Computed Tomography For Detection Research Articles

Reduction of Streak Artifacts in the Superior Vena Cava for Better Visualization of Mediastinal Structures Through Virtual Monoenergetic Reconstructions Using a Photon-counting Detector Computed Tomography.

Computed tomography (CT) is crucial in oncologic imaging for precise diagnosis and staging. Beam-hardening artifacts from contrast media in the superior vena cava can degrade image quality and obscure adjacent structures, complicating lymph node assessment. This study examines the use of virtual monoenergetic reconstruction with photon-counting detector CT (photon-counting CT) to mitigate these artifacts. The retrospective study included 50 patients who underwent thoracoabdominal scans. Virtual monoenergetic reconstructions at nine keV levels (60 to 140 keV) were analyzed for Hounsfield Unit (HU) stability, image noise, and artifact index in various regions of interest (ROIs): mediastinal adipose tissue (ROI 1 to 3) and vascular stations (ROI 4 to 6) were compared with reference tissue (ROI 7 to 8). The diagnostic image quality of the keV levels was assessed using a 5-point Likert Scale. Lower keV values (60 to 80) exhibited higher image noise and lower HU stability in mediastinal adipose tissue compared with higher energies, with optimal noise reduction observed at 130 keV (ROI 1 to 3). HU stability in vascular structures (ROI 4 to 6) significantly improved above 80 keV, with the best performance at 140 keV. Artifact levels decreased progressively from 60 to 140 keV. Visually, keV levels of 110 keV (96% Likert ≥4) and 120 keV (60% Likert 4) were rated most diagnostically valuable, consistent with technical findings. Virtual monoenergetic reconstructions with photon-counting CT effectively reduce beam-hardening artifacts near the superior vena cava, enhancing the visualization of lymph nodes and adjacent structures. This technology advances oncologic imaging by improving diagnostic accuracy in areas previously affected by artifact-related image degradation.

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 assessment of early changes in myocardial extracellular volume during postoperative adjuvant chemotherapy in patients with breast cancer via dual-layer spectral detector computed tomography: a cohort study.

The major of anticancer therapies induce a wide spectrum of cardiotoxic effects. Early identification of anticancer treatment-associated cardiotoxicity is critical to informing decisions on subsequent interventions. Myocardial extracellular volume (ECV) has been proposed as a useful parameter for quantifying the early cardiotoxicity of cancer-related treatment. This study used dual-layer spectral detector computed tomography (CT) technology to simultaneously assess cardiac function and myocardial ECV, characterizing the early changes in parameters during breast cancer therapy. A single-center cohort study was conducted that prospectively enrolled 40 women with breast cancer (mean age 47.5±10.8 years) who underwent postoperative adjuvant chemotherapy between January 12, 2022, and November 2, 2023, with available data from baseline to 3 months after chemotherapy of cardiac computed tomography (CCT), ultrasound cardiography (UCG), electrocardiography, and serum biomarkers. Midventricular and global ECVs of the left ventricle were measured based on an iodine map of the late enhancement phase of dual-layer spectral detector CT. Changes in cardiac function parameters, ECVs, and cardiac biomarkers from baseline to the 3-month follow-up were analyzed. Correlation coefficients between the changes in cardiac function parameters and ECVs were calculated. Between baseline and 3 months, there was no significant change in left ventricular ejection fraction (LVEF) on UCG (67.1%±3.8% vs. 66.3%±4.3%, P=0.29) or LVEF on CCT (65.4%±5.9% vs. 64.3%±7.4%, P=0.28). Heart rate increased over 3 months of follow-up (75.2±11.5 vs. 81.7±12.3 bpm; P<0.01). After normalization to body surface area (BSA), cardiac output on CCT/BSA ratio (CCT-CO indexed) (3.5±0.6 vs. 3.8±0.6 L/(min·m2); P=0.01) and left ventricular late (active) filling volume/BSA ratio (LVLFV indexed) (13.5±3.7 vs. 15.8±4.2 mL/m2; P<0.01) significantly increased, while there was a significant decrease at the 3-month follow-up in left ventricular early (passive) filling volume/BSA ratio (LVEFV indexed) (33.3±6.6 vs. 30.6±8.2 mL/m2; P=0.01) and LVEFV/LVLFV ratio (2.7±1.1 vs. 2.1±0.9; P<0.01). Midventricular and global ECVs were elevated at 3 months, significantly so for the midanterior ECV (24.0%±4.5% vs. 25.6%±3.1%; P=0.04), midaverage ECV (25.6%±2.5% vs. 27.0%±2.9%; P=0.01) and global ECV (25.4%±2.4% vs. 27.3%±2.7%; P<0.01). Although changes in ECVs were not associated with changes in LVEFs, global ECV changes were moderately correlated with changes in left ventricular end-diastolic volume/BSA ratio (CCT-LVEDV indexed) (r=0.52; P<0.001), left ventricular stroke volume/BSA ratio (CCT-LVSV indexed) (r=0.56; P<0.001), CCT-CO indexed (r=0.40; P=0.01), and LVEFV indexed (r=0.41; P=0.009). CCT-derived ECV was used to evaluate myocardial changes in the early stage of chemotherapy before LVEF significantly decreased. The increases in ECV were not correlated with LVEF. The changes in myocardial ECVs were moderately correlated with cardiac function parameters. ECV may be a useful biomarker for detecting cardiotoxicity in patients with breast cancer in the early stage of anticancer therapy.

