Numerical Simulation of Impact Rockburst of Elliptical Caverns with Different Axial Ratios

Herein, a finite discrete element method was used to simulate the rockburst phenomenon of elliptical caverns with different axis ratios. Two situations were employed, namely when the disturbance direction is perpendicular and parallel to the ellipse. Based on the peak stress, maximum velocity, stress nephogram, and image fractal characteristics, the influence of axis ratio and direction of the disturbance on rockburst were analyzed. The results show that the samples with different axis ratios experienced the same process of quiet period, slab cracking period, and rockburst. The rockburst pit had V shape, and the failure modes of rockburst primarily included shear cracks, horizontal tension cracks, and vertical tension cracks. With the rise in axis ratio, the peak stress and maximum speed increased. Furthermore, the pressure area on the left and right sides of the sample cavern decreased when the disturbance direction was parallel to the short axis of the ellipse, while it increased for the sample with a disturbance direction perpendicular to the short axis. The fractal dimension value of the crack was gradually amplified with disturbance. The fractal dimension value of the sample whose disturbance direction was perpendicular to the minor axis of the ellipse was lower, and it was more difficult to damage.

Reference Values of Native T1 at 3T Cardiac Magnetic Resonance—Standardization Considerations between Different Vendors

This study aimed at establishing native T1 reference values for a Canon Vantage Galan 3T system and comparing them with previously published values from different vendors. A total of 20 healthy volunteers (55% Women; 33.9 ± 11.1 years) underwent left ventricular T1 mapping at 3T MR. A MOLLI 5(3)3 sequence was used, acquiring three short-axis slices. Native T1 values are shown as means (±standard deviation) and Student’s independent samples t-test was used to test gender differences in T1 values. Pearson’s correlation coefficient analysis was used to compare two processes of T1 analysis. The results show a global native T1 mean value of 1124.9 ± 55.2 ms (exponential analysis), that of women being statistically higher than men (1163 ± 30.5 vs. 1077.9 ± 39.5 ms, respectively; p < 0.001). There were no specific tendencies for T1 times in different ventricular slices. We found a strong correlation (0.977, p < 0.001) with T1 times derived from parametric maps (1136.4 ± 60.2 ms). Native T1 reference values for a Canon 3T scanner were provided, and they are on par with those already reported from other vendors for a similar sequence. We also found a correlation between native T1 and gender, with higher values for women.

Imaging features of sentinel lymph node mapped by multidetector-row computed tomography lymphography in predicting axillary lymph node metastasis

Introduction Accurately assessing axillary lymph node (ALN) status in breast cancer is vital for clinical decision making and prognosis. The purpose of this study was to evaluate the predictive value of sentinel lymph node (SLN) mapped by multidetector-row computed tomography lymphography (MDCT-LG) for ALN metastasis in breast cancer patients. Methods 112 patients with breast cancer who underwent preoperative MDCT-LG examination were included in the study. Long-axis diameter, short-axis diameter, ratio of long-/short-axis and cortical thickness were measured. Logistic regression analysis was performed to evaluate independent predictors associated with ALN metastasis. The prediction of ALN metastasis was determined with related variables of SLN using receiver operating characteristic (ROC) curve analysis. Results Among the 112 cases, 35 (30.8%) cases had ALN metastasis. The cortical thickness in metastatic ALN group was significantly thicker than that in non-metastatic ALN group (4.0 ± 1.2 mm vs. 2.4 ± 0.7 mm, P < 0.001). Multi-logistic regression analysis indicated that cortical thickness of > 3.3 mm (OR 24.53, 95% CI 6.58–91.48, P < 0.001) had higher risk for ALN metastasis. The best sensitivity, specificity, negative predictive value(NPV) and AUC of MDCT-LG for ALN metastasis prediction based on the single variable of cortical thickness were 76.2%, 88.5%, 90.2% and 0.872 (95% CI 0.773–0.939, P < 0.001), respectively. Conclusion ALN status can be predicted using the imaging features of SLN which was mapped on MDCT-LG in breast cancer patients. Besides, it may be helpful to select true negative lymph nodes in patients with early breast cancer, and SLN biopsy can be avoided in clinically and radiographically negative axilla.

