Kalium-39-NMR in-vivo am Menschen bei 7Tesla: 39K-MR-Bildgebung und Auflösung der Quadrupolaufspaltung der 39K-Resonanz

In dieser Arbeit wurde die Machbarkeit der In-vivo-39K-MR-Bildgebung am menschlichen Oberschenkel sowie am Kopf mit einer nominellen Auflösung von 1 cm3 in einer Messzeit von 30 min bei einer Grundmagnetfeldstärke von 7T gezeigt. Zur Optimierung der Sequenzparameter wurden sowohl die globalen Relaxationszeitkonstanten bestimmt. In Untersuchungsregionen mit hohem Muskelanteil, wie im Ober- und Unterschenkel, ist die Resonanz von 39K in ein Triplett aufgespalten. Die beiden Satellitenresonanzen sind etwa achsensymmetrisch zur Zentralresonanz. Der Betrag ihrer Frequenzverschiebung ist vom Winkel zwischen dem Bein und dem statischen Magnetfeld B0 abhängig. Bei zu B0 paralleler Ausrichtung des Beins sind die Satellitenresonanzen gegenüber der zentralen Resonanz etwa um 200 Hz verschoben. Der Empfang von 39K-Signal nach Doppelquantenfilterung mit magic angle Anregung stützt die These, dass die 39K-Resonanz im Muskelgewebe aufgrund der Wechselwirkung mit einem nicht fluktuierenden elektrischen Feldgradienten in einer anisotropen Umgebung aufgespalten ist

Advances in MRI of the myelin bilayer

Myelin plays a key role in the function of the central nervous system and is involved in many neurodegenerative diseases. Hence, depiction of myelin is desired for both research and diagnosis. However, MRI of the lipid bilayer constituting the myelin membrane is hampered by extremely rapid signal decay and cannot be accomplished with conventional sequences. Dedicated short-T2 techniques have therefore been employed, yet with extended sequence timings not well matched to the rapid transverse relaxation in the bilayer, which leads to signal loss and blurring. In the present work, capture and encoding of the ultra-short-T2 signals in the myelin bilayer is considerably improved by employing advanced short-T2 methodology and hardware, in particular a high-performance human-sized gradient insert. The approach is applied to tissue samples excised from porcine brain and in vivo in a human volunteer. It is found that the rapidly decaying non-aqueous components in the brain can indeed be depicted with MRI at useful resolution. As a considerable fraction of these signals is related to the myelin bilayer, the presented approach has strong potential to contribute to myelin research and diagnosis

Blood Glucose Homeostasis in the Course of Partial Pancreatectomy--Evidence for Surgically Reversible Diabetes Induced by Cholestasis.

Partial pancreatic resection is accompanied not only by a reduction in the islet cell mass but also by a variety of other factors that are likely to interfere with glucose metabolism. The aim of this work was to characterize the patient dynamics of blood glucose homeostasis during the course of partial pancreatic resection and to specify the associated clinico-pathological variables.In total, 84 individuals undergoing elective partial pancreatic resection were consecutively recruited into this observational trial. The individuals were assigned based on their fasting glucose or oral glucose tolerance testing results into one of the following groups: (I) deteriorated, (II) stable or (III) improved glucose homeostasis three months after surgery. Co-variables associated with blood glucose dynamics were identified.Of the 84 participants, 25 (30%) displayed a normal oGTT, 17 (20%) showed impaired glucose tolerance, and 10 (12%) exhibited pathological glucose tolerance. Elevated fasting glucose was present in 32 (38%) individuals before partial pancreatic resection. Three months after partial pancreatic resection, 14 (17%) patients deteriorated, 16 (19%) improved, and 54 (64%) retained stable glucose homeostasis. Stability and improvement was associated with tumor resection and postoperative normalization of recently diagnosed glucose dysregulation, preoperatively elevated tumor markers and markers for common bile duct obstruction, acute pancreatitis and liver cell damage. Improvement was linked to preoperatively elevated insulin resistance, which normalized after resection and was accompanied by a decrease in fasting- and glucose-stimulated insulin secretion.Surgically reversible blood glucose dysregulation diagnosed concomitantly with a (peri-) pancreatic tumor appears secondary to compromised liver function due to tumor compression of the common bile duct and the subsequent increase in insulin resistance. It can be categorized as "cholestasis-induced diabetes" and thereby distinguished from other forms of hyperglycemic disorders

High‐resolution MRI of mummified tissues using advanced short‐T2 methodology and hardware

