Radiation Safety and Biological Effects Overview

What is the primary effect of radiation on macromolecular solutions?

It produces many smaller molecules and decreases viscosity.

What is a major form of DNA damage caused by irradiation?

Main chain scission, which can affect one or both side rails of the DNA.

How is DNA damage often repaired after main chain scission?

It is often quickly repaired, but mis-repair can lead to point mutations.

What is a point mutation?

A change or loss of a triplet code due to a single nucleotide change, which may result from mis-repair with a similar but incorrect molecule.

What is the principle action of radiation on humans?

The principle action is indirect, primarily resulting from the radiolysis of water.

How does biological tissue sensitivity vary under different conditions?

Biological tissue is more sensitive under aerobic conditions.

What is the Oxygen Enhancement Ratio (OER)?

It is the ratio of the dose required to produce a certain biological effect under anoxic conditions to the dose required to produce the same effect under aerobic conditions.

What age group is at the highest risk for radiation sensitivity?

Younger patients, due to their more rapidly dividing cells and higher metabolic rates.

What does the Law of Bergonie & Tribondeau state regarding cell maturity and radiation resistance?

Greater maturity of cells (adulthood) increases resistance against radiation.

Which cells are most sensitive to radiation?

Spermatogonia are among the most radiosensitive cells in the body.

What are deterministic effects in radiation exposure?

Effects that are dose-dependent, characterized by a threshold dose, and severity is related to the dose.

What are nonstochastic effects in radiation exposure?

Effects that are dose-independent, where the severity of the effect is not related to the dose.

What is LD 50/30 in the context of acute radiation lethality?

The lethal dose to kill 50% of the population within 30 days.

What is the threshold dose for skin radiation effects?

About 200 rads, where skin shows nonlinear threshold effects.

What is the earliest sign of skin radiation damage?

Damage to the epidermal basal (stem) cells.

What is the clinical tolerance level of skin radiation exposure?

Takes about 1800 rads over 4 weeks to reach the clinical tolerance level.

What is the effect of fluoroscopy in radiation exposure?

Boost mode can give up to a 10-fold increase in radiation per unit time.

What is the effect of radiation on testes?

As little as 10 rads can cause a decrease in spermatozoa.

What are the effects of pre-puberty and post-puberty radiation on ovaries?

Both can cause germ cell death and ovarian atrophy, with as little as 10 rads being harmful.

What is cytogenic damage in the context of radiation?

Damage that disrupts molecular bonds and produces visible chromosomal damage, manifesting during the next cellular mitosis.

What are the two types of cytogenic damage?

Single hit and multi-hit damage, with single hit being linear non-threshold at very low radiation doses.

What is the significance of multi-hit aberrations in radiation damage?

They are considered the most significant latent human damage.

What is the slope of the linear dose-response relationship in radiation exposure?

It compares observed cases to expected cases.

What factors influence lens radiosensitivity in cataract formation?

Lens radiosensitivity is age-dependent, with older age resulting in a greater effect and longer latent period.

What are the acute and fractionated thresholds for cataract formation?

Acute threshold is about 2 Gy, and fractionated threshold can be as high as 10 Gy.

What has changed in radiologic occupations since 1965?

Radiologic occupations have become safer.

What is the mortality rate of radiologic occupations compared to the general population?

Mortality is the same as the general population.

What is the general consensus on radiation-induced carcinogenesis regarding dose response?

Mortality is generally linear below 4.0 Sv and typically follows a non-threshold dose response.

Is radiation considered an effective cancer-causing agent?

No, it is not highly effective.

From which type of epithelium do thyroid cancers arise due to radiation exposure?

Thyroid cancers arise almost exclusively from follicular epithelium.

Which type of cancer is most likely to develop first due to radiation exposure?

Radiation-induced leukemia.

Why is bone marrow significant in the context of radiation exposure?

Bone marrow is among the most radiosensitive tissues.

What is the latency period for radiation-induced leukemia?

4 to 7 years, with an increased risk for about 20 years after exposure.

