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Contrast enhanced magnetic resonance imaging

Lu KH, Cao J, Oleson S, Ward MP, Phillips RJ, Powley TL, Liu Z

Direct link to the publication: doi: 10.1111/nmo.13380.

Impairment of gastric function may lead to chronic conditions such as gastroparesis, obesity, or gastroesophageal reflux disorders that are often resistant to pharmacological or dietary treatments. Collectively, gastric disorders affect more than 60 million people in the US, creating a medical burden of over $97.8 billion every year. With the epidemic growth of gastric disorders, the need to rescue impaired gastric function and to combat diabetes and obesity has become notably urgent. In this regard, vagus nerve stimulation (VNS) is an emerging electroceutical therapy for remedying gastric disorders, utilizing the vagal circuitry that innervates the gastrointestinal tract. However, evaluation of the efficacy of VNS or even optimization of VNS for gastrointestinal (GI) modulation has long been impeded by the lack of comprehensive and high-throughput assessments of gastric physiology. Current assessments of gastric physiology are mostly based on radioactive imaging or involve invasive intubation, and are unsafe for repeated measurements, technically cumbersome, and/or physiologically confounding.

In our recently published work, we have quantified the modulatory effects of left cervical VNS on gastric emptying in rats using 1) a feeding protocol in which the animal voluntarily consumed a post-fast, gadolinium-labeled meal and 2) a newly developed, robust, sensitive and non-invasive imaging strategy to measure antral motility, pyloric activity and gastric emptying based on contrast-enhanced magnetic resonance imaging (MRI). Our experimental protocol is further enhanced by advanced, computer-assisted image analysis to enable a comprehensive assessment of gastric functions and physiology.

The major findings of the work is that VNS can significantly promote gastric emptying. This effect is attributed to the expansion of the pyloric ring, with notable changes in antral contraction, in terms of its amplitude but not frequency. The expansion of the pyloric ring was significantly correlated with the increased rate of gastric emptying, confirming the relationship between the two. In summary, the protocol can guide the tuning and optimizing of stimulation parameters of neuromodulation without perturbing ongoing and spontaneous physiology, and is readily translatable to clinical applications.

Journal articles:

  • [1] Lu K-H, Cao J, Oleson S, Ward P, Phillips RL, Powley TL, Liu Z., “Vagus nerve stimulation promotes gastric emptying by increasing pyloric opening measured with magnetic resonance imaging,” Neurogastroenterology and Motility, doi: 10.1111/nmo.13380, 2018.

  • [2] Lu K-H, Cao J, Oleson S, Powley TL, Liu Z., “Contrast enhanced magnetic resonance imaging of gastric emptying and motility in rats,” IEEE Transactions on Biomedical Engineering, 64(11): 2546-2554, 2017.