Multimodality Functional Imaging in Radiation Therapy Planning: Relationships between Dynamic Contrast-Enhanced MRI, Diffusion-Weighted MRI, and 18F-FDG PET

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.

Voxel‐wise correlation of positron emission tomography/computed tomography with multiparametric magnetic resonance imaging and histology of the prostate using a sophisticated registration framework

“…The results have demonstrated the association of PET imaging with ground truth histology and given insights into the correlation of mpMRI with PET for a small cohort of patients. The particular advantage of the present study is the refined registration method and the voxel‐level analysis, as only a small number of voxel‐based correlation studies have been carried out previously .…”

“…Previous focal therapy studies have used variable and subjective definitions of tumour volume, such as low apparent diffusion coefficient (ADC) values from diffusion‐weighted imaging (DWI), and a consensus about the best approach is yet to be reached. In addition, there is a lack of knowledge about how mpMRI and PET relate to each other, and only a limited number of studies with either small datasets or no access to ‘ground truth’ histology data have been carried out to quantify these relationships . While it is known that accurate quantification of prostate tumour heterogeneity in mpMRI and PET needs to be assessed against histology, these data are not always readily available and it is also challenging to precisely correlate histology with imaging data .…”

Machine learning applications in radiation oncology

“…quantitative MRI allows for values of hypoxia, proliferation and receptor expression [46]. Key predictive values used for radiation oncology outcome models may include patient characteristics (e.g.…”

Bench to bedside molecular functional imaging in translational cancer medicine: to image or to imagine?

“…194e196 Other alternative imaging techniques include MR diffusion, MRS, and ultrasound. MR diffusion imaging and choline MRS have shown promise for imaging apoptosis and response to therapy 197,198 (Fig 7). Lipid proton MRS imaging by measuring mobile lipid signals is associated with changes in tumour apoptosis and necrosis.…”