Novel Pyridinium Cross-Link Structures Derived from Glycolaldehyde and Glyoxal.

Short-chained α-hydroxycarbonyl compounds such as glycolaldehyde (GA) and its oxidized counterpart glyoxal (GX) are known as potent glycating agents. Here, a novel fluorescent lysine-lysine cross-link 1-(5-amino-5-carboxypentyl)-3-(5-amino-5-carboxy-pentylamino)pyridinium salt (meta-DLP) was synthesized and its structure unequivocally proven by 1H NMR, 13C-NMR attached proton test, and 2D NMR. Further characterization of chemical properties and mechanistic background was obtained in comparison to the known monovalent protein modification 2-ammonio-6-(3-oxidopyridinium-1-yl)hexanoate (OP-lysine). Identification and quantitation in various sugar incubations with N2-t-Boc-lysine revealed a novel alternative formation pathway for both advanced glycation end products (AGEs) by the interplay of both carbonyl compounds, GA and GX, which was confirmed by isotope labeling experiments. The concentration of pyridinium AGEs was about 1000-fold lower compared to the well-established N6-carboxymethyl lysine. However, pyridinium AGEs were shown to lead to the photosensitized generation of singlet oxygen in irradiation experiments, which was verified by the detection of 3,3'-(naphthalene-1,4-diyl)-dipropionate endoperoxide. Furthermore, meta-DLP was identified in hydrolyzed potato chip proteins by collision-induced dissociation mass spectrometry after HPLC enrichment.

Speeding up the clinical routine: Compressed sensing for 2D imaging of lumbar spine disc herniation.

PURPOSE: Increasing economic pressure and patient demands for comfort require an ever-increasing acceleration of scan times without compromising diagnostic certainty. This study tested the new acceleration technique Compressed SENSE (CS-SENSE) as well as different reconstruction methods for the lumbar spine. METHODS: In this prospective study, 10 volunteers and 14 patients with lumbar disc herniation were scanned using a sagittal 2D T2 turbo spin echo (TSE) sequence applying different acceleration factors of SENSE and CS-SENSE. Gradient echo (GRE), autocalibration (CS-Auto) and TSE prescans were tested for reconstruction. Images were analysed by two readers regarding anatomical delineation, diagnostic certainty (for patients only) and image quality as well as objectively calculating the root mean square error (RMSE), structural similarity index (SSIM), SNR and CNR. The Friedman test and Chi-squared were used for ordinal, ANOVA for repeated measurements and Tukey Kramer test for continuous data. Cohen's kappawas calculated for interreader reliability. RESULTS: CS-SENSE outperformed SENSE and CS-Auto regarding RMSE (e.g. CS-SENSE 1.5: 43.03 ±â€¯11.64 versus SENSE 1.5: 80.41 ±â€¯17.66; p = 0.0038) and SSIM as well as in the subjective rating for CS-SENSE 3 TSE. In the patient setting image quality was unchanged in all subjective criteria up to CS-SENSE 3 TSE (all p > 0.05) compared to standard T2 with 43 % less scan time while the GRE prescan only allowed a reduction of 32 %. CONCLUSION: Combining a TSE prescan with CS-SENSE enables significant scan time reductions with unchanged ratings for lumbar spine disc herniation making this superior to the currently used SENSE acceleration or GRE reconstructions.

Accelerated MRI of the knee. Quality and efficiency of compressed sensing.

