Sequential Acquisitions Research Articles

Protecting Patients And Society In An Era Of Private Equity Provider Ownership: Challenges And Opportunities For Policy.

Private equity (PE) acquisitions in health care delivery nearly tripled from 2010 to 2020. Despite concerns around clinical and economic implications, policy responses have remained limited. We discuss the US policy landscape around PE ownership, using policies in the European Union for comparison. We present four domains in which policy can be strengthened. First, to improve oversight of acquisitions, policy makers should lower reporting thresholds, review sequential acquisitions that together affect market power, automate reviews with potential denials based on market concentration effects, consider new regulatory mechanisms such as attorney general veto, and increase funding for this work. Second, policy makers should increase the longer-run transparency of PE ownership, including the health care prices garnered by acquired entities. Third, policy makers should protect patients and providers by establishing minimum staffing ratios, spending floors for direct patient care, and limits on layoffs and the sale of real estate after acquisition (forms of "asset stripping"). Finally, policy makers should mitigate risky financial behavior by limiting the amount or proportion of debt used to finance PE acquisitions in health care.

Tungsten-Based Contrast Agent for Photon-Counting Detector CT Angiography in Calcified Coronaries: Comparison to Iodine in a Cardiovascular Phantom.

Calcified plaques induce blooming artifacts in coronary computed tomography angiography (CCTA) potentially leading to inaccurate stenosis evaluation. Tungsten represents a high atomic number, experimental contrast agent with different physical properties than iodine. We explored the potential of a tungsten-based contrast agent for photon-counting detector (PCD) CCTA in heavily calcified coronary vessels. A cardiovascular phantom exhibiting coronaries with calcified plaques was imaged on a first-generation dual-source PCD-CT. The coronaries with 3 different calcified plaques were filled with iodine and tungsten contrast media solutions equating to iodine and tungsten delivery rates (IDR and TDR) of 0.3, 0.5, 0.7, 1.0, 1.5, 2.0, 2.5, and 3.0 g/s, respectively. Electrocardiogram-triggered sequential acquisitions were performed in the spectral mode (QuantumPlus). Virtual monoenergetic images (VMIs) were reconstructed from 40 to 190 keV in 1 keV increments. Blooming artifacts and percentage error stenoses from calcified plaques were quantified, and attenuation characteristics of both contrast media were recorded. Blooming artifacts from calcified plaques were most pronounced at 40 keV (78%) and least pronounced at 190 keV (58%). Similarly, percentage error stenoses were highest at 40 keV (48%) and lowest at 190 keV (2%), respectively. Attenuation of iodine decreased monotonically in VMIs from low to high keV, with the strongest decrease from 40 keV to 100 keV (IDR of 2.5 g/s: 1279 HU at 40 keV, 187 HU at 100 kV, and 35 HU at 190 keV). The attenuation of tungsten, on the other hand, increased monotonically as a function of VMI energy, with the strongest increase between 40 and 100 keV (TDR of 2.5 g/s: 202 HU at 40 keV, 661 HU at 100 kV, and 717 HU at 190 keV). For each keV level, the relationship between attenuation and IDR/TDR could be described by linear regressions ( R2 ≥ 0.88, P < 0.001). Specifically, attenuation increased linearly when increasing the delivery rate irrespective of keV level or contrast medium. Iodine exhibited the highest relative increase in attenuation values at lower keV levels when increasing the IDR. Conversely, for tungsten, the greatest relative increase in attenuation values occurred at higher keV levels when increasing the TDR. When high keV imaging is desirable to reduce blooming artifacts from calcified plaques, IDR has to be increased at higher keV levels to maintain diagnostic vessel attenuation (ie, 300 HU), whereas for tungsten, TDR can be kept constant or can be even reduced at high keV energy levels. Tungsten's attenuation characteristics in relation to VMI energy levels are reversed to those of iodine, with tungsten exhibiting high attenuation values at high keV levels and vice versa. Thus, tungsten shows promise for high keV imaging CCTA with PCD-CT as-in distinction to iodine-both high vessel attenuation and low blooming artifacts from calcified plaques can be achieved.

