1. High-Speed Data Acquisition Electronics for a PEM Scanner
The ClearPEM Project
Pedro Lousã
(on behalf of the ClearPEM Consortium)
16th IEEE NPSS Real Time Conference 2009
Beijing
May 12th, 2009

2. Breast Cancer Breast Cancer Mammography
Most common type of cancer among women
Second deadliest cancer
One out of 9 women develop a form of breast cancer throughout her life
Mammography
Advantages
Low cost
Good sensivity/specificity
Disadvantages
Based in structural tissue changes
Less reliable in dense breasts
High false-positive rates 2

3. P.E.T. (Positron Emission Tomography)
Based on the decay of a positron emitting radionuclide (tracer)
18F-FDG most commonly used radiotracer
Based on histological and metabolical changes of the tissue
PET vs. Mammography
Advantages
Not dependent on tissue density
Very good sensivity
Disadvantages
More expensive
Low sensivity for small lesions (WB-PET) 3

4. The ClearPEM Project Goal Framework Status
High performance scanner, to approach the limits allowed by tracer physiology
Framework
Project developed in the framework of the Crystal Clear Collaboration, CERN
Funded by the Portuguese Innovation Agency (AdI)
4.5 M€ investiment
6 years development
Status
IP licensend to PETsys, SA
Scanner ready for clinical trials 4

5. The ClearPEM Project Requirements High counting sensitivity
Detector capable of image resolution of 1 mm
Detector capable to sustain a large flux of single photons (up to 10 MHz)
On-line coincidence trigger with few ns resolution
No data acquisition dead-time (up to 1 M coincidence events/s)
Measurement of individual hits of Compton events in the detector
Movable and compact dual-head detector plates with large active area
No parallax effect 5

6. Fluorine-18 Fluordeoxyglucose (FDG)
Concept
Radiotracer
18F-FDG - Fluordeoxyglucose
Scintillating Crystals
LYSO:Ce
Avalanche Photodiodes (APD)
Hamamatsu S8550
Electronic Detector
Custom developed ASIC
Fluorine-18 Fluordeoxyglucose (FDG) 6

7. System Architecture
FrontEnd Subsystem
DAE Subsystem 7

8. Detector Technology Crystals APDs Detector Plates Material: LYSO:Ce
Density: 7.4g.cm-3
Emission Peak: 420nm
Light Yield: photons/MeV
Time Constant: 40ns
Geometry: 2x2x20 mm3
APDs
Operating Voltage: V
Dark Current: ≤10nA
Gain uniformity (sub-array): ±15%
Detector Plates
6144 crystals
12288 readout channels
160x180 mm2 surface area
Front-back readout for DoI measurement 8

9. Frontend ASIC Characteristics Technology: CMOS 0.35μm Area: 70mm2
Input: 192 channels
Output: 2 highest channels
Max Input Charge: 90 fC
Noise: ENC ~ 1300 e-
Shaping: 40ns
Analog Memories: 10 samples
Clock Frequency: MHz
Power: 3.6 mW/channel 9

10. Frontend (FE) Electronics
Frontend Board
Processes 384 APD channels
Contains 2 ASICs for signal selection
2 High-speed ADCs (10bit, 100MHz)
1 LVDS transmitter (600Mbps)
Supermodule
Comprises 2 FE Boards
Processes 768 APD channels
Detector Plate
Comprises 8 Supermodules
Processes 6144 APD channels
Contains one Service Board to control 192 high-voltage lines as well as power supply, clock distribution, temperature monitoring and threshold settings 10

11. FE Electronics Performance
Pulse Shape
Amplifier response rise time: 20ns
Variation in baseline <0.5%
Noise
ENC = 1300 e- r.m.s.
Inter-channel dispersion ~ 8%
(2.2 ADC Counts = 5keV)
(Noise measurements obtained with full electronics chain) 11

12. Data Acquisition Electronics (DAE)
DAE Crate System
DAE housed in a single 19” rack crate
Uses two cPCI backplanes
1 TGR/DCC Board
4 DAQ Boards
FE - DAE bandwidth up to 19.2Gbps
Sophisticated coincidence trigger (36k calibration constants)
DAE-Acq Server bandwidth up to 6.4Gbps 12

13. Data Acquisition Electronics (DAE)
DAQ Board (Slave)
Check Signal’s Integrity
Calculate Basic Signal’s Parameters
Signal’s Classification
Send Relevant Data to TGR/DCC Board
Built on two 4-million gate Virtex-II FPGA
System composed by 4 boards 13

14. Data Acquisition Electronics (DAE)
TRG/DCC Board (Master)
DAQ Boards’ Arbitration
Data Concentration
Find Coincidences
Sends Relevant Data to Acq Server
Control Circuit Gateway
System’s Synch and Reset
Relies on a 3-million gate Virtex-II FPGA
S-Link bridge to Acq Server 14

15. Data Acquisition Electronics Performance
Trigger Performance
Events in coincidence up to 4.5MHz
(This involves computation of energy and time as well as Compton grouping and transmission to the trigger processor)
Acquisition rate up to 0.8MHz
(This involves readout of the event dataframe after the issueing of a trigger)
Disk storage > 300MBps 15

16. Simulations Simulation Model NURBS CArdiac Torso (NCAT) Phantom
Detector detailed description
Standard injection of 10mCi (370MBq)
Background tissue SUV: 2.12kBq/ml
Lesions SUV:
(4:1) 8.5kBq/ml
(5:1) 10.5kBq/ml
Exam Duration: 5 minutes
W. P. Segars,"Development of a new dynamic NURBS-based cardiac-torso (NCAT) phantom", PhD dissertation, The University of North Carolina, May 2001 16

17. Simulations 17

18. ClearPEM Images Image Setup Results 1mm 22Na source
Grid with 5mm pitch
Two acquisitions with orthogonal plate orientations for each source location ( keV)
Reconstruction of 16 source positions
Results
Horizontal FWHM: 1.3mm
Vertical FWHM: 1.2mm
OSEM-2D
OSEM-3D 18

19. Clinical Trials Phase 1 Phase 2
Tuning the image reconstruction with real cases
Phase 2
Assessment of PEM sensitivity / specificity
Comparison to mammography, MRI, WB-PET 19

20. Conclusions
ClearPEM technological developments were successfully completed
Excellent detector performance
ClearPEM electronics is one of the most innovative systems available for APD-based PET systems
Next steps: scanner characterization and clinical tests 20

21. Thank you! 谢 大 家
Pedro Lousã
ClearPEM Consortium
RT 2009 Conference