Role of MRI-Based Functional Imaging in Improving the Therapeutic Index of Radiotherapy in Cancer Treatment

Abstract

Advances in radiation technology, such as intensity-modulated radiation therapy (IMRT), have largely enabled a biological dose escalation of the target volume (TV) and reduce the dose to adjacent tissues or organs at risk (OARs). However, the risk of radiation-induced injury increases as more radiation dose utilized during radiation therapy (RT), which predominantly limits further increases in TV dose distribution and reduces the local control rate. Thus, the accurate target delineation is crucial. Recently, technological improvements for precise target delineation have obtained more attention in the field of RT. The addition of functional imaging to RT can provide a more accurate anatomy of the tumor and normal tissues (such as location and size), along with biological information that aids to optimize the therapeutic index (TI) of RT. In this review, we discuss the application of some common MRI-based functional imaging techniques in clinical practice. In addition, we summarize the main challenges and prospects of these imaging technologies, expecting more inspiring developments and more productive research paths in the near future.

Clinical implementation of magnetic resonance imaging simulation for radiation oncology planning: 5 year experience

“…Implementing an MR-planning program is the first step in the shift from CT-guided to fully MR-guided radiation therapy, and advantages could include integrating functional MR images and artificial intelligence (AI) to use image texture analysis and develop biomarkers to predict response before and during treatment [33,34]. It is hypothesized that these types of MR data could be utilized, for example, to adapt radiation dose during treatment depending on tumour response, for example, delivering higher doses to radioresistant regions and lower doses to the radiosensitive segments, an approach known as dose painting [35][36][37].…”

Biological target volume based on fluorine-18-fluorode-oxyglucose positron emission tomography/computed tomography imaging: a spurious proposition?

“…While the dormant tumor cells are not exactly the region of high FDG uptake, the region of SUV50%max isocontour for dose escalation was not consistent with the local recurrent lesion in our research. In addition, functional imaging modalities include 18 F-FDG-PET/CT and MRI-based functional imaging techniques such as diffusion-weighted imaging (DWI) and intravoxel incoherent motion DWI (IVIM-DWI) [ 7 ]. PET and DWI are both potential candidates for determining the BTV within the GTV for dose painting and escalation in HNC.…”

“…Traditional target volume delineation of nasopharyngeal tumors mainly relies on CT and MRI images, which are merely based on anatomical structure [ 7 ]. Functional imaging can help determine the biological characteristics and predict the radiotherapy sensitivity in different regions of the tumor; therefore, it has been gradually applied to contouring the gross target volume (GTV) [ 8 , 9 ].…”

Development and benchmarking diffusion magnetic resonance imaging analysis for integration into radiation treatment planning

“…44 In head and neck tumors, combined with PET and other conventional imaging modalities DWI increases diagnostic accuracy and early identification of nodal metastasis that cannot be otherwise visualized. 15,45 In addition, for prostate cancer, treatment plans of dose painting based on ADCto-Gleason score mappings have been shown to have the potential to increase the probability of tumor control with the most impactful factor being the positional ADC accuracy onto anatomical images. 9,46 The meaningful interpretation and clinical utility of diffusion imaging sequences have been challenged by the lack of standardization of imaging acquisition as well as the inaccuracy of parameter calculation especially in the absence of fit quality in vendor-provided parameter maps.…”