Matthew Hussey

Coupled Harmonic Oscillators

The aim in this chapter is to discuss the situation in which two mechanical oscillators interact with each other and energy can be interchanged between them.

Vibrations and the Human Body

The aim in this chapter is to describe the effects of externally applied vibrations on the human body and to discuss the significance of two internally generated mechanical vibrations in the body.

Free Harmonic Oscillator

In this chapter the aim is to describe the oscillatory behaviour of a simple system when vibrating freely, that is, without any external influences after the initial start-up.

The Scope of Medical Diagnostic Ultrasound

Ultrasound now ranks as a major diagnostic tool in medicine. Its applications are constantly expanding to new areas of the body with novel examination procedures being described in the literature. The types and sophistication of diagnostic ultrasound equipment are constantly being increased and improved. Ultrasound literature is expanding each year. Within this developing context, many firmly established ultrasound examination procedures now exist in the areas of obstetrics and gynaecology, neurology (brain and spinal chord), ophthalmology, cardiology, thyroid and breast, together with general abdominal imaging investigations. Techniques are also widely used for the study of blood flow throughout the cardiovascular system and for the assessment of the arteries, using ultrasound equipment based on the Doppler effect.

Basic Features of Ultrasound Propagation

This chapter deals with the basic ideas and aspects of ultrasound as it travels through a medium. The main questions addressed are the following: what are sound and ultrasound, what does the medium through which the ultrasound is passing do to the ultrasound, and finally, what does the ultrasound do to the medium?

Special Instruments and New Topics

There are many developments in the general area of diagnostic ultrasound which have not yet found wide application, but which are of considerable interest nevertheless. Some of these apply only in limited regions of the body or in limited areas of medicine. Some are still at the research stage and must yet be developed into clinical tools and procedures—if indeed the ideas prove worthwhile.

A-Mode Scanning Instruments

The earliest medical diagnostic ultrasound instrument was the A-Unit. Nowadays it is not itself of great importance but it is still at the heart of the more advanced types of instruments and therefore warrants some special attention. An understanding of the A-mode instrument is in many respects a prerequisite for understanding the more developed machines.

Safety of Diagnostic Ultrasound

One of the main advantages of ultrasound as a diagnostic tool is the absence of any observed undesirable side effects. But clinical users of ultrasound instrumentation should have a critical appreciation of this statement. What side effects can be caused by ultrasound? Under what conditions can such effects be produced? What risk is there of such effects arising from present or possible future diagnostic applications of ultrasound? Are there any possible abuses or mis-uses of diagnostic ultrasound which could accentuate these risks? How do these risks weigh in the balance with the benefits of diagnostic ultrasound procedures? Where are the gaps in our knowledge of this area? What basic precautions should the machine operator take to improve the protection of the patient against any possible risks from ultrasound radiation?

Motion (M-) Mode Scanning Instruments

One of the drawbacks of A-mode scanning is the fact that it yields only crude qualitative appreciation of the motion of structures. In order to overcome this difficulty, in particular for applications dealing with rhythmically-moving structures such as the heart and its valves, motion (M-), also called time-position (T–P), mode scanning, has been developed.

Static B-Mode Instruments

It was pointed out previously that one of the major drawbacks of the A-mode scanning technique is the fact that it acquires information about only a single line through the tissue at any particular position of the probe. The most common method for overcoming this one-dimensionality is the B-mode technique.