5. Piezoelectric effect : history 1880 piezoelectric effect : Pierre Curie and Jacques Curie. Curie temperature 1917, SONAR, Paul Langevin ultrasonic submarine detector. Post World War II : “AT cut” crystal barium titanate lead zirconatetitanate vaseemali@gmail.com 5
10. Ultrasound gel Contents Carbomer EDTA Propylene glycol Trolamine Don’t adjust gain till gel is applied Apply gel on both sides of plastic When nothing is available : use water vaseemali@gmail.com 10
12. Transducer : piezoelectric effect Direct mechanical force applied Internal generation of electrical charge Reverse Electrical field applied internal generation of a mechanical force vaseemali@gmail.com 12
23. Pulsed mode DC applied Disc expands A layer is compressed Subsequently adjacent layer compressed Compression wave of v velocity vaseemali@gmail.com 20
24. Continuous mode AC voltage applied Crystal pulsed like piston Compressions and rarefactions Wavelength Frequency vaseemali@gmail.com 21
25. Near field(Fresnel zone) & far field(Fraunhofer zone) Near field : inhomogeneous interference Far field : diverges Focal zone Between near and far field Best resolution vaseemali@gmail.com 22
26. Mechanical transducers Obsolete Physically moved for beam steering Used in 3D 4D Types Rotary wheel Oscillating transducer Oscillating mirror vaseemali@gmail.com 23 Diagnostic Ultrasound: Physics and Equipment edited by Peter R. Hoskins, Kevin Martin, Abigail Thrush
27. Rotary wheel One or more elements Wheel like housing Small transducer face Intercostal access vaseemali@gmail.com 24
31. electronicfocusing Multiple elements used Separate electrical supply Sequential excitement of elements Types Linear curved 2 dimensional Annular phased array vaseemali@gmail.com 28
32. Electronic focusing Mounted on straight bar Electronic pulsing Focal depth Focus at many FL Greater time delay b/n elements=shorter focal length vaseemali@gmail.com 29
33. Multiple zone focusing 2 focal zones Focused in 2 pulses First one focused at f1 Second at f2 vaseemali@gmail.com 30
34. Linear VS Curved array Linear curved Larger area of pt contact Wide field near the skin Better quality image Superficial structures Small acoustic window Narrow field near skin Wide field at depth Detailing is less vaseemali@gmail.com 31
35. Evolution of arrays vaseemali@gmail.com 32 Medical imaging: principles, detectors, and electronics By Krzysztof Iniewski
36. 1.5 D array Multiple(5-7) linear arrays Beam steering in Azimuthal plane Phased : outer to inner Frame rate reduction vaseemali@gmail.com 33 The essential physics of medical imaging By Jerrold T. Bushberg
37. 2D array Multiple rows of elements Voxel instead of pixel Obstetrics vaseemali@gmail.com 34
46. "I" Style Finger-Grip intraop vaseemali@gmail.com 43 design fits comfortably between the index and middle finger which allows for palpating organs and scanning at the same time. Array Type: Convex ArrayScan angle/width: 65°/20mmFrequency range: 3.75-10 MHz
47. End Fire Laparoscopic vaseemali@gmail.com 44 End-fire laparoscopic transducer that is perfect for CBD scanning and targeting lesions. Array Type: Phased ArrayScan angle/width: 90°Frequency range: 3-7.5 MHz
48. Micro Surgery vaseemali@gmail.com 45 pediatric scanning CBD scanning. small vessels Array Type: Linear ArrayInsertion diameter: 10mmScan angle/width: 10mmFrequency range: 5-13 MHz
49. Motorized TEE vaseemali@gmail.com 46 cardiac anesthesia, cardiac surgery, or intensive care work Array type: Phased Array SectorScan angle: 90°Frequency range: 2-8 MHzInsertion Depth: 1000 mmDiameter: 12.5 mm
65. gain Degree of echo amplification Bightness of display Measured in db More : artifactual echoes Less : negates real echo info vaseemali@gmail.com 57 Gain
74. A mode Ophthalmic exam Precise length & depth measurements Transducer : line of sight Position of structure : X Strength of backscatter vaseemali@gmail.com 66 Amplitude of backscatter Time/distance
76. M mode Brightness α intensity of reflected signal Position of moving reflectors Rapid motion : cardiac valves vaseemali@gmail.com 68 Essentials of medical ultrasound: a practical introduction to the principles By Michael H. Repacholi, Dierdre A. Benwell
78. M mode ECG concurrent Line of sight vaseemali@gmail.com 70
79. Real time USG Succession of frames Motion of tissues Line density at least 100 per frame Frame rate Depth of view vaseemali@gmail.com 71
