Contrast-to-noise Ratio Research Articles

Positron Range Correction Helps Enhance the Image Quality of Cardiac 82Rb PET/CT.

The image quality and quantitative accuracy of 82Rb myocardial perfusion imaging (MPI) using PET is challenged by the extensive positron range (PR) effects, with the PR of 82Rb being about 7 mm in soft tissues. This study explored the feasibility of applying postacquisition PR correction (PRC) to routine 82Rb PET/CT MPI acquisitions and assessed its impact on diagnostic accuracy and image quality. Methods: We implemented a PRC method adjusted to 82Rb into a vendor-provided reconstruction toolbox, using tissue-specific corrections for soft tissue, bone, and air/lungs. The PRC was evaluated in 2 cohorts: the first comprised 25 healthy volunteers who underwent repeated 82Rb MPI within 2 wk, and the second included 66 patients with known or suspected coronary artery disease. We measured the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) for the volunteer cohort. In the patient cohort, the impact of PRC was evaluated as changes in the area under the receiver operating characteristic curve (AUC), using fractional flow reserve as the gold standard (values < 80% were considered significantly reduced). We calculated AUCs for stress and ischemic total perfusion deficits. Results: In the volunteer cohort, PRC-based reconstructions (standard reconstruction [STD] + PRC) demonstrated significantly improved SNR and CNR compared with STD, with median increases of 22% and 47% for SNR and CNR, respectively (P < 0.05). For the patient cohort, comparable AUCs were reported for STD- versus PRC-based reconstructions (stress total perfusion deficits, 0.84 vs. 0.83 [P = 0.49]; ischemic total perfusion deficits, 0.87 vs. 0.87 [P = 0.80]). Conclusion: PRC significantly enhances SNR and CNR compared with STD without affecting the diagnostic accuracy of the scans. Given the significantly improved image quality, PRC may be recommended for MPI using 82Rb PET/CT clinical-routine-assessment interpretation of TPD.

Effect of OSEM Reconstruction Iteration Number and Monte Carlo Collimator Modeling on 166Ho Activity Quantification in SPECT/CT

Background: Accurate reconstruction and quantification in the post-therapy SPECT/CT imaging of 166Ho microspheres for hepatic malignancies is crucial for treatment evaluation. This present study aimed to explore the impact of the OSEM reconstruction parameters on SPECT/CT image features for dose distribution determination, using Hybrid Recon™ (Hermes Medical Solutions AB) and full Monte Carlo (MC) collimator modeling. Methods: Image quality and activity quantification were assessed through two acquisitions of the Jaszczak phantom using a Siemens Symbia Intevo Bold SPECT/CT system. The datasets were reconstructed using the OSEM method, with variations in the number of iterations for 15 and 8 subsets, both with and without full MC collimator modeling. Contrast recovery coefficient (QH), coefficient of variation (CV), contrast-to-noise ratio (CNR), calibration factor (CF), and activity recovery coefficient (ARC) were calculated and used to evaluate image quality and activity quantification. Results: Reconstructions with 5 iterations and 15 subsets, as well as 10 iterations and 8 subsets, were selected as the most suitable for 166Ho imaging, as they provided higher QH and ARCs. Incorporating full MC collimator modeling in both reconstructions led to significant improvements in image quality and activity recovery. The CFs remained consistent for a fixed value of 15 and 8 subsets, with values of (14.9 ± 0.5) cps/MBq and (14.6 ± 0.5) cps/MBq, respectively. However, when applying full collimator modeling, the CF values decreased to a range between 10.9 and 12.1 cps/MBq. Conclusions: For 166Ho SPECT/CT imaging, OSEM (with either 5 iterations and 15 subsets or 10 iterations and 8 subsets) combined with full MC collimator modeling yielded superior image quality and quantification results.

Feasibility of very low iodine dose aortoiliac CT angiography using dual-source photon-counting detector CT.

