Amide proton transfer‐weighted imaging of the head and neck at 3 T: a feasibility study on healthy human subjects and patients with head and neck cancer

Abstract

The aim of this study was to explore the feasibility and repeatability of amide proton transfer weighted (APTw) MRI for the head and neck on clinical MRI scanners. Six healthy volunteers and four patients with head and neck tumors underwent APTw-MRI scanning at 3T. The APTw signal was quantified by the asymmetric magnetization transfer ratio (MTRasym) at 3.5 ppm. Z-spectra of normal tissues in the head and neck (masseter muscle, parotid glands, submandibular glands and thyroid glands) were analyzed in healthy volunteers. Inter-scan repeatability of APTw-MRI was evaluated in six healthy volunteers. Z-spectra of head and neck tumor patients were produced and APTw signals in these tumors were analyzed. APTw-MRI scanning was successful for all ten subjects. The parotid glands showed the highest APTw signal (~7.6% averagely), while the APTw signals in other tissues were relatively moderate. The repeatability of APTw signals from the masseter muscle, parotid gland, submandibular gland and thyroid gland of healthy volunteers was established. Four head and neck tumors showed positive mean APTw ranging from 1.2% to 3.2%, distinguishable from surrounding normal tissues. APTw-MRI was feasible for the use in the head and neck regions at 3T. The preliminary results on patients with head and neck tumors indicated the potential of APTw-MRI for clinical applications.

Chemical exchange saturation transfer (CEST) MR technique for in-vivo liver imaging at 3.0 tesla

“…The actual water resonance was assumed to be at the frequency associated with the lowest intensity of the fitted Z-spectrum. Then, the interpolated Z-spectrum was shifted to the 0 ppm of the offset axis to correct for the field heterogeneity ΔB 0 [11]. The magnitude of the CEST effect was quantified as a magnetization transfer asymmetry ratio (MTR asym ): $${\mathit{MTR}}_{\mathit{asym}}false(\mathrm{normal\Delta }\mathrm{normal\Omega }false)=\frac{Sfalse(-\mathrm{normal\Delta }\mathrm{normal\Omega }false)}{S_0}-\frac{Sfalse(\mathrm{normal\Delta }\mathrm{normal\Omega }false)}{S_0}$$where ΔΩ denotes the shift difference between irradiation frequency and the water resonance, and S and S 0 are the saturated and nonsaturated image intensities, respectively.…”

Downfield‐NOE‐suppressed amide‐CEST‐MRI at 7 Tesla provides a unique contrast in human glioblastoma

“…For these protein ST effects, several interesting correlations have been shown that might play a role in vivo and especially in pathologies: dependence on intracellular pH (5,(10)(11)(12)(13), protein concentration (8,13), or protein folding (14,15) and aggregation states (16). Already, the use for brain tumor detection (6,(17)(18)(19)(20), grading (21), and possible differentiation of tumor recurrence and radiation necrosis (22) has been shown to be feasible by proteinbased saturation transfer MRI.…”

Molecular MRI differentiation between primary central nervous system lymphomas and high-grade gliomas using endogenous protein-based amide proton transfer MR imaging at 3 Tesla

“…The significance of using APT imaging is that the MRI contrast at the cellular protein level is achieved indirectly through the bulk water signal used in daily imaging. Many encouraging results have been reported by different research groups, regarding promising APT-weighted (APTW) signals as image biomarkers for brain tumours [22–27] and other cancers in the prostate, breast, and neck [28–31], and for cerebral ischemia [32–34], Parkinson’s disease [35], and ventral hernia [36]. To the best of our knowledge, PCNSLs have never been studied with APT imaging, and the APT-MRI parameters have also not been quantitatively compared between PCNSLs and HGGs.…”