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Biomedical subjects

D R Aberle

Publications and source records attributed to D R Aberle.

At least 19 recordsLinked to original sources
PubMed2001

A consensus statement of the Society of Thoracic Radiology: screening for lung cancer with helical computed tomography.

This consensus statement by the Society of Thoracic Radiology is a summary of the current understanding of low dose computed tomography (CT) for screening for lung cancer. Lung cancer is the most common fatal malignancy in the industrialized world. Unlike the next three most common cancers, screening for lung cancer is not currently recommended by cancer organizations. Improvements in CT technology make lung screening feasible. Early prevalence data indicate that about two-thirds of lung cancers that are detected by CT screening are at an early stage. Other data support the postulate that patients with lung cancers detected at this early stage have better rates of survival. Whether this will translate into an improved disease specific mortality is yet to be demonstrated. The suggested technical protocols, selection criteria, and method of handling the numerous benign nodules that are detected are discussed. It is the consensus of this committee that mass screening for lung cancer with CT is not currently advocated. Suitable subjects who wish to participate should be encouraged to do so in controlled trials, so that the value of CT screening can be ascertained as soon as possible.

Humans↗
PubMed2001

The effect of imaging modality on patient management in the evaluation of pulmonary thromboembolism.

A retrospective medical record review was performed to study the differences in clinical risk profiles and the relationships between test results versus management for suspected pulmonary thromboembolism (TE) in patients undergoing either radionuclide ventilation perfusion (V/Q) scans or pulmonary computed tomographic angiography (CTA), as the initial test. Data of 138 consecutive V/Q patients were compared with that of 149 consecutive CTA patients during equivalent 6-month intervals before and after the introduction of CTA. Information on risk factors, signs and symptoms, all diagnostic test results, and the relationships between the test results and ultimate physician management were collected and analyzed. V/Q results predicted physician management in all patients with high probability scans and 91% with normal to low probability scans. There were 35 patients with indeterminate V/Q scans--43% of these patients were managed without any other diagnostic test. CTA results predicted management in all patients with positive studies and 99% of patients with negative studies. In contrast to the V/Q cohort, only seven CTA studies were inconclusive--additional diagnostic tests determined management in all but one case. Compared with V/Q, CTA has fewer indeterminate results, is more directly reflective of management, and reduces the number of patients managed with inconclusive data.

Algorithms↗
PubMed2001

Patient-specific models for lung nodule detection and surveillance in CT images.

The purpose of this work is to develop patient-specific models for automatically detecting lung nodules in computed tomography (CT) images. It is motivated by significant developments in CT scanner technology and the burden that lung cancer screening and surveillance imposes on radiologists. We propose a new method that uses a patient's baseline image data to assist in the segmentation of subsequent images so that changes in size and/or shape of nodules can be measured automatically. The system uses a generic, a priori model to detect candidate nodules on the baseline scan of a previously unseen patient. A user then confirms or rejects nodule candidates to establish baseline results. For analysis of follow-up scans of that particular patient, a patient-specific model is derived from these baseline results. This model describes expected features (location, volume and shape) of previously segmented nodules so that the system can relocalize them automatically on follow-up. On the baseline scans of 17 subjects, a radiologist identified a total of 36 nodules, of which 31 (86%) were detected automatically by the system with an average of 11 false positives (FPs) per case. In follow-up scans 27 of the 31 nodules were still present and, using patient-specific models, 22 (81%) were correctly relocalized by the system. The system automatically detected 16 out of a possible 20 (80%) of new nodules on follow-up scans with ten FPs per case.

Automation↗
PubMed2001

Spiral versus electron-beam CT for coronary artery calcium scoring.

