Charge division readout for SensL SPMArray4 modules (last update October 10, 2011)

CENTER FOR ADVANCED IMAGINGCENTER FOR ADVANCED IMAGINGAT WEST VIRGINIA UNIVERSITYAT WEST VIRGINIA UNIVERSITY

Charge division readout for SensL SPMArray4 modules

(last update October 10, 2011)Motivation:CompactnessHigher MRI-compatibilityCost

Approach: Develop multiplexing readout schemes minimizing the number of readout channels, while maintaining high performance (primarily spatial resolution).

First stage: definition of the performance limits using “resistive” readout (4ch per module), including DOI operation

Second stage: develop row & column readout = 24 channels


ADC Gate ~125nsADC Gate ~125ns

40ns/div40ns/div

SPMArray4 4ch readout

The SPMArray4 module from SensL equipped with resistive 4ch readout from AiT Instruments. The output channels integrated and digitized in the AiT Instruments FPGA DAQ module (not shown).


1.5mm LYSO array

2.8mm window2.8mm window15% FWHM15% FWHM

15.0% FWHM15.0% FWHM@511 keV@511 keV

15.4% FWHM15.4% FWHM@511 keV@511 keV

1274 kev/511 kev ratio = 2.51 vs 2.49 expected1274 kev/511 kev ratio = 2.51 vs 2.49 expected

Raw images, and a profile through one pixel raw, at 511 keV, and examples of energy spectra for a 1.5mm step 10mm thick LYSO array.



1.0mm LYSO array

2.8mm window2.8mm window 1.5mm window1.5mm window

14.7% FWHM14.7% FWHM14.7% FWHM14.7% FWHM@511 keV@511 keV

13.7% FWHM13.7% FWHM@511 keV@511 keV

Raw images, and a profile through one pixel raw, at 511 keV, and examples of energy spectra for a 1mm step 10mm thick LYSO array.



The SiPM based photomultipliers are in principle much more compact than standard PMTs, when implemented with compact electronics. At right is the H8500 flat panel PMT from Hamamatsu with four channel resistive readout. In the center is the Matrix9 module from SensL with all-digital pixel readout of all 144 3mm pixels. At left and at top right is the Array4p9 module from SensL with AiT Instruments resistive 4ch readout. The four output channels (scope picture of one is shown, as well as of the sum signal) are integrated and digitized in the AiT Instruments FPGA DAQ module (not shown).

Array4p9 – a compact ~2” PM

H8500

Array4p9 1 channel

Sum of four

50ns50ns

Array4p9


Image at 511 keV and selected pixel energy spectra, at 81.1 deg F. 22Na source. Proteus LYSO array of 28x28 1.51 x 1.51 x10mm pixels (1.59 mm pitch) was coupled to the Array4p9 module through a 2mm thick acrylic spreader window. Optical coupling grease (Visilox V-788) was applied to all optical surfaces (wet coupling).

15.6% 15.6% @511 keV@511 keVFWHMFWHM

16.5% 16.5% @511 keV@511 keVFWHMFWHM

16.5% 16.5% @511 keV@511 keVFWHMFWHM

15.5% 15.5% @511 keV@511 keVFWHMFWHM

16.2% 16.2% @511 keV@511 keVFWHMFWHM

81.1 F

1.5mm LYSO array


Raw image and a profile at 511 keV through one pixel raw, at 42.3 deg F. 22Na source. Proteus LYSO array of 28x28 1.51 x 1.51 x10mm pixels (1.59 mm pitch) was coupled to the Array4p9 module through a 2mm thick acrylic spreader window. Wet coupling. Pixel energy resolution @511 keV measured from 14.5 to 16.8% FWHM, depending on the position of the LYSO pixel in the SiPM array. (Amplitude at this temperature was about 1.6 higher than that at 81.1 deg F, when measured at the same bias voltage.)

43.2 F

1.5mm LYSO array


Raw images obtained for 1274 keV and 511 keV photopeaks at room temperature (~ 74 deg F) using the second SiPM module and slightly modified readout circuitry. 22Na source. Proteus LYSO array of 28x28 1.51 x 1.51 x 10mm pixels (1.59 mm pitch) was coupled to the Array4p9 module through a 2.15mm thick acrylic spreader window. A comparative measurement was done with the H8500 flat panel PMT using the same LYSO array. Wet coupling. The image at 1274 keV can be used to provide better definition of the crystal map, especially at the edges of the module.

1274 keV

511 keV

511 keV

H8500

Array4p9

~74 F

1.5mm LYSO array


Raw images obtained for 1274 keV and 511 keV photopeaks at 43.2 deg F using the first SiPM module. 22Na source. Proteus LYSO array of 1.51 x 1.51 x 10mm pixels (1.59 mm pitch) coupled through a 2.15mm thick acrylic spreader window. Wet coupling.

