U-net based metal segmentation on projection domain for metal artifact reduction in dental CT

Unlike medical computed tomography (CT), dental CT often suffers from severe metal artifacts stemming from high-density materials employed for dental prostheses. Despite the many metal artifact reduction (MAR) methods available for medical CT, those methods do not sufficiently reduce metal artifacts in dental CT images because MAR performance is often compromised by the enamel layer of teeth, whose X-ray attenuation coefficient is not so different from that of prosthetic materials. We propose a deep learning-based metal segmentation method on the projection domain to improve MAR performance in dental CT. We adopted a simplified U-net for metal segmentation on the projection domain without using any information from the metal-artifacts-corrupted CT images. After training the network with the projection data of five patients, we segmented the metal objects on the projection data of other patients using the trained network parameters. With the segmentation results, we corrected the projection data by applying region filling inside the segmented region. We fused two CT images, one from the corrected projection data and the other from the original raw projection data, and then we forward-projected the fused CT image to get the fused projection data. To get the final corrected projection data, we replaced the metal regions in the original projection data with the ones in the fused projection data. To evaluate the efficacy of the proposed segmentation method on MAR, we compared the MAR performance of the proposed segmentation method with a conventional MAR method based on metal segmentation on the CT image domain. For the MAR performance evaluation, we considered the three primary MAR performance metrics: the relative error (REL), the sum of square difference (SSD), and the normalized absolute difference (NAD). The proposed segmentation method improved MAR performances by around 5.7% for REL, 6.8% for SSD, and 8.2% for NAD. The proposed metal segmentation method on the projection domain showed better MAR performance than the conventional segmentation on the CT image domain. We expect that the proposed segmentation method can improve the performance of the existing MAR methods that are based on metal segmentation on the CT image domain.

A bench-top micro-CT capable of simulating head motions

Computational three-dimensional (3D) models of a dental structure generated from 3D dental computed tomography (CT) images are now widely used in digital dentistry. To generate precise 3D models, high-resolution imaging of the dental structure with a dental CT is required. However, a small head motion of the patient during the dental CT scan could degrade the spatial resolution of CT images to the extent that digital dentistry is no longer possible. A bench-top micro-CT has been built to evaluate the head motion effects on the dental CT images. A micro-CT has been built on an optic table with a micro-focus x-ray source and a flat-panel detector. A rotation stage, placed in between the x-ray source and the detector, is mounted on two-directional goniometers that can rotate the rotation stage in two orthogonal directions while the rotation stage is performing the CT scan. The goniometers can make object motions of an arbitrary waveform to simulate head tilting or head nodding. CT images of a phantom have been taken with and without introducing the motions, and the motion effects on the CT images have been evaluated. Object motions parallel to the detector plane have greater effects on the CT images than those against the detector plane. With the bench-top micro-CT, the motion effects have been visually seen at a tiny rotational motion as small as 0.3°. The bench-top micro-CT can be used to evaluate head motion effects on the dental CT images. The projection data, taken with the motion effects, would be used to develop motion artifact correction methods for a high-resolution dental-CT.

Male circumcision: review and authors perspective

The aim of this article was to evaluate the proposed benefits and consequences of male circumcision and highlight the penile prepuce, the poorly understood and much controversial part of the human body. Databases of Pubmed, Science Direct, Springer Link, Wiley Interscience and others were searched. The research papers were studied and discussed. Finally, the opinion of the authors was recorded. Male circumcision is a legacy of the human civilization, originating in Egypt. It confers many prophylactic benefits for the recipient and his female partner. The benefits include protection against urinary tract infections, sexually transmitted diseases including HIV, penile and prostate cancer and cervical cancer in the female partner. At the same time, it is a simple and safe procedure, having minimal risks. The removed prepuce is not a vestigial but an important and unique structure, being used in repair of the common malformations of the penile urethra. Benefits of circumcision vastly outweigh its potential risks. Newborns with penile anomalies are best treated by deferring the procedure until the defect can be corrected using prepuce at few months of age

Studies on laminitis in the horse II-pathogenesis

The microscopic evaluations in acute laminitis were classified into two main phases. Vascular phase: The first changes were detected in the vasculature in the form of microthrombosis in the dermal capillaries, severe interstitial edema and hemorrhage in the primary dermal laminae during the first three days. These changes were manifested clinically by wariness of the hoof wall and coronary b and and bounding in digital pulsation. Epithelial phase: The main epithelial changes were disconfiguration, epithelial cell hyperplasia, hyperkeratinization, necrosis of the laminae within 20 and 30 days. Clinically, there were marked rotation of the third phalanx, flattening of the sole, coronitis, appearance of laminitic rings and spesis of the foot. Progressive pathological changes leading to hoof wall deformity as a result of formation of intermediate degenerative layers separating the stratum lamellatum and third phalanx from the hoof wall, rotation, perforation of the solar aspect and sepsis and appearance of the air or gas in the laminar region of the hoof wall on lateral radiographic during chronic laminitis

Tinea corporis, clinical and mycological study in Dakahlia

Our study was carried out in an attempt to classify and identify the causative fungi of tinea corporis as well as the incidence of the disease in our locality Trichophyton rubrum was the commonest isolated dermatophyte [35.75%]. Trichophyton violaceum comes next in frequency [16.58%], followed by trichophyton metagrophyte and Epidermophyton floccosum [7.77%], Trichophyton schoenleinii [4.66%] while trichophyton tonsurans [0.25%], trichophyton verrucosum [1.56%] and Microsporum canis [0.52%] were at the lowest end of the list, Candida were isolated from 24.87% of positive cases

Effects of ektafos, ratak and agrosan on pregnancy and fetal development in white rats

The teratogenicand other effects on pregnancy of EKTAFOS, agrosan and Ratak were studied. Four groups, each composed of 20 pregnant female white rats between the 10[th] to 19[th] day of gestation were used for revealing the dysmorphogenic effects of these preparations. Ektafos at a dose of 1 .95 mg/kg, body weight daily per os caused 25.2% resorption and 22.1% mortality and the average weight of the foetuses was 1.2 +/- 0.02 gm and their average length 2.1 +/- 0.09 cm. Agrosan at a dose of 100 mg/ 50 mg barley seeds daily caused 21% resorption sites and 18.9% mortality. The averages weight of the foeti was 1.9 +/- 0.02 gm and their average length 2.3 +/- 0.08 cm. Ratak at a dose of 0.9 mg/kg. daily mixed with 50 gm barley seeds caused 31% resorption and 33% mortality. The average weight of the foetuses was 1.4 +/- 0.03 gm and their average length was 2.3 +/- 0.06 cm. These values are significant different from the 12.34% resorption, 11 .5% mortality. Foetal weight of 3 .1 +/- 0.86 gm and foetal length of 4 .0 +/- 0 09 cm for the control group. Visceral examination of the foeti revealed no significant abnormalities compared with those of the control rats. Skeletal examination of the foetuses affected by Ektafos showed "incomplete fusion of the creanium [17.58%]. The incidence of vertebral column changes which included absence of one or more of the coccygeal vertebrae with separation of the wings of the atlas vertebrae was 15%. A reduced number of sternebrae was noted in 15.38% of the foetuses. Absence of some metacarpal, metatarsal and phalanges in the limbs was obtained in 7.67% of the foetuses. Foetuses from Agrosan treated dams showed malformations in the skull, vertebral column, ribs, sternebrae and limbs, their incidence being 15.53, 19.4, 13.59 and 18.53% respectively. Ratak affected rats showed no signs of skeletal malformations