To evaluate the feasibility of aortoiliac CT-Angiography (CTA) using dual-source photon-counting detector (PCD)-CT with minimal iodine dose. This IRB-approved, single-center prospective study enrolled patients with indications for aortoiliac CTA from December 2022 to March 2023. All scans were performed using a first-generation dual-source PCD-CT. Images were acquired with fast pitch and full spectral capabilities (collimation 144×0.4mm). The contrast protocol included a mixture of sodium chloride and iodinated contrast agent (Iopromide, total iodine dose: 9.5-9.8g). Virtual monoenergetic images (VMIs) were reconstructed at 40, 50, 60, and 68keV. Two blinded radiologists evaluated image quality on a 4-point scale. Attenuation was measured across eight regions in the aorta and iliac arteries, and contrast-to-noise ratio (CNR) was calculated. Statistical comparisons were performed using repeated measures ANOVA and Bonferroni post-hoc tests. The final cohort consisted of 39 subjects (mean age: 69.6±9.6years; 30.8% female). VMI at 40keV provided significantly higher attenuation: 478±114 HU, compared to 50keV (331±74 HU), 60keV (241±51 HU), and 68keV (190±48 HU) (p<0.01). This translated in increased CNR for 40keV reconstructions (11.8±3.9), followed by 50keV (9.1±3.0), 60keV (7.0±2.3), and 68keV (6.1±1.9) (p<0.01). Subjective image quality was rated excellent at 40keV (4 [3,4]), though associated with highest noise (38±7.4 HU, p=0.02). Aortoiliac CTA using dual-source PCD-CT at 40keV achieved high attenuation and CNR, enabling effective imaging with only 9.8g of iodine.

A novel method to enhance medical image reconstruction using Genetic Algorithm and Incremental Principal Component Analysis.

Medical imaging has an crucial role in modern healthcare and helps diagnosing and treating for a variety of medical conditions. However, the quality of medical images can be affected by factors such as noise, artifacts, and limited resolution. This paper proposes a novel approach for enhancing the reconstruction of medical images by combining Genetic Algorithm (GA) with Incremental Principal Component Analysis (IPCA). The proposed method aims to improve image quality by extracting relevant features from the original image using GA, followed by reconstruction using IPCA. Through this comprehensive approach, the goal is to enhance the reconstruction of medical images and improve their diagnostic utility in clinical practice. To prove the validity of the proposed method, five different magnetic resonance (MR) images of the shoulder joints are used and the image quality are measured using the signal-to-noise ratio (SNR) terminology with peak signal-to-noise ratio (PSNR), a structural similarity index measure (SSIM) and contrast-to-noise ratio (CNR). The results demonstrate significant improvements in image quality, confirming the effectiveness of the proposed method in enhancing the reconstruction of medical images.

Comparison of Radiation Dose and Image Quality in Pediatric Abdominopelvic Photon-Counting Versus Energy-Integrating Detector CT.

Adoption of abdominal photon counting detector CT (PCD-CT) into clinical pediatric CT practice requires evidence that it provides diagnostic images at acceptable radiation doses. Thus, this study aimed to compare radiation dose and image quality of PCD-CT and conventional energy-integrating detector CT (EID-CT) in pediatric abdominopelvic CT. This institutional review board-approved retrospective study included 147 children (median age 8.5y; 80 boys, 67 girls) who underwent clinically indicated contrast-enhanced abdominopelvic PCD-CT between October 1, 2022 and April 30, 2023 and 147 children (median age 8.5y; 74 boys, 73 girls) who underwent EID-CT between July 1, 2021 and January 1, 2022. Patients in the 2 groups were matched by age and effective diameter. Radiation dose parameters (CT dose index volume, CTDIvol; dose length product, DLP; size-specific dose estimate, SSDE) were recorded. In a subset of 25 matched pairs, subjective image quality was assessed on a scale of 1 to 4 (1=highest quality), and liver attenuation, dose-normalized noise, and contrast-to-noise ratio (CNR) were measured. Groups were compared using parametric and/or nonparametric testing. Among the 147 matched pairs, there were no significant differences in sex (P=0.576), age (P=0.084), or diameter (P=0.668). PCD-CT showed significantly lower median CTDIvol, DLP, and SSDE (1.6mGy, 63.8mGy-cm, 3.1mGy) compared with EID-CT (3.7mGy, 155.3mGy-cm, 6.0mGy) (P<0.001). In the subset of 25 patients, PCD-CT and EID-CT showed no significant difference in overall image quality for reader 1 (1.0 vs. 1.0, P=0.781) or reader 2 (1.0 vs. 1.0, P=0.817), or artifacts for reader 1 (1.0 vs. 1.0, P=0.688) or reader 2 (1.0 vs. 1.0, P=0.219). After normalizing for radiation dose, image noise was significantly lower with PCD-CT (P<0.001), while CNR in the liver (P=0.244) and portal vein (P=0.079) were comparable to EID-CT. Abdominopelvic PCD-CT in children significantly reduces radiation dose while maintaining subjective image quality, and accounting for dose levels, has the potential to lower image noise and achieve comparable CNR to EID-CT. These data expand understanding of the capabilities of PCD-CT and support its routine use in children.

