Potential of magnetization transfer MRI for target volume definition in patients with non‐small‐cell lung cancer

Abstract

To develop a magnetization transfer (MT) module in conjunction with a single-shot MRI readout technique and to investigate the MT phenomenon in non-small-cell lung cancer (NSCLC) as an adjunct for radiation therapy planning. A total of 10 patients with inoperable NSCLC were investigated using a 1.5T MR scanner. MT ratio (MTR) maps of several slices throughout the tumor were assessed. Each MTR-map was acquired within a short breathhold. Fluorodeoxyglucose positron emission tomography (FDG-PET) investigations were performed in addition to the MRI protocol. A total of 60 structures appearing conspicuous in FDG-PET were compared with structures appearing conspicuous in corresponding MTR maps. Quantification of similarity between both modalities was performed using similarity index calculation. MTR-maps showed different contrast than FDG-PET images. However, structures that appeared conspicuous in FDG-PET images, either by a marked signal enhancement or signal decrease, were found to be similarly present in MTR maps. A mean similarity index of 0.65 was calculated. MTR values of suspected atelectasis were on average lower than MTR values of tumor tissue. The proposed MT-MRI technique provides a high MT efficiency, while being robust and fast enough for breathhold acquisition. The results obtained encourage for further exploration of MT-MRI as an adjunct for radiotherapy planning in NSCLC.