Upload
schuyler
View
44
Download
1
Embed Size (px)
DESCRIPTION
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 - PowerPoint PPT Presentation
Citation preview
Qualification Test of a MPPC-based PET Module for Future MRI-PET Scanners
Yohta KUREIJ.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
Contents2
1. PET and Detectors
2. Evaluation of images by PET
3. Evaluation of images by MRI
4. Future prospects and summary
Positron Emission Tomography3
Functional imaging with 511keV annihilation gamma-rayTime of Flight(ToF) information improve S/NDepth of Interaction(DoI) information improve image qualityToF
DoICancer
:glucose
normal cell cancer cell
Warburg effect Cancer cells like glucose⇒ FDG + F18
glucose isotope tracer
Isotope is accumulated in cancer
Characteristics of Modalities4
X-ray CT PET MRISpatial Resolution 0.5mm 4 ~ 8mm 1mmExposure (Dose) 10mSv~ ~2mSv nothing
Image structural functional structural
Featurehard tissuesex) bone, tooth
cancerAD
soft tissuesex) cartilage, ligament
MRI-PET
⇒insensitivity to B fields is required
CT-PET = already being made into a productbecoming common as a multimodality imaging device
internal and external exposure
⇒compactness, low power and high time resolution are required
ToF-PET, DoI-PET
No problem of extra exposure
Detectors5
However, PMT is …
PMT
Scintillatorintricate in constructionlarge sizesensitive to B fields
SD can overcome these points
PD, APD : compact semiconductor MPPC : 2D-array of Geiger-mode APDs
PMT is incorporated in conventional PET scanner
high gainlong history and proven
ex.)Super-Kamiokande
especially, MPPC has great characteristics
13.6mm
13.6mm
Characteristics of Detectors6
High gain(= doesn’t need CSA)⇒much better S/N⇒much better time resolution (suitable for ToF-PET)
PMT PD APD MPPCGain
Q.E.[%]Voltage[V]
Volume large smallStructure complex simple
Power Consumption high lowInterfered in B yes no
suitable for PET
Compact and simple structure⇒suitable for DoI-PET
⇒ K.Takeuchi’s talk yesterday (Compton Camera)widely varying use
Our PET Project w/ MPPC7
⇒ T.Ambe’s Poster
Kishimoto et al. 2013, IEEE
1mm cube
Patent application PCT/JP2012/008129(Waseda Univ., Furukawa K.K.)
Average jitter; 105ps(FWHM) Time resolution; 616ps(FWHM)
ToF technique
sandwich scinti b/w MPPCs
DoI technique
Characteristics of Detectors8
PMT PD APD MPPCGain
Q.E.[%]Voltage[V]
Volume large smallStructure complex simple
Power Consumption high lowInterfered in B yes no
No Interfered in static magnetic fields⇒ Can “future MRI-PET” apply?
Qualification Test9
Phantom image by MRI operating with the PET
influenced from MRI
influenced from MPPC
image by PET operating with the MRINa22
≪experiment environment≫BioView Inc.
MRI: Varian INOVA UNITY 4.7 T MRI(gradient coil: 10 gauss/cm )
Test1: Imaging by PET10
MPPC+LYSO
static magnetic coil
RF coil
FSE , GE :procedures for taking MR image
x
y
z
• Outside MRI• Inside MRI ( under
FSE )• Inside MRI ( under
GE )
MPPC condition
sourceNa22
Left: MPPC array Hamamatsu S11827-3344MG
Right: Ce:LYSO 12×12 array (1.0×1.0×10mm3 )
gradient coil
recieve responce
linear info.
Result of Test1: Imaging by PET11
outside
FSE
GE
Result of Test1: Imaging by PET12
outside
FSE
GE
Projection X (FWHM)
1.63±0.03 mm
1.65±0.07 mm
1.70±0.08 mm
Result of Test1: Imaging by PET13
outside
FSE
GE
Result of Test1: Imaging by PET14
outside
FSE
GE
1.48±0.03 mm
1.49±0.05 mm
1.55±0.13 mm
Projection Y (FWHM)
Test2: Imaging by MRI15
Images ( Cooperation : BioView Inc. )
(1)
(2)
(3)
No.1 No.2 No.3 No.4 No.5
Before(left) and after(right) removing the probe Slice No.1 ~5
Slice No.1 ~5
(1) inside MRI(MPPC powered on) (2) inside MRI(MPPC powered off) (3) remove MPPC
Result of Test2: Imaging by MRI16
power ON (red line)
power OFF (green line)
remove MPPC (blue line)
Result of Test2: Imaging by MRI17
Loss Ratio
Loss Ratio=(Power ON or OFF)/(Remove the Probe)×100 [%]
Only 5% Loss
How much noise ?
