Virtual Monoenergetic Images Research Articles

Spectral metal artifact reduction after posterior spinal fixation in photon-counting detector CT datasets

PurposeTo investigate the usefulness of virtual monoenergetic image (VMI) reconstructions derived from scans on a novel photon-counting detector CT (PCD-CT) for artifact reduction in patients after posterior spinal fixation. MethodsThis retrospective cohort study included 23 patients status post posterior spinal fixation. Subjects were scanned on a novel PCD-CT (NAEOTOM Alpha, Siemens Healthineers, Erlangen, Germany) as part of routine clinical care. 14 sets of VMI reconstructions were derived in 10 keV increments for the interval 60–190 keV. The mean and the standard deviation (SD) of CT-values in 12 defined locations around a pair of pedicle screws on one vertebral level and the SD of homogenous fat were measured and used to calculate an artifact index (AIx). ResultsAveraged over all regions, the lowest AIx was observed at VMI levels of 110 keV (32.5 (27.8–37.9)) which was significantly different from those of VMIs ≤ 90 keV (p < 0.001) or ≥160 keV (p < 0.015), respectively. Overall AIx values increased in both lower- and higher-keV levels. Regarding individual locations, either a monotonous AIx-decrease for increasing keV values or an AIx-minimum in intermediate-keV levels (100–140 keV) was found. In locations adjacent to larger metal parts, the increase of AIx values at the high-end of the keV spectrum was mainly explained by a reappearance of streak artifacts. ConclusionOur findings suggest that 110 keV is the optimal VMI setting for overall artifact suppression. In specific anatomical regions, however, slight adjustments towards higher-keV levels may provide better results.

Changes in coronary plaque component volumes comparing different virtual monoenergetic images using photon-counting computed tomography

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): BV was supported by the ÚNKP-22-3-II-SE New National Excellence Program of the Ministry for Culture and Innovation from the source of the National Research, Development and Innovation Fund. Introduction Photon-counting CT (PCCT) allows virtual monoenergetic images (VMIs) which may aid more precise assessment of coronary plaques. We aimed to analyze how plaque component volumes change on different VMIs. Methods Coronary CT angiography images were acquired using a dual-source PCCT and VMIs were reconstructed between 40–180 keV in 10 keV increments. Polychromatic images at 120 kVp (T3D) were also reconstructed and used as reference. Quantitative image quality analysis was performed on all reconstructed images. Quantitative plaque assessment was performed on T3D images and segmentation masks were copied to all VMI images. Calcified plaque (CP; &amp;gt;350 Hounsfield units, HU), non-calcified plaque (NCP; 30–350HU) and low-attenuation NCP (LAP; −100-30HU) volumes were calculated. Results We analyzed 51 plaques from 51 patients (67% male, mean age 65±12 years). Average attenuation and contrast-to-noise ratio (CNR) decreased significantly with increasing keV levels, with similar values observed between T3D and 70 keV images (299±209 vs 303±225 HU, p = 0.15 for mean HU; 15.5±3.7 vs. 15.8±3.5, p = 0.32 for CNR). Mean NCP volume was comparable between T3D and 100–180 keV reconstructions. There was a graded decrease in mean CP volume, with a significant difference between all VMI images and T3D (p&amp;lt;0.05). LAP volume increased with increasing VMI energy levels and all VMI images showed a significant difference compared to T3D, except for 50 keV (28.0±30.8 mm3 and 28.6±30.1 mm3, respectively, p = 0.63). Conclusion Fixed threshold settings result in significantly different plaque volumes when using VMIs as compared to T3D images. Normalization protocols are needed to have comparable results between future studies.

Establishing a quality assurance program for photon counting detector (PCD) CT: Tips and caveats.