PURPOSE: To determine differences in coronary artery calcium detection, quantification, and reproducibility, as measured at electron-beam computed tomography (CT) and subsecond spiral CT with retrospective electrocardiogram gating in an asymptomatic adult population. MATERIALS AND METHODS: Seventy subjects asymptomatic for coronary heart disease underwent both electron-beam CT and subsecond spiral CT. In all subjects, two images each were obtained with both scanners. Two experienced readers using three different algorithms scored each of the four scans: one score for the electron-beam CT images and two scores for the spiral CT images. RESULTS: With a 130-HU threshold for the quantification of calcium, there were no significant differences in interscan and interobserver variation in calcium scores between the electron-beam CT and spiral CT images. There was greater interobserver (P <.001) and interscan (P <.03) variation in scores when a 90-HU threshold was used for spiral CT images. With a 130-HU threshold, when calcium scores were used for clinical risk stratification, there was a significant difference between the results obtained with electron-beam CT and those obtained with spiral CT (P <.05). CONCLUSION: Spiral CT has not yet proved to be a feasible alternative to electron-beam CT for coronary artery calcium quantification. There are systematic differences between calcium scores obtained with single-detector array subsecond spiral CT and those obtained with electron-beam CT.

Adult↗
PubMed2000

Contemporary cardiac imaging: an overview.

Comprehensive cardiac assessment embraces virtually every imaging modality and includes information about coronary vascular anatomy as well as cardiac morphology, function, perfusion, metabolism, and tissue characterization. Through sophisticated computer processing and image analysis, newer imaging technologies such as computed tomography (CT), magnetic resonance (MR), MR spectroscopy, and positron emission tomography now provide quantitative information that may obviate more invasive angiographic assessment. Currently, no single imaging technology realizes all questions relating to cardiac form and function, and many of the technologies overlap in the content and quality of information they provide. This overview seeks to provide a broad perspective on current cardiac imaging, articulating the benefits of various technologies and their limitations.

Aorta↗
PubMed2000

Knowledge-based segmentation of thoracic computed tomography images for assessment of split lung function.

The assessment of differential left and right lung function is important for patients under consideration for lung resection procedures such as single lung transplantation. We developed an automated, knowledge-based segmentation algorithm for purposes of deriving functional information from dynamic computed tomography (CT) image data. Median lung attenuation (HU) and area measurements were automatically calculated for each lung from thoracic CT images acquired during a forced expiratory maneuver as indicators of the amount and rate of airflow. The accuracy of these derived measures from fully automated segmentation was validated against those from segmentation using manual editing by an expert observer. A total of 1313 axial images were analyzed from 49 patients. The images were segmented using our knowledge-based system that identifies the chest wall, mediastinum, trachea, large airways and lung parenchyma on CT images. The key components of the system are an anatomical model, an inference engine and image processing routines, and segmentation involves matching objects extracted from the image to anatomical objects described in the model. The segmentation results from all images were inspected by the expert observer. Manual editing was required to correct 183 (13.94%) of the images, and the sensitivity, specificity, and accuracy of the knowledge-based segmentation were greater than 98.55% in classifying pixels as lung or nonlung. There was no significant difference between median lung attenuation or area values from automated and edited segmentations (p > 0.70). Using the knowledge-based segmentation method we can automatically derive indirect quantitative measures of single lung function that cannot be obtained using conventional pulmonary function tests.

Algorithms↗
PubMed1999

Comparative effects of hydrofluoroalkane and chlorofluorocarbon beclomethasone dipropionate inhalation on small airways: assessment with functional helical thin-section computed tomography.

