Radiation Safety

Question 1

Biological Effects of ionizing radiation

Answer 1

Energy from radiation knocks electrons out of the orbit, creating reactive elements in the body

Question 2

Critical Target of Ionizing Radiation

Answer 2

DNA- blueprints for everything!!

Question 3

Direct Effect

Answer 3

Ionization and destruction of DNA

Question 4

Indirect Effect

Answer 4

production of free radicals that can then diffuse far enough to reach and damage the critical target (dna, rna, proteins)

MOST COMMON

Question 5

How does x-ray cause biologic damage

Answer 5

can use genetic problems, cancer
damage to DNA is critical
Stem cells, young tissue

Question 6

Radiosensitivity

Answer 6

The relative susceptibility of cells, tissues, and organs to harmful action of ionizing radiation

Question 7

Radiosensitivity of Cells and Tissue Types

Answer 7

Stem cells are MORE radiosensitive than mature cells
Young tissue is MORE radiosensitive than old cells
Tissues with HIGH metabolic is MORE rariosensitive then low activity

Question 8

Basic Principles of Radiation Safety

Answer 8

ALARA: As Low as Reasonably Achievable
1. Distance: Maximize distance from source (I=1/d2)
2. Time: minimize time of exposure. Limit retakes, minimize holding patients
3. Shielding: lead aprons, gloves, thyroid shields that protect from scatter beams (NOT the direct beam)

Question 9

Maximum Permissible Dose of radiation

Answer 9

Whole body= 5,000 mrem/year

Question 10

5 elements of X-ray Control Panel

Answer 10

mA Selector-
Focal Spot Selector -
Timer (msec)
mAs Selector (mA x time (msec))
kVp selector

Question 11

Steps in producing X-ray

Answer 11

1. Prep: electrons generated through electrical current in the filament of the cathode
2. Expose: x-rays produced when electrons interact with metal in the anode

Question 12

mA Selector

Answer 12

Controls quantity of x-rays
mAs= mA x time

Question 13

Focal Spot Selector

Answer 13

***Controls resolution of image (quality)
Large Focal Spot: less detail or resolution
Small Focal Spot: more detail, needed for small areas such as the carpus

Question 14

kVp Selector

Answer 14

Controls contrast of the image AND influences number of x-rays
Voltage across the x-ray tube
Higher voltage= higher e- speed= harder they hit the anode= higher beam energy

Question 15

Spacial Resolution

Answer 15

ability to see 2 objects that are close together as being separate

Question 16

Scatter Radiation

Answer 16

Beams that are partially absorbed by the body and then scattered into a different direction
Greater body area exposed = more scatter

Question 17

Collimators

Answer 17

restrict beams to confined regions (usually illuminated to reduce scatter and increase contract

Question 18

Grids

Answer 18

Prevent scatter from reaching the film

Question 19

Film Vs Digital

Answer 19

Film: superior spatial resolution
Digital: Allows for contrast adjust which out weights benefit of spatial resolution

Question 20

Radiographic opacities

Answer 20

Metal: Highest Attenuation- absorbs the most radiation
Bone
Soft Tissue
Fat
Air: lowest attenuation- absorbs no radiation

Question 21

Degree of Attenuation

Answer 21

depends on the subject opacity and the thickness of the object (ex: small sliver of metal may have same degree of attenuation as a large portion of soft tissue

Question 22

Summation Effect

Answer 22

two objects superimposed over each other have an overlapping portion that appears more opaque
(Think venn diagram)

Question 23

Silhouetting Effects (Boarder Effacement)

Answer 23

two objects of the same subject density are in contact and appear blended together
Ex: abdominal effusion (fluid and organs have the same density so no definition can be seen)

Question 24

Magnification

Answer 24

enlargement of an image relative to its actual size

Question 25

Distortion

Answer 25

Unequal magnification happens when an object is not in line with the center of the beam

Question 26

Motion

Answer 26

causes loss of spatial resolution DECREASED with DECREASED exposure time

Question 27

Radiograph Orientation

Answer 27

position cranial on left side of image and caudal on right side of image for laterals Right is on your left and left is on your right VD/DV

Question 28

How to various types of electromagnetic radiation differ?

Answer 28

wavelength and energy. As wavelength decreases, energy increases.

Question 29

Unique properties of x-ray

Answer 29

energy to penetrate matter. direct engirt - breaking DNA strands indirect- cree radicals from water into body

Question 30

What determines radioactivity

Answer 30

varies with maturation and metabolism immature cells -> more radiosentive cells with higher metabolic rates are more sensitive

Question 31

What is the fundamental difference in the shadow created by an x-ray beam versus a shadow created by visible light?

Answer 31

visible light creates a show that outlines the outside of the object. Xray can penetrate the object, creating multiple inter shadows all superimposed creating 2D images of internal structures

Question 32

Role of collimator

Answer 32

restricts or limits size of x-ray beam

Question 33

how does collimator improve the image

Answer 33

decreases scatter radiation

Question 34

what is the role of the grid

Answer 34

limits the most of Carter radiation that reaches the detector of film IMPORTANT FOR TEST

Question 35

Which image would have been taken with a grid (A or B)

Answer 35

Image A would have been taken with the gird. Note the higher contrast of image A.

Question 36

How do traditional film screen systems create a radiographic Image?

Answer 36

The function of the screens is to convert x-ray energy into visible light. It is the light that exposes the film.

Question 37

What are the 5 basic tissues densities seen on a radiograph?

Answer 37

Metal, bone, soft tissue, fat, air

Question 38

Why is it important of have the area of interest centered in the x-ray beam?

Answer 38

The central portion of the x-ray beams is essentially perpendicular and there is little distortion, where as the peripheral region of the x-ray beam diverges which can produce distortion.

Question 39

Distance

Answer 39

Maximize your distance from radiation source THE INVERSE SQUARE LAW!!! Double the distance from the source will reduce exposure by 1/4