Evaluation of soft-plaque stenoses in coronary artery stents using conventional and monoenergetic images: first in-vitro experience and comparison of two different dual-energy techniques

Background: Non-invasive coronary imaging after stent placement remains challenging. Favorable results for dual-energy computed tomography (DECT) derived monoenergetic (MonoE) images have been reported for this purpose. Nowadays, there are different dual-energy techniques available, each with specific advantages and disadvantages. However, for the evaluation of coronaries after stent implantation there is no systematic comparison between different dual-energy techniques. Therefore, the aim of our study was to compare two widely used DECT systems using an in-stent restenosis (ISR) phantom setup. Methods: Soft-plaque-like stenoses (similar to 50% of lumen) were inserted into ten coronary stents embedded in contrast-filled vessel phantoms. A dual-source CT (DSCT) and a dual-layer CT (DLCI) with comparable acquisition and reconstruction parameters were used. Conventional polyenergetic (PolyE) and MonoE images with 9 different levels (40-120 keV) were calculated. ISR assessability was evaluated by subjective scoring using a 5-point scale and by the following quantitative parameters: image noise, visible lumen diameter (VLD) and ISR contrast-to-noise ratio (CNR). Results: A non-significant trend towards larger VLD in DLCT images was observed. Highest noise was found in low-keV MonoE with significantly higher values for DSCT than for DLCT. Conversely, noise was significantly lower for DSCT at higher-keV MonoE. Peak ISR CNR values were found at low-keV MonoE with no significant difference between both systems. However, for PolyE and mid-energy MonoE, CNRs were significantly higher for DSCT. Subjective image quality was significantly better for PolyE and low-keV MonoE than for high-keV MonoE, also without significant difference between both systems. Conclusions: Conspicuity of ISR benefits from DECT. Peak CNRs were comparable for both DECT systems and low-keV MonoE offered the highest CNR values and best subjective image quality. In contrast, high-keV MonoF, cannot be recommended for stent evaluation due to poor CNR values and therefore significantly limited visualization of stenoses

Venous-phase chest CT with reduced contrast medium dose: Utilization of spectral low keV monoenergetic images improves image quality

Purpose: Intravenous contrast administration is crucial in many CT examinations but also poses a potential risk to the patient. Monoenergetic images (MonoE) of dual-energy CT systems can virtually increase iodine attenuation and might improve image quality (IQ) if contrast dose is reduced. In this study, we investigated the influence of MonoE on lymph node (LN) delineation and IQ in chest CT examinations with significantly reduced contrast dose (50 %) of a novel dual-layer CT (DLCT). Method: 30 patients with clinically indicated reduced contrast dose underwent venous-phase chest DLCT scans. Conventional polyenergetic (PolyE) and MonoE images at 40 keV were calculated. The contrast difference of hilar lymph nodes (LN-CD) to the adjacent right pulmonary artery, their signal-to-noise (SNR) and contrast-tonoise-ratio (CNR) were determined. Subjective IQ was evaluated by 2 readers with respect to LN delineation and overall contrast enhancement (CE) using a 5-point-Likert-scale. Results: LN-CD, SNR and CNR were significantly higher in MonoE than in PolyE images (LN-CD 92.3 +/- 37.9 vs. 33.1 +/- 14.5 HU, SNR 8.4 +/- 3.4 vs. 4.0 +/- 1.2, CNR 9.2 +/- 6.3 vs. 2.6 +/- 1.5; all p < 0.01). The LN delineation (3.7 +/- 0.9 vs.1.8 +/- 0.7; p < 0.01) and the CE (3.9 +/- 0.7 vs. 2.3 +/- 0.7; p < 0.01) were rated significantly better for MonoE than for PolyE images. There was no MonoE examination classified as non-diagnostic. Conclusions: Subjective and objective IQ parameters can be significantly improved for venous-phase chest CT examinations with reduced contrast doses by utilization of low-keV MonoE reconstructions. All MonoE images provided sufficient overall CE and therefore reduced contrast doses might be considered in a wider range of DLCT examinations and patients

Prediction of anemia on enhanced computed tomography of the thorax using virtual non-contrast reconstructions

