9,384 research outputs found
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
Full text link1982-03A 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
Incipient speciation by sexual isolation in Drosophila melanogaster: variation in mating preference and correlation between sexes.
No full textIncipient speciation by sexual isolation in Drosophila melanogaster: extensive genetic divergence without reinforcement.
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Usefulness of (Ti)-T-201 Spect/Ct Relative to F-18-Fdg Pet/Ct in Detecting Recurrent Skull Base Nasopharyngeal Carcinoma
No full textBackground. This study was designed to compare (TI)-T-201 single photon emission computed tomography (SPECT)/CT with 18-fluoro-2-deoxyglucose (F- 18-FDG) PET/CT in diagnosing recurrent skull base nasopharyngeal carcinoma (NPC). Methods . Twenty-seven patients were recruited. Both (TI)-T-201 SPECT/CT and F-18-FDG PET/CT for each patient were performed at least 4 months later after initial therapy. Results. The sensitivity and specificity for (TI)-T-201 SPECT/CT were 66 .7% and 100%, and those for F- 18-FDG PET/CT were 86.7% and 75.0%. Lesion/background ratios were obtained for the 10 lesions that were both SPECT and PET true positive. For the 8 patients with recurrences in nasopharyngeal regions, PET lesion/background ratios were all higher than SPECT lesion/ background ratios. For the 2 patients with intracranial metastases, SPECT lesion/background ratios were higher than PET lesion/background ratios. Conclusion. (TI)-T-201 SPECT/ CT is as effective as F-18-FDG PET/CT in detecting recurrent NPC. For intracranal recurrence, (TI)-T-201 SPECT, because of its high intracranial lesion/background ratio, is probably better than F-18-FDG PET
Evaluation of Artery Wall Distensibility using Automatic Segmentation on CT Angiography Images
No full textPulmonary artery hypertension (PAH), which is diagnosed by an abnormal increase of blood pressure in the pulmonary artery, can be a severe disease, leading to heart failure. In recent years, medical imaging, such as echocardiography, magnetic resonance imaging (MRI), and computed tomography (CT), has been widely used due to its non-invasive property. Right pulmonary artery (RPA) wall distensibility derived from CT angiography was reported to serve as a reliabile marker for the diagnosis of PAH.
This study presented a robust method for automatic segmentation of artery based on CT angiography. The algorithm can be divided into two steps: generation of initial contour and refinement of edge. In the first step, a series of original images at different cardiac phases were thresholded to retrieve appropriate intensity window of vessels, followed by the determination of initial contours by a series of morphological image processing on the binary images with two simple manual initializations. Initial contours without touching can be taken as the final results of segmentation, when others need further refinement of edge. In the second step, the center of vessel was automatically located by an ellipse fitting method and then the ray casting algorithm was applied to search for possible edge. Disconnected segments of edge will be linked to complete the vessel segmentation. Furthermore, cross-sectional areas of arteries at different cardiac phases can be measured and used to obtain distensibility. In this study, artery wall distensibility of patients and healthy subjects was evaluated on four vessels, including aorta, main pulmonary artery, right and left pulmonary artery. In addition, segmentation results of five subjects were compared with those obtained by manual selection to evaluate the reliability of the proposed method
Reduction of CT dose for CT-based PET attenuation correction
Full text linkThesis (Ph.D.)--University of Washington, 2012One important goal of quantitative imaging using positron emission tomography (PET) combined with X-ray computed tomography (CT) is to accurately measure a tumor's characteristics both before and during therapy to determine as early as possible the efficacy of the treatment. The transmission CT scans in the dual modality PET/CT are used for attenuation correction of the PET emission data. Two significant challenges for quantitative PET/CT imaging come from respiratory motion in lung cancer imaging and estimation of the attenuation coefficients for high atomic number materials in bone imaging. Longer duration respiratory-gated CT has been proposed for attenuation correction of phase-matched respiratory-gated PET and motion estimation. Dual energy CT (DECT) has been proposed for accurate CT based PET attenuation correction (CTAC) for bone imaging. However, for both methods, the radiation dose from the CT scan is unacceptably high with the current CT techniques. This directly limits the clinical application of the quantitative PET imaging. Ultra-low dose CT for PET attenuation correction is studied for lung cancer imaging. Selected combinations of dose reduced acquisition and noise suppression methods are investigated by taking advantage of the reduced requirement of CT for PET CTAC. The impact of these methods on PET quantitation is evaluated through simulations on different digital phantoms. When CT is not used for diagnostic and anatomical localization purposes, it is shown that ultra-low dose CT for PET/CT is feasible. The noise and bias propagation from DECT acquisitions to PET or SPECT are studied for bone imaging, and related dose minimization are investigated. It is shown that through appropriate selection of CT techniques, DECT could deliver the same radiation dose as that of a single spectra CT and provide accurate attenuation correction for PET imaging containing high-Z materials. Finally, phantom-based measured experiments are performed to characterize the simulation and provide spectra validation
CT-assessed body composition and tumor immunologic characteristics in patients with non-small-cell lung cancer
No full textAbstract
Objectives: Obesity is associated with higher immunotherapy efficacy, but body mass index is a convoluted marker of adipose and muscle tissue. We conducted a discovery scale study to assess the association of skeletal muscle and adipose tissue areas annotated on computed tomography (CT) scan images with selected tumor immunologic characteristics among patients with non-small-cell lung cancer (NSCLC).
Methods: We analyzed publicly available data from 102 patients (mean age = 67.2, 47.1% female, and 70.6% stage I-II) who had diagnostic CT images in The Cancer Image Archive. All patients had the 12th thoracic vertebra (T12) image, and a subset (62 patients) had the 3rd lumber vertebra (L3) image. Paravertebral muscle areas on T12 and skeletal muscle and adipose tissue areas on L3 were annotated using Slice-O-Matic. RNA-seq data were provided by The Cancer Genome Atlas and Clinical Proteomic Tumor Analysis Consortium; percentages of CD8, regulatory T cells, and activated NK cells were identified using the CIBERSORT. ESTIMATE algorithm was used to derive the stromal score and the immune score. Differences in the immune markers were examined using ANOVA adjusting for stage, histology, and study.
Results and Conclusion: Patients with higher paravertebral muscle area (3rd tertile) had the lowest stromal scores, compared to the 2nd and 1st tertile (P<0.05). Patients in the 2nd tertile of paravertebral muscle areas had the highest immune score and CD274 (PD-L1) gene expression. Among the body composition types classified using L3 images, low muscle/high adiposity was associated with lower stromal scores, and low muscle was associated with lower immune scores, compared to high adiposity and high muscle/low adiposity types. Other immunological markers did not differ across the body composition types.
Significance: These findings suggest associations between deconvoluted skeletal and adipose tissue components and tumor markers relevant to immune checkpoint inhibitor efficacies in NSCLC. Further validation using immune phenotyping in a large patient sample is warranted. Funding: The study is in part supported by NIH/NCI R37CA248371 and OSU Comprehensive Cancer Center - James.
Citation Format: Ting-Yuan David Cheng, Cuthbert Mario Mahenge, Rand T. Akasheh, Ayse Selen Yilmaz, Ben Kinder, Xuan Nguyen, Maciej Pietrzak, Carolyn J. Presley, Peter G. Shields. CT-assessed body composition and tumor immunologic characteristics in patients with non-small-cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3405
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