A study on CT detection image generation based on decompound synthesize method

Background Nuclear graphite and carbon components are vital structural elements in the cores of high-temperature gas-cooled reactors(HTGR), serving crucial roles in neutron reflection, moderation, and insulation. The structural integrity and stable operation of these reactors heavily depend on the quality of these components. Helical Computed Tomography (CT) technology provides a method for detecting and intelligently identifying defects within these structures. However, the scarcity of defect datasets limits the performance of deep learning-based detection algorithms due to small sample sizes and class imbalance. Objective Given the limited number of actual CT reconstruction images of components and the sparse distribution of defects, this study aims to address the challenges of small sample sizes and class imbalance in defect detection model training by generating approximate CT reconstruction images to augment the defect detection training dataset. Methods We propose a novel CT detection image generation algorithm called the Decompound Synthesize Method (DSM), which decomposes the image generation process into three steps: model conversion, background generation, and defect synthesis. First, STL files of various industrial components are converted into voxel data, which undergo forward projection and image reconstruction to obtain corresponding CT images. Next, the Contour-CycleGAN model is employed to generate synthetic images that closely resemble actual CT images. Finally, defects are randomly sampled from an existing defect library and added to the images using the Copy-Adjust-Paste (CAP) method. These steps significantly expand the training dataset with images that closely mimic actual CT reconstructions. Results Experimental results validate the effectiveness of the proposed image generation method in defect detection tasks. Datasets generated using DSM exhibit greater similarity to actual CT images, and when combined with original data for training, these datasets enhance defect detection accuracy compared to using only the original images. Conclusion The DSM shows promise in addressing the challenges of small sample sizes and class imbalance. Future research can focus on further optimizing the generation algorithm and refining the model structure to enhance the performance and accuracy of defect detection models.

Recent Advancements in CT Detectors: A Comprehensive Review

The Computed Tomography (CT) scanners are widely used in the diagnostic and therapeutic medical fields due to their quick scanning times, excellent spatial resolution and widespread availability. The X-ray detector is essential for creating images and has a significant impact on radiation dose and image quality. All current commercial scanners use solid-state detectors and are comparable to third-generation technology. Detector characteristics include efficiency, stability, response time and afterglow. CT scanners have been used since 1971, and in the intervening decades, the technology has advanced tremendously. Notable developments in detector technologies have improved image quality and decreased radiation doses. The EMI head scanner was first equipped with Sodium Iodide (NaI) detectors, which necessitated long scan periods and a water bath to control detector saturation. These designs were improved upon by later generations, which offered quicker scanning speeds and better image quality. While the fourth generation of scanners used a stationary ring of detectors to drastically reduce scan durations, the thirdgeneration scanners introduced fan beams and rotation-rotation action. The sixth generation, called dual-source CT, allowed for dual-energy imaging using two X-ray tubes. The fifth generation, called electron-beam CT, produced X-rays using an electron beam. The seventh generation replaced traditional X-ray film with Flat-panel Detectors (FPD), which improved imaging. CT detector advancements include gemstone, stellar, photon counting, and NanoPanel prism detectors. The gemstone scintillator material is produced by General Electric Healthcare (GEHC). The Photon-counting Detector (PCD) is a new CT detector technology that uses a direct conversion X-ray detector to record X-ray photon energies. The stellar detector is based on Siemens Healthineers, and the NanoPanel prism detector is based on Philips. The present article discusses the recent trends in CT detector technology.

