Faculty Bibliography

The improvements to patient care that can be achieved by combining advanced imaging techniques and bronchoscopy are considerable. In this regard, CT imaging often plays an indispensable role in both the selection of appropriate candidates tor therapy as well as the choice of optimal interventional techniques. However, it is apparent that alternate methods for evaluating the airways and lung including ultrasound and electromagnetic navigation will likely play an increasingly important diagnostic role, necessitating a thorough understanding of their advantages and limitations. Disease-specific applications for which imaging technologies, including CT and VB, are either currently routinely used or show the greatest promise are for suspected or diagnosed lung cancers, central and peripheral, and emphysema. It may be anticipated that with growing experience, the potential for additional indications of these remarkable technologies are likely to increase in the near future

It has been known for several years that airflow limitations in the small airways may be an important contributor to Chronic Obstructive Pulmonary Disease (COPD). Quantification of wall thickness has lately gained attention thanks to the use of high resolution CT, with novel approaches focusing on automated methods that can substitute for visual assessment. While increased thickening of the wall is considered evidence of inflammatory disease, we hypothesize that there may be additional ways to detect and quantify inflammation, specifically, with the uptake of contrast material. In this preliminary investigation, we selected patients with documented chronic airway inflammation, and for whom pre and post contrast datasets were available. On targeted reconstruction of right upper and lower lobes, we selected airways with minimal connections to surrounding structures, and used a modified Full-Width-Half-Max method for quantification of lumen diameter, wall thickness, and wall density. Matching airway locations on the pre- and post-contrast cases were compared. Airways from patients without airway disease served as a control. Results for the airway disease cases showed an average enhancement of 72 HU +/- 59 HU within the airway walls. In the control group the average enhancement was 16 HU +/- 22 HU. While this study is limited in number of cases, we hypothesize that quantification of contrast uptake is an additional factor that could be considered in assessing airway inflammation. Simultaneously, we are currently investigating whether enhancement can be measured via a 'contrast' map created with dual energy scanning, where a 3-value decomposition algorithm differentiates iodine from other materials. This technique would eliminate both the need for a pre-contrast scan, and the task of matching airway locations on pre- and post- scans

Pulmonary nodule characterization is currently being redefined as new clinical, radiologic, and pathologic data are reported, necessitating a reevaluation of the clinical management, especially of subsolid nodules. These are now known to frequently, although not invariably, fall into the spectrum of peripheral adenocarcinomas of the lung. Strong correlation between the Noguchi histologic classification and computed tomographic (CT) appearances of these lesions, in particular, has been reported. Serial CT findings have further documented that stepwise progression of lesions with ground-glass opacity, manifested as an increase in size or the appearance and/or subsequent increase of solid components, does occur in a select subset of patients. As a consequence, recognition of the potential association between subsolid nodules and peripheral adenocarcinomas requires a review of current guidelines for the management of these lesions, further necessitated by a differential diagnosis that includes benign lesions such as focal inflammation, focal fibrosis, and organizing pneumonia. Specific issues that need to be addressed are the need for consensus regarding an appropriate CT classification, methods for precise measurement of subsolid nodules, including the extent of both ground-glass and solid components, as well as accurate assessment of the growth rates as means for predicting malignancy and prognosis. It is anticipated that interim guidelines may serve to standardize our current management of these lesions, pending further clarification of their natural history. (c) RSNA, 2009

The purpose of this review was to evaluate the accuracy of SPECT in acute pulmonary embolism. Sparse data are available on the accuracy of SPECT based on an objective reference test. Several investigations were reported in which the reference standard for the diagnosis of pulmonary embolism was based in part on the results of SPECT or planar ventilation-perfusion (V/Q) imaging. The sensitivity of SPECT in all but one investigation was at least 90%, and specificity also was generally at least 90%. The sensitivity of SPECT in 4 of 5 investigations was higher than that of planar V/Q imaging. The specificity of SPECT was generally higher, equal, or only somewhat lower than that of planar V/Q imaging. Most investigators reported nondiagnostic SPECT V/Q scans in no more than 3% of cases. Methods of obtaining SPECT images, methods of obtaining planar V/Q images, and the criteria for interpretation varied. The general impression is that SPECT is more advantageous than planar V/Q imaging.