To determine if anemia can be predicted on enhanced computed tomography (CT) examinations of the thorax using virtual non-contrast (VNC) images, in order to support clinicians especially in diagnosing primary asymptomatic patients in daily routine. In this monocentric study, 100 consecutive patients (50 with proven anemia), who underwent a contrast-enhanced CT examination of the thorax due to various indications were included. Attenuation was measured in the descending thoracic aorta, the intraventricular septum, and the left ventricle cavity both in the conventional contrast-enhanced and in the VNC images. Two experienced radiologists annotated the delineation of a dense interventricular septum or a hyperattenuating aortic wall sign for all patients. Hemoglobin levels were then correlated with the measured attenuation values, as well as the visualization of the aortic wall or interventricular septum. Good correlation was shown between hemoglobin levels and CT attenuation values of the left ventricular cavity (r = .59), aorta (r = .56), and ratio between left ventricular cavity and the intraventricular septum (r = .57). Receiver operating characteristic curve revealed <= 36.5 hounsfield units (left ventricular cavity) as the threshold for diagnosing anemia. Predicting anemia by visualization of a hyperattenuating aortic wall or a dense interventricular septum yielded a specificity of 98% and 92%, respectively. Predicting anemia on enhanced CT examinations using VNC is feasible. A threshold value of <= 36.5 hounsfield units (left ventricular cavity) best defines anemia. Aortic wall or interventricular septum visualization on VNC is a specific anemia indicator

Fourth update on CT angiography of coronary stents: invitro evaluation of 24 novel stent types

Background: Non-invasive evaluation of coronary stent patency by coronary computed tomography angiography (cCTA) remains challenging. Multiple studies showed that CT technology but also individual stent design strongly influence the assessability of coronary stents by cCTA. Purpose: To expand the available data on cCTA characteristics of coronary stents by 24 novel types to help interpreting examinations of patients after stent placement and selecting which stents are suitable for assessment by cCTA. Material and Methods: Twenty-four novel coronary stents (17 cobalt-chromium, six stainless-steel, one platinum-chromium) were examined in a coronary phantom. Standard cCTA parameters with stent-specific algorithms were used. Image quality was quantified for each stent using established parameters (in-stent attenuation alteration and visible lumen diameter). Results: Most stents (n=14) showed lumen visibilities of 45-55%. No severe restriction of lumen visibility (>60%) was found. The majority of stents (n=13) caused only small intraluminal attenuation deviations and no severe alterations (>20%) were found. When grouped by manufacturing material, no significant differences were found between cobalt-chromium and stainless-steel with identical mean visible diameters (1.520.17mm vs. 1.52 +/- 0.13mm) and comparable attenuation alterations (35.04 +/- 16.56 HU vs. 21.25 +/- 14.60 HU). The only platinum-chromium stent showed a smaller visible diameter (1.23mm) and higher attenuation alteration (41.70 HU), but was also deemed to be assessable by cCTA. Conclusion: All 24 novel evaluated stents are eligible for non-invasive evaluation by cCTA without significant differences between cobalt-chromium and stainless-steel stents. This updated catalogue of CT appearances of current coronary stents may serve as reference when taking care of patients with stents in need of coronary imaging

Fibrin sheaths in central venous port catheters: treatment with low-dose, single injection of urokinase on an outpatient basis

Purpose: Evaluation of the efficacy of single-shot, low-dose urokinase administration for the treatment of port catheter-associated fibrin sheaths. Methods: Forty-six patients were retrospectively evaluated for 54 episodes of port catheter dysfunction. The presence of a fibrin sheath was detected by angiographic contrast examinations. On an outpatient basis, patients subsequently received thrombolysis consisting of a single injection of urokinase (15.000 IU in 1.5 mL normal saline) through the port system. A second attempt was made in cases of treatment failure. Patients were followed up for technical success, complications and long-term outcome. Results: Port dysfunction occurred at a median of 117 days after implantation (range: 7-825 days). The technical success after first port dysfunction by thrombolysis was 87% (40/46); thereof, initial thrombolysis was effective in 78% (36/46). Nine patients (20%) received a second dose of urokinase after previous treatment failure. Follow-up was available for 26 of 40 patients after successful thrombolysis. In 8 of these, rethrombosis occurred after a median of 98 days (range: 21-354 days), whereby rethrombolysis was effective in 5 of 7 (63%) patients. The overall success of all thrombolyses performed was 70% (45/64). No procedure-related technical or clinical complications occurred. After first favorable thrombolysis, a Kaplan-Meier analysis yielded a 30-, 90- and 180-day probability of patency of 96%, 87% and 81%. Conclusion: Thrombolytic therapy on an outpatient basis appears to be a safe and efficient. Three-month patency rates are comparable to more invasive treatment options, including catheter exchange over a guide wire and percutaneous fibrin sheath stripping

Influence of spectral detector CT based monoenergetic images on the computer-aided detection of pulmonary artery embolism

