Computer Networks, PACS and Teleradiologyradres.ucsd.edu/secured/CH15-17 2015-Sinha-Nelson... ·...

Computer Networks, PACS and Teleradiology


Shantanu Sinha, Ph.D. and, T.R. Nelson, Ph.D.

University of California, San Diego

Radiology Physics Lectures: PACS


Communication Networks


Digital Medical Imaging Rationale

DIGITAL IMAGING

Cost Reduction

Improved Image Quality

Work Flow

Communication

•No developing •Eliminate lost films •Reduce retakes •No film file room •No darkroom •No waste disposal •Throughput

•Immediate image •High contrast •Wide exposure latitude •Image enhancement •Potential dose reduction •Quantitative imaging

•Connection to HIS, RIS •Archive, retrieve (DICOM) •Expert opinion referral •Teleconferencing •Improved accounting


Digital Medical Imaging Networks


Review Question


Computer Networks

• Local Area Networks (LAN) – In the medical center

– At home

• Wide Area Networks (WAN) – The Internet

– Between UC campuses

– Roadrunner, Cox, etc.


Computer Networks

• Area networks - infrastructure connecting workstations, servers and other locations – LAN - local area network (immediate vicinity)

– WAN - wide area network (extended area)

• Byte - unit of data (typically 8 bits - 255 possible values) – 1 kilo Byte (kB) = 1000 Bytes

– 1 mega Byte (MB) = 1,000,000 Bytes

– 1 giga Byte (GB) = 1,000,000,000 Bytes

– 1 tera Byte (TB) = 1,000,000,000,000 Bytes


Data Transfer Rate

• Bandwidth – Megabits/second (Mbits/s)

– Gigabits/second (Gbits/s)

• Throughput – Maximum data transfer rate achieved

• Packets – Bunches of bits

– Called - frames, datagrams, cells • Info regarding destination and content

• Node - device on a network, connected by ‘links’

• Network Address: Unique Id of each interface



– Layer 1: Physical - wiring – L 2: Data link - packet

format, access control, error checking, in Hardware.

– Network - connection between computer interface/switches/routers/LAN/WAN/etc.

– Transport - translates commands to interface card

– Application - user interface and applications

Network Protocol Layers:


Communication Networks: Medical PACS Network Topology

Router

• Bus Topology:

– All nodes connected to a single cable

• Star: all connected to a central node.

• Ring: each connected only to 2 adjacent nodes.

• Media access control protocol: – Token: permission to

transmit

• Segments of LAN connected by bridges, switches or routers



• LAN – Ethernet - 10, 100 or 1000 MB/s

– Fiber Distributed Data Interface (FDDI) • Optical fiber network - 100 MB/s

– Asynchronous Transfer Mode (ATM) • Small packets / very fast - 155 MB/s

• extended Local Area Network (eLAN) – All above types

– Include repeaters, bridges (selective packets),



• Communication Networks

– Modem (500 KBits/sec

– Asynchronous Transfer Mode (ATM)

• (2-500 MB/s)

– Fast Ethernet

• (100 MB/s)

– Ethernet

• (100 MB/s)

– Gigabit

• (1000 MB/s)

– FiberChannel

• (1000 MB/s)

• Network Connection

– Twisted Pair

– Coaxial

– Fiber Optic

– Wireless



• Very Large Networks – Links multiple LANs

– Routers • Receive and forward packets

• Use routing tables to optimize delivery

– Transmission Control Protocol / Internet Protocol • TCP/IP

• Transfer protocols used by routers to move data

• TCP - Layer 4

• IP - Layer 3 - computer address (e.g. 132.239.106.243) – hostname - trn_office.ucsd.edu (TRN Office Computer)


Communication Protocols

• traceroute 132.239.106.243 • traceroute to 132.239.106.243 (132.239.106.243), 64 hops max, 40 byte packets

• 1 192.168.1.1 (192.168.1.1) 1.236 ms 0.834 ms 0.707 ms

• 2 10.72.0.1 (10.72.0.1) 10.794 ms 15.480 ms 10.544 ms

• 3 cvsdca1-rtr1-ge2-1.san.rr.com (24.25.192.230) 11.300 ms 11.648 ms 7.531 ms

• 4 wcsdca1-gsr3-srp0.san.rr.com (24.25.196.30) 8.430 ms 8.406 ms 11.656 ms

• 5 so-2-0-0-0.gar1.sandiego1.level3.net (4.79.36.9) 8.433 ms 10.428 ms 11.274 ms

• 6 ge-7-0-0.mp1.sandiego1.level3.net (4.68.113.93) 12.094 ms 18.947 ms 11.288 ms

• 7 as-2-0.bbr1.losangeles1.level3.net (64.159.1.30) 14.514 ms ae-0-0.bbr2.losangeles1.level3.net (64.159.1.126) 13.436 ms as-2-0.bbr1.losangeles1.level3.net (64.159.1.30) 12.606 ms

