A Method for Manufacturing Oncological Phantoms for the Quantification of 18F-FDG PET and DW-MRI Studies.

Francesca Gallivanone,Matteo Interlenghi,Maurizia Baldi,Irene Carne,Daniele Fantinato,Isabella Castiglioni,Daniela D’Ambrosio

doi:10.1155/2017/3461684

Abstract

The aim of this work was to develop a method to manufacture oncological phantoms for quantitation purposes in 18F-FDG PET and DW-MRI studies. Radioactive and diffusion materials were prepared using a mixture of agarose and sucrose radioactive gels. T2 relaxation and diffusion properties of gels at different sucrose concentrations were evaluated. Realistic oncological lesions were created using 3D-printed plastic molds filled with the gel mixture. Once solidified, gels were extracted from molds and immersed in a low-radioactivity gel simulating normal background tissue. A breast cancer phantom was manufactured using the proposed method as an exploratory feasibility study, including several realistic oncological configurations in terms of both radioactivity and diffusion. The phantom was acquired in PET with 18F-FDG, immediately after solidification, and in DW-MRI the following day. Functional volumes characterizing the simulated BC lesions were segmented from PET and DW-MRI images. Measured radioactive uptake and ADC values were compared with gold standards. Phantom preparation was straightforward, and the time schedule was compatible with both PET and MRI measurements. Lesions appeared on 18F-FDG PET and DW-MRI images as expected, without visible artifacts. Lesion functional parameters revealed the phantom's potential for validating quantification methods, in particular for new generation hybrid PET-MRI systems.

Highlights

In vivo molecular imaging techniques, such as Computed Tomography (CT), Positron Emission Tomography (PET), and Magnetic Resonance Imaging (MRI)—in particular Diffusion Weighted MRI (DW-MRI)—are commonly used for the diagnosis, prognosis, and therapy monitoring of many diseases
Quantification strategies to extract biomarkers from in vivo molecular imaging techniques need to be validated in order to evaluate their performance, accuracy, and robustness, while comparing the values obtained by the application of image processing with actual values
Our procedure for phantom preparation was straightforward, and the time schedule was compatible in particular with PET measurements, since the time required for gel solidification varied from a few minutes to half an hour depending on gel quantity

Summary

Introduction

In vivo molecular imaging techniques, such as Computed Tomography (CT), Positron Emission Tomography (PET), and Magnetic Resonance Imaging (MRI)—in particular Diffusion Weighted MRI (DW-MRI)—are commonly used for the diagnosis, prognosis, and therapy monitoring of many diseases. These techniques are inherently quantitative; advanced image processing methods for extracting quantitative parameters have been developed for use as surrogate disease biomarkers. At a first level, the evaluation of quantitative strategies for volume and shape descriptors could be performed on patient data by comparison with qualitative features and manual contouring defined by a physician, this validation strategy is suboptimal. Both qualitative evaluations of shape descriptors and manual contouring are operatordependent, not ensuring an accurate GS for validation

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