The Problem
More than 60 million people in the United States suffer from disorders in the gastrointestinal (GI) tract that disrupt food digestion, nutrient absorption, and drug intake. These disorders not only compromise a person’s productivity and quality of life but also create a medical burden of more than 100 billion dollars every year. To evaluate myriad GI disorders, gastroenterologists have been working with invasive and low-resolution techniques that are not ideal for detecting dysfunctions in the GI tract.
Figure 1. A new MRI technique helps scientists to understand how the stomach responds to nutrients and therapies, which could offer more precise treatment for digestive disorders.
The Solution
At Purdue University, we have developed a new generation of diagnostic tools based on magnetic resonance imaging (MRI). Compared to current techniques that only offer 2 dimensional, static images of the GI tract, the Purdue MRI-based tool provides an all-in-one solution to creating images and reconstruction of 3D GI anatomy, movement, and functioning in real-time with a high-resolution view of organ tissues (1). MRI is non-invasive and is thus a highly appropriate method for repeated examinations and treatment follow-ups. In addition, the technique is applicable to both animals and humans, which helps enhance treatment development.
Figure 2. Non-invasive assessment of gastric emptying, gastric motility, pyloric opening, and bowel movements in humans using 4D, free-breathing, contrast-enhanced MRI with a naturalistic food-based meal. (Watch the full video here)
Impact
Figure 3. MRI technique can detect differences in stomach function between healthy controls and patients with gastroparesis.
Pilot studies at Indiana University School of Medicine on 4D MRI of gastroparetic humans (who have slower stomach emptying) suggest two stomach disorders: (a) impaired accommodation of the proximal stomach, and (b) distension of the distal stomach.
Electroceutical therapies for GI disorders
The MRI tool enables researchers and clinicians to observe how different parts of the GI tract respond to electrical nerve stimulation over time and helps treat chronic GI malfunctions in an individual (2,3). In the two referenced animal studies, we stimulated the left cervical vagus nerve and used MRI to monitor the effects of stimulation on gastric emptying and motility. Being able to observe the stimulatory effect in real time and, importantly, non-invasively, allows the adjustment of stimulation parameters (e.g., intensity, frequency, duration, etc.) on the fly without disturbing ongoing physiology.
Figure 4. The effect of vagus nerve stimulation on gastric emptying in rats from our earlier animal studies (— outline represents initial volume). Videos are available: Without VNS or With VNS
Cervical vagus nerve stimulation (VNS) significantly enhances the rate of gastric emptying in rats as illustrated by a greater decrease in 3D gastric volume.
The new imaging tool is expected to become a standard in the industry and clinic for assessing GI functions in various health conditions or following different treatments. The MRI-guided neuromodulation technique paves the way for a more precise and individualized treatment than drugs or dietary therapies.
