MDCB Formulas + Memorization Exam
Questions With 100% Verified Answers
grenz rays (energy) -
correct answer ✅20 kV
contact therapy and endocavitary units (energy) -
correct answer ✅40-60 kV
superficial units (energy) -
correct answer ✅50-150 kV
orthovoltage therapy (energy) -
correct answer ✅150-500 kV
supervoltage therapy (energy) -
correct answer ✅300-1000 kV
blocked equivalent square -
correct answer ✅Blkd Eq Sq = (Eq Sq)·√(% unblkd field)
calculating beam flatness and beam symmetry -
correct answer ✅Beam Flatness (for uniformity) =
[D(off axis)-D(CAX)]÷[D(off axis)+D(CAX)]
,MDCB Formulas + Memorization Exam
Questions With 100% Verified Answers
Beam Symmetry (for tilt) =
[D(x1)-D(x2)]÷[D(x1)+D(x2)], where x1 and x2 are points off CAX at
same depth
wedge angle formula
hinge angle formula -
correct answer ✅Wedge Angle θ = 90 - φ/2
Hinge Angle φ = 180 - 2θ
**These do not account for surface irregularity
geometric penumbra formula -
correct answer ✅P = S(SSD+d-SCD)/SCD, where
S = source size
SSD = source to skin distance
d = depth
SCD = source to collimator/diaphragm distance
P↑ if S↑, SCD↓, SSD↑
P is independent of field size
,MDCB Formulas + Memorization Exam
Questions With 100% Verified Answers
gap calculation -
correct answer ✅G = S1 + S2
where
S1 = d(L1/2)÷SAD1 and S2 = d(L2/2)÷SAD2
or for like SAD's,
G = (d/SAD)·(L1+L2)/2
Co-60 dmax and PDD at 10 cm ref depth -
correct answer ✅0.5 cm, 56%
4 MV dmax and PDD at 10 cm ref depth -
correct answer ✅1.0 cm, 61%
6 MV dmax and PDD at 10 cm ref depth -
correct answer ✅1.5 cm, 67%
10 MV dmax and PDD at 10 cm ref depth -
correct answer ✅2.5 cm, 73%
15 MV dmax and PDD at 10 cm ref depth -
correct answer ✅3.0 cm, 77%
, MDCB Formulas + Memorization Exam
Questions With 100% Verified Answers
18 MV dmax and PDD at 10 cm ref depth -
correct answer ✅3.5 cm, 80%
25 MV dmax and PDD at 10 cm ref depth -
correct answer ✅4.0 cm, 83%
%/cm attenuation for Co-60 -
correct answer ✅4.0% per cm
%/cm attenuation for 6 MV -
correct answer ✅3.5% per cm
%/cm attenuation for 20 MV -
correct answer ✅2.0% per cm
air to tissue density ratio -
correct answer ✅air = 0.3 (tissue)
3.3 (air) = tissue
Questions With 100% Verified Answers
grenz rays (energy) -
correct answer ✅20 kV
contact therapy and endocavitary units (energy) -
correct answer ✅40-60 kV
superficial units (energy) -
correct answer ✅50-150 kV
orthovoltage therapy (energy) -
correct answer ✅150-500 kV
supervoltage therapy (energy) -
correct answer ✅300-1000 kV
blocked equivalent square -
correct answer ✅Blkd Eq Sq = (Eq Sq)·√(% unblkd field)
calculating beam flatness and beam symmetry -
correct answer ✅Beam Flatness (for uniformity) =
[D(off axis)-D(CAX)]÷[D(off axis)+D(CAX)]
,MDCB Formulas + Memorization Exam
Questions With 100% Verified Answers
Beam Symmetry (for tilt) =
[D(x1)-D(x2)]÷[D(x1)+D(x2)], where x1 and x2 are points off CAX at
same depth
wedge angle formula
hinge angle formula -
correct answer ✅Wedge Angle θ = 90 - φ/2
Hinge Angle φ = 180 - 2θ
**These do not account for surface irregularity
geometric penumbra formula -
correct answer ✅P = S(SSD+d-SCD)/SCD, where
S = source size
SSD = source to skin distance
d = depth
SCD = source to collimator/diaphragm distance
P↑ if S↑, SCD↓, SSD↑
P is independent of field size
,MDCB Formulas + Memorization Exam
Questions With 100% Verified Answers
gap calculation -
correct answer ✅G = S1 + S2
where
S1 = d(L1/2)÷SAD1 and S2 = d(L2/2)÷SAD2
or for like SAD's,
G = (d/SAD)·(L1+L2)/2
Co-60 dmax and PDD at 10 cm ref depth -
correct answer ✅0.5 cm, 56%
4 MV dmax and PDD at 10 cm ref depth -
correct answer ✅1.0 cm, 61%
6 MV dmax and PDD at 10 cm ref depth -
correct answer ✅1.5 cm, 67%
10 MV dmax and PDD at 10 cm ref depth -
correct answer ✅2.5 cm, 73%
15 MV dmax and PDD at 10 cm ref depth -
correct answer ✅3.0 cm, 77%
, MDCB Formulas + Memorization Exam
Questions With 100% Verified Answers
18 MV dmax and PDD at 10 cm ref depth -
correct answer ✅3.5 cm, 80%
25 MV dmax and PDD at 10 cm ref depth -
correct answer ✅4.0 cm, 83%
%/cm attenuation for Co-60 -
correct answer ✅4.0% per cm
%/cm attenuation for 6 MV -
correct answer ✅3.5% per cm
%/cm attenuation for 20 MV -
correct answer ✅2.0% per cm
air to tissue density ratio -
correct answer ✅air = 0.3 (tissue)
3.3 (air) = tissue
