ABR Therapeutic Medical Physics Part 2
Questions With Complete Solutions
Virtual Source Distance Equation correct answer: (R100/R110) = ((VSD+Dmax+gap)/(VSD+Dmax))^2
Dose Delivered at Time correct answer: D(t) = D0(rate)/decay_constant*(1-e^(-dc(t))
D(t) = 1.44*D0(rate)*(1-e^(.693/T1/2*t))
TG-43 Geometry Function (Non-perpendicular) correct answer: Gl = Beta/(L*r*sin(theta))
Beta = angle between two ends of source to point
theta = angle between r and x axis
L = length of source
TG- 43 Geometry Function (Perpendicular) correct answer: Gl = 1/(r^2 - (L^2/4))
Beta from TG-43 correct answer: cos(Beta) = A.B/(|A||B|)
Area of Ellipse correct answer: Ae = πab
Secular Equilibrium correct answer: Ap = Ad after 25 days
T1/2 of parent is 100-1000 times that of daughter
Transient Equilibrium correct answer: • Transient equilibrium occurs when the half-life of the parent (T1) is not much longer than that of the daughter (T2) (e.g., decay of 99Mo to 99mTc). At transient equilibrium, the daughter activity A2 and the parent activity A1 are related by: A2 = A1 × T1/(T1 - T2).
No Equilibrium correct answer: daughter half-life longer than parent half-life
- activity of parent & daughter approx equal to activity of daughter (after approx 7 half-lives of daughter)
Specific Heat of Water correct answer: 1 cal/(g*K) or 4.184 J/(g*K)
Minimum Detectable Activity correct answer: MDA = 4.66*stdBkd+3/(Geometric_Eff*Intrinsic_Eff*timeBkd(s))
Also MDA = 3*SQRT(Rb/t) 99% conf interval
Standard Deviation of Net Count Rate correct answer: StdNetCntRate = SQRT((SQRT(Cnet)/tnet)^2+(SQRT(CBkd)/tBkd)^2)
Percent Error in Net Counts correct answer: %Error = StdNetCntRate/Netcpm
Person Sievert Equation correct answer: P-Sv = #PeopleD1*D1+#PeopleD2*D2+#PeopleD3*D3+...
Ev Per Ion Pair correct answer: 33.97 eV/IP or 33.97 J/C
Joule per eV correct answer: 1.6*10^(-19) J/eV
Roentgen correct answer: 2.58 * 10 ^ (-4) C/Kg Atoms to Grams conversion correct answer: Grams = Atoms * Aw(g/mol)/NA(atoms/mol)
Rad correct answer: 100 ergs/gram , 1cGy , absorbed dose
Joule Units correct answer: 1 Nm = kg*m^2/s^2
Newton Units correct answer: kg*m/s^2
Kinetic Energy of Ejected Electron correct answer: KE = h*nu-
bindingenergy
Compton Scattered Photon Equation correct answer: E' = E0/(1+E0/0.511*(1-cos(thetaphoton))
Electron Angle Compton Scatter correct answer: Cos(Phielectron) = 1 +E0/.511*tan(thetaphoton/2)
Ultrasound Intensity correct answer: dB = 10*log(I/I0)
attenuation linear with depth
HVL correct answer: HVL = ln(2)/Mu(linear attn. coef)
TVL correct answer: TVL = ln(10)/Mu(linear attn. coef)
Root Mean Square Voltage correct answer: Vrms = Vpeak/Sqrt(2)
Force on Particle in B Field correct answer: FM = qv x B = qvB
if 90Deg Power Reflected in Linac correct answer: Alpha = (z2-z1)/(z2+z1)
Minimum reflected when alpha = 0
Speed of Electron (Fraction of C) correct answer: Etotal = gamma*m0*c^2
Find Gamma
Gamma = 1/(Sqrt(1-B^2))
Solve for B
Waveguide Power Equation correct answer: P = V^2/(Z*L)
P = 5 mW
V = highest e- energy (20-22)
Z = Shunt Impedance (Mohms/m)
L = Accelerator Length (m) (1m)
Acoustic Impedance correct answer: Z = Rho*C
Z = pascal * seconds/meter or rayl
Rho = density
c = speed in medium
Signal Transmitted through boundary correct answer: T = 4*z1*z2/(z1+z2)^2
z1 & z2 acoustic impedance
Digestive Track Order (Start with Esophagus) correct answer: Esophagus, Stomach, Duodenum, Jejunum, Ileum, Cecum, Colon, Rectum
PDD Inherently Contains correct answer: Inverse Square Correction & Attenuation
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