Radiobiology and Cancer Terminology

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Questions and Answers

What characterizes high Linear Energy Transfer (LET) radiation compared to low LET radiation?

High LET radiation deposits energy uniformly across tissues.

High LET radiation has lower relative biological effectiveness (RBE).

High LET radiation causes less direct DNA damage than low LET radiation.

High LET radiation is more damaging due to denser ionization clusters. (correct)

Which factor is crucial in determining the biological effect of radiation on cells?

The temperature of the environment during exposure.

The type of radiation and its LET. (correct)

The duration of time between radiation fractions.

The total dose delivered at a single exposure.

Which statement about Relative Biological Effectiveness (RBE) is true?

RBE increases as the LET of the radiation increases. (correct)

RBE is constant regardless of dose and fractionation.

RBE decreases with lower doses of radiation.

RBE is only used for comparing different types of radiation therapy.

Which mechanism is employed to synchronize cell populations for radiation studies?

Employing Hydroxyurea to block cells from entering S phase. Signup and view all the answers

What is the significance of the oxygen effect in radiation therapy?

Cells are more sensitive to radiation when oxygen is present. Signup and view all the answers

What does the term 'Relative Biological Effectiveness' (RBE) refer to?

The ratio of doses required from different radiation types to achieve the same effect. Signup and view all the answers

Which statement best describes the difference between high LET and low LET radiation?

High LET radiation is more effective in causing direct DNA damage compared to low LET radiation. Signup and view all the answers

What is potentially lethal damage (PLD) in the context of radiation damage classification?

Damage that can be modified by post-irradiation environmental conditions. Signup and view all the answers

How does the dose rate effect impact cell survival after radiation exposure?

Increasing time between dose fractions can enhance cell survival. Signup and view all the answers

Which stage of the cell cycle does radiation primarily affect for DNA repair?

Late G2 phase allows for the highest chance of DNA repair. Signup and view all the answers

What role does reactive oxygen species (ROS) play in the effects of radiation?

ROS can amplify the damaging effects of radiation in cells. Signup and view all the answers

What is a key factor that increases the sensitivity of tumor cells to radiation?

High levels of oxygen in surrounding tissues Signup and view all the answers

Which of the following describes the process of reoxygenation after radiation treatment?

Hypoxic cells regain oxygen over time, improving radiosensitivity Signup and view all the answers

What is one of the four Rs of radiobiology that addresses the capacity of cells to recover from radiation damage?

Repair Signup and view all the answers

Which radiation type is likely to cause more significant biological damage per unit of dose?

Alpha particles Signup and view all the answers

What role does distribution play in radiation biology considering cell sensitivity?

Cells can be more radiosensitive at different times in the cell cycle Signup and view all the answers

What is typically a consequence of reoxygenation in tumor treatment post-radiation?

Potential inflammation and swelling Signup and view all the answers

In the context of radiation exposure in the environment, which of the following sources contributes to natural background radiation?

Cosmic rays from outer space Signup and view all the answers

Study Notes

Radiobiology

Radiobiology is the study of radiation on living things.

Terminology

DNA carries genetic information for development and function.
Tumors are abnormal cell growths (benign or malignant).
Cancer is a disease of abnormal cells that infiltrate and destroy normal tissue.

The Nature of Cancer

Carcinogenesis is the process of cancer formation, taking years.
Normal cells (10-20 microns) undergo genomic alterations, leading to uncontrolled replication and tumor formation (radiologically detectable at 2mm³).
Benign tumors stay localized and usually don't return after removal.
Malignant tumors are mobile (metastasize), show angiogenesis, and exhibit uncontrolled proliferation, with loss of growth suppressors.
Carcinoma (80-90%): a type of cancer affecting glands and organs (e.g., adenocarcinoma).
Squamous Cell Carcinoma: affects squamous epithelium.
Sarcoma: affects connective tissue.
Myeloma: affects plasma cells in bone marrow.
Leukemia: affects blood cells in bone marrow ("liquid/blood cancer").
Lymphoma: affects lymph cells.
Hodgkin's and Non-Hodgkin's are types of lymphoma.
Mixed types of cancer include combinations.

