A new method for determination of the theoretical reduction amount for wide-thick slab during the mechanical reduction process

Mechanical soft reduction (MSR) is an effective method for elimination of the centerline segregation and porosity of the continuous casting steel slab, and the reduction amount is a key parameter that determines whether the MSR could be applied successfully. In the present work, a 2D heat transfer model was developed for predicting the non-uniform solidification of the wide-thick slab. The measured shell thickness by nail shooting experiment and the measured slab surface temperature by infrared camera were applied to validate the 2D heat transfer model. A new calculation method of theoretical reduction amount that could consider the influence of non-uniform solidification of the wide-thick slab was then derived. Based on the predicted temperature field by the 2D heat transfer model and the newly-proposed calculation method, the required theoretical reduction amount and reduction gradient/rate for the wide-thick slab were calculated and discussed. The difference between the newly-proposed method and the previous method, the influence of the casting speed and slab thickness on the required theoretical reduction amount and reduction gradient/rate were also investigated.

Thin Slices and Maximum Intensity Projection Reconstructions Increase Sensitivity to Hyperdense Middle Cerebral Artery Sign in Acute Ischemic Stroke

Introduction: Cranial nonenhanced CT (NECT) imaging in hyperacute ischemic stroke is rarely used for assessing arterial obstruction of middle cerebral artery by identifying hyperdense artery sign (HAS). Considering, however, its growing importance due to its impact on the decision-making process of thrombolysis with or without mechanical thrombectomy improved sensitivity to HAS is necessary, particularly in the group of less experienced clinicians being frequently the first one assessing the presence of HAS on NECT. Objective: The present study aimed to investigate the effect of different NECT image reconstructions on the correct detection of hyperdense middle cerebral artery sign in a cohort of observers with lower experience level on NECT. Particularly, MIP image reconstructions were expected to be useful for less experienced observers due to both strengthening of the hyperdensity of HAS and streamlining to less image slices. Methods: Twenty-five of 100 patients’ NECT image data presented with HAS. Sixteen observers with lower practice level on NECT (10 radiologists and 6 neurologists) evaluated independently the 3 image reconstructions of each data set with thin slice 1.5 mm, thick slab 5 mm, and 6-mm maximum intensity projection (MIP) and rated the presence of HAS in middle cerebral artery. A GEE model with random observer effect was used to examine the influence of the 3 image reconstructions on sensitivity to HAS. A linear mixed effects regression model was used to investigate the ranking of detectability of HAS. Interrater reliability was determined by Fleiss’ kappa coefficient (κ). Results: Recognition of HAS and sensitivity to HAS significantly differed between the 3 image reconstructions (p = 0.0106). MIP and thin slice reconstructions yielded each on average the highest sensitivities with 73% compared to thick slab reconstruction with 45% sensitivity. The interobserver reliability was fair (κ, 0.3–0.4). Detectability of HAS was significantly easier and better visible ranked on MIP and thin slice reconstructions compared to thick slab (p < 0.05). Conclusion: MIP and thin slice reconstructions increased the sensitivity to HAS (73%), whereas thick slab reconstructions seemed to be less appropriate (45%).

Signal suppressions of grape syrup and grape syrup/lemon aqueous solutions in magnetic resonance cholangiopancreatography using heavily T2-weighted pulse sequence

Signal suppression of the gastrointestinal tract fluids in magnetic resonance cholangiopancreatography (MRCP) has been performed using various natural and chemical substances with the different MRCP pulse sequences. This study aimed to investigate the signal suppressions of the grape syrup and the grape syrup/lemon aqueous solutions in MRCP using the heavily T2-weighted sequences. For this purpose, the potassium, iron and manganese contents of grape syrup were measured by atomic absorption spectroscopy. The grape syrup and the grape syrup/lemon solutions with the various grape syrup percentages were imaged using the heavily T2-weighted sequences of MRCP such as T2 HASTE thick slab and T2 SPACE. MRCP in the volunteers was performed before and 10 minutes after oral administration of the grape syrup solution. The concentrations of potassium, iron, and manganese in grape syrup were 34.8, 2.4 and 1 mg/l, respectively. The in vitro study showed significantly lower signal to noise ratio using the grape syrup samples comparing to the grape syrup/lemon. The effective signal suppression for the in vitro study and considerable enhancement of negative contrast in the post-contrast MRCP was obtained using a T2 HASTE thick slab sequence. As a conclusion, the grape syrup solution can be used for signal suppression of the gastrointestinal tract fluid in MRCP as an oral negative contrast material. A T2 HASTE thick slab sequence produces suitable contrast in MRCP images using the grape syrup solution.