Showing papers on "Parametric Image published in 2002"

Clinical testing of high-spatial-resolution parametric contrast-enhanced MR imaging of the breast.

Abstract: OBJECTIVE. We performed a prospective clinical test of a high-spatial-resolution model-based parametric method for diagnosis of breast lesions detected on contrast-enhanced MR imaging.SUBJECTS AND METHODS. Fifty-seven women with 68 pathologically confirmed breast lesions were imaged (45 masses, 23 microcalcifications). Seven consecutive 2-min three-dimensional gradient-recalled echo acquisitions were performed after suitably timed gadopentetate dimeglumine injections. We derived a composite parametric image from three judiciously selected time points (three-time-point method), using a model-based kinetic algorithm. In this composite image, color brightness and hue signify contrast uptake and washout characteristics related to the product of microvessel surface area and permeability, as well as to the extracellular volume fraction. The reviewer was provided with the slice location of lesions, but with no other radiographic or clinical information. The reviewer then classified the lesions as benign or malig...

Improvement in echocardiographic evaluation of left ventricular wall motion using still-frame parametric imaging

Abstract: Background: Conventional echocardiographic assessment of left ventricular wall motion is based on visual interpretation of dynamic images, which depends on readers' experience. We tested the feasibility of evaluating endocardial motion using still-frame parametric images. Methods and Results: In protocol 1, integrated backscatter images were obtained in 8 anesthetized pigs at baseline, 5, and 60 seconds after left anterior descending coronary occlusion and during reperfusion. Images from 1 cardiac cycle were analyzed offline to create a parametric image of local video intensity oscillations. Ischemia-induced changes were quantified by segmenting the parametric images and calculating regional pixel-intensity profiles. In protocol 2, parametric images were obtained from contrast-enhanced echocardiograms in 30 patients (18 with wall-motion abnormalities; 12 control subjects). "Gold standard" for wall motion was determined from independent interpretations of dynamic images made by 3 experienced reviewers. Dynamic images were independently classified by 3 inexperienced and 3 intermediate-level readers. Interpretation was then repeated in combination with parametric images. Parametric images showed a bright band in the area spanned by endocardial motion, which gradually decreased in brightness and thickness in the left anterior descending territory during coronary occlusion in all animals. In patients, the agreement with the gold standard correlated with the readers' experience (68% inexperienced, 87% intermediate) and significantly improved by adding parametric images (83% and 91%, respectively). Conclusion: Parametric imaging provides a still-frame display of regional endocardial motion, sensitive to track ischemia-induced abnormalities. When combined with dynamic images, this technique improves the accuracy of the interpretation of wall motion, especially by less experienced echocardiographers. (J Am Soc Echocardiogr 2002;15:926-34.)

Methods and apparatus for contrast agent time intensity curve analyses

Abstract: A method of generating a time intensity curve includes receiving data regarding a scan of a patient injected with a contrast agent, generating a series of contrast images based upon the received data, and generating at least one parametric image based upon at least two contrast images.

Parametric image formation using clustering for dynamic cardiac SPECT

Abstract: Dynamic cardiac SPECT imaging can provide quantitative and possibly even absolute measures of physiological parameters. However, a dynamic cardiac SPECT study involves a number of steps to obtain estimates of physiological parameters of interest. One of the key steps involves the selection of regions of interest. In the past, this has been done manually or by using a semi-automatic method. We propose to use cluster analysis to segment the data to obtain improved parameter estimates. The algorithm consists of using a standard k-means clustering followed by a blood input fine-tuning procedure using fuzzy k-means performed to obtain a more accurate blood input function. Computer simulations were used to test the algorithm and to compute bias in kinetic rate parameters with and without the use of blood input fine-tuning. This was followed by performing eight studies in three canines and three studies in two patients with a dynamic cardiac perfusion SPECT protocol. The short-axis slice image data were used as input for the cluster analysis program as well as for a previously validated semi-automatic method. All of the time activity curves were fit to a two-compartment model. Parametric images of the wash-in rate parameter were obtained after cluster analysis. The wash-in rate estimates from the selected regions of interest with both of the methods were compared using microsphere derived flows as a gold standard in the case of canine studies. Our results suggest that in regions with low noise, cluster analysis provides parameter estimates comparable to the semi-automatic method in addition to providing improved visual defect localization and contrast. Moreover, the clustered curves have less noise and yield reasonable fits where with the semi-automatic method the fitting routine sometimes failed to converge. The use of clustering also required less manual intervention than the semi-automatic method. These results indicate that use of clustering may bring dynamic cardiac SPECT closer to clinical feasibility.