Development of next generation low-cost OCT towards improved point-of-care retinal imaging

Low-cost optical coherence tomography (OCT) has shown promise in increasing access to noninvasive retinal imaging at the point of care, especially in low-resource environments. A next-generation low-cost OCT system is presented which improves performance over previous versions by employing balanced detection, improved spectrometer falloff, and an increased A-line rate of 40 kHz. An algorithm is presented for image display that uses a histogram matching procedure to improve contrast-to-noise ratio (CNR). Imaging performance is benchmarked with CNR analysis of retinal OCT images, demonstrating a CNR of 2.01 ± 0.39 (p &lt; 0.0001) for macula images collected during a clinical trial, a significant improvement over previous low-cost OCT systems.

Fabrication of Glycerin-Based Chest Phantom as a Simulation Model for Paediatric Pneumonia

This study aims to fabricate a chest phantom that can replicate pneumonia cases in patients using materials that are easily found in the market. The materials used were polymethyl methacrylate (PMMA), polyurethane (PU) foam, and calcium carbonate which each replace the patient's soft tissue, lungs, and ribs, respectively. The patient's pneumonia case was replicated using glycerin fluid. The fabricated phantom was scanned using a GE Revolution EVO 128 slice CT scanner with a tube current of 100 mA and tube voltages of 80, 100, 120 and 140 kV. Image analysis was performed by comparing phantom images with patient images exposed using the same exposure factor. The parameters of CT number, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were used to compared images of the fabricated phantom and patients. The results showed that the CT numbers produced by soft tissue, bone, and normal lungs in the fabricated phantom were in the range of CT numbers of soft tissue, bone, and normal lungs in the patient image. Meanwhile, the CT number of pneumonia in the phantom (-805 HU) was still different from the CT number of pneumonia in the patient image (-57 to 49 HU). It can be concluded that the fabricated phantom has succeeded in replicating the main anatomical features of the patient (normal soft tissue, bone, and lung). However, replication of pneumonia needs to be improved so that it will be similar to the real case of pneumonia.

Development of In-house Chest Phantom for Pediatric Cancer Cases

This study aims to develop an in-house phantom that can more cheaply represent pediatric lung cancer cases. The materials used in this study were polymethyl methacrylate (PMMA) as a substitute for soft tissue, polyurethane (PU) foam as a substitute for lung tissue, and calcium carbonate as a replacement for rib bones. Cancer or nodules were represented using beeswax. The phantom evaluation was conducted using IndoQCT software, with parameters such as CT number, noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR). The CT numbers of cancer/nodule, normal lung, soft tissue, and bone for the in-house phantom are -217 to -117, -979, 80, and 871 HU, respectively. As comparison, the CT number of cancer/nodule, normal lung, soft tissue, and bone for the real patients are -141 to -103, -906, 73, and 743 HU, respectively. These findings indicate that the CT number, noise, SNR, and CNR values for the substitute materials used in the in-house phantom closely resemble the imaging values of patients with cancer/nodules. Thus, the materials used can effectively represent human tissue substitutes.

Enhancing Liver Nodule Visibility and Diagnostic Classification Using Ultrasound Local Attenuation Coefficient Slope Imaging.

B-mode ultrasound (US) presents challenges in accurately detecting and distinguishing between benign and malignant liver nodules. This study utilized quantitative US local attenuation coefficient slope (LACS) imaging to address these limitations. This is a prospective, cross-sectional study in adult patients with definable solid liver nodules at US conducted from March 2021 to December 2023. The composite reference standard included histopathology when available or magnetic resonance imaging. LACS images were obtained using a phantom-free method. Nodule visibility was assessed by computing the contrast-to-noise ratio (CNR). Classification accuracy for differentiating benign and malignant lesions was assessed with the area under the receiver operating characteristic curve (AUC), along with sensitivity and specificity. The study enrolled 97 patients (age: 62 y ± 13 [standard deviation]), with 57.0% malignant and 43.0% benign observations (size: 26.3 ± 18.9 mm). LACS images demonstrated higher CNR (12.3 dB) compared to B-mode (p < 0.0001). The AUC for differentiating nodules and liver parenchyma was 0.85 (95% confidence interval [CI]: 0.79-0.90), with higher values for malignant (0.93, CI: 0.88-0.97) than benign nodules (0.76, CI: 0.66-0.87). A LACS threshold of 0.94 dB/cm/MHz provided a sensitivity of 0.83 (CI: 0.74-0.89) and a specificity of 0.82 (CI: 0.73-0.88). LACS mean values were higher (p < 0.0001) in malignant (1.28 ± 0.27 dB/cm/MHz) than benign nodules (0.98 ± 0.19 dB/cm/MHz). LACS imaging improves nodule visibility and provides better differentiation between benign and malignant liver nodules, showing promise as a diagnostic tool.

