Radiography: Radiobiology & Radiation Safety Ch 13

The guiding philosophy of radiation protection is to keep radiation exposure as low as reasonably achievable (ALARA). This means that the goal is to minimize radiation doses to individuals and the general public while still allowing for the benefits of radiation use. It recognizes that it may not be possible to completely eliminate radiation exposure, but efforts should be made to reduce it to the lowest level that is reasonably achievable. This principle is important in various industries and fields where radiation is used, such as healthcare, nuclear power, and industrial settings.

One Gray (Gy) is equivalent to 100 rads.

Embryonic tissue is the most radiosensitive type of cell according to the Laws of Bergonie and Tribondeau. These laws state that cells that are rapidly dividing, undifferentiated, and have a long lifespan are more susceptible to radiation damage. Embryonic tissue fits all of these criteria as it undergoes rapid cell division and differentiation during development, and has a longer lifespan compared to other types of cells. Therefore, it is more prone to radiation damage compared to brain cells, cells of the gastric mucosa, and skin cells.

Erythema refers to the reddening of the skin caused by a high-radiation dose. This occurs when the skin is exposed to a significant amount of radiation, resulting in inflammation and dilation of blood vessels. The increased blood flow to the affected area causes the skin to appear red. It is important to note that erythema is specifically associated with a high dose of radiation, rather than a long-term, low dose.

The pelvis radiographic examination gives the fetus the highest "fetal dose" because it involves exposing the pelvic area, which is closer to the uterus where the fetus is located. This means that the radiation has a shorter distance to travel and has a higher chance of affecting the fetus. In contrast, the chest, cervical spine, and lumbar spine radiographic examinations are farther away from the uterus and therefore result in a lower fetal dose.

Using high kVp techniques will decrease patient dose because high kVp allows for better penetration of the X-rays through the patient's body, reducing the amount of radiation required to produce an image. This means that a lower dose of radiation is needed to achieve the desired image quality, resulting in a decrease in patient dose.

The conventional (British system) radiation unit to express radiation intensity in air is the Roentgen. This unit measures the ionization produced by X-rays or gamma rays in a specified volume of air. It is commonly used in the field of radiation protection and is defined as the amount of radiation that produces one electrostatic unit of charge in one cubic centimeter of dry air at standard temperature and pressure.

An indirect hit refers to a situation where an external force or agent causes damage to a biological system without directly interacting with it. In this context, free radicals are the most likely result of an indirect hit. Free radicals are highly reactive molecules that can cause damage to cells and biomolecules, including DNA. They are formed when molecules in the body undergo oxidation processes due to exposure to environmental factors such as radiation or toxins. Therefore, in the case of an indirect hit, the formation of free radicals is a plausible consequence.

Free radicals are temporary molecules or parts of molecules that form when radiation interacts with water. These molecules are toxic to human tissue. They are highly reactive and can cause damage to cells and DNA. Free radicals are known to be involved in various diseases and aging processes.

A direct hit refers to the breakage of a DNA molecule as a result of an interaction with an x-ray photon. When an x-ray photon directly interacts with a DNA molecule, it can cause damage to the molecular structure, leading to the breakage of the DNA molecule. This can have significant consequences for cell function and can potentially lead to genetic mutations or cell death.

Exposure to high levels of radiation can cause severe damage to the body's cells and tissues. The unit of measurement for radiation dose is rem (or Sv). In this question, the correct answer is 600 rem (6.0 Sv), which indicates that a whole-body exposure to this level of radiation can result in death. This level of radiation is extremely high and can cause extensive damage to the body's organs and systems, leading to fatal consequences.

The "weighting factor" is a number assigned to each type of radiation based on the variation in biologic damage that is produced when an individual receives exposure from different types of radiation. This factor takes into account the different levels of harm caused by different types of radiation and helps in calculating the equivalent dose (EqD) which expresses the overall biological effect of radiation on human tissue.

Exposure to radiation during pregnancy can increase the risk of birth defects. The greatest risk of birth defects occurs when the exposure exceeds a certain amount (r rad). Additionally, the timing of the exposure is also important. The first trimester of pregnancy is considered to be the most critical period for fetal development, so exposure during this time poses the highest risk of birth defects. Therefore, the correct answer is 1 and 2 only, as it states that the risk is highest when the exposure to the uterus exceeds r rad and occurs within the first trimester of pregnancy.

The correct answer is mrem. In the United States, the unit commonly used to report occupational dose to radiation workers is millirem (mrem). This unit measures the effective dose of radiation received by the workers, taking into account the type of radiation and the sensitivity of different body tissues to radiation. It is important to monitor and report occupational doses to ensure the safety of radiation workers and to comply with regulatory standards.

The correct answer reflects the current scientific opinion that there is an increased risk of cancer, leukemia, birth defects, and cataracts due to diagnostic levels of ionizing radiation.

Nerve cells would not be as vulnerable to x-rays compared to the other options. This is because nerve cells are specialized cells that have a unique structure and function, including a protective covering called the myelin sheath. The myelin sheath acts as insulation for the nerve cells, providing them with additional protection against external factors such as x-rays. In contrast, thyroid cells, skin cells, and blood cells do not have the same level of protection and are therefore more vulnerable to the damaging effects of x-rays.

The correct answer is "rad." The rad (radiation absorbed dose) is the conventional unit used in the British system to measure patient dose from radiation. It represents the amount of radiation energy absorbed by a specific material, such as human tissue. The rad is commonly used in the field of radiology to quantify the dose received by patients during medical procedures involving radiation, such as X-rays or CT scans. Other units, such as the roentgen, rem, and sievert, are also used to measure radiation, but they are not specific to the British system.

