Lecture 1: Intro/X-ray Production/Image Formation/QUIZ 1 (Winter)

Question 1

Radiology is used as a clinical tool for 4 main things:

Answer 1

1) detect presence or absence of disease
2) specific disease recognition and/or localization
3) progression of disease
4) evaluation of therapeutic success of failure

Question 2

4 types of diagnostic imaging

Answer 2

1) MRI
2) Nuclear medicine (i.e. PET scans)
3) Radiography (i.e. CT, fluoroscopy)
4) Ultrasound (i.e. echocardiography)

Question 3

who discovered x-rays?

Answer 3

Roentgen

Question 4

who discovered radioactivity?

Answer 4

Becquerel

Question 5

radiation

Answer 5

the transfer of energy as particles or electromagnetic (EM) waves. Radiation differs in its wavelength, frequency, and energy

Question 6

energy and wavelength are (directly/inversely) proportional?

Answer 6

inversely

Question 7

ionizing radiation

Answer 7

radiation with sufficient energy to cause the atom or molecule that it reacts with to lose an electron; an essential characteristic of high energy radiations when interacting with matter.

Question 8

The energy of electromagnetic radiation is inversely proportional to:

Answer 8

wavelength

Question 9

light travels at the same SPEED, but at different ENERGIES because of the varying frequencies and wavelengths of light

Answer 9

:)

Question 10

How are x-rays produced? Where does this occur?

Answer 10

through the conversion of energy within particulate radiation (electrons) to electromagnetic energy (x-rays). Occurs inside the x-ray tube when high speed electrons collide with the metal anode

Question 11

Which end of x-ray tube is positive? negative?

Answer 11

positive: anode
negative: cathode

Question 12

What causes electrons to be drawn across the negative and positive ends of the x-ray tube?

Answer 12

high voltage

Question 13

what metal comprises the cathode filament?

Answer 13

tungsten

Question 14

fx of focusing cup

Answer 14

negatively charged and focuses the electron cloud from the cathode toward the anode

Question 15

the cathode of an x-ray tube has (low/high) voltage and (low/high) resistance

Answer 15

low voltage, high resistance

Question 16

what metal comprises the anode (target)?

Answer 16

tungsten, rhenium

Question 17

The (cathode/anode) determines the NUMBER of electrons?

Answer 17

cathode

Question 18

The (cathode/anode) determines the ENERGY of electrons?

Answer 18

anode

Question 19

The anode has (low/high) voltage and (low/high) resistance

Answer 19

high voltage, low resistance

Question 20

kVp

Answer 20

• the energy potential applied from cathode to anode
• kilovoltage peak applied across the tube
• refers to the maximum energy of xrays
• determines how many of the x-rays make it through the patient

Question 21

mA:

Answer 21

• (milliamperes) controls the resistance of the circuit through the tungsten filament
• refers to the NUMBER of electrons boiled off the tubngsten tube/number of x-rays produced

Question 22

keV:

Answer 22

the duration of a photon/EM wave

Question 23

s-time

Answer 23

• the duration of a radiographic exposure

- combined with mA, determines # of x-rays that will be produced during a given exposure

Question 24

Which of the following is true of electromagnetic radiation?

a: has properties of a wave
b: has properties of a particle
c: travels at the same velocity regardless of wavelength or frequency
d: has a charge

Answer 24

a,b,c

Question 25

Bremsstrahlung

Answer 25

the process by which an x-ray is emitted by an e- during loss of kinetic energy

Question 26

In the diagnostic energy range typically used, the primary interaction of x-rays w/ matter is:

Answer 26

compton scatter

Question 27

ALARA stands for:

Answer 27

As Low As Reasonably Achievable

Question 28

Penumbra

Answer 28

a blurred area around the image of an object that results from use of a large focal spot, or decreased FOD

Question 29

quantum mottle

Answer 29

- relates to the # of photons that are incident on the detector and cause film blackening - mottle caused by the statistical fluctuation of the number of photons absorbed by the intensifying screens to form the light image on the film

Question 30

summation

Answer 30

the perceived increase in opacity observed when two objects are superimposed upon one another, but not necessarily in the same plane

Question 31

border effacement

Answer 31

the inability to distinguish margins of objects that are of the same opacity and in contact w/ one another

Question 32

the 5 radiographic opacities are:

Answer 32

gas, fat, soft tissue, mineral, metal

Question 33

3 settings we have control over when taking a radiograph

Answer 33

time (sec), mA, and kVp

Question 34

What happens if kVp is set too low?

