Comparison of Hounsfield Unit variability between two same model photon counting CT detector systems. A phantom study applied to lung CT.

Accurate quantification of lung density, in Hounsfield Units (HU), is of high importance to monitor progression of diseases such as emphysema using chest CT imaging. Reproducibility of HU quantification on independent photon counting detector CT (PCD-CT) systems with a focus on lung imaging have not yet been evaluated. We thus aimed to evaluate HU reproducibility on 2 independent PCD-CT systems using a repeatable phantom setup with identical acquisition and image reconstruction settings.

Photon counting CT clinical adoption, integration, and workflow.

Photon counting CT was recently introduced into clinical practice [Rajendran K, Petersilka M, Henning A, Shanblatt ER, Schmidt B, Flohr TG, Ferrero A, Baffour F, Diehn FE, Yu L, Rajiah P, Fletcher JG, Leng S, McCollough CH. First Clinical Photon-counting Detector CT System: Technical Evaluation. Radiology 2022;303(1):130-138.

Intraindividual Comparison of Dose Reduction and Coronary Calcium Scoring Accuracy Using Kilovolt-independent and Tin Filtration CT Protocols.

Purpose To investigate the ability of kilovolt-independent (hereafter, kV-independent) and tin filter spectral shaping to accurately quantify the coronary artery calcium score (CACS) and radiation dose reductions compared with the standard 120-kV CT protocol. Materials and Methods This prospective, blinded reader study included 201 participants (mean age, 60 years ± 9.8 [SD]; 119 female, 82 male) who underwent standard 120-kV CT and additional kV-independent and tin filter research CT scans from October 2020 to July 2021.

Multi-institutional Protocol Guidance for Pediatric Photon-counting CT.

Performing CT in children comes with unique challenges such as greater degrees of patient motion, smaller and densely packed anatomy, and potential risks of radiation exposure. The technical advancements of photon-counting detector (PCD) CT enable decreased radiation dose and noise, as well as increased spatial and contrast resolution across all ages, compared with conventional energy-integrating detector CT. It is therefore valuable to review the relevant technical aspects and principles specific to protocol development on the new PCD CT platform to realize the potential benefits for this population.

Standardizing technical parameters and terms for abdominopelvic photon-counting CT: laying the groundwork for innovation and evidence sharing.

Photon-counting detector CT (PCD-CT) is a new technology that has multiple diagnostic benefits including increased spatial resolution, iodine signal, and radiation dose efficiency, as well as multi-energy imaging capability, but which also has unique challenges in abdominal imaging. The purpose of this work is to summarize key features, technical parameters, and terms, which are common amongst current abdominopelvic PCD-CT systems and to propose standardized terminology (where none exists). In addition, user-selectable protocol parameters are highlighted to facilitate both scientific evaluation and early clinical adoption.

Technology Characterization Through Diverse Evaluation Methodologies: Application to Thoracic Imaging in Photon-Counting Computed Tomography.

Objective: Different methods can be used to condition imaging systems for clinical use. The purpose of this study was to assess how these methods complement one another in evaluating a system for clinical integration of an emerging technology, photon-counting computed tomography (PCCT), for thoracic imaging.

Methods: Four methods were used to assess a clinical PCCT system (NAEOTOM Alpha; Siemens Healthineers, Forchheim, Germany) across 3 reconstruction kernels (Br40f, Br48f, and Br56f).

First experience of evaluation of the impact of high-matrix size reconstruction in image quality in arterial CT runoff studies of the lower extremities.

Objectives: To determine whether image reconstruction with a higher matrix size improves image quality for lower extremity CTA studies.

Methods: Raw data from 50 consecutive lower extremity CTA studies acquired on two MDCT scanners (SOMATOM Flash, Force) in patients evaluated for peripheral arterial disease (PAD) were retrospectively collected and reconstructed with standard (512 × 512) and higher resolution (768 × 768, 1024 × 1024) matrix sizes. Five blinded readers reviewed representative transverse images in randomized order (150 total).

Comparison of Radiation Dose and Image Quality of Pediatric High-Resolution Chest CT Between Photon-Counting Detector CT and Energy-Integrated Detector CT: A Matched Study.

Photon-counting detector (PCD) CT has been shown to reduce radiation dose and improve image quality in adult chest CT examinations; its potential impact in pediatric CT is not well documented. The purpose of our study was to compare radiation dose, objective image quality, and subjective image quality of PCD CT and energy-integrating detector (EID) CT in children undergoing high-resolution CT (HRCT) of the chest. This retrospective study included 27 children (median age, 3.

Liver fat quantification in photon counting CT in head to head comparison with clinical MRI - First experience.

Purpose: To compare liver fat quantification between MRI and photon-counting CT (PCCT).

