Introduction to Ultrasound Principles Mani Montazemi, RDMS Baylor College of Medicine Division of Maternal-Fetal Medicine Department of Obstetrics and Gynecology Manager, Maternal Fetal Center Imaging Texas Children s Hospital, Pavilion for Women Houston Texas & Clinical Instructor Thomas Jefferson University Hospital Philadelphia, Pennsylvania B A D Basic Principles of Ultrasound Ultrasound diagnostically is used in 2 ways Basic Principles of Ultrasound Ultrasound diagnostically is used in 2 ways Anatomic information Basic Principles of Ultrasound Ultrasound diagnostically is used in 2 ways Anatomic information Blood flow information What is Ultrasound? What is Ultrasound? 1
Basic Principles of Ultrasound What is sound Sound is a form of energy Basic Principles of Ultrasound What is sound Sound is a form of energy What is energy Energy is the capacity to do work Moving an object, heating the room, lighting electricity Basic Principles of Ultrasound Sound is mechanical energy transmitted by pressure waves in a material medium Sound is not electromagnetic Matter must be present for sound to travel How Does an Ultrasound Instrument Work? Pulsed-echo Principle The energy within a pulsed-echo system is electrical, but the energy in the patient s body is sound, which is mechanical What is a Transducer? Converts one form of energy into another form 2
Video Clip - Transducer Transducer Frequency 5.0 3.5 2.25 2.25 MHz 3.5 MHz 5-6 MHz 7.5-10 MHz 9.0 MHz 12-17 MHz Transducer Configurations Curved linear Straight linear Conventional sector Microsector Endocavity Intraoperative Image Configurations Linear Curved Sector Transducer Configurations Mechanical Phased array Transducer Configurations Mechanical moving parts Wobbler or rotating Single or multi-element Mechanical beam steering & focusing Motor driven/fluid filled scan head FOV is sector Single or multi-frequency 3
Transducer Configurations Phased array no moving parts Flat linear Curved linear Sector Curved Linear Array Transducer Multi-element Elements arranged in an arc and are sequentially pulsed FOV is trapezoidal-sector Produce larger FOV Benefits: High quality imaging Faster frame rate Electronic focusing Video Clip - Transducer Categories of Sound Infra Sound Audible Sound below 20 Hz 20-20,000 Hz Ultrasound Above 20,000 Hz Sound is categorized according to the frequency of vibration per seconds Frequencies Used For Medical Diagnostic Ultrasound Are Normally Above 1 MHz One cycle / second = one Hertz (Hz) Resolution: What is it? Clarity & sharpness of an ultrasound image The capability of clearly distinguishing two points located close to each other on the sonogram One thousand cycles / second = one Kilohertz (khz) One Million cycles / second = one Megahertz 4
Video Clip Safety Safety - Prudent Use Minimize risk Minimize exposure Medical indication only Minimize exposure time Minimize exposure output Ultrasound Safety Prudent use dictates that the principle of ALARA be observed and the ultrasound power levels be maintained As Low As Reasonably Achievable, in order to provide the maximum benefit / risk ratio Output Display Values Power Thermal Index heat Ratio of the in-situ power to the acoustic power required to raise tissue temprature by 1 o C Mechanical Index cavitation Acoustic output in terms of the likelihood of tissue cavitation 5
Caution Image Orientation & Scanning Planes Longitudinal Transverse Oblique Scanning Planes Sagittal Scan Longitudinal, vertical planes Divide the body into left & right Sagittal Scan Sagittal Scan H A P F 6
Sagittal Scan Sagittal Scan Sagittal Scan Sagittal Scan Anterior Maternal Head Maternal Feed Posterior Sagittal Scan Sagittal Scan 7
Anterior Sagittal Scan H F Posterior Anterior H F Posterior Transverse Scan Horizontal, transaxial planes Divide the body into superior & inferior 8
Transverse Scan Transverse Scan R A P L Transverse Scan Transabdominal Transverse Transverse Scan Transverse Scan Twin Pregnancy 9
Oblique Scan Oblique Scan Oblique planes Inclined from the standard planes In any direction Artifacts Posterior Enhancement Acoustical Shadowing Attenuation Reverberations Refraction Posterior Enhancement Increased intensity in echoes from reflectors behind a structure that weakly attenuates sound Classical feature of fluid Posterior Enhancement Posterior Enhancement UT OV 10
Acoustical Shadowing Acoustical Shadowing Marked decrease in intensity of echoes from reflectors that lie behind a structure that is strongly reflecting or attenuating sound Complete lack of acoustical & anatomical information in the area of shadowing Acoustical Shadowing Acoustical Shadowing Head Acoustical Shadowing Acoustical Shadowing 11
Acoustical Shadowing Attenuation Reduction of the sound beam s amplitude and intensity as it travels through a medium Attenuation Attenuation Normal Attenuation Reverberations When 2 or more reflectors in the sound path cause multiple, repetitive artifactual echoes 12
Reverberations Reverberations Video Clip Artifacts Cervix US Appearance Artifacts Posterior Enhancement Acoustical Shadowing Attenuation Reverberations Refraction Echogenicity Intensity of echoes reflected by tissues or structures from inside the body 13
