Lifelike phantoms for assessing clinical image quality and dose reduction capabilities of a deep learning CT reconstruction algorithm.

Deep learning CT reconstruction (DLR) has become increasingly popular as a method for improving image quality and reducing radiation exposure. Due to their nonlinear nature, these algorithms result in resolution and noise performance which are object-dependent. Therefore, traditional CT phantoms, which lack realistic tissue morphology, have become inadequate for assessing clinical imaging performance.

Impact of scatter radiation on spectral quantification performance of first- and second-generation dual-layer spectral computed tomography.

Objective: To assess the impact of scatter radiation on quantitative performance of first and second-generation dual-layer spectral computed tomography (DLCT) systems.

Method: A phantom with two iodine inserts (1 and 2 mg/mL) configured to intentionally introduce high scattering conditions was scanned with a first- and second-generation DLCT. Collimation widths (maximum of 4 cm for first generation and 8 cm for second generation) and radiation dose levels were varied.

Spectral performance evaluation of a second-generation spectral detector CT.

Purpose: The aim of this study was to characterize a second-generation wide-detector dual-layer spectral computed tomography (CT) system for material quantification accuracy, acquisition parameter and patient size dependencies, and tissue characterization capabilities.

Methods: A phantom with multiple tissue-mimicking and material-specific inserts was scanned with a dual-layer spectral detector CT using different tube voltages, collimation widths, radiation dose levels, and size configurations. Accuracy of iodine density maps and virtual monoenergetic images (MonoE) were investigated.

Diagnostic accuracy of virtual non-contrast CT for aortic valve stenosis severity evaluation.

Background: Computed tomography aortic valve calcium (AVC) score has accepted value for diagnosing and predicting outcomes in aortic stenosis (AS). Multi-energy CT (MECT) allows virtual non-contrast (VNC) reconstructions from contrast scans. We aim to compare the VNC-AVC score to the true non-contrast (TNC)-AVC score for assessing AS severity.

Patient-derived PixelPrint phantoms for evaluating clinical imaging performance of a deep learning CT reconstruction algorithm.

Objective: Deep learning reconstruction (DLR) algorithms exhibit object-dependent resolution and noise performance. Thus, traditional geometric CT phantoms cannot fully capture the clinical imaging performance of DLR. This study uses a patient-derived 3D-printed PixelPrint lung phantom to evaluate a commercial DLR algorithm across a wide range of radiation dose levels.

Phantom-based quantification of the spectral accuracy in dual-layer spectral CT for pediatric imaging at 100 kVp.

Background: To determine the spectral accuracy in detector-based dual-energy CT (DECT) at 100 kVp and wide (8 cm) collimation width for dose levels and object sizes relevant to pediatric imaging.

Methods: A spectral CT phantom containing tissue-equivalent materials and iodine inserts of varying concentrations was scanned on the latest generation detector-based DECT system. Two 3D-printed extension rings were used to mimic varying pediatric patient sizes.

The Effect of Age on Fat Distribution in the Neck Using Volumetric Computed Tomography.

Background: Neck fat distribution plays an important role in aging, yet how fat distribution changes with age is largely unknown. This study used volumetric computed tomography in live patients to characterize neck fat volume and distribution in young and elderly women.

Methods: A retrospective analysis was conducted of head and neck computed tomographic angiographs of 20 young (aged 20 to 35 years) and 20 old (aged 65 to 89 years) women.

Principles and applications of multienergy CT: Report of AAPM Task Group 291.

In x-ray computed tomography (CT), materials with different elemental compositions can have identical CT number values, depending on the mass density of each material and the energy of the detected x-ray beam. Differentiating and classifying different tissue types and contrast agents can thus be extremely challenging. In multienergy CT, one or more additional attenuation measurements are obtained at a second, third or more energy.

Virtual Noncontrast Images From Portal Venous Phase Spectral-Detector CT Acquisitions for Adrenal Lesion Characterization.

Objective: The aim of this study was to investigate if Hounsfield unit (HU) values from virtual noncontrast (VNC) images derived from portal venous phase spectral-detector computed tomography can help to differentiate adrenal adenomas and metastases.

Methods: Spectral-detector computed tomography datasets of 33 patients with presence of adrenal lesions and standard of reference for lesion origin by follow-up/prior examinations or dedicated magnetic resonance imaging were included. Conventional and VNC images were reconstructed from the same scan.

