SPI sonographer in clinical setting/quality assurance

Quality assurance

The routine, periodic evaluation of an ultrasound system to guarantee optimal image quality

• must be performed periodically and routinely

Four requirements for a quality assurance program

• assessment of system component

• repairs

• Preventative maintainence

• Record keeping

Five goals of quality assurance

• guarantee proper operation of the system

• Detect gradual changes

• Minimize downtime

• Reduce the number of non diagnostic exams

• Reduce the number of repeat scans

Several devices enable the sonographer to perform quality assurance

3 of these devices are discussed

• tissue equivalent phantom

• Doppler phantom

• Beam profile/slice thickness phantom

Proper methods for quality assurance programs are

• test under known, defined conditions

• Use constant instrument settings

• Use a phantom with measurable characteristics

• Image in an identical environment

Tissue equivalent phantom

Have ultrasonic features similar to soft tissue

• used to evaluate grey scale and tissue texture

• Used to evaluate multi focus and adjustable focus phased array transducers

Tissue equivalent phantoms are similar to soft tissue in the following ways:

• speed of sound

• Attenuation

• Scattering characteristics

• Echogenicity

Why is grey scale evaluated with tissue equivalent phantom

Because it contains small scatterings that act like soft tissue

Doppler phantoms

• Vibrating string

• Moving belt

• Flow phantom

What do Doppler phantoms asses

The characteristics of all Doppler modalities, including pulsed, continuous wave, color, and power mode

Slice thickness phantoms

Determines elevational resources

• measures the beam geometry perpendicular to the imaging plane

• Thicker slices diminish spatial resolution (image detail) and reduce the ability to visualize small low contrast reflectors

• When overly thick, cystic structures may appear filled in

Two forms of sensitivity are

• normal

• Maximum

Normal sensitivity

All the pins, solid masses, and cystic structures in the test phantom are accurately displayed

• output power, TGC, and amplification are adjusted to establish normal sensitivity

Maximum sensitivity

Evaluated with the output power and amplification of the system set to the maximum practical levels

• a tissue equivalent phantom is imaged, and the depth of the tissue like texture on the display is measured

Dead zone

The region close to the transducer where images are inaccurate

• extends from the transducer to the shallowest depth from which meaningful reflections appear

• Info within this zone is unreliable and may not be used

The dead zone results from

The transducer ringing and the time it takes the system to switch from the transmit to the recieve mode

How is the dead zone assessed

With the shallowest series of pins in a test object

• with the tissue equivalent phantom, the dead zone is the shallowest depth at which uniform tissue texture appears

Higher frequency transducer have a thinner dead zone than

Lower frequency transducers

What does an acoustic stand off, or gel pad, allow for?

Accurate imaging of important superficial structures

• a 50 cc bag of IV fluid may also be used

An increasingly deeper dead zone may indicate what?

A cracked crystal, detached backing material, or a longer pulse duration

Registration accuracy

The ability of the system to place reflections in proper positions while imaging different orientations

Range accuracy

Vertical depth calibration, describes the systems accuracy in placing reflectors at correct depths located parallel to the sound beam

The accuracy of reflector depth positioned in A mode, M mode, B mode, and 2D imaging is called

Depth calibration

If differences appear between the ultrasound scan and the actual pin locations in the test object, the error may be caused by

• system malfunction or

• The speed of sound in phantom is different than 1540 m/s

Horizontal calibration

The systems ability to place echoes in their correct position when the reflectors are perpendicular to the sound beam

Distance measurement accuracy

Components of the ultrasound system used to measure distances also require periodic evaluation

• digital calipers should be checked in both vertical and horizontal directions

Focal zone

Surrounds the focus

• lateral resolution is excellent in this zone bc the beam is narrow

Focus

Is the depth at which the intensity is the highest and the beam is the narrowest; focal zone surrounds the focus

Axial resolution

Smallest distance at which two pins positioned parallel to the sound beam are displayed as two distinct echoes

• evaluated by scanning sets of successively closer spaced pins within the phantom

Lateral resolution

The minimum distance at which two side by side pins are displayed as two distinct images

• Another method is to measure the width of reflections on the display that are created by the point targets in the phantom

Compensation operation or uniformity

The systems ability to display similar reflectors in the phantom with echoes of equal brightness

