MI 237 - digital final- chloe

compton scatter

outer shell ionization, most scatter production and most dose to tech

photoelecctric

inner shell ionization, most significant dose to patient

what impacts scatter production

pt thickness, kVp and field size

who invented the first grid

Gustav Bucky (cross-hatched)

who improved grid design

Hollis potter (linear strips only, thinner strips)

potter bucky diaphragm

grid moved during exposure to blur grid lines

what is the interspace material in a grid

aluminium or plastic fiber because theyre radiolucent

what are the grid dimensions

height (H), thickness lead strips (T), distance between strips (D)

grid ratio equation

height of lead strips/distance between strips

focused grid

lead lines are angled to match the divergence of the beam

grid conversion formula

mAs 2/mAs1 = GCF2/GCF1

5 types of grid cutoff

off level, off angle, off center, off focus, upside down

what is the active or phosphor layer made of

barium fluorohalide bormides and iodides with europium activators

CR images will fade how much after 8 hours

25%

Photomultiplier tube (PMT)

collects the emitted light and turns it into an electrical signal

parts of the DEL

semi conductor, capacitor, TFT

what do scintillators do

xrays to light (CsL and Gadolinium)

Indirect DR steps

1: capture xray photon

2: coupling

3: collection

4: readout

5: digitization

what is the photodiode made of

amorphus silicon

CCD

xrays to light

CMOS

light to electrical signal (industrial)

what is the semiconductor in Direct DR made of

amorphus selenium

pixel size = what equation

FOV/matrix size

how does CR scanning work

red laser is rastor pattern then LED light to remove any leftover pixels , scans entire cassette (at least 30% should be scanned)

nyquist sampling theory

dictates the frequency of samplings must be greater than 2x the frequency of the incoming signal

what fixels dead dels

kernel

histogram type 1

main lobe and direct exposure spike (extremities)

histogram type 2

main lobe only (CXR, abdomen, pelvis)

histogram type 3

spike of light, main lobe, direct exposure spike (barium or hardwarre present)

what is determined by the histpogram anlysis

VOI and EI

4 types of noise

ambient, scatter, quantum, system

contrast to noise ratio (CNR)

systems ability to delineate subtle variations in the grayscale, want high CNR

Modular transfer function (MTF)

fidelity, measures accuracy of image compared to the actual object, want high MTF for good contrast

detective quantum effeiciency (DQE)

how well the photons are detected and converted into a signal or the eficiency in which the IR converts remnant radiation into a strong electrical signa, want higher DQE

spatial domain

location (orientation), kernels used here

intensity domain

color (brightness/contrast),

frequency domain

size, large objetcs have lower frequency

high pass filtering

frequency domain, supresses low frequencies/large objects, increases contrast

loww pass filtering

frequency domain, supresses high frequencies/smaller objects

what is the purpose of the input phosphor

xrays to light

what is the purpise of the photocathode

light to electrons

what is the purpose of the electrostatic lenses

focusies electrons toward anode

what is the purpose of the accelerating anode

attracts eletrons from photocathode, increases speed by 50-75%

what is the purpose of the output phosphor

electrons back into light (cadminium sulfide)

when you increase mag what happends to input phosphor diameter and focal spot

decreases, focal spot moves closer

mag factor equation

input phosphor diamter/input diameter during mag

minification gain

ratio of the inpit phosphor size compared to the output phosphor size

input phosphor diameter 2/output phosphor diameter2

brightness gain =

flux gain x minification gain

ON state for LCD

perpendicular, no light pass through

OFF state for LCD

electrical charge is being applied to the electrodes

HL7

manages non imaging data, how we get worklist on monitor

what ire RIS and HIS

LANs

what is image acquisition

first point of entry into MIMPS

what is display workstation

most interactive part of MIMPS

image manager/controller

brain of archive system

image storage/server

muscle of archive server

DICOM

standardizes programming languages between modalities, servers and workstations

lossless vs lossy

lossless = acceptable

lossy = irreversible

CAD

tools that draw attention to certain areas

kVp accuracy

annually, +/- 5

expouse linearity

annually, +/-10%

exposure reproducibility

annually, +/- 5%

AEC

annually +/-10%