Phantom-Less Nonlinear Magnetic Resonance Imaging Calibration With Multiple Input Blood Flow Model.

PURPOSE: Previous work used phantoms to calibrate the nonlinear relationship between the gadolinium contrast concentration and the intensity of the magnetic resonance imaging signal. This work proposes a new nonlinear calibration procedure without phantoms and considers the variation of contrast agent mass minimum combined with the multiple input blood flow system. This also proposes a new single-input method with meaningful variables that is not influenced by reperfusion or noise generated by aliasing. The reperfusion in the lung is usually neglected and is not considered by the indicator dilution method. However, in cases of lung cancer, reperfusion cannot be neglected. A new multiple input method is formulated, and the contribution of the pulmonary artery and bronchial artery to lung perfusion can be considered and evaluated separately. METHODS: The calibration procedure applies the minimum variation of contrast agent mass in 3 different regions: (1) pulmonary artery, (2) left atrium, and (3) aorta. It was compared with four dimensional computerized tomography with iodine, which has a very high proportional relationship between contrast agent concentration and signal intensity. RESULTS: Nonlinear calibration was performed without phantoms, and it is in the range of phantom calibration. It successfully separated the contributions of the pulmonary and bronchial arteries. The proposed multiple input method was verified in 6 subjects with lung cancer, and perfusion from the bronchial artery, rich in oxygen, was identified as very high in the cancer region. CONCLUSIONS: Nonlinear calibration of the contrast agent without phantoms is possible. Separate contributions of the pulmonary artery and aorta can be determined.

Fusion of lung MR/CT images through lung vessel registration.

Lung perfusion analysis with sequential contrasted MRI is an important clinical tool. This work is part of larger research in which the objective of fusing lung perfusion analysis and lung anatomical structures. In this work, it is proposed a multimodality MR/CT lung fusion algorithm based on lung vessel determination that analyzes lung perfusion. 3D contrasted MR and 3D CT images are first normalized (slice thickness, resolution and pixel intensity), then lung features are determined and elastically registered. The registration algorithm was checked by mapping in both directions, from MR to CT and vice-versa. A MR perfusion analysis result is fused with a 3D CT segmented lung vessel tree.

Applications of the chromatographic impulse response method in supercritical fluid chromatography.

The use of chromatographic impulse response (CIR) method with a coated open tubular capillary column has potential advantages in supercritical fluid chromatography. In this review, applications of the CIR method to measuring the thermodynamic properties such as diffusion coefficients, solubilities and partial molar volumes are presented. This survey gives the theoretical backgrounds for the CIR method with linear adsorption and nonlinear adsorption models. Furthermore, the brief theoretical backgrounds for using retention factors to determine solubilities and partial molar volumes are also provided. In addition, the data sources for the diffusion coefficients with an emphasis on the results published after 2004 and for the partial molar volumes in supercritical carbon dioxide are presented.

Automatic tracking of the respiratory motion of lung parenchyma on dynamic magnetic resonance imaging: comparison with pulmonary function tests in patients with chronic obstructive pulmonary disease.

PURPOSE: This study evaluated the respiratory motion of the lung parenchyma using dynamic magnetic resonance imaging and clarified differences between healthy individuals and patients with chronic obstructive pulmonary disease (COPD). MATERIALS AND METHODS: The study comprised 6 healthy volunteers and 42 patients diagnosed with smoking-related COPD. We captured 80 sequential frames from the mid-sagittal portion of the right lung while repeating forced deep breathing using a balanced fast-field echo sequence (repetition time, 2.2 ms; echo time, 1.1 ms; slice thickness, 10 mm; field of view, 450 mm; matrix size, 128 × 256; and acquisition time, 0.28 s/frame). We traced 15 points on pulmonary vessels using a computer-aided system and measured the maximal motion distance of each tracked point. Movement of these points was then compared with spirometric data using the Pearson correlation coefficient. RESULTS: Patients with COPD showed reduced respiratory motion compared with healthy volunteers. Respiratory motion and spirometric data such as forced expiratory volume in 1 s (FEV1) and FEV1/forced vital capacity showed highly significant positive correlations (correlation between normalized motion distance for the whole lung and FEV1, r = 0.75; P < 0.01). CONCLUSIONS: The respiratory motion of the pulmonary vessels reflects expansion and deflation of the lung parenchyma, and such motion is restricted in patients with COPD due to airflow limitation.