Impact of tissue-independent positron range correction on [68Ga]Ga-DOTATOC and [68Ga]Ga-PSMA PET image reconstructions: a patient data study.

The positron range effect can impair PET image quality of Gallium-68 (68Ga). A positron range correction (PRC) can be applied to reduce this effect. In this study, the effect ofa tissue-independent PRC for 68Ga was investigated on patient data. PET/CT data (40 patients: [68Ga]Ga-DOTATOC or [68Ga]Ga-PSMA) were reconstructed using Q.Clear reconstruction algorithm. Two reconstructions were performed per patient, Q.Clear with and without PRC. SUVmax and contrast-to-noise ratio (CNR) values per lesion were compared between PRC and non-PRC images. Five experienced nuclear medicine physicians reviewed the images and chose the preferred reconstruction based on the image quality, lesion detectability, and diagnostic confidence. A total of 155 lesions were identified. The PRC resulted in statistically significant increase of the SUVmax and CNR for soft tissue lesions (6.4%, p < 0.001; 8.6%, p < 0.001), bone lesions (14.6%, p < 0.001; 12.5%, p < 0.001), and lung lesions (3.6%, p = 0.010; 6.3%, p = 0.001). This effect was most prominent in small lesions (SUVmax: 12.0%, p < 0.001, and CNR: 13.0%, p < 0.001). Similar or better image quality, lesion detectability, and diagnostic confidence was achieved in PRC images compared to the non-PRC images as those assessed by the expert readers. A tissue-independent PRC increased the SUVmax and CNR in soft tissue, bone, and lung lesions with a larger effect for the small lesions. Visual assessment demonstrated similar or better image quality, lesion detectability, and diagnostic confidence in PRC images compared to the non-PRC images.

Deep learning reconstruction of zero-echo time sequences to improve visualization of osseous structures and associated pathologies in MRI of cervical spine

ObjectivesTo determine whether deep learning-based reconstructions of zero-echo-time (ZTE-DL) sequences enhance image quality and bone visualization in cervical spine MRI compared to traditional zero-echo-time (ZTE) techniques, and to assess the added value of ZTE-DL sequences alongside standard cervical spine MRI for comprehensive pathology evaluation.MethodsIn this retrospective study, 52 patients underwent cervical spine MRI using ZTE, ZTE-DL, and T2-weighted 3D sequences on a 1.5-Tesla scanner. ZTE-DL sequences were reconstructed from raw data using the AirReconDL algorithm. Three blinded readers independently evaluated image quality, artifacts, and bone delineation on a 5-point Likert scale. Cervical structures and pathologies, including soft tissue and bone components in spinal canal and neural foraminal stenosis, were analyzed. Image quality was quantitatively assessed by signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR).ResultsMean image quality scores were 2.0 ± 0.7 for ZTE and 3.2 ± 0.6 for ZTE-DL, with ZTE-DL exhibiting fewer artifacts and superior bone delineation. Significant differences were observed between T2-weighted and ZTE-DL sequences for evaluating intervertebral space, anterior osteophytes, spinal canal, and neural foraminal stenosis (p < 0.05), with ZTE-DL providing more accurate assessments. ZTE-DL also showed improved evaluation of the osseous components of neural foraminal stenosis compared to ZTE (p < 0.05).ConclusionsZTE-DL sequences offer superior image quality and bone visualization compared to ZTE sequences and enhance standard cervical spine MRI in assessing bone involvement in spinal canal and neural foraminal stenosis.Critical relevance statementDeep learning-based reconstructions improve zero-echo-time sequences in cervical spine MRI by enhancing image quality and bone visualization. This advancement offers additional insights for assessing bone involvement in spinal canal and neural foraminal stenosis, advancing clinical radiology practice.Key PointsConventional MRI encounters challenges with osseous structures due to low signal-to-noise ratio.Zero-echo-time (ZET) sequences offer CT-like images of the C-spine but with lower quality.Deep learning reconstructions improve image quality of zero-echo-time sequences.ZTE sequences with deep learning reconstructions refine cervical spine osseous pathology assessment.These sequences aid assessment of bone involvement in spinal and foraminal stenosis.Graphical

Assessment of a New CT Detector and Filtration Technology: Part 2-Image Quality in Phantoms, Cadavers, and Patients.

