Ultrasound imaging

1. Ultrasound IMAGING NIVETA SINGH MADE BY:

2. CONTENTS INTRODUCTION PRINCIPLE OF ULTRASOUND GENERATION AND DETECTION OF ULTRASOUND MAIN IMAGING MODES ULTRASOUND MACHINE PHILIPS HD11 ULTRASOUND SYSTEM TRANSDUCER PROBES WORKING PROCEDURE OF ULTRASOUND APPLICATIONS BENEFITS LIMITATIONS

3. ULTRASOUND: BASIC DEFINITION Ultrasound is acoustic(sound) energy in the form of waves having a frequency above the human hearing range(i.e. 20KHz) U ltrasound is a way of using sound waves to look inside the human body.

4. Ultrasound is a longitudinal mechanical wave where particle displacement is parallel to the propagation of wave. Transverse wave Longitudinal wave

5. PRINCIPLE OF ULTRASOUND Ultrasound waves are created by a vibrating crystal within a ceramic probe. Waves travel through the tissue and are partly reflected at each tissue interface. “Piezoelectric “ principle- electric current causes crystal to vibrate, returning waves create electric current. Following phenomenon occur when ultrasound propagates through matter: Reflection Refraction Diffraction Attenuation Scattering

6. GENERATION OF ULTRASOUND Ultrasound waves are usually both generated and detected by a piezoelectric crystal. The crystal deforms under the influence of an electric field and, vice-versa. When an alternating voltage is applied over the crystal, a compression wave with the same frequency is generated. Generally used piezoelectric materials are: PZT and PVDF (polyvinylidene fluoride)

7. DEFINITION /TERMINOLOGY Cycle Frequency :cycles per second Wavelength Acoustic impedance Velocity = f* λ = constant for a given medium Rarefaction = area of low density Compression = area of high density Attenuation Acoustic mismatch Frequency Amplitude Wavelength

8. INTERACTION OF ULTRASOUND WITH TISSUE

9. PIEZOELECTRIC CRYSTALS The thickness of the crystal determines the frequency of the scan head. Low Frequency 3 MHz High Frequency 10 MHz

10. FREQUENCY AND RESOLUTION HIGH FREQUENCY = HIGH RESOLUTION 3.5 MHz(sector) 7.5 MHz(linear)

11. FREQUENCY AND PENETRATION

12. ULTRASONOGRAPHY Ultrasonography or diagnostic sonography is an ultrasound based diagnostic imaging technique used for visualizing internal body structures.

13. MAIN IMAGING MODES GREY SCALE IMAGING A-Mode B-Mode M-Mode DOPPLER IMAGING Continuous wave Doppler Power Doppler Color Doppler Duplex Doppler Pulsed wave Doppler

14. A MODE Simplest form of ultrasound imaging which is based on the pulse-echo principle. A scans can be used to measure distances. A scans only give one dimensional information Not so useful for imaging Used for echo-encephalography and echo-ophthalmoscopy

15. B MODE B stands for Brightness B scans give two dimensional information about the cross-section. Generally used to measure cardiac chambers dimensions, assess valvular structure and function.

16. M MODE M stands for motion This represents movements of structures over time. M Mode is commonly used for measuring chamber dimensions. This is analogous to recording a video in ultrasound.

17. DOPPLER IMAGING It is a general term used to visualize velocities of moving tissues. Doppler ultrasound evaluates blood velocity as it flows through a blood vessel. Blood flow through the heart and large vessels has certain characteristics that can be measured using Doppler instruments.

18. BLOOD FLOW PATTERNS LAMINAR FLOW Layers of flow (normal) Slowest at vessel wall Fastest within center of vessel TURBULENT FLOW Obstructions disrupt laminar flow Disordered directions of flow

19. Apparent change in received frequency due to a relative motion between a sound source and sound receiver Sound TOWARD receiver = frequency Sound AWAY from receiver = frequency DOPPLER EFFECT

20. DOPPLER EQUATION

21. What defines a good Doppler display? No background noise Clear audible signal Accurate display of velocities

22. TYPES OF DOPPLER ULTRASOUND 1. CONTINUOUS WAVE DOPPLER (CW) Uses different crystals to send and receive the signal One crystal constantly sends a sound wave of a single frequency, the other constantly receives the reflected signal

23. Advantages of CW Can accurately display flow of any velocity without aliasing Disadvantages of CW Samples everything along the Doppler line Cannot position the Doppler to listen at a specific area along it’s path

24. 2. PULSED WAVE DOPPLER Produces short bursts/pulses of sound Uses the same crystals to send and receive the signal This follows the same pulse-echo technique used in 2D image formation.

