Task‐based evaluation of axial and multiplanar reconstructions in computed tomography: A volumetric analysis of spatial resolution, noise, and detectability

Assessing Image Quality Differences Between Single-Energy and Dual-Energy Computed Tomography in Head, Thoracic, and Abdominal Scans: A Systematic Review

Background Computed tomography (CT) is an essential imaging modality for evaluating head, thoracic, and abdominal conditions. High-quality images are crucial for accurate diagnosis and clinical decision-making. Single-energy CT (SECT) is widely used but is limited by beam-hardening artifacts and suboptimal contrast resolution, particularly in complex anatomical regions. Dual-energy CT (DECT) acquires data at two energy levels, allowing spectral analysis that can improve image quality. Objective This article aims to systematically compare image quality between SECT and DECT in head, thoracic, and abdominal CT, focusing on contrast resolution, image noise, artifact reduction, and diagnostic clarity. Materials and Methods A structured literature search was conducted to identify studies directly comparing SECT and DECT. Included studies were analyzed for image quality outcomes across different anatomical regions and clinical tasks, considering the influence of acquisition protocols and reconstruction methods. Results DECT generally improved contrast-to-noise ratio and reduced beam-hardening artifacts, especially in complex or contrast-enhanced regions. However, benefits varied by anatomical area and technical implementation. Optimized SECT protocols often achieved comparable image quality, emphasizing the importance of protocol refinement. Conclusion DECT offers potential advantages over SECT in selected applications, but its performance depends on careful optimization of acquisition and reconstruction parameters. Tailored, evidence-based protocol selection is essential to maximize clinical benefits.

A commissioning workflow for quantitative ¹⁷⁷Lu SPECT/CT across different Siemens scanner–reconstruction configurations

The accuracy of quantitative lutetium-177 single-photon emission computed tomography/computed tomography (¹⁷⁷Lu SPECT/CT) depends on the imaging system, acquisition protocol, reconstruction algorithm, and calibration strategy. This study aimed to develop and evaluate a practical commissioning workflow to optimize ¹⁷⁷Lu imaging across different commercial scanner–reconstruction configurations. Three Siemens workflows were evaluated: FLASH3D and xSPECT Quant on the Symbia Intevo Bold, and FLASH3D+ on the Symbia Pro.specta. A uniform phantom was used to assess image noise and derive calibration factors for the ordered-subset expectation maximization (OSEM)-based reconstructions. Recovery coefficients (RCs) were evaluated via an International Electrotechnical Commission/National Electrical Manufacturers Association phantom at various sphere-to-background ratios and modeled using a three-parameter logistic function for partial volume correction. Reconstruction parameters were optimized by jointly evaluating RC convergence and image noise, followed by quantitative validation using an anthropomorphic phantom. OSEM-based workflows showed a predictable dependence on equivalent iterations, yielding lower image noise. Conversely, xSPECT Quant exhibited complex parameter dependence and higher noise, but provided superior activity recovery—with RCs closer to unity—and the lowest quantification errors during validation. A reconstruction setting of two subsets and 30 iterations was selected for all workflows. For FLASH3D and FLASH3D+, this configuration provided RCs closest to unity while maintaining the coefficient of variation below the predefined 15% threshold. The same setting was adopted for xSPECT Quant to ensure methodological consistency despite its intrinsically higher image noise. This commissioning workflow provides a practical framework for local ¹⁷⁷Lu SPECT/CT optimization. Among the configurations, xSPECT Quant yielded higher recovery coefficients and lower quantification errors, albeit with increased noise. These findings highlight the need for locally optimized protocols for patient-specific dosimetry and do not establish the general superiority of any one reconstruction algorithm.

Image-quality optimization for late iodine enhancement with photon-counting CT: impact of spectral analysis and reconstruction parameters.

Quantification of image quality and partial volume effect along the axial field-of-view of uMI Panorama GS PET/CT system for multiple radionuclides.