Method: A cylindrical phantom with inserts containing six concentrations of oil (0, 10, 20, 30, 50 and 100%) and oil-iodine mixtures (0, 10, 20, 30 and 50% fat +3 mg/mL iodine) was imaged with a PCCT (NAEOTOM Alpha) and a 1.5 T MRI system (MR 450w, IDEAL-IQ sequence), using clinical parameters.

Flat-panel dual-energy head computed tomography in the angiography suite after thrombectomy for acute stroke: A clinical feasibility study.

Background: Management of large vessel occlusion (LVO) patients after thrombectomy is affected by the presence of intracranial hemorrhage (ICH) on post-procedure imaging. Differentiating contrast staining from hemorrhage on post-procedural imaging has been facilitated by dual-energy computed tomography (DECT), traditionally performed in dedicated computed tomography (CT) scanners with subsequent delays in treatment. We employed a novel method of DECT using the Siemens cone beam CT (DE-CBCT) in the angiography suite to evaluate for post-procedure ICH and contrast extravasation.

Coronary Artery Calcium Evaluation Using New Generation Photon-counting Computed Tomography Yields Lower Radiation Dose Compared With Standard Computed Tomography.

Prospective head-to-head comparison of coronary calcium scores between standard computed tomography (CT) and photon-counting CT show no significant differences, while photon-counting CT administers substantially lower radiation dose.

Sex differences in machine learning computed tomography-derived fractional flow reserve.

Coronary computed tomography angiography (CCTA) derived machine learning fractional flow reserve (ML-FFR) can assess the hemodynamic significance of coronary artery stenoses. We aimed to assess sex differences in the association of ML-FFR and incident cardiovascular outcomes. We studied a retrospective cohort of consecutive patients who underwent clinically indicated CCTA and single photon emission computed tomography (SPECT).

Interoperator reliability of an on-site machine learning-based prototype to estimate CT angiography-derived fractional flow reserve.

Background: Advances in CT and machine learning have enabled on-site non-invasive assessment of fractional flow reserve (FFR).

Purpose: To assess the interoperator and intraoperator variability of coronary CT angiography-derived FFR using a machine learning-based postprocessing prototype.

Materials And Methods: We included 60 symptomatic patients who underwent coronary CT angiography.

Comparison of 100-Kilovoltage Tin Filtration With Advanced Modeled Iterative Reconstruction Protocol to an Automated Kilovoltage Selection With Filtered Back Projection Protocol on Radiation Dose and Image Quality in Pediatric Noncontrast-Enhanced Chest Computed Tomography.

Objective: The aim of the study was to compare effects of a 100-kilovoltage (kVp) tin filtration (Sn100kVp) with Advanced Modeled Iterative Reconstruction (ADMIRE) protocol to an automated kVp selection and filtered back projection (FBP) protocol on radiation dose and image quality of in noncontrast-enhanced pediatric chest computed tomography (CT).

Methods: This retrospective study included 55 children (12 ± 6 years) undergoing baseline imaging using automated kVp selection with FBP on a second-generation dual-source CT scanner and follow-up CT using Sn100kVp with ADMIRE on a third-generation dual-source CT scanner. The volume CT dose index, dose length product, size-specific dose estimate, and milliamperage were compared.

Time-resolved, Cardiac-gated Computed Tomography After Endovascular Ascending Aortic and Arch Repair.

Purpose: Better time-resolved imaging of stent grafts in the ascending aorta and arch accounting for cardiac motion is necessary to understand device-related complications and endoleaks. This report describes dynamic time-resolved computed tomographic angiography (d-CTA) and its combination with electrocardiography gating (d-gated CTA) to image stent grafts in the ascending aorta and to characterize endoleaks more clearly.

Description: d-CTA involves multiple scans acquired at different time points along the contrast enhancement curve.

Prognostic Value of Computed Tomography-Derived Fractional Flow Reserve Comparison With Myocardial Perfusion Imaging.

Objectives: The aim of this study was to compare the incremental prognostic value of coronary computed tomography (CT) angiography (CCTA)-derived machine learning fractional flow reserve CT (ML-FFRct) versus that of ischemia detected on single-photon emission-computed tomography (SPECT) myocardial perfusion imaging (MPI) on incident cardiovascular outcomes.

Background: SPECT MPI and ML-FFRct are noninvasive tools that can assess the hemodynamic significance of coronary atherosclerotic disease.

Methods: We studied a retrospective cohort of consecutive patients who underwent clinically indicated CCTA and SPECT MPI.

A Clinically Driven Task-Based Comparison of Photon Counting and Conventional Energy Integrating CT for Soft Tissue, Vascular, and High-Resolution Tasks.

Photon-counting CT detectors are the next step in advancing CT system development and will replace the current energy integrating detectors (EID) in CT systems in the near future. In this context, the performance of PCCT was compared to EID CT for three clinically relevant tasks: abdominal soft tissue imaging, where differentiating low contrast features is important; vascular imaging, where iodine detectability is critical; and, high-resolution skeletal and lung imaging. A multi-tiered phantom was imaged on an investigational clinical PCCT system (Siemens Healthineers) across different doses using three imaging modes: macro and ultra-high resolution (UHR) PCCT modes and EID CT.

