Photon-counting Detector CT Research Articles

Photon-Counting CT-Angiography to Assess Intracranial Stents and Flow Diverters in Comparison to Digital Subtraction Angiography.

Photon-Counting Detector CT is characterized by enhanced image post-processing capabilities. The diagnostic accuracy of PCD-CT angiography (PCD-CTA) in assessing intracranial stents (ICS) and flow diverters (FD) has yet to be compared with digital subtraction angiography (DSA). Retrospective analysis of all consecutive patients who underwent ICS or FD implantation between April 2023 and May 2024. Polyenergetic images, along with virtual monoenergetic imaging (VMI), pure lumen (PL) and iodine (IOD) reconstructions were assessed by three readers using a5-point Likert scale and defined regions of interest (ROIs). Ablinded analysis was performed to identify relevant lumen reduction. The diagnostic accuracy of PCD-CTA was compared to DSA by calculating the area under the receiver operating characteristic curve. Atotal of 18patients (mean age59 ± 13years; 14women) with 14implanted ICS and 10FD were analyzed. Across all pairwise comparisons, pooled VMI reconstructions demonstrated higher ratings and signal-to-noise ratios compared to IOD, PL and UHR reconstructions (p < 0.001 for all comparisons). In the pooled assessment of DSA of in-stent vessel lumen 18(11%) of the 162 vessel segments and 6(33%) of the 18patients presented relevant narrowing of the in-stent vessel lumen. The sensitivity of PCD-CTA for detecting stenosis was 100% (18of 18in-stent vessel segments), while specificity was 89% (128/144 in-stent vessel segments). All readers reported a100% negative predictive value (128/128 in-stent vessel segments). Photon-Counting Detector CT might provide areliable assessment of intracranial vessels following stent or flow diverter implantation comparable to DSA in many cases.

Learned high resolution energy-integrating detector CT angiography: Harnessing the power of ultra-high-resolution photon counting detector CT.

Coronary computed tomography angiography (cCTA) is a widely used noninvasive diagnostic exam to assess patients for coronary artery disease (CAD). However, the spatial resolution of most CT scanners is limited due to the use of energy-integrating detectors (EIDs). To develop a convolutional neural network (Improved LUMEN visualization through Artificial super-resoluTion imagEs (ILUMENATE)) informed by photon-counting-detector (PCD)-CT to improve EID-CT image resolution and determine its impact on cCTA. With IRB approval, 30 patients undergoing clinically indicated cCTA were scanned with EID-CT (SOMATOM Force, Siemens Healthineers, Forchheim, Germany) and subsequently with ultra-high-resolution (UHR) PCD-CT (NAEOTOM Alpha, Siemens Healthineers) on the same day. ILUMENATE was trained on eight patient PCD-CT datasets (67,890 patch pairs with 90% for training (61,101), 10% reserved for validation (6,789)) and applied to 22 unseen EID-CT cases. Spatial resolution was evaluated using line profiles and percent diameter stenosis quantified with a severity score assigned. Two experienced radiologists, blinded to image type, selected preferred series and scored images for overall quality, sharpness, and noise comparing original EID-CT and ILUMENATE output. Visual assessment and line profiles showed substantial resolution improvement with ILUMENATE. Percent diameter stenosis was significantly reduced (mean±standard deviation: 4.42%±4.82%) using ILUMENATE (p<0.001) with nine lesions shifting down in severity score. Readers preferred ILUMENATE images in 22/22 cases and scored ILUMENATE superiorly for overall quality, sharpness, and noise (p<0.05). ILUMENATE enhanced image resolution, resulting in improved overall image quality, reduced calcium blooming artifacts, and improved lumen visibility in cCTA exams performed using EID-CT. This could potentially allow for improved accessibility to UHR image quality, allowing for more accurate assessment of CAD.

Neuro applications of photon-counting CT.

