MDCB Math Exam Questions With
100% Verified Answers
The surface dose rate of a Strontium-90 (Sr-90) eye applicator was
4.5 cGy/second on May 15. If a patient is to be treated 2 years later
on May 15, what is the treatment time if 1000 cGy is prescribed?
(The half-life of Sr-90 is 28 years.) -
correct answer ✅234 secs
A=Ao(.5)^n n= t/t1/2
a=1000/4.5=222.2
222.2= x (.5)^2/28
222.2= x (.5)^.071
222.2=x.9519
222.2/.9519= 233.4
Iodine 125 has an exposure rate constant of 1.1 r/hr/mci and a half
life of 60.2 days. The milligram hour radium equivalency of a
permanent implant of a 1 mci iodine seed is therefore? -
correct answer ✅277
1.44x60.2x 24(hrs)x1.1/8.25)= 277
,MDCB Math Exam Questions With
100% Verified Answers
formula- find t mean= 1.44 x t1/2
ER radium= 8.25rcm3/hr mci
If the exposure rate constant is .87 Rcm2 Hr-1 mci-1 and the
average patient transmission factor is .20 the exposure rate at
12.5cm for a patient who has been injected with 20mci of tc99m is?
-
correct answer ✅22 mr formula = Er= Activity x exposure rate
constx 1/d^2
ER= 20mCi x .87 x 1/12.5^2 x .2
.02272 x1000=22.7
or 22r/hr
The exposure rate emitting from a brachytherapy safe is 25mR/hr at
1 m from the source. The minimum thickness of shielding necessary
to reduce the exposure to an adjacent secretary to an acceptable
level would be? How many TVL? -
correct answer ✅2 TVL
,MDCB Math Exam Questions With
100% Verified Answers
A simulation for an isocentric treatment on a linear accelerator SAD
is 100cm with a 12x15 fs. The tx is given on a co 60 unit SAD 80cm.
The fs to be used is>=? -
correct answer ✅12X 15 > 100 NORMINAL sad LINAC
80> NOMINAL SAD CO60
fs defined at nominal SAD
A simulation film is taken at 130 SFD for making blocks to be used
on a linac with an SAD of 100cm and a source to tray distance of
65cm. The tx is rescheduled to a linac with an SAD of 80cm and
source to try dx of 52cm. The block may be accurately produced is
the source to film distance is set to? -
correct answer ✅104cm
80/100 x 130
THe HVL for Co60 is 1.1 cm of lead. What thickness of lead would
reduce the transmitted dose to 2%? -
correct answer ✅6 HVL= 6x 1.1= 6.6cm
, MDCB Math Exam Questions With
100% Verified Answers
1 HVL= 50%
2 HVL= 25%
3 HVL= 12.5%
4HVL= 6.25%
5 HVL= 3.125%
6 HVL= 1.56%
in the triangle above the value of X (slant on triangle) is? Given
height is 4cm and angle is 30 degrees? -
correct answer ✅tang(30)= 4/y
.577y=4
4/.577= 6.9cm
Calculate the given dose of a 100cm SSD tx with a tumor dose of
60cgy prescribed to a depth of 11cm
PDD @1.5cm=100
PPD @ 5.5cm=81.1
PDD @ 11cm= 67.1
100% Verified Answers
The surface dose rate of a Strontium-90 (Sr-90) eye applicator was
4.5 cGy/second on May 15. If a patient is to be treated 2 years later
on May 15, what is the treatment time if 1000 cGy is prescribed?
(The half-life of Sr-90 is 28 years.) -
correct answer ✅234 secs
A=Ao(.5)^n n= t/t1/2
a=1000/4.5=222.2
222.2= x (.5)^2/28
222.2= x (.5)^.071
222.2=x.9519
222.2/.9519= 233.4
Iodine 125 has an exposure rate constant of 1.1 r/hr/mci and a half
life of 60.2 days. The milligram hour radium equivalency of a
permanent implant of a 1 mci iodine seed is therefore? -
correct answer ✅277
1.44x60.2x 24(hrs)x1.1/8.25)= 277
,MDCB Math Exam Questions With
100% Verified Answers
formula- find t mean= 1.44 x t1/2
ER radium= 8.25rcm3/hr mci
If the exposure rate constant is .87 Rcm2 Hr-1 mci-1 and the
average patient transmission factor is .20 the exposure rate at
12.5cm for a patient who has been injected with 20mci of tc99m is?
-
correct answer ✅22 mr formula = Er= Activity x exposure rate
constx 1/d^2
ER= 20mCi x .87 x 1/12.5^2 x .2
.02272 x1000=22.7
or 22r/hr
The exposure rate emitting from a brachytherapy safe is 25mR/hr at
1 m from the source. The minimum thickness of shielding necessary
to reduce the exposure to an adjacent secretary to an acceptable
level would be? How many TVL? -
correct answer ✅2 TVL
,MDCB Math Exam Questions With
100% Verified Answers
A simulation for an isocentric treatment on a linear accelerator SAD
is 100cm with a 12x15 fs. The tx is given on a co 60 unit SAD 80cm.
The fs to be used is>=? -
correct answer ✅12X 15 > 100 NORMINAL sad LINAC
80> NOMINAL SAD CO60
fs defined at nominal SAD
A simulation film is taken at 130 SFD for making blocks to be used
on a linac with an SAD of 100cm and a source to tray distance of
65cm. The tx is rescheduled to a linac with an SAD of 80cm and
source to try dx of 52cm. The block may be accurately produced is
the source to film distance is set to? -
correct answer ✅104cm
80/100 x 130
THe HVL for Co60 is 1.1 cm of lead. What thickness of lead would
reduce the transmitted dose to 2%? -
correct answer ✅6 HVL= 6x 1.1= 6.6cm
, MDCB Math Exam Questions With
100% Verified Answers
1 HVL= 50%
2 HVL= 25%
3 HVL= 12.5%
4HVL= 6.25%
5 HVL= 3.125%
6 HVL= 1.56%
in the triangle above the value of X (slant on triangle) is? Given
height is 4cm and angle is 30 degrees? -
correct answer ✅tang(30)= 4/y
.577y=4
4/.577= 6.9cm
Calculate the given dose of a 100cm SSD tx with a tumor dose of
60cgy prescribed to a depth of 11cm
PDD @1.5cm=100
PPD @ 5.5cm=81.1
PDD @ 11cm= 67.1