A double-blind, randomized, parallel-group pilot study compared the relative efficacy of hydrofluoroalkane-134a beclomethasone dipropionate (HFA-BDP [QVAR]; mass median aerodynamic diameter, 0. 8-1.2 m) versus cholorofluorocarbon-11/12 BDP (CFC-BDP [Beclovent]; mass median aerodynamic diameter, 3.5-4.0 m) in 31 steroid naive patients with mild to moderate asthma (PC(20,) 4 mg/mL). Functional high-resolution computed tomography was used to assess the relative efficacy of HFA-BDP and CFC-BDP on regional air trapping, as an indirect measure of small airways function and on regional hyperreactivity. Pretreatment functional computed tomography was performed at residual volume before and after methacholine challenge. After 4 weeks of treatment, functional imaging was repeated before and after the same concentration of methacholine that was administered before the treatment (n = 19 patients). Quantitative assessment of changes in distribution of lung attenuation was performed. After 4 weeks of treatment, the HFA-BDP group showed significantly more improvement in air trapping overall (a shift in the lung attenuation curve at residual volume toward more attenuation) on the posttreatment computed tomography scan (P <.05; Fisher's Exact Test). After an equal constrictor stimulus (methacholine concentration), subjects treated with HFA-BDP (n = 10 patients) showed less increase in air trapping overall than subjects treated with CFC-BDP (n = 9 patients) on the posttreatment scans compared with the pretreatment scans (P <.001; Fisher's Exact Test). No significant difference was demonstrated between the 2 treatment groups with respect to improvement in symptoms, spirometry, or methacholine responsiveness assessed by FEV(1), except for a greater reduction in breathlessness in the HFA-BDP group (P <.05). We conclude that HFA-BDP may have greater efficacy in the peripheral airways and that this effect is better assessed with functional imaging computed tomography techniques than with conventional physiologic tests.

Administration, Inhalation↗
PubMed1999

A pattern classification approach to characterizing solitary pulmonary nodules imaged on high resolution CT: preliminary results.

The purpose of this research is to characterize solitary pulmonary nodules as benign or malignant based on quantitative measures extracted from high resolution CT (HRCT) images. High resolution CT images of 31 patients with solitary pulmonary nodules and definitive diagnoses were obtained. The diagnoses of these 31 cases (14 benign and 17 malignant) were determined from either radiologic follow-up or pathological specimens. Software tools were developed to perform the classification task. On the HRCT images, solitary nodules were identified using semiautomated contouring techniques. From the resulting contours, several quantitative measures were extracted related to each nodule's size, shape, attenuation, distribution of attenuation, and texture. A stepwise discriminant analysis was performed to determine which combination of measures were best able to discriminate between the benign and malignant nodules. A linear discriminant analysis was then performed using selected features to evaluate the ability of these features to predict the classification for each nodule. A jackknifed procedure was performed to provide a less biased estimate of the linear discriminator's performance. The preliminary discriminant analysis identified two different texture measures--correlation and difference entropy--as the top features in discriminating between benign and malignant nodules. The linear discriminant analysis using these features correctly classified 28/31 cases (90.3%) of the training set. A less biased estimate, using jackknifed training and testing, yielded the same results (90.3% correct). The preliminary results of this approach are very promising in characterizing solitary nodules using quantitative measures extracted from HRCT images. Future work involves including contrast enhancement and three-dimensional measures extracted from volumetric CT scans, as well as the use of several pattern classifiers.

Biophysical Phenomena↗
PubMed1998

Airway hyperreactivity: assessment with helical thin-section CT.

PURPOSE: To determine the accuracy of helical computed tomography (CT) for assessing reversible changes in bronchial size and air trapping due to airway hyperreactivity. MATERIALS AND METHODS: Spirometry and helical CT were performed in 15 patients with mild asthma and six healthy control subjects before and after bronchial provocation with methacholine chloride and after reversal of provocation with albuterol. CT was performed at suspended functional residual capacity and at residual volume in two lung regions (above and below the carina). Bronchial area and lung attenuation measurements were compared. RESULTS: At baseline, lung attenuation frequency distribution curves were similar between the control and asthma groups. After methacholine, control subjects showed a decrease of less than 10% in the forced expiratory volume at 1 second (FEV1) and no significant differences in lung attenuation curves. Patients with asthma showed a 20%-36% decrease in FEV1, with significant decreases in the median and lowest 10th percentile regions of the attenuation curves and in the cross-sectional area of small (< 5-mm2) airways (P < .001 for all comparisons). After albuterol, control subjects showed no change in spirometric measurements, lung attenuation, or bronchial size, whereas all such parameters returned to baseline levels in patients with asthma. CONCLUSION: Functional helical CT can accurately demonstrate reversible airflow obstruction resulting from airway hyperreactivity.

