MEDICAL PHYSICS ABR PROFESSIONAL
MEDICAL PHYSICS PREP QUESTIONS AND
ACCURATE ANSWERS GRADED A+
●● Dose Delivered at Time
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)
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)
Answer: Gl = 1/(r^2 - (L^2/4))
●● Beta from TG-43
Answer: cos(Beta) = A.B/(|A||B|)
●● Area of Ellipse
,Answer: Ae = πab
●● Secular Equilibrium
Answer: Ap = Ad after 25 days
T1/2 of parent is 100-1000 times that of daughter
●● Transient Equilibrium
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
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
Answer: 1 cal/(g*K) or 4.184 J/(g*K)
●● Minimum Detectable Activity
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
Answer: StdNetCntRate =
SQRT((SQRT(Cnet)/tnet)^2+(SQRT(CBkd)/tBkd)^2)
●● Percent Error in Net Counts
Answer: %Error = StdNetCntRate/Netcpm
●● Person Sievert Equation
Answer: P-Sv = #PeopleD1*D1+#PeopleD2*D2+#PeopleD3*D3+...
●● Ev Per Ion Pair
Answer: 33.97 eV/IP or 33.97 J/C
●● Joule per eV
Answer: 1.6*10^(-19) J/eV
●● Roentgen
Answer: 2.58 * 10 ^ (-4) C/Kg
●● Atoms to Grams conversion
, Answer: Grams = Atoms * Aw(g/mol)/NA(atoms/mol)
●● Rad
Answer: 100 ergs/gram , 1cGy , absorbed dose
●● Joule Units
Answer: 1 Nm = kg*m^2/s^2
●● Newton Units
Answer: kg*m/s^2
●● Kinetic Energy of Ejected Electron
Answer: KE = h*nu-bindingenergy
●● Compton Scattered Photon Equation
Answer: E' = E0/(1+E0/0.511*(1-cos(thetaphoton))
●● Electron Angle Compton Scatter
Answer: Cos(Phielectron) = 1 +E0/.511*tan(thetaphoton/2)
●● Ultrasound Intensity
Answer: dB = 10*log(I/I0)
MEDICAL PHYSICS PREP QUESTIONS AND
ACCURATE ANSWERS GRADED A+
●● Dose Delivered at Time
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)
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)
Answer: Gl = 1/(r^2 - (L^2/4))
●● Beta from TG-43
Answer: cos(Beta) = A.B/(|A||B|)
●● Area of Ellipse
,Answer: Ae = πab
●● Secular Equilibrium
Answer: Ap = Ad after 25 days
T1/2 of parent is 100-1000 times that of daughter
●● Transient Equilibrium
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
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
Answer: 1 cal/(g*K) or 4.184 J/(g*K)
●● Minimum Detectable Activity
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
Answer: StdNetCntRate =
SQRT((SQRT(Cnet)/tnet)^2+(SQRT(CBkd)/tBkd)^2)
●● Percent Error in Net Counts
Answer: %Error = StdNetCntRate/Netcpm
●● Person Sievert Equation
Answer: P-Sv = #PeopleD1*D1+#PeopleD2*D2+#PeopleD3*D3+...
●● Ev Per Ion Pair
Answer: 33.97 eV/IP or 33.97 J/C
●● Joule per eV
Answer: 1.6*10^(-19) J/eV
●● Roentgen
Answer: 2.58 * 10 ^ (-4) C/Kg
●● Atoms to Grams conversion
, Answer: Grams = Atoms * Aw(g/mol)/NA(atoms/mol)
●● Rad
Answer: 100 ergs/gram , 1cGy , absorbed dose
●● Joule Units
Answer: 1 Nm = kg*m^2/s^2
●● Newton Units
Answer: kg*m/s^2
●● Kinetic Energy of Ejected Electron
Answer: KE = h*nu-bindingenergy
●● Compton Scattered Photon Equation
Answer: E' = E0/(1+E0/0.511*(1-cos(thetaphoton))
●● Electron Angle Compton Scatter
Answer: Cos(Phielectron) = 1 +E0/.511*tan(thetaphoton/2)
●● Ultrasound Intensity
Answer: dB = 10*log(I/I0)