• 8 ae-24-54.car4.losangeles1.level3.net (4.68.102.111) 14.606 ms ae-14-55.car4.losangeles1.level3.net (4.68.102.143) 14.151 ms ae-24-52.car4.losangeles1.level3.net (4.68.102.47) 11.834 ms

• 9 lsanca3lcx1-ceic-14-0.wcg.net (64.200.200.50) 15.046 ms 35.930 ms 19.691 ms

• 10 inet-ucsd-ucsd1--lax-isp-ge.cenic.net (137.164.24.210) 15.337 ms 16.306 ms 19.376 ms

• 11 nodem-msfc--ucsd-gw-ge.ucsd.edu (132.239.255.129) 18.317 ms 16.605 ms 16.854 ms

• 12 nodem-msfc-nodev-msfc.ucsd.edu (132.239.254.254) 16.113 ms 18.660 ms 19.450 ms

• 13 132.239.106.243 (132.239.106.243) 19.230 ms 17.832 ms 18.788 ms



• Internet - international network of networks

• internet - network of networks using TCP/IP

• Other TCP/IP protocols – FTP - file transfer protocol – SMTP - simple mail transfer protocol – TELNET - access remote computer – HTTP - hypertext transfer protocol - web – URL - universal resource locater – WWW - world wide web -

• Internet connected servers that store documents

• HTML - hypertext markup language, XML - extended ML


Communication Networks • Long-distance links



• Network Security – Computers connected to network are vulnerable

– Improve security by limiting access • Disconnect from network

• Install firewall – Filters packets

– Limits access to approved computers

– Requires password for access through firewall

• Encrypt data / traffic

• Authentication to validate sender / receiver


PACS and Teleradiology

• Picture Archiving and Communication System – System for storage and transfer of radiologic images

• Teleradiology – Transmission of radiologic images to site remote from

acquisition site

• Images – Must not be significantly degraded compared to original

• Contrast

• Spatial Resolution


Teleradiology Ethical Standards

• ACR Ethics Rules - " A diagnostic radiologist should regularly interpret radiographs and other images only when the radiologist reasonably participates in the quality of medical imaging, utilization review, and matters of policy which affect the quality of patient care."


Mini PACS system



• Medical PACS Network


Large PACS System


Review Question



• Digital Image Acquisition – All modalities

• Radiography, Fluorography, CT, MRI, Nuclear, Ultrasound

• Direct digital imaging (CCD, Selenium plates, etc.)

• Film digitizers – Laser

– CCD


Image Storage


CCD Film Digitizer


Laser Film Digitizer


Film Digitizer ADC Transfer Function



• Digital Imaging and Communications in Medicine (DICOM) – Joint project of ACR and NEMA

– Developed to ensure compatibility between vendors

– Specifies standard formats for data objects • Patients

• Studies

• Images

• Requests – find, move, store, get



• DICOM header



0002,0002 Media Storage SOP Class UID: 1.2.840.10008.5.1.4.1.1.7

0002,0003 Media Storage SOP Inst UID: 1.2.840.113619.2.5.1762892410….

0002,0010 Transfer Syntax UID: 1.2.840.10008.1.2

0002,0012 Implementation Class UID: 1234567890.1998.310

0008,0008 Image Type: DERIVED\SECONDARY\SCREEN SAVE

0008,0016 SOP Class UID: 1.2.840.10008.5.1.4.1.1.7

0008,0018 SOP Instance UID: 1.2.840.113619.2.5.1762892410.2069….

0008,0020 Study Date: 20050113

0008,0023 Image Date: 20050113

0008,0030 Study Time: 203431.000000

0008,0033 Image Time: 204221

0008,0050 Accession Number: 1-13-2005

0008,0060 Modality: CT

0008,0064 Conversion Type: WSD

0008,0070 Manufacturer: GE MEDICAL SYSTEMS

0008,0080 Institution Name: UCSD THORNTON

0008,0090 Referring Physician's Name: NELSON

0008,1010 Station Name: TCT1_OC0

0008,1030 Study Description:

0008,103E Series Description: Screen Save

0008,1090 Manufacturer's Model Name: LightSpeed Plus

0010,0010 Patient's Name: NLST^QA^IMAGE

0010,0020 Patient ID: 1-13-2005

0010,0030 Patient's Birth Date:

0010,0040 Patient's Sex:

0010,1010 Patient's Age: 000Y

0018,1030 Protocol Name: 9.3 NELSON

0018,5100 Patient Position: HFS

0020,000D Study Instance UID: 1.2.840.113619.2.55.1.1762892410.2223….

