SPARC: Simultaneous Assessment of Gastric Emptying and Motility with Contrast Enhanced Magnetic Resonance Imaging in Humans

Abstract

PurposeMagnetic resonance imaging (MRI) of the gastrointestinal (GI) tract is an emerging technique for non‐invasive assessment of gastric emptying and motility in animals and humans. However, addition of MRI contrast agents to the test meal is often required to produce high luminal contrast to facilitate image analysis. Here, we reported a recipe of a test meal that is all natural (e.g. gadolinium‐free) and safe for humans. The ingredients of the test meal all contain relatively high concentration of manganese, which allow the lumen of the GI tract to be visible inside MRI. To capture gastric emptying and motility simultaneously, we have developed a dynamic 3D imaging protocol with high spatial and temporal resolution and an image segmentation and analysis algorithm.MethodSix healthy volunteers (3 woman; age 24–31) participated in this study. All subjects were asked to fast for 12 hours. Subjects were scanned using a 3T Siemens Prisma MRI scanner using an 18‐channel body coil and a 32‐channel spine coil. Prior to meal consumption, pre‐prandial gastric volume was quantified using a 3D true fast imaging (TRUFI) with steady‐state free precession sequence under free breathing. Then the subjects were instructed to ingest 350 ml of a semi‐solid test meal (263kcal) that contains blended natural foods (i.e. pineapple, banana, blueberry, firm tofu) with a relatively high concentration of manganese. Post‐meal MRI scans were performed using a 3D Spoiled Gradient Echo Variant (VIBE) sequence under gentle breaths over a 90‐minute time course. Post‐prandial gastric volumes, as well as antral contraction frequency and amplitude of the peristaltic wave, were quantified from the dynamic 3D MRI images using a custom‐built image processing pipeline.ResultsPre‐prandial gastric volume was measured prior to test meal consumption (30.98±12.29 mL). After the subjects consumed the test meal, the presence of manganese in the meal enhanced the contrast of the gastric lumen (Fig. 1). The imaging protocol collected fast real‐time MRI scans of the stomach processing and emptying of a meal and the algorithms quantified gastric motility and emptying rate. The stomach volume decreased at a rate of 1.58±0.50 mL/min, mainly attributed to volume decrease in the fundus and the corpus (1.31±0.53 mL/min) than in the antrum (0.28±0.15 mL/min). The frequency of gastric contractions was 2.79±0.17 cycles/min, which was in line with the frequency of gastric slow wave in humans. The displacement of the luminal wall (i.e. contraction amplitude) was greater at the antrum (7.42±1.39 mm) than at the fundus and the corpus (4.52±0.25 mm), as illustrated in Fig. 2.ConclusionHere, we developed a contrast‐enhanced gastric MRI protocol to non‐invasively monitor gastric emptying and motility in humans. Such experimental protocol was further empowered by advanced image analysis to enable comprehensive assessment of gastric functions and physiology. In summary, the proposed method may become a reliable standard to guide diagnosis and treatment of gastric disorders in humans.Support or Funding InformationNIH SPARC OT2OD023847Example gastric MRI images of the stomach distended with the test meal. The contrast of the gastric lumen was significantly enhanced due to the presence of manganese in the meal.Figure 1Mapping amplitude of gastric contractions on the luminal wall. The displacement of the luminal wall was greatest at the antrum, followed by the corpus, and smallest at the fundus.Figure 2