Epidemiology

Epidemiology is the study of the distribution and determinants of disease.
Incidence is the number of new cases in a population over a specific time.
Prevalence is the number of existing cases (previous and new) in a population.
Mortality is the death rate, often disease-related.

Etiology

Etiology is the study of causation.
Risk factors are variables linked to the likelihood of a specific endpoint (e.g., cancer).
- Intrinsic risks are those that cannot be changed, such as random errors during DNA replication or biological aging.
- Non-intrinsic risks are those that can be changed, such as exposure to radiation, chemical carcinogens, and infections (viruses).

Screening

Screening is a mechanism for detecting undiagnosed diseases.
Effective screening tests should have high sensitivity (detecting disease in those who have it) and specificity (correctly identifying those without disease).
Screening tests should be acceptable to the target population.
Screening strategies include breast, colorectal, lung, and prostate screenings, which may include non-invasive and invasive tests.

Radiation Physics

Radiation physics encompasses electromagnetic radiation (e.g., light, radio waves, X-rays) and particle radiation (fast-moving particles with energy and mass).
Ionizing radiation loses energy upon interaction with matter.
Interactions, such as photoelectric effect, Compton scattering, and pair production, can occur with inner or outer-shell electrons.
Stopping power is the average rate of energy loss of a charged particle per unit length.
Linear Energy Transfer (LET) is the energy transferred by radiation per unit length. Higher LET corresponds to more energy deposition in a smaller area.

Relative Biological Effectiveness (RBE)

RBE is a measure of the amount of radiation required to achieve a particular biological effect, expressed in Gray (Gy).
Equal doses of different radiation types do not have equivalent biological effects.
RBE is used to compare the effectiveness of different radiation types.

Radiation Chemistry

Radiolysis is the breakdown of a molecule, causing free radicals/ions to form via ionization.
Chemical interactions of radicals or ions with other molecules, and energy transfer can occur.
Water is a primary target for indirect effects, and these processes may lead to long-term biological consequences.

Cell Cycle

The cell cycle includes stages when DNA is replicated (S phase) and duplicated/separated (M).
Stages are G1, S, G2, and M to regulate cell growth.
Checkpoints control transitions between phases.

Chromosome damage

Chromosomes can be damaged by radiation.
This results in different types of chromosome abnormalities.

Cell Death

Apoptosis and necrosis are two types of cellular death.
Apoptosis is programmed cell death, involving controlled processes at the cellular level.
Necrosis is uncontrolled cell death, often due to injury or damage.

DNA Repair

Various mechanisms exist for DNA repair.
Base excision repair (BER) targets single-strand damage.
Nucleotide excision repair (NER) corrects larger distortions in DNA strands.
Homologous recombination repair (HR) repairs double-strand breaks using a homologous template.
Non-homologous end joining (NHEJ) joins broken ends directly, less accurate.
Mismatch repair (MMR) corrects base mismatches.

Survival curves

Survival curves show the relationship between the dose of radiation and the proportion of surviving cells.
The D0 value is the dose required to reduce survival by 37%.
D37: the dose required to reduce survival to a 63% level.

In-vitro assays/mouse tumour models

In-vivo studies are used to observe effects in living organisms.
In-vitro studies use lab techniques to investigate biological effects.
Mouse assays are common methods for modelling cancer and radiation damage in vivo/in-vitro conditions.

Other important concepts

Radiation induces chromosomal aberrations.
Risk of radiation comes from several factors (e.g., quality/type of radiation, amount).
Stochastic damage: no threshold of radiation dose for harmful effect.
Deterministic damage: a threshold dose above which tissue damage is observed.
OER = oxygen enhancement ratio: measures how much increased effect of radiation there is when oxygen levels are higher.
RBE = relative biological effectiveness: measures the amount of different types of radiation that can produce a certain effect.

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Description

Explore the fascinating world of radiobiology and its impact on living organisms. This quiz covers key concepts such as carcinogenesis, tumor characteristics, and different types of cancer, providing insight into the processes behind abnormal cell growth. Test your knowledge and understanding of these critical biological concepts.