Photon-counting detector CT, a recent advance in CT technology, has several advantages over conventional energy-integrating detector CT. These include increased spatial resolution, reduced image noise, increased soft-tissue and iodine contrast, lower radiation dose, and inherent spectral imaging. This article comments on recent literatures in neuroradiology covering the vessels, pituitary adenoma, temporal bone, and myelography while addressing certain issues and outlining future directions.

Comparison of radiation dose and image quality for abdominal CT exams using photon-counting and energy-integrating CT: A self-controlled study including optimized patient positioning.

Comparison of radiation dose and image quality for abdominal CT exams using photon-counting and energy-integrating CT: A self-controlled study including optimized patient positioning.

Assessment of metal artifacts from titanium wrist prostheses: photon-counting versus energy-integrating detector CT

BackgroundWe compared photon-counting detector computed tomography (PCD-CT) polyenergetic images, PCD-CT virtual monoenergetic images (VMI), and energy-integrating detector computed tomography (EID-CT) polyenergetic images regarding bone visualization and metal artifacts in patients with titanium wrist prostheses.MethodsAfter ethical approval, 15 patients were examined with PCD-CT and EID-CT. Polyenergetic images were reconstructed, as well as 130-keV VMI for PCD-CT. Five radiologists evaluated bone visualization, interpretability at metal-bone interface and metal artifacts using a 7-point ordinal scale. Streak artifacts and artifacts at the bone-metal interface were quantitatively assessed. Differences between image setups were analyzed using Friedman test and one-way ANOVA with post hoc tests.ResultsBone visualization was superior in PCD-CT polyenergetic images (median rating 6, range 3–7) compared with VMI (5, 3–7; p < 0.001) and EID-CT (5, 3–7; p = 0.018). Streak artifacts were more pronounced with PCD-CT polyenergetic images (4, 3–6) compared with EID-CT (5, 4–6; p = 0.003) and PCD-CT VMI (5, 3–7; p = 0.002), with quantitative results showing least streak artifacts in PCD-CT VMI, followed by EID-CT and PCD-CT polyenergetic images (50 ± 7%, 70 ± 6%, and 79 ± 5%, respectively; p < 0.001). Interpretability at bone-metal interface was better with PCD-CT polyenergetic images (5, 2–7; p = 0.045) and EID-CT (5, 3–6; p = 0.018) compared with PCD-CT VMI (4, 2–6), without quantitative differences.ConclusionStreak artifacts from titanium wrist prostheses were reduced using 130-keV PCD-CT VMI, while bone visualization was highest using PCD-CT polyenergetic images.Relevance statementIn patients with wrist implants, photon-counting detector CT allows for effective metal artifact reduction using virtual monoenergetic images and improved bone visualization using polyenergetic images. As polyenergetic images and VMI have different advantages, access to both image setups may benefit diagnostic evaluation.Key PointsVirtual monoenergetic images (VMI) presented a substantial reduction of metal streak artifacts.Polyenergetic images exhibited better image quality for bone imaging compared with VMI.A combination of image reconstructions should be preferred depending on the diagnostic task.Graphical

Accuracy of photon-counting detector CT-based iodine maps for myocardial late enhancement detection.