High correlation between radiation dose estimates for 256-slice CT obtained by highly parallelized hybrid Monte Carlo computation and solid-state metal-oxide semiconductor field-effect transistor measurements in physical anthropomorphic phantoms.

Purpose: Accurate, patient-specific radiation dosimetry for CT scanning is critical to optimize radiation doses and balance dose against image quality. While Monte Carlo (MC) simulation is often used to estimate doses from CT, comparison of estimates to experimentally measured values is lacking for advanced CT scanners incorporating novel design features. We aimed to compare radiation dose estimates from MC simulation to doses measured in physical anthropomorphic phantoms using metal-oxide semiconductor field-effect transistors (MOSFETs) in a 256-slice CT scanner.

Virtual monoenergetic images from spectral detector CT as a surrogate for conventional CT images: Unaltered attenuation characteristics with reduced image noise.

Objective: This study aimed to identify the energy level of virtual monoenergetic images (VMI) that closest represents conventional images (CI) in order to demonstrate that these images provide improved image quality in terms of noise and Signal-to-noise ratio (SD/SNR) while attenuation values (HU) remain unaltered as compared to CI.

Methods: 60 and 30 patients with contrast-enhanced (CE) and non-enhanced (NCE) spectral detector CT (SDCT) of the abdomen were included in this retrospective, IRB-approved study. CI and VMI of 66-74 keV as well as quantitative iodine maps were reconstructed (Q-IodMap).

The role of advanced reconstruction algorithms in cardiac CT.

Non-linear iterative reconstruction (IR) algorithms have been increasingly incorporated into clinical cardiac CT protocols at institutions around the world. Multiple IR algorithms are available commercially from various vendors. IR algorithms decrease image noise and are primarily used to enable lower radiation dose protocols.

Objective image characterization of a spectral CT scanner with dual-layer detector.

This work evaluated the performance of a detector-based spectral CT system by obtaining objective reference data, evaluating attenuation response of iodine and accuracy of iodine quantification, and comparing conventional CT and virtual monoenergetic images in three common phantoms. Scanning was performed using the hospital's clinical adult body protocol. Modulation transfer function (MTF) was calculated for a tungsten wire and visual line pair targets were evaluated.

Update on Cardiovascular Applications of Multienergy CT.

Advances in scanner technology enabling shorter scan times, improvements in spatial and temporal resolution, and more dose-efficient data reconstruction coupled with rapidly growing evidence from clinical trials have established computed tomography (CT) as an important imaging modality in the evaluation of cardiovascular disorders. Multienergy (or spectral or dual-energy) CT is a relatively recent advance in which attenuation data from different energies are used to characterize materials beyond what is possible at conventional CT. Current technologies for multienergy CT are either source based (ie, dual source, rapid kilovoltage switching, dual spin, and split beam) or detector based (ie, dual layer and photon counting), and material-based decomposition occurs in either image or projection space.

Calibration and error analysis of metal-oxide-semiconductor field-effect transistor dosimeters for computed tomography radiation dosimetry.

Purpose: Metal-oxide-semiconductor field-effect transistors (MOSFETs) serve as a helpful tool for organ radiation dosimetry and their use has grown in computed tomography (CT). While different approaches have been used for MOSFET calibration, those using the commonly available 100 mm pencil ionization chamber have not incorporated measurements performed throughout its length, and moreover, no previous work has rigorously evaluated the multiple sources of error involved in MOSFET calibration. In this paper, we propose a new MOSFET calibration approach to translate MOSFET voltage measurements into absorbed dose from CT, based on serial measurements performed throughout the length of a 100-mm ionization chamber, and perform an analysis of the errors of MOSFET voltage measurements and four sources of error in calibration.

Cardiac-Specific Conversion Factors to Estimate Radiation Effective Dose From Dose-Length Product in Computed Tomography.

Objectives: This study sought to determine updated conversion factors (k-factors) that would enable accurate estimation of radiation effective dose (ED) for coronary computed tomography angiography (CTA) and calcium scoring performed on 12 contemporary scanner models and current clinical cardiac protocols and to compare these methods to the standard chest k-factor of 0.014 mSv·mGycm.

Background: Accurate estimation of ED from cardiac CT scans is essential to meaningfully compare the benefits and risks of different cardiac imaging strategies and optimize test and protocol selection.

Spectral detector CT for cardiovascular applications.

