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At least 451 records · Page 25Linked to original sources
PubMedDate not supplied

Detection of central pulmonary embolism on computed tomography densitometry images before computed tomography pulmonary angiography.

OBJECTIVE: The purpose of this article is to describe the imaging findings of acute central pulmonary embolism on computed tomography (CT) densitometry images performed before contrast-enhanced CT pulmonary angiography. METHODS: A retrospective review was conducted of reports from all CT pulmonary angiograms performed at our institution, and cases of acute central pulmonary embolism, defined as those with clot in the main, left, or right pulmonary arteries, were identified. Images of positive studies were reviewed on a picture archiving and communications system (PACS) workstation. RESULTS: A total of 1282 CT pulmonary angiograms were obtained for evaluation of possible acute pulmonary embolism, and 1 combined CT aortogram and pulmonary angiogram was performed for aortic dissection and acute pulmonary embolism. Two hundred fourteen (16.7%) examinations positive for acute pulmonary embolism were identified, 26 (12.1%, 2.0% of total examinations) of which had central clots. Of the 26 patients with central acute pulmonary embolism, 12 (46.1%, 5.6% of all positive studies and 0.9% of all CT pulmonary angiograms) had clots that were visible on the densitometry images. CONCLUSION: Although an uncommon finding, acute central pulmonary embolism can be detected on CT densitometry performed to optimize opacification of the pulmonary arteries for CT pulmonary angiography and may prove useful in selected clinical situations.

Acute Disease↗
PubMedDate not supplied

Multidetector-row computed tomography and 3-dimensional computed tomography imaging of small bowel neoplasms: current concept in diagnosis.

The diagnosis of small bowel neoplasms can present a difficult challenge to the radiologist because the tumors are uncommon, often small, and may be difficult to detect radiographically. The most common small bowel neoplasms include adenocarcinoma, carcinoid, lymphoma, and gastrointestinal stromal tumors. The location and computed tomography (CT) appearance of the small bowel tumors may aid in the diagnosis. For instance, small bowel adenocarcinoma occurs more frequently in the duodenum and may result in obstruction. Carcinoid tumors are more common in the ileum and are typically hypervascular submucosal masses that produce a characteristic mesenteric mass when they spread to the mesenteric nodes. Lymphoma can occur anywhere along the gastrointestinal tract and have a variable CT appearance. It may appear as a single mass, multiple masses, an infiltrating lesion resulting in aneurysmal dilatation of the bowel, or as an exophytic mass. Gastrointestinal stromal tumors are more common in the jejunum and ileum and usually appear exophytic and bulky often with ulceration. Traditionally, small bowel series and enteroclysis have been used for imaging patients with suspected small bowel tumors. More recently, CT is beginning to play a more important role for this clinical indication. The thinner collimation possible with multidetector CT (MDCT) along with water as oral contrast and a good intravenous contrast bolus may improve the sensitivity of CT for detecting small bowel tumors. In addition, MDCT scanners improve the quality of the 3-dimensional CT (3D CT) images that are valuable to the clinicians and surgeons for surgical planning. It is important for the radiologist to be familiar with the CT appearance of these neoplasms and the potential role of MDCT and 3D imaging in their diagnosis and surgical planning.

Adenocarcinoma↗
PubMed1998

Predicting the rates of success and complications of computed tomography-guided percutaneous core-needle biopsies of the thorax from the findings of the preprocedure chest computed tomography scan.

The authors attempted to determine whether the anatomic characteristics of thoracic lesions and the surrounding lung field, as assessed by the preprocedure chest computed tomography (CT) scan, can assist in predicting the yield of complications or positive results of pathologic examination resulting from percutaneous core-needle biopsies (PCNB). The pathologic diagnoses and procedural complications of 50 consecutive thoracic PCNBs (43 men, age range 19-81 years) performed under the guidance of a single operator (J.A.M.) were recorded. Prebiopsy chest CT findings, including the size, depth, location, and border appearance of the lesion, as well as presence or absence of adjacent emphysema, interstitial fibrosis, bullae, pleural effusions, and the age and smoking history of the patient were correlated with the biopsy results and any ensuing complications. The pathologic analysis in 42 patients (84%) was specific enough to positively impact patient management, with 29 malignant and 13 benign entities. The imaging variables that predicted obtaining adequate tissue for pathologic diagnosis were most importantly large size (especially >35 mm), although irregular lesion margins and increased depth were significant as well. Seven patients (14%) experienced a pneumothorax, only one of which (2%) was symptomatic and required thoracostomy. All patients experiencing a pneumothorax had CT evidence of emphysema or interstitial fibrosis and all biopsied masses in these individuals had spiculated borders, with six (86%) in an anterior location and only one involving the pleural surface. We conclude that the preprocedure CT scan can delineate several characteristics of both the patient and the lesion to be biopsied that can assist in predicting the rates of successful tissue retrieval or pneumothorax during PCNBs.