To determine the suitability of a quality assurance (QA) program based on the American College of Radiology's (ACR) CT quality control (QC) manual to fully evaluate the unique capabilities of a clinical photon-counting-detector (PCD) CT system. A daily QA program was established to evaluate CT number accuracy and artifacts for both standard and ultra-high-resolution (UHR) scan modes. A complete system performance evaluation was conducted in accordance with the ACR CT QC manual by scanning the CT Accreditation Phantom with routine clinical protocols and reconstructing low-energy-threshold (T3D) and virtual monoenergetic images (VMIs) between 40 and 120keV. Spatial resolution was evaluated by computing the modulation transfer function (MTF) for the UHR mode, and multi-energy performance was evaluated by scanning a body phantom containing four iodine inserts with concentrations between 2 and 15mg I/cc. The daily QA program identified instances when the detector needed recalibration or replacement. CT number accuracy was impacted by image type: CT numbers at 70keV VMI were within the acceptable range (defined for 120kV). Other keV VMIs and the T3D reconstruction had at least one insert with CT number outside the acceptable range. The limiting resolution was nearly 40 lp/cm based on MTF measurements, which far exceeds the 12 lp/cm maximum capability of the ACR phantom. The CT numbers in the iodine inserts were accurate on all VMIs (3.8% average percentage error), while the iodine concentrations had an average root mean squared error of 0.3mg I/cc. Protocols and parameters must be properly selected on PCD-CT to meet current accreditation requirements with the ACR CT phantom. Use of the 70keV VMI allowed passing all tests prescribed in the ACR CT manual. Additional evaluations such an MTF measurement and multi-energy phantom scans are also recommended to comprehensively evaluate PCD-CT scanner performance.

Dual-Energy CT in Cardiothoracic Imaging: Current Developments.

This article describes the technical principles and clinical applications of dual-energy computed tomography (DECT) in the context of cardiothoracic imaging with a focus on current developments and techniques. Since the introduction of DECT, different vendors developed distinct hard and software approaches for generating multi-energy datasets and multiple DECT applications that were developed and clinically investigated for different fields of interest. Benefits for various clinical settings, such as oncology, trauma and emergency radiology, as well as musculoskeletal and cardiovascular imaging, were recently reported in the literature. State-of-the-art applications, such as virtual monoenergetic imaging (VMI), material decomposition, perfused blood volume imaging, virtual non-contrast imaging (VNC), plaque removal, and virtual non-calcium (VNCa) imaging, can significantly improve cardiothoracic CT image workflows and have a high potential for improvement of diagnostic accuracy and patient safety.

Photon-counting CT for diagnosis of acute pulmonary embolism: potential for contrast medium and radiation dose reduction

ObjectiveTo evaluate the image quality of an ultra-low contrast medium and radiation dose CT pulmonary angiography (CTPA) protocol for the diagnosis of acute pulmonary embolism using a clinical photon-counting detector (PCD) CT system and compare its performance to a dual-energy-(DE)-CTPA protocol on a conventional energy-integrating detector (EID) CT system.MethodsSixty-four patients either underwent CTPA with the novel scan protocol on the PCD-CT scanner (32 patients, 25 mL, CTDIvol 2.5 mGy·cm) or conventional DE-CTPA on a third-generation dual-source EID-CT (32 patients, 50 mL, CTDIvol 5.1 mGy·cm). Pulmonary artery CT attenuation, signal-to-noise ratio, and contrast-to-noise-ratio were assessed as objective criteria of image quality, while subjective ratings of four radiologists were compared at 60 keV using virtual monoenergetic imaging and polychromatic standard reconstructions. Interrater reliability was determined by means of the intraclass correlation coefficient (ICC). Effective dose was compared between patient cohorts.ResultsSubjective image quality was deemed superior by all four reviewers for 60-keV PCD scans (excellent or good ratings in 93.8% of PCD vs. 84.4% of 60 keV EID scans, ICC = 0.72). No examinations on either system were considered “non-diagnostic.” Objective image quality parameters were significantly higher in the EID group (mostly p < 0.001), both in the polychromatic reconstructions and at 60 keV. The ED (1.4 vs. 3.3 mSv) was significantly lower in the PCD cohort (p < 0.001).ConclusionsPCD-CTPA allows for considerable reduction of contrast medium and radiation dose in the diagnosis of acute pulmonary embolism, while maintaining good to excellent image quality compared to conventional EID-CTPA.Clinical relevance statementClinical PCD-CT allows for spectral assessment of pulmonary vasculature with high scan speed, which is beneficial in patients with suspected pulmonary embolism, frequently presenting with dyspnea. Simultaneously PCD-CT enables substantial reduction of contrast medium and radiation dose.Key Points• The clinical photon-counting detector CT scanner used in this study allows for high-pitch multi-energy acquisitions.• Photon-counting computed tomography allows for considerable reduction of contrast medium and radiation dose in the diagnosis of acute pulmonary embolism.• Subjective image quality was rated best for 60-keV photon-counting scans.

Virtual monoenergetic dual-layer dual-energy CT images in colorectal cancer: CT diagnosis could be improved?

