Essentials of Medical Ultrasound

One of the first applications of ultrasound was in submarine sonar equip­ ment. Since then ultrasound has found increasing applications, particularly in industry, but increasingly in biomedicine. For many years ultrasound has been used in physical therapy, although only in the past decade or two has it evolved from laboratory curiosity to a well-established diagnostic imaging modality. Ultrasound is now a widely accepted, indeed pervasive, diagnos­ tic and therapeutic tool in the medical field, and its applications are increasing rapidly. Our intent in developing this book is to provide a coherent tutorial intro­ duction to the field of medical ultrasound at a level suitable for those en­ tering the area from either medical or scientific backgrounds. The topics discussed should be of interest to nearly all medical and health care per­ sonnel needing to understand or operate ultrasonic devices, including clini­ cians, medical technicians, physiotherapists, medical physicists, and other biomedical scientists interested in the field. The book opens with a description of the basic principles of propagating acoustic waves, explains how they interact with a wide range of biological systems, and outlines the effects they produce. To provide practical infor­ mation to operators of ultrasound equipment, we have included thorough coverage of the details of ultrasonic instrumentation and measurement techniques, and set forth the framework for an effective quality assurance program.

1 Physical Characteristics of Ultrasound.- 1. Introduction.- 2. Acoustic Waves.- 2.1. Wave Motion.- 2.2. Periodic Wave Motion.- 3. Parameters on an Ultrasonic Wave.- 3.1. Modes of Wave Propagation.- 3.2. Standing Waves.- 4. Ultrasonic Transducers.- 4.1. Piezoelectric Materials.- 4.2. Medical Transducers.- 5. Characteristics of Ultrasound Beams.- 5.1. Huygen’s Principle.- 5.2. Circular Transducers.- 5.3. Far Field.- 5.4. Near Field.- 5.5. Pulsed Transducers.- 6. Reflection and Refraction.- 6.1. Matching.- 6.2. Mode Conversion.- 7. Absorption and Scattering.- 7.1. Absorption.- 7.2. Dispersion.- 7.3. Scattering.- 7.4. Doppler Effect.- 8. Conclusion.- Appendix: Mathematical Derivations of Physical Characteristics.- A. 1. Acoustic Waves.- A. 2. Modes of Propagation of Acoustic Waves.- References.- 2 Biophysical Mechanisms of Ultrasound.- 1. Introduction.- 2. Thermal Mechanism.- 2.1. Temperature Rise Without Heat Transfer.- 2.2. Temperature Rise During a Single Pulse—No Heat Transfer.- 2.3. Thermal Method of Intensity Measurement—No Heat Transfer.- 2.4. Temperature Rise with Heat Transfer.- 2.5. Temperature vs Time in an Absorbing Sphere—Influence of Conduction.- 2.6. Applications to Biomedical Ultrasound.- 2.7. Summary of Findings for Thermal Mechanism.- 3. Stress Mechanisms.- 3.1. First-Order and Second-Order Quantities—Radiation Pressure.- 3.2. Radiation Force.- 3.3. Radiation Torque.- 3.4. Acoustic Microstreaming.- 3.5. Stress Fields of Gas-Filled Pores—Low Megahertz Frequencies.- 3.6. Summary of Findings for Stress Mechanism.- 4. Cavitation.- 5. Conclusions.- References.- 3 Ultrasonic Measurement Techniques and Equipment Output Levels.- 1. Introduction.- 2. Measurement Parameters.- 3. Techniques and Instrumentation.- 3.1. Total Power—Radiation Force.- 3.2. Radiation Force-Intensity Techniques.- 3.3. Thermal Methods.- 3.4. Optical Techniques.- 3.5. Reciprocity Calibration.- 3.6. Electrical Determination of Ultrasonic Output for Quartz Transducers.- 3.7. Miniature Hydrophones.- 4. Ultrasound Equipment Output Levels.