To evaluate the diagnostic accuracy of iodine maps from photon-counting detector (PCD) CT in detecting myocardial late enhancement compared to late gadolinium enhancement (LGE)-MRI. In this retrospective analysis of a prospective cohort, patients underwent cardiac MRI with LGE followed by late iodine enhancement (LIE)-CT using dual-source PCD-CT. LIE-CT was performed 5 min post-intravenous administration of 100 mL iopromide (370 mg I/mL) using an ECG-triggered sequential protocol with full spectral capabilities (120 kVp, 144 × 0.4 mm collimation). Iodine maps were reconstructed with a quantitative kernel (Qr40) and iterative reconstruction. Two radiologists independently rated image quality on a four-point scale (1: "poor" to 4: "excellent"). Diagnostic performance was assessed per-patient and per-segment using LGE-MRI as reference, and inter-reader agreement was analyzed using Cohen's kappa (κ). The study included 27 patients (52% female; mean age 52.9 ± 17.2 years). Twelve (44%) had positive LGE, with 87/459 (19%) myocardial segments affected. Image quality was rated as good, with no significant differences between readers (median 3 [2-4] vs 3 [3-4]; p = 0.058). Per-patient sensitivities were 100% and 91.7%, specificities 73.3% and 80.0%, and accuracies 85.2%, respectively. Per-segment sensitivities, specificities, and accuracies were 74.7%, 94.9%, and 91.1% (reader 1) and 66.7%, 96.4%, and 90.7% (reader 2). Substantial inter-reader agreement was observed (κ = 0.70 per patient, 0.63 per segment). Iodine maps from PCD-CT demonstrate high diagnostic accuracy for assessing myocardial late enhancement, with substantial inter-reader agreement. These findings suggest that PCD-CT may serve as a valuable alternative to LGE-MRI. Question Can PCD CT iodine maps detect myocardial late enhancement with accuracy comparable to LGE-MRI? Findings PCD-CT iodine maps achieved high accuracy (85.2% per patient, > 90% per segment) with substantial inter-reader agreement. Clinical relevance PCD-CT iodine maps offer a valuable alternative to LGE-MRI for myocardial late enhancement assessment, especially for patients with contraindications to MRI.

Improving accuracy in assessing osseointegration in small animal bone using specimen-specific additively-manufactured fixtures based on clinical CT imaging.

Improving accuracy in assessing osseointegration in small animal bone using specimen-specific additively-manufactured fixtures based on clinical CT imaging.

Visualization of the middle meningeal artery on photon-counting detector CT: Comparison with energy-integrating detector CT

Visualization of the middle meningeal artery on photon-counting detector CT: Comparison with energy-integrating detector CT

Semiquantitative metrics of coronary artery disease burden: Intra-individual comparison between ultrahigh-resolution photon-counting detector CT and energy-integrating detector CT.

Semiquantitative metrics of coronary artery disease burden: Intra-individual comparison between ultrahigh-resolution photon-counting detector CT and energy-integrating detector CT.

Addendum to: Intra-individual comparison of coronary artery stenosis measurements between energy-integrating detector CT and photon-counting detector CT

Addendum to: Intra-individual comparison of coronary artery stenosis measurements between energy-integrating detector CT and photon-counting detector CT

Photon-Counting Chest CT at Radiography-Comparable Dose Levels: Impact on Opportunistic Visual and Semiautomated Coronary Calcium Quantification.

The introduction of photon-counting detector computed tomography (PCCT) has allowed for significant dose reductions compared to energy-integrating-detector CT, making it particularly relevant for applications such as lung cancer screening. Coronary artery calcification is an important incidental finding in lung cancer screening, warranting attention in this context. This study aims to assess the impact of dose reduction to levels comparable to that of a chest radiography on opportunistic evaluation of coronary artery calcification on PCCTs of the chest. Sixty-eight out of 115 patients with age >45 years and body mass index ≤30 kg/m2 undergoing noncontrast low- and chest-radiography-comparable-dose PCCT in the same session were included. Scans were performed at 100 kVp with image quality settings 12 (low-dose) and 2 (radiography-comparable-dose). Visual calcium scoring was conducted by 2 readers using 2 scoring approaches (CAD-RADS 2.0 and Shemesh). Semiautomated quantitative analysis was performed using commercially available software. Image quality was evaluated using 5-point Likert scales. Sixty-eight patients (65.9 ± 8.6 years; 49 men) were subjected to evaluation. CTDI was lower for radiography-dose scans (0.11 mGy vs 0.68 mGy; P < 0.001). Image quality was found to be inferior for radiography-dose scans (4.01 vs 2.03; P < 0.001). In both visual scoring approaches, coronary calcification was scored significantly lower in radiography-dose scans (P < 0.001 for both) with almost perfect reader agreement (CAD-RADS score Cohen's kappa =0.82; Shemesh score Cohen's kappa =0.81), most importantly reclassification from mild to absent occurred for CAD-RADS score in 31%/21% of cases and for Shemesh score in 23%/15% of cases (reader 1/reader 2). Semiautomated assessment showed no significant differences between low and radiography dose (P = 0.121). Strong correlation between scores (Pearson's r = 0.98, P < 0.001) with good agreement (Cohen's kappa =0.61) was found. Coronary artery calcifications are underestimated on radiography-dose PCCT visually, whereas semiautomatic analysis provides more robust results. Visual underestimation of coronary artery calcification in low-dose imaging is further amplified with the additional dose reduction to radiography-comparable dose levels, indicating that while estimation of high cardiovascular risk is feasible, exclusion of such risk is not possible.