To compare conventional CT images and virtual monoenergetic images (VMI) at dual-layer dual-energy CT (dlDECT) in patients with colorectal cancer (CRC) through quantitative analysis and to investigate the added value of VMI. Sixty-six consecutive patients with histologically documented CRC and available VMI reconstructions were retrospectively investigated. Subsequently, forty-two patients, without any colonic disease at colonoscopy, were selected as control group. Conventional CT images and VMI reconstructions at energy levels ranging from 40 (VMI40) to 100keV (VMI100) in 10keV increments, were obtained from the late arterial phase. First, signal-to-noise (SNR) and contrast-to-noise (CNR) ratios were obtained to select the best VMI reconstruction. Finally, the diagnostic accuracy of conventional CT and VMI40 in late arterial phase was evaluated. On quantitative analysis, SNR and CNR were higher for VMI40 (19.5 ± 7.7 and 11.8 ± 6.2, respectively) with statistically significant differences compared to conventional CT (P < 0.05) and all the other VMI reconstructions (P < 0.05), except for VMI50 (P > 0.05). The addition of VMI40 to conventional CT images significantly improved the area under the curve (AUC) for the diagnosis of CRC, increasing it from 0.875 to 0.943 for reader 1 (P < 0.05) and from 0.916 to 0.954 for reader 2 (P < 0.05). The improvement was greater in the less experienced radiologist (0.068) compared to the more experienced one (0.037). VMI40 has showed the highest quantitative image parameters. Furthermore, the use of VMI40 can lead to a significant improvement in the diagnostic performance for detecting CRC.

Investigation on the proton range uncertainty with spectral CT-based virtual monoenergetic images.

The stopping power ratio (SPR) prediction error will contribute to the range uncertainty of proton therapy. Spectral CT is promising in reducing the uncertainty in SPR estimation. The purpose of this research is to determine the optimal energy pairs of SPR prediction for each tissue and to evaluate the dose distribution and range difference between the spectral CT with the optimal energy pairs method and the single energy CT (SECT) method. A new method was proposed based on image segmentation to calculate the proton dose with spectral CT images for the head and body phantom. CT number of each organ region were converted to SPR with the optimal energy pairs of each organ. The CT images were segmented into different organ parts with thresholding method. Virtual monoenergetic (VM) images from 70keV to 140keV were investigated to determine the optimal energy pairs for each organ based on Gammex 1467 phantom. The beam data of Shanghai Advanced Proton Therapy facility (SAPT) was employed in matRad (an open-source software for radiation treatment planning) for the dose calculation. The optimal energy pairs were obtained for each tissue. The dose distribution of two tumor sites (brain and lung) were calculated with the aforementioned optimal energy pairs. The maximum dose deviation between spectral CT and SECT at the target region was 2.57% and 0.84% for the lung tumor and brain tumor respectively. The range difference between spectral and SECT was significant with 1.8411mm for the lung tumor. γ passing rate was 85.95% and 95.49% for the lung tumor and brain tumor with the criterion 2%/2mm. This work presents a way to determine the optimal energy pairs for each organ and to calculate the dose distribution based on the more accurate SPR prediction.

Combining virtual monoenergetic imaging and iterative metal artifact reduction in first-generation photon-counting computed tomography of patients with dental implants

ObjectivesWhile established for energy-integrating detector computed tomography (CT), the effect of virtual monoenergetic imaging (VMI) and iterative metal artifact reduction (iMAR) in photon-counting detector (PCD) CT lacks thorough investigation. This study evaluates VMI, iMAR, and combinations thereof in PCD-CT of patients with dental implants.Material and methodsIn 50 patients (25 women; mean age 62.0 ± 9.9 years), polychromatic 120 kVp imaging (T3D), VMI, T3DiMAR, and VMIiMAR were compared. VMIs were reconstructed at 40, 70, 110, 150, and 190 keV. Artifact reduction was assessed by attenuation and noise measurements in the most hyper- and hypodense artifacts, as well as in artifact-impaired soft tissue of the mouth floor. Three readers subjectively evaluated artifact extent and soft tissue interpretability. Furthermore, new artifacts through overcorrection were assessed.ResultsiMAR reduced hyper-/hypodense artifacts (T3D 1305.0/−1418.4 versus T3DiMAR 103.2/−46.9 HU), soft tissue impairment (106.7 versus 39.7 HU), and image noise (16.9 versus 5.2 HU) compared to non-iMAR datasets (p ≤ 0.001). VMIiMAR ≥ 110 keV subjectively enhanced artifact reduction over T3DiMAR (p ≤ 0.023). Without iMAR, VMI displayed no measurable artifact reduction (p ≥ 0.186) and facilitated no significant denoising over T3D (p ≥ 0.366). However, VMI ≥ 110 keV reduced soft tissue impairment (p ≤ 0.009). VMIiMAR ≥ 110 keV resulted in less overcorrection than T3DiMAR (p ≤ 0.001). Inter-reader reliability was moderate/good for hyperdense (0.707), hypodense (0.802), and soft tissue artifacts (0.804).ConclusionWhile VMI alone holds minimal metal artifact reduction potential, iMAR post-processing enabled substantial reduction of hyperdense and hypodense artifacts. The combination of VMI ≥ 110 keV and iMAR resulted in the least extensive metal artifacts.Clinical relevanceCombining iMAR with VMI represents a potent tool for maxillofacial PCD-CT with dental implants achieving substantial artifact reduction and high image quality.Key Points• Post-processing of photon-counting CT scans with an iterative metal artifact reduction algorithm substantially reduces hyperdense and hypodense artifacts arising from dental implants.• Virtual monoenergetic images presented only minimal metal artifact reduction potential.• The combination of both provided a considerable benefit in subjective analysis compared to iterative metal artifact reduction alone.

