PETMR intro E

林口長庚醫院核子醫學科
DepartmentofNuclearMedicineandMolecularImagingC.G.M.H.Linkou
Introduction of PETMR
Camus C.Y. Wu. 吳志毅
Medicalradiationtechnologist醫事放射師
DepartmentofNuclearMedicineandMolecularImagingC.G.M.H.長庚醫院核子醫學科
Experiences OF NM Dep. C.G.M.H.Linkou

INTRODUCTION OF PETMR
BASIC OF PETMR
CLINICAL WITH PETMR
CHALLENGE OF PETMR

BASIC OF PETMR
Why we need PETMR？

Perfusion ratevolumetransit time
Gd
Gd
wash in wash out
rate？
Transit time？
volume？

wash in wash out
concentration
time
Perfusion ratevolumetransit time

wash in wash out
Gd
Gd
Gd concentration↑
▼
Inhomogeneity ↑
Perfusion and magnetic field

T2 DSC (dynamic susceptibility contrast-enhanced)
Intensity(AIF)
time
Perfusion and magnetic field

＊only a certain extent
Diffusionandvectorofwatermolecules

fMRIandregionaloxygenconsumption

Feeding ≠ actual intake
O2 in Water ≠ Oxygen consumption

Identify the primary or metastatic lesions,
staging or assess the malignancy by the :
① metabolic path
② synthesis of the amino acids or proteins
③ specific hormones and their receptors
④ tumor related necrosis, abscess and hypoxiaF-18FDGC-11 L-Methioine tumor survey

▲ pathway of the myocardium viability scan
Using the blood perfusion and
oxygen consumption analysis, also
possible to use the "neurotransmitter
-receptor" or "metabolism" to assess
the myocardium or cardiac function.

Normal case （▲▲） PD case （▲）with
the F-18 FDOPA scan
Using the blood flow, metabolism,
neurotransmitter-receptor to assess
the blood flow (CBF) , Oxygen
consumption (CMRO2) and other
specific function or the functional
diseases.

F-18 Aβ amyloid scan
normal case(left) and abnormal case with diffuse distribution (right)

Ann Neurol. Author manuscript; available in PMC 2013 March 02.

● Ga-68 PSMA(prostate specific membrane antigen)：

PETMR PET-MR

BASIC OF PETMR
Evolution of PETMR

GE PET/CT+MR Trimodality Solution

Challenges of PET-MR
‧PET elements can not shielded the RF.
‧MRI elements can not cause the
attenuation of photon.
‧PET element can not cause magnetic
field inhomogeneity.
‧PMT malfunction under magnetic field.
‧Unable to perform the attenuation and
scatter fraction correction .

V
V
V

PMT malfunction
under magnetic field
How to solve the：

PrototypeA：opticalfiberPET in 1.5T MR

Genetic algorithms for MRI magnet design. Shaw, N.R.; Ansorge, R.E. (2002) IEEE Trans Appl Supercond 12, 733-736
Development of a Combined microPETR-MR System. Lucas A.J. et al. (2006) Technol Cancer Res Treat 5, 337-341
PrototypeB：APD PETMR

▲SiPM, (Silicon photomultipliers )
▲APDs,( Avalanche Photo Diodes )
SiPM and APDs has the following characteristics:
1. don’t need high voltage power supply.
2. unaffected by magnetic fields.
3. smaller, and allow design to fit needs.
4. Optical yield and gain similar to traditional PMT.

▲ SIEMENS APDs system. Dep. of Nuclear Medicine and Molecular Imaging C.G.M.H.
▲ GE SSPM system. Dep. of Radiology U.H.Z.

Attenuation Correction
and ScatterFraction Correction
Perform the ：

MR signal is not related to electromagnetic wave density
PET image constructed by the ：
① Emission data
② Attenuation correction factor (ACF)
③ Normalization data

correction w anatomical pattern method
MR signal classification method

①CombineMRimgwithknownattenuationcoefficientsanatomical
templates.
②Infertheattenuationcoefficientatthisplacefromtheanatomicaltemplate.
correction w anatomical pattern method
Advantages:
① the μ value of complex parts such as bones can be estimated.
② no linear attenuation coefficient confounding (binned, which will reduce the resolution).
Disadvantages:
① Need a lot of representative data.
② abnormality part can’t be controlled.
③ Limited by the transformation map accuracy.

①differenttypeoforganizationdoclassificationofMRimaging.
②Applythecorrespondingattenuationcoefficient.
MR signal classification method
Advantages:
① more convenient and fast.
② not easily affected by abnormalities anatomical parts.
Disadvantages:
① There will be a problem of linear attenuation coefficient confounding .
② MR signals cannot classified the bones or some complicated parts,.

