Chronic multiple pulmonary emboli. Regional response of the bronchial circulation

In pulmonary embolism, the bronchial circulation can dramatically increase perfusion to the lung and prevent infarction. The physiology of this response is incompletely understood. The authors studied the regional changes in the bronchial circulation in an animal model after multiple chronic pulmonary emboli to the periphery of one lung. The gross anatomy of the bronchial circulation was studied using Batson's solution to produce vascular casts of the pulmonary and bronchial circulations. These casts were prepared in a normal sheep and in a sheep with multiple chronic microemboli in the periphery of one lung. The normal bronchial arteries are visible as threadlike structures covering the surface of the tracheobronchial tree with ramifications extending to the lung periphery. In a sheep with multiple chronic microemboli, the bronchial arteries supply the pulmonary parenchyma deprived of pulmonary arterial flow. The bronchial arteries following pulmonary arterial embolization markedly dilate and are serpentine.     

Digital synthesis of lung nodules

Studies evaluating observer accuracy and visual perception of pulmonary nodules usually are based upon test films obtained from clinical practice in patients with proven pulmonary nodules. Unfortunately, such nodules do not always occur in the optimal size and location to facilitate testing. Such studies would be enhanced by the ability to place nodules of desired size and location on chest radiographs. This report describes a method of placing a computer-generated (synthesized) nodule on a digitized chest radiograph. To demonstrate the similarity of these synthesized nodules to real nodules, each digitized radiograph with a computer-generated nodule was paired with a digitized chest radiograph of a patient with a clinically proven pulmonary nodule. A total of 22 pairs of chest radiographs were then shown to 13 radiologists, who were asked to distinguish the synthesized nodule from the real nodule. With this two alternative forced-choice test, the radiologists were only able to distinguish the synthesized nodule in 51% of the cases, strongly suggesting that computer generated nodules may be used to simulate real pulmonary nodules in future tests of nodule detection.     

Pulmonary lymphangioleiomyomatosis: CT findings

Lymphangioleiomyomatosis, a rare disease occurring in women of childbearing age, is characterized by proliferation of smooth muscle in pulmonary lymphatic channels and mediastinal and abdominal lymph nodes. Chest radiographs typically reveal interstitial disease with normal lung volume. Pneumothorax and pleural effusions may be present. CT scans in eight patients with biopsy-proved pulmonary lymphangioleiomyomatosis were reviewed. The prominent feature of the disease was multiple thin-walled cysts throughout the lungs, best visualized on scans made with 1.5-mm collimation. Mediastinal and/or retrocrural lymphadenopathy, often not appreciated on the chest radiograph, was present in four of eight patients. CT can suggest a diagnosis of lymphangioleiomyomatosis when diagnosis by clinical presentation and chest radiographs is uncertain.     

Effects of image processing on nodule detection rates in digitized chest radiographs: ROC study of observer performance

To evaluate the effects of image processing in digitized chest radiographs when high-resolution images are used, an examination was done in which the detection of pulmonary nodules in unprocessed digitized chest radiographs was compared with that in images that had undergone processing with two methods, adaptive filtration and histogram equalization. The processing techniques have been optimized in previous work to selectively enhance the retrocardiac and subdiaphragmatic areas without significant alteration of detail in the lung. Eight observers were shown 150 test radiographs (50 unprocessed, 50 processed with adaptive filtration, 50 processed with histogram equalization) containing 150 nodules. The results indicate a statistically significant (P less than .03) difference, with highest observer performance in the chest radiographs processed with adaptive filtration (median area under ROC curve = 0.78), compared with unprocessed images (median = 0.68) and chest radiographs processed with histogram equalization (median = 0.62). Performance in the lung was not significantly different. Adaptive filtration applied to selectively enhance underexposed areas of film images may improve nodule detection. Histogram equalization provided no improvement in performance.     

Semi-automated 3D segmentation of major tracts in the rat brain: comparing DTI with standard histological methods

Researchers working with rodent models of neurological disease often require an accurate map of the anatomical organization of the white matter of the rodent brain. With the increasing popularity of small animal MRI techniques, including diffusion tensor imaging (DTI), there is considerable interest in rapid segmentation methods of neurological structures for quantitative comparisons. DTI-derived tractography allows simple and rapid segmentation of major white matter tracts, but the anatomic accuracy of these computer-generated fibers is open to question and has not been rigorously evaluated in the rat brain. In this study, we examine the anatomic accuracy of tractography-based segmentation in the adult rat brain. We analysed 12 major white matter pathways using semi-automated tractography-based segmentation alongside manual segmentation of Gallyas silver-stained histology sections. We applied four fiber-tracking algorithms to the DTI data—two integration methods and two deflection methods. In many cases, tractography-based segmentation closely matched histology-based segmentation; however different tractography algorithms produced dramatically different results. Results suggest that certain white matter pathways are more amenable to tractography-based segmentation than others. We believe that these data will help researchers decide whether it is appropriate to use tractography-based segmentation of white matter structures for quantitative DTI-based analysis of neurologic disease models.     

Performance of high-resolution monitors for digital chest imaging

High-resolution cathode-ray tubes (CRT's) are currently the most viable soft-copy display for digital radiography. We present here methods for measuring large-area contrast ratio and detail contrast ratio. A two-dimensional charge coupled device (ccd) array signal-averaged with a video frame buffer permits linear microradiometric measure of individual beam lines. Results from three different 1000-line monitors demonstrate the shift variance of resolution. The detail contrast ratio (or modulation depth) was found to vary from 100% to less than 10% across the face of one CRT. Dynamic focus in both the horizontal and vertical deflection circuitry proved effective in reducing this shift variance. Comparisons of three phosphors demonstrate the utility of long persistence phosphors (P164) for static display in producing brighter images with less flicker. Recommendations for CRT design and selection for high-resolution digital radiography are included.     

Restructuring of an evidence-based practice curriculum and assessment with structural mapping by course outcome verb

ObjectiveAn evidence-based clinical practice (EBCP) subcurriculum within a chiropractic curriculum was restructured to distribute EBCP topics to courses throughout the curriculum. We posited that this would enhance student learning through early exposure, repetition, and the use of progressively more difficult levels of learning. In this paper we describe how we determined if Bloom''s verb level trended upward from the beginning of the curriculum to the end and if there were any gaps in presentation of topics periodically in the curriculum. We describe how we determined if the restructured subcurriculum provided adequate integration of topics.MethodsEBCP committee chairs created templates of the new structure, solicited feedback from the faculty, and faculty members volunteered to assimilate topics into courses. Support for the faculty included comprehensive PowerPoint production and in-service training. Assessment for trends and gaps was performed of the resultant learning outcomes by mapping 13 quarters against 6 Bloom''s verb levels for 19 topics.ResultsFourteen of the topics had increasing linear model trends indicating verb progression. Decreased attention to EBCP topics was identified in some quarters.ConclusionThe graphical mapping process seemed useful to find EBCP topics that did not show progression of Bloom''s verb difficulty and gaps in topics in the restructured subcurriculum.     

Image optimization in a computed-radiography/photostimulable-phosphor system

Photostimulable phosphor imaging is an exciting new technology that has several advantages over film/screen radiography, the most important of which is the linearity of the photostimulable phosphor system over a wide exposure latitude. The photostimulable phosphor image is digital, and as such, provides options of how the image is viewed by radiologists. This report discusses the various image-processing parameters available for a photostimulable phosphor system and describes a rational approach for selecting these parameters in portable chest radiography. As photostimulable phosphor imaging becomes more widely implemented, an understanding of the processing parameters will facilitate the production of images that take full advantage of the benefits of these systems.