Deep learning estimation of proton stopping power with photon-counting computed tomography: a virtual study.

Proton radiation therapy may achieve precise dose delivery to the tumor while sparing non-cancerous surrounding tissue, owing to the distinct Bragg peaks of protons. Aligning the high-dose region with the tumor requires accurate estimates of the proton stopping power ratio (SPR) of patient tissues, commonly derived from computed tomography (CT) image data. Photon-counting detectors for CT have demonstrated advantages over their energy-integrating counterparts, such as improved quantitative imaging, higher spatial resolution, and filtering of electronic noise. We assessed the potential of photon-counting computed tomography (PCCT) for improving SPR estimation by training a deep neural network on a domain transform from PCCT images to SPR maps. The XCAT phantom was used to simulate PCCT images of the head with CatSim, as well as to compute corresponding ground truth SPR maps. The tube current was set to 260mA, tube voltage to 120kV, and number of view angles to 4000. The CT images and SPR maps were used as input and labels for training a U-Net. Prediction of SPR with the network yielded average root mean square errors (RMSE) of 0.26% to 0.41%, which was an improvement on the RMSE for methods based on physical modeling developed for single-energy CT at 0.40% to 1.30% and dual-energy CT at 0.41% to 3.00%, performed on the simulated PCCT data. These early results show promise for using a combination of PCCT and deep learning for estimating SPR, which in extension demonstrates potential for reducing the beam range uncertainty in proton therapy.

Extra cellular volume by computed tomography is useful for prediction of prognosis in cardiac sarcoidosis

Abstract Background Extracellular volume (ECV) fraction on magnetic resonance imaging (MRI) has been useful in evaluating the degree of myocardial fibrosis and has been reported to help diagnose and evaluate the prognosis of cardiomyopathy. However, there are also several contraindications in the cardiac MRI, and the performance of it takes time. Computed tomography (CT) helps screen for coronary artery disease, is more versatile than cardiac MRI, and is also useful in screening for coronary artery disease. Myocardial extracellular volume (ECV) analysis on CT has been recently eligible and has shown a good correlation with ECV on MRI. We hypothesized that ECV on CT, a new fibrosis indicator, would be useful in predicting prognosis in patients with cardiac sarcoidosis (CS). Purpose The purpose of this study is to evaluate the utility of ECV analysis on CT for predicting major adverse cardiac events (MACEs) in cases with cardiac sarcoidosis (CS). Methods As a single-center study, 48 patients (18 males, 67 ± 11 years old) diagnosed with CS based on the 2016 Japanese Circulation Society criteria and who underwent cardiac CT using 320-row detector CT or 256-row detector CT, and including late-phase images from December 2008 to January 2024 were analyzed retrospectively. We evaluated the ECV of left ventricular myocardium (LVM) using commercially available software (Figure A). The primary endpoint was MACEs, a composite of all-cause death, heart failure hospitalization, and fatal ventricular arrhythmia. Results Among all 48 patients, 14 combined events (10 fatal ventricular arrhythmias, three heart failure hospitalizations, and one all-cause death) were observed during a follow-up of 56 ± 57 months. ECV of LVM on CT was significantly higher in patients with MACEs than the others (37 ± 5.6% vs 33 ± 4.6%, P = 0.0087). The best cut-off value of ECV of LVM on CT for prediction of MACEs was 34.97%, and the sensitivity and specificity of LV-ECV to predict MACEs were 71% and 76% at the best cut-off, and the area under the curve was 0.73 based on the receiver operating characteristics curve analysis (P = 0.009) (Figure B). The cases with ECV ≥ 34.97% (n = 18) had significantly higher MACEs than the cases with ECV &amp;lt; 34.97% based on the Kaplan-Meier analysis (P = 0.0031) (Figure C). In the multivariate Cox proportional hazard model, ECV on LVM (Hazard ratio 1.11, 95% confidence interval 1.00-1.21, p=0.0493) and history of VT ablation (Hazard ratio 27.7, 95% confidence interval 4.27-180, p=0.0011) were the significant predictors of MACEs. Conclusion Adverse events mainly caused by fatal ventricular arrhythmia are relatively common in CS. Evaluation of ECV by CT may be useful for the prediction of MACEs in cases with CS.

