Dual-Energy and Photon-Counting Computed Tomography in Vascular Applications-Technical Background and Post-Processing Techniques.

The field of computed tomography (CT), which is a basic diagnostic tool in clinical practice, has recently undergone rapid technological advances. These include the evolution of dual-energy CT (DECT) and development of photon-counting computed tomography (PCCT). DECT enables the acquisition of CT images at two different energy spectra, which allows for the differentiation of certain materials, mainly calcium and iodine. PCCT is a recent technology that enables a scanner to quantify the energy of each photon gathered by the detector. This method gives the possibility to decrease the radiation dose and increase the spatial and temporal resolutions of scans. Both of these techniques have found a wide range of applications in radiology, including vascular studies. In this narrative review, the authors present the principles of DECT and PCCT, outline their advantages and drawbacks, and briefly discuss the application of these methods in vascular radiology.

High On-Treatment Platelet Reactivity Affects the Extent of Ischemic Lesions in Stroke Patients Due to Large-Vessel Disease.

BACKGROUND: Excessive platelet activation and aggregation plays an important role in the pathogenesis of ischemic stroke. Correlation between platelet reactivity and ischemic lesions in the brain shows contradictory results and there are not enough data about the potential role of stroke etiology and its relationships with chronic lesions. The aim of this study is to assess the relationship between platelet reactivity and the extent of ischemic lesions with the particular role of etiopathogenesis. METHODS: The study involved 69 patients with ischemic stroke, including 20 patients with large-vessel disease and 49 patients with small-vessel disease. Evaluation of platelet reactivity was performed within 24 h after the onset of stroke using two aggregometric methods (impedance and optical), while ischemic volume measurement in the brain was performed using magnetic resonance imaging (in diffusion-weighted imaging (DWI) and fluid-attenuated inversion recovery (FLAIR) sequences) at day 2-5 after the onset of stroke. RESULTS: In the large-vessel disease subgroup, a correlation was found between platelet reactivity and acute ischemic focus volume (correlation coefficient (R) = 0.6858 and p = 0.0068 for DWI; R = 0.6064 and p = 0.0215 for FLAIR). Aspirin-resistant subjects were significantly more likely to have a large ischemic focus (Odds Ratio (OR) = 45.00, 95% Confidence Interval (CI) = 1.49-135.36, p = 0.0285 for DWI; OR = 28.00, 95% CI = 1.35-58.59, p = 0.0312 for FLAIR) than aspirin-sensitive subjects with large-vessel disease. CONCLUSION: In patients with ischemic stroke due to large-vessel disease, high on-treatment platelet reactivity affects the extent of acute and chronic ischemic lesions.

Improved imaging of colorectal liver metastases using single-source, fast kVp-switching, dual-energy CT: preliminary results.

PURPOSE: Computed tomography remains the first-choice modality for assessment of colorectal cancer liver metastases (CRLM). Dual-energy computed tomography (DECT) is a relatively new technique that is becoming increasingly available. One of the advantages of DECT is the ability to maximise iodine detection. Our aim was to test whether single-source, fast kVp-switching DECT can improve imaging quality of CRLM compared to conventional (polychromatic) CT. MATERIAL AND METHODS: Twenty consecutive patients were enrolled into a preliminary prospective study. The scanning protocol consisted of four phases: non-contrast with standard 120 kV tube voltage and three post-contrast phases with rapid voltage switching. As a result, three sets of images were reconstructed: pre- and postcontrast polychromatic (PR), monochromatic (MR), and iodine concentration map (IM). To compare the sensitivity of the tested reconstructions, the number of CRLMs and the maximum diameter of the largest lesion were calculated. Objective image quality was measured as signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). The radiation dose was expressed as CTDIvol. RESULTS: Imaging was successfully performed in all patients. The number of detected lesions was significantly lower on PR images than on IM and MR 50-70 keV (mean number: 4.20 and 4.45, respectively). IM and MR at 70 keV presented the highest quality. SNR was significantly higher for IM and 70 keV images than for other reconstructions. The mean radiation dose was 14.61 mGy for non-contrast 120 kV scan and 17.89 mGy for single DECT scan (p < 0.05). CONCLUSIONS: DECT is a promising tool for CRLM imaging. IM and low-photon energy MR present the highest differences in contrast between metastases and the normal liver parenchyma.

Noninvasive evaluation of renal tissue oxygenation with blood oxygen level-dependent magnetic resonance imaging early after transplantation has a limited predictive value for the delayed graft function.

PURPOSE: The aim of this study was to evaluate the feasibility of renal oxygenation assessment using blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) in the early period after kidney transplantation and to estimate its prognostic value for delayed graft function. MATERIAL AND METHODS: Examinations were performed in 50 subjects: 40 patients within a week after the kidney transplantation and 10 healthy controls, using T2*-weighted sequence. Measurements in transplant patients were correlated to basic laboratory parameters in the early period after transplantation and at follow-up. RESULTS: Examinations of seven patients (18%) were rejected due to their poor technical quality. Mean R2* values in transplant recipients were lower than in controls (11.6 vs. 15.9 Hz; p = 0.0001). An R2* value of 0.28 Hz was calculated as the minimal detectable change. There was no relation between R2* values and laboratory parameters. However, patients eGFR ≥ 40 ml/min/1.73 m2 presented higher R2* values than recipients eGFR < 40 ml/min/1.73 m2 (12.0 vs. 11.1 Hz; p = 0.0189). In ROC analysis R2* of ≤ 11.7 predicted an early reduced graft function with 0.82 sensitivity and 56% specificity (AUC = 0.708; p = 0.024) but was not useful for delayed graft function prediction (p > 0.7). CONCLUSIONS: Evaluation of renal graft oxygenation using BOLD MRI is technically challenging in the early period after transplantation. An R2* value of 0.28 Hz may in practice be considered as the minimal detectable change. The delayed graft function seems not to be dependent on early oxygenation values. Further, large-scale studies are necessary to confirm the latter observation.

