Multimodality functional imaging in radiation therapy planning: relationships between dynamic contrast-enhanced MRI, diffusion-weighted MRI, and 18F-FDG PET.

Moisés Mera Iglesias,Antonio López Medina,José Luis Del Olmo Claudio,José L Alba Castro,Iago Landesa-Vázquez,Catherine Coolens,David Aramburu Núñez,Victor Muñoz,Francisco Salvador Gómez,Brandon Driscoll

doi:10.1155/2015/103843

Abstract

Objectives. Biologically guided radiotherapy needs an understanding of how different functional imaging techniques interact and link together. We analyse three functional imaging techniques that can be useful tools for achieving this objective. Materials and Methods. The three different imaging modalities from one selected patient are ADC maps, DCE-MRI, and 18F-FDG PET/CT, because they are widely used and give a great amount of complementary information. We show the relationship between these three datasets and evaluate them as markers for tumour response or hypoxia marker. Thus, vascularization measured using DCE-MRI parameters can determine tumour hypoxia, and ADC maps can be used for evaluating tumour response. Results. ADC and DCE-MRI include information from 18F-FDG, as glucose metabolism is associated with hypoxia and tumour cell density, although 18F-FDG includes more information about the malignancy of the tumour. The main disadvantage of ADC maps is the distortion, and we used only low distorted regions, and extracellular volume calculated from DCE-MRI can be considered equivalent to ADC in well-vascularized areas. Conclusion. A dataset for achieving the biologically guided radiotherapy must include a tumour density study and a hypoxia marker. This information can be achieved using only MRI data or only PET/CT studies or mixing both datasets.

Highlights

Radiotherapy is in a process of transformation from imageguided radiotherapy to biologically guided radiotherapy [1]
In the last few years some commercial treatment units have been developed that include an MRI unit combined with a linac in a single device [2,3,4,5], and PET/CT has proven useful for tumour staging and target delineation, especially in head and neck tumours and lung tumour [6,7,8]
In this paper a case study is presented using datasets from 18F-FDG PET/CT, DWMRI/ADC maps, and dynamic contrast-enhanced- (DCE-) MRI for characterizing tumour behaviour and for using the multimodality parameters as predictive values of tumour response from a patient included in the ARTFIBio project [34,35,36]

Summary

Introduction

Radiotherapy is in a process of transformation from imageguided radiotherapy to biologically guided radiotherapy [1] To this effect, in the last few years some commercial treatment units have been developed that include an MRI unit combined with a linac in a single device [2,3,4,5], and PET/CT (positron emission tomography/computed tomography) has proven useful for tumour staging and target delineation, especially in head and neck tumours and lung tumour [6,7,8]. In this paper a case study is presented using datasets from 18F-FDG (fludeoxyglucose labelled with 18F) PET/CT, DWMRI/ADC maps, and dynamic contrast-enhanced- (DCE-) MRI for characterizing tumour behaviour and for using the multimodality parameters as predictive values of tumour response from a patient included in the ARTFIBio project [34,35,36]. The PET enhancement (standard uptake value or SUV) in tumours is due to three different mechanisms: (i) cancer cells produce more ATP outside the mitochondria, even in well-oxygenated conditions (Warburg effect [37]); (ii) cancer cells proliferate more than normal tissue cells [38], and they need more glucose; and, (iii) cancer cells can survive in lower oxygenated regions better than normal tissue cells [39, 40] but consume more glucose because they need to produce ATP by glycolysis in absence of oxygen (Pasteur effect)

Objectives

Methods

Results

Discussion

Conclusion