"Photon Counting Detector Computed Tomography in Pediatric Imaging: A Review of current literature and future directions".

The benefits of photon counting detector (PCD) computed tomography (CT) include improved spatial resolution, increased radiation dose efficiency, and the elimination of electronic noise. Unlike traditional energy-integrating-detector (EID) CT systems, photon counting detectors have inherent spectral capabilities, which support "always-on" dual energy and multi-energy imaging acquisition. PCD-CT directly converts X-ray photons into electrical signals and captures their individual energy levels. Current commercially available PCD-CT scanners, all from one manufacturer, include two models that incorporate dual-source geometry. This innovation is particularly advantageous for pediatric imaging by enabling rapid scans that reduce motion artifact and therefore the need for sedation and can now be combined in the current model with multi-energy imaging or ultra-high-resolution acquisition. This review article explores how the technical benefits of PCD CT improve the diagnostic quality of images and opens the field of pediatric radiology up to future opportunities for research and new applications.

Dual-Source Dual-Energy Imaging Using Photon-Counting Detector CT for Bone Edema Detection: Leveraging Tin Prefiltration for Improved Spectral Performance.

The aims of the study were to evaluate the spectral performance of an investigational dual-source (DS) scan mode using a tin (Sn) filter on the B-subsystem of a clinical photon-counting detector (PCD) CT system and to demonstrate improved material decomposition performance using clinical examples of bone imaging tasks. Calcium inserts (Ca 100, 200 and 300 mg/cc) were placed in water phantoms (30-, 40-, and 50-cm lateral diameter) and scanned on clinical PCD-CT (NAEOTOM Alpha, Siemens) using DS spectral scan mode (QuantumPeak). Two tube potential configurations (70/Sn150 kV and 90/Sn150 kV) were used to scan the phantoms (11 mGy to 41 mGy volume CT dose index). The phantoms were also scanned using the single-source (SS) PCD-CT scan mode at 120 kV and 140 kV tube potential, and on a DS energy-integrating detector (EID) CT (SOMATOM Force, Siemens) for quantitative comparison. CT images (from SS-PCD-CT, DS-PCD-CT, and DS-EID-CT) were reconstructed using a quantitative kernel (Qr40) at a 2-mm section thickness using iterative reconstruction strength 1. Spectral separation was quantified using the dual-energy ratio (DER) of Ca inserts and using mean absolute percent error (MAPE) of Ca mass density obtained from Ca/water material decomposition. To demonstrate clinical feasibility, 4 patients were scanned using DS-PCD-CT under an institutional review board-approved study. Bone edema maps were reconstructed from DS-PCD-CT and compared with the corresponding clinical imaging exam of the same patients (MRI or DS-EID-CT). DS-PCD-CT at 70/Sn150 kV for Ca 100 mg/cc showed the highest mean DER (2.49 and 2.56 at 30 and 40 cm, respectively) among all scan configurations. For the 50-cm phantom at Ca 100 mg/cc, DS-PCD-CT at 90/Sn150 kV showed highest mean DER (1.88), followed by DS-EID-CT at 90/Sn 150 kV (1.87) and SS-PCD-CT at 140 kV (1.78). The MAPE values for DS-PCD-CT were consistently lower across all phantom sizes (MAPE max. of 1.44%) compared to SS-PCD-CT (MAPE max. 3.97%) and DS-EID-CT (MAPE max. 3.68%). Qualitatively, patient images illustrated bone edema depiction on DS-PCD-CT comparable to clinical MR images, and more precise edema depiction compared to DS-EID-CT images at the site of fractures and intramedullary lesions, and with fewer artifacts. DS-PCD-CT showed superior spectral performance for calcium imaging tasks compared to SS-PCD-CT and DS-EID-CT.