How do solid tumors compare to leukemia in terms of commonality after radiation exposure?

Solid tumors are three times more common than leukemia.

What is the average latency period for solid tumors following radiation exposure?

Average latency is 20 years or more.

According to the BEIR committee report, how much does overall lifetime cancer risk increase for every 10 rad?

Overall lifetime cancer risk increases about 1% for every 10 rad.

How does radiosensitivity to cancer differ between females and males?

Females are about 30% more radiosensitive to cancer than males.

How does the radiosensitivity of newborns compare to that of a 25-year-old?

Newborns are 3 times more radiosensitive for cancer than a 25-year-old.

What does data from drosophila studies suggest about genetic mutations and radiation?

Genetic mutations follow linear non-threshold curves with no 'dose rate' effect.

What was found regarding the doubling dose for genetic mutations in Mega-mouse experiments?

The doubling dose for genetic mutation was found to be much higher.

What significant effect was observed in Mega-mouse experiments regarding dose rate?

There is a substantial dose rate effect due to the ability of mice to heal.

What are the pertinent conclusions from Mega-mouse experiments regarding mutations?

Most mutations are harmful, and any dose of radiation increases the risk of spontaneous mutations.

During which trimester is fetal development most sensitive to radiation effects?

The 1st trimester is the most sensitive.

What is the most sensitive trimester for fetal effects from radiation exposure?

The 1st trimester.

What are the risks associated with fetal exposure during the 1st trimester?

High risk of prenatal death, congenital deformities, and neonatal death.

What is the significance of the first two weeks of fetal exposure to radiation?

High doses (250 mGy) can lead to severe outcomes, while low doses increase the normal incidence of spontaneous abortion.

What is the period of major organogenesis in fetal development?

From the 2nd to the 10th week.

What can high radiation doses during the 2nd to 10th week result in?

Temporary growth retardation and potential congenital deformities.

What are the potential effects of radiation exposure after the 10th week of pregnancy?

Functional CNS disorders and mental retardation, with approximately a 4% chance of occurrence.

What is the increase in congenital abnormalities following a 100 mGy exposure?

There is a percentage increase in congenital abnormalities from the normal averages.

What are the fetal risks associated with radiation exposure below 50 mGy?

There are minimal or no significant effects.

What fetal risks are associated with radiation exposure between 50 to 100 mGy?

Potential effects during organogenesis.

What is the recommended principle for reducing radiation exposure?

Minimize time, maximize distance, and employ shielding.

How is exposure time calculated in radiation exposure?

Exposure time is calculated as exposure rate multiplied by time.

What percentage of beam entrance skin intensity does scatter radiation represent at 1.0 meter?

Scatter is generally about 1% of beam entrance skin intensity at 1.0 meter.

What is the primary source of scatter radiation?

The patient.

What factors affect scatter radiation?

Thickness of body part, field size, orientation of body part and tube.

How does body part thickness affect scatter radiation?

Thicker body parts have more scatter radiation.

What is the relationship between field size and scatter radiation?

Field size is proportional to the square of the irradiated voxel size.

What are beam restricting devices used for?

To control the field size and reduce scatter radiation.

What is the purpose of a variable aperture collimator?

To control the field size using lead shutters.

At what kVp must lead be added to walls for radiation protection?

Above 70 kVp.

What is the grid ratio in radiation exposure?

Grid ratio is defined as height (h) divided by distance (d); a greater height improves scatter radiation stoppage.

What is primary beam radiation?

The actual beam being directed at the target.

What is the Tenth-Value Layer (TVL)?

The amount of material needed to reduce radiation to 1/10 of its original intensity, effectively reducing radiation by 90%.

What is the maximum permissible dose (MPD) for radiation exposure?

The cumulative lifetime limit of exposure is calculated as 10 mSv multiplied by age. For example, a 20-year-old has a limit of 200 mSv.

What is the purpose of personnel monitoring in radiation safety?

To measure radiation exposure using devices like film badges, which provide permanent records of exposure.

