ROENTGENOLOGY Flashcards by yan mae de

the intensity of gamma rays decreased with the distance from the source is increased

Inverse Square Law
I=D
Intensity
Distance

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smaller focal spot

greater resolution of image

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Xray tube in dental xray unit is

Coolidge

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Power supply

Tube Current

Tube Voltage

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determines the follow of electrons on the cathode

Most recommended:

Tube Current

7-15 mA

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generates xrays thru electrons

recommended

Tube voltage

recommended: 65-70 kVp

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transformation is to increase the voltage

Step Up

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transformation is to control the voltage dose

Step Down

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stated that the current flowing through a conductor is Equal to the voltage divided by the resistsnce of a conductor

Ohm's Law
V= I/R 
Voltage
I= current
R= resistance

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Proper kv for dental films is influenced by

Density of the tissue

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main fx that influences the time of film exposure

Voltage

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result from the electrons interacting with nuclei

Bremsstrahlung (breaking)

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excess radiation

Characterisitic

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when photons collides with loosely bound in outer shell of an atom

Compton (62%)

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is produced within thr px through compton interaction

Scatter radiation

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removes 100% scatter radiatiom to the px

Grid

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when there is ionization and emits characteristic radiation

Photoelctron 30%

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when there is NO change to absorbing atom & photon of scattered radiation is produced

Coherent 8%

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radiation coming directly out of the target

Primary radiation

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producespd when primary radiation is filtered & collimated

Useful beam

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produce from parts other than focal spot

Stray

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narrows the xray beam & restricts the area of the px face exposure by more than half
made up of lead & tungsten

Rectangular Collimator

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is the process of removing lower energy photon. made up of aluminum with 1.5 thick

filtration

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worn prevent stray radiation made up of lead (best metal to stop radiation)

Apron

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made up of scattered rays

Secondary radiation

ways to prevent 2ndary radiation

standing 6ft | 90-135* from the focal spot

image producespd after exposure to radiation & before processing

Latent image

refers to the amount of radiation required to produce a radiographic film of standard density

Exposure

diffrence in density appearing on a radiograph

Contrast

greatest contrast (short scale)

lowest kvp highest grid ratio smallest area of collimation

degree of darkening of exposed & processed xrays

Density

contrast opaque | hard

enamel dentin alb amalgam

contrast lucent soft

pulp pdl sinus air

least density

Direct exposure technique | smallest area of collimation

represent thr range of exposure that will produce diagnostically acceptsgle densities on a film

Latitude

represent the amount of radiation required to produce a radiograph of acceptable densities

Speed

slow speed film smaller grain better definition more exposure time

A, B, C

hignspeed film | most commonly used is best way to reduce exposure

D E F | Ecta

Q. most radioapaque tissue on the oral cavity most radiolucent tissue on the oral cavity most radioapaque restorative material most radiolucent restorative material

Enamel Air Amalgam & Gold Methacrylate

contains silver halide & silver bromide grains | the side that faces the xray tube intended to br exposed

Emulsion

made up of polyester polyethylene terephthalate (0.18mm) | support the emulsion by preventing the passage of light

Base

excessive bending of the film result to herringbone appearance of the film phalangioma penumbra

Distortion Improper position of film Appearance of thumb Shadow- distance of focal spot is too far

primary cause of injury because they produce free radicals

Ionization

amount of energy that an ionizing particle transfers to the material traversed permunit distance

LET | Linear Energy Transfer

with dose threshold requiring at least moderate level of exposure

Deterministic effect

change resulting from damage to DNA of a single cell

Stoachastic effect

earliest sign in the oral cavity

Mucositis - Candidiasis

common w/ more thsn 40 gy dose

ORN

when there is absence of radiation in the cell divisiom

Recovery period

Radiosensitive cells

1. Lymphocytes 2. Bone Marroe 3. Reproductive cells 4. Youngnbone

radioresistance cell

mature bone muscle cell nerve cell

radiosensitivity of cells depends on

Mitotic future mitotic activty degree of differentiation

critical orgsns on dentsl vicinity

Skin thyroid gland bone marrow lens

reduce radiatiom of the skin of the pt

Aluminum filter

skin exposure is low as

1-10mR

determines the quantity of radiation exposure

Dosimetry

twin film sensitive to xray beta & gamma rays

Film Badge Dosimetry

recommended dose for personal monitoring in the dental office

300 mR

max. wholembody radiation dose

50 milliseivetprt per year

human lethal dose of radiation

600 rads

proximal caries. overhang restoratiomn & alveolar bone advantage disadvantage

Bitewing absence of cervical burn out endo , periapical lesion

occlusal soze

57x76mm

paralleling device where the xray beam is perpendicular to the long axis of the tooth prevent distortion of the imag

Paralleing technique (long cone)

placed right angle or perpendicular to the long axis of the tooth

Bissecting Angle technique

detemines the working length of super imposed canls & facio lingual orientation of instruments

Slob technique/Cone shift/ Clark shift/buccal object rule

they all have intensifying screen to reduce exposure time

Extra oral

4 layers if intensifying screen

Base Reflective layer Protective layer Active layer

made up of polyesterr

Base

made up of titanium oxide (1mm)

Reflective layer

made up of cellulose (0.7-0.8mm)

Protective layer

made up of calcium tungstate

Active layer (Phosphor)

it measure anthropometric landmarks used to assess skeletal, dental, soft tissue landmarks , planes , angles & distances to classify craniofacial growth It can evaluate occipital, c1 & c2 fracture

Lateral skull projection (cephalometrics)

film size of lateral skull projection

8x10 inch

mainly used for zygomatic fracture

Submentovertex / Jug handle

mainly of maxillary sinus one of the best views for coronoid process can detect hanging drop sign oresent in blow outnfrscture uses campbell's & trapnell's lines for mid face fractures

Water's View ( Occipitomental)

show skull vault & frontal sinus

PA skull (Caldwell)

shows fracture of condyle

Reverse town projection (open mouth

used to produce an image by reducing the silver bromide & silver halide to solid silver grains

Developer

below 68*f will result to

Deactivation of hydroquinone

when there is dramatic change in temp. from one bath to another there will be distortion of emulsion surfsce

Reticulation

exhausted developer will produce

Light radiographs

it should have red bulb located 4 ft above worikng area

Dardk room

used to check safe lighting of darkroom | leakage of light will cause film fog

Penny test