Spectral detector computed tomography (SDCT) is a novel technology that uses two layers of detectors to simultaneously collect low and high energy data. Spectral data is used to generate conventional polyenergetic images as well as dedicated spectral images including virtual monoenergetic and material composition (iodine-only, virtual unenhanced, effective atomic number) images. This paper provides an overview of SDCT technology and a description of some spectral image types.

Artifacts at Cardiac CT: Physics and Solutions.

Computed tomography is vulnerable to a wide variety of artifacts, including patient- and technique-specific artifacts, some of which are unique to imaging of the heart. Motion is the most common source of artifacts and can be caused by patient, cardiac, or respiratory motion. Cardiac motion artifacts can be reduced by decreasing the heart rate and variability and the duration of data acquisition; adjusting the placement of the data window within a cardiac cycle; performing single-heartbeat scanning; and using multisegment reconstruction, motion-correction algorithms, and electrocardiographic editing.

Assessing Level of Agreement for Atherosclerotic Cardiovascular Disease Risk Categorization Between Coronary Artery Calcium Score and the American College of Cardiology/American Heart Association Cardiovascular Prevention Guidelines and the Potential Impact on Treatment Recommendations.

The 2013 American College of Cardiology/American Heart Association cardiovascular prevention guidelines use a new pooled cohort equation (PCE) to predict 10-year risk of atherosclerotic cardiovascular disease (ASCVD) events which form the basis of treatment recommendations. Coronary artery calcium score (CACS) has been proposed as a means to assess atherosclerotic risk. We sought to study the level of agreement in predicted ASCVD risk by CACS and PCE-calculated models and the potential impact on therapy of additional CACS testing.

Practical considerations for optimizing cardiac computed tomography protocols for comprehensive acquisition prior to transcatheter aortic valve replacement.

Transcatheter aortic valve replacement (TAVR) is performed frequently in patients with severe, symptomatic aortic stenosis who are at high risk or inoperable for open surgical aortic valve replacement. Computed tomography angiography (CTA) has become the gold standard imaging modality for pre-TAVR cardiac anatomic and vascular access assessment. Traditionally, cardiac CTA has been most frequently used for assessment of coronary artery stenosis, and scanning protocols have generally been tailored for this purpose.

Absence of coronary sinus tributaries in ischemic cardiomyopathy: An insight from multidetector computed tomography cardiac venographic study.

Objective: Cardiac resynchronization therapy (CRT) is an important therapeutic strategy in heart failure. However, there is a high incidence of lead implantation failure and suboptimal response, particularly in ischemic cardiomyopathy. This failure rate may partly be secondary to lack of suitable coronary sinus branches for lead implantation.

A pilot study of patient-specific cardiovascular MDCT dose maps and their utility in estimating patient-specific organ and effective doses in obese patients.

Background: Estimates of effective dose (E) for cardiovascular CT are obtained from a scanner-provided dose metric, the dose-length product (DLP), and a conversion factor. These estimates may not adequately represent the risk of a specific scan to obese adults.

Objective: Our objective was to create dose maps sensitive to patient size and anatomy in the irradiated region from a patient's own CT images and compare measured E (EDoseMap) to doses determined from standard DLP conversion (EDLP) in obese adults.

A pilot study investigating the effect of parathyroidectomy on arterial stiffness and coronary artery calcification in patients with primary hyperparathyroidism.

Background: Arterial stiffness (AS) and coronary artery calcification (CAC) are predictors of cardiovascular risk and can be measured noninvasively. The aim of this study was to analyze the effects of parathyroidectomy on AS and CAC in patients with primary hyperparathyroidism (PHP).

Methods: This prospective, institutional review board-approved study included 21 patients with PHP, who underwent parathyroidectomy.

Manual, semiautomated, and fully automated measurement of the aortic annulus for planning of transcatheter aortic valve replacement (TAVR/TAVI): analysis of interchangeability.

Background: Preprocedural 3-dimensional CT imaging of the aortic annular plane plays a critical role for transcatheter aortic valve replacement (TAVR) planning; however, manual reconstructions are complex. Automated analysis software may improve reproducibility and agreement between readers but is incompletely validated.

Methods: In 110 TAVR patients (mean age, 81 years; 37% female) undergoing preprocedural multidetector CT, automated reconstruction of the aortic annular plane and planimetry of the annulus was performed with a prototype of now commercially available software (syngo.