Application value of SOMATOM Force computed tomography in assisting the preoperative localization of colorectal cancer resection surgery

Background The objective of this study was to assess the application value of SOMATOM Force computed tomography (CT) in assisting the preoperative localization of colorectal cancer resection surgery. Method Retrospectively, the medical data of 120 inpatients with colorectal cancer were collected. The Kappa consistency test was used to evaluate diagnostic consistency in the localization and staging of colorectal cancer. The diagnostic value of preoperative SOMATOM Force CT detection was analyzed. Results In 120 colorectal cancer patients, the accuracy of SOMATOM Force CT for preoperative localization, T staging, and N staging of colorectal cancer were 91.7% (kappa = 0.837), 88.3% (kappa = 0.772) and 91.7% (kappa = 0.773), respectively. Among 45 rectum cancer patients, there were 19 positive cases with circumferential resection margin involvement, and the accuracy of SOMATOM Force CT detection was 86.7% (kappa = 0.767). The sensitivity, specificity, positive predictive value, and negative predictive value of SOMATOM Force CT detection in evaluating the circumferential resection margin involvement of rectum cancer were 78.95%, 96.15%, 93.75%, and 86.21%, respectively. Conclusions There was an important application value of SOMATOM Force CT in assisting the preoperative localization and tumor staging of colorectal cancer resection surgery. There was a good diagnostic value of preoperative SOMATOM Force CT detection in evaluating the circumferential resection margin involvement of rectum cancer.

Diagnostic Performance and Clinical Impact of Photon-Counting Detector Computed Tomography in Coronary Artery Disease.

Photon-counting detector-computed tomography (PCD-CT) has emerged as a promising technology, offering improved spatial resolution. This study aimed to evaluate the clinical impact and diagnostic performance of PCD-CT vs conventional energy-integrating detector computed tomography (EID-CT) for obstructive coronary artery disease (CAD). From 2022 to 2023, we retrospectively identified 7,833 consecutive patients who underwent clinically indicated coronary computed tomography angiography (CCTA) at a single center, with either PCD-CT (n=3,876; NAEOTOM Alpha [Siemens Healthineers]) or EID-CT (n=3,957; Revolution Apex 256 [GE HealthCare] or Aquilion ONE ViSION 320 [Canon Medical Systems]) scanners. Subsequent invasive coronary angiography (ICA) and percutaneous or surgical revascularization were performed as part of routine clinical care. Among those referred for ICA after coronary CTA, the presence of obstructive CAD in each vessel was determined by coronary CTA (severe stenosis on visual assessment per the Coronary Artery Disease Reporting and Data System) and ICA (≥50% diameter stenosis on quantitative coronary angiography) in a blinded fashion. The diagnostic performance of EID-CT and PCD-CT was compared by using quantitative coronary angiography as the reference standard. Patients who underwent PCD-CT were less frequently referred to subsequent ICA than those undergoing EID-CT (9.9% vs 13.1%; P< 0.001). Among those who underwent ICA, revascularization was more frequently performed in the PCD-CT group than in the EID-CT group (43.4% vs 35.5%; P=0.02). In the vessel-level analysis (n=1,686), specificity (98.0% vs 93.0%; P< 0.001), positive predictive value (83.3% vs 63.0%; P=0.002), and diagnostic accuracy (97.2% vs 92.8%; P< 0.001) were improved by PCD-CT. Sensitivity (90.9% vs 90.7%; P=0.95) and negative predictive value (98.9% vs 98.7%; P=0.83) for obstructive CAD were similar between the PCD-CT and EID-CT groups, respectively. PCD-CT exhibited excellent diagnostic performance for detecting obstructive CAD. Compared with patients undergoing conventional EID-CT, fewer patients were referred to ICA after PCD-CT, but those referred were more likely to undergo revascularization.

