Faculty Bibliography

Early detection of lung nodules is an important clinical indication for obtaining routine CT studies of the thorax. To date, research has focused on the sensitivity of computer-aided diagnosis (CAD) compared with expert chest radiologists typically using data obtained from single detector CT scanners. The present study focuses on the use of CAD as a second reader supplementing four nonexpert "community level" radiologists using state-of-the-art multidetector high resolution data sets. Evaluations of 18 cases with a total of 87 nodules (average 4.8 per case) were subsequently validated by a panel of two expert dedicated chest radiologists. Only 21% of nodules were identified by all four readers; 17% were identified only by CAD. The mean sensitivity of readers before CAD was 49% while following CAD this improved to 72% (p<0.001). When analyzed by individual lobes, the percentage of these in which nodules could be identified increased from 36% prior to CAD to 44% following CAD (p<0.001). These data support the use of CAD as a second reader specifically for nonexpert radiologists in general clinical practice. (C) 2004 CARS and Elsevier B.V. All rights reserved

Three-dimensional methods for quantifying pulmonary nodule volume at computed tomography (CT) and the effect of imaging variables were studied by using a realistic phantom. Two fixed-threshold methods, a partial-volume method (PVM) and a variable method, were used to calculate volumes of 40 plastic nodules (largest dimension, <5 mm: 20 nodules with solid attenuation and 20 with ground-glass attenuation) of known volume. Tube current times (20 and 120 mAs), reconstruction algorithms (high and low frequency), and nodule characteristics were studied. Higher precision was associated with use of a PVM with predetermined pure nodule attenuation, high-frequency algorithm, and diagnostic CT technique (120 mAs). A PVM is promising for volume quantification and follow-up of nodules

We developed an automated system for registering computed tomography (CT) images of the chest temporally. Our system detects anatomical landmarks, in particular, the trachea, sternum and spine, using an attenuation-based template matching approach. It computes the optimal rigid-body transformation that aligns the corresponding landmarks in two CT scans of the same patient. This transformation then provides an initial registration of the lung surfaces segmented from the two scans. The initial surface alignment is refined step by step in an iterative closest-point (ICP) process. To establish the correspondence of lung surface points, Elias' nearest neighbor algorithm was adopted. Our method improves the processing time of the original ICP algorithm from O(kn log n) to O(kn), where k is the number of iterations and n the number of surface points. The surface transformation is applied to align nodules in the initial CT scan with nodules in the follow-up scan. For 56 out of 58 nodules in the initial CT scans of 10 patients, nodule correspondences in the follow-up scans are established correctly. Our methods can therefore potentially facilitate the radiologist's evaluation of pulmonary nodules on chest CT for interval growth

PURPOSE: To assess the effect of using a lossy Joint Photographic Experts Group standard for wavelet image compression, JPEG2000, on pulmonary nodule detection at low-dose computed tomography (CT). MATERIALS AND METHODS: One hundred sets of lung CT data ('cases') were compressed to 30:1, 20:1, and 10:1 levels by using a wavelet-based JPEG2000 method, resulting in 400 test cases. Each case consisted of nine 1.25-mm sections that had been obtained with 20-40 mAs. Four thoracic radiologists independently interpreted the test case images. Performance was measured by using area under the receiver operating characteristic (ROC) curve (Az) and conventional sensitivity and specificity analyses. RESULTS: There were 51 cases with and 49 without lung nodules. Az values were 0.984, 0.988, 0.972, 0.921, respectively, for original and 10:1, 20:1, and 30:1 compressed images. Az values decreased significantly at 30:1 (P =.014) but not at 10:1 compression, with a trend toward significant decrease at 20:1 (P =.051). Specificity values were unaffected by compression (>98.0% at all compression levels). Sensitivity values were 86.3% (176 of 204 test cases with nodules), 77.9% (159 of 204 cases), 76.5% (156 of 204 cases), and 70.1% (143 of 204 cases), respectively, for original and 10:1, 20:1, and 30:1 compressed images. Results of logistic regression model analysis confirmed the significant effects of compression rate and nodule attenuation, size, and location on sensitivity (P <.05). CONCLUSION: While no reduction in nodule detection at 10:1 compression levels was demonstrated by using ROC analysis, a significant decrease in sensitivity was identified. Further investigation is needed before widespread use of image compression technology in low-dose chest CT can be recommended

The ability to identify and characterize pulmonary nodules has been dramatically increased by the introduction of multislice CT (MSCT) technology. Using high-resolution sections, MSCT allows considerable improvement in assessing nodule morphology, enhancement patterns, and growth. MSCT also has facilitated the development and potential of clinical application of computer-assisted diagnosis

OBJECTIVE: Our purpose was to describe three adult patients in whom we found increased thymic uptake of FDG on positron emission tomography and thymic enlargement with convex lateral margins on CT. Subsequent biopsy or resection showed normal thymic tissue. CONCLUSION: In three adults, we found a physiologic uptake of FDG by the thymus with standardized uptake values in the range of thymic neoplasia

Air trapping is a prominent finding in small airway disease (SAD)of the lungs. To investigate the feasibility of accurate, automated assessment of air-trapping from low-dose CT, we compare visual scoring by expert radiologists to a conventional method of automated assessment as well as two novel methods. The conventional method,the markdensity maskmark method, has been reported to correlateweakly but significantly with visual scoring on normal-dose CT.While we were unable to reproduce these results on our low-dose scans, our two novel methods showed some promise. More study on larger data sets is required to determine the optimal analysis method.

SUMMARY: A case of an immunocompetent patient with severe Aspergillus infection and radiographic findings typically described with angioinvasive aspergillosis is presented. When Aspergillus is isolated from the sputum in a patient with normal immunity, invasive aspergillosis should be considered when there are extensive radiographic findings characteristic of invasive fungal disease