366 The use of dedicated long-axis views focused on the left atrium improves the accuracy of left atrial volumes and function measured by cardiovascular magnetic resonance

Aims The use of apical views focused on the left atrium (LA) has improved the accuracy of LA volume evaluation by two-dimensional echocardiography. However, routine cardiac magnetic resonance (CMR) evaluation of LA volumes still uses standard 2- and 4-chamber cine images focused on the left ventricle. To investigate the potential of LA-focused CMR cine images, we compared LA maximal (LAVmax) and minimal (LAVmin) volumes, and emptying fraction (LA-EF) calculated on both standard and LA-focused long-axis cine images with LA volumes obtained by short-axis cine stacks covering the LA. Methods and results LA volumes and LA-EF were obtained from 108 consecutive patients by applying the biplane area-length algorithm to both standard and LA-focused 2- and 4-chamber cine images. Manual segmentation of a short-axis cine stack covering the LA was used as the reference method. Compared to the reference method, the standard approach significantly underestimated LA volumes (LAVmax: bias −13 ml; LOA = +11 ml, −37 ml; LAVmin; bias −10 ml, LOA: +9 ml, −28ml), and overestimated LA-EF (bias= 5%, LOA: +23%, −14%). Conversely, LA volumes (LAVmax bias −0.03 ml; LOA: +10 ml, −10 ml. LAVmin bias = −1.5 ml; LOA: +7 ml, −10 ml), and LA-EF (bias 2%, LOA: +11%, −7%) by LA-focused cine images were similar to those measured using the reference method. Moreover, LA volumes by LA-focused images were obtained faster than using the reference method (1.2 vs. 4.5 min, P &lt; 0.001). Conclusions LA volumes and LA-EF measured using dedicated LA-focused long-axis cine imaging are more accurate than using standard (LV-focused) cine images.

Extra & Intravascular Ultrasound (E&IVUS) Guided Intervention for Femoropopliteal Arterial Occlusive Lesions.

Background: Intravascular ultrasound (IVUS) shows vascular structures and positions of interventional devices in cross sectional-short axis to support interventions, especially for complex lesions. On the other hand, extravascular ultrasound (EVUS) visualizes the devices and vessel structures in long and short axis and reduces the radiation exposure by avoiding the use of fluoroscopy during guidewire manipulation. The images obtained from EVUS handling to guide the guidewire manipulation in both long and short axis is more difficult, time consuming, and stressful than IVUS, which is in short axis only. To solve this issue, we propose a novel guidewire crossing method in conjunctive with the use of both modalities, named “extra and intravascular ultrasound (E&IVUS)” guided intervention.Main text: This is the first report of a combined use of EVUS and IVUS for femoropopliteal occlusions. EVUS-guided intervention is mandatory to check the position of the device in long and short axis. However, the images of long axis are sometimes different from the original ones when EVUS is required to image from the short axis to the long axis. E&IVUS allows to dedicate EVUS to acquisition of the long axis and IVUS to the short axis view when confirming the device position. As a result, E&IVUS shortens the operation time and reduces the stress due to the manipulation of the probe to switch from the long to short axis image and vice versa. Moreover, we can accurately manipulate the guidewire to perform intimal tracking according to the information of EVUS long axis and the IVUS short axis images. Case involved a 76-year-old female with right superficial femoral artery occlusion was angiographically contrasted from a contralateral 6-Fr sheath. A hard wire supported with an over-the-wire typed IVUS was advanced into the CTO with EVUS and IVUS to confirm their positions until the guidewire crossing. We repeatedly performed this process, and all intimal tracking succeeded. The drug-coating balloons appropriately sized by IVUS measurement were deployed. Finally, a sufficient blood flow was achieved without complications.Conclusions: E&IVUS is a preferred strategy than using EVUS or IVUS alone. We should evaluate the clinical outcomes of this technique.