PHY3146 Applied Optics and Acoustics

2009-2010

Aims

Over the last two decades there have been significant developments in the medical use of non-ionising radiation, both optic and acoustic. Acoustics is routinely applied in imaging (Doppler-ultrasound) and therapeutic (e.g. shock-wave lithotripsy) contexts as well as underpinning the scientific understanding of speech and hearing. As high-power lasers have become commercially available, they have been exploited in a variety of, mainly therapeutic, clinical applications; this module covers both the theoretical, and practical, aspects of lasers and their operation.

Intended Learning Outcomes

A student should be able to:

Module Specific Skills

• explain surgical laser operation;
• describe the physics of light transport in tissue,the basic physical mechanisms of light-tissue interactions, and the medical application of these mechanisms;
• demonstrate awareness of laser safety;
• describe the structure and function of the ear;
• explain frequency resolution and hearing loss;
• manipulate the wave equation and deal with sound propagation in various systems (in particular, the effects of boundaries between two media);
• describe basic ultrasound imaging systems, and the equipment used;
• read literature associated with the advanced developments of the techniques and to put them into context within the broad area of medical imaging.

Discipline Specific Skills

• solve problems by the application of physical principles.

Personal and Key Skills

• undertake co-operative learning by discussing the contents of the module amongst themselves;
• appreciate the need to consider the safety aspects of working practices.

Learning and Teaching Methods

Lectures and demonstrations (20×1hr), problems classes (2×1hr). e-learning resources.

Assignments

Students are given problems during lectures and examples sheets which are discussed during problem classes.

Assessment

One 90-minute examination (100%).

Syllabus Plan and Content

1. Medical uses of lasers
   1. Laser operation and properties: pumping and gain mechanisms, directionality, continuous and pulsed modes.
   2. Light transport in tissue: absorption, scattering, transport theory.
   3. Principal light-tissue interaction mechanisms: photochemical, photothermal, photoablation, photodisruption.
   4. Therapeutic applications: dermatology, opthalmology, neurosurgery.
   5. Laser safety: eye hazards, skin hazards, laser classification and safety legislation.
2. Acoustic waves
   1. Acoustic wave equation
   2. Plane-wave solutions, speed of sound in various media
   3. Standing waves and vibrations
      1. Waves on a stretched string, membrane
      2. Sound waves in a pipe, cavity
      3. Waves on a bar
   4. Specific acoustic impedance, characteristic impedance of various media
   5. Intensity of sound waves
   6. Transmission across the boundary between two media
   7. Transmission through walls
3. Diagnostic ultrasound
   1. Frequency, wavelength, speed, resolution
   2. Characteristic impedance
   3. Attenuation
   4. Transducers and their output
   5. Types of scan and display
   6. Doppler systems
4. Medical acoustics
   1. Speech: phonemes and their classification, description of the vocal organs, acoustics of speech production, acoustic distinctions between phonemes, suprasegmental features, the speech spectrograph.
   2. Hearing: structure and function of the outer ear, middle ear and inner ear; the decibel, hearing threshold and equal-loudness curves, A-weighting, frequency resolution and auditory filters, hearing loss.
5. Sources of sound and sound transmission
   1. Monopole source
   2. Spherical waves
   3. Near and far field
   4. Strength of a source
6. Waves in pipes
   1. Helmholtz resonator
   2. Inertance, compliance and resistance (acoustic)
   3. Acoustic impedance
   4. Transmission in pipes; reflection and transmission at junctions

Core Text

Not applicable

Supplementary Text(s)

Denes P.B. and Pinson E.N. (1963), The Speech Chain, Bell Telephone Laboratories, ISBN x-021544-x (UL: 612.78 DEN)
Evans J.A. (1986), IPEM Report: Physics in Medical Ultrasound, IPEM, ISBN 0-904-18142-1 (UL: 616.075 EVA)
Hussey M. (1975), Diagnostic Ultrasound, Blackie & Son, ISBN 0-216-90029-8 (UL: 616.075 HUS )
Kinsler L.E. et al. (2000), Fundamentals of Acoustics (4^th edition), John Wiley, ISBN 0-471-84789-5 (UL: 534 FUN)
Niemz M.H. (1996), Laser-Tissue interactions, Springer, ISBN 3-540-60363-8 (UL: 610.28 NIE)
Pedrotti F.L. and Pedrotti F.J.L.S., Introduction to Optics, Prentice-Hall (UL: 535 PED)
Porges G., Applied Acoustics, Peninsula Publishing, ISBN 0-904-18141-1 (UL: 620.20 POR)

Formative Mechanisms

Students are able to assess their understanding through the problem sheets and classes. In addition, this module is given at Stages 3 and 4 when students have become familiar with staff and able to discuss difficulties with them.

Evaluation Mechanisms

The module will be evaluated using information gathered via the student representation mechanisms, the staff peer appraisal scheme, and measures of student attainment based on summative assessment.