Repetitive MRI of organs at risk in head and neck cancer patients undergoing radiotherapy

Abstract

With emerging technical advances like real-time MR imaging during radiotherapy (RT) with an integrated MR linear accelerator, it will soon be possible to analyze changes in the organs at risk (OARs) during radiotherapy without additional effort for the patients. Until then, patients have to undergo additional MR imaging and often without the same immobilization devices as used for radiotherapy. Consequently, studies with repetitive MRI during the course of radiotherapy are rare, with low patient numbers and with the challenge of registration between the different MR sequences and the varying imaging time points. This review focuses on studies with at least two MRIs, one before and another either during or post-RT, in order to report on RT-induced changes in normal tissues and their correlation with toxicity. We therefore included clinical studies published in English until March 2019, with repetitive MRI of OARs in head and neck cancer patients receiving external beam radiotherapy. OARs analyzed were salivary glands, musculoskeletal structures and bones. MR sequences used included T1, T2, dynamic contrast enhanced (DCE) imaging, diffusion-weighted imaging (DWI), DIXON and MR sialography.

18FDG Positron Emission Tomography Mining for Metabolic Imaging Biomarkers of Radiation-induced Xerostomia in Patients with Oropharyngeal Cancer

“…This was valid for nearly all dose levels, showing that even after very small radiation doses a change in SUV can still be detected. One possible explanation of the decrease in median SUV is the reduction in acinar cells [16-19] with simultaneous increase of intercellular water or fat, which can be visualized in magnetic resonance imaging (MRI) by an increase in T2 [20, 21] or ADC [22], and a rising fat fraction in DIXON MRI. [20] The direct negative correlation between ADC and FDG uptake [23] has been confirmed in several studies using a simultaneous PET/MR in pre-treatment HNC [24], lung cancer [25], lymphoma [26], and liver metastases [27] or post-RT as in rectal cancer [28] and retroperitoneal fibrosis.…”

“…From MRI studies, we know that recovery of the parotid glands, measured as percent changes in volume or ADC values, most probably occurs after 6-8 months from end of RT. [22]…”

MR-Guided Radiotherapy for Head and Neck Cancer: Current Developments, Perspectives, and Challenges

“…Especially DWI is a promising candidate as a prognostic imaging biomarker in HNC (25,(27)(28)(29)(30)(31), but with still conflicting results depending on the parameters analyzed (32). Moreover, early changes in quantitative MR parameters in OAR such as parotid glands may help to predict late toxicity like xerostomia, enabling therapeutic interventions or plan adaptations (33,34). Thus, MR-Linacs with their capability of longitudinal DWI, may facilitate a biologically adaptive treatment, depending on therapy response for tumors and/or OARs (35).…”

Image guidance in radiation therapy for better cure of cancer

“…The objective of this database is to generate clinical and imaging data to evaluate treatment outcome and to act as a repository for evaluation and training. Clinical trials currently explore the benefits of MRguided RT in patients with cancers of the liver, esophagus, bladder, brain, lung, rectum, head and neck, prostate and breast as well as in oligometastatic disease (OMD) [37][38][39][40][41][42][43][44][45][46].…”