Radiation Dosimetry questions with verified answers
Define Excitation Ans✓✓✓ The energy given to an orbital electron is
insufficient to eject it from an atom, so just simply raises it to the higher
energy level.
Define how electronic equilibrium can exist Ans✓✓✓ If the number of
electrons entering a space = the number of electrons leaving and of
similar energies.
Define Ionisation Ans✓✓✓ The process by which a neutral atom
acquires a positive or negative charge.
What are diodes used for, and what are they made of? Ans✓✓✓ used
for invivo and relative dosimetry
silicon crystal of 2 layers
one has an excess positive charge and the other has an excess negative
charge (P type and N type)
This creates 3rd region known as Depletion Layer
Accurate for measuring precise dose fall off
What are the advantages of diodes? Ans✓✓✓ Advantages
High sensitivity
Fast response
Small size - good spatial resolution
, No external bias (voltage)
robust
no pressure corrections needed
What are the advantages of MOSFET? Ans✓✓✓ Direct reading
sensitive
small
waterproof
wireless
What are the differences in the diodes depending on particle?
Ans✓✓✓ Photons - thick build up cap, as tissue equivalent to energy
eg. 6MV so 1.5cm
Electrons - very thin build up cap for protection
What are the disadvantages of diodes? Ans✓✓✓ Disadvantages
temperature dependence
has energy, doserate and angular dependence
needs electric wire to connect
accumulated dose - response changes over time, so must account for
this.
What are the disadvantages of MOSFET? Ans✓✓✓ Regular QA needed
Define Excitation Ans✓✓✓ The energy given to an orbital electron is
insufficient to eject it from an atom, so just simply raises it to the higher
energy level.
Define how electronic equilibrium can exist Ans✓✓✓ If the number of
electrons entering a space = the number of electrons leaving and of
similar energies.
Define Ionisation Ans✓✓✓ The process by which a neutral atom
acquires a positive or negative charge.
What are diodes used for, and what are they made of? Ans✓✓✓ used
for invivo and relative dosimetry
silicon crystal of 2 layers
one has an excess positive charge and the other has an excess negative
charge (P type and N type)
This creates 3rd region known as Depletion Layer
Accurate for measuring precise dose fall off
What are the advantages of diodes? Ans✓✓✓ Advantages
High sensitivity
Fast response
Small size - good spatial resolution
, No external bias (voltage)
robust
no pressure corrections needed
What are the advantages of MOSFET? Ans✓✓✓ Direct reading
sensitive
small
waterproof
wireless
What are the differences in the diodes depending on particle?
Ans✓✓✓ Photons - thick build up cap, as tissue equivalent to energy
eg. 6MV so 1.5cm
Electrons - very thin build up cap for protection
What are the disadvantages of diodes? Ans✓✓✓ Disadvantages
temperature dependence
has energy, doserate and angular dependence
needs electric wire to connect
accumulated dose - response changes over time, so must account for
this.
What are the disadvantages of MOSFET? Ans✓✓✓ Regular QA needed
