Feasibility evaluation of amide proton transfer-weighted imaging in the parotid glands: a strategy to recognize artifacts and measure APT value

Abstract

Background: The feasibility and image quality of three-dimensional (3D) amide proton transfer (APT)weighted (APTw) in parotid tumor lesions have not been well established in previous studies. This study aimed to evaluate the utility of APT imaging in parotid lesions and glands.Methods: Patients with parotid lesions received 3D turbo spin echo (TSE) APTw on a 3.0T scanner. Two radiologists, who were blinded to the clinical data, independently evaluated the APTw image quality using 4-point Likert scales (1= poor, 4= excellent) in terms of integrity and hyperintensity artifacts. An image quality selection protocol was built based on the two scores. Evaluable images (integrity score >1) and trustable images (integrity score >3 and hyperintensity artifacts score >2) were then enrolled for APTw value comparison between parotid lesions and glands.Results: Forty consecutive patients were included in this study. Four patients were excluded due to severe motion (n=3) or dental (n=1) artifacts, and 36 patients received the APT sequence. Among these, more parotid tumor lesions (34/36, 94.4%) than normal parotid glands (23/31, 74.2%) revealed excellent integrity scores (score =4) (P=0.034). Most parotid tumor lesions (24/34, 70.6%) and glands (16/28, 57.1%) revealed no or little hyperintensity artifacts for diagnosis (scores 3 and 4). APT values of parotid lesions and glands in the evaluable groups were 2.11%±1.15% and 1.60%±1.56%, respectively, and the difference was not significant (P=0.197). APT values of parotid lesions and glands in the trustable groups were 1.99%±1.18% and 1.03%±1.09%, respectively, and the difference was statistically significant (P=0.018).Conclusions: 3D APTw could be used to differentiate parotid tumors and normal parotid glands; however, the technology still needs to be improved to remove artifacts. In our study, most APTw images of tumor lesions in parotid glands had acceptable image quality, and these APTw images are feasible for diagnostic use.

Sensitivity and specificity of amide proton transfer-weighted imaging for assessing programmed death-ligand 1 status in non-small cell lung cancer: a comparative study with intravoxel incoherent motion and 18F-FDG PET

“…As a relatively novel MRI molecular imaging method, APTWI presents semiquantitative amide proton maps describing the heterogeneous metabolism of mobile proteins and peptides that can reflect the histopathological and genetic changes in tumors ( 16 , 17 , 39 ). Previous work has shown that higher APTWI signals indicate a high level of mobile protein and peptide metabolism, which was associated with more active cell proliferation, more microscopic necrosis ( 40 ), greater microvascular density ( 41 ), and an appropriate pH level ( 42 ). In the present investigation, compared to NSCLC patients who were PD-L1 negative, NSCLC patients who were PD-L1 positive had higher MTRasym (3.5 ppm) values, most likely due to active tumor cell proliferation ( 13 , 14 ), more necrosis ( 10 ), and higher microvascular density ( 29 , 30 ).…”

A Brief History and Future Prospects of CEST MRI in Clinical Non-Brain Tumor Imaging

“…Therefore, a fast image readout was chosen, such as echo planar imaging (EPI), rapid imaging with refocused echoes (RARE), fast spin echo (FSE), and/or fast imaging with steady-state precession (FISP) [ 6 , 34 , 35 , 36 ]. As shown in Table 1 , out of the three papers on liver and the two on lung, four used FSE [ 74 , 75 , 81 , 82 ] and one used EPI [ 73 ]. Besides a fast readout, respiration-gated design [ 81 , 82 ] or breath holding [ 73 , 74 ] are still required to reduce motion during acquisition.…”

“…Yuan et al [ 79 ] also found that APTw MRI was feasible for use in the head and neck regions at 3 T in clinical applications. Chen et al [ 75 ] found that most APTw images of tumor lesions in parotid glands had an acceptable image quality ( Figure 7 ), hence were feasible for diagnostic use.…”

“…The arrows mean APTw values in ROI. Reproduced with permission from AME 2021 (DOI: 10.21037/qims-20-675) [ 75 ].…”

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

“…In most APTw studies of parotid cancers, the APT protocol recommended for brain cancers (B1 = 2 μT, saturation time = 0.8~2 s) has been applied [ 13 , 24 , 26 , 27 ]. However, although this power and saturation time guarantee homogeneity in most normal brain areas, when applied to the parotid region, inhomogeneity and hyperintensity artifacts in PG and PT remain a hindrance [ 28 , 29 ]. APTw studies in the brain have demonstrated that lower B1 could lessen hyperintensity artifacts [ 30 ].…”