MPHY3013/M013 Medical Electronics and Neural Engineering

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Course information

Unit value
Year of study
Term
Course organiser
Second examiner
0.5
3 or 4
Term 2
Prof Nick Donaldson
Dr Anne Vanhoest

Purpose

This course brings together material from engineering, physics and physiology which are relevant to situations in which electronic devices are in direct contact with the body. It is therefore related to clinical applications in rehabilitation, intensive care, clinical neurophysiology and neuroprosthetics, etc. It should be useful to:

  • Medical students who will encounter these applications in clinical practice
  • Students who intend to go on to biomedical research
  • Engineering students who go on to specify, design, test or use clinical electrical equipment.
  • Students (pursuing degrees in either Electronic Engineering, Physics, Mechanical Engineering with Bioengineering, or Physical Sciences) who wish to familiarise themselves with medical electronics.

Usually, there are about equal numbers from engineering, the sciences, and intercalated medical students.

Year 3 and M-level variants

This course, taught during term 2, forms part of the Electronics with Medical Electronics (MEng) and Medical Physics & Bioengineering (MSci and Intercalated BSc) undergraduate degrees. For Electronics with Medical Electronics students this is a compulsory 3rd year course and provides core information which will be drawn upon during the final year. It is an optional course for other 3rd and 4th year Electronic Engineering students, and 4th year Physics students. For Medical students it is also optional.

This course can be taken in Year 3 as MPHY3013 or in Year 4 as an M-level variant called MPHYM013. The two variants differ in the amount of coursework, and the pass mark for the M-level variant is 50%.

Aims

The primary aim is to familiarise students with some of the important medical applications of electronics, where there is direct connection to the body, and to explain how the requirements for the equipment are derived. (Note that this course excludes imaging, other medical transducers and ionising radiation, which are covered in other courses.)

The taught material is not concerned with how the electronic devices work but what they must do for adequate performance and safety.

This course is tailored to the needs of both Engineers and Medics. It seeks to encourage dialogue between both disciplines to enable Medics and Engineers to appreciate more fully the applications, requirements, specifications, and limitations of medical electronic instrumentation. This is particularly important when multi-disciplinary teams liaise to specify, design and evaluate new medical technologies.

Objectives

  • To impart knowledge and understanding of the origins of electrophysiological signals and their characteristics.
  • To impart knowledge and understanding of electrodes.
  • To impart knowledge and understanding of electrical stimulation.
  • To impart knowledge and understanding of electric shock hazards and safety devices.
  • To impart knowledge and understanding of the characteristics and limitations of biomedical amplifiers for acquisition of electrophysiological signals, and to demonstrate how these characteristics are derived from an understanding of electrophysiology, electrode properties and electrical hazards.
  • To enable students to apply knowledge of stimulators and biomedical amplifiers during laboratory practicals and develop laboratory skills.
  • To illustrate and emphasise practical applications by visits to local hospitals.
  • To develop problem solving and analysis skills using the knowledge accumulated from this course.
  • To facilitate and develop communication skills and group work.
  • To enable students to take responsibility for their own learning.

Teaching and exams

Hours specific to the course:

  • Lectures: 26 hours.
  • Private reading: 25 hours.
  • Problem classes/tutorials: 2 hours (more if requested).
  • Laboratory work: 12 hours (3 experiments: 3 x 3 hour "mini-labs", 3 hours writing up).
  • Hospital department visits: 2 hours (2 x 1 hour visits).
  • Problem sheets: 20 hours (3 problem sheets).
  • Revision: 20 hours.


For MPHY3013 students, the assessment will consist of:

  • 1 Unseen written examination (3 hours) worth 80% of the total course mark.
  • Coursework completed during term-time worth 20% of the total course mark.

MHYM013 students will undertake the same exam and coursework, but complete an extra piece of assessed work.  They will be asked to present a scientific article to the class. Their exam will be worth 70% of the total work and coursework.

Prerequisites

Students should have an interest in the medical applications of electronics and have a basic knowledge of some circuit theory including complex impedance, and simple circuit components, such as resistors, capacitors and batteries. Prior knowledge of physics, electricity, anatomy and physiology will be useful. In past years, a particular difficulty for students on this course has been knowledge of transformers, complex number arithmetic and algebra, and its application to impedance calculations. We have therefore introduced six quizzes for students to do before the start of the course. To qualify for the course, you should pass 5 out of them (see Moodle page for more details).   These subjects are covered in some details in the Physiological Monitoring course (MPHY3012/M012). Attending this course in term 1 is not a prerequisite, but some form of prior understanding is recommended.

