25,265 research outputs found
Delta-aminolaevulinic acid mediated photodynamic antimicrobial chemotherapy on Pseudomonas aeruginosa planktonic and biofilm cultures.
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Application of CT in Diagnosing Carcinoma of the Maxillary Sinuses : PART 2: An Experimental Study of Pitfalls Encountered when Diagnosing Carcinoma of the Maxillary Sinuses with CT
Get PDF1982-03A phantom simulating the transverse section of the maxillary sinuses was constructed for experimentation with various CT scanners to study the following: (1) the occasional inability to image the very thin posterior-lateral walls which have no real bone defects, and (2) to verify whether or not the bony walls surrounding the maxillary sinuses are actually as thick as they appear on CT. The phantom was made of an acrylic cylinder containing three cavities simulating the maxillary sinuses and the nasal cavity and filled with water. The walls, made of thin aluminum and acrylic plates and placed between water and air, disappeared in some CT images. The thickness of the walls calculated from CT values was greater than the true thickness imaged by each CT scanner. The author stresses that in CT images, either experimentally or clinically, thin bony walls placed between water and air or fat tend to disappear, and that bony walls tend to appear thicker than their true thickenss.departmental bulletin pape
The prevalence of pulmonary parenchymal tuberculosis in patients with tuberculous pleuritis
No full textStudy objective: To examine the prevalence and characteristics of parenchymal tuberculous pleuritis in adult patients. Design: Prospective cohort study. Setting: Three hospitals affiliated with Seoul National University in South Korea. Patients: All patients > 15 years old with a diagnosis of tuberculous pleuritis were enrolled prospectively between January 1, 2004, and October 31, 2004. Interventions: Diagnostic thoracocentesis and CT of the chest were done for each patient. Acid-fast bacilli (AFB) smears and cultures for Mycobacterium tuberculosis were requested if patients produced any sputum. A board-certified radiologist reviewed the chest radiographs for the presence and characteristics of any lesions. Measurements and results: One hundred six patients with tuberculous pleuritis were enrolled (median age, 53 years; range 16 to 89 years). Among them, 33 patients (31%) had sputum or bronchial washing findings positive for AFB smears or for M tuberculosis by culture. Lung parenchymal lesions were observed in 91 of the patients (86%) using chest CT; 39 patients (37%) with parenchymal lesions had radiographic characteristics of active pulmonary tuberculosis. In total, 62 patients (59%) had bacteriologically or radiographically active pulmonary tuberculosis. In addition, 78 patients (74%) had features of reactivated pulmonary tuberculosis. Conclusions: Lung parenchymal lesions were more common in this series of patients with tuberculous pleuritis than has been reported in previous studies. The patients mostly had radiographic features of reactivated, rather than primary, tuberculosis.N
Can the ischemic penumbra be identified on noncontrast CT of acute stroke?
Get PDF<p><b>Background and Purpose:</b> Early ischemic changes on noncontrast CT in acute stroke include both hypoattenuation and brain swelling, which may have different pathophysiological significance.</p>
<p><b>Methods:</b> Noncontrast CT and CT perfusion brain scans from patients with suspected acute stroke <6 hours after onset were reviewed. Five raters independently scored noncontrast CTs blind to clinical data using the Alberta Stroke Program Early CT Score (ASPECTS). Each ASPECTS region was scored as hypodense or swollen. A separate reviewer measured time to peak and cerebral blood volume in each ASPECTS region on CT perfusion. Time to peak and cerebral blood volume were compared for each region categorized as normal, hypodense, or isodense and swollen.</p>
<p><b>Results:</b> Scans of 32 subjects a median 155 minutes after onset yielded 228 regions with both CT perfusion and noncontrast CT data. Isodense swelling was associated with significantly higher cerebral blood volume (P=0.016) and with penumbral perfusion (posttest:pretest likelihood ratio 1.44 [95% CI: 0.68 to 2.90]), whereas hypodensity was associated with more severe time to peak delay and with core perfusion (likelihood ratio 3.47 [95% CI: 1.87 to 6.34]). Neither isodense swelling nor hypodensity was sensitive for prediction of perfusion pattern, but appearances were highly specific (87.2% and 91.0% for penumbra and core, respectively). Intrarater agreement was good or excellent, but interrater agreement for both hypodensity and swelling was poor.</p>
