Mr Stefan Sam Scott Calder

BE(Hons), ME

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Doctoral Candidate - Doctor of Philosophy


Stefan Calder graduated with a Bachelor of Engineering (Honours) degree specialising in Biomedical Engineering from Auckland University in 2013. He went on to complete his Master of Engineering in Bioengineering at the Auckland Bioengineering Institute in 2015.

Stefan is now working towards his doctorate. His research focus is on the mathematical modelling of gastrointestinal electrophysiology, with specific regard to the characterisation of the relationship between the gastric electrical activity and the electrogastrogram.


Research | Current


An Experimental-Theoretical Analysis of the Forward Problem of Electrophysiology

Contraction of the stomach, also known as gastric motility, is an important part of digestion. One of the major regulators of gastric motility is an electrical activity termed slow waves. The accurate analysis of gastric slow wave is presently limited to invasive recording techniques.

Through the development of high-resolution (HR) electrode arrays, both normal and dysrhythmic slow waves in human subjects have been studied, significantly facilitating clinical translation. However, due to its invasiveness, HR recording/mapping is limited in its clinical utility.

On the other hand, electrogastrogram (EGG) is a non-invasive method of recording the resultant body surface potential of gastric slow wave propagation. EGG holds major potential as a routinely deployable tool to aid the diagnosis of gastric slow wave dysrhythmias and digestive dysfunctions. However, there are several technical and physiological limitations that have prevented EGG from becoming a routine diagnostic tool.

One approach to isolating the electrical source of the organ and inferring the resultant body surface potential is by conducting a torso tank experiment, in which the signal of an electrically active organ is either simulated using an artificial source, e.g., a signal generator, or housing an excised organ, e.g., the heart, inside a torso phantom, usually filled with saline. This particular experimental preparation provides extensive access to and control of relevant parameters as well as the option of both qualitative and quantitative evaluations of the associated changes in the EGG.

It is our aim in this study to further characterise the relation between the gastric electrical activity and the EGG in the hopes of further developing the EGG as a tool of clinical diagnosis. 


Dr Peng Du


Research groups

Gastrointestinal Research Group


Selected publications and creative works (Research Outputs)

  • Calder, S., O'Grady G, Cheng, L. K., & Du, P. (2018). Torso-Tank Validation of High-Resolution Electrogastrography (EGG): Forward Modelling, Methodology and Results. Annals of biomedical engineering, 46 (8), 1183-1193. 10.1007/s10439-018-2030-x
    Other University of Auckland co-authors: Greg O'Grady
  • Calder, S. S. (2015). An Experimental and Theoretical Analysis of the Electrogastrogram The University of Auckland. ResearchSpace@Auckland.

Contact details

Primary office location

Level 8, Room 801
New Zealand