rt 204 prelims

Ionizing radiation

carries more energy and can remove electrons from atoms, potentially causing damage

x-rays, gamma rays

examples of ionizing radiation

Non-ionizing radiation

does not have enough energy to ionize atoms

visible light, radio waves

examples of non-ionizing radiation

Alpha particles

2 protons, 2 neutrons; are heavy and highly ionizing

Beta particles

are lighter and can penetrate more but are still ionizing

Gamma rays and X-rays

are both high-energy electromagnetic radiation but differ in their origin

electron shells

origin of x-rays

nucleus

origin of gamma rays

Direct effects

occur when radiation directly damages biological molecules like DNA

Indirect effects

involve the formation of free radicals through radiation interaction with water

Deterministic effects

have a threshold dose and result from high doses (e.g. radiation therapy, cataracts)

Stochastic effects

have no threshold and are more likely with lower doses over time (e.g. cancer)

S Phase

DNA replication

M Phase

Mitosis, where chromosomes separate

Meiosis

Reduces chromosome number by half, crucial for reproductive cells

Double-strand DNA breaks

more likely to cause severe genetic consequences like mutations or cell death.

Gray (Gy)

Absorbed dose

Sievert (Sv)

Equivalent dose, accounting for radiation type and biological effects

Becquerel (Bq)

Measures radioactive decay

Higher doses

in dose effects, this lead to deterministic effects

radiation burns

example of deterministic effects

lower doses

in dose effects, this lead to stochastic effects

cancer risk

example of stochastic effects

Occupational Exposure

Radiation exposure during work, such as in radiology departments

Medical Exposure

 Exposure due to medical imaging or treatment

Public Exposure

General population exposure from sources like cosmic radiation or environmental contamination

Internal Exposure

comes from inhaled or ingested substances

External Exposure

comes from radiation outside the body

lead apron

Protective measures like ________ help reduce exposure

distance

Increasing the __________ from a source decreases exposure.

CT and X-ray

High radiation dose compared to other modalities

MRI and Ultrasound

Non-ionizing, generally considered safer but may not provide the same diagnostic information

PET

Involves positron-emitting radionuclides, used for metabolic activity evaluation

Brachytherapy

A type of internal radiation therapy where a radioactive source is implanted near the tumor, maximizing dose to the cancer while minimizing exposure to healthy tissue.

ALARA Principle: As Low As Reasonably Achievable

the standard for minimizing exposure in medical environments

Dosimetry

Monitoring of radiation exposure using dosimeters to ensure safety in environments with ionizing radiation.