Temporal segmentation of lung region from MRI sequences using multiple active contours.

Segmentation of the lung is particularly difficult because of the large variation in image quality. A modified Hough transform in combination with a mask creation algorithm can robustly determine synchronous respiratory patterns. The synchronicity restriction is relaxed by applying a greedy active contour algorithm. The respiratory patterns define a point cloud near the lung region boundary representing a subjective contour. The gravitation vector field (GVF) active contour algorithm is used to create an initial segmentation exclusively based on the point cloud. A final active contours algorithm is executed to adjust the boundary to the images. The algorithm was tested with healthy subjects and COPD patients, and the result was checked through temporal registration of coronal and sagittal images.

Multiple registration of coronal and sagittal MR temporal image sequences based on Hough transform.

This work discusses the use of breathing patterns present in time sequences of MR images in the temporal registration of coronal and sagittal images. The registration is done without the use of any triggering information and any special gas to enhance the contrast. The temporal sequences of images are acquired in free breathing. As coronal and sagittal sequences of images are orthogonal to each other, their intersection corresponds to a segment in the three dimensional space. The registration happens by analyzing this intersection segment that is determined by a coronal-sagittal mapping. A time sequence of this intersection segment can be stacked, defining a two dimension spatio-temporal (2DST) image. It is assumed that the diaphragmatic movement is the principal movement and all the lungs structures do move almost synchronously. The synchronization was realized through a pattern named respiratory function. A Hough transform algorithm, using the respiratory function as input, searches for synchronized movements with the respiratory function. Finally, the composition of coronal and sagittal images that are in the same breathing phase is made by comparison of diaphragmatic respiratory patterns. Several results and conclusions are shown.

Temporal segmentation of lung region MR image sequences using hough transform.

In this work, segmentation is an intermediate step in the registration and 3D reconstruction of the lung, where the diaphragmatic surface is automatically and robustly isolated. Usually, segmentation methods are interactive and use different strategies to combine the expertise of humans and computers. Segmentation of lung MR images is particularly difficult because of the large variation in image quality. The breathing is associated to a standard respiratory function, and through 2D image processing, edge detection and Hough transform, respiratory patterns are obtained and, consequently, the position of points in time are estimated. Temporal sequences of MR images are segmented by considering the coherence in time. This way, the lung silhouette can be determined in every frame, even on frames with obscure edges. The lung region is segmented in two steps: a mask containing the lung region is created, and the Hough transform is applied exclusively to mask pixels. The shape of the mask can have a large variation, and the modified Hough transform can handle such shape variation. The result was checked through temporal registration of coronal and sagittal images.

Correlation of lung parenchymal MR signal intensity with pulmonary function tests and quantitative computed tomography (CT) evaluation: a pilot study.

PURPOSE: To evaluate the effect of ventilatory impairment on MR signal intensity of the lung parenchyma. MATERIALS AND METHODS: Subjects were five normal volunteers (age = 30 +/- 7.9 years, mean +/- SD) and 19 male patients with chronic obstructive lung disease (COPD) (mean age = 70.4 +/- 6.5 years). Coronal MR images were obtained over entire lung fields at full inspiration and full expiration with cardiac triggering on a 1.5T system. Changes in the mean lung intensity between the two respiratory states were normalized by each intercept of the linear regression lines of the signal changes, and the slope of the relationship was calculated. Computed tomography (CT) images were also obtained in COPD patients at full inspiration using a multidetector row CT scanner. Attenuation values less than -950 Hounsfield units (HU) (RA-950) represented the percentage of relative lung area on the CT. RESULTS: The mean slope of COPD patients (0.365 +/- 0.074) was less steep than that of the normal subjects (0.570 +/- 0.124, P < 0.001). In COPD patients, the slope correlated significantly with forced expiratory volume in one second (FEV1, r = 0.508, P = 0.026), but not with RA-950. CONCLUSION: In COPD patients, lung signal change measured by MRI correlates with airflow obstruction, but not with volume of the emphysema measured by lung CT.

