B1 Power Modification for Amide Proton Transfer Imaging in Parotid Glands: A Strategy for Image Quality Accommodation and Evaluation of Tumor Detection Feasibility

Simple Summary Amide proton transfer weighted (APTw) imaging is a contrast-free molecular imaging method based on the chemical exchange saturation transfer (CEST) technique, initially applied and explored in brain cancers. Previous studies of APTw imaging in the head and neck area have applied APTw protocols in the brain, and hyperintensity artifacts remain a problem to solve. A total of 32 lesions and 30 parotid glands were involved in this research to address the effect of B1 power modification on improving APTw imaging quality in parotid tumor identification, aiming to minimize hyperintensity artifacts. We found that hyperintensity artifacts declined with B1 power decreasing, and combinations of different APTw sequences could improve tumor detection feasibility compared to one APTw sequence. Our findings in this research could give an insight into APTw imaging quality improvement in the head and neck area, which might help the noninvasive diagnosis of parotid tumors in the future.Abstract Background: In the application of APTw protocols for evaluating tumors and parotid glands, inhomogeneity and hyperintensity artifacts have remained an obstacle. This study aimed to improve APTw imaging quality and evaluate the feasibility of difference B1 values to detect parotid tumors. Methods: A total of 31 patients received three APTw sequences to acquire 32 lesions and 30 parotid glands (one patient had lesions on both sides). Patients received T2WI and 3D turbo-spin-echo (TSE) APTw imaging on a 3.0 T scanner for three sequences (B1 = 2 mu T, 1 mu T, and 0.7 mu T in APTw 1, 2, and 3, respectively). APTw image quality was evaluated using four-point Likert scales in terms of integrity and hyperintensity artifacts. Image quality was compared between the three sequences. An evaluable group and a trustable group were obtained for APTmean value comparison. Results: Tumors in both APT2 and APT3 had fewer hyperintensity artifacts than in APT1. With B1 values decreasing, tumors had less integrity in APTw imaging. APTmean values of tumors were higher than parotid glands in traditional APT1 sequence though not significant, while the APTmean subtraction value was significantly different. Conclusions: Applying a lower B1 value could remove hyperintensity but could also compromise its integrity. Combing different APTw sequences might increase the feasibility of tumor detection.