μ map對應衰減係數（cm-1）
Air(Bkg) 0
lung 0.0180~0.0224
Fat&Bone marrow 0.0854~0.0860
Soft tissure 0.1000
Bone > 0.1050
※ pixel :cm-1 = 1/10,000

withEmissionconversionfactor(ECF)

V
V
V
V
V

BrainPET for MAGNETOM Trio, 11.17.2006

MR and PET separate and stand alone.
MR and PET integrated in one.12. 2010 two types of business models

BASIC OF PETMR
Structure of integrated PETMR

integrated PETMR：8 block(8x8:4x4x20 mm) in 1 cassette
2 cassette in 1 DEA（DetectorElectronicAssembly）：28 DEA
DEA

TheTotalscore(E)andtheSignaldistribution
weight(X,Z)inthetraditionblockdetectoris：
E = A+B+C+D
X = (B+D)/E
Z = (C+D)/E
A B
C D
crystal PMT

The "signal distribution" of the integrated
PETMR is relatively complex. We replacing
the traditional 4 PMTs with a virtual PMT of 9
APDs per block:
A= 2(0)+(1)+(3)+(4)
B= 2(2)+(1)+(5)
C= 2(6)+(3)+(7)
D= 2(8)+(5)+(7)+(4)
then,gobacktothetraditionalcalculationmethod

CLINICAL WITH PETMR

What the PETMR（mMR）can provided?

Image diagnosis
■ F-18 FDG mMR scan of Brain tumor Head&Neck ca.

Image diagnosis
■ F-18 FDG mMR scan of Lung ca. Breast ca.

Image diagnosis
■ Brain tumor w C-11 Acetate
■ Thyroid ca. w I-124 sodium
■ Prostate ca. w C-11 Choline

■ Sequences of brain meta. detection ■ Sequences of NET
Image diagnosis

PET＋MR fusion
a billion dollars
？

■ Dementia_ amyloid PET image w MRASWIfMRI
ImageQuantitativeandAnalysis

■ Dementia_ FDG PET image w MRASWIrest fMRI

■ Dementia_ FDG PET image w fMRI

■ Brain tumor_ C-11 Acetate w wash inout, ktrans, MRS

■ Brain tumor _ F-18 FDG w DTI fiber tracks

■ Breast ca._FDG w mean curve

■ Prostate ca. _ C-11 choline w T1 mapping

■ CVS disiz_ C-11 Acetate w MR perfusion T1 mapping

WhatthePETMRcanprovided?
Diagnosis staging evaluation → prognosis
Combine image:
increased sensitivity. specificity, accuracy.
Quantitative and Qualitative:
increased consistency

Parametric Images
total lesion glycolysis (TLG)
Metabolicrateforglucose： (plasmaglucoseconcentration/lumped constant) x [(k1‧k3)/(k1+k3)]
P E T

Parametric Images

CHALLENGE OF PETMR

Conventional long magnets MR
Superconducting magnet
RF coil
Gradient coil

PETMR short magnet MR
RF coil
Gradient coilPET detector
• Poorhomogeneous
• Poorcontrast
• Poorcoolingeff.
Superconducting magnet

Disadvantages of diodes:
Area and price are non-linearly proportional.
The heat dissipation efficiency.
→ Thermal efficiency determines performance.
→ Thermal efficiency affects stability.

Is the electronic components interference the EPI image ?

CTAC: W/air/soft tissue/bone
psudoMRAC: W/air/soft tissue

DIXON AC:
W/air/soft tissure
UTE AC:
BONE/air/soft tissure

整合型PETMR的挑戰與限制 – T. O . F. ＆ P. S . F.

整合型PETMR的挑戰與限制 – T. O . F. ＆ P. S . F.
Precautions for correcting metal artifacts
with μ map：
1.ItisrecommendedtochangetoPETorPET/CTscanfirst.
2.Notcertify,itisnotsuitableforclinicaluse.
3.UseUTEμmaptoavoidinfluenceofattenuationcoefficient.
4.Theskullbaseorexcessiveboneareaarenotapplicable.
5.Trytokeeptheleft-rightsymmetrytoreducethegeometric
positionalvariableswhenpositionpatient.
6.disablefunctionssuchasPSForVUEtoavoidcausingSUV
numericalerrors.

THE JOURNAL OF NUCLEAR MEDICINE • Vol. 56 • No. 7 • July 2015

I. J. Radiation Oncology d Biology d Physics Volume 81, Number 1, 2011

● F-18 FDG / DCE IAUC(Ktrans) FUSION● C-11 ACT / Diffusion b200 FUSION

SHIMfailureandMagnetinhomogeneous
DIXON AC error

Advantages of TOF in PETCT:
‧Improve the PET image correctness
which may affected by wrong CTAC due to the
metal artifacts.
‧Improve PET image quality.

but…
Paramagnetic metal caused the
magnetic field inhomogeneous,
and lose signal.
however, No AC No PET image!

Quantitative comparison of PET performance, Karlberg et al. EJNMMI Physics (2016) 3:5
In addition to TOF method,
PSF (Point spread function) also
can get a better image quality.

GE
GeometryEmbracingMethod
SIEMENS
TIM CT Fastview

結論

Simple is not Easy
Easy is a minimum amount of effort to produce a result.
Simple is very hard. Simple is the removal of everything except what matters.

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PETMR intro E

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