Three-Dimensional Cephalometric Analysis of Orbital Morphology Modification for Midface Correction Surgery.

OBJECTIVES: The aim of this study was to create an evidence-based three-dimensional cephalometric analysis of orbits in order to perform time-efficient measurements of postoperative orbital morphology changes. MATERIALS AND METHODS: The authors used 23 (11 bilateral and 1 unilateral) anatomical landmarks. Based on these, 6 planes, 12 angular and 16 linear measurements were determined. A three dimensional analysis was performed twice by two observers on pre and post-operative computed tomography scans of six patients who had undergone midface advancement. The mean, minimal and maximal difference, as well as standard deviation (SD) and intraclass correlation coefficient (ICC) for the inter- and intra-observer landmark selection reliability were calculated. Additionally, the mean, minimal, maximal difference and standard deviation between pre- and post-operative angular and linear measurements were calculated to examine a connection between the established measurements and any morphological change. RESULTS: The inter and intra-examiner accuracy of all landmarks for three axes was >0.9 ICC. Despite excellent inter and intra-examiner agreement (<2.49 mm ± 2.05 mm SD) for the landmark selection, linear and angular measurements showed a mismatch, the mean SD for angular measurements was found to be 8.2° and the linear 3.04 mm. DISCUSSION: The possible causes of linear and angular measurement discrepancies are discussed and the future direction for the development of three-dimensional cephalometric analysis of orbits proposed.

Using Doppler ultrasound of the uterine and umbilical arteries and disordered angiogenesis markers (sFlt-1/PlGF) in unified monitoring of ischemic placental syndrome patients.

OBJECTIVE: The shared pathogenesis of placental ischemia entitles us to create a single treatment model. We attempted to develop a unified method for monitoring ischemic placental syndrome patients using Doppler ultrasound of the uterine and umbilical arteries and disordered angiogenesis markers sFlt-1 and PlGF. MATERIAL AND METHODS: 182 pregnant women suffering from the ischemic placental syndrome were divided into four groups depending on the severity of their lesions revealed in the Doppler ultrasound examination and weeks of pregnancy. We analyzed the behavior of clinical and biochemical parameters in these groups and the correlations between the ultrasound examination and the disordered angiogenesis markers. RESULTS: In the group of patients demonstrating more severe Doppler ultrasound lesions, the clinical and biochemical parameters were significantly more expressed, whereas unfavorable obstetric events occurred either earlier or more frequently. Lesions revealed in Doppler occur more commonly in groups before 34th week of pregnancy. Disordered angiogenesis markers are significantly correlated with ultrasound examination results. CONCLUSIONS: A unified method for monitoring the ischemic placental syndrome based on pathogenetic, biophysical (Doppler ultrasound), and biochemical (sFlt-1/PlGF) parameters is feasible and constitutes a valuable supplement to the existing standards, while the high correlations between Doppler ultrasound examinations and both sFlt-1 and PlGF point to a shared pathogenesis of the lesions. Intensity of Doppler changes is connected with time of testing and pregnancy duration.

Anatomical Evaluation of the Pulmonary Veins and the Left Atrium Using Computed Tomography Before Catheter Ablation: Reproducibility of Measurements.

BACKGROUND: Atrial fibrillation (AF) is a common supraventricular arrhythmia. ECG-gated MDCT seems to be currently a method of choice for pre-ablation anatomical mapping due to an excellent resolution and truly isotropic three-dimensional nature. The aim of this study was to establish the between-subject variability and inter-observer reproducibility of anatomical evaluation of the pulmonary veins (PV) and the left atrium (LA) using computed tomography. MATERIAL/METHODS: A retrospective analysis included 42 patients with AF, who were scheduled for a cardiac CT for ablation planning. Images were assessed by two independent radiologists using a semi-automatic software tool. The left atrium anatomy (volume, AP diameter), anatomy of the pulmonary veins (number, ostia diameters and surface area) were evaluated. The relative between-subject variability and the inter-observer variability of measurements were calculated. RESULTS: The heart rate during scanning ranged from 50 to 133/min. (mean 79.1/min.) and all examinations were of adequate image quality. Accessory pulmonary veins were found in 24% of patients. Between-subject variability of the PV ostial cross-sectional area ranged from 33% to 48%. The variability of the left atrium size was 21% for the diameter and 35% for the volume. The inter-observer agreement for the detection of accessory pulmonary veins was good (κ=0.73; 95% CI, 0.54-0.93). CONCLUSIONS: Between-subject variability of the pulmonary vein ostial cross-sectional area and the left artial volume is substantial. The anatomical assessment of the pulmonary vein ostia and the left atrium size in computed tomography presents a good inter-observer reproducibility.