ultrasound worksheet Flashcards
- What are the properties of sound waves and what equation do we use to express them?
There are five main characteristics of sound waves: wavelength, amplitude, frequency, time period, and velocity
Equation used is –
Velocity = frequency x wavelength
- Name the FOUR ways that ultrasound is attenuated.
- Absorbed
- Reflected
- Refracted
- Scattered
- What is the medical ultrasound frequency range?
Is a range of sound frequencies from 2MHz to 20 MHz
- How does tissue type affect the speed of sound and give examples of air, fat and bone in m/s?
Tissue type affects the speed of sound due to its density and elasticity. The propagation speed of sound is higher in tissues with increased stiffness and reduced density.
• air: 330 m/sec
• fat: 1450 m/sec
• bone: 4080 m/sec
- What is the piezoelectric effect
Piezoelectric Effect is the ability of certain materials to generate an electric charge in response to applied mechanical stress.
- Describe the ultrasound imaging pathway starting with the transducer to the resultant image.
A trained technician (sonographer) presses a small, hand-held device (transducer) against the area being studied and moves it as needed to capture the images. The transducer sends sound waves into your body, collects the ones that bounce back and sends them to a computer, which creates the images.
- What is acoustic impedance?
Acoustic impedance is the product of the density and speed of sound in the tissue.
- What are the benefits of ultrasound imaging? List good clinical applications
- Uses non-ionizing radiation which means it doesn’t have the same risks as x-rays
- Painless
- Captures soft tissue which cannot be seen clearly on an x-ray
- Widely accessible and less expensive than other methods
- Easy to use
- Best modality for diagnosis and monitoring of pregnant woman and their unborn babies
- Uses real time imaging, which means it can be used in procedures such as needle biopsies and fluid aspiration.
- What are the weaknesses of ultrasound imaging?
- Ultrasound waves are disrupted by air or gas. Therefore, ultrasound is not an ideal imaging technique for the air-filled bowel or organs obscured by the bowel
- Ultrasound has difficulty penetrating bone and, therefore, can only see the outer surface of bony structures and not what lies within
- Large patients are more difficult to image by ultrasound because greater amounts of tissue weaken the sound waves as they pass deeper into the body and need to return to the transducer for analysis.
- Cannot determine is something is malignant or non-malignant
- What are the biological effects of ultrasound?
- Thermal effects – controlled by thermal indices setting (TI)- heating
- Mechanical effects – controlled by mechanical indices setting (MI) – cavitation (bubble formation, oscillation and collapse)
- What are the BMUS safety guidelines for ultrasound imaging in the UK?
• Medical ultrasound imaging should only be used for medical diagnosis.
• Ultrasound equipment should only be used by people who are fully trained in its safe and proper operation. This requires:
o an appreciation of the potential thermal and mechanical bio-effects of ultrasound,
o a full awareness of equipment settings
o an understanding of the effects of machine settings on power levels.
• Examination times should be kept as short as is necessary to produce a useful diagnostic result.
• Output levels should be kept as low as is reasonably achievable whilst producing a useful diagnostic result.
• The operator should aim to stay within the BMUS recommended scan times (especially for obstetric examinations).
• Scans in pregnancy should not be carried out for the sole purpose of producing souvenir videos or photographs.
- How does ALARA apply to ultrasound imaging? as low as reasonably achievable).
- By using minimum power output
- Keeping the scanning time to minimum
- Not leaving the transducer/ probe on the skin surface if not scanning
- Describe the Doppler effect in ultrasound imaging and when can we apply this in clinical imaging?
Doppler is a change in sound frequency that shows the speed and direction of blood flow. We can apply this in clinical imaging when examining vascular emergencies such as testicular or ovarian torsion.
Doppler ultrasound helps the doctor to see and evaluate:
• blockages to blood flow (such as clots)
• narrowing of vessels
• tumors and congenital vascular malformations
• reduced or absent blood flow to various organs, such as the testes or ovary
• increased blood flow, which may be a sign of infection
• Color Doppler ultrasound is also called color-flow ultrasound
- When can ultrasound image artefacts be useful in diagnosing a patient and when are artefacts not useful? Give examples
- Shadow artifact is very useful for diagnosing gall stones
- comet tail affect is useful
- tiny stone calcification can be seen through tinglicining
- mirroring artefacts
- speed artefact
- reverberation artefact
- interpretation errors
- obscure normal anatomy, disease or a pathology