Comparison of radiation dose and image quality between contrast-enhanced single- and dual-energy abdominopelvic computed tomography in children as a function of patient size.

Background: Widespread adoption of dual-energy computed tomography (DECT) requires evidence it does not cause higher radiation dose than conventional single-energy CT (SECT). While a few publications involving pediatric patients exist, most have focused on small cohorts. Hence, there is still a need for studies that ascertain what radiation doses are expected in larger populations that include representative ranges of patient sizes and ages.

Evaluating renal lesions using deep-learning based extension of dual-energy FoV in dual-source CT-A retrospective pilot study.

Purpose: Dual-source (DS) CT, dual-energy (DE) field of view (FoV) is limited to the size of the smaller detector array. The purpose was to establish a deep learning-based approach to DE extrapolation by estimating missing image data using data from both tubes to evaluate renal lesions.

Method: A DE extrapolation deep-learning (DEEDL) algorithm had been trained on DECT data of 50 patients using a DSCT with DE-FoV = 33 cm (Somatom Flash).

Can radiomic analysis of a single-phase dual-energy CT improve the diagnostic accuracy of differentiating enhancing from non-enhancing small renal lesions?

Background: The value of dual-energy computed tomography (DECT)-based radiomics in renal lesions is unknown.

Purpose: To develop DECT-based radiomic models and assess their incremental values in comparison to conventional measurements for differentiating enhancing from non-enhancing small renal lesions.

Material And Methods: A total of 349 patients with 519 small renal lesions (390 non-enhancing, 129 enhancing) who underwent contrast-enhanced nephrographic phase DECT examinations between June 2013 and January 2020 on multiple DECT platforms were retrospectively recruited.

Deep learning based spectral extrapolation for dual-source, dual-energy x-ray computed tomography.

Purpose: Data completion is commonly employed in dual-source, dual-energy computed tomography (CT) when physical or hardware constraints limit the field of view (FoV) covered by one of two imaging chains. Practically, dual-energy data completion is accomplished by estimating missing projection data based on the imaging chain with the full FoV and then by appropriately truncating the analytical reconstruction of the data with the smaller FoV. While this approach works well in many clinical applications, there are applications which would benefit from spectral contrast estimates over the larger FoV (spectral extrapolation)-e.

Variability of quantitative measurements of metastatic liver lesions: a multi-radiation-dose-level and multi-reader comparison.

Purpose: To evaluate the variability of quantitative measurements of metastatic liver lesions by using a multi-radiation-dose-level and multi-reader comparison.

Methods: Twenty-three study subjects (mean age, 60 years) with 39 liver lesions who underwent a single-energy dual-source contrast-enhanced staging CT between June 2015 and December 2015 were included. CT data were reconstructed with seven different radiation dose levels (ranging from 25 to 100%) on the basis of a single CT acquisition.

Reproducibility of CT Radiomic Features within the Same Patient: Influence of Radiation Dose and CT Reconstruction Settings.

Background Results of recent phantom studies show that variation in CT acquisition parameters and reconstruction techniques may make radiomic features largely nonreproduceable and of limited use for prognostic clinical studies. Purpose To investigate the effect of CT radiation dose and reconstruction settings on the reproducibility of radiomic features, as well as to identify correction factors for mitigating these sources of variability. Materials and Methods This was a secondary analysis of a prospective study of metastatic liver lesions in patients who underwent staging with single-energy dual-source contrast material-enhanced staging CT between September 2011 and April 2012.

Performance evaluation of computed tomography systems: Summary of AAPM Task Group 233.

Background: The rapid development and complexity of new x-ray computed tomography (CT) technologies and the need for evidence-based optimization of image quality with respect to radiation and contrast media dose call for an updated approach towards CT performance evaluation.

Aims: This report offers updated testing guidelines for testing CT systems with an enhanced focus on the operational performance including iterative reconstructions and automatic exposure control (AEC) techniques.

Materials And Methods: The report was developed based on a comprehensive review of best methods and practices in the scientific literature.

Dual-Energy CT in Children: Imaging Algorithms and Clinical Applications.

Dual-energy CT enables the simultaneous acquisition of CT images at two different x-ray energy spectra. By acquiring high- and low-energy spectral data, dual-energy CT can provide unique qualitative and quantitative information about tissue composition, allowing differentiation of multiple materials including iodinated contrast agents. The two dual-energy CT postprocessing techniques that best exploit the advantages of dual-energy CT in children are the material-decomposition images (which include virtual nonenhanced, iodine, perfused lung blood volume, lung vessel, automated bone removal, and renal stone characterization images) and virtual monoenergetic images.