1274 keV

511 keV

43.2 F

1.5mm LYSO array


Raw image obtained after final re-optimization at 511 keV and at ~75 deg F. 22Na source. Proteus LYSO array of 1.51 x 1.51 x 10mm pixels (1.59 mm pitch) coupled through a 2.15mm thick acrylic spreader window. Wet coupling.

~75 F

511 keV

1.5mm LYSO array


Raw images at 511 keV and 1274 keV and energy spectra for selected LYSO pixels as well as normalized energy for the full detector at 43.2 deg F. 22Na source. Proteus LYSO array of 2.0 x 2.0 x 15mm pixels (2.0 mm pitch) coupled through a 2.15mm thick acrylic spreader window. Wet coupling.

43.2 F

511 keV

1274 keV

2mm LYSO array

17.7% FWHM 17.7% FWHM @511 keV@511 keV

Ratio: 2.53Ratio: 2.53

Normalized energy for the full detector.

17.6% 17.6% FWHM FWHM

16.0% 16.0% FWHM FWHM

15.8% 15.8% FWHM FWHM

16.4% 16.4% FWHM FWHM


Raw images at 511 keV and 1274 keV and energy spectra for the four selected LYSO pixels at 80 deg F using the first SiPM module. 22Na source. Proteus LYSO array of 2.0 x 2.0 x 15mm pixels (2.0 mm pitch) coupled through a 2.15mm thick acrylic spreader window. Wet coupling.

80 F

511 keV

1274 keV

2mm LYSO array array array

18.5% 18.5% FWHM FWHM

17.5% 17.5% FWHM FWHM

19.2% 19.2% FWHM FWHM

16.1% 16.1% FWHM FWHM


Two identical Array4p9 modules with 4ch charge division readout from AiT Instruments were coupled from both ends of a 10x10 1.5mm step 15 mm thick LYSO array from Proteus optimized for DOI operation. Room temperature. Wet coupling through 2mm thick spreader windows. Bias voltages: 29.2 and 29.6 Volt. ADC integration gate: 100 nsec.

511 keV energy window

All results for one selected

1.5mm LYSO pixel and broad 511 keV gamma beam from

22Na.

14.2%14.2%FWHM FWHM

Out_2

Out_1

Out_1

Out_2

Sum DOI=Out_1/Sum

20%

80%

Left: Raw image at 511 keV with row projection and energy spectra for the selected LYSO pixel. Both outputs were combined to form ONE image, showing good separation of individual 1.5mm pixels. Both individual energy spectra are broad, as expected, due to the DOI feature of the scintillator array.


All results for one selected

1.5mm LYSO pixel and

narrow collimated 511 keV

gamma beam from a

<1mm 22Na source.

DOI=Out_1/Sum

Left: DOI results at 511 keV and energy spectra for the selected LYSO pixel and a narrow 511 keV gamma beam adjusted to be in the mid-plane of the LYSO array. To calibrate DOI spatial resolution, the beam was moved to two additional and symmetrically placed 5mm spaced positions. Measured spatial resolution includes beam size.

21.3% 21.3% FWHM FWHM

16.9% 16.9% FWHM FWHM

20.7% 20.7% FWHM FWHM

1.66mm1.66mmFWHM FWHM

Out_1

Out_2

Two identical Array4p9 modules with 4ch charge division readout from AiT Instruments were coupled from both ends of a 10x10 1.5mm step 15 mm thick LYSO array from Proteus optimized for DOI operation. Room temperature. Wet coupling through 2mm thick spreader windows. Bias voltages: 29.2 and 29.6 Volt. ADC integration gate: 100 nsec.

DOI=Out_1/Sum

5mm

Out_2

Out_1

Out_1

Out_2

Sum

20%

80%


New 4ch charge division readout from New 4ch charge division readout from AiTAiT

Operation at 70 F. Bias voltage at 28.8 Volt. ADC signal Operation at 70 F. Bias voltage at 28.8 Volt. ADC signal integration gate of 200 nsec. 1mm pitch Proteus LYSO array of integration gate of 200 nsec. 1mm pitch Proteus LYSO array of 24x24 LYSO 10mm long pixels. Only about a quarter of the 24x24 LYSO 10mm long pixels. Only about a quarter of the detector populated with the array. The corner region detector populated with the array. The corner region indicated with an arrow. Variant B offers better performance. indicated with an arrow. Variant B offers better performance.

