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Disputation Hen Amit Morik

08.07.2022 | 12:00
Thema der Dissertation:
Accelerated Magnetization Encoding for Reversibly Bound, Hyperpolarized Xenon in Molecular Host-Guest Systems
Abstract: Magnetic resonance imaging (MRI) was used for the simultaneous acquisition of multi-sample spectra from Xe-binding host molecules. These spectra obtained by the method of chemical exchange saturation transfer with hyperpolarized xenon (Xe HyperCEST). The method’s high sensitivity overcomes challenges for the conventional MR spectroscopy in distinguishing structurally similar hosts. However, the method is slow since it demands repeating measurements along a spectral dimension and might also demand averaging to increase the image SNR. To accelerate image acquisitions of Xe HyperCEST, a novel method called CAVKA (combined approach of variable flip angle (VFA), keyhole and averaging) was introduced. The undersampling approach called keyhole together with VFA excitations allow optimized use of the available Xe magnetization to acquire a series of low-resolution images with enhanced signal of multiple samples. These are then computationally merged with a full-resolution image that benefits from low noise level as the result of applying averaging. The reuse of this single averaged image provides a meaningful acceleration (with only minor errors) compared to averaging of all the images in the series.
Application of the CAVKA method in the molecular host-guest system of cucurbit[7]uril (CB7) and multiple guests (cis-1,4-Bis(aminomethyl)cyclohexane, cadaverine and putrescine) revealed that commercially available CB7 contains an unexpectedly high amount of a CB6 impurity that was quantitatively estimated to be 8.5% through evaluation of Xe HyperCEST spectra. Furthermore, CB7 does not yield a resolved CEST response. Instead, rapid interactions between Xe and CB7 manifest in the spectrum and could be suppressed by the guest cis-1,4-Bis(aminomethyl)cyclohexane.

Zeit & Ort

08.07.2022 | 12:00

Hörsaal B (0.1.01)
Fachbereich Physik, Arnimallee 14, 14195 Berlin