Assessing anemia in stroke patients through virtual non-contrast imaging with photon-counting detector CT: validation on supra-aortic vessel CT-Angiography.

Anemia is a common comorbidity in stroke patients, traditionally detected via blood tests. This study evaluates the feasibility of using virtual non-contrast (VNC) imaging from photon counting detector-CT (PCD-CT) angiography to detect anemia and identifies the optimal anatomical site for assessment. In this retrospective study of 80 patients undergoing PCD-CT angiography of supra-aortic vessels, VNC series were analyzed at various anatomical sites, including the jugular veins, aorta, and cerebral sinuses. Correlations between serum hemoglobin (Hb) levels and VNC Hounsfield Unit (HU) values were assessed using Pearson's coefficients. Linear regression and ROC analysis evaluated diagnostic performance.ResultsThe jugular veins showed the strongest correlation between VNC HU values and Hb levels (R2 = 0.49, p < 0.001), with weaker correlations in arterial vessels like the aorta (R2 = 0.11, p < 0.001). ROC analysis of jugular vein VNC values yielded an AUC of 0.79 for anemia detection. Correlation strength declined with longer intervals between imaging and blood tests, suggesting temporal Hb variability. VNC imaging in CT angiography is a feasible method for detecting anemia, with the jugular veins providing the most reliable site for assessment. VNC imaging could be a valuable alternative when blood tests are delayed or unavailable.

Simple cystic lesions of the pancreas: image quality and diagnostic accuracy of photon-counting detector computed tomography.

To evaluate image quality and diagnostic accuracy of photon-counting detector (PCD) CT for the detection of pancreatic cystic lesions (PCLs) compared to energy-integrating detector (EID) CT with MRI serving as reference standard. We included consecutive patients who underwent contrast-enhanced PCD-CT of the abdomen and for whom an additional abdominal EID-CT was available. Multiparametric MRI served as the reference standard. CT images were assessed for the presence of PCLs by three radiologists independently in a blinded reading. Image quality, lesion conspicuity, and diagnostic confidence were rated on a 5-point Likert scale (5 = excellent). The coefficient of variation (CV) and the density difference between PCLs and visually normal pancreatic parenchyma were calculated as quantitative imaging measures. Radiation dose was assessed using CTDIvol [mGy]. Among 106 included patients (age 62.7 ± 12.6years; 45 [42.5%] male), 46 had MRI-confirmed cystic lesions (mean size 8.7 ± 7.4mm; range 2-45mm). Diagnostic accuracy for PCLs was significantly higher for PCD-CT vs. EID-CT (area under the curve: 0.81 vs. 0.74; p = 0.002; sensitivity: 76.8% vs. 59.4%). Image quality, lesion conspicuity, and diagnostic confidence were rated superior for PCD-CT vs. EID-CT (all p < 0.001). Quantitative analyses revealed a significantly lower CV (0.19 vs. 0.24; p = 0.002) and a higher density difference (94.1 HU vs. 76.6 HU p < 0.001) between PCLs and visually normal pancreatic parenchyma at lower radiation doses (7.13 vs. 8.68mGy; p < 0.001) for PCD-CT vs. EID-CT. PCD-CT provided significantly higher diagnostic accuracy and superior image quality for the detection of PCLs compared to conventional EID-CT at lower radiation dose.

Lung microvasculopathy in chronic thromboembolic pulmonary hypertension: high-resolution findings with photon-counting detector CT in 29 patients.

