towards reconstructionless 3d imaging of positron-emitting
TRANSCRIPT
Simon R. Cherry, Ph.D.
Biomedical Engineering and Radiology
Towards Reconstructionless
3D Imaging of
Positron-Emitting Radiotracers
using Cerenkov Radiation
Disclosures
Research Agreements
Canon Medical Research Unit
United Imaging Healthcare
UC Davis has a revenue sharing agreement with
United Imaging Healthcare
Disclosures
State-of-the-Art PET/CT
• 3-4 mm spatial resolution
• Detection sensitivity 5-10%
• Timing resolution: 200-500 ps
• Speed of light is
– 3 x 108 m/s
– 30 cm/ns
• Current state of the art is ~250 psecs - localizes signal to ~3.75 cm
• 20 psecs timing would localize event to 3 mm
Time-of-Flight (TOF) PET
noise reduction ~
Current work with Scintillators
Courtesy Paul Lecoq (CERN)Courtesy Dennis Schaart (TU Delft)Dennis R. Schaart
Delft University of Technology
Performance summary
32 mm x 32 mm x 22 mm
commercial-grade
LYSO:Ce with double-sided
(DSR) dSiPM readout
A practical and cost effective detector for PET/CT and PET/MRI
with ultrahigh spatial resolution, CRT, and detection efficiency
DOI
PSF CRT
147 ps 1.1 mm
G. Borghi et al, Phys Med Biol 61, 4904–4928, 2016
G. Borghi et al, Phys Med Biol 61, 4929–4949, 2016
Performance parameter State of
the art
BSR
monolithic
DSR
monolithic
Energy resolution < 12% ~10% ~10%
Spatial resolution ~4 mm 1.7 mm 1.1 mm
DOI resolution None 3.7 mm 2.4 mm
Coincidence resolving time 325-400 ps 214 ps 147 ps Monolithic LYSO, double-sided dSiPM L(Y)SO pixels, FBK NUV SiPM
Scintillation is a (relatively) slow process
Scintillator
511 keV
Gamma ray
e-
Cerenkov photons
Scintillation
photons Photodetector
(PMT or SiPM)
Cerenkov Radiation in Scintillators
10-16 sec 10-9 sec
Energetic
electron
Using Cerenkov Radiation for Time-of-Flight PET
Needs:
• Dense materials with high index of
refraction and high transparency in blue/UV
• Photodetectors with high blue/UV
sensitivity and low noise
𝑑𝑁
𝑑𝑥∝ 1 −
𝑐
𝒏 × 𝑣
2
න𝜆1
𝜆2 𝑑𝜆
𝜆2
timing
energy
Scintillators
Physics in Nuclear Medicine, 4th Edition
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
250 450 650
Cerenkov luminescence
BGO transmittance
BGO emission
ToF PET with Bismuth Germanate?
𝑑𝑁
𝑑𝑥∝ 1 −
𝑐
𝒏 × 𝑣
2
න𝜆1
𝜆2 𝑑𝜆
𝜆2
For BGO, n=2.15
Generation of Cerenkov Photons in BGO
Time of Flight PET with BGO
300 400 500 600 700 800
wavelength (nm)
0
0.2
0.4
0.6
0.8
1
Inte
nsity (
a.u
.)
0
10
20
30
40
50
60
70
PD
E (
%)
BGO emission
Cerenkov emission
NUV-HD SiPM (OV=10.3V)
RGB-HD SiPM (OV=9V) 2x3x2 mm3
BGO
267 ps
Kwon et al, Phys Med Biol 2017; 61: L38-47
Microchannel Plate Photomultipliers
Photosensor SPTR (ps)
PMT (R9800) 270
FBK NUV-HD SiPM 91
MCP-PMT (R3809) 25
Single photon time resolution (SPTR) is
critical for very fast timing
Dual-Ended Readout
MCP-PMTs with Integrated Cerenkov Radiator
Ota et al, Phys Med Biol 2019; 07LT01
Scintillator or
Cerenkov radiator
MCP-PMT
Entrance windowPhotocathode
CRI MCP-PMT
Cerenkov radiatorPhotocathode
MCP-PMTs with Integrated Cerenkov Radiator
In collaboration with Ryosuke Ota and Tomohide Omura
CRI MCP-PMT
Cerenkov radiator
(lead glass)
Photocathode
CRI MCP-PMT
Photocathode
SiPM Cerenkov radiator
(lead glass)
Sun Il Kwon
Eric Berg
Emilie Roncali
Acknowledgements
Funding:
R35 CA197608
R03 EB027268
R01 EB029633
Ryosuke Ota
Tokohide Omura Claudio Piemonte
Alberto Gola