit on a single image.