PIERS, Hawaii, Oct. 14 2003

Second Generation Microwave Imaging System: Phantom and Early Clinical

Experience

Paul M. Meaney, Dun Li, Qianqian Fang, Sarah A. Pendergrass, Margaret W.

Fanning, Keith D. Paulsen

THAYERSCHOOL OF

ENGINEERINGD A R T M O U T H C O L L E G E

THAYERSCHOOL OF

ENGINEERINGD A R T M O U T H C O L L E G E

PIERS, Hawaii, Oct. 14 2003

Outline

• Difficulties• Overview of 2nd Generation

MIS• Advances of Hardware• Advances of Algorithms• Phantom and Clinical Test• Future works

PIERS, Hawaii, Oct. 14 2003

First Generation Prototype

Operating from 300 MHz to 1 GHz

Sequentially Collecting data at 16 trans x 9 rec. sites

PIERS, Hawaii, Oct. 14 2003

Challenges

• Difficulties in 1G Microwave Imaging System– high attenuation of coupling medium

(saline)– limited measurement data (only up to

1GHz)– electronics efficiency (serial detection)– positioning (manually)– reconstruction efficiency

PIERS, Hawaii, Oct. 14 2003

Overview of 2nd Generation

MIS• Main Features

1. Parallel detection scheme2. Broad operating band (WB source,

components and connectors)3. Automated positioning4. Low contrast adjustable coupling

medium5. Efficient reconstruction algorithms6. Streamlined DAQ and data processing

PIERS, Hawaii, Oct. 14 2003

Comparisons

• Performance MatrixOld System New System

Receivers 9 15Operating Frequency

300MHz~1GHz 500MHz~3GHz

Detection Mode serial parallel

DAQ Speed 16 x 9 x 12 x 7 =12,096

12.5 min16 x 15 x 20 x 7 =33,600

10 minPositioning manual automatic

Coupling medium

Saline Glycerin/Water mixture

PIERS, Hawaii, Oct. 14 2003

Clinical Interface

Patient Bed

Electronics

Illumination

Tank

Linear

Actuator

Control

Terminal

Antenna

Array

Fluid

Managemen

t

System

PIERS, Hawaii, Oct. 14 2003

Operation Animation

FMS Patient Bed

Reservoir

SterilizerMotor

1, 1

2

, 2

PIERS, Hawaii, Oct. 14 2003

Electronics Design

PIERS, Hawaii, Oct. 14 2003

Coupling medium

• Benefits of Glycerin/Water mixture– Low attenuation– Adjustable dielectric properties– Better matching with breast tissue– Safe

PIERS, Hawaii, Oct. 14 2003

Measured Properties

Re

lati

vePer

mitt

ivit

y

(/

)Co

nduc

tivi

tyS

m

PIERS, Hawaii, Oct. 14 2003

High Frequency Measurement

Crosstalk between transeiver

channels

Amplitude response and phase error

vs. input signal power

PIERS, Hawaii, Oct. 14 2003

Reconstruction Framework

• 2D imaging (3D in developing,3D/2D,3D/3D)

• Iterative Gauss-Newton reconstruction• Freq.-Domain/Time-Domain forward

solvers• High frequency data implementation• Flexible regularization strategies• Simultaneous multiple-frequency

measurement synthesis

PIERS, Hawaii, Oct. 14 2003

Algorithm Optimization

• Adjoint method (building Jacobian matrix)

• Dual-mesh (reducing problem size)

• Log-Magnitude Phase-Unwrapping• 2 step reconstruction and conformal

mesh technique (enhancing image quality)

• Spatial filter (stabilizing reconstruction)

• Pre-scaled system (fine tuning)

PIERS, Hawaii, Oct. 14 2003

Adjoint method for dual-mesh

• Jacobian Matrix - Sensitivity

Receiver

JsSource

Only Matrix-vector multiplications are

needed, geometric related sparse matrix

can be build independent of

reconstruction

,2

1, , ( )( , , )

ˆ,s r

n

i j n s r

s r ni j n sr r

r rr

r rk

J rff j d

ff j

-ì -ïïï=¶

¶= íï -ïïî

A E

E E

Er r

r

rr r r

PIERS, Hawaii, Oct. 14 2003

Two-stage Regularization

• Switching from L-M to Tikhonov Reg. with a priori estimates

Step 1

Step 2

0 5 10 15 20 25 300

0.1

0.2

0.3

0.4

0.5

iteration

rel.

erro

r

2

2

11

min { }

( )

meas calc

T Tk k k

E E

x x J J I J bl -+

-

= - +

2 222

min { ( *) }meas calcE E L x xr- + -

PIERS, Hawaii, Oct. 14 2003

Phantom Experiment & Results

• Phantom

Corn syrup phantom

Diameter: 10cm

Inclusion: saline

Inclusion diameter: 3cm

PIERS, Hawaii, Oct. 14 2003

Clinical Data

• Patient 1082, Age: 68, AP: 14cm

1 2

Left Breast Right Breast1100MHz/2stage/conformal

PIERS, Hawaii, Oct. 14 2003

Future works

• 3D data acquisition and reconstruction• Multiple spectrum data analysis• Faster forward/recon algorithm

->Real time• MRI data validation• System optimizations (optimal

frequency(ies), transeiver num., spatial configurations, backgrd. contrast etc )

PIERS, Hawaii, Oct. 14 2003

Questions?

PIERS, Hawaii, Oct. 14 2003

Conformal Mesh

• Shirking the reconstructed unknown close to object based on scout images

Saline inclusion

Conformed domain & Imaging object

Monopole antenna

FE / BE region interface

FE / BE region interface

Concentric FE mesh Saline inclusion

Imaging object

Monopole antenna array