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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

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slide1

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

9th International “Hiroshima” Symposium

@ International Conference Center Hiroshima, Japan

slide2

2

Contents

PET and Detectors

Evaluation of images by PET

Evaluation of images by MRI

Future prospects and summary

slide3

3

Positron Emission Tomography

Warburg effect

:glucose

  • Cancer cells like glucose

⇒ FDG +

glucose

isotope tracer

DoI

normal cell

cancer cell

Isotope is accumulated in cancer

ToF

  • Functional imaging with 511keV annihilation gamma-ray
  • Time of Flight(ToF) informationimprove S/N
  • Depth of Interaction(DoI) information improve image quality

Cancer

slide4

4

Characteristics of Modalities

  • CT-PET = already being made into a product
  • becoming common as a multimodality imaging device
  • internal and external exposure
  • MRI-PET
  • ToF-PET,DoI-PET
  • No problem of extra exposure

⇒compactness, low power and

⇒insensitivity to B fields is required

high time resolution are required

slide5

5

Detectors

PMT is incorporated in conventional PET scanner

  • high gain
  • long history and proven

PMT

ex.)Super-Kamiokande

However, PMT is …

Scintillator

  • intricate in construction
  • large size
  • sensitive to B fields

13.6mm

SD can overcome these points

13.6mm

PD, APD : compact semiconductor

MPPC : 2D-array of Geiger-mode APDs

especially, MPPC has great characteristics

slide6

6

Characteristics of Detectors

suitable for PET

  • High gain(= doesn’t need CSA)

⇒much betterS/N

⇒much better time resolution (suitable for ToF-PET)

  • Compact and simple structure

⇒suitable for DoI-PET

slide7

7

Our PET Project w/ MPPC

Patent application PCT/JP2012/008129

(Waseda Univ., Furukawa K.K.)

DoI technique

Kishimoto et al. 2013, IEEE

sandwich scinti b/w MPPCs

1mm cube

⇒ K.Takeuchi’s talk yesterday (Compton Camera)

  • widely varying use

ToF technique

Average jitter; 105ps(FWHM)

Time resolution; 616ps(FWHM)

⇒ T.Ambe’s Poster

slide8

8

Characteristics of Detectors

  • No Interfered in static magnetic fields

⇒ Can “future MRI-PET” apply?

slide9

9

Qualification Test

  • image by PET operating with the MRI

influenced from MRI

  • Phantom image by MRI operating with the PET

influenced from MPPC

≪experiment environment≫

BioView Inc.

MRI: Varian INOVA UNITY 4.7 T MRI

(gradient coil: 10 gauss/cm)

slide10

10

Test1: Imaging by PET

static magnetic coil

recieveresponce

gradient coil

linear info.

MPPC condition

  • Outside MRI
  • Inside MRI(under FSE)
  • Inside MRI(under GE)

Left: MPPC array

Hamamatsu S11827-3344MG

Right: Ce:LYSO

12×12 array (1.0×1.0×10mm3 )

source

FSE,GE:

procedures for taking MR image

RF coil

MPPC+LYSO

slide11

11

Result of Test1: Imaging by PET

FSE

outside

GE

slide12

12

Result of Test1: Imaging by PET

Projection X(FWHM)

FSE

1.65±0.07 mm

1.63±0.03 mm

outside

GE

1.70±0.08 mm

slide13

13

Result of Test1: Imaging by PET

FSE

outside

GE

slide14

14

Result of Test1: Imaging by PET

Projection Y(FWHM)

FSE

1.49±0.05 mm

1.48±0.03 mm

outside

GE

1.55±0.13 mm

slide15

15

Test2: Imaging by MRI

(1) inside MRI(MPPC powered on)

(2) inside MRI(MPPC powered off)

(3) removeMPPC

SliceNo.1~5

Slice No.1~5

Before(left) and after(right) removing the probe

No.1

No.2

No.3

No.4

No.5

Images(Cooperation:BioView Inc.)

(1)

(2)

(3)

slide16

16

Result of Test2: Imaging by MRI

power ON (red line)

power OFF (green line)

remove MPPC (blue line)

slide17

17

Result of Test2: Imaging by MRI

Loss Ratio

Only 5% Loss

Loss Ratio=(Power ONor OFF)/(Remove the Probe)×100 [%]

slide18

18

Result of Test2: Imaging by MRI

Power on1

How much noise ?

