Bioeffects Flashcards
What are bioeffects?
Effects of sound on living tissue created by intense sound beam
What is a hydrophone/microprobe?
Similar to a small hypodermic needle with a tiny piece of PZT attached to its end; connected by a wire to an oscilloscope
What does a calibrated hydrophone provide?
Known relationship between the acoustic pressure signal and the voltage created by the PZT
What is the purpose of a membrane hydrophone?
Constructed from a very thin membrane of PZT plastic; detects intensity
What is the highest output power in ultrasound?
Pulsed Doppler
What is the lowest output power in ultrasound?
Gray scale imaging
What is the intermediate output power in ultrasound?
CF Doppler and M-mode
What is radiation force/feedback?
Force exerted on tissue by the sound beam; relates to power in the beam
What are the three devices that measure output of transducer by absorption?
- Calorimeter
- Thermocouple
- Liquid Crystal
What is the function of a calorimeter?
Measures total power/entire intensity in a sound beam through absorption
What does a thermocouple do?
A tiny electronic thermometer that can measure intensity at a particular location
How do liquid crystals respond to temperature?
Change color based on their temperature
What is the risk-benefit relationship in clinical ultrasound?
Benefits to the patient must outweigh the risks of the exam
True or False: Diagnostic ultrasound has known harmful bioeffects.
False
Under what circumstances can bioeffects be beneficial?
Under controlled circumstances
What is the primary mandate regarding clinical ultrasound?
Benefits to the patient must outweigh the risks
What is dosimetry?
The science of identifying and measuring the characteristics of an ultrasound beam relevant to its potential for producing biological effects
What does ‘in vivo’ refer to?
Within the living body
What are the main characteristics measured by a hydrophone?
- Period
- PRP
- PRE
- PD
- Amplitude
- DE
What is the process of conversion of energy to heat called?
Thermal energy conversion
What is JAcousto-Optics?
Based on the interaction of sound and light
What is a Schlieren system used for?
A shadowing system that visualizes the shape of a sound beam in a medium
What is the term for biological effects studied outside the living body?
In vitro
What approach searches for a relationship between cause and effect in bioeffects research?
Mechanistic Approach
What approach searches for a relationship between exposure and response in bioeffects research?
Empirical Approach
What type of cavitation involves stable oscillating bubbles?
Stable cavitation
What is the term for the implosion of gaseous nuclei, bubbles, or contrast agents?
Cavitation
True or False: The strongest conclusions in bioeffects research are made when mechanistic and empirical conclusions agree.
True
What mechanism involves very high intensities causing genetic damage and cell death?
Nonthermal Mechanism
What is the thermal index for soft tissue referred to as?
TIS
What is the thermal index for bone referred to as?
TIB
What is the thermal index for cranial bone referred to as?
TIC
Fill in the blank: _______ is important in the research of bioeffects.
Bioeffect research
What type of cavitation occurs at lower MI levels and involves oscillating gaseous nuclei?
Stable cavitation
What type of cavitation occurs at higher MI levels and is characterized by bursting bubbles?
Transient cavitation
What are the potential harmful bioeffects when the temperature rises from 37C by 2-4C for more than 50 hours?
Harmful bioeffects
What can a temperature of 41C+ during a testicular exam cause?
Infertility
True or False: Fetal tissues are more tolerant than adult tissue regarding temperature increases.
False
What type of cavitation is also called normal or inertial?
Transient
What occurs during transient cavitation that produces shock waves and very high temperatures?
Bursting bubbles
What does the FDA regulate as the SPTA limit in mW/cm²?
720 mW/cm²
What describes the interaction of sound waves with microscopic, stabilized gas bubbles in tissues?
Radiation force
What is the pressure threshold for transient cavitation compared to stable cavitation?
10% higher
What are the two techniques used to study bioeffects?
- Mechanistic Approach
- Empirical Approach
What is a key uncertainty in the mechanistic approach to bioeffect research?
Uncertainty about assumptions
What is a potential drawback of the empirical approach to bioeffects?
Species differences may alter results
What is the bioeffect research claim that should be viewed with caution?
Direct clinical significance without in vivo validation
What does MI stand for in the context of ultrasound?
Mechanical Index
The Mechanical Index is a calculated number related to the likelihood of harmful bioeffects from cavitation.
What are the two sound wave characteristics related to the Mechanical Index?
- Peak rarefaction pressure
- Frequency
What happens to cavitation and pressure when the Mechanical Index is higher?
- More cavitation
- More pressure
- Lower frequency
What happens to cavitation and pressure when the Mechanical Index is lower?
- Less cavitation
- Less pressure
- Higher frequency
Define epidemiology.
A branch of medicine associated with population studies and the prevalence of disease
It is empirical and often uses clinical surveys.
What is a significant use of ultrasound in pregnant women?
Routine scanning during normal pregnancies.
Why is it important to study ultrasound’s effects on fetuses?
Harmful effects, if present, have the potential to affect the fetus for life.
What fetal evaluations are commonly assessed in epidemiologic studies involving ultrasound?
- Fetal weight
- Abdomen circumference
- Head circumference
- Femur length
- Congenital abnormality
- APGAR scores
- Hearing
- Infection
True or False: Data indicates that ultrasound exposure is associated with adverse fetal outcomes.
False
Data indicates that ultrasound exposure is not associated with adverse fetal outcomes.
What are limitations of epidemiologic studies mentioned in the text?
- Studies are often retrograde
- Ambiguities may exist in the data
- Risk factors other than exposure to ultrasound may precipitate a bad outcome
Fill in the blank: Antegrade studies are always _______.
[better]
List some risk factors other than ultrasound exposure that may affect fetal outcomes.
- Environmental factors
- Poor nutrition
- Smoking
- Alcohol and drug abuse
What are the best types of epidemiologic studies?
Prospective and Randomized studies
These studies are preferred for obtaining meaningful information and accounting for risk factors.
What is an advantage of a prospective study?
A complete and accurate compilation of meaningful information is obtained
This helps in understanding patient outcomes more effectively.
What do randomized studies do?
Create 2 groups of patients
This allows for better control of risk factors affecting fetal outcomes.
What is a key conclusion regarding bioeffects from diagnostic ultrasound?
No confirmed harmful bioeffects have ever been reported
Future identification of bioeffects is possible, but not confirmed.
What is the balance between benefits and risks in diagnostic ultrasound?
The benefits to the patient outweigh the risks
This supports the prudent use of diagnostic ultrasound.
In what setting is it inappropriate to use diagnostic ultrasound?
Non-medical settings for entertainment
This use does not provide any medical benefit.
What should patients be informed about when participating in research studies?
How the research study differs from standard diagnostic procedures
This is important when there is no direct medical benefit.
What is the greatest risk associated with ultrasound equipment?
Electrical shock from a cracked transducer housing
Damaged transducers can also compromise image quality.
What does ALARA stand for in the context of ultrasound?
As Low As Reasonably Achievable
This principle aims to minimize patient exposure.
What does the term ‘prudent’ refer to in the context of ultrasound use?
Careful, judicious use
This emphasizes the need for valid medical justification.
What should be done regarding the duration of ultrasound studies?
Do not prolong studies
This is part of the ALARA principle to minimize exposure.
What is a common experience difference noted between diagnostic ultrasound and research?
Experience may differ due to longer research exams and greater exposure
This can affect the perceived safety and effectiveness of ultrasound procedures.