Simultaneous determination of binary diffusion coefficients from multiple response curves by chromatographic measurements.

The chromatographic impulse response technique with a polymer coated capillary column was applied to measurements of infinite dilution binary diffusion coefficients D and retention factors k in supercritical carbon dioxide by injecting a hexane solution dissolving a mixture of three unsaturated fatty acids such as alpha-linolenic acid, eicosapentaenoic acid, and docosahexaenoic acid. The coefficients were simultaneously estimated by the curve fitting analysis even from partially overlapping response curves with the resolution of 0.8. The D and k values for each solute were able to be so obtained as accurately as those determined by individually injecting a single component solution. Almost no effect of the interaction among the components in the mixture was found from various approaching ways for curve fitting and the consecutive injection of the mixture at a certain interval.

Measurements of binary diffusion coefficients, retention factors and partial molar volumes for myristoleic acid and its methyl ester in supercritical carbon dioxide.

The binary diffusion coefficients, D(12), and retention factors for myristoleic acid and its methyl ester at infinite dilution were measured by the chromatographic impulse response technique in supercritical carbon dioxide at temperatures of 313.2, 333.2 and 343.2 K and pressures from 9.2 to 30 MPa for the acid, and from 8.0 to 14 MPa for the ester. Although the D(12) values were represented by the two correlations, the D(12)/T vs. CO(2) viscosity and the Schmidt-number correlations, which are valid for more than 40 compounds that we have measured so far, significant temperature dependences were observed for the ester. Moreover, the D(12) values for the ester at 313.2 K downward deviated from the background values around 400 kg m(-3), where the partial molar volumes, obtained from the correlation between the retention factors measured and CO(2) densities, showed large negative values.

Impulse response techniques to measure binary diffusion coefficients under supercritical conditions.

This review describes impulse response techniques with a curve-fitting method to measure thermodynamic properties, such as binary diffusion coefficient, retention factor, and partial molar volume, under supercritical conditions. Theoretical background, parameter sensitivity, sources of experimental error, noise elimination technique, and the correction of apparent binary diffusion coefficients due to column coiling are discussed based on recent studies, together with data sources and predictive correlations for binary diffusion coefficients.

Chromatographic impulse response technique with curve fitting to measure binary diffusion coefficients and retention factors using polymer-coated capillary columns.

The theoretical basis of a Gaussian-like approximate solution was applied to a chromatographic impulse response technique with curve fitting for measuring binary diffusion coefficients and retention factors using a polymer-coated capillary column. The formulae were derived for evaluating both the accuracy of the approximate solution and the sensitivity of the parameters. The validity of the solution also was confirmed experimentally for pulse injection of phenol in acetone into supercritical carbon dioxide flowing at 313.15 K and 11.6-28.6 MPa. Potential sources for experimental errors of the method are discussed.

High-throughput classification of images of cells transfected with cDNA clones.

The sequence of the human genome has been determined. The next task is to determine the function of the genes. Classifying cellular forms of proteins encoded by human cDNA clones is a primary step toward understanding the biological role of proteins and their coding genes. We report here our ongoing work on an automatic system to facilitate this classification. Our system handles the transfection, incubation, acquisition of microscopic images of the cells, and the classification of forms there appearing in the images. Our system correctly classified proteins by their forms at a rate of 90% in feasibility studies.