Measuring Value in Development with Advanced Real Options for International Sequential Acquisitions

Even though the application of real options theory in international business research has increased substantially, the measurement of collaborative synergies in international sequential acquisition by means of advanced real options is still the theoreticall gap which needs to be filled by new research and promising area for empirical research. This paper moves the field forward and highlights the fact that strategic synergies can be considered as compound real options for growth that are opened by an international sequential acquisition and, thus, add market value to the acquirer. Our research is presented as a theory-building inductive case-based study. This paper aims to integrate sequential compound real options with real options that have changing volatility in order to evaluate collaborative tacit synergies (a value in development) of sequential international acquisitions; thus, it contributes to corporate finance, international business, and strategic management theory with a fresh evaluation of the applications of advanced real options.

BEAT-TO-BEAT VARIABILITY OF INVASIVE PULSE WAVE VELOCITY: TECHNICAL AND CLINICAL ASPECTS

Objective: Invasive foot-to-foot pulse wave velocity (PWV) is the reference standard for validating new non-invasive PWV-measuring devices. Because of acute haemodynamic variability and data processing issues, PWV shows beat-to-beat variability, which may have important clinical and technical implications. Though current device validation guidelines suggest averaging over at least n = 3 heartbeats to cope with variability, quantitative data on PWV's beat-to-beat variability is lacking. We aimed to quantify this variability and its impact on the confidence of the PWV estimate. Design and method: Pressure waveforms were acquired in n = 82 individuals in the ascending aorta and iliac bifurcation using a dual-tip intra-aortic catheter. For each individual, two datasets were recorded: 1) simultaneous ascending and iliac pressure acquisitions (with ECG), and 2) an additional ascending aorta pressure acquisition (with ECG). Pressure wave foot detection was performed using the intersecting interpolant method. By combining the iliac pressure recording from the first acquisition with the ascending aorta pressure recording from the second acquisition, we evaluated how a sequential acquisition protocol (e.g., catheter pull-back) affects the variability. Furthermore, we estimated how averaging over n consecutive heartbeats affects the standard deviation (SD) of such n-beats-averaged estimate of PWV. Results: PWV was 10.93 ± 4.24 and 11.12 ± 4.42 m/s (mean ± between-subject SD) for simultaneous (PWVsim) and sequential acquisitions (PWVseq; p = 0.002), respectively. The average within-subject SD ( = variability) was 0.48 ± 0.28 m/s for PWVsim and 1.47 ± 1.20 m/s for PWVseq (p &lt; 0.001). This increase in variability was mainly due to the beat-to-beat variability of the ECG R-wave-to-pressure foot time interval, which was ∼2 times higher than that of the simultaneous foot-to-foot transit time (Figure A). Averaging over n = 3 reduced the variability of PWVsim to 0.37 ± 0.25 m/s, while n = 10.24 (median) is required to reach a comparable variability for PWVseq (Figure B). Conclusions: Variability of an invasive foot-to-foot PWV estimate increases considerably when using sequential rather than simultaneous acquisitions. This increase is caused by the high beat-to-beat variability of the duration of the pre-ejection period. To reduce the effective variability of a sequential acquisition to the same level as that of a simultaneous acquisition, averaging over an approximately threefold higher number of heartbeats is required.

Design of a generic method for single dual-tracer PET imaging acquisition in clinical routine

Using different tracers in positron emission tomography (PET) imaging can bring complementary information on tumor heterogeneities. Ideally, PET images of different tracers should be acquired simultaneously to avoid the bias induced by movement and physiological changes between sequential acquisitions. Previous studies have demonstrated the feasibility of recovering separated PET signals or parameters of two or more tracers injected (quasi-)simultaneously in a single acquisition. In this study, a generic framework in the context of dual-tracer PET acquisition is proposed where no strong kinetic assumptions nor specific tuning of parameters are required. The performances of the framework were assessed through simulations involving the combination of [18F]FCH and [18F]FDG injections, two protocols (90 and 60 min acquisition durations) and various activity ratios between the two injections. Preclinical experiments with the same radiotracers were also conducted. Results demonstrate the ability of the method both to extract separated arterial input functions (AIF) from noisy image-derived input function and to separate the dynamic signals and further estimate kinetic parameters. The compromise between bias and variance associated with the estimation of net influx rate K i shows that it is preferable to use the second injected radiotracer with twice the activity of the first for both 90 min [18F]FCH+[18F]FDG and 60 min [18F]FDG+[18F]FCH protocols. In these optimal settings, the weighted mean-squared-error of the estimated AIF was always less than 7%. The K i bias was similar to the one of single-tracer acquisitions; below 5%. Compared to single-tracer results, the variance of K i was twice more for 90 min dual-tracer scenario and four times more for the 60 min scenario. The generic design of the method makes it easy to use for other pairs of radiotracers and even for more than two tracers. The absence of strong kinetic assumptions and tuning parameters makes it suitable for a possible use in clinical routine.