The purpose of this work was to evaluate the image quality of a commercial CT scanner equipped with a novel detector and filtration technology called PureVision Optics (PVO). CT number, noise, contrast-to-noise ratio (CNR), modulation transfer function (MTF), and noise power spectrum (NPS) were assessed using the ACR CT Accreditation phantom scanned with various acquisitions at 80 kV, 100 kV, 120 kV, and 135 kV, each with multiple CTDIvol values of 20 mGy, 40 mGy, and 65 mGy. Artifacts were evaluated in an anthropomorphic head phantom, a cadaver head, and in patient studies. Two neuroradiologists assessed image quality features in various patients who were examined with unenhanced brain CT on both scanners. Compared with the conventional scanner, for the same CTDIvol, the PVO scanner produced 20.3% less image noise (P < 0.001), 18.9% higher CNR (P < 0.01), and 24.6% higher spatial resolution (P < 0.001). Streak artifacts were less severe with the PVO scanner for the phantom, cadaver, and patient scans (P < 0.05). Radiologists scored the PVO scanner as significantly better for visualization of the cerebrospinal fluid space over the cerebral sulci in high convexity, image noise in gray and white matter, and artifacts in the posterior fossa. They also significantly preferred the PVO scanner for visualization of the border between brain gray and white matter, cerebrospinal fluid space around the mesencephalon, and overall diagnostic acceptability. For matched CTDIvol values, the scanner equipped with PVO technology produced better objective and subjective image quality metrics in brain CT imaging compared with a conventional CT scanner without PVO. In clinical settings, PVO may allow for lower doses while enhancing imaging through dense areas, improving visualization of subtle details, and offering more effective options for examining obese patients.This research received financial support from Canon Medical Systems USA. The study design and data were fully controlled by the coauthors, of which none are employees or consultants of Canon Medical Systems USA.

Combining Low-energy Images in Dual-energy Spectral CT With Deep Learning Image Reconstruction Algorithm to Improve Inferior Vena Cava Image Quality.

To explore the application of low-energy image in dual-energy spectral CT (DEsCT) combined with deep learning image reconstruction (DLIR) to improve inferior vena cava imaging. Thirty patients with inferior vena cava syndrome underwent contrast-enhanced upper abdominal CT with routine dose, and the 40, 50, 60, 70, and 80keV images in the delayed phase were first reconstructed with the ASiR-V40% algorithm. Image quality was evaluated both quantitatively [CT value, SD, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) for inferior vena cava] and qualitatively to select an optimal energy level with the best image quality. Then, the optimal-energy images were reconstructed again using deep learning image reconstruction medium strength (DLIR-M) and DLIR-H (high strength) algorithms and compared with that of ASiR-V40%. The objective CT value, SD, SNR, and CNR increased with the decrease in energy level, with statistically significant differences (all P<0.05). The 40keV images had the highest CT values, SNR, and CNR and good diagnostic acceptability, and 40keV was selected as the best energy level. Compared with ASiR-V40% and DLIR-M, DLIR-H had the lowest SD, highest SNR and CNR, and subjective score (all P<0.001) with good consistencies between the 2 physicians (all k ≥0.75). The 40keV images with DLIR-H had the highest overall image quality, showing sharper edges of inferior vena cava vessels and clearer lumen in patients with Budd-Chiari syndrome. Compared with the ASiR-V algorithm, DLIR-H significantly reduces image noise and provides the highest CNR and best diagnostic image quality for the 40keV DEsCT images in imaging inferior vena cava.

Optimization of x-ray dark-field CT for human-scale lung imaging.

X-ray grating-based dark-field imaging can sense the small angle scattering caused by object's micro-structures. This technique is sensitive to the porous microstructure of lung alveoli and has the potential to detect lung diseases at an early stage. Up to now, a human-scale dark-field CT (DF-CT) prototype has been built for lung imaging. This study aimed to develop a thorough optimization method for human-scale dark-field lung CT and guide the system design. We introduced a task-based metric formulated as the contrast-to-noise ratio (CNR) between normal and lesioned alveoli for system parameter optimization and designed a digital human-thorax phantom to fit the task of lung disease detection. Furthermore, a computational framework was developed to model the signal propagation in DF-CT and established the link between system parameters and the CNR metric. We showed that for a DF-CT system, its CNR first increases and then decreases with the system auto-correlation length (ACL). The optimal ACL is mostly independent of system's visibility, and is only related to the phantom's properties, that is, its size and absorption. For our phantom, the optimal ACL is about 0.35 µm at the design energy of 60keV. As for system geometry, increasing source-detector and isocenter-detector distance can extend the system's maximal ACL, making it easier for the system to meet the optimal ACL and relaxing the grating pitches. We proposed a set of parameters for a projective fringe system that can satisfy the simulated optimal ACL. This study introduced a task-based metric and a process for DF-CT optimization. We demonstrated that for a given phantom, the detection performance of the system is optimized at a specific ACL. The optimization method and design principles are independent from the underlying dark-field imaging method and can be applied to DF-CT system design using different grating-based implementations such as Talbot-Lau interferometer (TLI) or projective fringe method.