Combining iterative metal artifact reduction and virtual monoenergetic images severely reduces hip prosthesis-associated artifacts in photon-counting detector CT

Aim of this study was to assess the impact of virtual monoenergetic images (VMI) in combination and comparison with iterative metal artifact reduction (IMAR) on hip prosthesis-associated artifacts in photon-counting detector CT (PCD-CT). Retrospectively, 33 scans with hip prosthesis-associated artifacts acquired during clinical routine on a PCD-CT between 08/2022 and 09/2022 were analyzed. VMI were reconstructed for 100–190 keV with and without IMAR, and compared to polychromatic images. Qualitatively, artifact extent and assessment of adjacent soft tissue were rated by two radiologists using 5-point Likert items. Quantitative assessment was performed measuring attenuation and standard deviation in most pronounced hypodense and hyperdense artifacts, artifact-impaired bone, muscle, vessels, bladder and artifact-free corresponding tissue. To quantify artifacts, an adjusted attenuation was calculated as the difference between artifact-impaired tissue and corresponding tissue without artifacts. Qualitative assessment improved for all investigated image reconstructions compared to polychromatic images (PI). VMI100keV in combination with IMAR achieved best results (e.g. diagnostic quality of the bladder: median PI: 1.5 (range 1–4); VMI100keV+IMAR: 5 (3–5); p < 0.0001). In quantitative assessment VMI100keV with IMAR provided best artifact reduction with an adjusted attenuation closest to 0 (e.g. bone: PI: 302.78; VMI100keV+IMAR: 51.18; p < 0.0001). The combination of VMI and IMAR significantly reduces hip prosthesis-associated artifacts in PCD-CT and improves the diagnostic quality of surrounding tissue.

Exploring Dual-Energy CT Spectral Information for Machine Learning-Driven Lesion Diagnosis in Pre-Log Domain.

In this study, we proposed a computer-aided diagnosis (CADx) framework under dual-energy spectral CT (DECT), which operates directly on the transmission data in the pre-log domain, called CADxDE, to explore the spectral information for lesion diagnosis. The CADxDE includes material identification and machine learning (ML) based CADx. Benefits from DECT's capability of performing virtual monoenergetic imaging with the identified materials, the responses of different tissue types (e.g., muscle, water, and fat) in lesions at each energy can be explored by ML for CADx. Without losing essential factors in the DECT scan, a pre-log domain model-based iterative reconstruction is adopted to obtain decomposed material images, which are then used to generate the virtual monoenergetic images (VMIs) at selected n energies. While these VMIs have the same anatomy, their contrast distribution patterns contain rich information along with the n energies for tissue characterization. Thus, a corresponding ML-based CADx is developed to exploit the energy-enhanced tissue features for differentiating malignant from benign lesions. Specifically, an original image-driven multi-channel three-dimensional convolutional neural network (CNN) and extracted lesion feature-based ML CADx methods are developed to show the feasibility of CADxDE. Results from three pathologically proven clinical datasets showed 4.01% to 14.25% higher AUC (area under the receiver operating characteristic curve) scores than the scores of both the conventional DECT data (high and low energy spectrum separately) and the conventional CT data. The mean gain >9.13% in AUC scores indicated that the energy spectral-enhanced tissue features from CADxDE have great potential to improve lesion diagnosis performance.

