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ABSTRACT: The aim of this study was to investigate the short-term effects of furosemide on renal perfusion by using arterial spin labeling (ASL) magnetic resonance imaging.
Eleven healthy human subjects were enrolled in the study. The measurement of renal blood flow (RBF) was performed by applying an ASL technique with flow-sensitive alternating inversion recovery spin preparation and a single-shot fast spin-echo imaging strategy on a 3.0-T magnetic resonance scanner. For all subjects, the ASL magnetic resonance images were obtained before agent injection as a baseline scan. Then 20 mg of furosemide was injected intravenously. Postfurosemide ASL images were acquired following administration to evaluate the renal hemodynamic response.
Postinjection scans showed that cortical RBF decreased from 366.59 ± 41.19 mL/100 g/min at baseline to 314.33 ± 48.83 mL/100 g/min at 10 minutes after the administration of furosemide (paired t test, P = .04 vs baseline), and medullary RBF decreased from 118.59 ± 24.69 mL/100 g/min at baseline to 97.38 ± 18.40 mL/100 g/min at 10 minutes after the administration of furosemide (paired t test, P = .01 vs baseline). There was a negative correlation between the furosemide-induced diuretic effect and the reduction of RBF (Spearman's r = -0.61).
The dominant hemodynamic effect of furosemide on the kidney is associated with a decrease in both cortical and medullary blood perfusion. Furthermore, the quantitative ASL technique may provide an alternative way to noninvasively monitor the change in renal function due to furosemide administration.
Academic radiology 10/2012; 19(10):1194-200. · 2.09 Impact Factor
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ABSTRACT: Contrast-induced nephropathy is a prevalent cause of renal failure, and the mechanisms underlying this injury are not fully understood. We utilized noninvasive functional MRI in order to determine the serial effect of a single administration of iodinated contrast media (CM) on renal hemodynamics and oxygenation. Fifteen rabbits were randomized to receive an intravenous injection of CM (i.e. iopamidol-370; 6 ml kg(-1) body weight) or an equivalent amount of 0.9% saline. Both arterial spin-labeling and blood oxygen level-dependent imaging sequences were performed at 24 h before and at intervals of 1, 24, 48 and 72 h after injection to obtain serial renal blood flow (RBF) and relative spin-spin relaxation rate (R(2)*). Results showed that, in the iopamidol group, the mean cortical RBF decreased at 1 h (p = 0.04 vs baseline), reached its minimum at 24 h (p = 0.01) and gradually returned to baseline by 48 h (p = nonsignificant, NS). The outer medullary RBF decreased to its minimum by 24 h (p = 0.00) and remained less than baseline until 72 h. R(2)* in inner stripes was dramatically increased at 1 h (p = 0.00), remained elevated at 24 h (p = 0.05), but returned to baseline by 48 h (p = NS). R(2)* values within the cortex and outer stripes and inner medulla were slightly increased, but the changes did not reach a statistical significance (p = NS). Saline did not produce positive change in either RBF or R(2)* within different compartments of the kidney. We conclude that iopamidol is associated with a relatively longer-term hypoperfusion in whole kidney and decreased oxygen level in the inner stripes of the outer medulla.
Contrast Media & Molecular Imaging 07/2012; 7(4):418-25. · 3.33 Impact Factor
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ABSTRACT: The purpose of this study was to demonstrate the feasibility of an asymmetric spin echo (ASE) single-shot echo planar imaging (EPI) sequence for the noninvasive quantitative measurement of intrarenal R(2) ' in humans within 20 s. The reproducibility of R(2) ' measurements with the ASE-EPI sequence was assessed in nine healthy young subjects in repeated studies conducted over three consecutive days. Moreover, we also evaluated whether the ASE-EPI sequence-measured R(2) ' reflected the intrarenal oxygenation changes induced by furosemide in another group of normal human subjects (n = 10). Different flow attenuation gradients (b = 0, 40 and 80 s/mm(2) ) were utilized to examine the impact of the intravascular signal contribution on the estimation of intrarenal R(2) '. In the absence of flow dephasing gradients (b = 0 s/mm(2) ), the computed coefficient of variation (CV) of R(2) ' was 21.31 ± 4.52%, and the estimated R(2) ' value decreased slightly, but not statistically significantly (p > 0.05), after the administration of furosemide in the medullary region. However, CV of R(2) ' was much smaller in the presence of flow dephasing gradients (9.68 ± 3.58% with b = 40 s/mm(2) and 10.50 ± 3.62% with b = 80 s/mm(2) ). Moreover, a significant reduction in R(2) ' in the renal medulla was obtained (p < 0.05 for both b = 40 s/mm(2) and b = 80 s/mm(2) ) after the administration of furosemide, reflecting an increase in oxygen tension in the medullary region. In addition, R(2) ' measurements did not differ between the b = 40 s/mm(2) and b = 80 s/mm(2) scans, suggesting that small diffusion gradients were sufficient to minimize the intravascular signal contribution. In summary, we have demonstrated that renal R(2) ' can be obtained rapidly using an ASE-EPI sequence. The measurement was highly reproducible and reflected the expected intrarenal oxygenation changes induced by furosemide. Copyright © 2012 John Wiley & Sons, Ltd.