To evaluate CT findings suggestive of lung microvasculopathy in patients with chronic thromboembolic pulmonary hypertension (CTEPH). Twenty-nine patients were scanned with high-spatial resolution on a photon-counting detector (PCD)-CT unit. A maximum of three pairs per patient, each composed of hyper- and hypo-attenuating areas of mosaic perfusion, were selected. Comparative analysis of the 86 selected pairs showed: (a) a higher frequency of ill-defined micronodules (p = 0.008), lobular ground-glass opacities (p = 0.01) and haziness (p = 0.003) in hypoattenuated areas; (b) there was no significant difference in the frequency of neovascularity (p = 0.43). Similar trends were observed in hypoattenuating areas of the 66 pairs studied in the 22 patients with central and peripheral CTEPH; an absence of ill-defined micronodules, lobular ground-glass opacities, and haziness in hyperattenuating areas was noticed in the 20 pairs studied in the 7 patients with peripheral CTEPH. Patients with a mean pulmonary artery pressure ≤ 42 mmHg (i.e., the median value of mean pulmonary artery pressure) had 45 pairs compared, showing a higher frequency of ill-defined micronodules (p = 0.003) and haziness (p < 0.001) in hypoattenuated areas, together with a higher frequency of subpleural systemic-to-pulmonary anastomoses (p = 0.02). There were no statistical differences in the frequency of CT findings between hypo- and hyper-attenuating areas in the 41 pairs of patients with a mean pulmonary artery pressure > 42 mm Hg. CT features suggestive of microvasculopathy were more frequent in areas of hypoperfusion, with a trend toward homogenization of CT findings in patients with severe PH. Question Lung microvascular lesions play a crucial role in the origin of residual pulmonary hypertension after successful thromboendarterectomy, currently beyond the scope of imaging. Findings The expected morphological abnormalities at the level of distal pulmonary circulation in CTEPH were found to be depictable in each zone of mosaic perfusion. Clinical relevance This study suggests that the high-spatial resolution of PCD-CT has the capability of approaching the complex pathophysiology of small-vessel disease in CTEPH, providing important information prior to therapeutic decisions.

Paediatric high-pitch lung imaging with photon-counting detector computed tomography: a dose reduction phantom study.

Photon-counting detector computed tomography (PCD-CT) can reduce radiation dose in paediatric lung imaging. The aim of this study was to determine the lowest radiation dose maintaining adequate image quality for high-pitch lung imaging using a PCD-CT in a chest phantom replicating the characteristics of a 5-year-old child. The phantom was imaged on a dual-source PCD-CT with five different volume CT dose indices (CTDIvol): 0.45 mGy, 0.30 mGy, 0.15 mGy, 0.07 mGy, and 0.01 mGy. Scans were acquired with Sn100 kV in standard and ultra-high resolution modes. Polychromatic images were reconstructed with a 1-mm slice thickness, lung kernel Bl60, without quantum iterative reconstruction and with quantum iterative reconstruction at strengths 2 and 4. Two paediatric radiologists rated reconstructions subjectively, defining adequate image quality as the visibility of small peripheral structures. Objective evaluation included global noise index and global signal-to-noise ratio index. Exposure times were 0.42 s and 0.84 s for standard and ultra-high resolution modes, respectively. Subjective assessments showed no significant differences across scan modes or quantum iterative reconstruction strengths for both readers at all doses (all, P > 0.05). Scans at 0.07 mGy with quantum iterative reconstruction 4 were deemed to maintain adequate image quality at the lowest dose. Global noise index was always lower and global signal-to-noise ratio index always higher in ultra-high resolution compared with standard mode, underscoring noise reduction achieved via ultra-high resolution mode's small pixel effect. PCD-CT enables high-pitch lung imaging while maintaining adequate image quality at a radiation dose as low as 0.07 mGy, with quantum iterative reconstruction 4, in a paediatric phantom representing a 5-year-old child.

Single-Energy, Dual-Energy, and Photon-Counting Computed Tomography of the Liver: Current Development and Clinical Utility for the Assessment of Focal Liver Lesions.

