Bioeffects Flashcards by Roxanne Roden

What are bioeffects?

Effects of sound on living tissue created by intense sound beam

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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

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What does a calibrated hydrophone provide?

Known relationship between the acoustic pressure signal and the voltage created by the PZT

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What is the purpose of a membrane hydrophone?

Constructed from a very thin membrane of PZT plastic; detects intensity

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What is the highest output power in ultrasound?

Pulsed Doppler

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What is the lowest output power in ultrasound?

Gray scale imaging

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What is the intermediate output power in ultrasound?

CF Doppler and M-mode

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What is radiation force/feedback?

Force exerted on tissue by the sound beam; relates to power in the beam

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What are the three devices that measure output of transducer by absorption?

Calorimeter
Thermocouple
Liquid Crystal

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What is the function of a calorimeter?

Measures total power/entire intensity in a sound beam through absorption

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What does a thermocouple do?

A tiny electronic thermometer that can measure intensity at a particular location

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How do liquid crystals respond to temperature?

Change color based on their temperature

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What is the risk-benefit relationship in clinical ultrasound?

Benefits to the patient must outweigh the risks of the exam

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True or False: Diagnostic ultrasound has known harmful bioeffects.

False

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Under what circumstances can bioeffects be beneficial?

Under controlled circumstances

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What is the primary mandate regarding clinical ultrasound?

Benefits to the patient must outweigh the risks

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What is dosimetry?

The science of identifying and measuring the characteristics of an ultrasound beam relevant to its potential for producing biological effects

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What does ‘in vivo’ refer to?

Within the living body

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What are the main characteristics measured by a hydrophone?

Period
PRP
PRE
PD
Amplitude
DE

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What is the process of conversion of energy to heat called?

Thermal energy conversion

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What is JAcousto-Optics?

Based on the interaction of sound and light

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What is a Schlieren system used for?

A shadowing system that visualizes the shape of a sound beam in a medium

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What is the term for biological effects studied outside the living body?

In vitro

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What approach searches for a relationship between cause and effect in bioeffects research?

Mechanistic Approach

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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 ## Footnote 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 ## Footnote 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 ## Footnote 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 ## Footnote 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 ## Footnote This helps in understanding patient outcomes more effectively.

What do randomized studies do?

Create 2 groups of patients ## Footnote 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 ## Footnote 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 ## Footnote This supports the prudent use of diagnostic ultrasound.

In what setting is it inappropriate to use diagnostic ultrasound?

Non-medical settings for entertainment ## Footnote 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 ## Footnote 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 ## Footnote Damaged transducers can also compromise image quality.

What does ALARA stand for in the context of ultrasound?

As Low As Reasonably Achievable ## Footnote This principle aims to minimize patient exposure.

What does the term 'prudent' refer to in the context of ultrasound use?

Careful, judicious use ## Footnote This emphasizes the need for valid medical justification.

What should be done regarding the duration of ultrasound studies?

Do not prolong studies ## Footnote 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 ## Footnote This can affect the perceived safety and effectiveness of ultrasound procedures.