The Clinical Value of the MAR+ Metal Artifact Reduction Algorithm for Postoperative Assessment of Lumbar Internal Fixation.

With the widespread use of lumbar pedicle screws for internal fixation, the morphology of the screws and the surrounding tissues should be evaluated. The metal artifact reduction (MAR) technique can reduce the artifacts caused by pedicle screws, improve the quality of computed tomography (CT) images after pedicle fixation, and provide more imaging information to the clinic. To explore whether the MAR+ method, a projection-based algorithm for correcting metal artifacts through multiple iterative operations, can reduce metal artifacts and have an impact on the structure of the surrounding metal. A total of 57 patients who underwent lumbar spine CT examination after lumbar internal fixation from January to December 2023 in our hospital were retrospectively enrolled. The CT images were reconstructed using MAR+ and non-MAR+ techniques and were subdivided into MAR+ and non-MAR+ groups. The CT number (in Hounsfield units) and the SD noise values of the spinal canal, vertebral body, psoas major muscle, and adjacent fat were measured in the 2 groups of CT images, and the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. The subjective score was evaluated by two diagnostic radiologists using a double-blind method for image quality evaluation of the MAR+ group and the non-MAR+ group, and the image quality was classified on a 5-point scale. The rank-sum test was utilized to compare the subjective and objective scores of the 2 groups. The SD values of the spinal canal (Z=-4.12, P<0.01), vertebral body (Z=-3.81, P<0.01), and psoas major muscle (Z=-3.87, P<0.01) in the MAR+ group were significantly lower than those in the non-MAR+ group (P<0.05). However, the SD values of the adjacent fat (Z=-2.03, P=0.42) in the MAR+ group, although smaller than those in the non-MAR+ group, were not statistically significant. The CNR values of vertebral canal (Z=-2.67, P=0.008) and fat (Z=-2.60, P=0.009) were higher in the MAR+ group than in the non-MAR+ group, whereas the CNR values of the vertebral body (Z=-6.74, P<0.01) in the MAR+ group were smaller than those in the non-MAR+ group, and the difference of all of them was statistically significant (P<0.05). Furthermore, for both CT and SNR values, the MAR group's values were all less than those of the non-MAR group and were statistically significant (P<0.05). The subjective scores of the measurement points were all higher in the MAR+ group than in the non-MAR+ group. The MAR+ technique has a noise reduction effect on different tissues and artifacts are significantly reduced. Although the artifacts caused by metal screws were not completely eliminated, the MAR+ technique was able to reduce the interference of artifacts in the diagnosis of CT images, thus improving their diagnostic quality.

Selective use of ferumoxytol-enhanced magnetic resonance angiography in patients with renal insufficiency: insights from a pilot study.

The use of conventional contrast agents in computed tomography (CT) and magnetic resonance (MR) imaging is often limited in patients with chronic kidney disease (CKD) due to potential nephrotoxicity. Ferumoxytol, originally developed for iron supplementation, has emerged as a promising alternative MR contrast agent that is safer for patients with CKD. This study aims to present our center's experience with ferumoxytol as a contrast agent in CKD patients. We retrospectively reviewed 24 MR imaging studies of the chest, abdomen, and pelvis performed in CKD patients at our center. All patients were deemed suitable for ferumoxytol administration, receiving a dose of 4mg/kg with post-injection monitoring. The imaging quality of the ascending, descending, suprarenal and infrarenal aortic segments was assessed by three independent observers using a qualitative scoring system (nondiagnostic, poor vascular definition, good vascular definition, and excellent vascular definition). Quantitative analyses, including signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and heterogeneity index, were also performed. No adverse reactions to ferumoxytol were observed. Of the 72 vascular segments evaluated, 90.8% of the images were rated as excellent vascular definition, and 9.2% were rated as good vascular definition. Inter-observer agreement was substantial (k = 0.647), with no statistically significant differences in ratings between observers. Ferumoxytol is a safe and effective alternative to conventional contrast agents for MR vascular imaging, particularly in patients with renal insufficiency. These findings support its selective use in appropriate clinical scenarios, offering a reliable imaging option for CKD patients.

Evaluation of charge summing correction in CdTe-based photon-counting detectors for breast CT: performance metrics and image quality.