Low-dose high-resolution chest CT in adults with cystic fibrosis: intraindividual comparison between photon-counting and energy-integrating detector CT

BackgroundRegular disease monitoring with low-dose high-resolution (LD-HR) computed tomography (CT) scans is necessary for the clinical management of people with cystic fibrosis (pwCF). The aim of this study was to compare the image quality and radiation dose of LD-HR protocols between photon-counting CT (PCCT) and energy-integrating detector system CT (EID-CT) in pwCF.MethodsThis retrospective study included 23 pwCF undergoing LD-HR chest CT with PCCT who had previously undergone LD-HR chest CT with EID-CT. An intraindividual comparison of radiation dose and image quality was conducted. The study measured the dose-length product, volumetric CT dose index, effective dose and signal-to-noise ratio (SNR). Three blinded radiologists assessed the overall image quality, image sharpness, and image noise using a 5-point Likert scale ranging from 1 (deficient) to 5 (very good) for image quality and image sharpness and from 1 (very high) to 5 (very low) for image noise.ResultsPCCT used approximately 42% less radiation dose than EID-CT (median effective dose 0.54 versus 0.93 mSv, p < 0.001). PCCT was consistently rated higher than EID-CT for overall image quality and image sharpness. Additionally, image noise was lower with PCCT compared to EID-CT. The average SNR of the lung parenchyma was lower with PCCT compared to EID-CT (p < 0.001).ConclusionIn pwCF, LD-HR chest CT protocols using PCCT scans provided significantly better image quality and reduced radiation exposure compared to EID-CT.Relevance statementIn pwCF, regular follow-up could be performed through photon-counting CT instead of EID-CT, with substantial advantages in terms of both lower radiation exposure and increased image quality.Key PointsPhoton-counting CT (PCCT) and energy-integrating detector system CT (EID-CT) were compared in 23 people with cystic fibrosis (pwCF).Image quality was rated higher for PCCT than for EID-CT.PCCT used approximately 42% less radiation dose and offered superior image quality than EID-CT.Graphical

Photon-counting CT for forensic death investigations-a glance into the future of virtual autopsy.

This article explores the potential of photon-counting computed tomography (CT) in forensic medicine for a range of forensic applications. Photon-counting CT surpasses conventional CT in several key areas. It boasts superior spatial and contrast resolution, enhanced image quality at low x-ray energies, and spectral imaging capabilities that enable more precise material differentiation. These advantages translate to superior visualization of bone structures, foreign bodies, and soft tissues in postmortem examinations. The article discusses the technical principles of photon-counting CT detectors and highlights its potential applications in forensic imaging, including high-resolution virtual autopsies, pediatric forensic CT, trauma analysis, and bone density measurements. Furthermore, advancements in vascular imaging and soft tissue contrast promise to propel CT-based death investigations to an even more prominent role. The article concludes by emphasizing the immense potential of this new technology in forensic medicine and anthropology.

Clinical assessment of computed tomography for detecting ingested blister packs: A single-center retrospective study.

Blister pack (BP) ingestion poses serious risks, such as gastrointestinal perforation, and accurate localization by computed tomography (CT) is a common practice. However, while it has been reported in vitro that CT visibility varies with the material type of BPs, there have been no reports on this variability in clinical settings. In this study, we investigated the CT detection rates of different BPs in clinical settings. This single-center retrospective study from 2010 to 2022 included patients who underwent endoscopic foreign body removal for BP ingestion. The patients were categorized into two groups for BP components, the polypropylene (PP) and the polyvinyl chloride (PVC)/polyvinylidene chloride (PVDC) groups. The primary outcome was the comparison of CT detection rates between the groups. We also evaluated whether the BPs contained tablets and analyzed their locations. This study included 61 patients (15 in the PP group and 46 in the PVC/PVDC group). Detection rates were 97.8% for the PVC/PVDC group compared to 53.3% for the PP group, a significant difference (p < 0.01). No cases of BPs composed solely of PP were detected by CT. Blister packs were most commonly found in the upper thoracic esophagus. Even in a clinical setting, the detection rates of PVC and PVDC were higher than that of PP alone. Identifying PP without tablets has proven challenging in clinical. Considering the risk of perforation, these findings suggest that esophagogastroduodenoscopy may be necessary, even if CT detection is negative.

