Intro to Digital Imaging and PACS

what is digital imaging

any imaging accusation process that produces an electronic image that can be viewed and manipulated on a computer

what type of signal is xray

analog

analog data

continuously varying electrical current

ADC

analog to digital converter

digital data

defines quantities of current

DAC

digital to analog converter

• can help send data faster

computer

the machine that performs mathematical computations

algorithms 

preprogrammed instructions

computer program

collection of thousands of interrelated algorithms

computer language

2 system alphabet (binary)

• 1 = on

• 2 = off

each binary number is a bit

an 8-bit word is a byte

computer memory rated in terms of byte memory

cloud computing

networks/gateways, servers

hardware 

CPU 

memory, input, and output devices

software 

computer programs, applications, or operating systems stores as a code within hardware

operating system

integrates hardware with software

film/screen system

cassette contains film

x-rays expose cassette 

crystals in the screen emit light

light and x-rays expose film

• over 90-99% from light 

• less than 1-10% from x-ray 

produces latent image in film emulsion

film is processed chemically to produce an image

image can be viewed on a light box

in film/screen process, what is exposing the film more

light 

• 90-99% from light 

• 1-10% from x-ray

computed radiography

conventional x-ray equipment

cassettes with photostimulable phosphor 

uses a plate reader 

CR photostimulable phosphor plate

uses barium fluorohalide

x-rays strike phosphor 

plate placed in reader

laser beam releases energy of latent image 

light picked up by photomultiplier tube/converted to electronic 

ADC converts energy to digital 

sent to computer for processing 

Flat panel detectors (DR)

image receptor is contained within table, or a separate device is attached via cable

indirect capture systems (DR)

2-step process

absorbs x-ray

convert energy to light

light collected and converted to electrical signal

ADC converts to digital signal and sends to computer

direct capture system (DR)

x-ray energy converted to electric signal directly 

electrical signal sent to ADC and then to computer 

plumbicon and vidicon TV tubes

display of “real time” images (fluoro)

The digital image

converted into numerical values for transmission and processing

detector acquires image information

analogue signal is converted to format

a matrix gives form to the image

matrix 

pattern of cells in rows and columns 

pixel

individual boxes or picture elements 

what determines resolution 

pixel size 

smaller pixels = better resolution

larger matrix has _____ pixels

smaller

brightness 

intensity at a specific location within an image

how to calculate pixel size

P = FOV/matrix

DICOM stands for:

digital imaging and communication in medicine

DICOM

common computer language that allows various devices within imaging to communicate and share data 

communication protocol standards 

two common standards in PACS are

DICOM 

• addresses the communication of images/data

Health Level-7 (HL-7)

• addresses the communication of textual data 

• integrates hospital info to radiology info

  • pt demographics

  • type of exam

  • rad reports

Integrating the Healthcare Enterprise (IHE)

removes redundant information between computer-based healthcare information systems and PACS

what does PACS stand for

picture archive and communication systems

PACS

a networked group of computers, servers, and archives that manage digital images

connected to HIS (hospital information system) and RIS (radiology information system) system 

3 components of PACS

acquisition (modalities)

display (workstations)

storage (archive server)

Hospital Information System (HIS)

computer based system used to collect and process data to provide users with info needed for problem solving and decision making

functions of HIS

pt scheduling

appointment reminders

invoice service

monitor insurance coverage

majer components of HIS

clinical information system (CIS)

administrative information system (AIS)

radiology information system (RIS)

integrates and or communicates with the HIS and PACS systems

specific to the needs of the radiology department that are not contained in the hospital system 

features of RIS 

order entry 

scheduling imaging exams

generation of Rad reports 

billing preparation

quality assurance 

Electronic health record (EHR) or Electronic medical record (EMR)

electronical version of an individual pt collection of medical documents

provides data and quality of care

computer networks

allow information to be transferred to be transferred and shared among computers and consists of both hardware and software

• LAN

• WAN

LAN

Local area network

connects computers separated by short distances

WAN

wide area network 

connects computers separated be large distances

bandwidth

data transfer rate

high bandwidth = instant connection

storage architectures

NAS

SAN

DAS

VNA

NAS

network attached storage 

software installed in hardware 

SAN

storage area network 

solely for image storage

DAS

direct attached storage

storage directly attached to single computer

is not networked

VNA

vendor neutral archive

system requires images to be stored in a nonproprietary format allowing for interchange

archive architectures

RAID redundant array of independent discs

• storage for a few weeks/months 

• quick retrieval 

“jukebox” 

• discs or tapes are retrieved by a robotic technology 

images compression

significantly reduces the size or volume of data to reduce storage required, bandwidth required to transmit images, and process times

lossless compression

allows all original information in image to be retained

is fully reversable

lossy compressions

loses data once image is compressed and uncompressed

loss of resolution when reversed

compression rations

element that reduces the size of the image file 

teleradiology 

moving images via modem, phone, or cable lines to remote locations

radiologists viewing images from home