We evaluate the impact of charge summing correction on a cadmium telluride (CdTe)-based photon-counting detector in breast computed tomography (CT). We employ a custom-built laboratory benchtop system using the X-THOR FX30 0.75-mm CdTe detector (Varex Imaging, Salt Lake City, Utah, United States) with a pixel pitch of 0.1mm, operated in both standard mode [single pixel (SP)] and charge summing correction mode [anticoincidence (AC)]. A tungsten anode source operated at 55kVp with 2-mm aluminum external filtration and tube currents of 25, 100, and 200mA with corresponding exposure times of 20, 5, and 2.5ms were employed to study the effects of X-ray fluence and pulse pileup. Performance comparisons between AC and SP modes are performed in both projection and image reconstructed spaces. In the projection space, performance metrics include count rate, energy resolution, uniformity, modulation transfer function (MTF), and noise power spectrum (NPS). In the image space, performance metrics consist of contrast-to-noise ratio (CNR), uniformity, NPS, and iodine quantification accuracy. For both acquisition modes, signal-to-thickness calibration, for gain and beam hardening corrections, is used before image reconstruction. Images are reconstructed via TIGRE CT software using the standard Feldkamp, Davis, and Kress (FDK) filtered back projection algorithm with a Hann filter and reconstructed with a voxel size of 0.081mm. Material decomposition is performed using a standard image-based method. In the detector space, the application of hardware-based charge summing correction enhances spectral resolution and improves the spatial resolution of MTF at lower energy thresholds but introduces anomalous edge enhancement effects and artifacts in the MTF at high fluence. A negative noise correlation was observed in AC mode-acquired images. As expected, the AC acquisition mode results in a decreased detector count rate. In the image space, NPS results displayed elevated noise in low-energy AC images. However, at high energy, noise was comparable between both modes. Greater uniformity was observed in SP mode-acquired images. The largest disparity was observed in the iodine quantification test, where the AC mode demonstrates a much stronger linear relationship between estimated and true iodine concentrations than the SP mode. The results are specific to the studied system, reconstruction parameters, and irradiation conditions limited to 200mA and 0.5 mAs. The AC mode generally provides better energy and MTF resolution at low energy thresholds but with increased noise and reduced uniformity. In image space, charge summing correction improved iodine quantification and CNR at high energy thresholds.

Quantitative and Visual Benefits of Data-Driven Motion Correction on Oncologic PET/CT: AProspective Cross-sectional Study.

Conventional positron emission tomography (PET) respiratory gating utilizes a fraction of acquired PET counts (i.e., optimal gate [OG]), whereas elastic motion correction with deblurring (EMCD) utilizes all PET counts to reconstruct motion-corrected images without increasing image noise. Our aim was to assess the quantitative and visual impacts of EMCD-based motion correction on FDG-PET and DOTATATE-PET images relative to OG and ungated (UG) images. This prospective, single-center study enrolled adults undergoing FDG or DOTATATE oncologic PET/CT between June 2020 and October 2022. Subjects underwent a standard-of-care (SOC) PET acquisition while wearing a respiratory gating belt. UG, belt-gating-derived optimal gate (BG-OG), EMCD utilizing belt gating (BG-EMCD), and EMCD utilizing data-driven gating (DDG-EMCD) images were reconstructed. Tracer-avid lesions in the lower chest or upper abdomen were segmented. Quantitative metrics were extracted. Two independent, blinded readers assessed image quality via a 4-point scale and counted lesions on each reconstruction. Differences between reconstructions were assessed via the Wilcoxon signed-rank test (alpha, 0.05). This study enrolled 78 subjects; 36 subjects (mean age, 64.8 years; 20 males) with 136 tracer-avid lesions were analyzed. Data provided are medians across all tracers. Lesion SUV-max was significantly higher (P<0.001) on motion-corrected images (BG-OG: 10.77, BG-EMCD: 10.75, DDG-EMCD: 10.74) than UG images (9.00). Lesion contrast-to-noise ratios (CNRs) were significantly lower (P<0.001) for BG-OG (6.31) and UG images (7.89) than BG-EMCD (9.14) and DDG-EMCD (8.89) images. FDG and DOTATATE subgroup analyses produced similar results. Among motion-corrected images, both readers preferred EMCD-based images to BG-OG images for all tracers (P<0.001) and both subgroups. EMCD-based images occasionally demonstrated more tracer-avid lesions than BG-OG or UG images. EMCD-based motion correction beneficially impacts lesion quantitation (including higher SUVs and CNRs) and overall image quality. When employed on capable scanners, EMCD can improve the quality of oncologic PET imaging.

