Unit III Creating the Image Chapter 26 Digital Image Management

Unit IIICreating the Image

Chapter 26Digital Image Management

Copyright © 2006 by Thomson Delmar Learning. ALL RIGHTS RESERVED. 4

Objectives

• Discuss advantages of using PACS in a medical imaging department

• Explain why a PACS network may require a separate computer network from the one used throughout an institution


Objectives

• Describe laser printers that can be used for digital images

• Explain soft-copy monitor display parameters


Objectives

• Identify types of storage available for digital images

• Discuss necessity for Digital Imaging and Communication in Medicine (DICOM) in medical imaging


Introduction

• Filmless environment has become possible today due to:– Faster data handling– High resolution monitors– Efficient storage options– Communication standardization


Introduction

• PACS– Hardware and software

• HIS/RIS

• Integration of the electronic medical record (EMR)


Digital Imaging Formats

• CR/DR

• Digital fluoro/angiography

• Computed tomography

• MRI

• Sonography

• Others


Image Acquisition

• Mini PACS

• Teleradiology

• Film digitizers– Laser digitizer– CCD digitizer


Laser Digitizer

• Laser scans film in raster pattern

• Light transmitted through film detected

• Converted into electronic signal and digitized


CCD Digitizer

• Light focused into a line shines through film

• Strikes linear array CCD detector

• A signal proportional to the amount of light striking the detector is sent to the computer


Image Distribution

• Network infrastructure and file management– Large impact on data distribution

• Images need to be distributed to radiologists and clinicians


Image File Size

• Dependent upon:– Matrix size– Bit depth


Gray Scale Bit Depth

• 8 – 32 bits– 1 byte = 8 bits

• File size of pixel– Multiplied by bit depth and divided by 8

• 8 – 32 bit depth• 1 – 4 bytes of storage


Bandwidth

• Controls the speed at which data can be sent over a network

• Bits per second– bps


PACS network

• Separate network allows for large data files to be moved quickly– LAN (local area network)– Ethernet

• Bandwidth 10 Mbps


Teleradiology

• WAN (wide area network)– Much slower

• Wireless networks– Currently even slower


PACS Difficulties

• Large files

• Limited bandwidth

• Special language

• Problems interfacing with HIS


HIS/RIS

• Hospital information systems– Database containing all patient medical

record information except for radiology

• Radiology information systems– Radiology specific database


HIS/RIS

• Ideally want interconnected HIS/RIS– RIS then sends needed patient information

to PACS


Filmless/Paperless Environment

• HIS registers patients and sends orders to RIS

• RIS generates worklist for the day

• PACS sends image and patient data to radiologist/clinician


Image Display

• Hard-copy display

• Soft-copy display


Hard-Copy Display

• Laser printers

• Dry processors


Laser Printer Components

• Laser source

• Collimator lens or beam shaping optics

• Beam modulator

• Deflecting mirror-shaping lenses

• Cylindrical deflection mirror

• Unexposed film storage

• Mechanical transport


Laser Printers

• 8 bit gray scale

• Light sources– Infrared (780-820 nm)– Solid-state diode (~670-680 nm)– Helium-neon (633nm)


Laser Printers

• Film exposed line by line in raster pattern

• Exposed film processed by dry or wet processor


Laser Printer Calibration


Wet Laser Film

• Contains silver halides

• Spectrally sensitive to red or infrared wavelengths– Will be fogged by red safelights

• Processed through developer, fixer, wash and dried


Dry Processors

• Thermally processed– Heat-sensitive film

• Silver-based emulsion• Dye microcapsules• Carbon-based adherographic printing


Silver-Based Emulsion Dry Processor Film

• Silver Benhate– Laser light creates latent image centers– Heat develops latent image centers


Dye Microcapsule DryProcessor Film

• Become permeable when exposed to laser

• Heat activates chemical processing

• Cooling causes processing to stop

• If stored in high heat film density can increase over time


Carbon-Based Adherographic Printing

• Film exposed to gallium arsenide laser

• Carbon particles adhere to areas exposed by laser

• Cover sheet sealed or laminated onto finished film


Dry Processor Film

• Shorter shelf life

• More sensitive to heat and humidity


Soft-Copy Display

• Monitors– CRT– Flat panel


CRT

• Components– Electron gun– Phosphor screen


CRT

• Electron stream– Raster pattern


Flat Panel LCD Monitors

• Light source shines on individual pixels

• Liquid crystal and hydrogenated amorphous silicon TFTs– Located between glass plates


Storage

• Typical large radiology department– 150,000 examinations– 3.2 Terabytes of memory

• 3-5 years of storage• 16 Terabytes


Storage

• Short-term– Local hard drive– PACS server and RAID

• Long-term– Jukebox of disks or tapes


Storage

• Off-site– Ensures integrity if there is a catastrophic

event


DICOM

• Standards-based protocol created by joint efforts of ACR and the National Electrical Manufacturers Association (NEMA)

Documents

Unit III Creating the Image Chapter 26 Digital Image Management