Impact of an advanced image based monoenergetic reconstruction algorithm on coronary artery stent visualization by dual source dual energy computed tomography: A primary study

ABSTRACT Background: The aim of this study was to investigate the qualities of advanced image based virtual monoenergetic (Mono+) images using a noise optimized algorithm at different kiloelectron volts (keV) compared with linear blended 120 kilovoltage (kV) images in patients with coronary stents. Materials and Methods: Thirty two patients who had undergone coronary computed tomography angiography were retrospectively enrolled in the study. Linear blended 120 kV image and 16 Mono+ images were reconstructed. Quantitative assessments included luminal attenuation difference, in stent image noise, in stent signal to noise ratio (SNR) and contrast to noise ratio (CNR). Double blinded and independent qualitative evaluation of image quality was performed by two readers using a five point scale. Results: The luminal attenuation difference value in the 190 keV group was the lowest. The in stent image noise in the 190 keV group was the lowest, in comparison with that in the 90–180 keV groups; however, it showed no significant difference. The 40 keV group had the highest in stent SNR, and there were no differences between the 40 keV group and the 50–100 keV groups. The 60 keV group had the highest in stent CNR, although no significant difference was found between the 60 keV group and the 40–120 keV groups. The highest subjective score was observed in the 80 keV group, with significant differences from the other groups (P &lt; 0.05), except for the 90 keV group. Conclusion: In comparison with computed tomography image with conventional reconstruction, Mono+ reconstructions at 90 keV can significantly reduce the in stent noise and provide better image quality of coronary stents.

Dual-Energy CT Evaluation of Gastrointestinal Bleeding

Gastrointestinal (GI) bleeding is a potentially life-threatening condition accounting for more than 300 000 annual hospitalizations. Multidetector abdominopelvic CT angiography is commonly used in the evaluation of patients with GI bleeding. Given that many patients with severe overt GI bleeding are unlikely to tolerate bowel preparation, and inpatient colonoscopy is frequently limited by suboptimal preparation obscuring mucosal visibility, CT angiography is recommended as a first-line diagnostic test in patients with severe hematochezia to localize a source of bleeding. Assessment of these patients with conventional single-energy CT systems typically requires the performance of a noncontrast series followed by imaging during multiple postcontrast phases. Dual-energy CT (DECT) offers several potential advantages for performing these examinations. DECT may eliminate the need for a noncontrast acquisition by allowing the creation of virtual noncontrast (VNC) images from contrast-enhanced data, affording significant radiation dose reduction while maintaining diagnostic accuracy. VNC images can help radiologists to differentiate active bleeding, hyperattenuating enteric contents, hematomas, and enhancing masses. Additional postprocessing techniques such as low-kiloelectron voltage virtual monoenergetic images, iodine maps, and iodine overlay images can increase the conspicuity of contrast material extravasation and improve the visibility of subtle causes of GI bleeding, thereby increasing diagnostic confidence and assisting with problem solving. GI bleeding can also be diagnosed with routine single-phase DECT scans by constructing VNC images and iodine maps. Radiologists should also be aware of the potential pitfalls and limitations of DECT. ©RSNA, 2023 Quiz questions for this article are available through the Online Learning Center.

Virtual Monoenergetic Imaging of Lower Extremities Using Dual-Energy CT Angiography in Patients with Diabetes Mellitus.

Type 2 diabetes mellitus (DM) is the most common metabolic disorder in the world and an important risk factor for peripheral arterial disease (PAD). CT angiography represents the method of choice for the diagnosis, pre-operative planning, and follow-up of vascular disease. Low-energy dual-energy CT (DECT) virtual mono-energetic imaging (VMI) has been shown to improve image contrast, iodine signal, and may also lead to a reduction in contrast medium dose. In recent years, VMI has been improved with the use of a new algorithm called VMI+, able to obtain the best image contrast with the least possible image noise in low-keV reconstructions. To evaluate the impact of VMI+ DECT reconstructions on quantitative and qualitative image quality in the evaluation of the lower extremity runoff. We evaluated DECT angiography of lower extremities in patients suffering from diabetes who had undergone clinically indicated DECT examinations between January 2018 and January 2023. Images were reconstructed with standard linear blending (F_0.5) and low VMI+ series were generated from 40 to 100 keV, in an interval of 15 keV. Vascular attenuation, image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were calculated for objective analysis. Subjective analysis was performed using five-point scales to evaluate image quality, image noise, and diagnostic assessability of vessel contrast. Our final study cohort consisted of 77 patients (41 males). Attenuation values, CNR, and SNR were higher in 40-keV VMI+ reconstructions compared to the remaining VMI+ and standard F_0.5 series (HU: 1180.41 ± 45.09; SNR: 29.91 ± 0.99; CNR: 28.60 ± 1.03 vs. HU 251.32 ± 7.13; SNR: 13.22 ± 0.44; CNR: 10.57 ± 0.39 in standard F_0.5 series) (p < 0.0001). Subjective image rating was significantly higher in 55-keV VMI+ images compared to the other VMI+ and standard F_0.5 series in terms of image quality (mean score: 4.77), image noise (mean score: 4.39), and assessability of vessel contrast (mean value: 4.57) (p < 0.001). DECT 40-keV and 55-keV VMI+ showed the highest objective and subjective parameters of image quality, respectively. These specific energy levels for VMI+ reconstructions could be recommended in clinical practice, providing high-quality images with greater diagnostic suitability for the evaluation of lower extremity runoff, and potentially needing a lower amount of contrast medium, which is particularly advantageous for diabetic patients.