Purpose: Evolutionary medicine aims to study disease development from a long-term perspective, and through the analysis of mummified tissue, timescales of several thousand years are unlocked. Due to the status of mummies as ancient relics, noninvasive techniques are preferable, and, currently, CT imaging is the most widespread method. However, CT images lack soft-tissue contrast, making complementary MRI data desirable. Unfortunately, the dehydrated nature and short T2 times of mummified tissues render them practically invisible to standard MRI techniques. Specialized short-T2 approaches have therefore been used, but currently suffer severe resolution limitations. The purpose of the present study is to improve resolution in MRI of mummified tissues. Methods: The zero-TE-based hybrid filling technique, together with a high-performance magnetic field gradient, was used to image three ancient Egyptian mummified human body parts: a hand, a foot, and a head. A similar pairing has already been shown to increase resolution and image quality in MRI of short-T2 tissues. Results: MRI images of yet unparalleled image quality were obtained for all samples, reaching isotropic resolutions of 0.6 mm and SNR values above 100. The same general features as present in CT images were depicted but with different contrast, particularly for regions containing embalming substances. Conclusion: Mummy MRI is a potentially valuable tool for (paleo)pathological studies, as well as for investigations into ancient mummification processes. The results presented here show sufficient improvement in the depiction of mummified tissues to clear new paths for the exploration of this field. Keywords: HYFI; ZTE; ancient Egyptian mummy; high resolution; high-performance gradient; short T2

Bar graphs of the pre- and postoperative values for (A) HbA1c, (B) BMI, (C) Ca19-9 and (D) CEA with respect to deteriorated, stable and improved blood glucose homeostasis.

<p>Points: means; error bars: 95% CI; black error bars: preoperative values; broken error bars: postoperative values for each group; reference lines: cut-off/normal values; F- and p-values beneath each diagram: one-sided ANOVA for comparison between the three groups at each time point; and p-values within the diagram: two-sided T-test for paired samples for pre- and post-operative comparisons within the designated group.</p

Distribution of the categorical variables based on the dynamics of blood glucose homeostasis after partial pancreatectomy.

<p>Distribution of the categorical variables based on the dynamics of blood glucose homeostasis after partial pancreatectomy.</p

Bar graphs of the pre- and postoperative values for (A) amylase, (B) lipase, (C) γGT, (D) bilirubin, (E) ALAT and (F) ASAT with respect to deteriorated, stable and improved blood glucose homeostasis.

<p>Points: means; error bars: 95% CI; black error bars: preoperative values; broken error bars: postoperative values for each group; reference lines: cut-off/normal values; F- and p-values beneath each diagram: one-sided ANOVA for comparison between the three groups at each time point; and p-values within the diagram: two-sided T-test for paired samples for pre- and post-operative comparisons within the designated group.</p

A high-performance gradient insert for rapid and short-T2 imaging at full duty cycle

Purpose The goal of this study was to devise a gradient system for MRI in humans that reconciles cutting‐edge gradient strength with rapid switching and brings up the duty cycle to 100% at full continuous amplitude. Aiming to advance neuroimaging and short‐T2 techniques, the hardware design focused on the head and the extremities as target anatomies. Methods A boundary element method with minimization of power dissipation and stored magnetic energy was used to design anatomy‐targeted gradient coils with maximally relaxed geometry constraints. The design relies on hollow conductors for high‐performance cooling and split coils to enable dual‐mode gradient amplifier operation. With this approach, strength and slew rate specifications of either 100 mT/m with 1200 mT/m/ms or 200 mT/m with 600 mT/m/ms were reached at 100% duty cycle, assuming a standard gradient amplifier and cooling unit. Results After manufacturing, the specified values for maximum gradient strength, maximum switching rate, and field geometry were verified experimentally. In temperature measurements, maximum local values of 63°C were observed, confirming that the device can be operated continuously at full amplitude. Testing for peripheral nerve stimulation showed nearly unrestricted applicability in humans at full gradient performance. In measurements of acoustic noise, a maximum average sound pressure level of 132 dB(A) was determined. In vivo capability was demonstrated by head and knee imaging. Full gradient performance was employed with echo planar and zero echo time readouts. Conclusion Combining extreme gradient strength and switching speed without duty cycle limitations, the described system offers unprecedented options for rapid and short‐T2 imaging. Magn Reson Med 79:3256–3266, 2018. © 2017 International Society for Magnetic Resonance in Medicine