Qualification Test of a MPPCbased PET Module for

Qualification Test of a MPPC-based PET Module for Future MRI-PET Scanners Yohta KUREI J. Kataoka, T. Kato, T. Fujita, H. Funamoto, T. Tsujikawa (Waseda Univ. ) S. Yamamoto (Nagoya Univ. ) 5 September 2013 9 th International “Hiroshima” Symposium @ International Conference Center Hiroshima, Japan

2 Contents 1. PET and Detectors 2. Evaluation of images by PET 3. Evaluation of images by MRI 4. Future prospects and summary

3 Positron Emission Tomography Warburg effect : glucose Ø Cancer cells like glucose ⇒ FDG + glucose normal cell Cancer Do. I To. F cancer cell isotope tracer Isotope is accumulated in cancer Functional imaging with 511 ke. V annihilation gamma-ray Time of Flight(To. F) information improve S/N Depth of Interaction(Do. I) information improve image quality

4 Characteristics of Modalities 　 Spatial Resolution Exposure (Dose) Image Feature X-ray CT 0. 5 mm 10 m. Sv~ structural hard tissues ex) bone, tooth PET 4～ 8 mm ~2 m. Sv functional cancer AD MRI 1 mm nothing structural soft tissues ex) cartilage, ligament l CT-PET = already being made into a product becoming common as a multimodality imaging device internal and external exposure l MRI-PET No problem of extra exposure ⇒insensitivity to B fields is required l To. F-PET, Do. I-PET ⇒compactness, low power and high time resolution are required

5 Detectors PMT is incorporated in conventional PET scanner high gain long history and proven ex. )Super-Kamiokande However, PMT is … PMT Scintillator intricate in construction large size sensitive to B fields SD can overcome these points PD, APD : compact semiconductor MPPC : 2 D-array of Geiger-mode APDs especially, MPPC has great characteristics 13. 6 mm

6 Characteristics of Detectors 　 PMT Gain Q. E. [%] Voltage[V] Volume large Structure complex Power Consumption high Interfered in B yes PD APD small simple low no High gain(= doesn’t need CSA) ⇒much better S/N ⇒much better time resolution (suitable for To. F-PET) Compact and simple structure ⇒suitable for Do. I-PET MPPC suitable for PET

7 Our PET Project w/ MPPC Patent application PCT/JP 2012/008129 (Waseda Univ. , Furukawa K. K. ) Do. I technique Kishimoto et al. 2013, IEEE sandwich scinti b/w MPPCs 1 mm cube widely varying use ⇒ K. Takeuchi’s talk yesterday (Compton Camera) To. F technique Average jitter; 105 ps(FWHM) Time resolution; 616 ps(FWHM) ⇒ T. Ambe’s Poster

8 Characteristics of Detectors 　 PMT Gain Q. E. [%] Voltage[V] Volume large Structure complex Power Consumption high Interfered in B yes No Interfered in static magnetic fields ⇒ Can “future MRI-PET” apply? PD APD small simple low no MPPC

9 Qualification Test Ø　 image by PET operating with the MRI influenced from MRI Ø　Phantom image by MRI operating with the PET influenced from MPPC ≪experiment environment≫ Bio. View Inc. MRI: Varian INOVA UNITY 4. 7 T MRI (gradient coil: 10 gauss/cm）

10 Test 1: Imaging by PET static magnetic coil recieve responce gradient coil linear info. 　　 source RF coil MPPC+LYSO MPPC condition • Outside MRI • Inside MRI（under FSE） • Inside MRI（under GE） Left: MPPC array FSE，GE： Hamamatsu S 11827 -3344 MG Right: Ce: LYSO procedures for taking MR image 12× 12 array (1. 0× 10 mm 3 )

11 Result of Test 1: Imaging by PET FSE outside GE

12 Result of Test 1: Imaging by PET Projection X (FWHM) outside FSE 1. 65± 0. 07 mm GE 1. 70± 0. 08 mm 1. 63± 0. 03 mm

13 Result of Test 1: Imaging by PET FSE outside GE

14 Result of Test 1: Imaging by PET Projection Y (FWHM) outside FSE 1. 49± 0. 05 mm GE 1. 55± 0. 13 mm 1. 48± 0. 03 mm

15 Test 2: Imaging by MRI 　(1) inside MRI(MPPC powered on) 　(2) inside MRI(MPPC powered off) 　(3) remove MPPC Slice No. 1～ 5 Images（Cooperation：Bio. View Inc. ） No. 1 (1) (2) (3) No. 2 Slice No. 1～ 5 Before(left) and after(right) removing the probe No. 3 No. 4 No. 5