511 keV

1274 keV

1

1

2

2

511 keV

1274 keV

Variant A

21.2% 21.2% FWHM FWHM

2.992.99

3.053.05

3.03.0

2.982.98

3.113.11

22.8% 22.8% FWHM FWHM

23.7% 23.7% FWHM FWHM

22.1% 22.1% FWHM FWHM

23.3% 23.3% FWHM FWHM

Variant B

1274/ 511 1274/ 511 keVkeVPeak ratioPeak ratio


Operation at 42 F. Operation at 42 F. Bias voltage at 29.5 Volt. ADC signal integration gate of 175 nsec. Proteus 1.0 mm pitch LYSO array of 24x24 10mm long pixels was coupled to the Array4p9 module through a 2.50 mm thick acrylic spreader window using coupling grease. Only about a quarter of the detector populated with the array.


20nsec/div

Sum pulse shapes Sum pulse shapes with the new 4ch with the new 4ch readout (Variant readout (Variant B) B)

511 keV

1274 keV

19.7% 19.7% FWHM FWHM

1274/ 511 keV peak 1274/ 511 keV peak ratioratio

2.882.88

3.473.47

2.762.76

2.882.88

2.792.79

20.8% 20.8% FWHM FWHM

17.7% 17.7% FWHM FWHM

23.4% 23.4% FWHM FWHM

28.8% 28.8% FWHM FWHM



Operation at 42 F. Operation at 42 F. Bias voltage at 29.5 Volt. ADC signal Bias voltage at 29.5 Volt. ADC signal integration gate of 175 nsec. Proteus LYSO array of 28x28 1.51 x integration gate of 175 nsec. Proteus LYSO array of 28x28 1.51 x 1.51 x 10mm pixels (1.59 mm pitch) was coupled to the Array4p9 1.51 x 10mm pixels (1.59 mm pitch) was coupled to the Array4p9 module through a 2.50 mm thick acrylic spreader window using module through a 2.50 mm thick acrylic spreader window using coupling grease. Special thresholding scheme increases the ratio coupling grease. Special thresholding scheme increases the ratio of 1274 keV peak to 511 keV peak (from the of 1274 keV peak to 511 keV peak (from the 2222Na source), as seen Na source), as seen at right. Partially this effect is compensated by electronics at right. Partially this effect is compensated by electronics saturation effects, especially in the edge regions. saturation effects, especially in the edge regions.

17.7% 17.7% FWHM FWHM

18.9% 18.9% FWHM FWHM

18.1% 18.1% FWHM FWHM

23.2% 23.2% FWHM FWHM

22.5% 22.5% FWHM FWHM

1274/1274/511 511 keVkeVPeak Peak ratioratio

2.942.94

3.043.04

2.712.71

2.542.54

XX



Operation at 72 F. Operation at 72 F. Bias voltage at 29.5 Volt. ADC signal integration gate of 175 nsec. Proteus LYSO array of 28x28 1.51 x 1.51 x 10mm pixels (1.59 mm pitch) coupled to the Array4p9 module through a 2.50 mm thick acrylic spreader window using coupling grease.

511 511 keVkeVPeak Peak ratioratio

0.7050.705

0.5640.564

1.001.00

0.980.98

21.5% 21.5% FWHMFWHM

21.5% 21.5% FWHM FWHM

18.5% 18.5% FWHM FWHM

23.4% 23.4% FWHM FWHM

22.3% 22.3% FWHM FWHM

0.9280.928


Row & Column Readout Scheme for the Row & Column Readout Scheme for the SensL Array4p9 arraySensL Array4p9 array

R/C: (12 + 12) = R/C: (12 + 12) = 24 ch./144 24 ch./144 pixelspixels

Operation at 70 F. Operation at 70 F. Bias voltage at 28.8 Volt. ADC signal Bias voltage at 28.8 Volt. ADC signal integration gate of 150 nsec. Results @ 511 keV. Proteus LYSO integration gate of 150 nsec. Results @ 511 keV. Proteus LYSO array of 28x28 1.51 x 1.51 x 10mm pixels (1.59 mm pitch) was array of 28x28 1.51 x 1.51 x 10mm pixels (1.59 mm pitch) was coupled to the Array4p9 module through a 2.50 mm thick acrylic coupled to the Array4p9 module through a 2.50 mm thick acrylic spreader window. Wet (grease) coupling.spreader window. Wet (grease) coupling.

