Nuclear Medicine Instrumentation

Vocabulary flashcards for Nuclear Medicine Instrumentation lecture notes.

Gas Detectors

Basic gas detector with a voltage response curve including recombination, ionization, proportional, limited proportionality, Geiger Muller, and continuous discharge regions.

Ion Pairs

Occurs when radiation interacts with atoms and molecules, resulting in creating ion pairs. The number of electrons created is related to the amount of radiation present.

Anode

A positively charged central wire in a gas detector.

Cathode

A negatively charged metal tube in a gas detector.

Power Source (Gas Detectors)

Maintains the charge on the cathode and anode, with a meter to measure electricity flow during neutralization of charge.

Basic Operation (Gas Detectors)

The gas between the cathode and anode acts as an insulator until radiation ionizes the gas molecules, producing free electrons and positive ions.

Voltage Response Curve

The curve representing the applied voltage between the cathode and anode, divided into 6 regions.

Ionization Region

Also known as the saturation region; all electrons are collected, and the voltage is sufficient to reach the saturation point.

Geiger-Muller Region

Gas amplification is maximized; each radiation event produces an avalanche of ions, and the pulse size is the same for all radiation events; GM meters operate here.

Current Mode

Measures the number of electrons per second required to keep the anode and cathode charged, based on the time-average number of ionizations.

Pulse Mode

Electrons are treated as a group, with the pulse representing the total charge deposited by a single radiation interaction; dead time affects counting ability.

Ion Chambers/Exposure Rate meters

Gas filled device, used to measure exposure rate. Works in the ionization region in current mode.

GM Meters

Operates in the Geiger-Mueller region of the voltage response curve and in pulse mode, used as a qualitative indicator of radiation.

GM Meters-Quality Control Checks

Accuracy check performed annually; daily battery and voltage constancy checks.

Paralyzable

If an event occurs during dead time in the paralyzable design, it will be missed, and the dead time restarts and the instrument will reach saturation.

Non-Paralyzable

If an event occurs during dead time in the non-paralyzable design, it will be lost. The detector will reach saturation relative to the inverse of dead time.