PURPOSE The comprehensive knowledge of how the distinct physical decay characteristics of each radionuclide shape their image quality performance is essential for tailoring acquisition protocols and ensuring optimal clinical applications. Understanding the spatial dependence of the contrast recovery coefficient (CRC) is a prerequisite for robust quantitative image analyses and accurate clinical interpretations, since the partial volume effect (PVE) and the count rate vary along the axial field of view (AFOV). Image quality assessments with various radionuclides were performed on the uMI Panorama GS PET/CT system, with the CRC profile across its extended AFOV also evaluated. METHODS Following the NEMA NU 2-2018 standard, the image quality was assessed using the NEMA IEC (NEC) Body Phantom with 18F, 64Cu, 68Ga, 89Zr, 124I, and 90Y. The CRC, the background variability (BV), and the lung residual error were measured to quantify the image quality. CRCs were sequentially measured at four axial offsets: 1/2, 1/4, 1/8, and 1/16 of the AFOV. The impact of the radionuclide-specific PSF (point spread function) modeling on the CRC was evaluated by comparing PET images reconstructed with and without PSF modeling. RESULTS The assessment demonstrated comparable image qualities for 18F, 64Cu, 68Ga, 89Zr, 124I, while 90Y showed a similar CRC but a higher BV and a higher lung residual error, attributable to its low positron branching ratio. The BV and lung residual error increased with increasing axial distance from the AFOV center, whereas CRCs for larger spheres remained stable across AFOV positions; small-sphere CRC measurements exhibited increased dispersion toward the periphery due to reduced count statistics. The PSF modeling significantly improved CRCs for 68Ga and 124I, consistent with their long positron ranges. CONCLUSIONS All investigated radionuclides were effectively imaged on the uMI Panorama GS PET/CT system. The AFOV uniformity was quantitatively evaluated based on CRC measurements obtained at multiple positions along the AFOV.

Dual-energy CT with metal artifact reduction for post-EVAR CTA surveillance: a prospective study with image quality analysis.

Impact of acquisition parameters in photon-counting computed tomography on the stability of virtual monoenergetic attenuation values and effective atomic number: a phantom study.

OBJECTIVE Photon-counting CT (PCCT) can generate virtual monoenergetic images (VMI) and effective atomic number (Zeff), demonstrating considerable potential for tissue quantification. However, the influence of key acquisition parameters on the stability of these quantitative metrics has not been fully elucidated. This study aimed to evaluate the reliability of VMI CT numbers and Zeff in abdominal organs under varying tube voltage, image quality (IQ) level, and pitch. METHODS An adult male anthropomorphic abdominal phantom (Kyoto Kagaku CTU-41) was scanned using PCCT. The reference protocol was 120 kVp, image quality level (IQ level) 145, and pitch 1. Eight additional protocols were acquired by independently altering tube voltage (140 kVp, 90 kVp, Sn100 kVp), IQ level (115, 85, 55, 25), and pitch (3). VMI were reconstructed at 40, 60, 70, and 100 keV, and CT numbers and Zeff were measured in multiple organs. Differences from the reference protocol were calculated to assess the reliability of these quantitative indices under modified scan conditions. RESULTS Across all protocols, VMI attenuation showed excellent correlation with the reference protocol (r ≥ 0.996). For IQ levels of 115, 85, and 55, all absolute CT number deviations were below 5 HU; at IQ level 25, only two measurements fell within the 5-10 HU range. At 140 kVp, all absolute deviations were below 5 HU. For the 90 kVp protocol, the prostate deviation at 40 keV was -11.33 HU, and five other measurements ranged between 5 and 10 HU. With the Sn100 kVp protocol, absolute deviations of the L1 vertebra and prostate exceeded 10 HU at 60 keV (L1 reached 19.33 HU), and three additional measurements were between 5 and 10 HU. Pitch alteration caused the greatest variability: only 75% of measurements had absolute deviations within 10 HU and 67.5% within 5 HU; deviations were prominent on 40 keV images, with the L1 vertebra reaching -41 HU. The intraclass correlation coefficient for Zeff was ≥0.999 under all conditions. Zeff deviations were within 0.2 for 140 kVp and IQ levels of 115, 85, and 55; the pancreas deviation was 0.34 at IQ level 25; at pitch 3, the maximum deviation (L1) was 0.37, and several organs showed deviations close to or exceeding 0.2. CONCLUSIONS Pitch exerts the greatest influence on the stability of VMI CT numbers, whereas tube voltage and IQ level have relatively minor effects. VMI at medium-to-high energy levels (≥70 keV) exhibit relative stability across different parameters and are recommended as the first choice for quantitative analysis. Zeff measurements remain highly stable under various acquisition conditions, supporting their reliability in quantitative PCCT applications.