Echogenicity Liquids Solids Vessels & Ducts Soft Tissue Bone Gallbladder Fibrous Cysts Gall Stone Urinary Bladder Tumors Kidney Stone Cysts Polyps & Lesions Calcific Plaque Echogenicity of a structure is described relative to surrounding or adjacent tissue Echogenicity Anechoic Anechoic Hypoechoic Hyperechoic Sonolucent No internal echoes Anechoic Anechoic 14
Anechoic Anechoic Hyperechoic Hyperechoic High intensity echoes Increased echogenicity Echogenic Hyperechoic Hyperechoic 15
Hypoechoic Hypoechoic Low intensity echoes Decreased echogenicity Clotted Blood Hemoperitoneum Homogeneous Heterogeneous Echotexture Homogeneous Homogeneous Uniform echoes Fine, smooth texture 16
Homogeneous Heterogeneous Non-uniform echoes Irregular texture Heterogeneous Heterogeneous Normal Normal Cystic Solid Complex Types of Masses Cystic Masses Anechoic Fluid filled Smooth, well defined margins Posterior enhancement 17
Cystic Masses Cystic Masses Cephalocele Solid Masses Solid Masses Contains varying amounts of internal echoes Regular or irregular margins Poorly defined back wall Posterior attenuation of sound Distal acoustic shadow Uterine Leiomyoma US Findings Discrete solid mass single or multiple Uterine Leiomyoma US Findings Variable echogenecity hypoechoic, hyperechoic 18
Uterine Leiomyoma US Findings Diagnostic Challenge Solid Masses Complex Masses Predominantly Cystic Mostly cystic Posterior enhancement Internal echoes Thin or thick septations Thin or thick walls Hemorrhagic Cyst Mural Nodule vs. Clot Lace-like pattern of internal echoes 19
Mural Nodule vs. Clot Complex Masses Normal Sacrococcygeal Teratoma Complex Masses Complex Masses Cervical Teratoma Complex Masses Complex Masses Predominantly Solid Mostly echogenic Internal cystic changes Posterior attenuation Cystic Lymphangioma 20
Complex Masses Describing A Mass Size Shape, borders, wall Acoustic properties (cystic, solid, complex) Posterior enhancement or attenuation Location Normal Hepatoblastoma How Would You Describe This Mass? How Would You Describe This Mass? In the right adnexa TRV Pelvis How Would You Describe This Mass? How Would You Describe This Mass? In the right adnexa there is a round, well marginated thin walled mass with a sharply defined back wall, In the right adnexa there is a round, well marginated thin walled mass with a sharply defined back wall, thin internal septations, 21
How Would You Describe This Mass? How Would You Describe This Mass? In the right adnexa there is a round, well marginated thin walled mass with a sharply defined back wall, thin internal septations, low intensity echoes, In the right adnexa there is a round, well marginated thin walled mass with a sharply defined back wall, thin internal septations, low intensity echoes, and excellent posterior enhancement. How Would You Describe This Mass? Basic System Overview In the right adnexa there is a round, well marginated thin walled mass with a sharply defined back wall, thin internal septations, low intensity echoes, and excellent posterior enhancement. The features are those of a complex, predominantly cystic mass. Patient Data Entry Patient Data Entry 22
Transducer / Exam Selection Transducer / Exam Selection Transducer Selection Probe Handling Resolution vs. Penetration Right frequency for penetration Highest frequency for resolution? Probe Handling Sagittal Probe Handling Sagittal Incorrect Incorrect 23
Probe Handling Sagittal Probe Handling Sagittal Incorrect Correct Probe Handling Sagittal Probe Handling Transverse Incorrect Probe Handling Transverse Probe Handling Transverse Incorrect Correct 24
Probe Handling Don t Probe Handling Basic Controls Freeze Overall Gain TGC Depth Focus Overall Gain Overall Gain - Increase An increase or decrease of the gain will change the brightness of the image Affects entire field of view 25
Overall Gain - Increase Overall Gain - Increase Overall Gain - Decrease Overall Gain - Decrease Overall Gain - Decrease Overall Gain 26
Time Gain Compensation These slide pots controls amplification of returning echo signals at specific depths The TGC compensates for loss in signal strength as the ultrasound beam passes through an organ Affects specific portions of the field of view Time Gain Compensation Near Field Mid Field Far Field Time Gain Compensation Time Gain Compensation Brighter Darker Time Gain Compensation Time Gain Compensation Brighter 27
Time Gain Compensation Time Gain Compensation Darker The diagnosis is only As good as the information your image provides Time Gain Compensation What Constitute a Good Image? What Constitute a Good Image? 28
Controls the depth of field of view Depth Depth When the image depth is changed, the field of view increases or decreases Too Small Depth Just Right Too Big Focus Transmit Zone Highlights area of interest Place at or slightly below area of interest Focus Region of minimum beam width in a focused ultrasound beam 29
Focus Focus Don t Get Fooled By Poor Technique Pay Attention to Focal Zone Ancillary Functions Cine Loop Stores and displays images with no loss of quality M-Mode Useful in evaluating motion and velocity of moving structures Fetal Heart Motion 30
OB Calculations Sac Diameter Highlight and Select OB Calc OB Calculations Select [Single/A/B] soft key if needed OB Calculations Highlight and select Biometry or AFI Measurements Calipers, Add Caliper Individual measurements Trace, Ellipse Measures area and circumference OB Worksheet Edit or Delete Measurements Enter Previous Exam Data Enter Comments 31
OB Worksheet OB Worksheet OB Worksheet Thank You 32