Radiology Student RDH 2024

Nucleus of an atom contains

protons and neutrons

= atomic mass

K shell has the highest

binding energy

most useful for medical imaging

to remove an electron from orbit, energy must be

equal to or stronger than binding energy keeping electron in orbit

Who discovered radiation?

Roentgen 1895

radiation travels through space as

waves (electromagnetic radiation) or particles (Particulate radiation)

ionization

the process of adding or removing electrons from an atom or molecule, which gives the atom or molecule a net charge (not neutral)

Ionizing radiation

high in energy

capable of producing ions

the type of xray we use is

electromagnetic radiation

travels in a wave like motion

travels at the speed of light

has no charge and no mass

the ___________ determines the penetrating power of an xray

wavelength

Power Supply of an xray machine

electricity= power source (DC=direct current or AC= alternating current)

circuit= route the electrical current takes (high voltage, 65,000-100,000 volts)

transformer= mechanism used in an electrical circuit to increase or decrease the voltage. (can be step down, step up or auto)

Control panel of xray machine

displays on/off, kvp, mA, time (exposure time)

ampere= number of electrons

volt= force that moves electrodes from cathode to anode

kvp= detemines speed of voltage away from cathode (to anode) and determines quality.

What does the lead glass housing of an X-ray tube head contain?

Cathode and anode

What is the function of the molybdenum in an X-ray tube head?

Focuses direction of electrodes towards the anode

How is the anode in an X-ray tube head controlled?

By kvp settings

Where do electrons hit to produce x-rays in an X-ray tube head?

Tungsten target

What is the focal spot in an X-ray tube head?

Small area on the tungsten target where electrons hit and x-rays originate

What components are contained in the tube head of an X-ray machine?

X-ray tube, high/low voltage transformers, and insulating oil

What is the function of the PID in an X-ray machine?

Reduces exposure and directs x-ray beams

How does the copper stem contribute to an X-ray tube head?

Dissipates excess heat

the tungsten target is not the same as the

tungsten filament

if you go from a C to an A+ thats even better!

Cathode (-) to anode (+)

primary radiation basics

at the cathode, when the power switch is activated, the tungsten filament produces electrons, causing an electron cloud to form (this process is called thermionic emission)

When the exposure button is pressed, the

electrons barrel at high speed to the tungsten target and transform kinetic energy into x-rays. heat that is formed is dissipated through the copper stem.

photons (bundle of energy) leaves the x-ray tube as primary radiation

Xrays are formed at the tube mainly by two mechanisms braking radiation, and characteristic radiation

Braking radiation (Bremsstrahlung)

major source of xrays produced in dentistry (70%)

results when high energy electrons move come close to the nucleus of the tungsten atoms. (at the tungsten target). they then slow down (braking) and energy is released

characteristic radiation

electrons from the cathode dislodge electrons from the inner orbit (K or L shell) and make little xrays

scatter radiation

A form of secondary radiation that occurs when an x-ray beam has been deflected from its path by interaction with matter

may cause fogging of an xray

compton scatter

MOST COMMON TYPE (60%)

ionization occurs

-x ray photon knocks electron from OUTER orbit

-it can interact with other atoms

photoelectric effect

photon interacts with inner shell electron (less common type of scatter radiation, 30% of scatter radiation)

ionization occurs

coherent scatter

photons interact with electron, in outer shell, but matter is not altered

no ionization

sievert

SI unit of equivalent dose and effective dose

1 sv =

100 rem

1 Gy =

100 rad

exposure measurements

roentgen(standard)

Coulomb (SI)

Absorbed dose vs dose equivalent.

absorbed dose= dose of radiation

dose equivalent = absorbed dose adjusted to the biological damage potential of the particular type

Radiation damage (indirect and direct)

direct= damage to cell's protein, lipid barrier and DNA accounts for 1/3 of biological damage

indirect= radiation interacts with cells water content, and produces free radicals = ACCOUNTS for 2/3 of biological damage

somatic effect

occurs when the biological change or damage occurs in the irradiated individual, but is not passed along to offspring

cataracts, cancer

stochastic effect

When a biological response is based on the probability of occurrence rather than the severity of the change

ie. all or none

non-stochastic effect

also called deterministic effect. severity of the damage is dependent on the dose

Highly sensitive cells

immature cells

quickly dividing cells

younger persons cells

Less sensitive cells

highly specialized cells, mature cells, slowly dividing cells

In order from most to least sensitive cells

bone marrow

reproductive

intestines

blood

skin

immature bone, thyroid, kidney liver, CT

most sensitive part of cell= DNA and chromosomes

Natural resources of radiation

Radon (gas released from decaying material in the ground)

background radiation

a FMS is equivalent to background radiation from

1-2 days of background (naturally occurring) radiation

Dental exposure is similar in radiation exposure to a

commerical flight

a CT scan emits

100 TIMES the radiation of a dental radiograph

Filtration of radiation is produced by

aluminum discs

collimation

The restriction of the size and shape of the x-ray beam in order to reduce patient exposure.

