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