8/18/2015G.A. Fornaro Characterization of diffractive optical elements for improving the performance...

$: 8/18/2015G.A. Fornaro Characterization of diffractive optical elements for improving the performance of an endoscopic TOF- PET detector head Student: G.$
04/19/23 G.A. Fornaro

Characterization of diffractive Characterization of diffractive optical elements for improving optical elements for improving

the performance of an the performance of an endoscopic TOF-PET detector endoscopic TOF-PET detector

head head Student: G. A. Fornaro

Supervisor: G. Battistoni


OutlineOutline

PET principles EndoTOFPET-US: the project

Time of light (TOF) principle

Optical optimization by means of micro optical element (MOE)


tracerInjection(18F-FDG)

Ring of scintillators

Ring of scintillators

PET PrinciplesPET Principles

e+

e-e+

Neutron-deficient isotope

pp

pp

ppn

nnn p

n n

e+γ (511 KeV)γ (511 KeV)

γ (511 KeV)γ (511 KeV) 2π coincidences2π coincidences

Parallel projections

Projection

fs

PET data (sinograms)s

zf

f

PET images

z

x

Reconstruction

LORLOR

04/19/23 G.A. Fornaro04/19/23

PET: origins of noisePET: origins of noise

• True coincidences • Scattered

coincidences• Random coincidences

Coincidence time window (Δt): time in which two detected photons are considered to be originated in the same event

StR

R

s

t

1

SRt

2StRr

In order to reduce the noise it is important to improve the time resolution of the detecting system and thus to maximize the

number of photon extracted from the crystal

In order to reduce the noise it is important to improve the time resolution of the detecting system and thus to maximize the

number of photon extracted from the crystal

pheNt

In a PET detection system:In a PET detection system:

Single count rate

Single count rate

Duration of scintillationDuration of scintillation

Number of phe in the detector

Number of phe in the detector

04/19/23 G.A. Fornaro04/19/23

EndoTOFPET-US project

• First clinical target: pancreatic cancers;

• Develop new biomarkers;

• Develop a dual modality PET-US endoscopic probe

with...– Spatial resolution: 1mm– Timing resolution: 200ps FWHM coincidence– High sensitivity to detect 1mm tumors in a few minutes– Energy resolution: sufficient to discriminate against Compton

events

04/19/23 G.A. Fornaro04/19/23


build a prototype of a PET-US endoscopic probe for detection of early stage pancreatic tumors

Aim:

04/19/23 G.A. Fornaro04/19/23


build a prototype of a PET-US endoscopic probe for detection of early stage pancreatic tumors

Aim:

Scintillating crystal matrix

Micro optical elementd-SiPM

Biopsy niddle

Ultrasound trasducer


US: detects regions in which the density of the tissue changes (possible cancer)



PET detectorPET detector

Exte

rnal

PET

Pla

te



Exte

rnal

PET

Pla

te

EndoTOFPET project


Detector B

Detector A

e-e+Patient

tA

tB

dd1

Time of Flight info reduce the Time of Flight info reduce the statistical noise variance statistical noise variance

CONVTOF SNRd

DSNR

cmD 3

2

tcd

c

ddddttt AB

11

withwith

pst 200


Detector B

Detector A

e-e+Patient

tA

tB

dd1

Time of Flight info reduce the Time of Flight info reduce the statistical noise variance statistical noise variance

CONVTOF SNRd

DSNR

cmD 3

2

tcd

c

ddddttt AB

11

withwith

pst 200

d-SiPM with single SPAD readout for single optical photon counting

d-SiPM with single SPAD readout for single optical photon counting

Individual SPAD

04/19/23 G.A. Fornaro04/19/23

Problem: 50% light of the crystal is lost in the dead zones of the d-SiPM

Crystal MOEd-SiPM

MOE:Aim and concept

04/19/23 G.A. Fornaro04/19/23

Crystal

Solution: optical collimator btw crystal and photodetector

Optical collimator/Lenticular Lens

500µm

MOEd-SiPM

Problem: 50% light of the crystal is lost in the dead zones of the d-

SiPM

MOE:Aim and concept

04/19/23 G.A. Fornaro04/19/23

1) Match pitches of d-SiPM (25µm active area);