Description

The lectures are in four groups: electrical safety, amplifiers, electrodes and nerves. There are three practicals (which take place in the Undergraduate Lab on the 6 th Floor of the Roberts Building) and usually two visits to local hospitals to see how the methods are applied (e.g. Clinical neurophysiology, Cochlear implants, UCH Equipment Management). Three question sheets are set for coursework.

The course begins with an overview of the subject of Medical Electronics, discussing its scope and relevance to Engineers and Medics.  Fundamental knowledge of physiological signal evolution and characteristics are reviewed.

The section on safety considers electricity supply, physiological effects of electricity on the body, sources of electrical hazards, issues of safety and safety devices.

The following section is about biomedical amplifiers. Requirements and characteristics are described. Sources of interference are discussed with emphasis on 50Hz mains interference.

The section on electrodes considers types of electrode and the resistance to ionic current flow in the tissue. The electrode-electrolyte interface is described at equilibrium and polarisable and non-polarisable electrodes are considered for silver/silver chloride and platinum respectively. Electrical models of the electrodes are introduced.  Volume conductor effects are discussed leading to a brief introduction to recorded neural signals.The next section imparts knowledge on electrical stimulation. The response of muscles to artificially-activated nerves is considered, the design of stimulators and functional uses.  Specifically, the behaviour of neurons is studied, by considering resting potentials and action potentials. Finally, applications of recording biopotential signals and electrical stimulation are considered. Examples include recording electrical signals from the heart (ECG), muscles (EMG), nerves (ENG) and brain (EEG) and the use of stimulators for defibrillators, pacemakers, cochlear implants and restoring loss of limb movement.

The course subject matter is conveyed through lectures, problem solving, student preparation and presentation of seminars and tutorials, demonstrations, "mini-labs" and recommended reading. The mini-labs provide the opportunity to study electrical activity generated by the students' own muscles (EMG) during movement and to measure nerve conduction velocity. They also develop practical skills, teach students to manage their time to achieve a required task, facilitate team work, and provide the opportunity to apply theoretical principles taught during the course.

Brief Syllabus

Lectures (3 hours per week during Term 1)

  1. Introduction to Medical Electronics.
  2. Electricity Supply and Sources of Hazard. Experimental results; Internal, External; Threshold levels; Electric Shock hazards (vacuum cleaner example, etc); Earth Leakage and "Patient" leakage; Isolation and circuit breakers.
  3. Biomedical Amplifiers. Characteristics of biomedical signals, common-mode interference, differential amplifiers, Common Mode Rejection Ratio, effect of source resistances.
  4. Electrodes. Terminology, Variety of Electrodes, Calculation of Resistances in Volume Conductor, Half-cell potentials, Reference Electrodes, Non-polarisable (silver-silver chloride electrode), Polarisable electrode (platinum), Circuit models of electrodes.
  5. Electrophysiology and electrical stimulation. Nerves, Nerve structure, Resting Potential, Action Potentials (regeneration), Action Potential (propagation), Volume Conductor Effects, Recorded nerve signals. Nerve stimulation due to current flow, response to stimulation (strength-duration curve, twitch response, tetanic contractions, force-pulse frequency effect, force-modulation frequency), design of stimulators, uses of muscle stimulation, simulation of neuron activation.
  6. Applications: Biopotential Signal Recording. EEG, ECG, EMG, ENG, ERG.
  7. Applications: Stimulation. Defibrillators, pacemakers, FES, cochlear stimulators.

Core Texts

  • R. H. S. Carpenter, Neurophysiology (3rd Edition), Arnold, 1996.
  • J. G. Webster (Editor), Medical Instrumentation - Application and Design, Houghton Miflin Co. Note: Third Edition £39.95. Beware that the Second Edition sells for the much inflated price of £75
  • B. H. Brown, R. H. Smallwood, D. C. Barber, P. V. Lawford and D. R. Hose, Medical Physics and Biomedical Engineering, Institute of Physics Publishing, 1999.

Comments from previous students on the course

In general:

"It was a practical hands-on course."
"The lecturers conveyed their enthusiasm for the subject."
"The lecturers cared about the students."

Regarding the mini-labs:

"They were all very good. Questions helped a lot in understanding."
"I'd never used oscilloscopes before."
"The stimulation of the leg muscle was very good."
"The electronics course practical sessions were fun, interesting and stimulating."