Principles and Applications of Dual-Layer Spectral CT in Gastrointestinal Imaging.

The advance in technology allows for the development of different CT scanners in the field of dual-energy computed tomography (DECT). In particular, a recently developed detector-based technology can collect data from different energy levels, thanks to its layers. The use of this system is suited for material decomposition with perfect spatial and temporal registration. Thanks to post-processing techniques, these scanners can generate conventional, material decomposition (including virtual non-contrast (VNC), iodine maps, Z-effective imaging, and uric acid pair images) and virtual monoenergetic images (VMIs). In recent years, different studies have been published regarding the use of DECT in clinical practice. On these bases, considering that different papers have been published using the DECT technology, a review regarding its clinical application can be useful. We focused on the usefulness of DECT technology in gastrointestinal imaging, where DECT plays an important role.

Robustness of radiomics features of virtual unenhanced and virtual monoenergetic images in dual-energy CT among different imaging platforms and potential role of CT number variability

ObjectivesTo evaluate robustness of dual-energy CT (DECT) radiomics features of virtual unenhanced (VUE) image and virtual monoenergetic image (VMI) among different imaging platforms.MethodsA phantom with sixteen clinical-relevant densities was scanned on ten DECT platforms with comparable scan parameters. Ninety-four radiomic features were extracted via Pyradiomics from VUE images and VMIs at energy level of 70 keV (VMI70keV). Test–retest repeatability was assessed by Bland–Altman analysis. Inter-platform reproducibility of VUE images and VMI70keV was evaluated by coefficient of variation (CV) and quartile coefficient of dispersion (QCD) among platforms, and by intraclass correlation coefficient (ICC) and concordance correlation coefficient (CCC) between platform pairs. The correlation between variability of CT number radiomics reproducibility was estimated.Results92.02% and 92.87% of features were repeatable between scan–rescans for VUE images and VMI70keV, respectively. Among platforms, 11.30% and 28.39% features of VUE images, and 15.16% and 28.99% features of VMI70keV were with CV < 10% and QCD < 10%. The average percentages of radiomics features with ICC > 0.90 and CCC > 0.90 between platform pairs were 10.00% and 9.86% in VUE images and 11.23% and 11.23% in VMI70keV. The CT number inter-platform reproducibility using CV and QCD showed negative correlations with percentage of the first-order radiomics features with CV < 10% and QCD < 10%, in both VUE images and VMI70keV (r2 0.3870–0.6178, all p < 0.001).ConclusionsThe majority of DECT radiomics features were non-reproducible. The differences in CT number were considered as an indicator of inter-platform DECT radiomics variation.Critical relevance statement: The majority of radiomics features extracted from the VUE images and the VMI70keV were non-reproducible among platforms, while synchronizing energy levels of VMI to reduce the CT number value variability may be a potential way to mitigate radiomics instability.Graphical

Dual-layer spectral CT improves the image quality of cerebral unenhanced CT scan in children