What is the typical thickness of lead used in lead safety garments for primary and secondary beams?

Typical thickness is specified in millimeters, with specific values for primary and secondary beams.

What is the average dose for an extremity exam of the hand or foot?

The average dose is 0.1 mSv.

What should be done to protect patients during radiographic procedures?

Maximize kVp while minimizing mAs to reduce patient exposure.

Who should be monitored for radiation exposure?

Any person likely to receive a dose in excess of 10% of their occupational dose limit in one year.

What does a 0.5 mm lead apron do in terms of exposure reduction?

It reduces exposure by at least a factor of 10.

What is the quality factor (HT) measured in?

HT is measured in Rems.

What additional precautions should pregnant workers take regarding radiation exposure?

Pregnant workers may continue to work but should wear an extra badge at the abdomen beneath their apron and should not exceed the recommended dose limits.

What are thyroid shields and leaded goggles used for?

They are recommended when monthly collar badge readings exceed a certain threshold to protect sensitive areas from radiation.

What is the purpose of using film badges in personnel monitoring?

Film badges use film to measure radiation exposure, with darkening read by a densitometer.

What are the advantages of more sensitive personnel monitoring devices?

They provide more accurate results, although they may be more expensive and take longer to process.

What is the significance of lead glass in radiation shielding?

Lead glass is used because it meets legal requirements for radiation shielding.

What is the relationship between Tenth-Value Layer (TVL) and Half-Value Layer (HVL)?

1 TVL is equivalent to approximately 3.32 HVLs.

What is the recommended lead thickness for gonadal shields?

Gonadal shields should have specific lead thickness to ensure adequate protection.

What is the typical lead equivalent for lead glass shielding?

The lead equivalent for lead glass is specified in millimeters.

What is the purpose of a densitometer in radiation monitoring?

A densitometer is used to read the darkening of film in personnel monitoring badges.

What is the significance of areas routinely occupied by radiation workers?

These areas require specific shielding and monitoring to ensure safety from radiation exposure.

What is the impact of using a lead apron on radiation exposure?

A lead apron significantly reduces the amount of radiation exposure to the wearer.

What is the ALARA principle in radiation safety?

ALARA stands for As Low As Reasonably Achievable.

How does distance from the fluoroscopy table affect radiation exposure?

Getting 1 foot away from the table decreases the dose.

Where should an operator stand to minimize exposure to scatter radiation during fluoroscopy?

The operator should stand away from the table, as most scatter radiation is emitted from the patient.

What is the effect of orientation of the image intensifier on radiation exposure?

The orientation can change the location of scatter radiation.

What are the two outcomes of radiolysis of water?

The two outcomes are the production of free radicals and the formation of hydrogen and hydroxyl ions.

How does biological tissue sensitivity to radiation vary with oxygen levels?

Biological tissue is more sensitive under aerobic conditions.

What is the relationship between cell maturity and radiation resistance?

Greater maturity of a cell increases resistance to radiation.

How does the age of tissue or organs affect radiosensitivity?

Decreased age of tissue/organs increases radiosensitivity.

What effect does increased metabolic activity have on radiosensitivity?

Increased metabolic activity increases radiosensitivity.

What is the impact of increased cell proliferation rate on radiosensitivity?

Increased cell proliferation rate increases radiosensitivity.

Which tissue type is most sensitive to radiation?

Lymphoid tissue is the most sensitive to radiation.

Which tissue type is least sensitive to radiation?

Mature connective tissue is the least sensitive to radiation.

What type of radiation-induced DNA damage is quickly repaired but may result in misrepair?

This type of damage is described as single-strand breaks.

What type of radiation-induced DNA damage is generally considered irreparable?

Double-strand breaks are generally considered irreparable.

What is the oxygen effect in radiation therapy?

The oxygen effect refers to the increased effectiveness of radiation in the presence of oxygen, dependent on linear energy transfer.

What happens to macromolecular solutions when irradiated?

They produce many smaller molecules and their viscosity decreases.