rad exam 3 extra

LD 50/30

refers to the radiation dose expected to cause death in 50% of an exposed population within 30 days; it is used to estimate radiation lethality

High kVp techniques

produce more scatter radiation, which results in lower radiographic contrast and more shades of gray on the image

The prodromal stage

is the first phase of acute radiation syndrome and includes symptoms like nausea and vomiting shortly after exposure

Collimation

is the most effective and commonly used method of beam restriction and significantly reduces patient dose and scatter radiation

Increasing SID

decreases beam intensity at the image receptor, so mAs must be increased to maintain proper exposure

Atrophy

is the shrinkage or reduction in size of tissues or organs following high radiation doses due to cell loss

Scatter radiation

degrades image quality by reducing contrast, so minimizing scatter improves diagnostic visibility

The hematopoietic syndrome

affects bone marrow and blood cell production and occurs at lower doses than gastrointestinal or cerebrovascular syndromes

A compensating filter

evens out exposure across structures of different thicknesses and requires an increase in technique to maintain receptor exposure

Radium behaves like calcium

in the body, which is why it accumulates in bone tissue and can cause long-term damage

Inverse square law

states that radiation intensity decreases with the square of the distance, meaning small distance changes greatly impact exposure

Low kVp techniques

produce higher contrast images with more black-and-white differences, often used for extremities

Genetic radiation effects

occur when DNA in reproductive cells (sperm or ova) is damaged and passed to future generations

The latent period

is a temporary phase where no symptoms are present, even though cellular damage has already occurred

Opening collimation (larger field size)

increases scatter production and reduces image contrast

Digital radiography (DR)

provides immediate image acquisition and allows for post-processing adjustments like brightness and contrast

Threshold dose

is the minimum radiation dose required before a deterministic effect (like skin erythema) will occur.

Early radiation effects

(deterministic) increase in severity with dose and include symptoms like epilation and skin erythema

The cerebrovascular syndrome

occurs at extremely high doses and leads to rapid neurological failure and death within hours to days

SID (source-to-image distance)

is the distance from the x-ray tube to the image receptor and directly affects beam intensity

Grid interspace material

must be radiolucent so that primary radiation can pass through while scatter is absorbed by lead strips

Radiation protection principles

assume that all tissues and organs are potentially sensitive to radiation damage

Doubling dose (~1.0 Sv)

is the amount of radiation required to double the natural mutation rate in humans

Chest radiography uses 72-inch SID

to reduce heart magnification and improve image accuracy

Reducing scatter radiation

(via grids or collimation) increases radiographic contrast and improves image quality

Automatic collimators

adjust the field size to match the image receptor size, not the anatomy being imaged

Erythema (skin reddening)

typically appears 24–48 hours after receiving a high radiation dose (~2 Gy)

Natural background radiation

is a constant low-level exposure source and contributes significantly to overall lifetime dose

FDA radiation initiatives

focus on safe imaging practices, informed decision-making, and increasing patient awareness

If SID decreases

beam intensity increases at the receptor, so mAs must be decreased to avoid overexposure

Gastrointestinal syndrome

damages the intestinal lining, leading to severe fluid loss, infection, and high mortality rates

Below the threshold dose

deterministic effects will not occur regardless of how many times exposure happens

Digital imaging systems

have wide exposure latitude, meaning acceptable images can be produced over a range of exposures

mAs controls quantity of radiation

while kVp controls both beam quality (energy) and contrast