1. Limited Ultrasound Training
Developed by:
Dr. David Ying, Radiologist
Michelle Zehr, RN, BSN
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The following information is the copyrighted intellectual property of CompassCare Pregnancy Services, and may not be used by any party without the expressed written permission of CompassCare.

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Objectives
Describe indications for limited ultrasound exams
Understand and apply the basic principles of ultrasound physics and instrumentation
Understand the implications for patient care from ultrasound findings
provide appropriate education regarding the ultrasound procedure, its purpose and its limitations
Understand and apply these basic principles necessary for proficiency in imaging technique
Perform limited ultrasound examinations, including identification of fetal cardiac activity, and fetal presentation, using the correct measurement techniques to determine gestational age
Evaluate the patient’s response to ultrasound findings and implement appropriate nursing interventions based on that response
Document all ultrasound findings to the responsible health care provider per CompassCare policy and procedure
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3. Ultrasound Physics and Instrumentation
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4. Sound Wave Propagation
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5. Electromagnetic Wave: Radio Wave, Light Wave
Does not require medium for transmission and is measured in wavelength (distance between two adjacent vibrations)
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6. Mechanical Wave: Sound Wave
Transmitted through a medium such as air, water, solid and is measured in frequency (vibrations per second), or hertz (Hz=1 vibration/second)
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Waveforms Compared
Light
370 trillion to 750 trillion Hz
Spectrum of visible light ranges from 780nm to 380nm (Nanometer=I billionth of a meter)
Ultraviolet, X-ray and gamma rays have progressively shorter wavelengths
Infrared and radio microwave have progressively longer wavelengths
Sound
spectrum ranges from 20-20,000 Hz.
Ultrasound is in the range higher than 20,000 Hz
Medical ultrasound is in the range of 2-7 megahertz (MHz= 1,000,000 Hz)
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Useful terms:
Attenuation: Weakening of sound as it propagates through a medium
Causes:
Absorption, reflection, and scattering
Decibels (dB): units used to relatively quantify intensity of sound for comparison purposes
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Frequency: cycle/vibrations per second expressed in hertz (Hz)
1 Hz=1 vibration/second
Intensity:
Power (energy/time)/area= Watts/area
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Incidence: Direction of sound wave travel to the boundary between 2 media
e.g. perpendicular, oblique angle
Impedance:
= density of medium X propagation speed
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Inverse square law: intensity of sound varies inversely with the square of the distance from the source
Speed of propagation: depends on the medium. The more solid (high elasticity or stiffness) medium allows faster speed. Decreasing speed in solids, water, air.
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Boundary behavior: (interface between media)
Reflection: bouncing back from the boundary
Specular: when the boundary is smooth and flat
Scattering: when the boundary is rough and uneven
Refraction: crossing the boundary with change in direction
Transmission: going through the boundary
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Transducer Functions
A transducer converts one form of energy to another.
An ultrasound transducer converts sound wave energy to electric energy and vice versa.
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14. Composition of an U/S Probe
Piezoelectric element:
Material that is capable to convert pressure and electricity, such as ceramic or quartz
Element (crystal) in linear, curved (sector) and phased array
Damping/matching, material:
To improve transmission
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Operating Frequency
The higher the operating frequency, the thinner the transducer element, the greater the attenuation (or the lesser the depth penetration)
3.5 or 5.0 MHz for the abdominal probe
5.0 or 7.5 MHz for the internal/vaginal probe
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Beam Focusing:
Focusing electronically to improve resolution at various depths
Coupling Medium:
Gel that is used to eliminate air at transducer-skin interface to maximize ultrasound transmission
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Types of transducers
External:
Linear array
Flat top, curved top, pointed top
Sector
Internal (endo-):
Rectal, vaginal, esophageal, vascular, etc.
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Penetration:
Depth of images obtained is directly related to:
Attenuation by the medium
Power of the beam
Frequency (Hz), inverse relationship
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19. Time-Gain Compensation
To provide a more uniform image by “compensating” the weaker signals from deeper (further from the transducer) tissue as a result of longer time and greater attenuation
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Resolution
Detail
Contrast
Temporal
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Detail:
Degree of separation of structure echoes or signals
Axial resolution: along the beam direction
Lateral resolution: perpendicular to the beam direction
Increased frequency means increased resolution but decreased penetration
(useful U/S frequency is 2-15mHz)
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Contrast:
Improves with:
Greater gray scale
(U/S signal strength vs. B-W scale)
Color display
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Temporal:
Improves with higher frame rate
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Artifacts
Types:
False (erroneous) signals or images
Missing signals or structures
Wrong locations
Incorrect sizes
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Artifact Causes:
Section Thickness:
Ultrasound beam is
3-D while the displayed image is
2-D
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Artifact Causes:
Acoustic speckles:
Interference effects of scattered sound beams and echoes from various tissues and directions of the ultrasound beam.
