Seoul National University Functional & Molecular Imaging System Lab Progress in Nuclear Imaging Mikiko Ito, PhD Dept. of Nuclear Medicine, Seoul National Univ., Seoul 심광숙 교수님 퇴임기념 워크샵 June , 2011

Seoul National University Functional & Molecular Imaging System Lab 1.PET/MRI 2.New DOI detector

Seoul National University FMIS Lab Positron Emission Tomography What is PET based on the coincidence detection of a pair of positron annihilation gamma-rays

Seoul National University FMIS Lab Positron Emission Tomography What is PET based on the coincidence detection of a pair of positron annihilation gamma-rays Provide biochemical information by using positron-emitter labeled pharmaceuticals have higher performance for resolution, sensitivity, and quantitative accuracy compared with SPECT

Seoul National University FMIS Lab Imaging Technique Range of EM Wave Spatial Resolution SensitivityAnatomical Imaging Molecular Imaging PET511 keV1 ~ 10 mm ~ mole/L ++++ MRIMicrowave25 ~ 100 μm ~ mole/L ++++ CTX-ray50 ~ 200 μm+++ PETMRICT Motivation for PET/MRI

Seoul National University FMIS Lab MR-Compatible SiPM PET Insert PET insert with 12 detector modules (D=13.6 cm) Dedicated FPGA-based acquisition system LGSO ( 1.5x1.5x7.0 mm 3 ) 20x18 array SiPM (4x4 MPPC) 2x2 array Shielding box Position encoding (64  4 ch) LGSO & SiPM Temperature sensor & Amplifiers

Seoul National University FMIS Lab Simultaneous PET/MR Imaging Siemens MAGNETOM Trio 3T MRI 4-cm loop receiver coil X2

Seoul National University FMIS Lab With RF shielding MR Compatibility of SiPM PET Without RF Inside 3T MRI T2 Turbo Spin Echo

Seoul National University FMIS Lab Simultaneous PET/MRI Studies T2 MRIFusionSNU SiPM PET FDG PET & T2 MRI in BALB/c Mouse Kidneys

Seoul National University Functional & Molecular Imaging System Lab 1.PET/MRI 2.New DOI detector

Seoul National University FMIS Lab Why DOI Measurement? Long crystal Small cross section Small diameter Small-ring PET system : Small animal, breast, brain… Small cross section of crystal long crystal

Seoul National University FMIS Lab Why DOI Measurement? Small-ring PET system : Small animal, breast, brain… Small cross section of crystal long crystal If the DOI position is unknown Parallax error

Seoul National University FMIS Lab Why DOI Measurement? If the DOI position is unknown Parallax error If the DOI position is known Depth of interaction (DOI)

Seoul National University FMIS Lab Multi-layer detector DOI Detector Designs Multi-anode PMT Typically 5~10 mm Discrete DOI information High manufacturing cost Dual-ended readout detector Continuous DOI information High manufacturing cost Damage of front sensor by gamma rays

Seoul National University FMIS Lab Multi-layer detector DOI Detector Designs Multi-anode PMT Typically 5~10 mm Dual-ended readout detector Continuous DOI information High manufacturing cost Damage of front sensor by gamma rays Discrete DOI information High manufacturing cost Cons

Seoul National University FMIS Lab Dual-ended readout detector DOI Detector Designs Multi-anode PMT Typically 5~10 mm Multi-layer detector Continuous DOI information High manufacturing cost Damage of front sensor by gamma rays Discrete DOI information High manufacturing cost Cons

Seoul National University FMIS Lab DOI Detector Designs Multi-anode PMT Typically 5~10 mm Multi-layer detector Dual-ended readout detector Discrete DOI information High manufacturing cost Continuous DOI information High manufacturing cost Damage of front sensor by gamma rays Pros Cons

Seoul National University FMIS Lab Direct DOI measurement DOI Detector Designs Direct DOI measurement Discrete DOI with high resolution Low packing fraction Large output channels High manufacturing cost WLS strip Crystal SiPM