Result of Test2: Imaging by MRI18
Power on1
Power off1Only 6(noise) w.r.t. 255(signal)
Future prospectsPET/MRI have little impact on MRI/PET
19
A more advanced version of the MRI-PET gantry with 8 MPPC-based PET modules
Summary
We’re developing a more advanced version of the MRI-PET gantry with 8 MPPC-based PET modules
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
20
Appendix
1mm cube2mm cube3mm cube
lengthMPPCMPPC
MPPCZ
21
1DoI position
Appendix: DoI TechniquePatent application PCT/JP2012/008129(Waseda Univ., Furukawa K.K.)
Kishimoto et al. 2013, IEEE
The setup of this experiment
ConnectorPlastic Case
CircuitFFC, CC→LEMO
Alumi. Case
:FFC 2m(signal)
ConnectorPlastic Case
MPPCPlastic Case
magnetic fieldsNo magnetic fields
: Coax Cable 5m(HV)
2. create LUT1. draw flood MAP
3. select 511keV in LUT
create imageby using the selecting events
MPPC
HV
5V power supply
Delay
CSADC
MPPC
Delay
Fan I/O
Fan I/O
Fan I/O
HV
Fan I/O
×4×16
×4
×4
×4
Discri.
Discri.
Coincidence G&D Generator Gate
G&D Generator D I/O×16
temperature compensation circuit
The principle of MRI.What is Fast Spin/Gradient Echo?
Axial directions and phases are in a divided state
N
S
Axial directions and phases are parallel and start to precess
apply static magnetic field into protons
N
S
proton receive the energy and lean by RF waves (excitation state)
RF
apply RF waves into protons
N
S
start to return parallel stateand radiate energy in the form of e.m. rays
RF
stop applying RF waves into protons
: electromagnetic ray (FID signal)
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.
animationB) 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.
FSE : 90 deg pulse + 180 deg pulse
RF waveincline 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 reversalNo Pulse = more shorter time
FSE : a few minutesGE : a few secondsWe 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.
(Not array)spectrum under B field (S10362-33-050C)
spectrum under B field (S10362-33-050C)
3 kinds of circuit
outside MRI inside MRIinside MRI
+copper shield
check the waveform by OSC evaluate each E resolution
in static magnetic fieldsunder FSEunder GE
compared to outside MRI
MPPC is
MPPC
HV
Delay
CSADC
Fan I/O Discri. G&D Generator Gate
G&D Generator D I/O
filter circuit
5V power supply
temperature compensation circuit
FSE , GE によるノイズoutside MRI
FSE
GE
511 keV
pulse
511 keV
pulse
no interference by set up discri ably
outside MRI inside MRIinside MRI
copper shield
static magnetic fields
MPPC is outside MRIGrand Level
circuit is
FSEGrand Level
outside MRI inside MRIinside MRI
copper shield
MPPC is outside MRI
circuit is
GEGrand Level
outside MRI inside MRIinside MRI
copper shield
MPPC is outside MRI
circuit is
511keVstatic magnetic fields
outside MRI inside MRIinside MRI
copper shield
MPPC is outside MRI
circuit is
511keVFSE
outside MRI inside MRIinside MRI
copper shield
MPPC is outside MRI
circuit is
511keVGE
outside MRI inside MRIinside MRI
copper shield
MPPC is outside MRI
circuit is
E resolution
MPPC is outside MRI
MPPC is inside MRI
MPPC isunder FSE
MPPC is under GE
circuit is outside MRI 16.0% 15.2% 15.9% 15.9%
circuit is inside MRI 15.5% 15.6% 15.8% 15.4%
inside MRI+
copper shield16.3% 15.6% 16.4% 15.9%
energy resolution ( 511keV, FWHM )