Advancements in computed tomography (CT) technology, particularly the emergence of dual-energy CT (DE-CT) and photon-counting detector CT (PCD-CT), can improve detection, characterization, and treatment monitoring of focal liver lesions. DE-CT, through its ability to differentiate tissues with similar densities and produce diverse datasets, has enhanced lesion visibility and diagnostic precision. PCD-CT further advances imaging with superior spatial resolution and material decomposition capabilities, offering potential for complex diagnostic scenarios. This review aimed to highlight the role of CT in hepatic imaging and its application to focal liver lesions.DE-CT improves lesion detectability using low-energy virtual monochromatic images, which enhance iodine contrast and reduce radiation and contrast agent doses. It also facilitates treatment response evaluation after locoregional therapies for hepatocellular carcinoma by quantifying biomarkers, such as the extracellular volume fraction. This review underscores the transformative impact of DE-CT and PCD-CT on liver imaging, emphasizing their complementary roles alongside magnetic resonance imaging. These innovations have paved the way for more precise diagnostics, improved treatment planning, and enhanced patient outcomes in the management of liver diseases.

Use of Photon-Counting Detector CT to Visualize Liver-Specific Gadolinium-Based Contrast Agents: A Phantom Study.

BACKGROUND. The low clinically approved doses of gadolinium-based contrast agents (GBCAs) do not generate sufficient enhancement on CT for diagnostic purposes. Photon-counting detector (PCD) CT offers improved spectral resolution and could potentially enable visualization of hepatocyte-specific GBCAs, given their associated high gadolinium concentrations within hepatocytes. OBJECTIVE. The purpose of this study was to investigate the potential of gadoxetate disodium in combination with PCD CT and low-energy virtual monoenergetic imaging (VMI) reconstructions to achieve an increase in attenuation in a phantom. METHODS. A series of solutions was prepared of diluted gadoxetate disodium (concentrations of 0.250-2.5 μmol/mL, corresponding with doses of 25-200 μmol/kg). These solutions, along with deionized water, were evaluated in an anthropomorphic abdominal phantom using a clinical PCD CT scanner; VMI reconstructions at 40, 50, 60, and 70 keV and virtual noncontrast (VNC) imaging reconstructions were generated. Attenuation measurements were obtained; a linear regression model combined these values with previously reported in vivo data to estimate hepatic enhancement and CNR across doses. RESULTS. Attenuation increased with increasing concentration at a given energy level and with decreasing energy level for a given concentration; VNC images had the lowest attenuation. The maximum attenuation reached in the abdominal phantom was 45.2 HU for a concentration of 2.5 μmol/mL at 40 keV. A concentration of 0.25 μmol/mL had attenuation at 40 keV of 13.0 HU. The model yielded estimated in vivo hepatic enhancement at 40 keV of 4.9 HU for a dose of 25 μmol/kg, 19.9 HU for 100 μmol/kg, and 30.8 HU for 200 μmol/kg; corresponding CNRs were 0.13, 0.52, and 0.81, respectively. CONCLUSION. The combination of gadoxetate disodium and PCD CT could theoretically allow appreciable hepatic enhancement at a 200-μmol/kg dose; such effect was not observed for the clinically approved 25-μmol/kg dose. CLINICAL IMPACT. PCD CT achieved attenuation increases for gadoxetate disodium at considerably lower doses than previously documented for CT of GBCAs, albeit at approximately eight times greater than clinical doses, which were thus too high for clinical use. Additional research exploiting PCD CT technology could seek to reduce further doses required for sufficient visualization into a clinically feasible range, to potentially allow CT using a liver-specific agent.

Increased diagnostic accuracy and better morphology characterization of unruptured intracranial aneurysm by ultra-high-resolution photon-counting detector CT angiography

BackgroundAccurate detection and morphology evaluation of unruptured intracranial aneurysms (UIAs) are essential for patient management. This study aimed to assess the efficacy of ultra-high-resolution (UHR) photon-counting detector-CT angiography (PCD-CTA) in...