Assessment of gastric fundic accommodation using physiologic segmentation of the stomach with dynamic antral contraction scintigraphy (DACS) rather than anatomic division: establishing normal values

Objectives: Assessment of gastric fundic accommodation (FA) during routine gastric emptying scintigraphy (GES) is being increasingly recognized as important for potentially explaining patient symptoms of dyspepsia and for targeting therapy. The fundus undergoes receptive relaxation and accommodation and then generates sustained pressure to move solids into the antrum. In response, the antrum then performs rhythmic contractions to promote gastric emptying. Currently, measurement of FA during GES is typically performed by anatomic division of the stomach into proximal vs distal halves or thirds. Goals of this study included: 1) Develop software to perform semiautomated Fourier analysis of dynamic antral contraction scintigraphy (DACS) to separate the antrum (phasic contractions) from the proximal stomach (no phasic contractions); 2) Establish normal values for FA using this method; 3) Compare measurement of FA based on DACS Fourier analysis to anatomic division of the stomach in halves.

Methods: Normal subjects (n=20, 13 male, 7 female, aged (mean±SD) 24.6±6.6 years) underwent GES using the SNMMI recommended standard solid-meal consisting of two pieces toasted bread, liquid egg white and jam with water. The egg white was labeled with 74 MBq (2mCi) Tc-99m sulfur colloid. Anterior and posterior static imaging was performed at 0, 30, 60, 120, 180, 240 min after meal ingestion. Continuous dynamic imaging (1 image/3 sec) was performed for 20 minutes after each static imaging time. MatLab semi-automated software was developed to divide the stomach into proximal and distal halves along its longitudinal axis and to also analyze DACS using Fourier amplitude and frequency analysis. FA was assessed by measuring intragastric meal distribution (IMD) in the image immediately post meal ingestion (t=0 min) (IMD-0). IMD-0 is calculated as the ratio of counts in the fundus divided by the total stomach. IMD-0 was calculated by both dividing the proximal stomach (fundus) vs distal stomach in halves (IMD-0(½)) and by segmenting the fundus from the antrum by defining the antrum by those pixels demonstrating phasic antral contractions (IMD-0(AC)) utilizing Fourier analysis. Results: Antral contractions started 11.2±12.6 min (mean±SD) after meal ingestion. The antral contractions originated in the mid-body of the stomach 40.3±11.0% from distal to proximal stomach along the longitudinal axis. Antral contraction frequency, 3.28±0.74 contractions per minute, and ejection fraction, 29.4±13.4%, both peaked at 30 min. The normal mean values for IMD-0(½) = 0.75±0.15 vs IMD-0(AC) = 0.85±0.14 (p = 0.004).

Conclusions: In assessing fundic accommodation using IMD-0, Fourier analysis can be used to segregate the gastric antrum from the fundus based on antral phasic contractions. This assessment is more physiologic compared to simple anatomic division of the stomach. The mean normal value for IMD-0 obtained based on antral contractions is significantly higher than that using anatomic division of the stomach in halves due to the larger area of the fundus based on the physiologic DACS method. This new method and new normal values for measuring fundic accommodation response by DACS will require study in a larger patient population to determine if DACS derived measurement of FA better associates with other physiologic tests of fundic accommodation and helps determine which patients will benefit from targeted therapies to improve patient symptoms associated with abnormal fundic accommodation.