Quantum iterative reconstruction on a photon-counting detector CT improves the quality of hepatocellular carcinoma imaging

Background Excellent image quality is crucial for workup of hepatocellular carcinoma (HCC) in patients with liver cirrhosis because a signature tumor signal allows for non-invasive diagnosis without histologic proof. Photon-counting detector computed tomography (PCD-CT) can enhance abdominal image quality, especially in combination with a novel iterative reconstruction algorithm, quantum iterative reconstruction (QIR). The purpose of this study was to analyze the impact of different QIR levels on PCD-CT imaging of HCC in both phantom and patient scans. Methods Virtual monoenergetic images at 50 keV were reconstructed using filtered back projection and all available QIR levels (QIR 1–4). Objective image quality properties were investigated in phantom experiments. The study also included 44 patients with triple-phase liver PCD-CT scans of viable HCC lesions. Quantitative image analysis involved assessing the noise, contrast, and contrast-to-noise ratio of the lesions. Qualitative image analysis was performed by three raters evaluating noise, artifacts, lesion conspicuity, and overall image quality using a 5-point Likert scale. Results Noise power spectra in the phantom experiments showed increasing noise suppression with higher QIR levels without affecting the modulation transfer function. This pattern was confirmed in the in vivo scans, in which the lowest noise levels were found in QIR-4 reconstructions, with around a 50% reduction in median noise level compared with the filtered back projection images. As contrast does not change with QIR, QIR-4 also yielded the highest contrast-to-noise ratios. With increasing QIR levels, rater scores were significantly better for all qualitative image criteria (all p < .05). Conclusions Without compromising image sharpness, the best image quality of iodine contrast optimized low-keV virtual monoenergetic images can be achieved using the highest QIR level to suppress noise. Using these settings as standard reconstruction for HCC in PCD-CT imaging might improve diagnostic accuracy and confidence

Portal hypertension in patients with hepatocellular carcinoma and immunotherapy : prognostic relevance of CT-morphologic estimates

Background Clinically significant portal hypertension (CSPH) has been identified as an important prognostic factor in patients with hepatocellular carcinoma (HCC) undergoing curative treatment. This study aimed to assess PH estimates as prognostic factors in patients with HCC treated with immunotherapy. Methods All patients with HCC treated with an immunotherapeutic agent in first or subsequent lines at our tertiary care center between 2016 and 2021 were included (n = 50). CSPH was diagnosed using the established PH score for non-invasive PH estimation in pre-treatment CT data (cut-off ≥ 4). Influence of PH on overall survival (OS) and progression-free survival (PFS) was assessed in uni- and multivariable analyses. Results Based on the PH score, 26 patients (52.0%) were considered to have CSPH. After treatment initiation, patients with CSPH had a significantly impaired median OS (4.1 vs 33.3 months, p < 0.001) and a significantly impaired median PFS (2.7 vs 5.3 months, p = 0.02). In multivariable Cox regression, CSPH remained significantly associated with survival (HR 2.9, p = 0.015) when adjusted for established risk factors. Conclusions Non-invasive assessment of CSPH using routine CT data yielded an independent prognostic factor in patients with HCC and immunotherapy. Therefore, it might function as an additional imaging biomarker to detect high-risk patients with poor survival and possibly for treatment decision making

A multidisciplinary pulmonary embolism response team (PERT) : first experience from a single center in Germany

