Nuclear Medicine Gastrointestinal Studies Lecture

Practice vocabulary flashcards covering gastric emptying protocols, esophageal motility and reflux evaluations, and gastrointestinal bleeding scintigraphy based on lecture notes.

Standard Gastric Emptying Meal

A standardized semi-solid meal consisting of two scrambled eggs mixed with Technetium sulfur colloid, toast, and water, which the patient must ingest within 5 minutes.

Normal Gastric Emptying Values

The standard diagnostic criteria where at least 60% of the meal empties by 2 hours ($\le 40\%$ remains), less than 30% remains in the stomach at 3 hours, and less than 10% remains at 4 hours.

Geometric Mean

A mathematical combination of anterior and posterior stomach counts used in gastric emptying analysis to correct for attenuation as food moves from posterior to anterior during digestion.

Left Anterior Oblique (LAO) View

The single-camera imaging position used as an alternative to the geometric mean to minimize the effect of anterior-to-posterior tracer transit in the stomach.

Reglan (Metoclopramide)

A prokinetic drug administered as a $10\,\text{mg}$ IV dose slowly over 1 to 2 minutes during a gastric emptying exam to determine if pharmacologic intervention restores a normal emptying rate ($T_{1/2} < 90\,\text{minutes}$).

Pheochromocytoma

An adrenal gland tumor that places a patient at high risk of severe hypotension, shock, and death if Reglan (metoclopramide) is injected too rapidly.

Dual-Isotope Gastric Emptying Study

An exam that simultaneously measures solid and liquid gastric emptying by administering Tc-99m sulfur colloid in scrambled eggs alongside Indium-111 DTPA mixed into drinking water.

Achalasia

An esophageal motility disorder characterized by a failure of normal muscular peristalsis and contraction, causing radioactive tracer to pool and linger in the esophagus (especially the lower third).

Barium Swallow Study

A fluoroscopic radiographic exam where a patient swallows barium contrast from a small cup, providing high-resolution visualization that has largely replaced nuclear medicine esophageal transit studies.

Esophageal Manometry

A diagnostic procedure where a tube lined with pressure sensors is placed down the esophagus to directly measure muscular pressures during swallowing.

Esophageal Transit Protocol

An exam requiring the patient to ingest $150\text{--}500\,\mu\text{Ci}$ of Technetium sulfur colloid in about $15\,\text{mL}$ of water, followed by dry swallows every 15 seconds for 4 to 10 minutes.

Normal Esophageal Transit Benchmark

The clearance of at least 90% of esophageal radioactivity after 8 swallows (2 minutes), with complete clearance expected within 4 to 10 minutes.

Adult Gastroesophageal Reflux Protocol

An exam where a supine patient consumes $300\,\mu\text{Ci}$ of Technetium sulfur colloid in $150\,\text{mL}$ of orange juice acidified with dilute hydrochloric acid, followed by incremental inflation of an abdominal binder up to $100\,\text{mm\,Hg}$.

Gastroesophageal Reflux Normal Value

A quantitative measurement where less than 3% of stomach activity refluxes into the esophagus (abnormal is considered greater than 10%).

Pediatric Gastroesophageal Reflux Study

An imaging test for infants with chronic aspiration pneumonia where $150\,\mu\text{Ci}$ of Technetium sulfur colloid is added to $90\text{--}150\,\text{mL}$ of formula in a lead-shielded bottle to check for activity aspirating into the lungs over 24 hours.

Barrett's Esophagus

A precancerous esophageal condition caused by chronic acid reflux where normal squamous epithelium is repeatedly injured and replaced by metaplastic tissue.

GI Bleed Study Bleeding Threshold

The minimal internal bleeding rate detectable by a nuclear medicine GI bleed scan, which can detect hemorrhages as low as approximately $2\,\text{mL/hr}$.

Hematocrit

The percentage of total blood volume occupied by cellular elements (red blood cells, white blood cells, and platelets), typically measuring 40% to 45% in healthy adults.

Technetium Sulfur Colloid (GI Bleed)

A radiopharmaceutical for GI bleed imaging that is cleared by the liver and spleen within 5 to 10 minutes, requiring the patient to be actively bleeding at the exact time of injection.

Tagged Red Blood Cells (Tc-99m RBCs)

A radiopharmaceutical preparation that remains within the intravascular space, allowing continuous or intermittent imaging of gastrointestinal bleeding for up to 24 hours.

Stannous Ion ($\text{Sn}^{2+}$)

The chemical reducing agent (commonly sourced from reconstituted pyrophosphate [PYP] kits) that enters red blood cells to reduce pertechnetate and lock it intracellularly.

UltraTag Kit

An in vitro commercial labeling kit recommended by the Society of Nuclear Medicine that achieves approximately 90% red blood cell labeling efficiency.

Free Pertechnetate ($\text{TcO}_4^-$)

Unbound technetium that concentrates in the gastric mucosa (secreting into bowel lumen) and clears through the urinary bladder, producing false-positive artifacts during GI bleed evaluations.

Large-Bore Needle (18 to 20 Gauge)

The recommended IV gauge for administering radiolabeled red blood cells to avoid shearing the cells and causing unwanted splenic uptake.