Gastro-Oesophageal Reflux Scintigraphy

6.3.1 Radiopharmaceuticals

• ^99mTc-sulphur colloid

6.3.2 Uptake mechanism / biology of the tracer

^99mTc-sulphur colloid is the radiopharmaceutical of choice; it is not absorbed by the pulmonary mucosa (reflux into the respiratory tract) or the gastrointestinal tract and remains stable in the acidic medium of the stomach.

There is no consensus on standardized Gastro-Oesophageal Reflux (GER) scintigraphic method. Generally, 18.5 MBq to 185 MBq (from paediatric to adult activity) of^99mTc-sulphur colloid is added to milk (infant feeding bottle) or fruit juice for a total volume of 100 to 300 mL before being ingested.

GER scintigraphy provides direct and physiologic images of GER by imaging the passage of the gastric radioactive component into the oesophagus or the pulmonary tract.

GER can also be detected with oesophageal transit and / or gastric emptying scintigraphies.

6.3.3 Indications

• Diagnostic imaging of GER is not always required and can be based on typical clinical symptoms and lead to the introduction of an adapted treatment.
• First line tests are oesophageal pH-monitoring, multichannel oesophageal intraluminal impedance testing, or combination of both along with esophagoscopy ± biopsy.
• Thus, GER scintigraphy no longer has a place in the initial management of reflux. However, it remains of interest in some situations:
  • In children, to objectify reflux into the respiratory tract. Namely, in cases of children with impaired physical development and/or with symptoms referable to the respiratory tract, i.e., recurrent infections, refractory asthma and apnoea.
  • In cases of symptoms suggestive of oesophageal reflux, after an ineffective proper treatment and negative results of the other tests.
  • In association with oesophageal transit scintigraphy and gastric emptying scintigraphy, GER scintigraphy quantifies gastric emptying duration and oesophageal transit time, evaluates motility disorders, and then allows a complete evaluation of upper GUT function.

6.3.4 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].

6.3.5 Clinical performances

• Safe, non-invasive, and highly sensitive method.
• Minimal radiation exposure.
• The performance of GER scintigraphy show large variations between centres, because the standards for this test have been poorly established. A highly variable sensitivity of 15 to 100% has been reported, and this contrasts with an excellent specificity of 81 to 100%.

6.3.6 Activities to administer

For adults, the recommended administered activity ranges from 18-185 MBq.

In paediatric nuclear medicine, the activities should be modified according to the EANM paediatric dosage card (https://www.eanm.org/publications/dosage-calculator/).

6.3.7 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 0.16-1.6 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."

6.3.8 Interpretation criteria/major pitfalls

Images must be inspected for movement prior to interpretation, and motion correction applied when indicated.

GER is defined as at least one reflux episode in the form of sharp spikes of activity emerging from the stomach to the oesophagus and/or pulmonary tract.

6.3.9 Patient preparation

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

6.3.10 Methods

Approximately 100-300 mL of the radiolabelled radioactive liquid meal is ingested, and then about 50-100 mL of non-radiolabelled water, milk, or fruit juice is ingested, thereafter, to clean up residual radioactive activity remaining in the mouth and/or oesophagus.

After ingestion of the meal, the patient lays in the supine position under the gamma camera.

Dynamic images of 15 secs each are recorded for up to 1 h leading to the acquisition of approximately 200 images in posterior view. The operator performs a cinematic playback of the images dataset for detecting gastro-oesophageal reflux.

Reflux detection can be improved by generating TACs considering the whole oesophagus as well as its upper, middle, and lower thirds and the fundus.