25. Advantages of PW Can sample at a specific site along the Doppler line. The location of the sample is represented by the Sample Volume Disadvantages of PW The maximum velocity which can be displayed is limited. The signal will always alias at a given point, based on the transducer frequency.

26. COMPARISON

27. 3. COLOR DOPPLER Utilizes pulse-echo Doppler flow principles to generate a color image. I mage is superimposed on the 2D image. The red and blue display provides information regarding DIRECTION and VELOCITY of flow. Used for general assessment of flow in the region of interest Gives only descriptive or semi quantitative information on blood flow.

28. PW Doppler Color Doppler

29. 4. POWER DOPPLER 5 times more sensitive in detecting blood flow than color doppler. It can get those images that are impossible with color doppler. U sed to evaluate blood flow through vessels within solid organs.

30. ULTRASOUND MACHINE

31. MODELS OF ULTRASOUND MACHINE Following models of ultrasound systems have been studied: PHILIPS EPIQ 5/7 Most advanced ultrasound system Has anatomical intelligence PHILIPS HD11 / HD11 XE LCD with a rotation of 360 Better resolution as compared to Envisor series PHILIPS ENVISOR SERIES Poor resolution Monitor rotation is about 70-80

32. PHILIPS HD11 ULTRASOUND SYSTEM

33. APPLICATIONS Applications available on the HD11 ultrasound system are: Abdominal Cardiac Gynecological Intraoperative Musculoskeletal Neonatal head Obstetrical Pediatric Transcranial and Transesophageal Vascular

34. GENERAL COMPONENTS OF HD11 System control panel System monitor PC E box System power supply

35. HARDWARE ARCHITECTURE It consists of an E BOX and personal computer (PC) E Box has electronic boards that performs many ultrasonic imaging functions such as transducer selection, Beam forming, detection and image processing. The various electronic boards are: 1. S ystem motherboard (backplane) 2. Signal distribution board 3. Four TR boards (TR0, TR1,TR2 and TR3) 4. Signal processor board PC acts a central processing unit – 1. Performing processing of image data 2. Serves as a main controller of the E-Box and system user interface

36. SOFTWARE ARCHITECTURE It consists of four major executables: Beam processing control (E Box) Signal processing control (E Box) Image modalities (PC) Image management and review (PC)

37. ULTRASOUND SYSTEM BLOCK DIAGRAM

38. 1. DISPLAY (System monitoring) HD11 system monitor is an RGB, 15-in FST display monitor Has an integrated microphone and supports six different video formats 2. BEAM FORMER Synchronizes the generation of ultrasound waves Scan and focus the transmitted beam Amplifies the returning Echoes Compensate for attenuation PARTS OF ULTRASOUND MACHINE

39. 3. PULSER Generates the voltages that drive the transducer Depends on the PRF( pulse repetition frequency) and affects the frame rate (FR) 4 . T/R SWITCH AND CHANNELS Perform the functions of transmit and switch Drives voltage from the pulser to the transducer

40. 6. TRANSDUCER E lectronic device that converts energy from one form to another. Ultrasound transducers converts electrical pulse into sound pulse and sends sound pulse into the body and listens for returning echoes generated by tissue interfaces and again converts sound pulse into electrical signal . Piezoelectric transducers are used in ultrasound.

41. A TRANSDUCER PROBE

42. TRANSDUCER SELECTION Exam type Body constitution Acoustic window/ Access Field of view Mode requirements: Doppler, Color etc.

