THE 12 TH VIENNA CONFERENCE ON INSTRUMENTATION 15-20 FEV 2010 The ClearPEM Breast Imaging Scanner...

THE 12TH VIENNA CONFERENCE ON INSTRUMENTATION

15-20 FEV 2010

The ClearPEM Breast Imaging Scanner

LIP - LABORATORY OF INSTRUMENTATION AND EXPERIMENTAL PARTICLE PHYSICSLisbon, PORTUGAL

Jorge A. NEVESon behalf of the ClearPEM Collaboration

PEMCollaboration

Motivation

Breast Cancer and Positron Emission Tomography

01

10

11 npν

γ 511keVγ 511keV e+ e-

Breast cancer is the most common cancer among women mean incidence rate of 1.2 million females per year worldwide

PET is a functional imaging technique that has demonstrated large potential for breast cancer detection - Positron Emission Mammography (PEM)

The Patient is injected with 18F-FDG radiotracer that fix in tumor cells and decays by

positron emission. The 2 γ photons resulting by the positron-electron annihilation

are detected in temporal coincidence to imaging the biodistribution of the

radiotracer.

The ClearPEM Breast Imaging Scanner Jorge A. NEVES

THE 12TH VIENNA CONFERENCE ON INSTRUMENTATION 15-20 FEV 20102/18

The ClearPEM Scanner

Detector Calibration

Energy and Time Resolution

Image Reconstruction

Conclusions

Outline




Good Spatial Resolution (~1.5 mm FWHM) Fine crystal segmentation (2 x 2 mm) Dual APD readout of crystal pixels Depth-of-Interaction measurements

with a resolution of ~2 mm FWHM

High Detection Sensitivity Long LYSO:Ce crystal (20 mm) Two detector plates with large active area

(16 x 18 cm2 FOV)

Reduced Random Background (~30%) Large flux of single photons (up to 10 MHz) Coincidence time resolution of ~4 ns FWHM

for background rejection


The ClearPEM Characteristics



ClearPEM MOVIE





The ClearPEM Detector ModulesTwo Detector Plates

160 x 180 mm2 active area

6144 scintillation crystals LYSO:Ce (emit visible light when high energy photons interact with them)

12288 APD pixel channels ( Highly sensible photo-detector. Generate pulses in response to scintilation light)

Double readout of crystal pixels for Depth-of-Interaction measurent (to minimize parallax effect)

Water cooling system (18.0 ± 0.1 °C)

Hamamatsu S8550 Avalanche PhotoDiode

LYSO:Ce 2x2x20 mm3 crystal

4x8 crystal matrices

384 APD arrays, Operating Voltage 350-450V

ε ~ 82% @ 511 keV

7.4 g.cm-3



BaSO4 walls


FrontEnd ASICCharge Amplifier Characteristics

Technology: AMS 0.35 μm CMOS, 70 mm2 Area

Input: 192 channels

Output: 2 highest channels (192:2 mux)

-> to readout Compton events Max Input Charge: 90 fC Noise: ENC ~1300 e-

(Baseline RMS = 2.2 ADC counts = 5 keV)

Shaping: 40 ns

Analog Memories: 10 pulse samples

Clock Frequency: 50-100 MHz

Power: 3.6 mW/channel



12 cm

4.5 cm

ASICs (2x192 channels)

FrontEnd Board

Modules (12x32 crystals, 24 APDs)

HV matrix

Service Board

Super Module 2 FrontEnd Boards and 12 Detector Modules

Processes 768 APD channels

FrontEnd Board Contains 2 ASICs for APD signal readout 2 High-speed dual ADCs (10bits, 100 MHz) 1 LVDS Channel Link Transmitter (2.4 Gbps)

Detector Head 8 Super Modules (16

for both DHs) 1 Service Board for HV & LV

distribution, T(°C) monitoring water cooling plates


FrontEnd Electronics

192 Detector Modules




Off-Detector and Data Acquisition Electronics19’’ crate

2cPCI backplanes



Data Transfer Bandwidth6.4 Gbps Trigger/DCC Acquisition Server

800 MBps (520) @ S-Link FedKit (PCI)

60 MBps (42) @ USB 2.0

400 MBps Storage Rate

Coincidence Triggering Rate 800 kHz

DAE System – L1 Trigger/DAQ4 DAQ Boards (Slave)

8 XlinxTM FPGA First data filtering to identify usefull data

(find Top-Bottom crystal coincidences) Check signal integrity calculating basic parameters Send relevant data to TGR/DCC Board