Clinical application of third-generation dual-source CT-based dynamic imaging reconstruction for pulmonary embolism imaging

BackgroundTo evaluate the clinical diagnostic value of third-generation dual-source CT for pulmonary embolism, focusing on the optimization of dual-source CT scanning with dynamic reconstruction in acute pulmonary embolism (PE) and various imaging manifestations.MethodsEighty-two patients with pulmonary embolism were enrolled and randomly divided into standard CT angiography (SCTA) and dynamic CT angiography (DCTA). DCTA patients were divided into dynamic CT angiography arterial phase (DCTAa), time phase Angiography reconstruction (TMIP-CTA), and 4D noise reduction TMIP-CTA according to the image reconstruction. The region of interest was selected in the region of the pulmonary trunk and its branches, respectively. The vessel CT value and image background noise (IN) of each subgroup were also determined, and the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. Simultaneously two radiologists performed a subjective evaluation of the quality of the picture images.ResultsThe DCTA group had a lower contrast dose than the SCAT group, but the vessel CT value, IN, CNR, and SNR were significantly higher in the DCTA group compared with the SCTA group. CT of the vascular lumen was generally higher in all subgroups of DCTA than in SCTA, with the highest in the TMIP-CIA group. IN was significantly higher in both the DCTAa and TMIP-CTA groups than in the SCTA group. SNR and CNR were elevated in TMIP-CTA and 4D noise reduction TMIP-CTA compared to the SCTA group. In addition, the subjective image quality scores of the DCTA group were significantly higher than those of SCTA, and the 4D noise reduction TMIP-CTA had the most. However, the ED of the SCTA group was lower than that of the DCTA group.Conclusion4D noise reduction TMIP-CTA based on DCTA reconstruction significantly improves the quality of pulmonary artery CTPA images and increases the clinical diagnostic rate, with potential for clinical dissemination.

Improving Image Quality and Decreasing SAR With High Dielectric Constant Pads in 3 T Fetal MRI.

At high magnetic fields, degraded image quality due to dielectric artifacts and elevated specific absorption rate (SAR) are two technical challenges in fetal MRI. To assess the potential of high dielectric constant (HDC) pad in increasing image quality and decreasing SAR for 3 T fetal MRI. Prospective. 3 T. Balanced steady-state free precession (bSSFP) and single-shot fast spin-echo (SSFSE). One hundred twenty-eight participants (maternal-age 29.0 ± 3.6, range 20-40; gestational-age 30.3 ± 3.5 weeks, range 22-37 weeks) undertook bSSFP and 40 participants (maternal-age 29.5 ± 3.8, range 19-40; gestational-age 30.4 ± 3.5 weeks, range 23-37 weeks) undertook SSFSE. Patient clinical characteristics were recorded, such as gestational-age, amniotic-fluid-index, abdominal-circumference, body-mass-index, and fetal-presentation. Quantitative Image-quality analysis included signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). Qualitative analysis was performed by three radiologists with four-point scale to evaluate overall image quality, dielectric artifact, and diagnostic confidence. Whole-body total SAR was obtained from the vendor workstation. Paired rank sum test was used to analyze the differences in SNR, CNR, overall image quality, dielectric artifact, diagnostic confidence, and SAR with and without HDC pad. Spearman correlation test was used to detect correlations between image quality variable changes and patient clinical characteristics. P values <0.05 were set as statistical significance. With HDC pad, SNR and CNR was significantly higher (41.45% increase in SNR, 54.05% increase in CNR on bSSFP; 258.76% increase in SNR, 459.55% increase in CNR on SSFSE). Overall qualitative image quality, dielectric artifact and diagnostic confidence improved significantly. Adding HDC pad significantly reduced Whole-body total SAR (32.60% on bSSFP; 15.40% on SSFSE). There was no significant correlation between image quality variable changes and participant clinical characteristics (P-values ranging from 0.072 to 0.992). In the clinical setting, adding a HDC pad might increase image quality while reducing dielectric artifact and SAR. Dielectric artifacts and elevated SAR are two technical problems in 3T fetal MRI. In a prospective analysis of 168 pregnant participants undertaking 3.0T fetal MRI scanning, high dielectric constant (HDC) pad increased SNR by 41.45%, CNR by 54.05% on bSSFP, and SNR by 258.76%, CNR by 459.55% on SSFSE. Overall image quality, dielectric artifact reduction, and diagnostic confidence assessed by three radiologists was improved. Whole-body total SAR decreased by 32.60% on bSSFP and by 15.40% on SSFSE. These findings suggested that the HDC pad can enhance fetal MRI safety and quality, making it a promising tool for clinical practice. 2 TECHNICAL EFFICACY: Stage 5.