MPHY3886/M866/G886: Optics in Medicine

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Course information

Unit value
Year of study
Term
Course organiser & lecturer
Lecturer
Lecturer
0.5
3 or 4
Term 1
Dr Ben Cox
Dr Sandy Mosse
Dr Robert Cooper

Purpose

This course forms part of the Physics with Medical Physics (BSc), Medical Physics (MSci), Electronic Engineering with Medical Electronics (BEng) and Medical Physics & Bioengineering (BSc(Intercal)) undergraduate degrees. The course, taught during Term 1, will provide an introduction to the principles of tissue optics, lasers in medicine, and the interaction of light with biological tissues.

Course variants

This course can be taken in Year 3 as MPHY3886 or in Year 4 as an M-level variant called MPHYM886. The two variants differ in the amount of coursework, and the pass mark for the M-level variant is 50%. It can also be taken as an MSc module called MPHYG886.

Aims and Objectives

To provide a thorough understanding of the basic physical principles which underlie the various uses of light in diagnostic and therapeutic medicine, to impart sufficient knowledge to provide a basis for further courses in more specialised applications, and to form a basic core of knowledge appropriate for a trainee in medical physics.

Objectives
  • To provide a firm knowledge and understanding of how light and tissue interact, of the optical properties of tissues, and of methods for modelling light transport in tissue.
  • To explain the various effects, photochemical, thermal, mechanical, that can arise following the interaction of light with biological tissue.
  • To teach the physics of the types of laser typically used in medical applications.
  • To explain the physical principles underlying the safe usage of lasers and also the calculation of safe laser viewing conditions based of European Community standards. Students should be able to perform these calculations for simple viewing conditions.

Teaching and exams

Teaching will consist of:

  • Lectures, 32 hours.
  • Seminars/problem classes, 6 hours.
  • Required written work (coursework, problem sheets), 20 hours.
  • Private reading, 52 hours.

The assessment will consist of:

  • 1 unseen written examination (2.5 hours) worth 80% of the total module mark.
  • Two pieces of coursework, worth a total of 20% of the total module mark.

Prerequisites

We assume that you have met the minimum entry requirements for our undergraduate degree programmes (i.e. A level Mathematics (grade A preferred), Physics and one other A level at ABB or above, or equivalent). If you feel you meet the prerequisites through a non-standard route, please contact the module organiser. All variants of the modules have the same prerequisites.

Specific knowledge assumed:

Mathematics: Familiarity with simple algebra, trigonometry, basic differential and integral calculus, exponentials, vectors and matrices, and vector calculus notation would be helpful.

Physics / Engineering: No strict prerequisites but some familiarity with Jablonski diagrams would be helpful.

Biology: No specific background knowledge required.

Other: Nothing specific.

Description

Optical radiation, incorporating the ultraviolet, visible and infrared regions of the electromagnetic spectrum, has a wide range of uses in medicine, e.g. in surgical lasers and non invasive imaging systems. The way in which different wavelengths of light interact with the various components of biological tissue is key to the understanding of how optical radiation can be used to as a diagnostic and therapeutic tool. The foundation of this course is therefore the description of the physical principles of absorption and scattering and how these are adapted to describe light interaction with and transport through tissue. Light sources are described with particular emphasis given to the physics of lasers and their design and working principles. The unique properties of laser light can lead to the production of a very wide range of different tissue effects which are put to use in a number of clinical applications, e.g. treatment of cancers and removal of port wine stains. To optimise the use of lasers for specific treatments theoretical models are developed to predict the effects of laser light on tissue (e.g. depth of thermal coagulation). These models are described in detail as are a wide range of clinical applications of lasers. An understanding of laser safety is a prerequisite for anyone working with lasers. A summary of the European Laser Safety Standard is given with the relevant physics and anatomy background to explain how the limits of safety are determined. Practical examples of a number of laser safety scenarios and details of the laser safety calculations for eye and skin safety are also given.

The course is taught as a series of lectures, tutorials and seminars. Problem sheets and in-class calculation examples are used to show how the theory is put into practice.

Brief Syllabus

Introduction to Light Transport in Tissue
  • Mechanisms of light-tissue interactions
  • Physics of absorption, absorption spectra, spectroscopy
  • Physics of optical scattering, scattering coefficients, scattering phase functions
  • Essential terminology
  • Theories of light scattering including Rayleigh, Rayleigh Ganz Debye and Mie theory
  • Models of light transport including radiative transfer equation, diffusion approximation and Monte Carlo
Effects of light on Tissue
  • Fates of excited species
  • Photochemical effects, photodynamic therapy
  • Thermal effects, laser ablation and coagulation, laser hyperthermia, thermal relaxation time, photoacoustic effect
  • Photoablation, corrective eye surgery, LASIK
  • Clinical applications
Sources of Light
  • Incoherent and coherent light sources
  • Properties of laser light
  • Mechanisms of laser light generation
Laser Safety
  • European Safety Standard; laser classification
  • Laser safety of the eye
  • Corneal and retinal irradiance
  • Laser safety of the skin
  • Laser safety calculations

Useful Texts

  • Jorge Ripoll Lorenzo, Principles of Diffuse Light Propagation: Light Propagation in Tissues with Applications in Biology and Medicine, World Scientific, 2012
  • M. H. Niemz, Laser tissue interactions, 3rd edition, Springer Verlag, 2003.
  • Safety of laser products. Part I: equipment classification, requirements and user's guide. British Standards Institute, BS EN 60825-1 (2014)
  • J. A. S. Carruth and A. L. Mckenzie, Medical Lasers - science & clinical applications, Adam Hilger Ltd, 1986.
  • J. Wilson and J. F. B. Hawkes, Lasers, Principles and Applications, Prentice Hall, 1987.
  • A. Katzir, Lasers and Optical Fibres in Medicine, Academic Press Inc. 1993.
  • O. Svelto, Principles of Lasers, Plenum Press 1982.
  • G. F. Lothian, Absorption Spectrophotometry, Adam Hilger 1969.
  • L. A. Geddes and L. E. Baker, Principles of Applied Biomedical Instrumentation, Wiley, New York, 1989.