Adolescent↗
PubMed1998

The evolution of an integrated timeline for oncology patient healthcare.

The introduction of computers in the medical environment has contributed to the proliferation of medical data, often making it difficult to consolidate information on a single patient. In patients with complex medical problems, such as oncology patients, the lack of data integration can negatively impact on patient care. This paper presents an infrastructure for the creation of an integrated multimedia timeline that automatically combines patient information from distributed hospital information sources, and creates a visual summary of pertinent events in a patient's medical history. In this prototype, we focus on oncology patients under treatment for advanced cancers.

Database Management Systems↗
PubMed1997

CT of pulmonary thromboembolism.

Conventional incremental CT has for many years been useful in the fortuitous diagnosis of pulmonary thromboembolic disease, allowing for visualization of both the central occluding thrombus and the pleuroparenchymal sequelae. Unfortunately, the slow data acquisition times precluded the inclusion of conventional CT in diagnostic algorithms for the diagnosis of this disease. The development and increasing availability of fast scanning techniques, namely helical (spiral) CT and electron-beam CT, now provide a noninvasive means of consistently and accurately demonstrating acute and chronic pulmonary arterial thrombus to the segmental level. CT has the added advantage over ventilation-perfusion scanning and pulmonary angiography of depicting unsuspected intrathoracic disease that may account for the patient's presenting illness.

Acute Disease↗
PubMed1997

Functional imaging of the airways.

The use of traditional pulmonary function tests (PFT) to assess airflow obstruction is limited by the fact that these measurements are global and can neither express the potential regional heterogeneity nor localize the distribution of airways involved. High-resolution computed tomography (HRCT) is an established technique for the detailed evaluation of the pulmonary parenchyma. The development of helical scanning techniques enables volume datasets to be acquired through regions of interest in a single breathhold. Acquired during different phases of suspended respiration or under different physiologic conditions, these image sets provide potential insights into the relationships between airway structure and function. Volumetric data in also amenable to advance image processing algorithms enabling more precise characterization of bronchial morphology. This review considers the challenge of assessing cardiopulmonary function due to the complexity of the heart and lungs. The considerable insights that have been gained about airway physiology in animal experimentation are discussed. Studies investigating the role of volume acquisition's Helical CT and Electron Beam CT techniques of evaluating functional small airways function in humans are reviewed in detail and potential methods for analysis of airflow obstruction and detection of airway reactivity are extensively considered.

Animals↗
PubMed1997

Method for segmenting chest CT image data using an anatomical model: preliminary results.

We present an automated, knowledge-based method for segmenting chest computed tomography (CT) datasets. Anatomical knowledge including expected volume, shape, relative position, and X-ray attenuation of organs provides feature constraints that guide the segmentation process. Knowledge is represented at a high level using an explicit anatomical model. The model is stored in a frame-based semantic network and anatomical variability is incorporated using fuzzy sets. A blackboard architecture permits the data representation and processing algorithms in the model domain to be independent of those in the image domain. Knowledge-constrained segmentation routines extract contiguous three-dimensional (3-D) sets of voxels, and their feature-space representations are posted on the blackboard. An inference engine uses fuzzy logic to match image to model objects based on the feature constraints. Strict separation of model and image domains allows for systematic extension of the knowledge base. In preliminary experiments, the method has been applied to a small number of thoracic CT datasets. Based on subjective visual assessment by experienced thoracic radiologists, basic anatomic structures such as the lungs, central tracheobronchial tree, chest wall, and mediastinum were successfully segmented. To demonstrate the extensibility of the system, knowledge was added to represent the more complex anatomy of lung lesions in contact with vessels or the chest wall. Visual inspection of these segmented lesions was also favorable. These preliminary results suggest that use of expert knowledge provides an increased level of automation compared with low-level segmentation techniques. Moreover, the knowledge-based approach may better discriminate between structures of similar attenuation and anatomic contiguity. Further validation is required.