<p><b>Conclusions:</b> Regions exhibiting hypoattenuation are likely to represent the infarct core, whereas regions that are isodense and swollen have increased cerebral blood volume and are more likely to signify penumbral perfusion. Although noncontrast CT is not sensitive for detection of core and penumbra, appearances are specific. Some information on tissue viability can therefore be obtained from noncontrast CT.</p>
sj-docx-1-acr-10.1177_02841851221095925 - Supplemental material for Non-ECG-gated high-pitch CT angiography versus hybrid ECG-gated CT angiography for aorta using 512-slice CT: comparison of image quality and radiation dose
No full textSupplemental material, sj-docx-1-acr-10.1177_02841851221095925 for Non-ECG-gated high-pitch CT angiography versus hybrid ECG-gated CT angiography for aorta using 512-slice CT: comparison of image quality and radiation dose by Jimin Lee, Yeon Joo Jeong, Geewon Lee, Chang Won Kim, Jin You Kim, Nam Kyung Lee, Han Cheol Lee and Ji Won Lee in Acta Radiologica</p
Detectability of colorectal neoplasia with fluorine-18-2-fluoro-2-deoxy-D-glucose positron emission tomography and computed tomography (FDG-PET/CT)
No full textThe purpose of this study was to analyze the detectability of colorectal neoplasia with fluorine-18-2-fluoro-2-deoxy-d-glucose positron emission tomography/computed tomography (FDG-PET/CT).
Data for a total of 492 patients who had undergone both PET/CT and colonoscopy were analyzed. After the findings of PET/CT and colonoscopy were determined independently, the results were compared in each of the six colonic sites examined in all patients. The efficacy of PET/CT was determined using colonoscopic examination as the gold standard.
In all, 270 colorectal lesions 5 mm or more in size, including 70 pathologically confirmed malignant lesions, were found in 172 patients by colonoscopy. The sensitivity and specificity of PET/CT for detecting any of the colorectal lesions were 36 and 98%, respectively. For detecting lesions 11 mm or larger, the sensitivity was increased to 85%, with the specificity remaining consistent (97%). Moreover, the sensitivity for tumors 21 mm or larger was 96% (48/50). Tumors with malignant or high-grade pathology were likely to be positive with PET/CT. A size of 10 mm or smaller [odds ratio (OR) 44.14, 95% confidence interval (95% CI) 11.44-221.67] and flat morphology (OR 7.78, 95% CI 1.79-36.25) were significant factors that were associated with false-negative cases on PET/CT.
The sensitivity of PET/CT for detecting colorectal lesions is acceptable, showing size- and pathology-dependence, suggesting, for the most part, that clinically relevant lesions are detectable with PET/CT. However, when considering PET/CT for screening purposes caution must be exercised because there are cases of false-negative results
Development of a synthetic phantom for the selection of optimal scanning parameters in CAD-CT colonography
Get PDFThe aim of this paper is to present the development of a synthetic phantom that can be used for the selection of optimal scanning parameters in computed tomography (CT) colonography. In this paper we attempt to evaluate the influence of the main scanning parameters including slice thickness, reconstruction interval, field of view, table speed and radiation dose on the overall performance of a computer aided detection (CAD)–CTC system. From these parameters the radiation dose received a special attention, as the major problem associated with CTC is the patient exposure to significant levels of ionising radiation. To examine the influence of the scanning parameters we performed 51 CT scans where the spread of scanning parameters was divided into seven different protocols. A large number of experimental tests were performed and the results analysed. The results show that automatic polyp detection is feasible even in cases when the CAD–CTC system was applied to low dose CT data acquired with the following protocol: 13 mAs/rotation with collimation of 1.5 mm × 16 mm, slice thickness of 3.0 mm, reconstruction interval of 1.5 mm, table speed of 30 mm per rotation. The CT phantom data acquired using this protocol was analysed by an automated CAD–CTC system and the experimental results indicate that our system identified all clinically significant polyps (i.e. larger than 5 mm)
Sequential morphological changes in follow-up CT of pulmonary mucormycosis