0020,000E Series Instance UID: 1.2.840.113619.2.5.23192418.1105648471.99.5

0020,0010 Study ID: 7382

0020,0011 Series Number: 99

0020,0013 Image Number: 459

0028,0002 Samples per Pixel: 1

0028,0004 Photometric Interpretation: MONOCHROME2

0028,0010 Rows: 512

0028,0011 Columns: 512

0028,0100 Bits Allocated: 16

0028,0101 Bits Stored: 16

0028,0102 High Bit: 15

0028,0103 Pixel Representation: 1

0028,1050 Window Center: 40

0028,1051 Window Width: 400

0028,1052 Rescale Intercept: -1024

0028,1053 Rescale Slope: 1

0028,1054 Rescale Type: je ne sais pas

7FE0,0010 Pixel Data: 1178

------------------------

Title: UCSD_Thornton_LS_Plus_H2O_1_2005.dcm

Width: 512 pixels

Height: 512 pixels

Bits per pixel: 16 (signed)

Display range: -160 - 240

No Threshold

Calibration Function: y = a+bx

a: -32768.000000

b: 1.000000

Unit: "gray value"

• DICOM header



• Networks for Image and Data Transfer – DICOM image data

– Radiology Information Systems (RIS)

– Hospital Information Systems (HIS)

• Communications Standard – Health Level 7 (HL7)

• Radiology worklists

• Exchange of clinical, laboratory & imaging reports

• Keeps patient records correctly assigned

• Controls pre-fetching of data to improve efficiency

• Interface to WWW – improves remote access


Review Question



• Image storage – Different sizes and formats for each modality

• Radiography, Fluorography, CT, MRI, Nuclear, Ultrasound

– Image data may be compressed or un-compressed

– On-line storage (< 1 sec) • Recent studies

– Near on-line storage (1-5 seconds) • Recent past

– Off-line (> 1 minute) • Archival


Medical Imaging Patient Storage Requirements

Imaging Study Image Size Images/Pt MBits/Pt MBytes/Pt

CT 512 100 210 25

MRI 512 100 210 25

Ultrasound 512 50 105 13

Nuclear Med 256 50 53 7

Plain Film (low)

2000 10 640 80

Plain Film (high)

4000 10 2560 320

2

2

2

2

2

2


Medical Imaging Storage Requirements

Studies/Month CT MRI US NucMed DX (low) Angio

Vascular Interv

OPC

Thornton 229 97 186 87 1150 150 40

Hillcrest 840 250 625 345 5260 984 1774

4th & Lewis 162 320

IMG 227 593

Total Studies (All Sites)

1069 347 1200 432 7323 1134 1814

MBits/study 210 210 105 53 640 640 640

Total Storage/Month

(GBytes) 28 9 16 3 586 91 145

Total Storage (All Groups) 878 GBytes/month 10,540 GBytes/year

Total (CT,MRI,US,Nucs) 56 GBytes/month 672 GBytes/year

Data Archive Storage Requirements (GBytes) (1994-1995 Data)


Medical Imaging Response Time

Image Based Task

0.1 1 10 100 1000

Interactive Review

Emergency Interpretation

Consult/Review

Archival Transfer

Response Time (sec.)


Medical Imaging Network Performance

Single Image

File Size (MBits)

0.1 Mb/s 1 Mb/s 10 Mb/s 100 Mb/s

1000 Mb/s

CT 2.1 21 2.1 0.2 0.02 0.002

MRI 2.1 21 2.1 0.2 0.02 0.002

Ultrasound 2.1 21 2.1 0.2 0.02 0.002

Nuclear Med

1.1 11 1.1 0.1 0.01 0.001

Plain Film (low)

64 640 64 7 0.7 0.07

Plain Film (high)

256 2560 256 25 2.5 0.25

Network Transfer Time (s) for a Given Transfer Rate


Medical Imaging Network Performance

Network Transfer Time (s) for a Given Transfer Rate

Patient Study

File Size (MBits)

0.1 Mb/s 1 Mb/s 10 Mb/s 100 Mb/s

1000 Mb/s

CT 210 2100 210 21 2.1 0.2

MRI 210 2100 210 21 2.1 0.2

Ultrasound 105 1050 105 11 1.1 0.1

Nuclear Med

53 530 53 6 0.6 0.06

Plain Film (low)

640 6400 640 64 6.4 0.6

Plain Film (high)

2560 25600 2560 256 25.6 2.5



• Image Storage – Redundant Array of Independent Disks (RAID)

– Various implementations

» Duplication -> to complex error correction



• Near on-line storate - Tape Archive

• On-line storage - RAID

Tape/ Disk RAID


Review Question


Data Storage and Compression


Data Transmission


Image Display

Keyboard

Pointing Device

CRT / LCD Display


Review Question


Image Display

• Critical Image Parameters

– image features • contrast, brightness, resolution, noise, uniformity, focus, dynamic range,

color display, etc.

– monitor features • screen size, pixels, contrast ratio, dot pitch, number of images per

monitor screen 3x3, 4x4, text display

– patient information • labeling, look-up tables (e.g. age-dating, etc.), anatomic orientation,

patient history, dx, etc.

– transmission parameters • compression mode, bandwidth, etc.


Review Question


Image Display


Image Processing

Edge Sharpening Both Contrast Enhanced


Image Display Calibration

• Luminance

• Contrast

• Display look-up function

• Replicate original equipment display


Hardcopy Devices

• Multiformat video camera


Hardcopy Devices

• Laser multiformat camera


PACS Summary


PACS Quality Control

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