- 4.1. Therapy Equipment.- 4.2. Diagnostic Equipment.- 4.3. Output Levels and Biological Effect Levels.- References.- 4 Selected Biological Effects of Ultrasound.- 1. Introduction.- 2. Whole-Body Radiation.- 2.1. Vertebrates.- 2.2. Insects.- 3. Tissues and Organs.- 3.1. Central Nervous System.- 3.2. Liver.- 3.3. Testes.- 3.4. Blood Stasis.- 3.5. Tissue Regeneration.- 3.6. Neoplastic Tissues and Synergism.- 4. Cells and Microorganisms.- 5. Biomacromolecules and Their Assemblages.- 5.1. Biomacromolecules.- 5.2. Macromolecular Assemblages.- 6. Concluding Remarks.- 7. Acknowledgments.- References.- 5 Clinical Applications of Diagnostic Ultrasound.- 1. Introduction.- 1.1. Limited Significance Method.- 1.2. Useful Ancillary Method of Investigation.- 1.3. Most Efficacious Method of Non-Invasive Examination.- 1.4. Sole Investigative Tool.- 2. Head.- 2.1. Brain.- 2.2. Eyes.- 3. Neck.- 3.1. Thyroid and Parathyroid Glands.- 3.2. Carotid Artery.- 4. Chest.- 4.1. Heart.- 4.2. Pleural Space.- 4.3. Breast.- 5. Abdomen.- 5.1. Liver.- 5.2. Kidneys.- 5.3. Pancreas.- 5.4. Spleen.- 5.5. Biliary Tract.- 5.6. Aorta.- 5.7. Lymph Nodes.- 5.8. Peritoneal Space.- 6. Pelvis.- 6.1. Uterus (Pregnant).- 6.2. Uterus (Nonpregnant).- 6.3. Fallopian Tubes and Ovaries.- 6.4. Bladder.- 6.5. Prostate and Scrotum.- 7. Extremities.- 8. Conclusion.- 6 Ultrasound Therapy.- 1. Introduction.- 2. Therapeutic Devices and the Ultrasound Field.- 2.1. Ultrasound Therapy Devices.- 2.2. Temporal (Time) Variations of the Ultrasound Field.- 2.3. Spatial Variations of Ultrasound Fields.- 3. Quality Assurance and Standards.- 3.1. Power and Intensity.- 3.2. Power Output and Exposure Time.- 3.3. Quality Assurance of Equipment.- 4. Ultrasound Transmission and Absorption in Biological Materials.- 5. Applications of Therapeutic Ultrasound.- 6. Minimizing Operator and Patient Exposure.- 7. Contraindications for the Application of Ultrasound in Therapy.- 8. Summary.- References.- 7 Quality Assurance in Diagnostic Ultrasound.- 1. Introduction.- 2. Description of Equipment Displays.- 2.1. A-Mode.- 2.2. B-Mode.- 2.3. M-Mode.- 2.4. Two-Dimensional Cross-Section Images.- 2.5. Gray-Scale.- 2.6. Real-Time Displays.- 2.7. Continuous-Wave Techniques.- 2.8. Holographic Display.- 3. Equipment Operation.- 3.1. Operator Controls.- 3.2. Scanning Technique.- 3.3. Potential Hazards.- 3.4. Warmup Procedure.- 3.5. Hardcopy Care.- 3.6. Hospital Electrical Noise.- 4. Routine Preventive Maintenance.- 4.1. Hardcopy.- 4.2. Air Filters.- 4.3. Scanning Arm Stability.- 4.4. Integrity of Enclosures.- 4.5. Worn or Frayed Cables.- 5. System Performance and Testing.- 5.1. Transducer.- 5.2. Receiver.- 5.3. Analog Scan Converter.- 5.4. Digital Scan Converter.- 5.5. Gray-Scale Display.- 5.6. B-Mode Registration.- 5.7. Display Size and Linearity.- 5.8. Document System Performance.- 6. Routine Performance Tests.- 6.1. Introduction.- 6.2. AIUM 100-mm Test Object.- 6.3. Test of Test Object Liquid Acoustic Velocity.- 6.4. Other Performance Tests.- Performance Test Worksheets.- 7. Summary.- Sample Service Logs.- References.- Bibliography: Selected Quality Assurance Publications.- 8 Ultrasound Standards: Regulations and Guidelines.- 1. Philosophy of Developing Standards.- 2. Biological Effects.- 3. Types of Standards.- 4. Device or Emission Standards.- 4.1. Diagnostic Ultrasound.- 4.2. Therapy Devices.- 4.3. Surgical Devices.- 4.4. Dentistry.- 5. Safe-Use Guidelines and Education.- 5.1. Guidelines.- 5.2. Education.- 6. International Activities.- 7. National Standards.- 8. Summary.- References.- Glossary of Ultrasound Terminology.