EXACTTM CT Scanner

EXACT: The heart of an FAA-certified Explosives Detection Scanner

3-D Image

System Block Diagram

Automatic Explosives Detection4 processors

3D Image Display

Image Reconstruction1.5 GOp/s, 50 processors

Helical Cone Beam Data

X-ray CT scanner

Reconstruction Engine Requirements

Nutating SliceImage Reconstruction

1.5 GOp/s

Dual-energyHelical Cone-beam data

Control and Status (RS232)

Images (SCSI)

6064 samples/view1080 views/s

450 3D bags /hr 90 2D slices/s

Reconstruction Algorithm

• Nutating Slice Reconstruction

• Prerequisite: cone beam data corrected for detector imperfections

Nutating Slice Reconstruction

HELICAL CONE-BEAM

SKYpack* Computer

• Application-specific repackaging of standard 6U VME product– originally developed for DARPA SAST

program

• Dual use in commercial applications– explosives detection– medical CT image reconstruction*SKY Computers, Chelmsford, MA

SKYpack Components

• 1 RISC processor for I/O control• 12 RISC processors for compute

processing– Labeled AP0-11 in diagram

• 6 SHARC processors• 6 ASIC processors• Shared Bus: SKYchannel

SKYpack Partitioning

• High and low energy images reconstructed on different SKYpacks

• Processes are data driven and asynchronous

Processor Memory

AP 264 MB

4 MB

Platform 0

Platform 1

Platform 2

SKY-CT

ControlProcessor

SKYchannel

SKYpack

RS232

SKYburst

Data Entry Point

SCSI

64 MB

64 MB

AP 3

AP 1

AP 0

AP 4

AP 5

AP 6

AP 7

AP 8

AP 9

AP 10

AP 11

SHARCS

ASICS

4 MB

SKYpack Partitioning

AP 0o/p0 SHARC 0

AP 7

AP 8

AP 9o/p21

i/p

i/p

i/o0

i/o1

RS232

CorrectionCone FanFan Hybrid

Hybrid Parallel Filtering

InputData

SHARC 5

SKYpack Partitioning cont’d

ASIC 0

ASIC 5

L Video Memory

AP 10 AP 11

R Video

Memory

i/p

i/o 0

i/o13

o/p0

o/p249

Backprojection

Untilt

Image FormattingAnd Transfer (SCSI)

SKYpack Partitioning• System processor distributes cone

beam data to AP 0-7• AP 0 does RS232 communication and

controls other processors• AP 0-7 correct and convert cone to

hybrid data• Each cone view contributes to 22

slices, every 12th view a new slice is created

SKYpack Partitioning• AP 8-9 convert hybrid data to parallel • SHARCs high pass filter parallel data

using FFT• ASICs backproject filtered data into

tilted slices• AP 10 untilts tilted slices into parallel• AP 11 formats images and carries out

SCSI communication

Verification and Validation

• Offline, single process software was implemented

• Simulations to verify offline software

• Intermediate results from offline software matched with online software

Automatic Detection Subsystem

• Consists of four processors• Does image analysis, archiving and

display• Image data is propagated along two

paths that search for two classes of explosives

• Each path uses detection and discrimination algorithms

References• “Nutating Slices CT Image

Reconstruction Apparatus and Method” United States Patent: 5,802,134, September 1998

• “Parallel Processing Architecture for Computed Tomography Scanning System using Non-Parallel Slices” United States Patent: 5,887,047, March 23, 1999

• “Computed Tomography Apparatus and Method for Classifying Objects” United States Patent: 6,317,508, November 13, 2001