Instrumentation & Calibration Flashcards
6 cards from real CLS practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Instrumentation & Calibration flashcards as text
Which parameter directly determines the irradiance (power density) at the tissue surface when using a laser handpiece?
Answer: Output power and spot size
Irradiance (W/cm²) = Power (W) ÷ Spot Area (cm²). For a given output power, decreasing the spot size dramatically increases irradiance because area decreases as the square of the radius. Both power and spot size must be measured accurately during calibration.
A technician uses test paper to verify the laser spot size. The ablated spot appears elongated rather than circular. What is the most likely cause?
Answer: The beam is astigmatic or the handpiece optics are misaligned
An elongated ablation spot indicates beam astigmatism (unequal divergence in two axes) or misalignment of internal handpiece optics. This produces uneven fluence delivery across the spot and requires optical realignment or component replacement.
What is the role of a wavelength meter (wavemeter) in laser instrumentation maintenance?
Answer: To precisely measure the output wavelength for quality assurance and conformance verification
A wavemeter uses interference principles (often a Fizeau or Michelson interferometer) to precisely measure laser wavelength. Regular wavelength verification confirms the laser is operating within its specified range, which is critical for predictable chromophore absorption and patient safety.
In a Q-switched laser, what does increasing the Q-switch delay time typically do to the output pulse?
Answer: Increases peak power and decreases pulse duration
Increasing the Q-switch delay allows more population inversion to build up in the gain medium before switching to high-Q. When the cavity opens, more stored energy is released in a shorter time, producing a higher peak power and shorter pulse duration—key for photomechanical effects in pigment removal.
Why is it important to verify the laser spot size at the exact working distance specified in the device manual during calibration?
Answer: Because fluence calculations depend on spot area, which changes with defocusing
Laser beams diverge beyond the focal point, increasing spot area and reducing fluence (J/cm²). Calibrating and operating at the specified working distance ensures the delivered fluence matches the calculated dose. Defocusing can dramatically reduce efficacy or, conversely, focusing too tightly can cause unintended injury.
Which document provides traceable calibration standards for laser measurement instruments used in medical device quality assurance?
Answer: NIST (National Institute of Standards and Technology) calibration certificates
NIST calibration certificates provide measurement traceability to national standards, ensuring that power meters and energy meters used in clinical laser calibration give accurate, reproducible readings. Traceable calibration is required for ISO-compliant quality management systems in medical device use.