Recently, a practical method of speckle reduction in laser rear projection displays that uses an optical system with a small moving diffuser has attracted much attention. In this paper, a model of the speckle generation and reduction mechanism in the system is presented. We investigated the speckle, focusing on the physical aspects of its generation, rather than treating it statistically. We found that the granularity of the speckle patterns generated by the small diffuser corresponded to the size of the coherent regions on the projection screen. This determined the efficiency of the speckle reduction when the small diffuser was rotated.

Periapical lucencies are often seen incidentally at head and neck imaging studies performed for indications not related to the teeth. These lesions are, however, occasionally manifestations of diseases that have a wide range of effects and may at times represent the source of symptoms that prompted the study. The vast majority of periapical lucencies are the result of apical periodontal or pulpal disease. If found in an advanced state or left untreated, disease related to the tooth may spread to adjacent tissues, including the sinuses, orbits, deep fascial spaces of the neck, and intracranial structures, and result in a significant increase in patient morbidity and mortality. Although the majority of periapical lucencies seen on radiographs and computed tomographic images occur secondary to apical periodontal or pulpal disease, not all lucencies near the tooth root are due to infection. Lucency near the tooth root may be seen in the setting of other diseases of odontogenic and non-odontogenic origin, including neoplasms. Although imaging findings for these lesions can include periapical lucent components, awareness of the varied secondary imaging features can aid the radiologist in developing an accurate differential diagnosis. Familiarity with the imaging features and differential diagnoses of diseases or conditions that cause lucency around the tooth root results in appropriate referral and prompt diagnosis, management, and treatment, and can prevent unnecessary additional imaging or intervention. In addition, early recognition and appropriate treatment of infectious processes will result in improved clinical outcomes and a decrease in morbidity and mortality.

Dual-energy CT showed higher specificity and acceptable sensitivity in diagnosing laryngeal cartilage invasion compared with MR imaging.

BACKGROUND AND PURPOSE: Conventional CT has generally lower detectability of bone marrow invasion than MR imaging due to lower tissue contrast. The purpose of this study was to compare the diagnostic performance of conventional CT alone or in combination with bone subtraction iodine imaging using area detector CT for the evaluation of skull base invasion in patients with nasopharyngeal carcinoma. MATERIALS AND METHODS: Forty-four consecutive patients who underwent contrast-enhanced CT using 320-row area detector CT and contrast-enhanced MR imaging for nasopharyngeal carcinoma staging between April 2012 and November 2017 were enrolled in this retrospective study. Bone subtraction iodine images were generated by subtracting pre-and postcontrast volume scans using a highresolution deformable registration algorithm. Two blinded observers evaluated skull base invasion at multiple sites (sphenoid body, clivus, bilateral base of the pterygoid process, and petrous bone) using conventional CT images alone or in combination with bone subtraction iodine images. Examination of MR and CT images by an experienced neuroradiologist was the reference standard for evaluating sensitivity, specificity, and area under the receiver operating characteristic curve. RESULTS: Twenty-six patients (59%) showed skull base invasion at 84 sites on the reference standard. Conventional CT plus bone subtraction iodine images showed higher sensitivity (92.9% versus 78.6%, P ϭ .02) and specificity (95.6% versus 86.1%, P ϭ .01) than conventional CT images alone for evaluating skull base invasion. The area under the receiver operating characteristic curve for conventional CT plus bone subtraction iodine (0.98) was significantly larger (P Ͻ .001) than the area under the receiver operating characteristic curve for conventional CT alone (0.90). CONCLUSIONS: Conventional CT plus bone subtraction iodine performs more closely to the accuracy of combining CT and MR imaging compared with conventional CT alone. ABBREVIATIONS: AUC ϭ area under the receiver operating characteristic curve; BSI ϭ bone subtraction iodine; CCT ϭ conventional CT; NPC ϭ nasopharyngeal carcinoma N asopharyngeal carcinoma (NPC), arising from the epithelial lining of the nasopharynx, has a propensity to invade the skull base just above the nasopharynx. Skull base invasion indicates a tumor stage of at least T3 according to the eighth edition of

In‐depth theoretical analysis is performed on several methods that have been proposed for the reduction of color breakup on field sequential color LCDs. Among them, our newly proposed method, RGBKKK, gives the best practical result. The results were verified on our field sequential OCB‐mode LCD of 36.9cm‐diagonal XGA size.

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Objective: Nasopharyngeal cystic lesions are commonly encountered on magnetic resonance imaging with significantly overlapped imaging characteristics. The purpose of this study was to determine the prevalence and distinguishing imaging features of cystic lesions in the nasopharynx in the largest patient series to date.Methods: After institutional review board approval, consecutive head magnetic resonance images of 3000 patients performed at 1.5 T between June 2010 and April 2011 were retrospectively reviewed for cystic nasopharyngeal lesions. Location, size, and signal characteristic of cystic lesions were recorded. Electronic medical records were reviewed for patient demographics, symptoms, and underlying conditions. Results: Among 3000 patients, 6% had Tornwaldt cysts (peak prevalence, 51-60 years old) and 10% had mucous retention cysts (peak prevalence, 41-50 years old). A significant correlation between human immunodeficiency virus infection and mucous retention cysts was observed (P < 0.001).Conclusions: The prevalence of Tornwaldt cysts was slightly higher than previously described in the literature. Additionally, younger and older patients had the lowest prevalence of Tornwaldt cyst, suggesting these lesions are acquired and subsequently involute with time. A significant correlation was observed between human immunodeficiency virus infection and mucous retention cysts.

A detailed analysis on "eye-trace integration" which causes the degradation of moving pictures is made. Some intrinsic characteristics and questions are found and the visual results that show the effects of the overdrive and the intraframe blanking are obtained. Also a new possibility is found, that could produce a better view without using blanking. / K. Sekiya