Introduction to the Virtual Special Issue: Strategy Science’s Contributions to Doctoral Reading Lists

Introduction to the Virtual Special Issue: <i>Strategy Science</i>’s Contributions to Doctoral Reading Lists

High-throughput multi-color reliable SMLM nanoscopy.

Beyond all super-resolution microscopy methods, single molecule localization microscopy (SMLM) offers best 3D spatial resolution, up to several nanometers. Despite its super-resolutive property, SMLM has still a low throughput. In this context, SMLM offers a mono-color limited field of view (FOV). SMLM suffers indeed from fluorophore photoswitching characteristics, which depends on the wavelength, and significant chromatic aberration at the nanoscale. Multicolor SMLM imaging is classically achieved by sequential acquisitions at different excitation wavelengths, but lengthy acquisition times, drifts between the different color recordings, and cross excitation by different lasers may hamper quantitative reconstruction. In this talk, we will present two strategies to increase the FOV up to 200 × 200 µm² while improving the number of colors up to 3: Adaptable Scanning for Tunable Excitation Regions (ASTER) and spectral-demixing respectively. The association of ASTER and spectral demixing leads to increase the throughput by a factor 50 compared to standard nanoscopy approach, in the same acquisition time. We here present a reliable characterization of those methods for homogeneity, localisation precision, crosstalk, labelling density influence. By using complementary samples, we could obtain a rigorous estimation of the performances in various settings: DNA origamis, gold standard samples for SMLM, up to real biological applications as hippocampal neurons or extracellular vesicles characterization.

Assignment of aromatic side-chain spins and characterization of their distance restraints at fast MAS

The assignment of aromatic side-chain spins has always been more challenging than assigning backbone and aliphatic spins. Selective labeling combined with mutagenesis has been the approach for assigning aromatic spins. This manuscript reports a method for assigning aromatic spins in a fully protonated protein by connecting them to the backbone atoms using a low-power TOBSY sequence. The pulse sequence employs residual polarization and sequential acquisitions techniques to record HN- and HC-detected spectra in a single experiment. The unambiguous assignment of aromatic spins also enables the characterization of 1H–1H distance restraints involving aromatic spins. Broadband (RFDR) and selective (BASS-SD) recoupling sequences were used to generate HN-ΗC, HC-HN and HC-HC restraints involving the side-chain proton spins of aromatic residues. This approach has been demonstrated on a fully protonated U-[13C,15N] labeled GB1 sample at 95–100 kHz MAS.

Measuring Collaborative Synergies with Advanced Real Options: MNEs’ Sequential Acquisitions of International Ventures

This paper aims to extend the real options theory valuing strategic collaborative synergies by advanced real options with changing volatility and contributes to the international business literature on MNEs’ sequential acquisitions of international ventures. The proposition is that collaborative synergies can be valued with advanced real options with changing volatility when an MNE is pursuing the sequential acquisition of an international venture and the MNE’s stock volatility is changing at the time of deciding on a full takeover. The paper discusses how recombining and non-recombining lattices with constant and changing volatilities can be employed to value the collaborative synergies of sequential international acquisitions. The theoretical proposition has been justified with the explanatory case study: Natura Cosméticos S.A.’s (Brazil) sequential acquisition of the Aesop brand (Australia). In conclusion, the paper discusses its findings, contributions, limitations, and future work.

