VOICE OF THE ENGINEER - ElectronicsAndBooks

More documents

Recommendations

Info

SENSORSORARRAYRAYADCMULTI-CHANNELADCADCMULTI-CHANNELADCFPGADATA-ACQUISITION ACQUISITION SUBSYSTEMSLIP RINGMULTI-PLEXERBUFFERSERIALIZER/DESERIALIZERDATA-AGGREGATION CARDCUSTOMNETWORK-INTERFACECARDIMAGERECONSTRUCTIONCPUCUSTOMRAIDCONTROLLERFigure 3 In a CT-image-reconstruction workstation, customized network-interface cards terminate custom protocols, and customRAID controllers buffer the raw data at high rates until the system can reconstruct the image.RAID(a)Figure 4 A cranial image (a) is indistinguishable from the reconstructedimage (b) after 3-to-1 data compression.(b)sec and 16 bits/sample. The aggregate throughput requirementis 1280 Mbytes/sec, a rate that exceeds the throughputof commercially available RAID controllers, which topout at 800 Mbytes/sec. CT-signal compression can reducethe throughput requirement of RAID controllers. For example,GE Healthcare (www.gehealthcare.com), SamplifySystems (www.samplify.com), and Stanford University(www.stanford.edu) have demonstrated the efficacy of signalcompression in both lossless and nearly lossless modesto achieve compression ratios that provide compelling reductionsof 3-to-1 or even 4-to-1 in data-acquisition rates(Reference 1).Figure 4 shows an original image and a sample image of3-to-1 compressed data. For more than 400 images, a Stanfordradiologist could not distinguish the image of compressedsamples from the image of noncompressed samples.With signal compression on the rotor side of the slip ringand decompression in software on the workstation, the CTsystem realizes the benefit of bit-rate reduction across theentire signal chain, including the slip ring, the network-interfacecard, and the RAID controller. Integration of signalcompression into CT slip rings makes the compression transparentto the rest of the CT system so that such compressingslip rings can be drop-in replacements for older slip rings.In CT machines, image reconstruction typically occursthree to 10 times slower than does CT data acquisition. Thisasymmetry creates the need for RAIDs in the system to bufferthe raw data until the CT machine can reconstruct it intoan image. Because the RAID is the last link in the data-acquisitionchain, CT-machine designers must build theworkstation on the CT gantry by considering data-acquisitionrates instead of image-reconstruction rates. A new architecturehelps designers build CT workstations based onthe lower image-reconstruction rates rather than the higherdata-acquisition rates (Figure 5).With compression of the X-ray-detector data in the slipring, you can now replace a custom multilane fiber-optic interfacewith a standard storage interface, such as FibreChannelor InfiniBand. This approach allows you to use off-theshelfRAIDs outside the workstation. In this architecture,an off-the-shelf FibreChannel or InfiniBand switch providesthe connectivity between the gantry or the data-acquisitionsubsystem, storage subsystem, and workstation. The workstationcan now use standard low-cost network-interface cardsrather than the customized interfaces that today’sgantry-to-console connectors use.Furthermore, because image-reconstructionrates are several times lower than data-acquisitionrates, designers can build decompression into theRAID, enabling the integration of compressioninto CT systems in a manner that is transparent toimage-reconstruction software. With the eliminationof the need for a RAID or its transition intothe gantry, the designer can now base the workstationon commodity PC-server hardware.With R&D budgets tightening, medical-imagingOEMs must deliver next-generation technologiesacross a wider range of market segments withlower development costs. This move requires themto rationalize technologies that target the competitiveadvantages of their machines.EDN40 EDN | FEBRUARY 3, 2011
SENSORSORARRAYRAYADCMULTI-CHANNELADCADCMULTI-CHANNELADCFPGADATA-ACQUISITION ACQUISITION SUBSYSTEMSLIP RINGMULTI-PLEXERBUFFERSERIALIZER/DESERIALIZERDATA-AGGREGATION CARDFIBRE-CHANNELSWITCHRAIDCONTROLLERFIBRE-CHANNEL-NETWORK-INTERFACECARDIMAGERECONSTRUCTIONCPUCOMPRESSINGRAIDFigure 5 A new architecture for CT workstations puts compression of the X-ray-detector data into the slip ring, so that you canreplace custom multilane fiber-optic interfaces with a standard storage interface, allowing the use of off-the-shelf RAIDs.REFERENCE1 Wegener, Albert; Naveen Chandra; Yi Ling; Robert Senzig;and Robert Herfkens, “Real-time compression of raw computedtomography data: technology, architecture, and benefits,”Proceedings of the SPIE Medical Imaging Conference,Volume 7258, pg 7258H, March 2009, www.samplify.com/ct.AUTHOR’S BIOGRAPHYAllan Evans is vice president of marketing at Samplify SystemsInc (Santa Clara, CA), a provider of signal-compression andbeam-forming technology for the medical-imaging market. Heholds a master’s degree in electrical engineering from the Universityof California—San Diego and a master’s degree in businessadministration from Santa Clara University (Santa Clara, CA).FEBRUARY 3, 2011 | EDN 41
Page 1 and 2: VOICE OF THE ENGINEERFEB3Issue 3/20
Page 3 and 4: VOICE OF THE ENGINEERFEB3Issue 3/20
Page 7 and 8: 2.3.11contentsAdvances inenergy-sto
Page 9 and 10: contents2.3.11Simpler PowerConversi
Page 11 and 12: ASSOCIATE PUBLISHER,EDN WORLDWIDEJu
Page 13 and 14: Analog Devices: enabling the design
Page 15 and 16: Class D amplifier suppresses EMISil
Page 17 and 18: SIGNAL INTEGRITYBY HOWARD JOHNSON,
Page 19 and 20: with more sophistication. The boot
Page 21 and 22: loop) to achieve clock locking befo
Page 23 and 24: CLOCKRESETCONFIGURATIONSERIALBOOTLO
Page 25 and 26: EXTERNALNAND MEMORYOPERATING-SYSTEM
Page 27 and 28: ENERGY HARVESTING RELIES ONINTERMIT
Page 29 and 30: Have you heard?Oscilloscopes fromth
Page 32 and 33: POWER CONSTRAINTS OF WIRELESS SENSO
Page 34 and 35: Your Project Acceleration Resource
Page 36 and 37: BY ALLAN EVANS • SAMPLIFY SYSTEMS
Page 38 and 39: The voltage required across the sup
Page 42 and 43: 5A LDO for Digital ICs85mVDropoutVo
Page 45 and 46: Get an edge: laser driversPhoto Cou
Page 47 and 48: YOU CAN IMPROVETHE CIRCUIT BYREPLAC
Page 49 and 50: or even destroy a power supply’s
Page 51 and 52: IntroducingEDN’s NewMicrosite on
Page 53 and 54: ADVERTISER INDEXCompany Page Compan
Page 55 and 56: www.globalfoundries.com/mwc

VOICE OF THE ENGINEER - ElectronicsAndBooks

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?