Angiographic magnetic resonance color composites of the normal brain and its vasculature.

Vascular magnetic resonance imaging (MRI) has become an important noninvasive adjunct to conventional cerebral MRI studies. To detect parenchymal changes associated with vascular anomalies, optimal diagnostic evaluation requires the comparison of both spin-echo and angiographic gradient-echo MRIs. To compress image data into a single 24-bit color image possessing the combined tissue contrast characteristics of both conventional spin-echo "black-blood" images and flow-sensitive gradient-echo "bright-blood" images, the red-green-blue color model and computer-based image-processing software were used to generate composites of MRI sets in which blood appears bright red while many stationary tissues possess near-natural colors. This technique may have potential applicability to human cerebrovascular MRI.

Composite and classified color display in MR imaging of the female pelvis.

Because of its superior soft-tissue-imaging capabilities, MRI has proved to be an excellent modality for visualizing the contents of the female pelvis. In an effort to potentially improve gynecological MRI studies, we have applied color composite techniques to sets of spin-echo and gradient-echo gray-tone MR images obtained from various individuals. For composite generation, based on tissue region of interest calculated mean pixel intensity values, various colors were applied to spatially aligned images using a DEC MicroVAX II computer with interactive digital language (IDL) so that tissue contrast patterns could be optimized in the final image. The IDL procedures, which are similar to those used in NASA's LANDSAT image processing system, allowed the generation of single composite images displaying the combined information present in a series of spatially aligned images acquired using different pulse sequences. With our composite generation techniques, it was possible to generate seminatural-appearing color images of the female pelvis that possessed enhanced conspicuity of specific tissues and fluids. For comparison with color composites, classified images were also generated based on computer recognition and statistical separation of distinct tissue intensity patterns in an image set using the maximum likelihood processing algorithm.

Generation of color composites for enhanced tissue differentiation in magnetic resonance imaging of the brain.

Currently, the diagnostic interpretation of magnetic resonance (MR) images requires that radiologists integrate specific tissue contrast information from several different images obtained at the same anatomic slice position. Each of these images has its own unique tissue contrast patterns which are based on the image acquisition parameters (pulse sequence) selected. The complex contrast patterns observable in these images reflect the inherent biophysical characteristics of the tissues and fluids present in the imaged section. In an effort to increase the diagnostic accuracy and efficiency of MR image interpretation, we have generated color composite images from quantitatively analyzed achromatic MR images of the brain, obtained while utilizing different pulse sequences. By using a DEC MicroVAX II computer with Interactive Digital Language (IDL), this color display method has been applied to images obtained from General Electric Signa and Siemens Magnatom imagers. For this study, our image sets included T1-weighted, T2-weighted, and proton density spin echo sequences as well as both high and low flip angle gradient echo sequences. Advantages of our color composite methods, in contrast to many other image processing techniques that have been described, are that minimal information is lost, computer misclassification of tissues is avoided, and the conspicuity of specific tissues is enhanced. Furthermore, with this method it is possible to produce composite images whose color renditions approach a natural anatomic tissue appearance. Availability of these color composites to radiologists may improve the efficiency and accuracy of the diagnostic interpretation of MR images.

PC-based multiparameter full-color display for tissue segmentation in MRI of adnexal masses.

OBJECTIVE: Our purpose was to apply full-color composite generation methods to multiparameter MRI to assess the ability of the technique to quantitatively segment clinically important anatomic and pathologic tissues. MATERIALS AND METHODS: With use of a personal computer with a 386 microprocessor and full-color (24 bit) graphics display capabilities, custom and commercially available image-processing softwares were applied to spatially aligned multiparameter SE MR image sets obtained from six patients undergoing diagnostic work-up for suspected adnexal or pelvic masses to generate intensity-based color composites. To quantitatively assess the ability of this technique to differentially segment anatomically and pathologically confirmed tissue types into unique color regions within the full-color spectrum, color image analysis was performed on the multiparameter color composites within each patient case, and the results were compared using 95% confidence intervals. RESULTS: Based on the results of pathologic correlation and color image analysis, the generation of full-color composites represents a feasible technique for compressing the diverse tissue contrast data present in multiparameter MR images of adnexal masses. CONCLUSION: With this technique, it is possible to generate composites that simultaneously display uniquely color-coded anatomic and pathologic tissue information within the context of partially natural-appearing images.

CT findings in 14 patients with Mycobacterium chelonae pulmonary infection.

OBJECTIVE: The purpose of this report is to describe helical and high-resolution CT findings in 14 patients with pulmonary infection caused by Mycobacterium chelonae, a nontuberculous mycobacterial species that has become increasingly recognized as a rare but significant cause of chronic lung infection in immunocompetent patients. CONCLUSION: Bronchiectasis, nodules, and consolidation are the most common CT features of M. chelonae pulmonary infection. Cavities are less common. These CT findings resemble those reported for Mycobacterium avium complex. In this study, M. chelonae pulmonary infection occurred exclusively in middle-aged and older women.