A quantitative analysis of various patterns applied in lattice light sheet microscopy

Light sheet microscopes reduce phototoxicity and background and improve imaging speed compared to widefield and confocal microscopes. However, when equipped with Gaussian beams, the axial resolving power of a light sheet microscope and the observable field of view are inversely related. Light sheets based on dithered optical lattices improve axial resolution and beam uniformity compared Gaussian beams by using axially structured illumination patterns. However, these advantages come at the expense of an increased total illumination to the specimen and a decreased axial confinement of the illumination pattern. Using simulations and experimental measurements in fixed and live cells, we quantify the differences between Gaussian and lattice light sheets on beam uniformity, axial resolution, lateral resolution, and photobleaching. We demonstrate how different optical lattice illumination patterns can be tuned to prioritize either axial resolution or optical sectioning. Finally, we introduce an approach to spectrally fuse sequential acquisitions of different lattice light sheet patterns with complementary optical properties to achieve both high resolution and low background images.

Interleaved and simultaneous multi-nuclear magnetic resonance in vivo. Review of principles, applications and potential.

Magnetic resonance signals from different nuclei can be excited or received at the same time,rendering simultaneous or rapidly interleaved multi‐nuclear acquisitions feasible. The advan‐tages are a reduction of total scan time compared to sequential multi‐nuclear acquisitions or that additional information from heteronuclear data is obtained at thesame time and anatomical position. Information content can be qualitatively increased by delivering a more comprehensive MR‐based picture of a transient state (such as an exercise bout). Also, combiningnon‐proton MR acquisitions with 1Hinformation (e.g., dynamic shim updates and motion correction) can be used to improve data quality during long scans and benefits image coregistration. This work reviews the literature on interleaved and simultaneous multi‐nuclear MRI and MRS in vivo. Prominent use cases for this methodology in clinical and research applications are brain and muscle, but studies have also been carried out in other targets, including the lung, knee, breast and heart. Simultaneous multi‐nuclear measurements in the liver and kidney have also been performed, but exclusively in rodents. In this review, a consistent nomenclature is proposed, to help clarify the terminology used for this principle throughout the literature on in‐vivo MR. An overview covers the basic principles, the technical requirements on the MR scanner and the implementations realised either by MR system vendors or research groups, from the early days until today. Considerations regarding the multi‐tuned RF coils required and heteronuclear polarisation interactions are briefly discussed, and fields for future in‐vivo applications for interleaved multi‐nuclear MR pulse sequences are identified.

Single-cell DNA-seq depicts clonal evolution of multiple driver alterations in osimertinib-resistant patients

The development of targeted agents, such as osimertinib for EGFR-mutated non-small-cell lung cancer (NSCLC), has drastically improved patient outcome, but tumor resistance eventually always occurs. In osimertinib-resistant NSCLC, the emergence of a second molecular driver alteration (such as ALK, RET, FGFR3 fusions or BRAF, KRAS mutations) has been described. Whether those alterations and the activating EGFR mutations occur within a single cancer cell or in distinct cell populations is largely debated. Tumor sequencing was used to identify the acquired resistance mechanisms to osimertinib in the MATCH-R trial (NCT0251782). We implemented single-cell next-generation sequencing to investigate tumor heterogeneity on patient's frozen tissues in which multiple alterations have been identified. Patient-derived models, cell lines, and patient-derived xenografts were exposed to specific inhibitors to investigate combination treatment strategies. Among the 45 patients included in MATCH-R who progressed on osimertinib, 9 developed a second targetable alteration (n= 2 FGFR3-TACC3, n= 1 KIF5B-RET, n= 1 STRN-ALK fusions; n= 2 BRAFV600E, n= 1 KRASG12V, n= 1 KRASG12R, n= 1 KRASG12D mutations). Single-cell analysis revealed that the two driver alterations coexist within one single cancer cell in the four patients whose frozen samples were fully contributive. A high degree of heterogeneity within samples and sequential acquisitions of molecular events were highlighted. A combination treatment concomitantly targeting the two driver alterations was required on the corresponding patient-derived models to restore cell sensitivity, which was consistent with clinical data showing efficacy of brigatinib in the patient with ALK fusion after progression to osimertinib and crizotinib administered sequentially. Distinct molecular driver alterations at osimertinib resistance coexist with initial EGFR mutations in single cancer cells. The clonal evolution of cancer cell populations emphasized their heterogeneity leading to osimertinib relapse. Combining two targeted treatments is effective to achieve clinical benefit.

