The emerging potential of magnetic resonance imaging in personalizing radiotherapy for head and neck cancer: an oncologist's perspective

Abstract

Head and neck cancer (HNC) is a challenging tumour site for radiotherapy delivery owing to its complex anatomy and proximity to organs at risk (OARs) such as the spinal cord and optic apparatus. Despite significant advances in radiotherapy planning techniques, radiation-induced morbidities remain substantial. Further improvement would require high-quality imaging and tailored radiotherapy based on intratreatment response. For these reasons, the use of MRI in radiotherapy planning for HNC is rapidly gaining popularity. MRI provides superior soft-tissue contrast in comparison with CT, allowing better definition of the tumour and OARs. The lack of additional radiation exposure is another attractive feature for intratreatment monitoring. In addition, advanced MRI techniques such as diffusion-weighted, dynamic contrast-enhanced and intrinsic susceptibility-weighted MRI techniques are capable of characterizing tumour biology further by providing quantitative functional parameters such as tissue cellularity, vascular permeability/perfusion and hypoxia. These functional parameters are known to have radiobiological relevance, which potentially could guide treatment adaptation based on their changes prior to or during radiotherapy. In this article, we first present an overview of the applications of anatomical MRI sequences in head and neck radiotherapy, followed by the potentials and limitations of functional MRI sequences in personalizing therapy. INTRODUCTIONRadical radiotherapy (RT) is integral to the management of head and neck cancer (HNC) in both the primary and adjuvant settings. Advances in computer-assisted radiological techniques over the past two decades have in turn revolutionized radiotherapy planning. Development of advanced radiotherapy planning techniques such as intensity-modulated radiotherapy (IMRT) and volumetricmodulated arc therapy have allowed for better dose conformation to the tumour target and sparing of surrounding normal tissues. HNC was one of the first tumour sites where IMRT was widely implemented owing to a significant reduction in radiation-induced xerostomia in comparison with three-dimensional conformal planning.

MRI features of presumed normal palatine tonsils in dogs

“…, Wong et al . ). It has been demonstrated that MRI is superior to CT in characterising local tumour extent, bone marrow involvement and detection of perineural spread (Law et al .…”

“…Studies in human medicine have underlined the benefit of MRI in head and neck radiotherapy planning with improvement of tumour delineation and reduction in interobserver variations compared with CT (Wong et al . ).…”

“…In human medicine, MRI is commonly used in the investigation of tonsillar disease including oral-oropharyngeal squamous cell carcinoma and nasopharyngeal carcinoma (Olmi et al 1995, Bolzoni et al 2004, Law et al 2011. MRI is also increasingly used for defining the extent of tumour invasion into adjacent soft tissues in oropharyngeal neoplasia (Lenz et al 2000, Liao et al 2008, Wong et al 2017. It has been demonstrated that MRI is superior to CT in characterising local tumour extent, bone marrow involvement and detection of perineural spread (Law et al 2011).…”

Diffusional kurtosis imaging in head and neck cancer: On the use of trace‐weighted images to estimate indices of non‐Gaussian water diffusion

“…In this regard, functional MRI techniques, such as diffusion‐ as well as perfusion‐MRI, could have an important role, as they can provide several quantitative indices strictly related to tissue cellular density, vascular perfusion, and tumor heterogeneity . These indices represent distinctive tumor signatures with radiobiological relevance that could guide treatment optimization and personalization . However, the integration of functional MRI techniques into clinical practice is currently limited by the lack of standardized acquisition protocols and image analysis methods, hindering the robust validation of personalized oncological approaches.…”

Quantitative analysis of image quality for acceptance and commissioning of an MRI simulator with a semiautomatic method

“…Developments in radiotherapy require precise MRI images for target and normal tissue delineation, characterizing tumor features, and monitoring treatment response during and after radiotherapy 4, 5. MRI simulation is a relatively new technique for radiotherapy 6, 7.…”