Background Over the last few years, the concept of multidisciplinary pulmonary embolism response teams (PERTs) has emerged to encounter the increasing variety and complexity in managing acute pulmonary embolism (PE). Purpose To investigate PERT's composition and added clinical value in a university center in Germany. Methods Over 4 years (01/2019–11/2022), patients with confirmed PE were enrolled in a prospective single-center cohort study (PERT Mainz). We investigated the composition of PERT and compared, after propensity score matching, patients with acute PE before and after the initiation of PERT at our Medical University Centre. The primary outcome was in-hospital PE-related mortality. Results From 2019 to 2022, 88 patients with acute PE with a PERT decision were registered. Of those, 13 (14.8%) patients died during the in-hospital stay. Patients evaluated by a PERT had a median age of 68; 48.9% were females, and 21.7% suffered from malignancy. Right ventricular dysfunction was present in 76.1% of all patients. In total, 42.0% were classified as intermediate–high-risk PE and 11.4% as high-risk PE. First PERT contact mainly originated from emergency departments (33.3%) and intensive care units (30.0%), followed by chest pain units (21.3%) and regular wards (12.0%). The participation rate of medical specialties demonstrated that cardiologists (100%) or cardiac/vascular surgeons (98.6%) were included in almost all PERT consultations, followed by radiologists (95.9%) and anesthesiologists (87.8%). Compared to the PERT era, more patients in the pre-PERT era were classified as simplified pulmonary embolism severity index (sPESI) ≥ 1 (78.4% vs 71.6%) and as high-risk PE according to ESC 2019 guidelines (18.2% vs. 11.4%). In the pre-PERT era, low- and intermediate-low patients with PE received more frequently advanced reperfusion therapies such as systemic thrombolysis or surgical embolectomy compared to the PERT era (10.7% vs. 2.5%). Patients in the pre-PERT were found to have a considerably higher all-cause mortality and PE-related mortality rate (31.8% vs. 14.8%) compared to patients in the PERT era (22.7% vs. 13.6%). After propensity matching (1:1) by including parameters as age, sex, sPESI, and ESC risk classes, univariate regression analyses demonstrated that the PE management based on a PERT decision was associated with lower risk of all-cause mortality (OR, 0.37 [95%CI 0.18–0.77]; p = 0.009). For PE-related mortality, a tendency for reduction was observed (OR, 0.54 [95%CI 0.24–1.18]; p = 0.121). Conclusion PERT implementation was associated with a lower risk of all-cause mortality rate in patients with acute PE. Large prospective studies are needed further to explore the impact of PERTs on clinical outcomes

Late-Onset Prosthetic Endocarditis with Paraaortic Abscess Caused by Cutibacterium acnes

Cutibacterium acnes, an integral component of the skin’s customary bacterial flora, represents a Gram-positive anaerobic bacterium characterized by its low virulence. Despite its low virulence, the pathogen can cause profound-seated infections as well as infections linked to medical devices. We report a case study of a prosthesis endocarditis accompanied by a paraaortic abscess caused by C. acnes, a development occurring five years prior to composite aortic root and valve replacement. At the point of admission, the patient presented with a combination of symptoms hinting at a subacute progression, such as weight loss, chest pain, and limitations of cardiopulmonary functionality. An anaerobic pathogen, namely C. acnes, was detected in a singular blood culture vial. Since first-line imaging modalities such as echocardiography did not reveal any signs of inflammation, and in the case of a suspected diagnosis for IE, did not show high pretest probability, further diagnostic imaging such as 18F-FDG PET CT was put to use. Here, a highly elevated glucose metabolism around the aortic valve ring was detected, pointing to an inflammatory process. The patient received adjusted intravenous antibiotic therapy over a course of six weeks; he then underwent surgical therapy via re-replacement of the aortic root and valve using a composite conduit. Advanced microbiological analyses, including the amplification of PCR and valve sequencing via 16S rDNA, mainly detected one pathogen: C. acnes. Delayed onset with mild symptoms and laboratory findings is characteristic of infective endocarditis by C. acnes. Due to its high rate of complications, mortality, and morbidity, an infection should not be disregarded as contamination. Recommendations from different studies underline a combination of a positive blood culture and microbiological evidence to differentiate between contamination and true infection in the case of an infection involving C. acnes. Serial blood cultures with prolonged incubation, advanced microbiological analyses, and modified Duke criteria including second-line imaging techniques should be utilized for further evaluation

Parahydrogen induced polarization on a clinical MRI system : polarization transfer of two spin order

