Radiation Oncology Radiobiology 2 - "LET"s Model

LETs learn

100

What LET stands for

What is linear energy transfer?

200

Gamma rays and are referred to high or low LET particles.

What is low LET?

300

While gamma rays release about 0.3 keV/micron, these particles release about 100 keV/micron.

What are alpha particles?

400

True or false: neutrons have lower LET than alpha-particles?

What is false? 

(Depends on the neutron energy)

500

The field of dosimetry related to effects at the cellular dimensions is known as this:

What is microdosimetry?

RBEquitous

100

RBE is needed because radiation dose, irrespective of beam quality, results in the same biological effects. True or false?

What is false?

200

What RBE stands for.

What is Relative Biological Effectiveness?

300

For a given particle, the RBE can depend on the dose and this property of the particle.

What is the energy?

400

The phenomena where RBE *de*creases as LET increases.

When is 'Overkill'?

500

The clinical RBE of protons when compared with photons.

What is about 1.1?

RT Radiobiology

100

TCP and NTCP stands for this.

What is tumor control probability and normal tissue complication probability?

200

T_pot is defined as the doubling of tumor cells and typically has this unit for time.

What are days?

300

The classical four 'R's of radiobiology.

What are repair of DNA damage, redistribution of cells in the cell cycle, repopulation, and reoxygenation of hypoxic tumor areas?

400

What the 'n' stands for in the BED equation.

What are the total number of fractions, n?

500

alpha/beta

value (estimate) for an early reaction of skin.

What is 9-12 Gy?

BEDder believe it

100

The EQD2 is a simple way of expressing a biological response relative to what dose per fraction?

What is 2 Gy fractions?

200

The approximate minimum time needed for sublethal repair after delivering a fraction.

What is approximately 6 hours? (or about a day for the spinal cord?)

300

The Lea-Catcheside factor 'g' is used to accommodate for the dose per fraction effect if sublethal recovery is not complete. True or false?

What is true?

400

For most tumor types and for early endpoints, the biological effect of a specific dose-fractionation will (increase/decrease) if overall treatment time is increased.

What is 'decrease'?

(biological effect decreases if overall treatment time is increased)

500

Errors in total dose delivery can be 'corrected' for by using Joiners' formula of 

D= P - E & d = Pp - Ee / (P - E). 

What does P and p stand for?

P is the total planned dose, and p is the planned dose per fraction.

Fractions and fictions

100

Hyperfractionation is defined as what?

What is delivering 2 or more radiation fractions per day?

200

Hyperfraction is often used to deliver a higher biological effect and thus the total dose is typically higher?/lower? than a conventional 2 Gy / fraction regimen. 

What is higher? 

Ex: EORTC 22971 compares 80.5Gy in 70 fx vs. 70Gy in 35 fx

300

This fictional dinosaur was awakened from the depths of the Pacific ocean from a nuclear detonation.

What is Godzilla?

400

The hype of hypofractionation greatly facilitated due to these technologies that significantly reduce the risk of toxicities.

What are image guidance and intensity modulation?

500

Walter White (Breaking Bad) was treated for this type of cancer.

What is lung cancer?