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Artifact Causes:
Reverberations:
Repeated echoes occur between the transducer and a strong reflector.
Mirror image is a form of reverberation artifact and formed with a strong reflector within a tissue.
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Artifact Causes:
Refraction:
Laterally misplaces or mis-shapens a structure when a beam is refracted in the tissue.
e.g. Observed depth of object in water.
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Artifact Causes:
Artifact Causes:
Speed error:
Axially misplaces a structure when the speed of the ultrasound beam is miscalculated
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Artifact Causes:
Artifact Causes:
Shadowing:
Decrease or loss of ultrasound signal behind a strongly reflecting or attenuating structure, or from the edge of a refracting structure.
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Artifact Causes:
Artifact Causes:
Enhancement:
Increase in echo signals behind a poorly attenuating structure.
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Artifact Causes:
Artifact Causes:
Grating Lobes:
False duplicated and miscalculated images created by side beams in directions different from the primary beam.
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33. Proficiency in imaging technique:
Patient Interaction
Professional, but friendly
Courteous
Respectful, esp. in regard to privacy
Informative regarding the procedure, but not the diagnosis
Proper instrument settings probes and gel.
Correct transducer frequency and type.
Adjust field size, near and far gain settings
Contrast, gain and TGC slope
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Scanning Technique:
Patient position:
Supine, prone and lateral, to provide shortest distance to the anatomic structure of interest
Image:
In traditional long (sagittal) and transverse (axial) planes. Also oblique, coronal and angle planes if necessary.
Identify anatomic structures and landmarks.
Know the pathology (abnormal findings)
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Safety:
There is no known risk associated with diagnostic ultrasound since first used in the 70’s.
The possibility of adverse bio-effects from an even low level, delayed harm of the U/S energy transfer can not be absolutely denied.
Minimize use exposure time and intensity of the ultrasound without sacrificing the proper gathering of diagnostic information.
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Patient Education
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37. Indication for testing:
Confirm the viability of pregnancy.
visualize your baby’s heartbeat within the uterus.
31% of all pregnancies are not viable. (it could be miscarriage, ectopic pregnancy, or multiple other reasons why the pregnancy hormone would be in the urine).
Confirming how far along she is related to her last menstrual period (LMP).
Explain what you anticipate before the exam.
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38. With each week, size doubles and development is much more defined
Gestational Age
Gestational Sac (GS)
Yolk Sac (YS)
Fetal Heart Motion
Movements
Development
(visualized)
3-4 wks + -
4-5 wks ?
5-6 wks
6-7 wks
8-9 wks
arms, legs
9-10 wks
face
11 wks
arms & legs moving, jaw lines, fingers and toes
12 wks
More clarity
With each week, size doubles and development is much more defined

39. Scope of Information Provided:
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40. See What You Expect To See: Confirm Viability
Reiterate what you were able to see.
Explain the development that is there that you can’t see.
Show the model of comparison to where they are, and where they’ll be soon.
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41. Saw What you Expect to See Unable to Confirm Viability: Before 6 Weeks
Say, “You are __far along and I can not confirm viability. I see ___ and would expect to see that.”
i.e.: “You are 5 weeks today by the measurements, I see the yolk sac (point it out), but can not confirm viability because I can not see the heart beat today. We will need to reschedule you for next week in order to confirm viability.”
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42. Didn’t See What You Expect to See Unable to Confirm: After 6 Weeks
Say to the patient, “I do not see what I expect to see.”
Reiterate what you would have expected and explain you are not seeing that today.
Follow P&P
You want to be sure to review policy and procedure manual for this until you have it memorized, which will probably be forever since I wrote the policy and still have to look back.
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43. What this exam does not include:
Sex of the baby
Diagnosis of pregnancy from an RN or Sonographer
Diagnosis/Opinion of what is wrong if you do not see what you expect to see (to the pt.)
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44. Criteria for Rescheduling an Ultrasound