Abstract
Purpose/Introduction: As a ubiquitous component of all animal tissues, cholesterol has vital structural roles [1, 2]. In this work, the detection of cholesterol is reported for the first time noninvasively in human calf adipose tissue by 13C MRS at 7T, with the J-refocused 1H PRESS localized DEPT sequence combined with broadband decoupling.
Subjects and Methods: A J-refocused 1H PRESS localized DEPT sequence was shown in Fig.1. A 90o RF pulse was inserted in the middle of the double echo PRESS localization part, which reverses the direction of J-coupling evolution
at this point. While J-refocused 1H PRESS substitutes the first 90o pulse of a conventional DEPT experiment, the residual part of the DEPT sequence remains unchanged and was implemented subsequently. The effectiveness of
the suppression of J-modulation was investigated by comparing glutamate spectra obtained with and without J-refocusing pulse at different TE times.
To detect lipids in the calf adipose tissue, the sequence was applied on a 7T Philips Achiena MRI system using a quadrature dual-tuned 13C/1H partial volume extremity coil.
Results: As demonstrated from the glutamate phantom, an effective suppression of J modulation by the J-refocusing pulse is achieved when TE is less than 80ms as shown in Fig. 2. Natural abundance 13C MR spectra acquired with
the proposed sequence from the left calf of two healthy subjects are shown in Fig. 3. Eight well established peak assignments are labelled in green with their chemical shifts marked in black which are in agreement with literature values (Table 1). In addition, there are also five obvious peaks observed in both subjects consistently across all measurements, which have not been reported
yet. The three peaks marked in yellow are tentatively assigned to cholesterol in accordance to literature values [6, 7]. The other two peaks in blue are assigned to the allylic carbon atoms C13 trans and C18 respectively (Table 1) [3, 4, 5].