Landslide Susceptibility Mapping of Central and Western Greece, Combining NGI and WoE Methods, with Remote Sensing and Ground Truth Data

The exploitation of remote sensing techniques has substantially improved pre- and post- disaster landslide management over the last decade. A variety of landslide susceptibility methods exists, with capabilities and limitations related to scale and spatial accuracy issues, as well as data availability. The Interferometric Synthetic Aperture Radar (InSAR) capabilities have significantly contributed to the detection, monitoring, and mapping of landslide phenomena. The present study aims to point out the contribution of InSAR data in landslide detection and to evaluate two different scale landslide models by comparing a heuristic to a statistical method for the rainfall-induced landslide hazard assessment. Aiming to include areas with both high and low landslide occurrence frequencies, the study area covers a large part of the Aetolia–Acarnania and Evritania prefectures, Central and Western Greece. The landslide susceptibility product provided from the weights of evidence (WoE) method proved more accurate, benefitting from the expert opinion and the landslide inventory. On the other hand, the Norwegian Geological Institute (NGI) methodology has the edge on its immediate implementation, with minimum data requirements. Finally, it was proved that using sequential SAR image acquisitions gives the benefit of an updated landslide inventory, resulting in the generation of, on request, updated landslide susceptibility maps.

A multi-inversion multi-echo spin and gradient echo echo planar imaging sequence with low image distortion for rapid quantitative parameter mapping and synthetic image contrasts.

Brain imaging exams typically take 10-20 min and involve multiple sequential acquisitions. A low-distortion whole-brain echo planar imaging (EPI)-based approach was developed to efficiently encode multiple contrasts in one acquisition, allowing for calculation of quantitative parameter maps and synthetic contrast-weighted images. Inversion prepared spin- and gradient-echo EPI was developed with slice-order shuffling across measurements for efficient acquisition with T1 , T2 , and weighting. A dictionary-matching approach was used to fit the images to quantitative parameter maps, which in turn were used to create synthetic weighted images with typical clinical contrasts. Dynamic slice-optimized multi-coil shimming with a B0 shim array was used to reduce B0 inhomogeneity and, therefore, image distortion by >50%. Multi-shot EPI was also implemented to minimize distortion and blurring while enabling high in-plane resolution. A low-rank reconstruction approach was used to mitigate errors from shot-to-shot phase variation. The slice-optimized shimming approach was combined with in-plane parallel-imaging acceleration of 4× to enable single-shot EPI with more than eight-fold distortion reduction. The proposed sequence efficiently obtained 40 contrasts across the whole-brain in just over 1 min at 1.2 × 1.2 × 3 mm resolution. The multi-shot variant of the sequence achieved higher in-plane resolution of 1 × 1 × 4 mm with good image quality in 4 min. Derived quantitative maps showed comparable values to conventional mapping methods. The approach allows fast whole-brain imaging with quantitative parameter maps and synthetic weighted contrasts. The slice-optimized multi-coil shimming and multi-shot reconstruction approaches result in minimal EPI distortion, giving the sequence the potential to be used in rapid screening applications.

A comprehensive assessment of physical image quality of five different scanners for head CT imaging as clinically used at a single hospital centre-A phantom study.

