NPTE-PTA Therapeutic Modalities and Electrotherapy 1 — Questions and Answers
Question 1: Which parameter determines the frequency of ultrasound and affects depth of penetration?
- Intensity (W/cm²)
- Frequency (MHz) (Correct answer)
- Duty cycle (%)
- Treatment duration (minutes)
Correct answer: Frequency (MHz)
Ultrasound at 1 MHz penetrates deeper (up to 5 cm) and is used for deep tissues, while 3 MHz penetrates more superficially (1–2 cm) due to higher absorption.
Question 2: What does a 20% duty cycle in pulsed ultrasound indicate?
- Ultrasound is on 20% of the time and off 80% of the time (Correct answer)
- Ultrasound intensity is set to 20% of maximum
- The frequency is 20% of 1 MHz
- The treatment lasts 20 minutes
Correct answer: Ultrasound is on 20% of the time and off 80% of the time
Duty cycle is the ratio of on-time to total cycle time; a 20% duty cycle means the ultrasound is active for 20% of each pulse cycle, reducing thermal effects.
Question 3: Which electrical stimulation waveform is most commonly used for muscle strengthening in a normally innervated muscle?
- Russian current (medium-frequency AC) (Correct answer)
- Interferential current
- High-voltage pulsed current
- Direct current (galvanic)
Correct answer: Russian current (medium-frequency AC)
Russian current (2500 Hz sinusoidal AC delivered in 50 bursts/sec) is widely used for muscle strengthening because it produces strong, comfortable muscle contractions.
Question 4: What is the primary physiological effect of cryotherapy in the first 24–48 hours post-injury?
- Increased blood flow and collagen synthesis
- Vasoconstriction, reduced metabolism, and decreased edema formation (Correct answer)
- Increased nerve conduction velocity
- Increased tissue extensibility
Correct answer: Vasoconstriction, reduced metabolism, and decreased edema formation
Cryotherapy causes vasoconstriction, slows cellular metabolism, and reduces the release of inflammatory mediators, limiting secondary tissue damage in the acute phase.
Question 5: Iontophoresis uses which principle to drive medication through the skin?
- Ultrasonic cavitation
- Magnetic resonance
- Direct electrical current repelling similarly charged ions (Correct answer)
- High-frequency alternating current
Correct answer: Direct electrical current repelling similarly charged ions
Iontophoresis uses direct current to drive ionized medication through the skin; like charges repel, so a negatively charged drug is driven from the negative electrode into tissue.
Question 6: Which modality is contraindicated over a cardiac pacemaker?
- Cold pack application
- Moist heat pack
- Interferential current (IFC) (Correct answer)
- Manual stretching
Correct answer: Interferential current (IFC)
Electrical stimulation modalities including interferential current are contraindicated over or near cardiac pacemakers as they can interfere with pacemaker function.
NPTE-PTA Therapeutic Modalities and Electrotherapy 1
Which parameter determines the frequency of ultrasound and affects depth of penetration?