Objective: To evaluate the influence of monoenergetic reconstructions using a spectral detector CT (SDCT) on the computer aided detection (CAD) of pulmonary artery embolism (PAE) on CT pulmonary angiography (CTPA) and CT in venous contrast phase (CTV). Material and Methods: A retrospective data base search identified 15 patients with CTPA and 18 patients with CTV and diagnosis of PAE. For these patients, monoenergetic (monoE) images at different energy levels or with a fixed attenuation in the pulmonary artery were generated and independently analyzed using a commercially available computer aided detection (CAD) tool. Attenuation in the pulmonary artery and in the embolus was measured. Results: For CTPA and CTV, in monoenergetic images the difference in attenuation between vessel and embolus was significantly higher than in conventional images. In CTPA the detection rate was highest in the > 500 HU monoE images with 67,9% detected emboli and 93,3% of patients correctly identified as having PAE. At the same time the false positive rate could be significantly reduced by using monoE images compared to conventional images. Detection rates for CTV were lower than in CTPA but were raised significantly by monoE reconstructions. Conclusions: The combination of SDCT and CAD improves the diagnostic accuracy of CAD and enables CAD interpretation of CTV

Knowledge-based iterative reconstructions for imaging of coronary artery stents: first in-vitro experience and comparison of different radiation dose levels and kernel settings

Background: Advanced knowledge-based iterative model reconstructions (IMR) became recently available for routine computed tomography (CT). Using more realistic physical models it promises improved image quality and potential radiation dose reductions, both possibly beneficial for non-invasive assessment of coronary stents. Purpose: To evaluate the influence of different IMR settings at different radiation doses on stent lumen visualization in comparison to filtered back projection (FBP) and first-generation (hybrid) iterative reconstruction (HIR). Material and Methods: Ten coronary stents in a coronary phantom were examined at four different dose settings (120 kV/125 mAs, 120 kV/75 mAs, 100 kV/125 mAs, 100 kV/75 mAs). Images were reconstructed with stent-specific FBP and HIR kernels and with IMR using CardiacRoutine (CR) and CardiacSharp (CS) settings at three different iteration levels. Image quality was evaluated using established parameters: image noise; in-stent attenuation difference; and visible lumen diameter. Results: Image noise was significantly lower in IMR than in corresponding HIR and FBP images. At lower radiation doses, image noise increased significantly except with IMR CR3 and IMR CS3. Visible lumen diameters were significantly larger with IMR CS than with FBP, HIR, and IMR CR. IMR CR showed the smallest attenuation difference, while attenuation was artificially decreased extensively with IMR CS. FBP and HIR showed moderately increased in-stent attenuations. No relevant influence of used radiation doses on visible lumen diameters or attenuation differences was found. Conclusion: IMR CR reduces image noise significantly while offering comparable stent-specific image quality in comparison to FBP and HIR and therefore potentially facilitates stent lumen delineation. Utilization of IMR CS for stent evaluation seems unfavorable due to artificial image alterations

Poly-energetic and virtual mono-energetic images from a novel dual-layer spectral detector CT: optimization of window settings is crucial to improve subjective image quality in abdominal CT angiographies

Purpose: We aimed to determine optimal window settings for poly-energetic (PolyE) and virtual mono-energetic images (MonoE) derived from abdominal angiographic studies on a novel dual-layer spectral detector CT (SDCT) system. Methods: From 50 patients, SDCT datasets PolyE and MonoE at 70 and 40 keV levels were reconstructed and best individual window width and level (BI-W/L) manually assessed. Through regression analysis, the so-called optimized individual (OI-W/L) values were obtained. Subjective image quality parameters and vessel diameters were measured to determine influences of different W/L settings. Results: Image noise was lower and attenuation and contrast-to-noise ratio were higher in MonoE compared to PolyE (all p <= 0.002). Mean BI-W/L values for PolyE, 70, and 40 keV were 637/284, 647/291, and 1568/691, respectively. Mean OI-W/L values were 631/276, 628/286, and 1516/667, respectively. Compared to standard settings, all adjusted W/L settings varied significantly and yielded higher subjective scoring. No between-group differences were found between manually adjusted and mathematically calculated W/L settings. Conclusion: PolyE and MonoE from abdominal angiographic SDCT studies require appropriate W/L settings especially at low energy reconstruction levels. Individual adjustment reaches the best image quality but is time consuming. From our data, predefined W/L settings of 640/280 (PolyE/MonoE 70 keV) and 1570/690 (MonoE 40 keV) as a non-individualized starting point for abdominal angiographic studies from the novel SDCT system are suggested

Ultrasound-guided lymphangiography and interventional embolization of chylous leaks following esophagectomy

Postoperative chylothorax is a serious complication after transthoracic esophagectomy, and is associated with major morbidity due to dehydration and malnutrition. For patients with high-output fistula, re-thoracotomy with ligation of the thoracic duct is the treatment of choice. Radiologic interventional management is an innovative procedure that has the potential to replace surgery in the treatment algorithm