Hyperpolarization techniques enhance the nuclear spin polarization and thus allow for new nuclear magnetic resonance applications like in vivo metabolic imaging. One of these techniques is Parahydrogen Induced Polarization (PHIP). It leads to a hyperpolarized 1H spin state which can be transferred to a heteronucleus like 13C by a radiofrequency (RF) pulse sequence. In this work, timing of such a sequence was analyzed and optimized for the molecule hydroxyethyl propionate. The pulse sequence was adapted for the work on a clinical magnetic resonance imaging (MRI) system which is usually equipped only with a single RF transmit channel. Optimal control theory optimizations were performed to achieve an optimized polarization transfer. A drawback of hyperpolarization is its limited lifetime due to relaxation processes. The lifetime can be increased by storing the hyperpolarization in a spin singlet state. The second part of this work therefore addresses the spin singlet state of the Cs-symmetric molecule dimethyl maleate which needs to be converted to the spin triplet state to be detectable. This conversion was realized on a clinical MRI system, both by field cycling and by two RF pulse sequences which were adapted and optimized for this purpose. Using multiple conversions enables the determination of the lifetime of the singlet state as well as the conversion efficiency of the RF pulse sequence. Both, the hyperpolarized 13C spin state and the converted singlet state were utilized for MR imaging. Careful choice of the echo time was shown to be crucial for both molecules.Hyperpolarisationsmethoden verstärken die Kernspinpolarisation und ermöglichen dadurch neue Anwendungen der Kernspinresonanz wie die Bildgebung von Stoffwechselprozessen. Eine dieser Methoden ist die Parawasserstoff Induzierte Polarisation (PHIP), welche einen hyperpolarisierten 1H-Zustand erzeugt. Diese Hyperpolarisation kann durch Sequenzen von Radiofrequenzpulsen auf einen Heterokern wie 13C übertragen werden. In dieser Arbeit wurde die Zeitabstimmung einer solchen Sequenz für das Molekül Hydroxyethylpropionat analysiert und optimiert. Die Pulssequenz wurde für einen klinischen Kernspintomographen angepasst, so dass sie mit einem einzigen Sendekanal verwendet werden kann. Optimierungssimulationen basierend auf der Theorie der optimalen Steuerung wurden durchgeführt, um den Polarisationstransfer zu verbessern. Ein Nachteil der Hyperpolarisation ist, dass sie aufgrund von Relaxationsprozessen nur eine eingeschränkte Lebensdauer hat. Diese kann erhöht werden, indem die Hyperpolarisation in einem Singulett-Zustand gespeichert wird. Der zweite Teil dieser Arbeit befasst sich daher mit dem Singulett-Zustand des Cs-symmetrischen Moleküls Dimethylmaleat, welcher für Messungen in einen Triplett-Zustand überführt werden muss. Diese Konversion wurde in einem klinischen Kernspintomographen zum einen durch eine Magnetfeldvariation zum anderen durch zwei Pulsssequenzen realisiert. Mehrfach aufeinanderfolgende Konversion wurden verwendet, um die Lebensdauer des Singulett-Zustands und die Konversionseffizienz der Pulssequenz zu bestimmen. Beide Möglichkeiten, der hyperpolarisierte 13C-Zustand und der konvertierte Singulett-Zustand, wurden zur Bildgebung verwendet. Die Notwendigkeit einer sorgfältigen Wahl der Echozeit wurde für beide Moleküle gezeigt

Computational Fluid Dynamics Simulations of Contrast Agent Bolus Dispersion in a Coronary Bifurcation: Impact on MRI-Based Quantification of Myocardial Perfusion

Contrast-enhanced first-pass magnetic resonance imaging (MRI) in combination with a tracer kinetic model, for example, MMID4, can be used to determine myocardial blood flow (MBF) and myocardial perfusion reserve (MPR). Typically, the arterial input function (AIF) required for this methodology is estimated from the left ventricle (LV). Dispersion of the contrast agent bolus might occur between the LV and the myocardial tissue. Negligence of bolus dispersion could cause an error in MBF determination. The aim of this study was to investigate the influence of bolus dispersion in a simplified coronary bifurcation geometry including one healthy and one stenotic branch on the quantification of MBF and MPR. Computational fluid dynamics (CFD) simulations were combined with MMID4. Different inlet boundary conditions describing pulsatile and constant flows for rest and hyperemia and differing outflow conditions have been investigated. In the bifurcation region, the increase of the dispersion was smaller than inside the straight vessels. A systematic underestimation of MBF values up to −16.1% for pulsatile flow and an overestimation of MPR up to 7.5% were found. It was shown that, under the conditions considered in this study, bolus dispersion can significantly influence the results of quantitative myocardial MR-perfusion measurements

Magnetic resonance imaging of 1H long lived states derived from parahydrogen induced polarization in a clinical system