80. Frame rate Movie FR 25-30fps Temporal resolution Now >100 fps, TR 10ms Real time 20-30fps M mode : very high fps Hence LOS ,TR 0.1ms Better frame rate Less depth Less field of view Depth X scan lines X frame rate =constant vaseemali@gmail.com 72
82. Trackball Cursor motion GUI control vaseemali@gmail.com 74 Track ball
83. Zoom Magnifies selected area Read zoom Digital zoom No changes in line density Write zoom Optical zoom Increases scan line density Improved resolution vaseemali@gmail.com 75
85. Dynamic range/compress Ratio of largest/smallest echo Measured in dB From tissues 100-150dB Decreases as signals into USG Rejection filter : rejects very small & very large echoes TGC 60 dB at ADC level vaseemali@gmail.com 77
86. Compress 60dB of interest Display : only 20dB brightness levels Non linear amplifier More gain for smaller signals Liver texture: wide Obstetric: less Dark : amniotic fluid Bright : bones vaseemali@gmail.com 78
88. Power Not the same as gain Energy transferred to tissues More power : more tissue damage Measured in watts/cm2 ALARA : as low as reasonably allowable More than 8 W/cm2 : therapeutic AIUM guidelines(SATA,SPTP) Doppler : excessive power levels Use less power Quick examination vaseemali@gmail.com 80
92. Time gain compensation vaseemali@gmail.com 84 Springer handbook of acoustics By Thomas D. Rossing
93. Freeze and cine loop Stops further image acquisition Displays current image vaseemali@gmail.com 85
94. Cine loop Track ball Not USG specific Used in CT MRI PET Still images in succession Played back Dynamic movement : Cardiac motion Doppler studies Recorded as movie Physician/cardiologist can view later vaseemali@gmail.com 86
95. Image processor Interpolation between scan lines Log compress Post processing Spatial filtering Reduce noise Enhance edges Temporal filtering : frame avg/persist Reduces image noise Image demonstrates a lag Reduction in temporal resolution vaseemali@gmail.com 87
96. Scan converter (ADC) Echo : Analog wave Analogue Storage CRT Unstable “drift” in settings Analog-Digital convertor Digital Stable Processing vaseemali@gmail.com 88
97. Image display Displays : analogue input Modern machines: digital architecture DAC Input : digital Output : analogue Brightness Contrast vaseemali@gmail.com 89
98. Image memory 640 X 480 pixels 256 gray shade levels ¼ MB per image Color images : Doppler imaging Freeze function Temporary image store Archiving : MLC Latest systems : internal storage Hold many GB data vaseemali@gmail.com 90
99. Image resolution Spatial : 2 close objects as distinct Axial : along beam axis Lateral : perpendicular to beam axis Azimuthal : perpendicular to beam & transducer Contrast : two regions of different avg brightness Temporal : distinguish events in time Real time cant in cardiac valve motion Freedom from artifacts vaseemali@gmail.com 91
103. Axial resolution 95 Ultrasound in cardiology By Kurt J. G. Schmailzl, Oliver Ormerod vaseemali@gmail.com
104. Lateral resolution Depends on Beam width User controlled Depends on focusing vaseemali@gmail.com 96 The essential physics of medical imaging By Jerrold T. Bushberg
105. Azimuthal/elevation resolution Resolution in plane Perpendicular to beam axis Perpendicular to transducer Thickness of beam No user control Fixed due to transducer thickness vaseemali@gmail.com 97
113. References Principles and Practice of Ultrasonography By Bhargava Doppler Ultrasound in Gynecology and Obstetrics By ChristofSohn, Hans-Joachim Voigt, Klaus Vetter, Klaus Vetter (M.D.) Small animal diagnostic ultrasound By Thomas G. Nyland, John S. Matto Clinical sonography: a practical guide By Roger C. Sanders, Thomas Charles Winter on Clinical diagnostic ultrasound By Grant M. Baxter, Paul L. P. Allan, Patricia Morley PACS and Imaging Informatics: Basic Principles and Applications By H. K. Huang Medical imaging physics By William R. Hendee, E. Russell Ritenour The essential physics of medical imaging By Jerrold T. Bushberg Appleton & Lange's review for the ultrasonography examination By Carol Krebs, Charles S. Odwin, Arthur C. Fleischer Advances in mass data analysis of images and signals in medicine ... By Petra Perner The practice of ultrasound: a step-by-step guide to abdominal scanning By Berthold Block Diagnostic ultrasound imaging: inside out By Thomas L. Szabo vaseemali@gmail.com 105
