MDCB CORE 2026 MAIN EXAMS QUESTIONS
AND ANSWERS SURE A+
✔✔What is an estimated hotpsot for the following beams:
Co-60
4x
10x
25x - ✔✔Co-60: 30%
4x: 20%
10x: 10%
25x: 5%
✔✔What is the difference between a dynamic wedge and a virtual wedge? -
✔✔Dynamic: jaw
Virtual: a physical wedge in the head of the machine
✔✔What is the difference between forward planning and inverse planning? -
✔✔Forward: select fields, manual weighting, FIF, most common in breast
Inverse: optimizer determines best fluence pattern, optimizer determines weighting of
fields, pre-defined dose distribution
✔✔What are advantages of forward planning over inverse planning? - ✔✔-Simpler
intensity patterns
-Easier to deliver
-Easier to verify
-Easier to calc MUs
✔✔What are advantages of inverse planning over forward planning? - ✔✔-Less dose to
critical structures
-Intensity patterns provide better distribution
,✔✔What are the steps done when performing IMRT commissioning? - ✔✔-Acceptance
test all equipment
-Beam data collection (small field dosimetry)
-TPS beam modeling
-Test algorithm
-MLC commissioning
-R&V testing
-Validate everything
✔✔What is considered the gold standard for absolute patient dosimetry? What other
options can be done? - ✔✔Gold standard: ion chamber
-Can also use film to evaluate relative dosimetry
-Can also use detector array (MapCheck)
✔✔When measuring absolute dosimetry for patient-specific QA, what is the preferred
agreement of the dose? What is the max deviation? - ✔✔preferred: +/-3%
max deviation: +/-5%
✔✔When measuring distance to agreement for patient-specific QA, what is the
preferred agreement of the dose and the points? - ✔✔Dose: 95% pass
Points: +/-3% or +/-3mm
✔✔Which has more dose heterogeneity(hotspots) within the target volume: 3D or
IMRT? - ✔✔IMRT
✔✔What report discusses contouring guidelines and target volumes? - ✔✔ICRU report
50 and 62
✔✔Tomotherapy is AKA___.
Tomo has a beam stop that is ___.
MLCs on a tomo unit are ___ thick and made of___.
What type of energy and what type of imaging is used? - ✔✔-helical IMRT
-2-3 TVLs
-10cm thick (very thick since beam is always on while table moves) made of tungsten
alloy
-6x beam and MVCT used
✔✔If a patient is less than 45 years old, what is the recommended dose constraint for
the contralateral breast? - ✔✔Below 200cGy
✔✔If a pregnant patient recieves the following dose, what is the risk to the fetus:
<5 rem
5-10 rem
10-50 rem
, >50 rem - ✔✔<5 rem: little risk
5-10 rem: risk uncertain
10-50 rem: significant risk during 1st trimester
>50 rem: high risk
✔✔What is the common rx for TBI?
Where is rx point?
What is dose rate? - ✔✔-8fx(200cGy)=1200cGy
-Prescribe to umbilicus
-Dose rate of 5-10cGy/min
✔✔What are the goals for the following parameters for a TBI plan?
-ISL
-OAR
-TPR - ✔✔-ISL: +/-6%
-OAR: +/-5%
-TPR: +/-4%
✔✔With TBI, if SSD increases what happens to surface dose? - ✔✔Increases
✔✔What is the typical rx for IORT e-? - ✔✔-single fx
-1000-2000cGy
-6Mev
✔✔What type of collimator should be used when doing IORT e- tx? - ✔✔-Aluminum
collimators and Lucite cones
-Low Z materials since low Bremms
✔✔Does inverse square apply with IORT e-? - ✔✔No
✔✔With IORT e-,
-Flatness is ___.