Computer Simulation↗
PubMed1996

A concept-based retrieval system for thoracic radiology.

Current digital information systems in radiology are insufficient to accommodate the retrieval needs of academicians. Significant efforts are required in retrieving clinical cases for teaching and research. We describe a prototype system that supports intelligent case retrieval based on a combined specification of patient demographics, radiologic findings, and pathologic diagnoses. The documents for these cases can be distributed among multiple heterogeneous data bases. The system features automatic indexing of radiology and pathology reports, a comprehensive lexicon for thoracic radiology, an interface to a hospital information system, radiology information system, and picture archiving and communication systems, and a graphical user interface for query formulation and results visualization. The prototype system was developed within the domain of thoracic radiology involving patients with lung cancer.

Abstracting and Indexing↗
PubMed1996

Detection of simulated lung nodules with computed radiography: effects of nodule size, local optical density, global object thickness, and exposure.

RATIONALE AND OBJECTIVES: We quantified differences in the detection of simulated lung nodules on computed radiographs on the basis of variations in nodule size, local contrast, body habitus (global contrast), and exposure. METHODS: A step-wedge phantom was developed to simulate the attenuation ranges of the lung, retrocardiac, and subdiaphragmatic regions of the adult human chest. Additional Lucite wedges were used to simulate two different body thicknesses and to provide variable structural noise. Soft-tissue-equivalent nodules of 3-mm and 5-mm diameter that resulted in 10% differences in attenuation from lung equivalence were embedded in lung-equivalent material. By superimposing the sheets in various positions, 84 unique nodule configurations containing eight nodules per image were exposed on a computed radiography system. Computed radiographs were acquired at two different exposures approximating standard exposure and underexposure. For each resulting phantom image, seven observers scored the presence or absence of a nodule within individual cells of a 5 x 5 grid matrix. RESULTS: True-positive fractions for 3-mm-diameter nodules were very low across all conditions. True-positive fractions for 5-mm-diameter nodules varied from 0.23 to 0.98. Significant differences in the conspicuity of 5-mm nodules depended on differences in phantom thickness and differences in the locations of nodules within lung-, retrocardiac-, or subdiaphragmatic-equivalent regions. Accuracy in detecting nodules was significantly lower at lower exposures when nodules were located in the subdiaphragmatic-equivalent region. CONCLUSION: On computed radiographs, small nodules (5-mm diameter) can be reliably detected when they are located in areas of high or moderate surrounding local contrast, such as the lung or mediastinal regions. Detection of nodules decreases in regions of lower optical density corresponding to the subdiaphragmatic regions of the chest. The decrease in nodule detectability is greatest under conditions that simulate large body thickness and underexposure.

Adult↗
PubMed1996

Integrated multimedia timeline of medical images and data for thoracic oncology patients.

A prototype multimedia medical database has been developed to provide image and textual data for thoracic oncology patients undergoing treatment of advanced malignancies. The database integrates image data from the hospital picture archiving and communication system with textual reports from the radiology information system, alphanumeric data contained in the hospital information system, and other electronic medical data. The database presents information in a timeline format and also contains visualization programs that permit the user to view and annotate radiographic measurements in tabular or graphic form. The database provides an efficient and intuitive display of the changing status of oncology patients. The ability to integrate, manage, and access relevant multimedia information may substantially enhance communication among distributed multidisciplinary health care providers and may ensure greater consistency and completeness of patient-related data.

Databases, Factual↗