Cooperative AI training for cardiothoracic segmentation in computed tomography: An iterative multi-center annotation approach.

PURPOSE: Radiological reporting is transitioning to quantitative analysis, requiring large-scale multi-center validation of biomarkers. A major prerequisite and bottleneck for this task is the voxelwise annotation of image data, which is time-consuming for large cohorts. In this study, we propose an iterative training workflow to support and facilitate such segmentation tasks, specifically for high-resolution thoracic CT data. METHODS: Our study included 132 thoracic CT scans from clinical practice, annotated by 13 radiologists. In three iterative training experiments, we aimed to improve and accelerate segmentation of the heart and mediastinum. Each experiment started with manual segmentation of 5-25 CT scans, which served as training data for a nnU-Net. Further iterations incorporated AI pre-segmentation and human correction to improve accuracy, accelerate the annotation process, and reduce human involvement over time. RESULTS: Results showed consistent improvement in AI model quality with each iteration. Resampled datasets improved the Dice similarity coefficients for both the heart (DCS 0.91 [0.88; 0.92]) and the mediastinum (DCS 0.95 [0.94; 0.95]). Our AI models reduced human interaction time by 50 % for heart and 70 % for mediastinum segmentation in the most potent iteration. A model trained on only five datasets achieved satisfactory results (DCS > 0.90). CONCLUSIONS: The iterative training workflow provides an efficient method for training AI-based segmentation models in multi-center studies, improving accuracy over time and simultaneously reducing human intervention. Future work will explore the use of fewer initial datasets and additional pre-processing methods to enhance model quality.

Automated image quality assessment for selecting among multiple magnetic resonance image acquisitions in the German National Cohort study.

In magnetic resonance imaging (MRI), the perception of substandard image quality may prompt repetition of the respective image acquisition protocol. Subsequently selecting the preferred high-quality image data from a series of acquisitions can be challenging. An automated workflow may facilitate and improve this selection. We therefore aimed to investigate the applicability of an automated image quality assessment for the prediction of the subjectively preferred image acquisition. Our analysis included data from 11,347 participants with whole-body MRI examinations performed as part of the ongoing prospective multi-center German National Cohort (NAKO) study. Trained radiologic technologists repeated any of the twelve examination protocols due to induced setup errors and/or subjectively unsatisfactory image quality and chose a preferred acquisition from the resultant series. Up to 11 quantitative image quality parameters were automatically derived from all acquisitions. Regularized regression and standard estimates of diagnostic accuracy were calculated. Controlling for setup variations in 2342 series of two or more acquisitions, technologists preferred the repetition over the initial acquisition in 1116 of 1396 series in which the initial setup was retained (79.9%, range across protocols: 73-100%). Image quality parameters then commonly showed statistically significant differences between chosen and discarded acquisitions. In regularized regression across all protocols, 'structured noise maximum' was the strongest predictor for the technologists' choice, followed by 'N/2 ghosting average'. Combinations of the automatically derived parameters provided an area under the ROC curve between 0.51 and 0.74 for the prediction of the technologists' choice. It is concluded that automated image quality assessment can, despite considerable performance differences between protocols and anatomical regions, contribute substantially to identifying the subjective preference in a series of MRI acquisitions and thus provide effective decision support to readers.

Whole-Body Magnetic Resonance Imaging in the Large Population-Based German National Cohort Study: Predictive Capability of Automated Image Quality Assessment for Protocol Repetitions.