Get PDFPURPOSEWe aimed to describe the computed tomography (CT) features of pulmonary mucormycosis including sequential changes between follow-ups. MATERIALS AND METHODSBetween June 2001 and May 2011, five patients (three males and two females; median age, 43 years; age range, 13–73 years) who had been pathologically diagnosed with pulmonary mucormycosis constituted our study population. Their clinical and CT features including sequential changes over follow-ups were evaluated retrospectively. RESULTSAll patients were immunocompromised due to either hematologic diseases (n=3), diabetes mellitus (n=1), or steroid administration for autoimmune hepatitis (n=1). All patients had symptoms such as fever (n=5), tachycardia (n=1), or pleuritic chest pain (n=1) on admission. Regarding the clinical outcome after treatment, one patient died, and the remaining four recovered from the disease. In terms of initial CT features, the morphologies of pulmonary mucormycosis included a single mass (n=3), consolidation (n=1), or multiple masses (n=1). There were seven pulmonary lesions in total, 3–7 cm in size, which showed a CT halo sign (n=3), reversed-halo sign (n=2), or air-fluid levels (n=2). On follow-up CTs, the lesions of all patients contained necrosis. All three patients with a mass or masses with a CT halo sign on initial CT had a decreased surrounding halo followed by central necrosis, and the lesions gradually decreased in size on recovery. CONCLUSIONPulmonary mucormycosis usually manifests as a mass or masses with a halo or reversed-halo sign on the initial CT scan followed by a decreased extent of surrounding ground-glass opacities with the development of internal necrosis during follow-up
Deciphering seismic response of landslide-prone slopes from reconnaissance microtremor measurements with a broad-band velocimeter
No full textRecent experimental studies have pointed out that susceptibility of slopes to seismically induced failures can be significantly increased by site conditions determining phenomena of directional resonance along potential sliding directions. Evidence of such situations were obtained from long-term accelerometric monitoring conducted in central Italy (Caramanico Terme), and it has been suggested that similar phenomena may have influenced also some of the giant landslides triggered in Taiwan by the 1999 Chi-Chi earthquake. Since factors controlling directional resonance are still unclear, it is of great interest to develop reconnaissance techniques capable to point out the occurrence of conditions of site response directivity. One promising technique is based on the analysis of the azimuthal variations of the spectral ratios between horizontal and vertical component of noise recordings (HVNR), derived from microtremors measured with portable velocimeters. At this regard an extension of observations to low frequency spectral ratios, even below 1 Hz, is desirable, especially in the case of very large landslides whose stability conditions under seismic shaking could be more sensitive to the effect of larger wavelengths. For this reason we tested the employment of a portable broad-band sensor for HVNR measurements on landslide-prone slopes. First, measurements previously carried out at Caramanico with different seismometric sensors were repeated for comparative purposes. Then, data acquisition was extended to other sites in the same area and in two areas of Taiwan, on the giant landslides of Tsaoling and Jiufengershan. It is recognized that the analysis of noise recording on a broader frequency bandwidth poses some supplementary difficulties for the presence of strong low frequency signals that vary with atmospheric and sea conditions. However, the measurements obtained at Caramanico showed that, where clear site response directivity had been revealed by previous observations, the results of HVNR analysis derived from broad-band measurements were consistent with those derived by other type of sensors. At other Caramanico sites, HVNR analysis of the broad-band data provided uncertain results, possibly as effect of variable conditions of data acquisition that might obscure weaker site response effects. In some cases the repeatability of the results was a problem, possibly due to temporary action of a local source of strong polarised noise. The measurements obtained in Taiwan in the two giant landslide areas, both characterised by mass movements occurred along bedding surface, revealed the presence of abnormally high values of HVNR for sites on slip surfaces, with a very strong directional variation through a large frequency band and with pronounced maxima at frequency less than 1-2 Hz, i.e. at frequencies influenced by signals of atmospheric and marine origin. Although the recordings on nearby sites on the flanks or the crowns of the landslides did not reveal similar properties, the representativeness and exact significance of the HVNR data acquired on the slip surfaces need to be more deeply investigated in order to exclude the effects of anomalous acquisition conditions. More in general, contemporaneous measurements of noise with two different types of instruments at different times and varying environmental conditions should help to clarify to what extent the reconnaissance type of noise measurements by broad-band instruments could be useful for detecting directivity in seismic site respons
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