Progress in Nuclear Imaging Mikiko Ito Ph D

Progress in Nuclear Imaging Mikiko Ito, Ph. D Dept. of Nuclear Medicine, Seoul National Univ. , Seoul 심광숙 교수님 퇴임기념 워크샵 June. 11 -12, 2011 Seoul National University Functional & Molecular

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

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

Motivation for PET/MRI PET Imaging Technique MRI Range of EM Spatial Wave Resolution PET 511 ke. V 1 ~ 10 mm MRI Microwave 25 ~ 100 μm CT X-ray 50 ~ 200 μm CT Sensitivity 10 -11 ~ 10 -12 mole/L 10 -3 ~ 10 -5 mole/L Anatomical Molecular Imaging + +++ Seoul National University FMIS Lab

MR-Compatible Si. PM PET Insert LGSO (1. 5 x 7. 0 mm 3) 20 x 18 array Shielding box Si. PM (4 x 4 MPPC) 2 x 2 array Temperature sensor & Amplifiers PET insert with 12 detector modules (D=13. 6 cm) Dedicated FPGA-based acquisition system Position encoding (64 4 ch) LGSO & Si. PM Seoul National University FMIS Lab

Simultaneous PET/MR Imaging Siemens MAGNETOM Trio 3 T MRI 4 -cm loop receiver coil X 2 Seoul National University FMIS Lab

MR Compatibility of Si. PM PET Without RF Inside 3 T MRI T 2 Turbo Spin Echo With RF shielding Seoul National University FMIS Lab

Simultaneous PET/MRI Studies T 2 MRI Fusion SNU Si. PM PET Kidneys FDG PET & T 2 MRI in BALB/c Mouse Seoul National University FMIS Lab

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

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

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

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

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

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

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

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

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

DOI Detector Designs Direct DOI measurement Pros • Discrete DOI with high resolution Cons • Low packing fraction • Large output channels • High manufacturing cost e ir u q e r t no s e o d t o f ha t o r o t m c i e A et d I O D rs w o e s n n e p s o to vel o e h d p r o o T : ls a t s y r c nal o i t i d d a y d u t s r u WLS strip Crystal Si. PM Seoul National University FMIS Lab

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

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

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

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

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

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

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

Detector Design Detector design • Unpolished LYSO (22 x 22 array) • Crystal : 2. 0 x 28 mm 3 • H 8500 PMT (8 x 8 anode array) Triangular-teeth shape Conventional strip shape Triangular teeth reflector z y x Seoul National University FMIS Lab

DOI Response “Side on” irradiation 3 D DOI response function ( bx , by , (ax – ay + A )/E ) (ax – ay + A )/E 3 D DOI response map 26 mm 22 mm 18 mm 14 mm 10 mm 6 mm 2 mm H 8500 PMT 26 mm 22 mm 18 mm 14 mm 10 mm 6 mm 2 mm Seoul National University FMIS Lab

DOI Response Estimation of DOI resolution 2 D projection map histogram Counts (ax – ay + A )/E 3 D DOI response map DOI resolution : 3. 52 mm B § Average DOI resolution : 3. 5 mm for 28 mm crystal array Seoul National University FMIS Lab

Crystal Identification Flood image “Front on” irradiation 40 cm 22 x 22 array H 8500 PMT § All crystal positions were well separated in flood image Seoul National University FMIS Lab

Summary 1. New DOI detector : monolayer crystal array + single-ended readout 2. DOI dependency : 2 D 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 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 Seoul National University FMIS Lab