Nowadays, given the technological advance in CT imaging and increasing heterogeneity in characteristics of CT scanners, a number of CT scanners with different manufacturers/technologies are often installed in a hospital centre and used by various departments. In this phantom study, a comprehensive assessment of image quality of 5 scanners (from 3 manufacturers and with different models) for head CT imaging, as clinically used at a single hospital centre, was hence carried out. Helical and/or sequential acquisitions of the Catphan-504 phantom were performed, using the scanning protocols (CTDIvol range: 54.7–57.5 mGy) employed by the staff of various Radiology/Neuroradiology departments of our institution for routine head examinations. CT image quality for each scanner/acquisition protocol was assessed through noise level, noise power spectrum (NPS), contrast-to-noise ratio (CNR), modulation transfer function (MTF), low contrast detectability (LCD) and non-uniformity index analyses. Noise values ranged from 3.5 HU to 5.7 HU across scanners/acquisition protocols. NPS curves differed in terms of peak position (range: 0.21–0.30 mm-1). A substantial variation of CNR values with scanner/acquisition protocol was observed for different contrast inserts. The coefficient of variation (standard deviation divided by mean value) of CNR values across scanners/acquisition protocols was 18.3%, 31.4%, 34.2%, 30.4% and 30% for teflon, delrin, LDPE, polystyrene and acrylic insert, respectively. An appreciable difference in MTF curves across scanners/acquisition protocols was revealed, with a coefficient of variation of f50%/f10% of MTF curves across scanners/acquisition protocols of 10.1%/7.4%. A relevant difference in LCD performance of different scanners/acquisition protocols was found. The range of contrast threshold for a typical object size of 3 mm was 3.7–5.8 HU. Moreover, appreciable differences in terms of NUI values (range: 4.1%-8.3%) were found. The analysis of several quality indices showed a non-negligible variability in head CT imaging capabilities across different scanners/acquisition protocols. This highlights the importance of a physical in-depth characterization of image quality for each CT scanner as clinically used, in order to optimize CT imaging procedures.

Rapidly emerging SARS-CoV-2 B.1.1.7 sub-lineage in the United States of America with spike protein D178H and membrane protein V70L mutations

ABSTRACT The SARS-CoV-2 B.1.1.7 lineage is highly infectious and as of April 2021 accounted for 92% of COVID-19 cases in Europe and 59% of COVID-19 cases in the U.S. It is defined by the N501Y mutation in the receptor-binding domain (RBD) of the Spike (S) protein, and a few other mutations. These include two mutations in the N terminal domain (NTD) of the S protein, HV69-70del and Y144del (also known as Y145del due to the presence of tyrosine at both positions). We recently identified several emerging SARS-CoV-2 variants of concerns, characterized by Membrane (M) protein mutations, including I82T and V70L. We now identify a sub-lineage of B.1.1.7 that emerged through sequential acquisitions of M:V70L in November 2020 followed by a novel S:D178H mutation first observed in early February 2021. The percentage of B.1.1.7 isolates in the US that belong to this sub-lineage increased from 0.15% in February 2021 to 1.8% in April 2021. To date, this sub-lineage appears to be U.S.-specific with reported cases in 31 states, including Hawaii. As of April 2021, it constituted 36.8% of all B.1.1.7 isolates in Washington. Phylogenetic analysis and transmission inference with Nextstrain suggest this sub-lineage likely originated in either California or Washington. Structural analysis revealed that the S:D178H mutation is in the NTD of the S protein and close to two other signature mutations of B.1.1.7, HV69-70del and Y144del. It is surface exposed and may alter NTD tertiary configuration or accessibility, and thus has the potential to affect neutralization by NTD directed antibodies.

Advantage and validation of vendor-independent software for myocardial strain analysis compared to vendor-specific software.

One of the main limitations incorporating strain imaging into widespread clinical practice is inter-vendor incompatibility. This poses a problem when serial strain measurements are required in a multi-vendor echocardiography laboratory. This study sought to compare the variability of two-dimensional speckle-tracking global and regional longitudinal strain using vendor-specific software and vendor-independent software from images acquired by two different commercially available ultrasound systems. Forty subjects underwent two sequential echocardiographic acquisitions using different ultrasound systems (GE Vivid E9 and Philips iE33). Global longitudinal strain and regional peak longitudinal strain were derived using vendor-specific software (EchoPAC BT 13 v201 and QLAB version 10.3) and vendor-independent software (TomTec Image Arena version 4.6). Agreement and reproducibility of global and regional strain between vendor-specific and vendor-independent software were assessed by independent blinded observers. Global longitudinal strain derived from vendor-independent software was comparable to global longitudinal strain derived from vendor-specific software, whilst regional strain was lower in agreement compared to global longitudinal strain. There was good overall agreement and high inter- and intra-observer reproducibility using vendor-independent software for global longitudinal strain and regional strain. Vendor-independent software provides good agreement with vendor-specific software for global longitudinal strain. However, minor variability exists for regional strain measurements between vendor-independent and vendor-specific software. Good agreement of strain measurements derived by vendor-independent software suggests vendor-independent software could potentially be useful for serial follow-up of global longitudinal strain.

