simulation of hypoxia pet tracer dynamics based on tumour tissue microsections

Simulation of hypoxia PET tracer dynamics based on tumour tissue

microsections

Molecular Imaging in Radiation Oncology

Brussels, 18 – 20 March 2010

David MönnichSection for Biomedical Physics, Radiooncological Clinic, Tübingen

Introduction

Dose distribution can be tailored by IMRT (Dose Painting)

Hypoxia PET imaging with [18F]-FMISO

Dynamic PET imaging: Voxel-wise Time Activity Curves (TACs)

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Larynx carcinoma,FMISO PET 4 h p.i.

TACs

Objective

Link PET voxel signals to the underlying tumour microstructure

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Creating vascular maps from tumour microsections

Extracted vascular map

Regions with different vascular fractions (VF)

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Courtesy of E. Troost, UMC Nijmegen

Blue: Endothelium Red: Proliferation Green: Hypoxia

3.9

mm

Low VF (1.0%)

Interm. VF (3.4%)

High VF (14.5%)

Model & Simulation Method

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Solve oxygen reaction-diffusion equation

Static oxygen distribution

Model & Simulation Method

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Solve oxygen reaction-diffusion equation

Increase

Necrotic regime

Static oxygen distribution

Model & Simulation Method

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Solve oxygen reaction-diffusion equation Solve FMISO

reaction-diffusion equation

Increase

Necrotic regime

Static oxygen distribution

Tracer supply to hypoxic areas is diffusion limited

FMISO binding is not hypoxia specific in the first 15 minutes

Results

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3.8

mm

Tracer supply to hypoxic areas is diffusion limited

FMISO binding is not hypoxia specific in the first 15 minutes

Results

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3.8

mm

Results

TACs from differently perfused regions

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Results

TACs from differently perfused regions

Different microstructure can lead to similar late signal

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Summary and conclusion

Summary● FMISO supply to hypoxic regions is limited by molecular

diffusion speed on relevant time scales● Different tissue microstructure can lead to similar voxel

activitiy in static PET images

Conclusion● Dose painting using static images might omit hazardous

tumour regions● Imaging of perfusion seems necessary in addition to

static hypoxia imaging

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