43. TYPES OF CONNECTOR There are three types of connector slots in HD 11 ultrasound system: C artridge connector Explora connector Pencil connector Cartridge connector Pencil connector Explora connector

44. TRANSDUCER PROBES Probes are generally described by the size and shape of their face(“footprint”). There are 3 basic types of probe used in emergency and critical-care ultrasound. Linear array probe Curvilinear array probe Phased array probe

45. STRAIGHT LINEAR ARRAY PROBE It is designed for superficial imaging Crystals are aligned in a linear fashion within a flat head and produce sound waves in a straight line. Image produced is rectangular in shape Probe has higher frequency ( 5-13 MHz) providing better resolution and less penetration.

46. CURVILINEAR PROBE Also called convex probe Used for scanning deeper structures Crystals are aligned along a curved surface which results in a wide field of view Image created is sector shaped. Probes have frequency between 1-8 MHz allowing greater penetration and less resolution. Generally used in abdominal and pelvic applications .

47. PHASED ARRAY PROBE Crystals are grouped closely together. Sound waves originate from a single point and fan outward, creating a sector-type image. Has smaller and flatter footprint than the curvilinear probe. Probe has frequency between 2-8 MHz Generally used for cardiac imaging, Imaging between ribs and small spaces.

48. ENDOCAVITARY PROBE Has a curved face Has higher frequency than curvilinear probe ( 8-13 MHz) Probe’s elongated shape allows it to be inserted close to the anatomy being evaluated. Curved face creates a wide field of view of almost 180 High frequency provides superior resolution Most commonly used for gynecological applications

49. SPECIAL PROBES Linear intraoperative probe Transesophageal probe Used in cardiology, surgery Used in neurosurgery Volume convex probe Used in obstetrics

50. TRANSDUCER TYPES OF HD11 U/S SYSTEM 1. CURVED ARRAY TRANSDUCERS Connector Applications C5-2 Cartridge Abdominal, OB/GYN C8-4v Cartridge Endovaginal OB/GYN C8-5 Explora Abdominal, Neonatal head, OB/GYN, Paediatric C9-4 Explora Abdominal, OB/GYN, Paediatric C9-5ec Explora Endocavity

51. 2. DOPPLER PENCIL TRANSDUCERS Connector Applications D2cwc Pencil Cardiac D2tcd Pencil Transcranial doppler D5cwc Pencil Cardiac, vascular 3. LINEAR ARRAY TRANSDUCERS Connector Applications L8-4 Explora Abdominal, Musculoskeletal, Vascular, Small parts L12-3 Cartridge Abdominal, , Musculoskeletal, Vascular, Small parts L12-5 Explora Abdominal, Small parts, Vascular L15-7io Explora Cardiac, Intraoperative, Musculoskeletal

52. 4. SECTOR ARRAY TRANSDUCERS Connector Applications PA 4-2 Cartridge Abdominal, cardiac, OB/GYN, TCD S3-1 Explora Abdominal, cardiac, TCD, OB/GYN S8-3 Explora Cardiac, Neonatal head, OB/GYN, Paediatric abdominal S12-4 Explora Paediatric cardiac, Paediatric abdominal, Intraoperative, Neonatal head Connector Applications S7-2omni Explora Transesophageal S7-3t mini- multi Explora Transesophageal T6H Transesophageal 5. TEE TRANSDUCERS

53. WORKING PROCEDURE

54. APPLICATIONS Obstetrics and Gynecology 1. Measuring the size of the fetus 2. Determining the sex of the baby 3. Monitoring the baby for various procedures Cardiology 1. Seeing the inside of the heart to identify abnormal functions 2. Measuring blood flow through the heart and major blood vessels Urology 1. Measuring blood flow through the kidney 2. Locating kidney stones 3. Detecting prostate cancer at early stage

55. RISKS The two major risks involved with Ultrasound are: Development of heat : Tissues or water absorb the ultrasound energy which increases their temperature locally. Formation of bubbles ( cavitation): When dissolved gases come out of solution due to local heat caused by Ultrasound.

56. BENEFITS Images muscle, soft tissues very well Renders “live images” where most desirable section is selected S hows structure of organs No long-term side-effects Widely available and comparatively flexible Highly portable Relatively inexpensive Spatial resolution is better in high frequency ultrasound scanners

57. LIMITATIONS S onographic devices have trouble penetrating bone Sonography performs very poorly when there is a gas between the transducer and organ of interest Body habitus has large influence on image quality Method is operator-dependent No scout image as there is with CT and MRI