PurposeTo evaluate the image quality and determine the optimal energies of virtual monoenergetic imaging (VMI) in unenhanced pediatric cerebral scans by dual-layer spectral detector computed tomography (DLCT). MethodsFifty-three consecutive unenhanced cerebral scans by a DLCT scanner in children (age ≤ 12 years) were retrospectively analyzed. Conventional images (CI) and VMIs were reconstructed. The gray matter (GM) and white matter (WM) noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), posterior fossa, and subcalvarial artifac tindex (PFAI, SAI) were calculated. Two radiologists independently determined the image quality using a 5-point Likert-type scale based on GM − WM differentiation (GWMA), subcalvarialspace (SAA), beam hardening artifacts in the posterior fossa (PFAA), and the overall diagnostic quality. The student t-test and Wilcoxon test were used to determining the statistical significance. ResultsCompared with CI, superior noise were observed in VMI at low keV levels and were lowest at 100 keV (P < 0.001); the SNR and CNR were significantly higher at the 45 keV to 75 keV levels (all Ps of <0.005). The best GWMA were noticed at the 50 keV level compared to other keV levels (all P < 0.05). The optimal SAA and PFAA were found at 100 keV, respectively. The assessment of overall diagnostic quality was the best at 50 keV (P < 0.013 to < 0.001). ConclusionsThe VMI scan significantly improved the quality of pediatric cerebral images compared with those from CI. The optimal energy level for the brainparenchyma was 50 keV while those for subcalvarial space and posterior fossa were 100 keV.

Pseudoenhancement in Cystic Renal Lesions – Impact of Virtual Monoenergetic Images of Photon-Counting Detector CT on Lesion Classification

To investigate the impact of virtual monoenergetic images (VMI) from photon-counting detector CT (PCD-CT) on the enhancement and classification of renal cysts. Adults with renal cysts (≥7mm) who received a triphasic examination on a clinical PCD-CT (120kVp; IQ level 68) between July 2021 and March 2022 were retrospectively identified. Only non-enhancing cysts (enhancement<10HU between unenhanced and venous phase at 70keV) were included. VMI from 40 to 190keV with increments of 10keV were reconstructed from the venous phase. Enhancement was measured to classify each lesion as non-enhancing (<10HU), equivocally enhancing (10-19HU), and definitely enhancing (≥20HU). Classification changes as a function of VMI were assessed. Pearson correlation coefficient, the Kruskal-Wallis and the Chi-square test were used. A total of 86patients (mean age, 74±9 years; 74 male) with 160 non-enhancing renal cysts (17.6±10mm) were included. CT attenuation of the cysts increased from higher to lower VMI levels with a mean attenuation of 4±11HU at 190keV to 36±17HU at 40keV. Mean attenuation of the renal parenchyma was 43±4HU at 190keV and 414±71HU at 40keV. No cyst exhibited enhancement from 70keV to 190keV. At 40, 50, and 60keV, 35% (56/160), 29% (47/160) and 9% (15/160) of cysts showed equivocal and 46% (74/160), 10% (16/160), and 0% (0/160) definite enhancement, respectively. There was no significant influence of size (P=.13), cyst location (P=.9) and BMI (P=.19) on enhancement classification. VMI has a relevant impact on enhancement and classification of renal cysts with misclassification in a large number of cases at energy levels below 70keV.

Improving visualization of free fibula flap perforators and reducing radiation dose in dual-energy CT angiography.

The precise assessment of the perforators of the fibula free flap (FFF) is crucial for minimizing procedure-related complications when harvesting the FFF in patients with maxillofacial lesions. This study aims to investigate the utility of virtual noncontrast (VNC) images for radiation dose saving and to determine the optimal energy level of virtual monoenergetic imaging (VMI) reconstructions in dual-energy computed tomography (DECT) for visualization of the perforators of the fibula free flap (FFF). Data from 40 patients with maxillofacial lesions who received lower extremity DECT examinations in the noncontrast and arterial phase were collected in this retrospective, cross-sectional study. To compare VNC images from the arterial phase with true non-contrast images in a DECT protocol (M_0.5-TNC) and to compare VMI images with 0.5 linear images blending from the arterial phase (M_0.5-C), the attenuation, noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and subjective image quality were assessed in different arteries, muscles, and fat tissues. Two readers evaluated the image quality and visualization of the perforators. The dose-length product (DLP) and CT volume dose index (CTDIvol) were used to determine the radiation dose. Objective and subjective analyses showed no significant difference between the M_0.5-TNC and VNC images in the arteries and muscles (P>0.09 to P>0.99), and VNC imaging could reduce 50% of the radiation dose (P<0.001). Compared with those of the M_0.5-C images, the attenuation and CNR of VMI reconstructions at 40 kiloelectron volt (keV) and 60 keV were higher (P<0.001 to P=0.04). Noise was similar at 60 keV (all P>0.99) and increased at 40 keV (all P<0.001), and the SNR in arteries was increased at 60 keV (P<0.001 to P=0.02) in VMI reconstructions compared with those in the M_0.5-C images. The subjective scores in VMI reconstructions at 40 and 60 keV was higher than those in M_0.5-C images (all P<0.001). The image quality at 60 keV was superior to that at 40 keV (P<0.001), and there was no difference in the visualization of the perforators between 40 and 60 keV (P=0.31). VNC imaging is a reliable technique for replacing M_0.5-TNC and provides radiation dose saving. The image quality of the 40-keV and 60-keV VMI reconstructions was higher than that of the M_0.5-C images, and 60 keV provided the best assessment of perforators in the tibia.