Hyperpolarization is a powerful tool to overcome the low sensitivity of nuclear magnetic resonance (NMR). However, applications are limited due to the short lifetime of this non equilibrium spin state caused by relaxation processes. This issue can be addressed by storing hyperpolarization in slowly decaying singlet spin states which was so far mostly demonstrated for non-proton spin pairs, e.g. 13C-13C. Protons hyperpolarized by parahydrogen induced polarization (PHIP) in symmetrical molecules, are very well suited for this strategy because they naturally exhibit a long-lived singlet state. The conversion of the NMR silent singlet spin state to observable magnetization can be achieved by making use of singlet-triplet level anticrossings. In this study, a low-power radiofrequency pulse sequence is used for this purpose, which allows multiple successive singlet-triplet conversions. The generated magnetization is used to record proton images in a clinical magnetic resonance imaging (MRI) system, after 3 min waiting time. Our results may open unprecedented opportunities to use the standard MRI nucleus 1H for e.g. metabolic imaging in the future.Fil: Graafen, Dirk. Max Planck Institute for Polymer Research; Alemania. Johannes Gutenberg University Medical Center; AlemaniaFil: Franzoni, Maria Belen. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Max Planck Institute for Polymer Research; AlemaniaFil: Schreiber, Laura M.. Johannes Gutenberg University Medical Center; AlemaniaFil: Spiess, Hans W.. Max Planck Institute for Polymer Research; AlemaniaFil: Münnemann, Kerstin. Max Planck Institute for Polymer Research; Alemani

Optimization of the Reconstruction Settings for Low-Dose Ultra-High-Resolution Photon-Counting Detector CT of the Lungs

Photon-counting detector computed tomography (PCD-CT) yields improved spatial resolution. The combined use of PCD-CT and a modern iterative reconstruction method, known as quantum iterative reconstruction (QIR), has the potential to significantly improve the quality of lung CT images. In this study, we aimed to analyze the impacts of different slice thicknesses and QIR levels on low-dose ultra-high-resolution (UHR) PCD-CT imaging of the lungs. Our study included 51 patients with different lung diseases who underwent unenhanced UHR-PCD-CT scans. Images were reconstructed using three different slice thicknesses (0.2, 0.4, and 1.0 mm) and three QIR levels (2–4). Noise levels were determined in all reconstructions. Three raters evaluated the delineation of anatomical structures and conspicuity of various pulmonary pathologies in the images compared to the clinical reference reconstruction (1.0 mm, QIR-3). The highest QIR level (QIR-4) yielded the best image quality. Reducing the slice thickness to 0.4 mm improved the delineation and conspicuity of pathologies. The 0.2 mm reconstructions exhibited lower image quality due to high image noise. In conclusion, the optimal reconstruction protocol for low-dose UHR-PCD-CT of the lungs includes a slice thickness of 0.4 mm, with the highest QIR level. This optimized protocol might improve the diagnostic accuracy and confidence of lung imaging

Quantum iterative reconstruction on a photon-counting detector CT improves the quality of hepatocellular carcinoma imaging

Abstract Background Excellent image quality is crucial for workup of hepatocellular carcinoma (HCC) in patients with liver cirrhosis because a signature tumor signal allows for non-invasive diagnosis without histologic proof. Photon-counting detector computed tomography (PCD-CT) can enhance abdominal image quality, especially in combination with a novel iterative reconstruction algorithm, quantum iterative reconstruction (QIR). The purpose of this study was to analyze the impact of different QIR levels on PCD-CT imaging of HCC in both phantom and patient scans. Methods Virtual monoenergetic images at 50 keV were reconstructed using filtered back projection and all available QIR levels (QIR 1–4). Objective image quality properties were investigated in phantom experiments. The study also included 44 patients with triple-phase liver PCD-CT scans of viable HCC lesions. Quantitative image analysis involved assessing the noise, contrast, and contrast-to-noise ratio of the lesions. Qualitative image analysis was performed by three raters evaluating noise, artifacts, lesion conspicuity, and overall image quality using a 5-point Likert scale. Results Noise power spectra in the phantom experiments showed increasing noise suppression with higher QIR levels without affecting the modulation transfer function. This pattern was confirmed in the in vivo scans, in which the lowest noise levels were found in QIR-4 reconstructions, with around a 50% reduction in median noise level compared with the filtered back projection images. As contrast does not change with QIR, QIR-4 also yielded the highest contrast-to-noise ratios. With increasing QIR levels, rater scores were significantly better for all qualitative image criteria (all p < .05). Conclusions Without compromising image sharpness, the best image quality of iodine contrast optimized low-keV virtual monoenergetic images can be achieved using the highest QIR level to suppress noise. Using these settings as standard reconstruction for HCC in PCD-CT imaging might improve diagnostic accuracy and confidence