PURPOSE: To evaluate potential clinical acceleration factors of Compressed SENSE (CS)1 in direct comparison with SENSE for fat saturated (fs)2, proton density-weighted (PD)3 2D and 3D sequences of the knee. METHOD: Twenty healthy volunteers were scanned with a 3 T scanner, all receiving a standard, fs 2D PD, three CS (CS 2, CS 3, CS 5) as well as time-equivalent SENSE accelerations (S 2, S 3, S 5). The fs 3D PD sequence was acquired with four CS (CS 6, CS 8, CS 10, CS 15) and equivalent SENSE (S 5.72, S 7.69, S 9.57, S 14) factors. Three independent readers rated the images. Signal-to-noise, contrast-to-noise, root-mean-square error and structural similarity index were analyzed for objective evaluation. RESULTS: Scan time decreased with increasing CS factor (2D CS 2: 145 s, 2D CS 3: 95 s, 2D CS 5: 57 s, 3D CS 6: 293 s, 3D CS 8: 220 s, 3D CS 10: 176 s, 3D CS 15: 119 s). The 2D standard sequence was rated best for diagnostic certainty and overall image impression with an average of 4.97 ±â€¯0.10 and 4.80 ±â€¯0.24 (all p < 0.05), except for 2D CS 2 and 2D S 2. For the 3D sequences, the standard sequence performed better for both parameters for CS 15, S 9.57 and S 4, as well as S 7.69 for overall image impression while CS 8 was non-inferior for all tested criteria and CS 10 only inferior for delineation of the anterior cruciate ligament, both outperforming the time-equivalent SENSE accelerations. CONCLUSION: Compressed SENSE can significantly decrease (34.39 % for 2D CS 2 and 54.17 % for 3D CS 10) scan time in knee imaging with unchanged diagnostic certainty and overall image impression compared to the clinical reference.

Correction to: CT metal artifacts in patients with total hip replacements: for artifact reduction monoenergetic reconstructions and post-processing algorithms are both efficient but not similar.

The original version of this article, published on 03 May 2018, unfortunately contained a mistake. The following correction has therefore been made in the original.

Accelerated MRI of the Lumbar Spine Using Compressed Sensing: Quality and Efficiency.

BACKGROUND: Decreasing MRI scan time is a key factor to increase patient comfort and compliance as well as the productivity of MRI scanners. PURPOSE/HYPOTHESIS: Compressed sensing (CS) should significantly accelerate 3D scans. This study evaluated the clinical application and cost effectiveness of accelerated 3D T2 sequences of the lumbar spine. STUDY TYPE: Prospective, cross-sectional, observational. POPULATION: Twenty healthy volunteers and 10 patients. FIELD STRENGTH/SEQUENCE: A 3D T2 TSE sequence, identical 3D sequences with three different parallel imaging and CS accelerating factors, and 2D TSE sequences as a clinical reference were obtained on a 3T scanner. ASSESSMENT: Three readers evaluated the sequences for delineation of anatomical structures and image quality. A quantitative analysis consisting of root mean square error, structural similarity index, signal-to-noise ratio, and contrast-to-noise ratio were performed. The scan times were used to calculate cost differences for each sequence. STATISTICAL TESTS: An analysis of variance with repeated measurements and the Friedman test were used to test for potential differences between the sequences. Post-hoc analysis was made with the chi-squared and Tukey-Kramer test. RESULTS: CS with factor 4.5 results in unchanged image quality compared to the T2 TSE for volunteers and patients (overall image impression: 4.75 vs. 4.20 [P = 0.73] and 4.90 vs. 4.47 [P = 0.44]). The CS 4.5 scan is 167 seconds (-39%) faster than the 3D and 216.5 seconds (-45%) faster than the 2D sequences. No significant differences was found for the diagnostic certainty in the volunteers and patients between 2D TSE and 3D CS 4.5 (P = 0.89 and P = 0.43). A reduction of scan time to 148 seconds (CS 8) was still rated acceptable for most diagnosis. DATA CONCLUSION: CS accelerates the 3D T2 without compromising image quality. The 3D sequences offer comparable diagnostic quality to the clinical 2D standard with less scan time (-45%), potentially increasing the productivity of MRI scanners. LEVEL OF EVIDENCE: 1 Technical Efficacy: Stage 6 J. Magn. Reson. Imaging 2019;49:e164-e175.

Modification and Cross-Linking of Proteins by Glycolaldehyde and Glyoxal: A Model System.

Highly reactive intermediates of the Maillard reaction, such as glycolaldehyde and glyoxal, are precursors in the modification and cross-linking of proteins. Therefore, we investigated ribonuclease A modified by glycolaldehyde and glyoxal, separately. For the first time, various protein species derived by these aldehydes were successfully separated by ion-exchange chromatography and gel permeation chromatography. Highly cross-linked ribonuclease A was obtained in glycolaldehyde incubations. In contrast, glyoxal predominantly led to modified monomeric protein species. These results were verified by sodium dodecyl sulfate polyacrylamide gel electrophoresis and isoelectric focusing. Quantitation of mono- and bivalent protein modifications of the isolated protein species led to a positive correlation between the degree of protein modification and the change of the isoelectric point and molecular weight, respectively. Glycolaldehyde is easily oxidized to glyoxal. However, significantly lower levels of bivalent glyoxal modifications were detected in glycolaldehyde versus glyoxal incubations (glyoxal-lysine dimer, 1.58 ± 0.02 versus 2.86 ± 0.04 mmol/mol of phenylalanine; glyoxal-lysine amide, 2.7 ± 0.1 versus 5.6 ± 0.1 mmol/mol of phenylalanine). In addition, a novel glycolaldehyde-specific lysine-lysine cross-link was identified and putatively assigned as 1-(5-amino-5-carboxypentyl)-4-(5-amino-5-carboxypentyl-amino)pyridinium salt.