NMR in Biomedicine 06/2012; · 3.21 Impact Factor
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ABSTRACT: To investigate the feasibility of T(1) -weighted dynamic contrast-enhanced (DCE) MRI for the measurement of brain perfusion.
Dynamic imaging was performed on a 3.0 Tesla (T) MR scanner by using a rapid spoiled-GRE protocol. T(1) measurement with driven equilibrium single pulse observation of T(1) (DESPOT1) was used to convert the MR signal to tracer concentration. Cerebral perfusion maps were obtained by using an improved gamma-variate model in 10 subjects and compared with those with arterial spin label (ASL) approach.
The cerebral blood volume (CBV) values were calculated as 4.74 ± 1.09 and 2.29 ± 0.58 mL/100 g in gray matter (GM) and whiter matter (WM), respectively. Mean transit time (MTT) values were 6.15 ± 0.59 s in GM and 6.96 ± 0.79 s in WM. The DCE values for GM/WM cerebral blood flow (CBF) were measured as 53.41 ± 9.23 / 25.78 ± 8.91 mL/100 g/min, versus ASL values of 49.05 ± 10.81 / 23.00 ± 5.89 mL/100 g/min for GW/WM. Bland-Altman plot revealed a small difference of CBF between two approaches (mean bias = 3.83 mL/100 g/min, SD = 11.29). There were 6 pairs of samples (5%, 6/120) beyond the 95% limits of agreement. The correlation plots showed that the slop of Y (CBF_(_DCE)) versus X intercept (CBF_(_ASL)) is 0.95 with the intercept of 4.53 mL/100 g/min (r = 0.74; P < 0.05).
It is feasible to evaluate the cerebral perfusion by using T(1)-weighted DCE-MRI with the improved kinetic model.
Journal of Magnetic Resonance Imaging 02/2012; 35(6):1322-31. · 2.70 Impact Factor
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ABSTRACT: To assess the effects of intravenous-injected iodinated contrast medium (CM) on intrarenal water diffusion using noninvasive diffusion-weighted MRI (DW-MRI).
Ten New Zealand White rabbits were randomized to receive a 6 mL/kg body weight intravenous injection of clinically used iopamidol-370 (n = 7) or an equivalent amount of 0.9% physiological saline (n = 3). A sequential DW-MRI was performed to estimate the intrarenal apparent diffusion coefficient (ADC) at 24 h before and 1 h, 24 h, 48 h, and 72 h after administration.
Iopamidol produced a progressive ADC reduction in inner stripes of the renal outer medulla (IS) by 13.92% (P = 0.05) at 1 h, 17.52% (P = 0.02) at 24 h, 20.23% (P = 0.01) at 48 h and 16.31% (P = 0.04) at 72 h after injection. Cortical ADC was decreased by 14.14% (P = 0.01) at 48 h and 14.12% (P = 0.01) at 72 h after injection. Iopamidol produced slight decrease of ADCs in outer stripes of the outer medulla (OS) and inner medulla (IM) of kidney but without statistical difference. In control group, no significant ADC changes was observed in each anatomic compartment due to saline injection (P > 0.05).
As demonstrated by DW-MRI, intravenous iopamidol injection resulted in a successive reduction of intrarenal water diffusion, particularly in IS of kidney. This MR technique may be used as a noninvasive tool to perform a time course study of the pathogenesis associated with contrast-induced nephropathy (CIN).
