Diffusion-weighted MR imaging (DWI) using TRacking Only Navigator echo (TRON): initial clinical evaluation and comparison to respiratory triggered and free breathing DWI

Introduction Diffusion-weighted MR imaging (DWI) is an emerging technique for the detection and characterization of liver lesions [1]. Two types of non-breathhold DWI are used in clinical practice: respiratory triggering (RT) and free breathing (FB). However, RT DWI suffers from a prolonged examination time, while FB DWI may suffer from image blurring [1]. Recently, the limitations of both RT and FB DWI have been overcome by the introduction of TRacking Only Navigator echo (TRON) [2, 3]. TRON uses a navigator echo for continuous real-time slice tracking and does not use any gating window; consequently, scan time is not prolonged and image blurring is reduced [2, 3]. So far, TRON has only been evaluated in healthy volunteers, and not in a clinical setting. It is still unknown how TRON compares to RT and FB DWI with regard to conspicuity and apparent diffusion coefficient (ADC) measurements of liver lesions. The purpose of this study was therefore to assess conspicuity and ADCs of liver metastases in TRON, compared to RT and FB DWI.