Answer 34

rad will be a shadow of an image b/c x-rays don't make it through the patient

Question 35

fx of filtration

Answer 35

removes the low energy x-rays that we don't need (won't be diagnostic, and may cause harm)

Question 36

fx of collimation

Answer 36

reduces scatter, protects patients, and focuses on an area of interest when taking a rad

Question 37

clicker Q: X-rays are produced in an x-ray tube by:

Answer 37

interactions of electrons with metal

Question 38

photoelectric effect vs. compton scatter

Answer 38

Both involve the ejection of an electron when light strikes a metal. Photoelectric effect: - photon is absorbed and does NOT contribute to image formation, electron is released - Usually occurs at lower energies Compton scatter: - photon is scattered at some angle and contributes to image formation, and the electron is released with another direction - Usually occurs at higher energies - degrades image

Question 39

increased kVp --> likelihood of Compton scatter

Answer 39

increases

Question 40

increased kVp --> likelihood of photoelectric effect (PE)

Answer 40

decreases

Question 41

increased atomic number --> likelihood of PE

Answer 41

increases

Question 42

thickness/density of object --> compton scatter

Answer 42

increases

Question 43

attenuation

Answer 43

reduction in intensity of the primary beam as it travels through an object/patient (i.e. via absorption, scatter)

Question 44

latitude

Answer 44

- the ability of a film to record differences in density - maximum difference in radiographic density of anatomical structures that can be evaluated on a given radiograph - inversely related to contrast with many shades of gray - obtained with HIGH kVp and LOW mAS - used for abdomen and thoracic evaluation

Question 45

contrast

Answer 45

- the state of being strikingly different from something else, typically in juxtaposition or close association - difference in the photo density (optical whiteness/blackness) b/w 2 adjacent anatomic structures - short gray scale - obtained with LOW kVp and HIGH mAS - used for musculoskeletal evaluation

Question 46

clicker Q: when creating a radiograph of the thorax, your settings should aim to:

Answer 46

decrease the inherent contrast in the image, and use a higher kVp

Question 47

increasing kVp --> contrast

Answer 47

decreases

Question 48

more scatter will be produced with increases in:

Answer 48

kVp, field size (collimation), and patient thickness

Question 49

2 methods to reduce scatter after x-ray prod.

Answer 49

grids, air gap

Question 50

What are grids?

Answer 50

- series of radioopaque material (lead) alternated with strips of radiolucent material - fx: transmits only those x-rays on a straight line from the source to the image receptor - placed b/w the patient and the film to remove scatter prod. by the interaction of the primary beam with the patient

Question 51

grid ratio

Answer 51

height of strips/space between the strips (standard ratio = 8:1, 10:1)

Question 52

purpose of the image recording system

Answer 52

to form a visual display and permanent record for future comparison

Question 53

what do intensifying screens do?

Answer 53

convert x-ray energy into visible light which then exposes the film. Film by itself is an inefficient detector of x-rays

Question 54

4 main components of the intensifying screen and their functions?

Answer 54

1) protective coating: prevents damage 2) phosphor: active layer that emits light 3) reflective layer: reflects light photons toward film 4) base: support layer

Question 55

screen speed

Answer 55

relative number that identifies the efficiency of conversion of x-ray radiation into light

Question 56

3 factors that determine screen speed

Answer 56

1) phosphor type 2) crystal size 3) secondary factors (dye, reflective layer)

Question 57

faster screen speed --> detail of image

Answer 57

decreases

Question 58

advantages of intensifying screens

Answer 58

- decrease x-ray dose to the patient, exposure times | - increase image contrast

Question 59

disadvantages of intensifying screens

Answer 59

- decrease detail | - artifacts

Question 60

Computed Radiography (CR)

Answer 60

- uses cassettes w/ image plate - phosphorescence records and stores latent image - read by laser

Question 61

Direct Digital Radiography (DR)

Answer 61

- x-rays converted to electronic signal | - immediate display

Question 62

What is DICOM?

Answer 62

(Digital Imaging and Communications in Medicine) - standard for handling, storing, printing, and transmitting info for medical imaging. - safe, legal storage of medical record document

Question 63

what is PACS?

Answer 63

(Picture archive and communication system) | -storage of DICOM images in a complex database