Only 6(noise) w.r.t. 255(signal)

Power off1

slide19

19

Future prospects

  • PET/MRI have littleimpact on MRI/PET

A more advanced version of the MRI-PET gantry

with 8 MPPC-based PET modules

slide20

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

slide22

Appendix: DoI Technique

Patent application PCT/JP2012/008129

(Waseda Univ., Furukawa K.K.)

Kishimoto et al. 2013, IEEE

DoI position

1mm cube

3mm cube

2mm cube

slide24

:FFC 2m(signal)

:Coax Cable5m(HV)

Connector

Plastic Case

Connector

Plastic Case

Circuit

FFC, CC→LEMO

Alumi. Case

MPPC

Plastic Case

No magnetic fields

magnetic fields

slide25

1. draw flood MAP

  • 2. create LUT
  • 3. select 511keV in LUT

create image

by using the selecting events

slide26

5V power supply

  • temperature compensation circuit
  • HV

×4

  • MPPC
  • Fan I/O
  • Fan I/O

×16

×4

  • Delay
  • Discri.
  • CSADC
  • Coincidence
  • G&D Generator
  • Gate
  • Delay
  • Discri.
  • HV

×4

  • G&D Generator
  • MPPC
  • Fan I/O
  • Fan I/O

×4

  • D I/O

×16

slide27

The principle of MRI.

What is Fast Spin/Gradient Echo?

slide29

N

apply static magnetic field

into protons

Axial directions and phases are parallel

and start to precess

S

slide30

N

apply RF waves

into protons

RF

proton receive the energy and

leanby RF waves (excitation state)

S

slide31

N

stop applying RF waves

into protons

: electromagnetic ray(FID signal)

start to return parallel state

and radiate energy in the form of e.m. rays

RF

S

slide32

animation

A)

All are vertical in the vertical magnetic field

and spinning on their long axis,

but this illustration is in a rotating reference frame where the spins are stationary on average.

B)

A 90 degree pulse has been applied

that flips the arrow into the horizontal (x-y) plane.

C)

Due to local magnetic field inhomogeneities, as the net moment precesses, some spins slow down due to lower local field strength while some speed up due to higher field strength and start getting ahead of the others. This makes the signal decay.

D)

A 180 degree pulse is now applied

so that the slower spins lead ahead of the main moment

and the fast ones trail behind.

E)

The fast moments catch up with the main moment

and the slow moments drift back toward the main moment.

F)

Complete refocusing has occurred

and at this time the echo can be measured.

slide33

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 (≦90deg)

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 180deg pulse into proton after 90deg pulse.

and then the echo of resonance signal is occurred.

spectrum under b field s10362 33 050c
spectrum under B field (S10362-33-050C)

3 kinds of circuit

inside MRI

+

copper shield

outside MRI

inside MRI

in static magnetic fields

under FSE

under GE

MPPC is

compared to outside MRI

  • check the waveform by OSC
  • evaluate each E resolution
slide36

5V power supply

  • temperature compensation circuit
  • HV
  • MPPC
  • Fan I/O
  • Discri.
  • G&D Generator
  • Gate
  • Delay
  • G&D Generator
  • CSADC
  • D I/O

filter circuit

fse ge
FSE,GEによるノイズ

pulse

FSE

outside MRI

511 keV

pulse

GE

511 keV

no interference

by set up discriably

slide38

circuit is

inside MRI

copper shield

outside MRI

inside MRI

MPPC is outside MRI

Grand Level

static magnetic fields

slide39

circuit is

inside MRI

copper shield

outside MRI

inside MRI

MPPC is outside MRI

Grand Level

FSE

slide40

circuit is

inside MRI

copper shield

outside MRI

inside MRI

MPPC is outside MRI

Grand Level

GE

slide41

circuit is

inside MRI

copper shield

outside MRI

inside MRI

MPPC is outside MRI

511keV

static magnetic fields

slide42

circuit is

inside MRI

copper shield

outside MRI

inside MRI

MPPC is outside MRI

511keV

FSE

slide43

circuit is

inside MRI

copper shield

outside MRI

inside MRI

MPPC is outside MRI

511keV

GE

slide44

E resolution

energy resolution(511keV, FWHM)