Predicting coronary atherosclerosis heart disease with pericoronary adipose tissue attenuation parameters based on dual-layer spectral detector computed tomography: a preliminary exploration.

Coronary atherosclerosis is a chronic inflammatory condition. Pericoronary adipose tissue (PCAT) attenuation is closely related to coronary inflammation. This study aimed to investigate the relationship between PCAT attenuation parameters and coronary atherosclerotic heart disease (CAD) using dual-layer spectral detector computed tomography (SDCT). This cross-sectional study included eligible patients who underwent coronary computed tomography angiography using SDCT at the First Affiliated Hospital of Harbin Medical University between April 2021 and September 2021. Patients were classified as CAD (with coronary artery atherosclerotic plaque) or non-CAD (without coronary artery atherosclerotic plaque). Propensity score matching was used to match the two groups. The fat attenuation index (FAI) was used to quantify PCAT attenuation. The FAI was measured on conventional images (120 kVp) and virtual monoenergetic images (VMI) by semiautomatic software. The slope of the spectral attenuation curve (λ) was calculated. Regression models were established to evaluate the predictive value of PCAT attenuation parameters for CAD. A total of 45 patients with CAD and 45 patients without CAD were enrolled. The PCAT attenuation parameters in the CAD group were significantly higher than those in the non-CAD group (all P values <0.05). The PCAT attenuation parameters of vessels with or without plaques in the CAD group were higher than those of vessels without plaques in the non-CAD group (all P values <0.05). In the CAD group, the PCAT attenuation parameters of vessels with plaques were slightly higher than those of vessels without plaques (all P values >0.05). In receiver operating characteristic curve analysis, the FAIVMI model achieved an area under the curve (AUC) of 0.8123 for discriminating between patients with and without CAD, which was higher than those of the FAI120 kVp model (AUC =0.7444) and the λ model (AUC =0.7230). However, the combined model of FAIVMI, FAI120 kVp, and λ obtained the best performance (AUC =0.8296) of all the models. PCAT attenuation parameters obtained using dual-layer SDCT can aid in distinguishing patients with and without CAD. By detecting increases in PCAT attenuation parameters, it might be possible to predict the formation of atherosclerotic plaques before they appear.

The first mobile photon-counting detector CT: the human images and technical performance study

Objective. The purpose of this study is to assess its human images and its unique capabilities such as the ‘on demand’ higher spatial resolution and multi-spectral imaging of photon-counting-detector (PCD)-CT. Approach. In this study, the FDA 510(k) cleared mobile PCD-CT (OmniTom Elite) was used. To this end, we imaged internationally certified CT phantoms and a human cadaver head to evaluate the feasibility of high resolution (HR) and multi-energy imaging. We also demonstrate the performance of PCD-CT via first-in-human imaging by scanning three human volunteers. Main results. At the 5 mm slice thickness, routinely used in diagnostic head CT, the first human PCD-CT images were diagnostically equivalent to the EID-CT scanner. The HR acquisition mode of PCD-CT achieved a resolution of 11 line-pairs (lp)/cm as compared to 7 lp cm−1 using the same kernel (posterior fossa-kernel) in the standard acquisition mode of EID-CT. For the quantitative multi-energy CT performance, the measured CT numbers in virtual mono-energetic images (VMI) of iodine inserts in the Gammex Multi-Energy CT phantom (model 1492, Sun Nuclear Corporation, USA) matched the manufacturer reference values with mean percent error of 3.25%. Multi-energy decomposition with PCD-CT demonstrated the separation and quantification of iodine, calcium, and water. Significance. PCD-CT can achieve multi-resolution acquisition modes without physically changing the CT detector. It can provide superior spatial resolution compared with the standard acquisition mode the conventional mobile EID-CT. Quantitative spectral capability of PCD-CT can provide accurate, simultaneous multi-energy images for material decomposition and VMI generation using a single exposure.