Noise reduction of parametric images of myocardial blood flow by filtering H/sub 2//sup 15/O dynamic PET images using wavelet transform

Abstract: Dynamic PET images are useful for the measurement of physiological functions. However, signal to noise ratio of H/sub 2//sup 15/O dynamic PET images is poor, thus filtering is necessary. It is well known that discrete wavelet transform saves detailed information in high frequency while diminishing noise. Recently, two methods to generate parametric images of myocardial blood flow using H/sub 2//sup 15/O dynamic PET images have been suggested by our group, but the signal to noise ratio of the suggested parametric images has a room for improvement by applying appropriate temporal or spatial filters to raw dynamic images. Thus, in this study, we applied wavelet transform to reduce the statistical noise in time-activity curve in each pixel prior to generating parametric images of myocardial blood flow and related parameters, and compared the image quality of parametric images with and without wavelet filtering. Wavelet denoising applied to raw dynamic images prior to generating parametric images, removed noise in time-activity curves and, as a result, increased image quality of parametric images without the degradation of spatial resolution.

Optical image amplification in phase-sensitive parametric amplifier

Abstract: The scheme of parametric image amplification without using lenses is discussed. The theoretical analysis shows that the scheme is appropriate to a broadband amplifier which assures a high linear gain, a better resolution and noiseless amplification.

Extracting kinetic information from dynamic imaging protocols: a Bayesian approach to parametric image analysis

Abstract: A Bayesian method is proposed to determine regularized parametric images from dynamic imaging protocols. The approach allows to estimate functional parameters from a mathematical model of contrast agent kinetics, and to regularize such estimate using Bayesian approaches. Simulation studies and preliminary analysis of real contrast-enhanced MRI data from mammary tumors in an animal model are encouraging.

Pixels based statistical differences between lung SPECT: experimental approach to help for the diagnosis and the follow-up of pulmonary embolism

Abstract: The statistical parametric mapping method is applied in Neurology for activation studies. We had adapted this powerful method on Lungs SPECT to help for the diagnosis and the follow-up of pulmonary embolism (PE) and other lung diseases. The SPECT slices of pairs of examination were normalized thanks to the total acquired counts, reconstruction background subtracted, smoothed and realigned. Variation in each image was estimated by a filtering approach. A parametric image of statistical differences was finally computed. We had thus obtained a 3D image showing regions of improved or altered region under treatment. We have tested the method on simulated PE images and applied it on various Lung SPECT with good results. A tuning of the various parameters could lead to more a more accurate parametric image. This new approach of lung SPECT processing appears to be a promising useful tool for the physician.

Characterization of Breast Masses Using a New Method of Ultrasound Contrast Agent Imaging in 3D Mapping of Vascular Anomalies

Abstract: : Doppler ultrasound and other imaging modalities have been used to assess characteristics of vasculature associated with malignant breast masses. 3D contrast refill imaging should help visualize slow-flow in small neo-vasculature associated with these masses. The dual-transducer method proposed should provide vascular mapping while minimizing acquisition time, the major limitation of techniques such as interval-imaging (I-I) and real-time (RT) imaging. Phantom tube-flow studies from Y2 were further quantified. A phantom kidney model initially tested in Y2 has been extensively studied and compared to I-I and RT methods. Image volumes reconstructed using the dual-transducer method displayed remarkable spatial detail. After accounting for contrast decay, mean transit times (MTTs) for image planes derived from reconstructed image volumes were consistent (p<0.05) with corresponding single I-I and RT scans. In addition, the development of a parametric image display scheme has been undertaken. Raw images highlighting differences in MTT throughout the model have been generated, and refinements to parametric calculations are currently underway. Limitations of the clinical ultrasound machine were still problematic during Y3, and no patient data has been acquired. We hope to conduct a slightly abridged clinical phase during a no-cost extension period. Y3 results are presented here.