Rad Bio

Question 0

OER = -for x- & gamma rays -for neutrons -for alpha particles -calculation

Answer 0

2.5 1.6 1.0 Calc:

Question 1

RBE =

Answer 1

.

Question 2

For low LET radiations, 1 Gy = ? Ionizations For high LET, 1 Gy = ?? Ionizations

Answer 2

?= 1 ?? = 4

Question 3

The 4 Rs of Radiobiology

Answer 3

Repair Redistribution Repopulation Reoxygenation

Question 4

Which of the 4 Rs affect the tumor?

Answer 4

**All** Repair Repopulation Redistribution Reoxygenation

Question 5

Which of the 4 Rs affect early responding tissues (to radiation)?

Answer 5

Repair Repopulation Redistribution

Question 6

Which of the 4 Rs affect the late responding tissues?

Answer 6

Repair (only)

Question 7

What is the rationale for accelerated fractionation?

Answer 7

1. Dose is delivered prior to the onset of accelerated proliferation 2. Will cause more severe acute side effects, but patients should be off treatment before it is seen 3. Should not have any effect on late normal tissue complications

Question 8

Withers “hockey stick” graph

Answer 8

.

Question 9

The ‘Rs’ that are important in the dose rate effect

Answer 9

Repair Repopulation

Question 10

The ‘Rs’ that are important in the inverse dose rate effect

Answer 10

Repair Repopulation Redistribution

Question 11

Tpot :

Answer 11

The potential doubling time of tumor Calc: Tpot= (lambda) * (Ts / LI) Ts = time thru S phase LI = labeling index

Question 12

BED:

Answer 12

Biological equivalent dose Calc:

Question 13

Autophagy-related genes (Atgs)

Answer 13

* Regulate autophagy * required for the elongation of the lysosomal membrane * 2 ubiquitin-like conjugation systems: 1. Atg12 - Atg5 2. Atg8 - phosphatidylethanolamine (LC3-PE)

Question 14

Types of chromosomal aberrations:

Answer 14

Cell irradiated early in interphase 1. Dicentric (lethal) 2. Ring (lethal) 3. Small interstitial deletion (non-lethal) 4. Symmetric translocation (non-lethal)

Question 15

Types of chromatid aberrations:

Answer 15

1.

Question 16

PERK:

Answer 16

Protein kinase-like endoplasmic reticulum kinase (Add more in Ch26)

Question 17

Natural sources of radiation

Answer 17

1. Solar 2.

Question 18

DNA repair mechanisms

Answer 18

1. BER (base excision repair) 2. NER ( nucleotide excision repair) 3. HRR (homologous recombination repair) 4. NHEJ (non-homologous end-joining) 5. Cross-link repair (a combination of NER and recombinational repair pathways?) 6. MMR (mismatch repair)

Question 19

Mechanism of BER (base excision repair)

Answer 19

.

Question 20

Mechanism of NER ( nucleotide excision repair)

Answer 20

.

Question 21

Mechanism/gene protein products of HRR (homologous recombination repair/rejoining)

Answer 21

rad50, rad51, rad57

Question 22

Mechanism of NHEJ (non-homologous end-joining)

Answer 22

.

Question 23

MMR (mismatch repair) gene mutations with hereditary non-polyposis colon cancer

Answer 23

MLH1, PMS1, MSH2

Question 24

Growth fraction

Answer 24

Fraction of cells in a TUMOR that are actively cycling at a given time GF= (# proliferating cells) / (# proliferating cells + quiescent cells) Values in GF equation are only related to the tumor

Question 25

Cell loss factor (phi)

Answer 25

Disparity btwn Tpot and volume doubling time (Td) (Phi) = 1 - (Tpot / Td)

Question 26

Cell loss factor could be due to:

Answer 26

• exfoliation - necrosis - gaining access to vasculature - immune system - apoptosis

Question 27

Radiation syndromes

Answer 27

1. Cerebral vascular 2. Gastrointestinal 3. Hematopoietic

Question 28

Cerebrovascular syndrome

Answer 28

• TBI of ~100 Gy - death in 24-48 hrs - quick death - severe nausea & diarrhea w/in minutes - then disorientation, loss of coordination, respiratory distress, seizures,coma, death

Question 29

Gastrointestinal syndrome

Answer 29

TBI of >10 Gy - death 3-10 days later - nausea, diarrhea, vomiting - if diarrhea extends for days, it’s a negative prognostic indicator

Question 30

Hematopoietic syndrome

Answer 30

• 2.5 - 5 Gy - damage to the hematopoietic system - mature cells in circulation eventually die off (usually normal life span) - death usually in 30 - 60 days

Question 31

Population more sensitive to radiation exposure

Answer 31

Very young & very old > adult Male > female

Question 32

Typical LET values for: 1. 250-kVp x-rays 5. 14 MeV neutrons 2. Co-60 g rays. 6. Heavy charged particles 3. 3 MeV x-rays. 7. 1 keV electrons 4. 1 MeV electrons. 8. 10 keV electrons

Answer 32

(All in keV/um) * 2 * 12 * 0.2 * 100-200 * 0.3 * 12 * 0.25 * 2.3

Question 33

Radiation weighting factors (Wr) -photons - electrons/muons - protons/charged pions - alpha particles, fission fragments, heavy ions - neutrons

Answer 33

1 1 2 20 A continuous curve as a function of neutron energy

Question 34

Amount of radiation per ionizing event

Answer 34

34 eV

Question 35

Average energy loss per cluster

Answer 35

~110 eV

Question 36

Damage per 1 Gy of x-rays: DSB DNA crosslinks SSB base damages

Answer 36

40 DSB 150 DSB 1000 SSB 2500 base damages

Question 37

Where are the cell cycle checkpoints?

Answer 37

G1/S G2/M S

Question 38

Amifostine

Answer 38

*AKA WR-2721 *Radioprotector in radiotherapy *only radioprotector approved by FDA *Used in the prevention of xerostomia. *Given 30 minutes before radiation.

Question 40

Do : (D zero)

Answer 40

Dose of radiation that induces an average of one lethal event per cell, leaving 37% still viable

Question 41

Spur - what is it? - amount of energy? - number of ion pairs? - diameter?

Answer 41

• for x- or gamma rays, 95% of energy deposition events are these - contains up to 100 eV of energy - 3 ion pairs - 4 nm diameter

Question 42

Blob - what is it? - amount of energy? - number of ion pairs? - diameter?

Answer 42

• Much less frequent than blobs than spurs - 100 - 500 eV - 12 ion pairs - 7 nm - very frequent with alpha particles or neutrons

Question 43

Clustered lesion definition

Answer 43

• wide variety of complex lesions including base damage and DSB - previous term = locally multiply damaged site. - could be spread out over 20 base pairs