MPHY3886/M866/G886: Optics in Medicine

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Course information

Unit value
Year of study
Term
Course organiser
Second examiner
Other lecturers
0.5
3 or 4
Term 1
Prof Clare Elwell
Dr Ben Cox
Dr. Adrien Desjardins
Dr. Sandy Mosse

Purpose

This course forms part of the Physics with Medical Physics (B.Sc.), Medical Physics (M.Sci.), Electronic Engineering with Medical Electronics (B.Eng)and Medical Physics & Bioengineering (B.Sc.(Intercal)) undergraduate degrees. The course, taught during Term 1, will provide an introduction to the principles of optics and 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 and
to impart sufficient knowledge to provide a basis for further courses in more
specialised applications as well as help form a basic core of knowledge appropriate
for a trainee in medical physics.

Objectives
  • To provide a sound basic knowledge and understanding of the optical properties of tissues, the effects of multiple scattering on light distribution and mathematical methods for calculating the transport of light in tissues.
  • To impart knowledge on applications of microscopy techniques including optical coherence tomography and fluorescence microscopy.
  • To impart knowledge in laser physics and the principles of the thermal, photochemical and photomechanical effects that light can have on biologicaltissue.
  • To impart knowledge on 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 (essays, 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 course mark.
  • Coursework comprising 2 problem sheets, 1 essay, and 1 e-learning exercise, completed during term-time, worth a total of 20% of the total course mark.

Prerequisites

There are no strict prerequisites.

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 which include practical demonstrations of light interaction with tissue and some of the clinical optical monitors routinely use in hospitals. 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
  • Major Chromophores in Tissue
  • Terminology
  • Laws of Absorption
  • Theories of light scattering including Rayleigh, Rayleigh Ganz Debye and Mie theory
  • Models of light transport including Diffusion theory, Kubelka Munk and Monte Carlo
  • Non linear effects including fluorescence and phosphorescence
Applications
  • Oximetry
  • Optical Coherence Tomography
  • Microscopy
Sources of Light
  • Incoherent and coherent light sources
  • Properties of laser light
  • Mechanisms of laser light generation
Effects of laser light in Tissue
  • Thermal effects; laser ablation and coagulation, laser hyperthermia, thermal relaxation time.
  • Photochemical effects;photoablation, photodynamic therapy
  • Photoacoustic effects; photoacoustic spectroscopy, laser generation of shock waves
  • Clinical applications
Laser Safety
  • European Safety Standard; laser classification
  • Laser safety of the eye
  • Corneal and retinal irradiance
  • Laser safety of the skin
  • Laser safety calculations

Core Texts

  • J. A. S. Carruth and A. L. Mckenzie, Medical Lasers - science & clinical applications, Adam Hilger Ltd, 1986. (TM)
  • J. Wilson and J. F. B. Hawkes, Lasers, Principles and Applications, Prentice Hall, 1987. (TM)
  • M. H. Niemz, Laser tissue interactions, Springer Verlag.
  • A. Katzir, Lasers and Optical Fibres in Medicine, Academic Press Inc. 1993. (TM)
  • O. Svelto, Principles of Lasers, Plenum Press 1982. (TM)
  • Safety of laser products. Part I: equipment classification, requirements and user's guide. British Standards Institute (1994). BS EN 60825-1
  • G. F. Lothian, Absorption Spectrophotometry, Adam Hilger 1969.
  • L. A. Geddes and L. E. Baker, Principles of Applied Biomedical Instrumentation, J. Wiley, New York, 1989.