Cavity Theory, Ion Chambers,, & Dose 1

Term for current collected in chamber in air spaces outside designated volume?

Extracameral ionization

Rank from largest to smallest (K_coll, KERMA, TERMA, K_rad)

TERMA, KERMA, K_coll, K_rad

Which cavity theory(s) accounts for delta rays?

Spencer-Attix and Burlin

formula for (K_coll)_air?

(K_coll)_air=X*(W_air/e)

Which cavity theory can be used to calculate dose in large cavity?

Burlin

Match Cavity theory correction factors P_fl, P_cel, etc..

know these

Work function for air value?

33.97 J/C… this is on the ABR constants sheet lol

T/F. Under conditions of TCPE, D=K_coll.

False. Proportional, not equal

T/F. Assuming K_rad=0, K=K_col?

True.. we usually assume radiative processes escape volume

TG-51 K_Q equation…

K_Q = (Ratio of L/ρ for water to air ∗P_fl∗P_gr∗P_wall∗P_cel∗P_ion)_Q divided by (Ratio of L/ρ for water to air ∗P_fl∗P_gr∗P_wall∗P_cel∗P_ion)_Co-60

Where on %DD curve is Beta < 1?

Buildup region

T/F. Purpose of cavity theory is to relate dose in air of ion chamber to dose in water?

True

Under which [beam type] conditions would you utilize D_med = φ(S/ρ)

Stopping power ratios used in ELECTRON beams

T/F. In MV beams, KERMA=TERMA?

False. TERMA includes energy losses that do not get transferred to medium (principally scattered compton photons)

What is difference between definition of KERMA and TERMA? (i.e. what s in one but not the other)

Scattered Compton Photons

Spencer Attix Cavity Theory equation?

D_med/D_gas= Ratio of RESTRICED Stopping powers

T/F. Units of KERMA and Dose can both be J/Kg.

True

Match TERMA, KERMA, K_coll, K_rad with most closesly related quantitiy (transfer coefficient, energy absorption coefficient, total coefficient, (1-g)(transfer coefficients)

TERMA - μ/ρ

KERMA - μ_tr/ρ

K_coll - μ_en/ρ

K_rad - (1-g)(μ_tr/ρ)

Given following conditions, which cavity theory?

Secondary e^- spectrum not perturbed by cavity presence, energy of secondary e^- is deposited where they are created inside chamber, delta rays ignored

Bragg-Gray