INSERT: Challenges in Developing SPECT/MRI€¦ · Introduction PET/MRI Symposium 2 London, 21-23 Sep 2016 Débora Salvado Around 10,000 children and adults are diagnosed with brain

INSERT: Challenges in Developing SPECT/MRI

Débora SalvadoInstitute of Nuclear Medicine

University College London

On behalf of the INSERT consortium

PET/MRI SymposiumLondon, 21-23 September 2016

Introduction

2PET/MRI SymposiumLondon, 21-23 Sep 2016

Débora Salvado

Around 10,000 children and adults are diagnosed with brain tumours annually in the UK:

¼ of childhood cancer incidence and 6% overall

Gliomas make up to 30% of malignant brain tumours

Recurrence is high and the outcome is very poor

Glioma imaging gold standard is MRI. But:

Abnormal MRI signal following treatment that mimics progression

No marker for high grade vs low grade disease

Challenging to measure treatment response

Biology of microscopic residual disease not visible

No individualised treatment with patient selection for specific agents

Paediatric patients need anaesthesia

pseudo-progression

tumour grading

response monitoring

specificity

single session scans

Cancer Research UK; Goodenberger et al., Cancer Genetics 2012.

The INSERT Project


Débora Salvado

EC projectGA n. 305311Kickoff: 01/03/13Duration: 4 years

Provide improved personalized radiochemotherapies for brain tumour(glioma) patients using a specifically developed multi-modality imaging tool.

Integrated SPECT/MRI for enhanced stratification in radiochemotherapy

The Consortium


Débora Salvado

Politecnico di Milano (Italy)C.Fiorini, P.Busca, A.D.Butt, M.Occhipinti, P.Triglio, M.Carminati, G.Montagnani

Mediso Medical Imaging Systems (Hungary)K.Nagy, T.Bukki, M.Czeller, Z.Papp, Z.Nyitrai, G.Nemeth, P.Major, G.Legradi

Fondazione Bruno Kessler (Italy)C.Piemonte, A.Ferri, A.Gola

MRI.Tools GmbH (Germany)J.Rieger, T.Niendorf, A.Kuehne

Nuclearfields International BV (Netherlands)P.vanMullekom, C.Linskens, J.Willems

University College London (UK)B.F.Hutton, K.Erlandsson, D.Salvado, S.Short, I.Francesco

Università Vita-Salute San Raffaele (Italy)L.Politi, R.Moresco, S.Belloli, G.DiGrigoli, S.Valtorta

Università Degli Studi di Milano (Italy)L.Ottobrini, C.Martelli

Cromed Research and Services ltd.(Hungary)D.Mathe

CF Consulting srl. (Italy)C.Finocchiaro, S.Cogoni

Preclinical vs Clinical System


Débora Salvado

20 cm

Explore glioma models on mouse and rat brains.

Extend technology to clinical SPECT to investigate human glioma treatment.

Stationary insert system Radiotracers: 99mTc, 111In, 123I

Detection module

Collimator RF Coil

10 cm

20 cm

The Challenges


Débora Salvado

MR-compatible solid state readout: SiPMs replace PM tubes convert light to electrical signal suitable to amplify low light levels compact and robust compatible with magnetic field require cooling

APD SiPM

PMTB=0 B>0

EM Interference

Limited Angular Sampling

Restricted Space, Materials and Weight

Collimator!

Radiation shielding

Detection Module


Débora Salvado

Pre-Clinical System(small animals)

5 cm 5 cm

SiPMreadout

Cooling block

ASIC readout + DAQ board

CsI:Tlcrystal

Clinical System(humans)

10 cm

5 cm

ASIC readout + DAQ board

SiPMreadout

CsI:Tlcrystal

Cooling block

Single SiPM contains 16000 APDs Single SiPM tile contains an array of 6x6 SiPMs Detection module readout: 4 (pre-clinical) or 8 (clinical) SiPM tiles

Cooling Block


Débora Salvado

Unasembled cooling block’s lower piece showing serpentine pathways for cooling the passing fluid (water+glycol).