CT metal artifacts in patients with total hip replacements: for artifact reduction monoenergetic reconstructions and post-processing algorithms are both efficient but not similar.

OBJECTIVES: This study compares metal artifact (MA) reduction in imaging of total hip replacements (THR) using virtual monoenergetic images (VMI), for MA-reduction-specialized reconstructions (MAR) and conventional CT images (CI) from detector-based dual-energy computed tomography (SDCT). METHODS: Twenty-seven SDCT-datasets of patients carrying THR were included. CI, MAR and VMI with different energy-levels (60-200 keV) were reconstructed from the same scans. MA width was measured. Attenuation (HU), noise (SD) and contrast-to-noise ratio (CNR) were determined in: extinction artifact, adjacent bone, muscle and bladder. Two radiologists assessed MA-reduction and image quality visually. RESULTS: In comparison to CI, VMI (200 keV) and MAR showed a strong artifact reduction (MA width: CI 29.9±6.8 mm, VMI 17.6±13.6 mm, p<0.001; MAR 16.5±14.9 mm, p<0.001; MA density: CI -412.1±204.5 HU, VMI -279.7±283.7 HU; p<0.01; MAR -116.74±105.6 HU, p<0.001). In strong artifacts reduction was superior by MAR. In moderate artifacts VMI was more effective. MAR showed best noise reduction and CNR in bladder and muscle (p<0.05), whereas VMI were superior for depiction of bone (p<0.05). Visual assessment confirmed that VMI and MAR improve artifact reduction and image quality (p<0.001). CONCLUSIONS: MAR and VMI (200 keV) yielded significant MA reduction. Each showed distinct advantages both regarding effectiveness of artifact reduction, MAR regarding assessment of soft tissue and VMI regarding assessment of bone. KEY POINTS: • Spectral-detector computed tomography improves assessment of total hip replacements and surrounding tissue. • Virtual monoenergetic images and MAR reduce metal artifacts and enhance image quality. • Evaluation of bone, muscle and pelvic organs can be improved by SDCT.

Metal artifact reduction by dual-layer computed tomography using virtual monoenergetic images.

OBJECTIVE: The aim of the study was to investigate the performance and diagnostic value of metal artifact reduction in virtual monoenergetic images generated from dual-layer computed tomography (DLCT). METHODS: 35 patients that received a DLCT at the University Hospital Cologne and had an orthopedic implant in the examined region were included in this study. For each DLCT virtual monoenergetic images of different energy levels (64keV, 70keV, 105keV, 140keV, 200keV and an optimized photon energy) were reconstructed and analyzed by three blinded observers. Images were analyzed with regard to subjective criteria (extent of artifacts, diagnostic image quality) and objective criteria (width and density of artifacts). RESULTS: 21 patients had implants in the spine, 8 in the pelvis and 6 patients in the extremities. Diagnostic image quality improved significantly at high photon energies from a Likert-score of 4.3 (±0.83) to 2.3 (±1.02) and artifacts decreased significantly from a score of 4.3 (±0.66) to 2.6 (±2.57). The average optimized photon energy was 149.2±39.4keV. The density as well as the width of the most pronounced artifacts decreased from-374.6±251.89HU to -12.5±205.84HU and from 14.5±8.74mm to 6.4±10.76mm, respectively. CONCLUSION: Using virtual monoenergetic images valuable improvements of diagnostic image quality can be achieved by reduction of artifacts associated with metal implants. As preset for virtual monoenergetic images, 140keV appear to provide optimal artifact reduction. In 20% of the patients, individually optimized keV can lead to a further improvement of image quality compared to 140keV.