Characterization of Internal Fatigue Cracks in Aluminum Alloys by Simulation of Phase Contrast Tomography

Synchrotron Radiation Computed Tomography (SRCT) allows a better detection of fatigue cracks in metals than laboratory CT due to the existence of phase contrast. However the presence in reconstructed images of fringes at the edges of objects generated by Fresnel diffraction makes it difficult to identify and analyze the cracks quantitatively. Simulations of phase contrast synchrotron tomography images containing cracks with different sizes and shapes are obtained by using GATE software. Analyzing the simulation results, firstly, we confirmed that the bright parts with strong contrast in SRCT image are streak artifacts; secondly, we found that the gray scale values within the cracks in SRCT images are related to the crack size; these simulation results are used to analyse SRCT images of internal fatigue cracks in a cast Al alloy, providing a clearer visualisation of damage.

Hybrid Approach Towards Removal of Streak Artifacts and Region Identification in Brain Radiology

A streak artifact is an anomaly seen in the CT image of the brain. It is like a dark bands or streaks appearing in an image that is not present in the original region. The appearance of these artifacts leads to misinterpretation of medical diagnosis. Under sampling, photon starvation, motion and beam hardening are some of the reasons for occurrence of streak artifacts. These type of artifacts commonly occur in the posterior fossa of the brain. This paper mainly focuses on region shape and texture identification and removal of streak artifacts exists in the brain image. Initially morphological operators and fuzzy k-means algorithms are used to identify the different regions in the CT brain image. Each region is treated as a single image and features are extracted for each image. The feature descriptors are constructed using region properties and statistical features. The extracted features are compared with threshold brain image to identify the dark bands of streak artifacts.

Single-phase bilateral low dose contrast medium injection for diagnosing occlusions of the thoracic venous system: a case report

Occlusion of the thoracic venous system and/or occlusion of central venous catheters (CVC) of unknown cause can, in selected cases, require advanced imaging. Here, we describe a case study of a patient with a failing central dialysis catheter (CDC) which was diagnosed by computed tomography (CT) in connection with a single-phase bilateral low-dose contrast medium (CM) injection using only 3.6 g of iodine. By injecting a low CM dose, the risk of streak artifacts from first-pass of high intravascular concentrations of CM can be avoided. Therefore, the technique described here should be beneficial also to patients with normal renal function.