(rectangular collimation reduces tissue exposure by 60% then circular)

standard PID lengths

8-16 inches

16 inches produce more parallel rays and reduce radiation exposure

ALARA

As Low As Reasonably Achievable

dosimeter

a badge that records exposure to radiation that is worn when taking x-rays, worn on waist

MPD

maximum permissible dose

MPD for occupationally exposed persons is?

5 rem = 50 mSv= 0.05 Sv/year

20mSv/year averaged over 5 years, not exceeding 50 mSv in any 1 year

MPD for non-occupationally exposed persons

1 mSv/year (0.1 rem/year)

(0.1 rem per year)

pregnancy and MPD

0.5 mSv per year

Beam intensity

total energy contained in the beam affected by mA, kVp, distance, and exposure time

To increase beam intensity, you must

increase kvp, mA, and time

decrease distance

to decrease beam intensity you must

decrease kvp, ma, time

increase distance

inverse square law

the intensity of radiation is inversely proportional to the square of the distance from the source of radiation

how to calculate inverse square law

how much longer? two times? then 2 squared = 4 then INVERT,

so beam is 1/4 as intense (if farther away)

**but if question is shortening distance, If closer, then 4 times MORE intense

Density

proportional to mA, kvp and time

To maintain similar density,

if time is increased, milliamperage must be ____

decreased, and vice versa

Contrast is dependent ONLY on?

kvp

sharpness of image is increased when

focal point on tungsten target is small

object to receptor distance is short

tube to receptor distance is long

distortion: elongation is caused by

underangulation

foreshortening is caused by

overangulation

bisecting technique

Primary beam aligns with bisecting line of tooth and sensor

paralleling technique

Intraoral technique of exposing periapical and bitewing images

in PID angulation, a negative angle is

up

positive angle is pointing down

SLOB rule

1. Same Lingual

2. Opposite Buccal

3. Lingual objects move in same direction as the tube head

4. Buccal objects move in the opposite direction as the tube head

herringbone pattern

film put in backwards

Focal trough (image layer)

A three-dimensional curved zone in which structures are clearly demonstrated on a panoramic image

waters projection

to evaluate the maxillary sinus area

MRI

for soft tissue

Shark fin error

lead apron above collqr

flat line in pan (frown)

patients chin tipped forward

opacity in middle of pan

spine slumped

large dark shadow over apices of maxillary arch

tongue

pt did not touch tongue to the roof of the mouth

thin and blurry anterior teeth

patient is biting too far forward

wide and fat anterior teeth

patient is biting too far back (away bite is fat and blurry)

New Patient Guidelines

Primary dentition= selected periapical/occlusal views or posteior bitewings if proximal surfaces cannot be visualized or probed.

Patients without evidence of disease= may not need xrays

Mixed dentition= BWs, Pan and select PAs as needed

Adolescent= Same as mixed dentition (above)

Patients with evidence of disease may need FMS

In general, if no evidence of disease NEW PATIENT with, mixed dentition, adolescents, and adults (including partially edentulous adults) need posterior BWs, Pan, and select PAs. if they have evidence of disease, these patients need a FMS.

Recall Patients at INCREASED RISK FOR CARIES

Primary dentition, mixed dentition,, adolescent= BW at 6-12 intervals if proximal surface is unable to be probed.

Adult, partially edentulous= Post BWs at 6-18 month intervals

Recall patient with no caries risk

if patient has no caries risk, intervals are:

primary, mixed dentition= BW 12-24 months

adolescents= BW 18-36 months

Adults= 24-36 months

incisive foramen

nasal septum

maxillary sinus

inverted Y

The intersection of the maxillary sinus and the nasal cavity

located above maxillary canines

nutrient canal

mental ridge

coronoid process

often seen in maxillary posterior PAs

coronoid process on the skull

anterior portion of the ramus

ramus of the mandible

vertical part of mandibleRa

maxillary tuberosity

often seen in maxillary posterior PAs

coronoid process

maxillary tuberosity

zygomatic process

maxillary sinus (found superior to maxillary molar/premolar area)

zygomatic process

zygomatic process on skull

cheekbone

mandibular canal

external oblique ridge

...A radiopaque band extending downward and forward from the anterior border of the ramus of the mandible

median palatine suture

NOT a fracture

radiopaque restorations

gold

amalgam

composite (darker though)

silver point

ortho brackets

retention pins

implants

slightly radiopaque restos

base material

gutta percha

porcelain