BACKGROUND: Reproducible image quality is of high relevance for large cohort studies and can be challenging for magnetic resonance imaging (MRI). Automated image quality assessment may contribute to conducting radiologic studies effectively. PURPOSE: The aims of this study were to assess protocol repetition frequency in population-based whole-body MRI along with its effect on examination time and to examine the applicability of automated image quality assessment for predicting decision-making regarding repeated acquisitions. MATERIALS AND METHODS: All participants enrolled in the prospective, multicenter German National Cohort (NAKO) study who underwent whole-body MRI at 1 of 5 sites from 2014 to 2016 were included in this analysis (n = 11,347). A standardized examination program of 12 protocols was used. Acquisitions were carried out by certified radiologic technologists, who were authorized to repeat protocols based on their visual perception of image quality. Eleven image quality parameters were derived fully automatically from the acquired images, and their discrimination ability regarding baseline acquisitions and repetitions was tested. RESULTS: At least 1 protocol was repeated in 12% (n = 1359) of participants, and more than 1 protocol in 1.6% (n = 181). The repetition frequency differed across protocols (P < 0.001), imaging sites (P < 0.001), and over the study period (P < 0.001). The mean total scan time was 62.6 minutes in participants without and 67.4 minutes in participants with protocol repetitions (mean difference, 4.8 minutes; 95% confidence interval, 4.5-5.2 minutes). Ten of the automatically derived image quality parameters were individually retrospectively predictive for the repetition of particular protocols; for instance, "signal-to-noise ratio" alone provided an area under the curve of 0.65 (P < 0.001) for repetition of the Cardio Cine SSFP SAX protocol. Combinations generally improved prediction ability, as exemplified by "image sharpness" plus "foreground ratio" yielding an area under the curve of 0.89 (P < 0.001) for repetition of the Neuro T1w 3D MPRAGE protocol, versus 0.85 (P < 0.001) and 0.68 (P < 0.001) as individual parameters. CONCLUSIONS: Magnetic resonance imaging protocol repetitions were necessary in approximately 12% of scans even in the highly standardized setting of a large cohort study. Automated image quality assessment shows predictive value for the technologists' decision to perform protocol repetitions and has the potential to improve imaging efficiency.

Stacked Ensemble Machine Learning for Range-Separation Parameters.

Density functional theory-based high-throughput materials and drug discovery has achieved tremendous success in recent decades, but its power on organic semiconducting molecules suffered catastrophically from the self-interaction error until the nonempirical but expensive optimally tuned range-separated hybrid (OT-RSH) functionals were developed. An OT-RSH transitions from a short-range (semi)local functional to a long-range Hartree-Fock exchange at a distance characterized by a molecule-specific range-separation parameter (ω). Herein, we propose a stacked ensemble machine learning model that provides an accelerated alternative of OT-RSH based on system-dependent structural and electronic configurations. We trained ML-ωPBE, the first functional in our series, using a database of 1970 molecules with sufficient structural and functional diversity, and assessed its accuracy and efficiency using another 1956 molecules. Compared with nonempirical OT-ωPBE, ML-ωPBE reaches a mean absolute error of 0.00504a0-1 for optimal ω's, reduces the computational cost by 2.66 orders of magnitude, and achieves comparable predictive power in optical properties.

Cobalt Kß valence-to-core X-ray emission spectroscopy: a study of low-spin octahedral cobalt(iii) complexes.

Kß valence-to-core (V2C) X-emission spectroscopy (XES) has gained prominence as a tool for molecular inorganic chemists to probe the occupied valence orbitals of coordination complexes, as illustrated by recent evaluation of Kß V2C XES ranging from titanium to iron. However, cobalt Kß V2C XES has not been studied in detail, limiting the application of this technique to probe cobalt coordination in molecular catalysts and bioinorganic systems. In addition, the community still lacks a complete understanding of all factors that dictate the V2C peak area. In this manuscript, we report experimental cobalt Kß V2C XES spectra of low-spin octahedral Co(iii) complexes with different ligand donors, in conjunction with DFT calculations. Cobalt Kß V2C XES was demonstrated to be sensitive to cobalt-ligand coordination environments. Notably, we recognize here for the first time that there is a linear correlation between the V2C area and the spectrochemical series for low-spin octahedral cobalt(iii) complexes, with strong field π acceptor ligands giving rise to the largest V2C area. This unprecedented correlation is explained by invoking different levels of π-interaction between cobalt p orbitals and ligand orbitals that modulate the percentage of cobalt p orbital character in donor MOs, in combination with changes in the average cobalt-ligand distance.

Whole-Body MR Imaging in the German National Cohort: Rationale, Design, and Technical Background.