Evaluation the effect of wide-body detector CT under free breathing combined with cardiac motion correction technology on CCTA image quality

PurposeTo explore the feasibility of using wide-body detector Computed Tomography (CT) combined with Cardiac Motion Correction (CMC) technology for coronary Computed Tomography angiography (CCTA) in free breathing state and its impact on image quality. Methods120 patients who underwent CCTA scans at our institution from March 2023 to December 2023 were collected in this retrospective study. Recorded the coronary artery images before applying CMC technology as the control group, and the images after applying CMC technology as the experimental group. Patients were divided into two groups by different heart rate (HR), Group A (HR > 70 bpm) and Group B (HR ≤ 70 bpm), with 66 patients in group A and 54 patients in group B. Subjective image quality assessments were performed on the left anterior descending artery (LAD), left circumflex artery (LCX), and right coronary artery (RCA) proximal segments. These assessments were conducted by two senior radiologists using a double-blind approach and a 4-point scale (1 indicating poor image quality and 4 indicating excellent image quality). The subjective scores among the three coronary artery segments were analyzed by chi-square test, using Kappa coefficient to analyze the inter-observer agreement. ResultsThe control group had a subjective score of 3.37 ± 0.81/3.27 ± 0.83 for the LCX, 2.97 ± 0.85/2.93 ± 0.78 for the LAD, and 2.70 ± 0.75/2.80 ± 0.66 for the RCA. The experimental group had a subjective score of 3.90 ± 0.31/3.83 ± 0.38 for the LCX, 3.83 ± 0.38/3.87 ± 0.35 for the LAD, and 3.87 ± 0.35/3.83 ± 0.38 for the RCA. There was a great enhancement in the image quality observed in the experimental group when contrasted with the control group both in group A and group B (all P < 0.05). The inter-observer consistency of LCX, LAD and RCA were 0.726, 0.801 and 0.734 in control group and 0.769, 0.870 and 0.870 in experimental group. ConclusionThe utilization of CMC technology significantly enhances the quality of CCTA images acquired during free breathing.

Assessing tissue differentiation capabilities in X-ray imaging through cadmium zinc telluride (CZT) photon counting detectors.

In recent years, the use of photon-counting detection technology has resulted in significant X-ray imaging research. This advanced technology holds considerable promise for enhancing Computed Tomography (CT) scanners, offering a potential solution to the limitations inherent in traditional CT detectors. The ongoing studies are dedicated to assessing the effectiveness and sensitivity of semiconductor detector materials in photon counting detectors, particularly in their ability to detect soft tissue contrasts. This study aimed to characterize the performance of the Cadmium Zinc Telluride (CZT) photon counting detector in identifying various tissues with a focus on assessing its sensitivity in distinguishing tissue types in X-ray imaging. An optimal frame rate per second (FPS) of the CZT detector was evaluated by setting the X-ray tube voltage and current at 25 keV and 35 keV and 0.5 mA, 1.0 mA respectively. By keeping the optimum FPS fixed, the detector energy thresholds were set in small steps from 15 keV to 35 keV and the tube currents were set for X-ray tubes in ranges of 0.1 mA–1.0 mA to evaluate the relationship between voltage and current of the X-ray source and counts per second (CPS). The specimens, including fat, liver, muscles, paraffin wax, and contrast media were placed on a stair-step chamber constructed from Plexi-glass, spanning six distinct thickness levels. We investigated X-ray transmission across these tissue samples at varying thicknesses, exploring five energy thresholds: 21 keV, 25 keV, 29 keV, 31 keV, and 45 keV to evaluate their impact on the CPS. This study found that a frame rate of 12 frames per second optimally aligns with the spectral response of the X-ray source. Furthermore, a linear correlation is present between the CPS and the X-ray tube current. The transmission of X-rays through a sample depends on its thickness, a phenomenon observed across different energy thresholds in this study. The detectors exhibit high sensitivity and linearity, ensuring accurate and reliable measurements in diverse imaging scenarios, making them invaluable tools for precise data acquisition in both research and clinical applications.

Advanced Imaging of Total Knee Arthroplasty.