19.4% 19.4% FWHM FWHM

2.642.64

2.602.60

2.602.60

2.682.68

20.8% 20.8% FWHM FWHM

20.5% 20.5% FWHM FWHM

19.1% 19.1% FWHM FWHM



R/C: (12 + 12) = R/C: (12 + 12) = 24 ch./144 24 ch./144 pixelspixels

Operation at 70 F. Operation at 70 F. Bias voltage at 28.8 Volt. ADC Bias voltage at 28.8 Volt. ADC signal integration gate of 150 nsec. Results @ 511 keV. signal integration gate of 150 nsec. Results @ 511 keV. 24x24 pixel 1mm pitch LYSO array from Proteus. Only 24x24 pixel 1mm pitch LYSO array from Proteus. Only about 30% of the detector surface populated with the about 30% of the detector surface populated with the array. The corner region indicated with an arrow. array. The corner region indicated with an arrow.

Corner

Row & Column Readout Scheme for the Row & Column Readout Scheme for the SensL Array4p9 arraySensL Array4p9 array

2.942.94

2.812.81

2.932.93

2.812.81


20.2% 20.2% FWHM FWHM

24.8% 24.8% FWHM FWHM

25.2% 25.2% FWHM FWHM

23.1% 23.1% FWHM FWHM

29.7% 29.7% FWHM FWHM

2.942.94


X-Y Readout Schemes for SensL X-Y Readout Schemes for SensL Array4p9 arraysArray4p9 arrays

R/C: (12 + 12) - 24 ch./144 pixelR/C: (12 + 12) - 24 ch./144 pixel ~ 5cm x 5cm module~ 5cm x 5cm module

Example: 2x2 array - 48 ch./Example: 2x2 array - 48 ch./~10cm x 10cm module~10cm x 10cm module

Example: 2x4 array - 72 Example: 2x4 array - 72 ch./ch./~10cm x 20cm module~10cm x 20cm module

Example: 4x4 array - 96 ch./Example: 4x4 array - 96 ch./~20cm x 20cm module (2304 pixels)~20cm x 20cm module (2304 pixels)


X-Y Readout Schemes for SensL Array4p9 arraysX-Y Readout Schemes for SensL Array4p9 arrays

Example: 2x6 array - 96 ch./ ~10cm x 30cm moduleExample: 2x6 array - 96 ch./ ~10cm x 30cm module

Example: 1x6 array - 84 ch./ ~5cm x 30cm moduleExample: 1x6 array - 84 ch./ ~5cm x 30cm module

CENTER FOR ADVANCED IMAGINGCENTER FOR ADVANCED IMAGINGAT WEST VIRGINIA UNIVERSITYAT WEST VIRGINIA UNIVERSITY X-Y Readout Schemes for SensL X-Y Readout Schemes for SensL

Array4p9 arraysArray4p9 arraysExample: 2x12 (DOI) Example: 2x12 (DOI) ring ring

Readout:Readout:

- 24 sums for energy and DOI24 sums for energy and DOI- 12 trigger signals (for 12 trigger signals (for coincidence matrix)coincidence matrix)- position signals - summed position signals - summed both sides – 12x12 both sides – 12x12 outputs/moduleoutputs/module- multiplexed six modules x multiplexed six modules x 2 = 84 position channels2 = 84 position channels-Total number of position Total number of position channels = 168channels = 168- Total number of readout Total number of readout channels: 192 (for a total channels: 192 (for a total of 3456 individual 3mm of 3456 individual 3mm pixels, reduction factor: pixels, reduction factor: 18) 18)

CENTER FOR ADVANCED IMAGINGCENTER FOR ADVANCED IMAGINGAT WEST VIRGINIA UNIVERSITYAT WEST VIRGINIA UNIVERSITY Summary

•The “resistive” 4ch readout for the SensL SPMArray4 module from AiT Instruments works very well at room temperature (no cooling) down to 1mm LYSO pixel sizes. •The economical, simple and very compact 4ch-per-module readout of the 144 channel Array4p9 module can accommodate the requirements for adequate performance for LYSO scintillation pixel arrays down to ~1.5-2mm pixel size. •The operation is very stable with temperature, with the amplitude change (at the same voltage bias) of less than a factor 2 over the wide tested range of 40-80 deg F. •Initial evidence on DOI operation is that with that design of the readout <2mm FWHM 3D resolution can be obtained using LYSO arrays specially designed for DOI operation.•To achieve 1mm resolution in the present configuration of 3x3 SPMArray4 modules in Array4p9, the row-and-column readout of 12X by 12Y provides this performance at room temperature.•The X and Y outputs from several modules can be multiplexed to produce larger FOV array structures, retaining good spatial resolution, while still with limited total number of ADC readout channels. •Novel 4ch readout from AiT using signal circuitry with signal thresholding is offering better performance than standard “resistive” readout. The optimization of this concept still continues. •Lowering temperature to 42F substantially improves performance.

Charge division readout for SensL SPMArray4 modules (last update October 10, 2011)

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