RAPHEX THERAPY SET QUESTIONS AND ANSWERS
SURE A+
✔✔flattening filters flatten the beam at a depth of - ✔✔10cm
✔✔what two factors are important in selecting a PDD table from literature for a
superficial x-ray unit? - ✔✔HVL and SSD
✔✔dose under a 1.5cm width block of 5 HVL thickness in a 15x15 6MV photon beam at
5 cm depth due to transmission plus scatter is approximately ____% of the dose in the
open beam - ✔✔15%
✔✔A patient treated with 6MV tangential breast fields, the dose to the ovaries 20cm
inferior to the fields is approximately ___% of the prescribed dose - ✔✔.5%
✔✔how far from the field edge does 5% occur for a 6MV beam? - ✔✔2cm
✔✔how quickly are electrons attenuated in lead? - ✔✔2MeV/mm
✔✔how much more cerrobend is needed than lead for electrons? (%) - ✔✔20%
✔✔what is the purpose of combining electrons and photons rather than just electrons
for a parotid treatment? - ✔✔lower the skin dose
✔✔equation for total dose in an LDR brachy treatment - ✔✔TD=initial dose rate * 1.44*
t1/2
✔✔Alpha decay - ✔✔2 protons, 2 neutrons- A-4, Z-2
✔✔beta minus - ✔✔neutron= proton + electron, A stays same, Z+1, produces neutrino
✔✔beta plus - ✔✔proton= neutron + positron, A stays same, Z-1, produces neutrino
SURE A+
✔✔flattening filters flatten the beam at a depth of - ✔✔10cm
✔✔what two factors are important in selecting a PDD table from literature for a
superficial x-ray unit? - ✔✔HVL and SSD
✔✔dose under a 1.5cm width block of 5 HVL thickness in a 15x15 6MV photon beam at
5 cm depth due to transmission plus scatter is approximately ____% of the dose in the
open beam - ✔✔15%
✔✔A patient treated with 6MV tangential breast fields, the dose to the ovaries 20cm
inferior to the fields is approximately ___% of the prescribed dose - ✔✔.5%
✔✔how far from the field edge does 5% occur for a 6MV beam? - ✔✔2cm
✔✔how quickly are electrons attenuated in lead? - ✔✔2MeV/mm
✔✔how much more cerrobend is needed than lead for electrons? (%) - ✔✔20%
✔✔what is the purpose of combining electrons and photons rather than just electrons
for a parotid treatment? - ✔✔lower the skin dose
✔✔equation for total dose in an LDR brachy treatment - ✔✔TD=initial dose rate * 1.44*
t1/2
✔✔Alpha decay - ✔✔2 protons, 2 neutrons- A-4, Z-2
✔✔beta minus - ✔✔neutron= proton + electron, A stays same, Z+1, produces neutrino
✔✔beta plus - ✔✔proton= neutron + positron, A stays same, Z-1, produces neutrino
