Background : Intravascular ultrasound (IVUS) is becoming increasingly accepted for assessing coronary anatomy. However, its utility in visualizing and quantifying coronary morphology has been limited by its 2D tomographic nature. This study presents a 3D reconstruction technique that accurately preserves 3D geometric information. Methods and Results : Images obtained from manual IVUS pullbacks and continuous bi-plane angiography were fused, using angiography to reconstruct the transducer trajectory and aid in solving for the correct rotational orientation. A novel 3D active surface method automatically identified the luminal and medial–adventitial borders which, when superimposed on the transducer trajectory, could be surface-rendered for visualization and morphometry. Segmentation agreed well with manual assessment, and 3D luminal shape matched that of angiography when projected to 2D. Conclusions : We conclude that this method provides an accurate reconstruction of the vessel's anatomy, which accounts for the true curvature of the vessel.

We are investigating the use of optical spectroscopy (fluorescence, reflectance, Raman scattering) for detecting precancerous lesions in the mucosal linings of hollow organs. We present a morphological model for extracting quantitative pathological information from fluorescence spectra, using colonic dysplasia as an example. The potential of this technique in providing histological information in real time without the need for tissue removal is discussed.

The intrinsic fluorescence achieved without dyes (autofluorescence) of bladder tissue, benign mucosa and the various stages of transitional cell carcinoma (TCC), is being characterized. D'Hallewin, et al., and Koenig, et al., are testing autofluorescence spectroscopy for detecting bladder carcinoma using an optical fiber probe inserted down the auxiliary channel of an endoscope. These studies do not include fluorescent microscopy to directly examine the fluorescing structures (fluorophores) within the tissue. Therefore, frozen unstained sections are being imaged on a fluorescence microscope to identify and reveal the morphology and location of the fluorophores. Tissue biopsies taken at endoscopy are immediately frozen in liquid nitrogen. Later, the tissue is cut into 5 μm sections. Serial sections are alternately imaged frozen on the fluorescence microscope or stained with hematoxylin-and-eosin (H&E). The H&E stained slides are reviewed by a pathologist.A 75-W xenon arc lamp fitted with a 380-nm narrow-band interference filter is coupled to microscope slides on the stage of an Olympus MT-2 inverted microscope.

Several groups have shown that laser-induced fluorescence spectroscopy can detect dysplastic changes in human colon tissues. We present an approach based on analysis of the underlying tissue microstructure for extracting histological information from such spectral signals. The method employs fluorescence microscopy and tissue optics to model the `bulk' fluorescence collected with an optical fiber probe in a clinical setting. For both colonic normal and adenoma, we measured the intrinsic fluorescence lineshapes, the spatial distributions of the fluorophores, and optical parameters of tissue. Numerical and analytical solutions to the radiative transfer equation were then used to compute fluorescence spectra. The results of the model were in excellent agreement with clinical spectra collected during colonoscopy, using 370 nm excitation. Four factors were found to be responsible for the spectral differences between normal tissue and adenoma: fluorescence of mucosal collagen, dysplastic cell, and submucosa, and hemoglobin attenuation. Preliminary results indicate that these parameters can be extracted from individual clinical spectra by reversing the modeling procedure.

The potential for intravascular ultrasound (IVUS) to evaluate arterial pathologies and to suggest invasive techniques thus far has been limited by its qualitative and subjective evaluation. The purpose of this study is to develop tools to automatically identify and objectively quantify the calcifications present in IVUS images of human coronaries.

Unstained frozen sections of normal and atherosclerotic human aorta and coronary artery were examined using histochemical and fluorescence microscopic techniques to identify the structures responsible for autofluorescence under 351 to 364 nm laser excitation. These structures included elastin and collagen in normal and atherosclerotic specimens, calcium deposits in calcified plaques, and granular or ring-shaped deposits histochemically identified as ceroid found in both calcified and non-calcified plaques. Qualitatively, both the color and intensity of ceroid autofluorescence differed greatly from that of elastin or collagen. The emission spectra of elastin, collagen, and ceroid were examined by microscopic spectrofluorimetry, and were found to differ significantly as well. When compared with spectra of elastin and collagen, spectra of ceroid were broader, shifted to the red, and were somewhat resistant to bleaching. We conclude that detection of laser-induced ceroid autofluorescence may aid in identifying plaques for laser ablation.

Laser induced fluorescence has been explored as an early detection scheme for two clinically important examples of neoplasia: colorectal dysplasia and transitional cell carcinoma in the urinary bladder. In both, it is desirable to detect microscopic and biochemical changes of pre-cancer in order to identify patients at risk for developing invasive carcinoma. This paper will compare the fluorescence obtained from these two pre-cancerous conditions, and discuss the connection between the fluorescence and the morphological/molecular changes occurring in the tissue. The similarities and differences in the fluorescence will be compared to determine the general features of pre-cancerous changes that might be utilized for detection of the disease.