-Increase energy=___flatness
-Increase energy=___penumbra - ✔✔-Flatness is poor (15%)
-Increase energy=flatness worsens
-Increase energy= increased penumbra (penumbra will be on short side of colli)
✔✔What is the field arrangement for a TSI with e- tx? - ✔✔-6 field technique, Standford
technique, beams 60 degree apart
-Tx fields 1,2,3 on 1st day then tx field 4,5,6 on 2nd day
✔✔For TSI e- tx, what is:
-Tolerance for uniformity
-PDD
AND ANSWERS SURE A+
✔✔What is an estimated hotpsot for the following beams:
Co-60
4x
10x
25x - ✔✔Co-60: 30%
4x: 20%
10x: 10%
25x: 5%
✔✔What is the difference between a dynamic wedge and a virtual wedge? -
✔✔Dynamic: jaw
Virtual: a physical wedge in the head of the machine
✔✔What is the difference between forward planning and inverse planning? -
✔✔Forward: select fields, manual weighting, FIF, most common in breast
Inverse: optimizer determines best fluence pattern, optimizer determines weighting of
fields, pre-defined dose distribution
✔✔What are advantages of forward planning over inverse planning? - ✔✔-Simpler
intensity patterns
-Easier to deliver
-Easier to verify
-Easier to calc MUs
✔✔What are advantages of inverse planning over forward planning? - ✔✔-Less dose to
critical structures
-Intensity patterns provide better distribution
,✔✔What are the steps done when performing IMRT commissioning? - ✔✔-Acceptance
test all equipment
-Beam data collection (small field dosimetry)
-TPS beam modeling
-Test algorithm
-MLC commissioning
-R&V testing
-Validate everything
✔✔What is considered the gold standard for absolute patient dosimetry? What other
options can be done? - ✔✔Gold standard: ion chamber
-Can also use film to evaluate relative dosimetry
-Can also use detector array (MapCheck)
✔✔When measuring absolute dosimetry for patient-specific QA, what is the preferred
agreement of the dose? What is the max deviation? - ✔✔preferred: +/-3%
max deviation: +/-5%
✔✔When measuring distance to agreement for patient-specific QA, what is the
preferred agreement of the dose and the points? - ✔✔Dose: 95% pass
Points: +/-3% or +/-3mm
✔✔Which has more dose heterogeneity(hotspots) within the target volume: 3D or
IMRT? - ✔✔IMRT
✔✔What report discusses contouring guidelines and target volumes? - ✔✔ICRU report
50 and 62
✔✔Tomotherapy is AKA___.
Tomo has a beam stop that is ___.
MLCs on a tomo unit are ___ thick and made of___.
What type of energy and what type of imaging is used? - ✔✔-helical IMRT
-2-3 TVLs
-10cm thick (very thick since beam is always on while table moves) made of tungsten
alloy
-6x beam and MVCT used
✔✔If a patient is less than 45 years old, what is the recommended dose constraint for
the contralateral breast? - ✔✔Below 200cGy
✔✔If a pregnant patient recieves the following dose, what is the risk to the fetus:
<5 rem
5-10 rem
10-50 rem
, >50 rem - ✔✔<5 rem: little risk
5-10 rem: risk uncertain
10-50 rem: significant risk during 1st trimester
>50 rem: high risk
✔✔What is the common rx for TBI?
Where is rx point?
What is dose rate? - ✔✔-8fx(200cGy)=1200cGy
-Prescribe to umbilicus
-Dose rate of 5-10cGy/min
✔✔What are the goals for the following parameters for a TBI plan?
-ISL
-OAR
-TPR - ✔✔-ISL: +/-6%
-OAR: +/-5%
-TPR: +/-4%
✔✔With TBI, if SSD increases what happens to surface dose? - ✔✔Increases
✔✔What is the typical rx for IORT e-? - ✔✔-single fx
-1000-2000cGy
-6Mev
✔✔What type of collimator should be used when doing IORT e- tx? - ✔✔-Aluminum
collimators and Lucite cones
-Low Z materials since low Bremms
✔✔Does inverse square apply with IORT e-? - ✔✔No
✔✔With IORT e-,
-Flatness is ___.
-Increase energy=___flatness
-Increase energy=___penumbra - ✔✔-Flatness is poor (15%)
-Increase energy=flatness worsens
-Increase energy= increased penumbra (penumbra will be on short side of colli)
✔✔What is the field arrangement for a TSI with e- tx? - ✔✔-6 field technique, Standford
technique, beams 60 degree apart
-Tx fields 1,2,3 on 1st day then tx field 4,5,6 on 2nd day
✔✔For TSI e- tx, what is:
-Tolerance for uniformity
-PDD