Adult↗
PubMed1998

Helical computed tomography diagnosis of pleural dissemination in lung cancer: comparison of thick-section and thin-section helical computed tomography.

Pleural dissemination in lung cancer was prospectively evaluated by helical computed tomography (CT), and the usefulness of thick-section CT (10-mm collimation; pitch 1) and thin-section CT (2-mm collimation; pitch 1) were compared. The study included 54 patients with pulmonary adenocarcinoma in whom plain chest radiographs showed no evidence of pleural effusion and in whom the primary lesion was seen to be contiguous with the pleural surface on thick-section CT. Thin-section CT was performed for evaluation of the costal, mediastinal, interlobar, and diaphragmatic pleural surfaces. Pathologic examination revealed pleural dissemination in 20 patients (8 resected, 12 nonresected). Pleural dissemination was diagnosed in 12 patients on thick-section CT, and in 20 patients on thin-section CT. False negatives occurred in ten and two patients, respectively. The same two patients were false positives by both methods. Accuracy was 78% for thick-section CT and 93% for thin-section CT, and sensitivity was 50% and 90%, respectively. Thin-section CT provided more useful information than thick-section CT for the evaluation of pleural dissemination in lung cancer.

Adenocarcinoma↗
PubMedDate not supplied

Benign or malignant?: differentiating breast lesions with computed tomography attenuation values on dynamic computed tomography mammography.

OBJECTIVE: To evaluate enhancement effects of breast lesions with dynamic computed tomography (CT) and to determine characteristics to aid in differential diagnosis of benign and malignant lesions. METHODS: One hundred seventy-six women underwent preoperative dynamic CT, in which they were scanned with rapid injection of contrast media (3 mL/s) after 30 seconds and 2 minutes (early and delayed phases, respectively). The CT values and enhancement patterns of malignant lesions (n = 154) were compared with those of benign lesions (n = 22), and the cut point of CT values with the best validity was analyzed. RESULTS: The CT values of malignant lesions were higher than those of benign lesions in both phases (P < 0.0001). The cut point was determined to be 60 Hounsfield units (HU) in the early phase (44% validity, 90% sensitivity). Washout and plateau patterns were more commonly seen in the malignant group (73% specificity). CONCLUSIONS: The analysis of enhancement effects on CT may lead to more appropriate differentiation of benign and malignant lesions.

Adult↗
PubMedDate not supplied

Detailed nodal features of cervical tuberculous lymphadenitis on serial neck computed tomography before and after chemotherapy: focus on the relation between clinical outcomes and computed tomography features.

OBJECTIVE: To investigate the relation between clinical outcomes and nodal features on computed tomography (CT) in cervical tuberculous lymphadenitis (CTBL) before and after antituberculous chemotherapy. METHODS: Fifty-six patients with CTBL underwent CT before and after a 6- or 12-month course of standard chemotherapy. Three radiologists evaluated the nodal features on serial CT retrospectively, including calcification (no/punctuate/large), necrosis (no/eccentric/central), perinodal infiltrations (no/localized/extensive), and enhancing patterns (no/peripheral/homogeneous). The clinical outcome was defined as "favorable" (n = 33) or "unfavorable" (n = 23) at the completion of chemotherapy. RESULTS: All the features on the initial CT scan did not show a statistically significant difference between the favorable and unfavorable groups. On the final CT scan, absence of necrosis (P < 0.005), no infiltration (P < 0.005), no enhancement (P < 0.008), and central enhancement (P < 0.014) were more common in the favorable group, whereas large necrosis (P < 0.005), localized and extensive infiltration (P = 0.005, P < 0.005), and peripheral enhancement were more common in the unfavorable group (P < 0.005, P = 0.009). CONCLUSIONS: Central necrosis, perinodal infiltration, and peripheral rim enhancement on the final CT scan showed differences between the 2 groups. These CT features reflecting inflammation can be useful findings for assessing treatment response.