800 µm

25 µm 25 µm

Crystal


MOEd-SiPM


MOE:Aim and concept

04/19/23 G.A. Fornaro04/19/23

1) Match pitches of d-SiPM (50µm);2) Concentrate the maximum of light into parallel

rays3) Create ‘differential’ light pattern on the SPAD

surface only;


MOECrystal d-SiPM

d-SiPM


MOE:Aim and concept



1) Match pitches of d-SiPM (50µm);2) Concentrate the maximum of light into parallel rays3) Create ‘differential’ light pattern on the SPAD surface only;

Solution: optical collimator between crystal and photodetector

MOECrystal d-SiPM

04/19/23

simulations forecast a transmission simulations forecast a transmission gain of 1.3gain of 1.3

MOE:Aim and concept

04/19/23 G.A. Fornaro04/19/23

We have built and tested different benches for the optical characterization of the MOE:

Crystal + MOE in direct contact with the sensitive area of a CCD used as photodetector

Characterization of light distribution at the output of the crystal (input of MOE)

Characterization of MOE in direct contact with CCD (near field): by changing the angle of incidence of light on the MOE we detected the transmitted light at its output

Complete characterization of MOE with the camera (far field): by changing the angle of incidence of light on the MOE we detected the light distribution at its output

X- Rays source Matrix

CCDUSB connection

MOE

CCD+MOE

Rotating disk

filter

pinhole

PMTγ-Source crystal

UV Lamp

MOE

θγ

filterUV Lamp

DigitalCamera

Benches for MOE characterizationBenches for MOE characterization

04/19/23 G.A. Fornaro04/19/23

… Thanks for

your

attention!

The works are in progress…

Reach a convergence btw experimental parameter and the ones of simulations in order to make the comparison of the results

more and more realistic

Final aim:understand well the input parameters of the

MOE in order to be able to forecast its output’s intensity profile

04/19/23 G.A. Fornaro04/19/23

Direct contact with CCD


CCD USB connection

Proteus/AGILE 4x4 crystal matrix :•all crystals fully wrapped (Vikuiti)•X-Rays (40 keV) could only penetrate and excite the first vertical row of crystal

Horizontal position (pixels)

Inte

nsity

(a.u

.)

X-Rays direction

Bare Matrix

air interface crystal-CCD

Average of each vertical

array of pixels

Horizontal array of averages intensities

04/19/23 G.A. FornaroHorizontal position

(pixels)

Inte

nsity

(a.u

.)

Bare MatrixMatrix + MOE (air)

04/19/23

Direct contact with CCD

X-Rays direction

air interface crystal-MOE and MOE-CCD


CCDUSB

connection

MOE

Proteus/AGILE 4x4 crystal matrix :•all crystals fully wrapped (Vikuiti)•X-Rays (40 keV) could only penetrate and excite the first vertical row of crystal

Average of each vertical

array of pixels

Horizontal array of averages intensities


Inte

nsity

(a.u

.)

3 4 65 87 109 111213 14

Bare Matrix

Matrix + MOE (air)

25μm

Horizontal position (pixels)04/19/23

For evaluating the gain we would have in the active regions of a SPAD that will be put in front of the MOE we calculated:

1. the integral of the intensity of light coming out from the crystal+MOE in a region of 25μm (≈5 pixels) around each peak;

2. the integral of the intensity of light coming out from the bare crystal in the same regions of 25 μm

A.R. = gain in the active regions of a SPAD

peak 1 2 3 4 5 6 7 8 9 10 11 12 13 14

A.R. 1.21 1.25 1.30 1.29 1.26 1.26 1.26 1.23 1.24 1.25 1.25 1.28 1.28 1.30

Average gain on the peaks = 1.26Gain forecasted by simulations =1.7

Direct contact with CCD: matrix in dry contact with MOE

Gain on single peaks


WP1: UnivMedProject Coordination

WP2: CERNCrystals and opticsScintillating fibers

and diffrative coupling optics

WP6: TUM Clinical requirements & preclinical and pilot clinical studies

Feasibility tests on pigs, Pilot clinical tests, Impact on biomarker studies

WP3: Delft TU Photodetectors

Novel digital photodetectors

WP4: LIPFE and DAQ

electronicsHighly integrated TOF electronics

WP5: DESYDetector IntegrationMiniaturized probe

Tracking&Image fusion

4 years project

8/18/2015G.A. Fornaro Characterization of diffractive optical elements for improving the performance...

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