Q/A

Question 1

Ionization chamber

Answer 1

Measure exposure by detecting liberated electron charge when x-ray photons ionize the gas within the chamber

C/kg or roentgens

1. Ionization chambers are dosimetry devices used to measure the output of x-ray tubes. Function as photo timers in automatic exposure controls and in nuclear medicine, as dose calibrators.
2. Pocket ionization chambers are a portable form of dosimetry device in the shape of large pens. Mechanical fragility.
3. Geiger counters have a high voltage across the chamber. Due to the high voltage and positive potential, liberated electrons are accelerated and gain energy, resulting in more liberated electrons from the chamber and amplification of liberated charge (electron avalanche). Therefore, they are HIGHLY SENSITIVE and are used to detect RADIOACTIVE CONTAMINATION (low level of radiation).

Question 2

Double mAs

Answer 2

• Increases square root the SNR (If 2X=square root of 2= 1.4)
• Increases linearly dose and head deposition in the anode disc (2X)

Question 3

Particle without mass

Answer 3

Photon:
No mass.
Does have momentum and wave like properties
Momentum of photon is determined by E(energy)/c(speed of light)

Question 4

What is the threshold for temporary hair loss?

Answer 4

2-5 Gy
> 5Gy: Clinically important hair and skin reactions
>10 Gy: Call dermathologist