The prevalence of total knee arthroplasty (TKA) is increasing with the aging population. Although long-term results are satisfactory, suspected postoperative complications often require imaging with the implant in place. Advancements in computed tomography (CT), such as tin prefiltration, metal artifact reduction algorithms, dual-energy CT with virtual monoenergetic imaging postprocessing, and the application of cone-beam CT and photon-counting detector CT, allow a better depiction of the tissues adjacent to the metal. For magnetic resonance imaging (MRI), high bandwidth (BW) optimization, the combination of view angle tilting and high BW, as well as multispectral imaging techniques with multiacquisition variable-resonance image combination or slice encoding metal artifact correction, have significantly improved imaging around metal implants, turning MRI into a useful clinical tool for patients with suspected TKA complications.

LEAFLETS AND EXTRA–LEAFLETS HYPOATTENUATED LESIONS FOLLOWING TAVR

Abstract Introduction Subclinical leaflets thrombosis is a condition diagnosed with multi–detector computer tomography (MDCT) characterized by a meniscal–shaped hypoattenuated lesion of one or more leaflets. Transcatheter aortic self–expandable valves are commonly manufactured with pliable pericardium over a nitinol frame that forms the leaflets and the extra–leaflets components, such as the valve skirt. Little is known about extra–leaflets hypoattenuated lesions localization, including the anatomic sinus level. Methods This was an ambi–directional study. Fifty patients underwent MDCT at follow–up. Results At mean follow–up was of 12 months, hypoattenuated leaflet lesion with mild to severe restricted movement was detected in 8 individuals (16%); anatomic sinus lesion was identified in 9 patients (18%) with higher prevalence in the non–coronary sinus (16%); subvalvular lesion with a variable extension toward the valve inflow, was diagnosed in 8 patients (16%). In 4 patients (8%) the anatomic sinus thrombus was ‘in overlap’ with the leaflet thrombus; in 3 patients (6%) was in continuity with the subvalvular frame thrombus. Bicuspid valve was the only independent predictor associated with hypoattenuated lesions (adj OR 8.25 (95% CI: 1.38, 49.21), p=0.02). Conclusions This study demonstrated that hypoattenuated lesions could be identified not only at leaflet, but also at subvalvular and anatomic sinus level. The clinical relevance of such lesions remains uncertain.

The tibial tubercle-to-trochlear groove distance changes in standing weight-bearing condition: An upright weight-bearing computed tomography analysis

BackgroundThe tibial tubercle-to-trochlear groove (TT-TG) distance and Insall-Salvati (I/S) ratio are widely used to determine the need for distal realignment in conjunction with medial patellofemoral ligament (MPFL) reconstruction in patients with recurrent patellar dislocation. A TT-TG distance >20 mm and an I/S ratio >1.3 are significant anatomical risk factors for patellar instability. However, these parameters have traditionally been measured using non-weight-bearing (NWB) imaging modalities. As patellar dislocation occurs during weight-bearing actions, these two parameters should be measured under weight-bearing conditions. Thus, this study aimed to measure the TT-TG distance and I/S ratio using upright full-weight-bearing (FWB) computed tomography (CT) scans and compare the data with NWB CT scans. MethodsThis study included 49 knee joints of 26 healthy volunteers. CT images were obtained under both FWB and NWB standing conditions using a 320-detector row upright CT scanner. TT-TGs in the axial plane and I/S ratios in the sagittal plane were measured and compared. ResultsThe average FWB TT-TG distance was 20.3 ± 3.9 mm, whereas the average NWB TT-TG distance was 12.3 ± 4.7 mm. The TT-TG level was significantly higher in the FWB condition than that in the NWB condition (P < 0.001). The I/S ratios were comparable between the FWB and NWB conditions (P = 0.29). ConclusionsThe TT-TG distance in the standing weight-bearing condition was larger than the conventional TT-TG distance and surpassed the historical cutoff value of TT-TG, which may affect the indication of additional distal realignment in MPFL reconstruction for patellar instability.

Significance of upper cervical epidural venous engorgement on head computed tomography in the initial diagnosis of spontaneous intracranial hypotension: patient series.