1 TGR/DCC – Trigger & Data Concentrator Board (Master) 1 XilinxTM FPGA DAQ Board’s arbitration System’s Sync and Reset Responsible for the identification of

coincidence between detector heads Sends relevant data to Acquisition

Server (S-Link Bridge)


Scanner Integration @ IPO

Portuguese Institute of Oncology - Porto

Examination BedDetector Heads

Robotic structure



511 keV

APD pixel

APD pixel

LYSO:Ce Crystal

Relative Gain

Distributio

n of Energ

y Calib

rations C

onstants

3 Calibration constants per crystal (Top and Bottom readout)

Detector Calibration

Absolute Gain

Distribution of pulse peak timeRequires > 4%/mm for DOI resolution < 2 mm FWHM

DOI Calibration



Tmax

Tpeak

Photon time is extracted from the pulse samples fitted by the function:


Time Measurements

Typical pulse 50 MHz sampling

The coincidence time resolution of the whole scanner is 5.2 ns FWHM



Time C

alibratio

n


Energy MeasurementsAverage energy resolution at 511 keV for the

full scanner is 16.0 %

22Na spectra for all crystals

Photopeak measurements

511 keV photopeakcompton

Good energy linearity Energy resolution and photopeak position not dependent of DOI



Without DOI Information

With DOI Information

1.2 mm FWHM


ClearPEM Spatial ResolutionPoint Source Imaging

22Na point source in a grid with 5 mm pitch

Energy window 400 - 600 keV

Sinograms of 16 source positions are added

3D-OSEM/STIR Reconstruction

Spatial Resolution Transaxial 1.2 mm FWHM

(corrected by source size ~ 1 mm)

DOI Effect Images without using DOI information

show considerable blurring




ClearPEM Spatial ResolutionDerenzo Phantom Imaging

Sealed phantom with 22Na gel

20 μCi activity (T1/2 = 2.6y)

Active area: 35 mm Ø x 38.1 mm length

Phantom Draw

3.0 mm

2.5 mm

2.0 mm

1.5 mm

1.2 mm

Dist. = 150 mmTakes = 4 x 20 min

450-600 keV energy window6 ns time window

3.0 mm

2.5 mm

2.0 mm

1.5 mm

1.2 mm

3996 0

3D-OSEM




Initial Clinical TestsExample os a typical exam

dose 7.6 mCi 150 mm detector plate opening 4 angular orientations coincidence windom ± 4 ns energy window 400 - 650 keV low coincidences rate ~1.2 kHz fraction of randoms in FoV IS 35%

Reconstruction 3D-OSEM simple normalization correction randoms, attenuation and scatter correction not applied 22Na source data added to sinogram, emulating lesion (L/B~4 for 3 mm lesion)



Conclusions



ClearPEM electronics is one of the most innovative

systems available for APD-based PET systems

Excellent detector performance

Time Resolution: 5.2 ns FWHM

Energy Resolution: 16 %

Spatial Resolution: 1.2 mm FWHM

Initial clinical trials have been started

Needs and efforts on image corrections

ClearPEM-Sonic



E. Albuquerque1, F. G. Almeida2,13, P. Almeida3, E. Auffray10, J. Barbosa2, A. L. Bastos9, V. Bexiga1, R. Bugalho4, C. Cardoso4, S. Carmona8, J.F. Carneiro2, B. Carriço4, C. S. Ferreira4, N. C. Ferreira5, M. Ferreira4, M. Frade4, F. Gonçalves1, C. Guerreiro5, P. Lecoq10, C. Leong1, P. Lousã6, P. Machado1, M. V. Martins3, M. C. Martins6, N. Matela3, R. Moura4, J.A.Neves4, P. Neves6, N. Oliveira3, C. Ortigão4, F. Piedade6, J. F. Pinheiro4, P. Relvas6, A. Rivetti10 , P. Rodrigues4, I. Rolo4, M. Rolo4, A. I. Santos8, J. Santos2, M. M. Silva1, S. Tavernier11, I. C. Teixeira1,9, J. P. Teixeira1,9, J. C. Silva4,10, R. Silva4, A. Trindade4, J. Varela4, 10

1 INESC-ID, 2 INEGI, 3 IBEB/FCUL, 4 LIP, 5 IBILI/FMUC, 6 INOV, 8 HGO, 9 IPO, 10CERN, 11VUB

Funded bySFRH/BD/33667/2009

Acknowledgments

Thank you!

THE 12 TH VIENNA CONFERENCE ON INSTRUMENTATION 15-20 FEV 2010 The ClearPEM Breast Imaging Scanner...

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