PURPOSE: To detail the rationale, design, and future perspective of implementing whole-body magnetic resonance (MR) imaging in the German National Cohort, a large multicentric population-based study. MATERIALS AND METHODS: All institutional review boards approved the study, and informed consent is obtained before study enrollment. Participants are enrolled from a random sample of the general population at five dedicated imaging sites among 18 recruitment centers. MR imaging facilities are equipped with identical 3.0-T imager technology and use uniform MR protocols. Imager-specific hardware and software settings remained constant over the study period. On-site and centralized measures of image quality enable monitoring of completeness of the acquisitions and quality of each of the MR sequences. Certified radiologists read all MR imaging studies for presence of incidental findings according to predefined algorithms. RESULTS: Over a 4-year period, six participants per day are examined at each center, totaling a final imaging cohort of approximately 30 000 participants. The MR imaging protocol is identical for each site and comprises a set of 12 native series to cover neurologic, cardiovascular, thoracoabdominal, and musculoskeletal imaging phenotypes totaling approximately 1 hour of imaging time. A dedicated analysis platform as part of a central imaging core incorporates a thin client-based integrative and modular data handling platform to enable multicentric off-site image reading for incidental findings. Scientific analysis will be pursued on a per-project hypothesis-driven basis. CONCLUSION: Population-based whole-body MR imaging as part of the German National Cohort will serve to compile a comprehensive image repository, will provide insight into physiologic variants and subclinical disease burden, and has the potential to enable identification of novel imaging biomarkers of risk.

Imaging and surgical planning for perihilar cholangiocarcinoma.

Recent advances in multidetector computed tomography (MDCT) offer several benefits for management of perihilar tumors. Resection planning for perihilar cholangiocarcinoma should consider two factors: safety and curability. Recognition of individual anatomic variations is particularly important for avoiding intraoperative injury. In particular, hepatic arterial variations often restrict resection procedures. Extent of both longitudinal and vertical invasion by biliary tumors can be estimated from multiplanar reconstruction (MPR) images. Longitudinal extent of resection can be planned based on two anatomic landmarks, the U point and the P point, readily identifiable in preoperative 3-dimensional (3D) images and by intraoperative inspection. Concerning vertical invasion, when direct vascular invasion is suspected from a finding of attachment of tumor and vessels such as portal veins and/or hepatic arteries without a thin low-density plane of separation shown by MPR, these vessels should be resected en bloc with the tumor. Surgical team members can plan and simulate details of vascular resection and reconstruction using 3D images. Reduced operative morbidity and increased R0 resection rates are expected because of better planning of procedures. These techniques soon may increase long-term survival for patients with perihilar cholangiocarcinoma.

Subtypes of excitatory amino acid receptors involved in the stimulation of [3H]dopamine release from cell cultures of rat ventral mesencephalon.

N-methyl-D-aspartic acid (NMDA), quisqualic acid (QUIS), and kainic acid (KAIN), respective agonists for three excitatory amino acid (EAA) receptor subtypes, stimulated [3H]dopamine ([3H]DA) release from dissociated cell cultures of fetal rat ventral mesencephalon. Release evoked by all three agonists was Ca2(+)-dependent and inhibited by broad-spectrum antagonists (D,L-cis-2,3-piperidine dicarboxylic acid [PDA] and kynurenic acid [KYN]). However, both of these antagonists were more potent against KAIN than against QUIS and only KAIN-evoked release was blocked by gamma-D-glutamyl-aminomethyl sulfonic acid (GAMS, IC50 700 microM). NMDA-stimulated [3H]DA release was selectively inhibited by competitive (3-[2-carboxypiperazine-4-yl]propyl-1-phosphonic acid [CPP] and D,L-2-amino-5-phosphonovaleric acid [APV]) and non-competitive (phencyclidine and MK-801) NMDA receptor antagonists. In 1.2 mM Mg2+, NMDA-stimulated [3H]DA release was Na(+)-dependent and inhibited by tetrodotoxin (TTX, 2 microM) or by the local anaesthetic, lidocaine (200 microM). However, in 0 Mg 2+, NMDA-evoked release was not inhibited by TTX or lidocaine. Thus, TTX-sensitivity of the NMDA response in 1.2 mM Mg2+ apparently occurs because Na(+)-action potentials are required to alleviate a Mg2+ blockade. Neither QUIS- nor KAIN-evoked release was affected by Mg2+ or TTX. When extracellular NaCl was replaced by sucrose or Na2SO4, the QUIS response was increased. KAIN-evoked release was unaffected by the sucrose substitution and was attenuated in the Na2SO4-containing buffer. It is concluded that NMDA and QUIS/KAIN release [3H]DA via separate receptor subtypes.