Implementing lung cancer screening: the US experience.

The reduced lung cancer mortality observed with low-dose computed tomography (LDCT) screening in the National Lung Screening Trial (NLST) has led to annual screening in the United States as a covered benefit by both private insurers and the federal health insurance programme, the Centers for Medicare and Medicaid Services. Reimbursement for screening requires data submission to a federal registry on all individuals, whether privately or federally insured. Data must document individual patient eligibility as well as shared decision-making regarding the benefits and risks of LDCT screening, smoking cessation counselling, and the importance of annual screening. Beyond these requirements lie opportunities to maximise the benefits of screening in the radiology setting. Individuals eligible for screening account for a minority of those diagnosed with lung cancer in the US; the evidence needed to improve patient selection must be collected systematically for both screen-detected and incidentally detected lung nodules. Current nodule management and tracking guidelines reduce the false-positive rates observed in the NLST, but fall short in their ability to correctly classify nodules as benign or malignant. Smoking cessation is inadequately managed in most busy clinician practices. As a common nidus for tobacco-associated lung diseases, imagers are uniquely poised to collect the longitudinal data to better inform screening eligibility and to improve indeterminate nodule management, while maximising the setting of screening to motivate and provide smoking cessation. By re-engineering the notion of imaging practice, radiologists can be major contributors to lung cancer early detection and mortality reduction.

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.

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.

Problem-oriented prefetching for an integrated clinical imaging workstation.

Prefetching methods have traditionally been used to restore archived images from picture archiving and communication systems to diagnostic imaging workstations prior to anticipated need, facilitating timely comparison of historical studies and patient management. The authors describe a problem-oriented prefetching scheme, detailing 1) a mechanism supporting selection of patients for prefetching via characterizations of clinical problems, using multiple data sources (picture archiving and communication systems, hospital information systems, and radiology information systems), classifying patients into cohorts on the basis of their medical conditions (e.g., lung cancer); and 2) prefetching of multimedia data (imaging, laboratory, and medical reports) from clinical databases to enable the viewing of an integrated patient record. Preliminary evaluation of the prefetching algorithm using classic information retrieval measures showed that the system had high recall (100 percent), correctly identifying and retrieving data for all patients belonging to a target cohort, but low precision (50 percent). A key finding during testing was that the recall of the system was increased through the use of multiple data sources (compared with one data source), because of better patient descriptors. Medical problems and patient cohorts were more specifically defined by combining information from heterogeneous databases.

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.

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.

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.

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.

Pitfalls in the diagnosis of thoracic aortic dissection at CT angiography.

Two hundred seventy-five computed tomographic (CT) angiograms of the thoracic aorta were obtained over a period of approximately 4 years in patients with suspected or known aortic dissection. In all cases, unenhanced images were initially obtained, followed by contrast material-enhanced images. A variety of pitfalls were encountered that mimicked aortic dissection. These pitfalls were attributable to technical factors (eg, improper timing of contrast material administration relative to image acquisition); streak artifacts generated by high-attenuation material, high-contrast interfaces, or cardiac motion; periaortic structures (eg, aortic arch branches, mediastinal veins, pericardial recess, thymus, atelectasis, pleural thickening or effusion adjacent to the aorta); aortic wall motion and normal aortic sinuses; aortic variations such as congenital ductus diverticulum and acquired aortic aneurysm with thrombus; and penetrating atherosclerotic ulcer. Although several of these pitfalls are easy to recognize and therefore unlikely to present a diagnostic problem, others are potentially confusing. Familiarity with these common pitfalls, coupled with a knowledge of normal intrathoracic anatomy, will facilitate recognition of true aortic dissection and help avoid misdiagnosis at thoracic aortic CT angiography.

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.

Automated measurement of single and total lung volume from CT.

PURPOSE: The goal of this work was to develop an automated method for calculating single (SLV) and total (TLV) lung volumes from CT images. METHOD: Patients underwent volumetric CT scanning through the entire chest in a single breath-hold, as well as pulmonary function tests. An automated, knowledge-based system was developed to segment the lungs in the CT images. Image-processing routines were used to extract sets of voxels from the image data that were identified by matching them to anatomical objects defined in a model. SLV and TLV were calculated by summing included voxels. RESULTS: For 43 patients analyzed, TLV from CT and total lung capacity from body plethysmography were strongly correlated (r = 0.90). On average, the CT-derived volume of the left lung accounted for 47.2% of the total. CONCLUSION: A knowledge-based approach to segmentation of the lungs in CT can be used to automatically estimate SLV and TLV.

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.

The effects of co-occurrence matrix based texture parameters on the classification of solitary pulmonary nodules imaged on computed tomography.

In this project, patients with a solitary pulmonary nodule, were imaged using high resolution computed tomography. Quantitative measures of texture were extracted from these images using co-occurrence matrices. These matrices were formed with different combinations of gray level quantization, distance between pixels and angles. The derived measures were input to a linear discriminant classifier to predict the classification (benign or malignant) of each nodule. Using a relative quantization scheme with eight levels, four features yielded an area under the ROC curve (Az) of 0.992; 93.8% (30/32) of cases were correctly classified when training and testing on the same cases; while 90.6% (29/32) were correctly classified when jackknifing was used.

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.

Hyperad: augmenting and visualizing free text radiology reports.

Hyperad is an automated computer system designed to extract key concepts from thoracic radiology reports and give physicians access to a large database containing the reports and key concepts. The concepts are extracted from textual documents with natural language processing techniques, then stored with the original documents in the database, which can be queried in terms of findings or associated attributes from an intuitive and easily accessible interface. The extracted concepts are represented both textually in a coded hypertext format and graphically on a coronal cross-sectional anatomy atlas, an idealized graphical model of human anatomy. To facilitate implementation, the communication protocols and standards of the World Wide Web (Web) were adopted. The reports and associated forms are encoded in standard hypertext markup language, which makes it possible to use hypermedia links to navigate the Hyperad database with any graphical Web browser. In the future, Hyperad may prove useful for other applications.

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.

Development and testing of image-processing methods for the quantitative assessment of airway hyperresponsiveness from high-resolution CT images.

PURPOSE: Our goal was to develop a protocol and image-processing methods to quantitate both bronchial and lung attenuation changes in patients imaged with helical high-resolution CT (HRCT). METHOD: Human subjects underwent helical HRCT at two suspended breath-hold conditions, functional residual capacity and residual volume, at baseline and following methacholine-induced bronchoprovocation. A semiautomated contouring program was used to define anatomically like bronchi and axial lung sections from the different physiologic sequences, from which automated measurements of area, shape, and attenuation were made. Because the gray level threshold for contouring directly affects the measured area of an anatomic structure, two types of evaluation studies were performed. These included in vivo measurements using baseline parameters of human subjects as the standard of reference and in vitro measurements of a CT phantom designed to simulate the air-soft tissue interfaces of bronchi. RESULTS: Phantom tests showed that the minimum difference between actual and measured areas of holes occurred at a threshold of -500 HU. The smallest diameter holes were most sensitive to changes in threshold value. However, although absolute area measurements of both simulated and human bronchi varied with threshold level, the percent changes in airway areas between baseline and bronchoprovocation sequences were relatively stable at any given threshold. CONCLUSION: These image-processing tools provide reproducible measurements of area as well as attenuation characteristics of pulmonary structures and may offer insights into the practical use of functional imaging in evaluating conditions of airflow obstruction.

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.