Mdcb Certification |Actual Questions And Verified Answers|Brand New Update|Graded A+

MDCB CERTIFICATION MATH |ACTUAL QUESTIONS
AND VERIFIED ANSWERS|BRAND NEW 2026-2027
UPDATE|GRADED A+


Question 1

If the exposure rate constant is 0.87 Rcm2hr-1mCi-1 and the average patient transmission
factor

is 0.20, the exposure rate at 12.5 cm for a patient who has been injected with 20 mCi of
Tc99m

is:

(A) 18 mR/hr.

(B) 20 mR/hr.

(C) 22 mR/hr.

(D) 25 mR/hr.

CORRECT ANSWER

(C) 22 mR/hr.



0.87x20x0.2x(1/12.5)^2=0.022R or 22mR




Question 2

The exposure rate emitting from a brachytherapy safe is found to be 25 mR/hr at 1 m from
the

safe source. The minimum thickness of shielding necessary to reduce the exposure to an

adjacent office secretary to an acceptable level would be:

(A) 1 TVL.

(B) 2 TVL.

(C) 10 TVL.


1

, (D) 12 TVL.

CORRECT ANSWER

(B) 2 TVL.




Question 3

The mass attenuation coefficient for lead at 140 keV is 2.6 cm2/g and the density of lead is
11.3 g/cm3. What is the percentage transmission through a 0.5 mm thick lead apron for an
effective energy of 140 keV?

(A) 11.3%

(B) 23.0%

(C) 32.3%

(D) 43.7%

CORRECT ANSWER

(B) 23.0%

2.6/11.3=0.23




Question 4

The dose rate at a patient's mid-plane is found to be 250 cGy/min at 100 cm SAD. A
protocol for hemi-body irradiation stipulates that the dose rate must be no more than 100
cGy/min. At what minimum SAD must the patient be treated?

(A) 120 cm

(B) 145 cm

(C) 158 cm

(D) 182 cm

CORRECT ANSWER

(C) 158 cm



2