Agreement between left ventricular ejection fraction assessed in patients with gated IQ-SPECT and conventional imaging

BackgroundThe aim of the study was to assess the agreement between the left ventricular ejection fraction (LVEF) values obtained with IQ-SPECT and those obtained with a conventional gamma camera equipped with low-energy high-resolution (LEHR), considered as the method of reference. MethodsGated-stress MPI using 99mTc-tetrofosmin was performed in 55 consecutive patients. The patients underwent two sequential acquisitions (Method A and B) performed on Symbia-IQ SPECT with different acquisition times and one (Method C) on a Ecam SPECT equipped with LEHR collimators. The values of the different datasets were compared using the Bland-Altman analysis method: the bias and the limits of agreement (LA) were estimated in a head-to-head comparison of the three protocols. ResultsIn the (Method A-Method C) comparison for LVEF, the bias was 3.8% and the LAs ranged from − 9.3% to 16.8%. The agreement was still lower between Method B and C, whilst only slightly improved when Methods A and B were compared. ConclusionsThe wide amplitude in LA intervals of about 30% indicates that IQ and LEHR GSPECT are not interchangeable. The values obtained with IQ-SPECT should only be used with caution when evaluating the functional state of the heart.

Virtual brightfield and fluorescence staining for Fourier ptychography via unsupervised deep learning.

Fourier ptychographic microscopy (FPM) is a computational approach geared towards creating high-resolution and large field-of-view images without mechanical scanning. Acquiring color images of histology slides often requires sequential acquisitions with red, green, and blue illuminations. The color reconstructions often suffer from coherent artifacts that are not presented in regular incoherent microscopy images. As a result, it remains a challenge to employ FPM for digital pathology applications, where resolution and color accuracy are of critical importance. Here we report a deep learning approach for performing unsupervised image-to-image translation of FPM reconstructions. A cycle-consistent adversarial network with multiscale structure similarity loss is trained to perform virtual brightfield and fluorescence staining of the recovered FPM images. In the training stage, we feed the network with two sets of unpaired images: (1) monochromatic FPM recovery and (2) color or fluorescence images captured using a regular microscope. In the inference stage, the network takes the FPM input and outputs a virtually stained image with reduced coherent artifacts and improved image quality. We test the approach on various samples with different staining protocols. High-quality color and fluorescence reconstructions validate its effectiveness.

Temperature Compensation of Crystal References in NB-IoT Modems

The low-cost nature of NB-IoT modems encourages them to deploy uncompensated crystal oscillators (XOs) as frequency references. The frequency offset of an uncompensated XO, however, makes network acquisition inefficient under low network coverage. In the worst case, the bulk of an NB-IoT modem’s power is consumed in network acquisition. This work demonstrates a discrete frequency synthesizer prototype that employs its phase-locked loop to compensate for the frequency offset of its reference XO. We propose an accurate crystal model and a compensation logic that are suitable for 32-bit microprocessors, commonly available in NB-IoT modems. Alternatively, when synthesized in a commercial 65-nm process in 24-bit precision, the proposed compensation logic is simulated to require a total area of 0.029 mm2 and power of 290 nW at a refresh rate of 1.4 kHz. Moreover, the XO model requires only 0.16 kB of RAM. The prototype achieves a compensation error level of down to 27 ppb ( $3\sigma $ ) over the temperature range from −40 to 85 °C. The dominant error sources of the prototype are discussed in detail. In addition, we show that an NB-IoT modem can use the information acquired from sequential network acquisitions to compose and update its XO model in the field. This support for field calibration removes the need for XO characterization in production and ensures the validity of the model over the NB-IoT modem’s lifespan. The prototype achieves a compensation error level of down to 50 ppb ( $3\sigma $ ) in an emulated in-field calibration test, sufficient to ensure energy-efficient low-latency network acquisition under low network coverage.