Specific design to the INSERT detection module.

Measurements using a 57Co source, with SiPMs at ~0oC.

Spatial Resolution


Débora Salvado

Lead plate Thickness: 2 mm Hole diameter: 0.5 mm Pitch: 2 mm

0 10 20 30 40 500.6

0.8

1

1.2

1.4

1.6

1.8

2

2.2

X [mm]

Reso

luti

on

[m

m]

<FWHM> ~1.0 mmBusca et al., Conf. Rec. IEEE NSS/MIC 2015.

0 2000 4000 6000 8000 10000 120000

0.5

1

1.5

2

2.5x 10

4

Channels [Ch]

Co

un

ts

122 keV

Measurements using a uniform 57Co source, with SiPMs at ~0oC.

Energy Resolution


Débora Salvado

FWHM R ~ 14%

Busca et al., Conf. Rec. IEEE NSS/MIC 2015.

Collimator Design (1)


Débora Salvado

Use multiple small high intrinsic resolution detectors.

Sensitivity maximized using multiple apertures with minification rather than magnification.

𝑅sys = 𝑅geom2 + 𝑅intr × 𝑚𝑖𝑛

2

eg. if 𝑅intr = 1 mm and 𝑚𝑖𝑛 = 4, this gives an effective intrinsic resolution of 4 mm.

Added advantage is compact design.

where 𝑚𝑖𝑛 is minification factor

Rogulski et al., IEEE Trans. Nucl. Sci. 1993.

Detector

Collimator

Slit provides pinhole-type of collimation in the transaxial direction.

Slats provide parallel-hole type of collimation in the axial direction.

In comparison to pinhole collimators, the slit-slat offers better axial coverage and better axial resolution due to the slats.

Conventional slit-slat collimator

20×20cm

10cm

Top view

Lateral view

Transax. FOV coverage

Axial FOV coverage

Collimator Design (2)


Débora Salvado

Interior slit

Half-slits: shared by adjacent detectors in the ring configuration

Mini-slits instead of long ones: improve angular sampling

Extended slats with interior slit: compactness and resolution improvement

Salvado et al., Conf. Rec. IEEE NSS-MIC 2014.

Novel Mini-Slit-Slat Collimator (MSS)

Mini slits

Mini half-slits

Ring configuration Collimator prototype

Angular Blurring Algorithm

Objective: calculate system matrix 𝑝

Assumes each voxel is a 3D Gaussian kernel (blob)

Calculates the line integrals of the blob within angles 𝜃 and 𝜑 analytically, and applies an angular blurring according to the line of response geometry and PSF

Post-processing: 𝑝 is multiplied by sensitivity factors (collimator apertures) and blurring dependent on the angle of incidence (parallax effect)

Reconstruction


Débora Salvado

Bousse et al., Conf. Rec. IEEE NSS/MIC 2013; Erlandsson et al., Conf. Rec. PSMR 2015.

project

backproject

PROJECTIONS

Advantages: Fast computation due to

analytical description Flexible for evaluation of a

range of collimator geometries

INSERT: SPECT insert for simultaneous SPECT/MRI of the brain Stationary system based on high-resolution detectors and multi-pinhole (pre-clinical) /

slit-slat (clinical) collimators

Summary


Débora Salvado

Clinical system:Available 1st quarter of 2017

Pre-clinical system:Under evaluation tests

Acknowledgements


Débora Salvado

Funding

PhD Fellowship SFRH/BD/88093/2012 NIHR University College London Hospitals

Biomedical Research Centres EC FP7-HEALTH 305311

Members of the consortium for the materials provided.

Thank you for your attention!


Débora Salvado

http://www.insert-project.eu/

INSERT: Challenges in Developing SPECT/MRI€¦ · Introduction PET/MRI Symposium 2 London, 21-23 Sep 2016 Débora Salvado Around 10,000 children and adults are diagnosed with brain

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