Adult↗
PubMed2006

Time-course characterization of the computed tomography contrast enhancement of an iodinated blood-pool contrast agent in mice using a volumetric flat-panel equipped computed tomography scanner.

OBJECTIVE: The objective of this study was to determine the time-course of computed tomography (CT) contrast enhancement of an iodinated blood-pool contrast agent. METHODS: Five C57BL/6 mice were anesthetized, imaged at baseline, and given an iodinated blood-pool contrast agent. Micro-CT scans were acquired at 0, 0.25, 0.5, 1, 2, 4, 8, and 24 hours after injection. The mean CT number was determined in a region of interest in 7 organs. RESULTS: The CT contrast enhancement was plotted as a function of time for each organ. We identified an imaging window immediately after injection suitable for visualizing the vascular system and a second imaging window at 24 hours for visualizing liver and spleen. CONCLUSIONS: A single injection of the blood-pool contrast agent can be used for dual-phase investigations of the vasculature (t = 0 hours) and liver (t = 24 hours), which can be applied to studies of liver tumors or disease.

Animals↗
PubMed2006

Intrinsic measurement bias on computed tomography scout view is unpredictable: Computed tomography pelvimetry using a phantom.

Our aim was to determine the degree of bias in CT scanogram measurements. We obtained standard lateral and anteroposterior (AP) pelvimetry scanograms of a phantom pelvis after placing ball bearings or aluminium rods to mark bony landmarks. Computed tomography pelvimetry was carried out at the manufacturer-recommended table height on two commercial CT scanners and at 10-mm increments up to 50 mm above and below this height. The AP inlet, AP outlet, interspinous distance and transverse diameters were each measured three times for each scanogram. The true measurements were obtained directly from the disassembled phantom. Bias was defined as the difference between the CT measurement and the true measurement. Observer error was negligible. The transverse diameter was overestimated at high table positions and underestimated at low table positions on both scanners (+6 to -10 mm). After correcting for geometric distortion, up to 6 mm bias was still present. The point at which no bias occurred was different for each scanner and did not correspond to the manufacturers' recommended table height. The outlet was overestimated on both scanners by up to 5 mm. The true inlet measurement was overestimated by 1.2 mm. The interspinous distance was minimally underestimated on both scanners. The measurements on CT scanogram were underestimated or overestimated in an inconsistent and unpredictable fashion, varying from one type of measurement to another and from CT scanner to CT scanner. This has implications for the accuracy and clinical utility of measurements obtained from a CT scanogram.

Analysis of Variance↗
PubMed1992

Personal computer equipment for dental digital subtraction radiography vs. industrial computer equipment and conventional radiography.

A "low-cost" personal computer (PC) system used to digitize dental radiographs was tested by assessing the accuracy of its subtraction images versus those of "high-cost" industrial equipment and conventional radiography. Subtraction images were made of artificial lesions in human femur bone and subsequently evaluated by students and teachers. The observations were analyzed in terms of true positive and false positive reports. "Low-cost" and "high-cost" subtraction images revealed only small differences in diagnostic accuracy. Compared to conventional radiography, the diagnostic accuracy of the subtraction images with the "low-cost" PC system was significantly higher for all observers. The interexaminer variance was similar for the subtraction and the conventional images for both students and teachers, except for a significantly reduced interexaminer variance for the teachers concerning the true positive reports with the "low-cost" PC subtraction technique.

Bone and Bones↗
PubMed1979

Computed tomographic cavo-urography: lower-extremity contrast infusion simultaneous with computed tomography of the retroperitoneum.

Successful opacification and distention of the inferior vena cava was obtained simultaneously with computed tomography by contrast infusion through a lower-extremity vein. Images obtained by this method displayed retroperitoneal anatomical relationships to better advantage, permitting more accurate interpretation of the upper retroperitoneum, particularly in lymphoma.

