Output Measurements for Medical Ultrasound de Roy C. Preston

Output Measurements for Medical Ultrasound

Roy C. Preston

en Limba Engleză Paperback – 23 noi 2011

Medical applications of ultrasound range from therapy, foetal monitoring, diagnostic imaging and blood flow measurement, to surgery and lithotripsy. Ever since the earliest developments of medical ultrasound there has been an interest in the measurement and characterisation of the ultrasonic fields generated in these applications, either for assessment of performance of equipment or for safety. Until recently, procedures for acoustic output measurements were ill-defined, but standards are now being developed internationally by the International Electrotechnical Commission (1EC) and reliable commercial measuring equipment is becoming more widely available. The aim of this book is to introduce acoustic output measurement techniques and to provide an insight into the measurement methods. The material presented is based on a course originally run during November 1989 at the National Physical Laboratory. In addition to the lectures, the course consisted of a series of practicals to allow participants to gain experience of making measurements. Teddington, UK Roy C. Preston February 1991 Contents List of Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii List of Symbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xv Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 Safety of Diagnostic Ultrasonic Equipment: The Relevance of Acoustic Output Information to the Clinical User R. C. Preston 1. 1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 5 1. 2 The Relevance of Acoustic Output Information. . . . . . . . . . . . . 6 1. 2. 1 What Is Acoustic Output Information? . . . . . . . . . . . . . . . . . . . 6 1. 2. 2 What Is Acoustic Output Information Used For? . . . . . . . 6 1. 2. 3 Why Should You Know the Acoustic Output Levels of Your Equipment? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1. 2. 4 Are Acoustic Output Levels Really that Important? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Cuprins

1 Safety of Diagnostic Ultrasonic Equipment: The Relevance of Acoustic Output Information to the Clinical User.- 1.1 Introduction.- 1.2 The Relevance of Acoustic Output Information.- 1.3 Acoustic Output Information.- 1.4 Acoustic Fields and Output of Medical Ultrasonic Equipment.- 1.5 Standards and Regulations.- 1.6 The Impact on the Clinician.- 1.7 Conclusions.- 1.8 Recommended Additional Reading Material.- 1.9 References.- 2 Fundamentals of Ultrasonic Propagation.- 2.1 Introduction.- 2.2 Ultrasonic Wave Propagation.- 2.3 Transduction.- 2.4 Ideal Fields.- 2.5 Nonlinear Propagation.- 2.6 Recommended Additional Reading Material.- 3 Overview of Measurement Techniques.- 3.1 Introduction.- 3.2 Key Acoustical and Other Field Parameters.- 3.3 Acoustic Pressure.- 3.4 Acoustic Displacement.- 3.5 Radiation Force.- 3.6 Temperature Rise.- 3.7 Summary of Quantitative Measurement Techniques.- 3.8 Assessment of Measurement Uncertainty.- 3.9 Measurement Traceability.- 3.10 Qualitative Techniques.- 3.11 References.- 4 Hydrophones.- 4.1 Introduction.- 4.2 Types of Hydrophone.- 4.3 Using a Hydrophone.- 5 Ultrasonic Power Balances.- 5.1 Introduction.- 5.2 The Radiation Force Balance.- 5.3 Choosing a Configuration and Target.- 5.4 Examples of Radiation Force Balances.- 5.5 Measurement Considerations.- 5.6 Summary of Important Points to Note During Measurements.- 5.7 References.- 6 Hydrophone-Based Measurements on a Specific Acoustic Pulse Part 1: Field Characterisation.- 6.1 Introduction.- 6.2 The Acoustic Pulse Waveform.- 6.3 Pressure Parameters.- 6.4 Derivation of Intensity from Pressure Measurements.- 6.5 Intensity Parameters.- 6.6 Spatial-peak Parameters.- 6.7 Beam-Shape Information.- 6.8 Spatial-Average Parameters.- 6.9 Power Parameters.- 6.10 Output Beam Intensity.- 6.11 Locating Maxima in Fields.- 6.12 Concept of in-situ or Derated Levels.- 6.13 References.- 7 Measurements on a Specific Acoustic Pulse Part 2: Measurements.- 7.1 Introduction.- 7.2 The Measurement System.- 7.3 Spatial-Peak Measurements.- 7.4 Spatial-Average Measurements.- 7.5 Continuous-Wave Systems.- 7.6 Accuracy Assessment.- 7.7 Recommended Additional Reading Material.- 7.8 References.- 8 Real-Time Scanning Systems Part 1: Modes of Operation.- 8.1 Introduction.- 8.2 Principles of Operation.- 8.3 Pulse Characteristics.- 8.4 Pulse Patterns.- 8.5 Scanner Settings.- 8.6 Discussion.- 8.7 Recommended Further Reading Material.- 9 Real-Time Scanning Systems Part 2: Measurements.- 9.1 Introduction.- 9.2 Measurement Systems.- 9.3 Making Measurements.- 9.4 Measurement Uncertainties.- 9.5 References.- Glossary: Definitions Relevant to Ultrasonic Field Measurements.