Seoul National University FMIS Lab Direct DOI measurement DOI Detector Designs Direct DOI measurement Discrete DOI with high resolution Low packing fraction Large output channels High manufacturing cost WLS strip Crystal SiPM Pros Cons

Seoul National University FMIS Lab Direct DOI measurement DOI Detector Designs Direct DOI measurement Discrete DOI with high resolution Low packing fraction Large output channels High manufacturing cost WLS strip Crystal SiPM Pros Cons Aim of our study : To develop new DOI detector that does not require additional crystals or photo-sensors

Seoul National University FMIS Lab Concept of DOI Measurement Single-layer crystal array + Single-ended readout  Cost-effectiveness Multi-anode PMT Triangular teeth reflector

Seoul National University FMIS Lab Concept of DOI Measurement Tailoring light spread  Continuous DOI Multi-anode PMT Reflector grid Single-layer crystal array + Single-ended readout  Cost-effectiveness Triangular teeth reflector

Seoul National University FMIS Lab Concept of DOI Measurement Multi-anode PMT Reflector grid Triangular teeth reflector Reflector grid : constructed by crossing the triangular-teeth strips

Seoul National University FMIS Lab Concept of DOI Measurement Multi-anode PMT Reflector grid Triangular teeth reflector y x z Reflector grid : constructed by crossing the triangular-teeth strips

Seoul National University FMIS Lab Concept of DOI Measurement Triangular teeth reflector y x z Reflector grid : constructed by crossing the triangular-teeth strips Upper- half Lower- half Direction of light dispersion Within the upper-half block : in the y direction Within the lower-half block : in the x direction Amount of dispersion : depends on the DOI position

Seoul National University FMIS Lab Concept of DOI Measurement Triangular teeth reflector y x z Reflector grid : constructed by crossing the triangular-teeth strips Direction of light dispersion Within the upper-half block : in the y direction Within the lower-half block : in the x direction Amount of dispersion : depends on the DOI position Upper- half Lower- half

Seoul National University FMIS Lab Concept of DOI Measurement Reflector grid : constructed by crossing the triangular-teeth strips Direction of light dispersion Within the upper-half block : in the y direction Within the lower-half block : in the x direction Amount of dispersion : depends on the DOI position Triangular teeth reflector y x z Upper- half Lower- half DOI information : by comparing X and Y signal distributions

Seoul National University FMIS Lab Detector Design Triangular-teeth shape Conventional strip shape Detector design Unpolished LYSO (22 x 22 array) Crystal : 2.0 x 2.0 x 28 mm 3 H8500 PMT (8 x 8 anode array) Triangular teeth reflector y x z

Seoul National University FMIS Lab ( b x, b y, (a x – a y + A )/E ) DOI Response 2 mm 26 mm 6 mm 10 mm 14 mm 18 mm 22 mm H8500 PMT 3D DOI response function (a x – a y + A )/E 26 mm 22 mm 18 mm 14 mm 10 mm 6 mm 2 mm 3D DOI response map “Side on” irradiation

Seoul National University FMIS Lab DOI Response Estimation of DOI resolution 3D DOI response map (a x – a y + A )/E B Counts DOI resolution : 3.52 mm 2D projection map histogram  Average DOI resolution : 3.5 mm for 28 mm crystal array

Seoul National University FMIS Lab Crystal Identification Flood image 40 cm “Front on” irradiation 22 x 22 array  All crystal positions were well separated in flood image H8500 PMT

Seoul National University FMIS Lab Summary 1. New DOI detector : monolayer crystal array + single-ended readout 2.DOI dependency : 2D light dispersion tailored by geometry of reflector frame (triangular teeth shape) 3.Initial performances -Average DOI resolution of 3.5 mm for 2.0 x 2.0 x 28 mm crystals -Energy resolution of 15.8 ~ 18.8 % -Time resolution of 1.2 ~ 1.8 ns -All crystals are separated in flood image

Seoul National University FMIS Lab Thank you for your attention

Seoul National University FMIS Lab Dept. of Nuclear Medicine