Contrast Media↗
PubMed1982

Computed measures on computed tomograms of the head.

Measures of average parietal bone mass (APBM) and average parietal skull width (APSW) were developed using automatic image processing techniques and a special polar coordinate system. The precision of the technique is about 2%; the measures are obtained by processing one section of a computed tomographic head scan obtained without special apparatus. In males the APBM does not decrease with age; in females it splits into two groups of age, probably based on postmenopausal changes. The APSW in both males and females increases slightly with age. The clinical utility of the measures is discussed.

Cephalometry↗
PubMed1984

Angio-computed tomography and dynamic computed tomography in staging of renal cell carcinoma.

Dynamic computed tomography and angio-tomography combine criteria generated by CT with those of angiography and are advocated by the author to improve staging of renal cell carcinoma. Dynamic CT was performed in 29 patients and angio-CT in 12 patients in this group. Rapid acquisition of data permits generation of a CT section in intervals of 1 to 6 seconds, which in turn reflects arterial, capillary, and venous transit of contrast medium through tissues. The propensity for dense enhancement of renal cell carcinoma makes possible positive identification of tumor elements. This feature proved accurate for the assessment of local extension of renal neoplasms in all 29 patients, involvement of the renal vein by tumor in 9/10, involvement of the inferior vena cava by tumor in 6/6, and involvement of regional nodes by tumor in 6/8.

Adenocarcinoma↗
PubMed2004

Comparison of perfusion computed tomography and computed tomography angiography source images with perfusion-weighted imaging and diffusion-weighted imaging in patients with acute stroke of less than 6 hours' duration.

BACKGROUND AND PURPOSE: We aimed to determine the diagnostic value of perfusion computed tomography (PCT) and CT angiography (CTA) including CTA source images (CTA-SI) in comparison with perfusion-weighted magnetic resonance imaging (MRI) (PWI) and diffusion-weighted MRI (DWI) in acute stroke <6 hours. METHODS: Noncontrast-enhanced CT, PCT, CTA, stroke MRI, including PWI and DWI, and MR angiography (MRA), were performed in patients with symptoms of acute stroke lasting <6 hours. We analyzed ischemic lesion volumes on patients' arrival as shown on NECT, PCT, CTA-SI, DWI, and PWI (Wilcoxon, Spearman, Bland-Altman) and compared them to the infarct extent as shown on day 5 NECT. RESULTS: Twenty-two stroke patients underwent CT and MRI scanning within 6 hours. PCT time to peak (PCT-TTP) volumes did not differ from PWI-TTP (P=0.686 for patients who did not undergo thrombolysis/P=0.328 for patients who underwent thrombolysis), nor did PCT cerebral blood volume (PCT-CBV) differ from PWI-CBV (P=0.893/P=0.169). CTA-SI volumes did not differ from DWI volumes (P=0.465/P=0.086). Lesion volumes measured in PCT maps significantly correlated with lesion volumes on PWI (P=0.0047, r=1.0/P=0.0019, r=0.897 for TTP; P=0.0054, r=0.983/P=0.0026, r=0.871 for CBV). Also, PCT-CBV lesion volumes significantly correlated with follow-up CT lesion volumes (P=0.0047, r=1.0/P=0.0046, r=0.819). CONCLUSIONS: In hyperacute stroke, the combination of PCT and CTA can render important diagnostic information regarding the infarct extent and the perfusion deficit. Lesions on PCT-TTP and PCT-CBV do not differ from lesions on PWI-TTP and PWI-CBV; lesions on CTA source images do not differ from lesions on DWI. The combination of noncontrast-enhanced CT (NECT), perfusion CT (PCT), and CT angiography (CTA) can render additional information within <15 minutes and may help in therapeutic decision-making if PWI and DWI are not available or cannot be performed on specific patients.

Adult↗
PubMed2005

Presence of early ischemic changes on computed tomography depends on severity and the duration of hypoperfusion: a single photon emission-computed tomographic study.