Spontaneous intracranial hypotension (SIH) is a rare condition characterized by positional headache, for which contrast-enhanced magnetic resonance imaging (MRI) is the preferred diagnostic method. Although MRI reveals characteristic findings, head computed tomography (CT) is usually the first diagnostic step, but identifying features of SIH on CT is often difficult. This study was specifically designed to evaluate the utility of head CT in detecting upper cervical epidural venous engorgement as a sign of SIH. Of 24 patients with SIH diagnosed between March 2011 and May 2023, 10 did not undergo upper cervical CT. In the remaining 14 patients, engorgement of the upper cervical epidural venous plexus was observed. CT detection rates were consistent with MRI for spinal fluid accumulation or dural thickening. After treatment, in 92.9% of patients, the thickness of the epidural venous plexus decreased statistically significantly from 4.8 ± 1.3 mm to 3.6 ± 1.2 mm. This study suggests that upper cervical spine CT focused on epidural venous engorgement may be helpful in the initial diagnosis of SIH and may complement conventional MRI evaluation. Extending CT imaging to the upper cervical spine will improve the diagnostic accuracy of patients with positional headaches suspected to be SIH.

First experimental evaluation of a high-resolution deep silicon photon-counting sensor.

Current photon-counting computed tomography detectors are limited to a pixel size of around 0.3 to 0.5mm due to excessive charge sharing degrading the dose efficiency and energy resolution as the pixels become smaller. In this work, we present measurements of a prototype photon-counting detector that leverages the charge sharing to reach a theoretical sub-pixel resolution in the order of . The goal of the study is to validate our Monte-Carlo simulation using measurements, enabling further development. We measure the channel response at the MAX IV Lab, in the DanMAX beamline, with a 35keV photon beam, and compare the measurements with a 2D Monte Carlo simulation combined with a charge transport model. Only a few channels on the prototype are connected to keep the number of wire bonds low. The measurements agree generally well with the simulations with the beam close to the electrodes but diverge as the beam is moved further away. The induced charge cloud signals also seem to increase linearly as the beam is moved away from the electrodes. The agreement between measurements and simulations indicates that the Monte-Carlo simulation can accurately model the channel response of the detector with the photon interactions close to the electrodes, which indicates that the unconnected electrodes introduce unwanted effects that need to be further explored. With the same Monte-Carlo simulation previously indicating a resolution of around with similar geometry, the results are promising that an ultra-high resolution detector is not far in the future.

Photon-Counting Detector CT for Liver Lesion Detection-Optimal Virtual Monoenergetic Energy for Different Simulated Patient Sizes and Radiation Doses.

The aim of this study was to evaluate the optimal energy level of virtual monoenergetic images (VMIs) from photon-counting detector computed tomography (CT) for the detection of liver lesions as a function of phantom size and radiation dose. An anthropomorphic abdominal phantom with liver parenchyma and lesions was imaged on a dual-source photon-counting detector CT at 120 kVp. Five hypoattenuating lesions with a lesion-to-background contrast difference of -30 HU and -45 HU and 3 hyperattenuating lesions with +30 HU and +90 HU were used. The lesion diameter was 5-10 mm. Rings of fat-equivalent material were added to emulate medium- or large-sized patients. The medium size was imaged at a volume CT dose index of 5, 2.5, and 1.25 mGy and the large size at 5 and 2.5 mGy, respectively. Each setup was imaged 10 times. For each setup, VMIs from 40 to 80 keV at 5 keV increments were reconstructed with quantum iterative reconstruction at a strength level of 4 (QIR-4). Lesion detectability was measured as area under the receiver operating curve (AUC) using a channelized Hotelling model observer with 10 dense differences of Gaussian channels. Overall, highest detectability was found at 65 and 70 keV for both hypoattenuating and hyperattenuating lesions in the medium and large phantom independent of radiation dose (AUC range, 0.91-1.0 for the medium and 0.94-0.99 for the large phantom, respectively). The lowest detectability was found at 40 keV irrespective of the radiation dose and phantom size (AUC range, 0.78-0.99). A more pronounced reduction in detectability was apparent at 40-50 keV as compared with 65-75 keV when radiation dose was decreased. At equal radiation dose, detection as a function of VMI energy differed stronger for the large size as compared with the medium-sized phantom (12% vs 6%). Detectability of hypoattenuating and hyperattenuating liver lesions differed between VMI energies for different phantom sizes and radiation doses. Virtual monoenergetic images at 65 and 70 keV yielded highest detectability independent of phantom size and radiation dose.