Hussain Basheer
Quiz by , created more than 1 year ago

Medical Physics Quiz on Generators of high frequency electromagnetic waves. Frequency ranges used in physiotherapy. Inductive and capacitive methods. Determination of the power of electromagnetic wave sources. Safety technique - Medical Physics -MCQs, created by Hussain Basheer on 23/11/2018.

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Hussain Basheer
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Generators of high frequency electromagnetic waves. Frequency ranges used in physiotherapy. Inductive and capacitive methods. Determination of the power of electromagnetic wave sources. Safety technique - Medical Physics -MCQs

Question 1 of 20

1

Which of the following human organs and tissues have the least thermal conductivity?

Select one of the following:

  • Muscles

  • Brain

  • Skin and fat

Explanation

Question 2 of 20

1

Which of the following diagnostic/therapeutic methods cause deep tissue heating?

Select one of the following:

  • Thermography

  • High frequency electric current therapy

  • Deep x-ray therapy

Explanation

Question 3 of 20

1

Faradization is a method for:

Select one of the following:

  • Electro-stimulation with low frequency pulsed current

  • High frequency electromagnetic therapy

  • Interferential current therapy of deep-seated tissue

Explanation

Question 4 of 20

1

The most common frequency used in high-frequency electro-stimulation is:

Select one of the following:

  • 20 Hz

  • 20 kHz

  • 2 MHz

Explanation

Question 5 of 20

1

Modern electromyography methods rely on the following parameter (chose one):

Select one of the following:

  • Rheobase

  • Chronaxie

  • Accommodation coefficient

Explanation

Question 6 of 20

1

Thermography is a medical imaging method that:

Select one of the following:

  • Is harmless

  • Has high resolution

  • With diagnostic significance similar to MRI

Explanation

Question 7 of 20

1

Which of the following body fluids and tissues has the least electrical conductivity?

Select one of the following:

  • Blood

  • Bones

  • Bone marrow

Explanation

Question 8 of 20

1

Electric resistance (R) is inversely proportional to:

Select one of the following:

  • Electric conductance (G)

  • Frequency (f)

  • Period (T)

Explanation

Question 9 of 20

1

What is the main effect that causes heating in microwave diathermy, and also in the microwave oven (f = 2.45 GHz)?

Select one of the following:

  • Resonance: water molecules oscillate with the same frequency

  • Dielectric heating: electric dipoles of water are made to rotate

  • Refraction: bending of waves inside the substance

Explanation

Question 10 of 20

1

Electric potential difference is measured in units of volts (V) that represent the ratio of:

Select one of the following:

  • Charge per time, Q/t

  • Energy per charge, E/Q

  • Energy per distance, E/x

Explanation

Question 11 of 20

1

Which of following electric currents is the most dangerous for the human body?

Select one of the following:

  • High frequency AC

  • Low frequency AC

  • Pulsed current

Explanation

Question 12 of 20

1

Which of the following currents will cause stimulation in excitable tissue (nerves or muscles)?

Select one of the following:

  • Low frequency, pulsed, above threshold

  • Low frequency, alternating, below threshold

  • High frequency, alternating, above threshold

Explanation

Question 13 of 20

1

High-frequency generators produce electromagnetic waves with:

Select one of the following:

  • Aperiodic behavior

  • Constant amplitude

  • Gradually damping amplitude

Explanation

Question 14 of 20

1

Which of the following currents causes differential heating in tissues?

Select one of the following:

  • Pulsed current

  • High frequency current

  • DC current

Explanation

Question 15 of 20

1

Which of the following features are common forelectrosurgery and electrostimulation?

Select one of the following:

  • The frequency

  • The shape of the electrodes

  • The use of alternating current

Explanation

Question 16 of 20

1

Specific heat capacity is defined as:

Select one of the following:

  • The amount of heat needed to raise the temperature of 1 kg of substance by 1 degree Kelvin (or Celsius)

  • The heat released during the controlled burn of 1 kg of substance

  • The heat gain in a substance when Gibbs free energy increases by 1 joule

Explanation

Question 17 of 20

1

Electrosurgical procedures apply alternating current in the radio frequency (RF) range (100 kHz - 5 MHz) directly to the tissue. Why during electrosurgery there is no nerve and muscular stimulations?

Select one of the following:

  • High frequencies currents do not penetrate deep enough

  • Oscillations are much faster than membrane depolarization time

  • The power is below stimulation threshold

Explanation

Question 18 of 20

1

What is the heating mechanism of high frequency alternating current (2MHz)?

Select one of the following:

  • Brief polarization of tissue

  • Oscillations of ionized molecules, rotation of dipoles and associated collisions

  • Absorption of energy from the electromagnetic waves

Explanation

Question 19 of 20

1

When an inductor (L) and a capacitor (C) are connected in series, the resulting (L-C) electric circuit is called:

Select one of the following:

  • Operational amplifier (compares and amplifies signal)

  • Current rectifier (converts AC into DC)

  • Harmonic oscillator (used to emit radio waves)

Explanation

Question 20 of 20

1

The Earth surface is (reasonably) constant potential reference, and for that reason taken to be the :

Select one of the following:

  • Infinite potential

  • Negative potential

  • Zero potential

Explanation

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