BACKGROUND AND PURPOSE: To evaluate the clinical significance of early ischemic change (EIC) on computed tomography (CT), pertinent factors that contribute to the appearance of EIC. METHODS: Both CT and technetium-99m hexamethylpropylene amine oxime were performed on a total of 53 patients (34 men, 19 women, mean 69.7 years old) with acute embolic stroke within 6 hours of onset. Patients were excluded if they showed definite clinical recovery or were administered thrombolytic agents. EIC was evaluated using Alberta Stroke Program Early CT Score (ASPECTS). Residual cerebral blood flow (CBF) was determined on SPECT. Variables that were considered pertinent were patients' age, gender, neurological severity, symptom duration, and residual CBF. Using significant pertinent factors for EIC, separate analyses of brain swelling without hypoattenuation and parenchymal hypoattenuation were performed. RESULTS: Patients with EIC (n=37) showed severe neurological deficits, a longer duration and severe hypoperfusion. A positive correlation was observed between ASPECTS and residual CBF (P=0.002; Kruskal-Wallis test). A logistic-regression analysis revealed that both symptom duration (r=0.024, P=0.006) and severity of hypoperfusion (r= -12.167, P=0.006) are independent factors related to EIC. Symptom duration and residual CBF were significantly different among patients with parenchymal hypoattenuation (n=32), brain swelling without hypoattenuation (n=5), and no EIC (P=0.018 and P=0.001, respectively; one-way ANOVA). CONCLUSIONS: The presence of EIC is determined by the duration and the degree of hypoperfusion. This finding supports the hypothesis that tissue damage may be evaluated by a combination of onset time and the presence of EIC.

Adult↗
PubMed1997

Computing with the leaky integrate-and-fire neuron: logarithmic computation and multiplication.

The leaky integrate-and-fire (LIF) model of neuronal spiking (Stein 1967) provides an analytically tractable formalism of neuronal firing rate in terms of a neuron's membrane time constant, threshold, and refractory period. LIF neurons have mainly been used to model physiologically realistic spike trains, but little application of the LIF model appears to have been made in explicitly computational contexts. In this article, we show that the transfer function of a LIF neuron provides, over a wide-parameter range, a compressive nonlinearity sufficiently close to that of the logarithm so that LIF neurons can be used to multiply neural signals by mere addition of their outputs yielding the logarithm of the product. A simulation of the LIF multiplier shows that under a wide choice of parameters, a LIF neuron can log-multiply its inputs to within a 5% relative error.

Action Potentials↗
PubMed2004

Computed tomography angiographic correlates of early computed tomography signs in acute ischemic stroke.

BACKGROUND AND PURPOSE: Early computed tomography (CT) signs of stroke signify major arterial occlusion. CT angiogram (CTA) is useful in detecting major arterial occlusion and may help triaging patients for intra-arterial thrombolysis. The correlation between the early signs of stroke and arterial occlusion on CTA was studied. METHODS: Consecutive patients with suspected acute anterior circulation ischemic stroke presenting within 6 hours of symptom onset underwent noncontrast CT of the head followed by CTA. The scans were later reviewed for evidence of early signs of stroke on CT scan and intracranial arterial occlusion on CTA. RESULTS: Sixteen of 65 patients had arterial occlusion on CTA; 12 (75%) of these showed the early CT signs of stroke. All the early signs except M2 "dot" sign significantly correlated with middle cerebral artery (MCA) occlusion on CTA. Hyperdense MCA sign was the only independent predictor of a MCA occlusion. CONCLUSION: In a small sample, early CT signs of stroke strongly correlated with arterial occlusion, with hyperdense MCA sign being the most predictive of a MCA occlusion.

Acute Disease↗
PubMed2006

Development of computations in bioscience and bioinformatics and its application: review of the Symposium of Computations in Bioinformatics and Bioscience (SCBB06).

The first symposium of computations in bioinformatics and bioscience (SCBB06) was held in Hangzhou, China on June 21-22, 2006. Twenty-six peer-reviewed papers were selected for publication in this special issue of BMC Bioinformatics. These papers cover a broad range of topics including bioinformatics theories, algorithms, applications and tool development. The main technical topics contain gene expression analysis, sequence analysis, genome analysis, phylogenetic analysis, gene function prediction, molecular interaction and system biology, genetics and population study, immune strategy, protein structure prediction and proteomics.

Biological Science Disciplines↗