16 Result of Test 2: Imaging by MRI power ON (red line) power OFF (green line) remove MPPC (blue line)

17 Result of Test 2: Imaging by MRI Loss Ratio Only 5% Loss Ratio=(Power ON or OFF)/(Remove the Probe)× 100 [%]

18 Result of Test 2: Imaging by MRI Power on 1 How much noise ? Only 6(noise) w. r. t. 255(signal) Power off 1

19 Future prospects PET/MRI have little impact on MRI/PET A more advanced version of the MRI-PET gantry with 8 MPPC-based PET modules

20 Summary We developed a high resolution, compact PET module for future MRI-PET scanners A slight degradation in the spatial resolutions of PET image operating with MRI Signal Loss Ratio of MR image was only degraded by 5% operating with PET Noise of MR image was only a few percent We’re developing a more advanced version of the MRI-PET gantry with 8 MPPC-based PET modules

Appendix

Appendix: Do. I Technique Patent application PCT/JP 2012/008129 (Waseda Univ. , Furukawa K. K. ) Kishimoto et al. 2013, IEEE Do. I position 3 mm cube 2 mm cube 1 mm cube

The setup of this experiment

: FFC 2 m(signal) ：Coax Cable 5 m(HV) Circuit FFC, CC→LEMO Alumi. Case Connector Plastic Case No magnetic fields Connector Plastic Case magnetic fields MPPC Plastic Case

1. draw flood MAP 2. create LUT 3. select 511 ke. V in LUT create image by using the selecting events

5 V power supply temperature compensation circuit HV MPPC × 4 × 16 Fan I/O × 4 Delay Fan I/O CSADC Coincidence Discri. Delay HV × 4 Fan I/O MPPC × 16 Discri. × 4 Fan I/O G&D Generator　 Gate G&D Generator　 D I/O

The principle of MRI. What is Fast Spin/Gradient Echo?

Axial directions and phases are in a divided state

N apply static magnetic field into protons Axial directions and phases are parallel and start to precess S

N apply RF waves into protons proton receive the energy and lean by RF waves (excitation state) S RF

N : electromagnetic ray (FID signal) stop applying RF waves into protons start to return parallel state and radiate energy in the form of e. m. rays S RF

A) F) B) C) D) E) All 180 are vertical in the magnetic fieldmoment Due A The Complete 90 fast to degree local moments refocusing magnetic pulse catch has isvertical has field now been up occurred inhomogeneities, applied with applied the main as the net spinning onthe their long axis, that moment so and flips the at this the slow precesses, thetime slower arrow moments spins into echo some drift the lead can spins horizontal back ahead be slow measured. toward of(x-y) down the main plane. due main moment tomoment. lower but this illustration is inbehind. asome rotating reference where local and the field fast strength ones trail while speed up dueframe to higher the spins are and stationary on average. field strength start getting ahead of the others. This makes the signal decay. animation

FSE： 90 deg pulse + 180 deg pulse RF wave incline proton at a 90 deg angle RF wave the slower spins lead ahead of the main moment and the fast ones trail behind. GE：α deg pulse + inverse gradient α (≦ 90 deg) shorten the time of incline gradient magnetic field reversal No Pulse = more shorter time FSE：a few minutes GE：a few seconds We want to receive FID signal, but we can’t because the signal decay very fast. (This problem is caused by magnetic field inhomogeneity. ) Then, we repeat applying 180 deg pulse into proton after 90 deg pulse. and then the echo of resonance signal is occurred.

spectrum under B field (S 10362 -33 -050 C) (Not array)

spectrum under B field (S 10362 -33 -050 C) 3 kinds of circuit outside MRI MPPC is inside MRI + copper shield in static magnetic fields under FSE under GE compared to outside MRI Ø　check the waveform by OSC Ø　evaluate each E resolution

5 V power supply temperature compensation circuit filter circuit HV MPPC Fan I/O Delay CSADC Discri. G&D Generator　 Gate G&D Generator　 D I/O

FSE，GEによるノイズ pulse outside MRI FSE 511 ke. V pulse GE no interference by set up discri ably 511 ke. V

circuit is outside MRI Grand Level inside MRI copper shield MPPC is outside MRI static magnetic fields

circuit is outside MRI Grand Level inside MRI copper shield inside MRI MPPC is outside MRI FSE

circuit is outside MRI Grand Level inside MRI copper shield inside MRI MPPC is outside MRI GE

circuit is outside MRI 511 ke. V inside MRI copper shield MPPC is outside MRI static magnetic fields

circuit is outside MRI 511 ke. V inside MRI copper shield inside MRI MPPC is outside MRI FSE

circuit is outside MRI 511 ke. V inside MRI copper shield inside MRI MPPC is outside MRI GE

E resolution energy resolution（511 ke. V, FWHM） circuit is outside MRI circuit is inside MRI + copper shield MPPC is outside MRI MPPC is inside MRI MPPC is under FSE MPPC is under GE 16. 0% 15. 2% 15. 9% 15. 5% 15. 6% 15. 8% 15. 4% 16. 3% 15. 6% 16. 4% 15. 9%