Mock cysts and solid masses

The tissue equivalent phantom is used to evaluate the dimensions, texture, and fill in of cysts

• the system should accurately display hollow structures as anechoic and solid structures as hyperechoic

Display, hardcopy output, and grey scale dynamic range

adjusting the systems output power and amplification should produce changes in the grey scale display

Adjustments to the output power and amplification of the system should

Alter the appearance of the image on the systems display and all output devices

Adjustments on a single display device (such as brightness or contrast of a monitor) should

Alter the image on that particular device only

Major principles of medical ethics

• respect for autonomy

• Nonmaleficence

• Beneficence

• Justice

Respect for autonomy

The patient has the capacity to act intentionall, with understanding and with free wil

• this principle is the basis for informed consent

Non maleficence

Requires that we avoid needless harm or injury to the patient

• imposing careless or unreasonable harm on a person or negligence

Beneficence

The actions of health care providers should benefit the patient

Justice

Fairness, people who are equals should qualify for equal treatment regardless of age, gender, educational background and other factors

Complete informed consent generally includes

• the nature of the procedure

• Reasonable alternatives

• The risks, benefits, and uncertainties related to each alternative

• Assessment of patients understanding

• The patients acceptance

Revocation of consent

A patient may withdraw previously granted consent at any timee

Upon meeting a patient

• Intro yourself, explain the procedure and your role in performing it

• Identify the patient

• If possible use patients wrist band, if no wrist band you can include the patient in identifying themselves

• If patient is sedated and arrives without wrist band, call the nurse. The patient may be sent back to the floor and the study be rescheduled when the patient has appropriate identification

• It is inappropriate for a sonographer to cancel the exam, ordering or canceling exams is outside the sonographers scope of practice

Ergonomics

Studies the interaction between the sonographer, patient, and equipment in order to optimize the well being of sonographers

Sonographers must be

In good physical shape and have full use of their hands, wrists, and shoulders

3 out of 4 sonographers experience pain from work related musculoskeletal injury

3 out of 4 sonographers experience pain from work related musculoskeletal injury

Nearly 20% of sonographers end their career as a result of

Musculoskeletal injury

Causes of injury

Repetitive motions

Forceful or awkward movements

Poor posture

Improper position

Strain

And pressure on joints for extended periods

Sonographers should hold the probe using a whole hand grip called

Palmar grip

Standard precautions

A set of guidelines to minimize the exposure and risk of health care workers when in contact with patient

• based on the idea that all patients should be treated as potentially infectious

Universal precautions

Originally developed in the 1980s to minimize the risk of patients to HIV, HBV and other blood born pathogens

To what do standard precautions apply?

All body fluids

Secretions

Excretions

Mucous membranes

Airborne particles

nonintact skin

and to any items soiled with these substances

OSHA

Occupational standard and health administration

What percentage of sonographers are thought to experience musculoskeletal pain related to work?

80%

Billion

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Billions & billionths

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Three acoustic variable

Pressure

Density

Distance

Acoustic parameters

• period

• Frequency

• Amplitude

• Power

• Intensity

• Wavelength

• Propagations speed

Lung speed

500 m/s

Fat speed

1,450 m/s

Soft tissue speed (average)

1540 m/s

Liver speed

1560 m/s

Blood speed

1560 m/s

Muscle speed

1600 m/s

Tendon speed

1700 m/s

Bone speed

3500 m/s

Air speed

330 m/s

Water speed

1480 m/s

Metals speed

2000-7000 m/s

Frequency & period

Inversely related

Amplitude and power

Directly

Amplitude and intensity

Directly

Power and intensity

Directly

Wavelength and intensity

Unrelated

Wavelength and frequency

Inversely

Acoustic velocity and density

Inversely

Elasticity and speed of sound

Inversely

Acoustic velocity and compressibility

Inversely

Stiffness and sound speed

Directly

Frequency and intensity

Unrelated

Frequency and sound speed

Unrelated

Power and frequency

Unrelated

Pulse duration directly proportional to

• the number of cycles in pulse

• To period

Pulse duration inversely related to

Frequency

Spatial pulse length is directly proportional to

• number of cycles in pulse

• To wavelength

Spatial pulse length inversely related to

• frequency

PRP is unrelated to period, it is only related to

DEPTH