The unit of the SI system used to measure the ionization of dry air by an x-ray beam is C/kg (Coulombs per kilogram). This unit is used to quantify the amount of electric charge generated per unit mass of air when exposed to an x-ray beam. The ionization of air occurs when the x-ray photons transfer energy to the air molecules, causing them to become ionized. The C/kg unit allows for a standardized measurement of the ionization process, providing a consistent and reliable way to quantify the effects of x-ray exposure on dry air.

The conventional (British System) radiation unit of absorbed dose is the Rad. The Rad is a unit used to measure the amount of energy absorbed by a material when exposed to radiation. It is commonly used in the field of radiation protection and is equal to 0.01 joules of energy absorbed per kilogram of material.

In radiography, patient dose is usually calculated at the skin. This is because the skin is the outermost layer of the body and is the first point of contact with the radiation beam. Measuring the dose at the skin provides an indication of the radiation exposure that the patient receives during the procedure. It is important to monitor the dose at the skin to ensure that it is within safe limits and to minimize the risk of radiation-related side effects or injuries.

The KUB (Kidneys, Ureters, and Bladder) radiographic examination typically delivers the greatest gonadal exposure. This is because the KUB exam involves imaging the pelvic region, which is closer to the gonads compared to the other options (chest, lumbar spine, and femur). Therefore, the radiation dose received by the gonads is generally higher during a KUB examination.

Breast cancer is a stochastic radiation effect because it is a type of cancer that can occur randomly and without a clear threshold dose. Stochastic effects are those that have a probability of occurring, and their severity does not depend on the dose of radiation received. In the case of breast cancer, exposure to radiation increases the likelihood of developing the disease, but the severity or likelihood of occurrence is not directly linked to the dose received.

Low-dose techniques in radiography aim to reduce the amount of radiation exposure to the patient. Increasing kVp (kilovoltage peak) allows for better penetration of the x-rays, reducing the need for higher mAs (milliamperage seconds) and therefore reducing the radiation dose. Using a minimum source-image distance of 40 inches helps to reduce the patient's exposure to scattered radiation. Using slow intensifying screens also helps to reduce the radiation dose by allowing for longer exposure times and therefore lower mAs settings. Therefore, options 1 and 3 are considered low-dose techniques.

Stochastic effects are typical of the risk to a patient undergoing a diagnostic x-ray examination. Stochastic effects are random and occur without a threshold dose, meaning that any amount of radiation exposure can increase the probability of these effects occurring. These effects are usually long-term and include the development of cancer and genetic mutations.

Using faster screens and increasing the kVp using the 15% rule both decrease patient dose. Faster screens reduce the amount of radiation needed to produce an image, resulting in lower patient dose. Increasing the kVp using the 15% rule allows for a higher energy x-ray beam, which can penetrate the patient more easily and reduce the amount of radiation needed. Increasing the grid ratio to a 16:1 ratio, on the other hand, increases patient dose by requiring more radiation to penetrate the grid and reach the image receptor.

The EDE limit for whole-body dose of occupational radiation exposure for nonpregnant workers older than age 18 who are involved in radiation use is 5.0 rem per year. This means that these workers can be exposed to a maximum of 5.0 rem of radiation per year without exceeding the recommended limit. It is important for these workers to monitor and control their radiation exposure to ensure their safety and minimize any potential health risks associated with radiation exposure.

Exposure to radiation can lead to various changes in the body, and one of the earliest changes is seen in the blood. At a radiation dose of 25 rem (0.25 Sv), these blood changes become apparent. It is important to note that different radiation doses can have different effects on the body, and higher doses can lead to more severe consequences. However, at a dose of 25 rem, blood changes can already be observed.

The given answer, 1, 2, and 3, is correct because all three options listed are considered "low-dose techniques." Using optimum kVp means using the highest possible kilovoltage peak, which reduces the amount of radiation needed to produce an image. Using fast screens and fast film also reduces the exposure time and therefore the radiation dose. Finally, using a minimum source-image distance (SID) of 40 inches helps to reduce the radiation dose by increasing the distance between the patient and the x-ray source. Therefore, all three options contribute to reducing the radiation dose and are considered low-dose techniques.

The reduction of a limited operator's exposure to ionizing radiation can be accomplished by decreasing the time in the radiation field and increasing the distance from the radiation field. By spending less time in the radiation field, the operator reduces their overall exposure. Similarly, by increasing the distance from the radiation field, the operator decreases their exposure as the intensity of radiation decreases with distance. Using low kVp exposure techniques, however, does not directly reduce the operator's exposure to ionizing radiation.

Nonstochastic radiation effects are deterministic effects that occur when an individual is exposed to a high dose of radiation. These effects have a threshold dose below which they do not occur. In this case, all three options (sauzyres followed by coma, erythema, and radiation sickness) are examples of nonstochastic radiation effects.

High radiation doses can cause both nonstochastic effects and short-term somatic effects. Nonstochastic effects occur when the severity of the effect increases with the dose, such as radiation burns or radiation sickness. Short-term somatic effects refer to the immediate health effects that occur shortly after exposure, such as nausea, vomiting, and hair loss. Stochastic effects, on the other hand, occur randomly and do not have a threshold dose, meaning they can occur even at low doses. Examples of stochastic effects include cancer and genetic mutations. Since the correct answer states that only options 2 and 3 occur with high radiation doses, it means that stochastic effects (option 1) do not occur at high doses.