Journal of Magnetic Resonance Imaging 01/2012; 35(5):1139-44. · 2.70 Impact Factor
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ABSTRACT: To explore the potential of computerized characterization of prostate MR images by extracting the fractal features of texture and intensity distributions as indices in the differential diagnosis of prostate cancer.
MR T2-weighted images (T2WI) of 55 patients with pathologic results detected by ultrasound guided biopsy were collected and then divided in two groups, 27 with prostate cancer (PCa) and 28 with no histological abnormality. Texture fractal dimension (TFD) and histogram fractal dimension (HFD) were calculated to analyze complexity features of regions of Interest (ROIs) selected from the peripheral zone. Two-sample t-tests were performed to evaluate group differences for both parameters. Receiver operating characteristic (ROC) analysis was used to estimate the performance of TFD and HFD for discriminating PCa.
Significant differences were found in both TFD and HFD between the two patient groups. The areas under the ROC curves of TFD and HFD were 0.691 and 0.966, respectively, in distinguishing prostatic carcinoma from normal peripheral zone. As characterized by the fractal indices, cancerous prostatic tissue exhibited smoother texture and lower variation in intensity distribution than normal prostatic tissue.
The study suggests that TFD and HFD depict the changes in texture and intensity distribution associated with prostate cancer on T2WI. Both TFD and HFD provide promising quantitative indices for cancer identification. HFD performs better than TFD offering a more robust MR-based indicator in the diagnosis of prostatic carcinoma.
Journal of Magnetic Resonance Imaging 07/2009; 30(1):161-8. · 2.70 Impact Factor
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ABSTRACT: PurposeTo explore the potential of computerized characterization of prostate MR images by extracting the fractal features of texture and intensity distributions as indices in the differential diagnosis of prostate cancer.Materials and MethodsMR T2-weighted images (T2WI) of 55 patients with pathologic results detected by ultrasound guided biopsy were collected and then divided in two groups, 27 with prostate cancer (PCa) and 28 with no histological abnormality. Texture fractal dimension (TFD) and histogram fractal dimension (HFD) were calculated to analyze complexity features of regions of Interest (ROIs) selected from the peripheral zone. Two-sample t-tests were performed to evaluate group differences for both parameters. Receiver operating characteristic (ROC) analysis was used to estimate the performance of TFD and HFD for discriminating PCa.ResultsSignificant differences were found in both TFD and HFD between the two patient groups. The areas under the ROC curves of TFD and HFD were 0.691 and 0.966, respectively, in distinguishing prostatic carcinoma from normal peripheral zone. As characterized by the fractal indices, cancerous prostatic tissue exhibited smoother texture and lower variation in intensity distribution than normal prostatic tissue.Conclusion
The study suggests that TFD and HFD depict the changes in texture and intensity distribution associated with prostate cancer on T2WI. Both TFD and HFDprovide promising quantitative indices for cancer identification. HFD performs better than TFD offering a more robust MR-based indicator in the diagnosis of prostatic carcinoma. J. Magn. Reson. Imaging 2009;30:161–168. © 2009 Wiley-Liss, Inc.
Journal of Magnetic Resonance Imaging 06/2009; 30(1):161 - 168. · 2.70 Impact Factor
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ABSTRACT: In this article, an improved method to segment the renal cortex and medulla and to eliminate the influence of kidney motion produced by respiration is proposed. On the basis of an adaptive threshold estimated from the mean gray levels of the grown regions, a region-growing algorithm is presented to produce a three-dimensional (3-D) kidney contour and to segment the renal structures. Moreover, a shell mask of kidney margin is proposed to realize a coarse matching so as to eliminate the image translation, which makes the processing simple and direct in spatial processing without any image transform computations, and a correlation computation can be implemented with great efficiency. Then, a refined matching with a mask of cortex is completed through a 3-D correlation algorithm to ensure the accurate registration of the images in different phases. Comparing with the global mask including the whole kidney, both the shell mask and the cortex mask significantly contribute to decreasing the matching errors for images with nonuniform intensity signals, which much improves the registration quality of renal MR images. In this way, the effect of the respiration motions can be eliminated so that the intensity measurement in different phases becomes accurate within the respective structures.
IEEE Engineering in Medicine and Biology Magazine 10/2008; 27(5):36-41. · 2.06 Impact Factor
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ABSTRACT: In this paper, a novel and fast method to detect liver nodules automatically based on the original image, which avoids problems raised by liver segmentation was proposed. Algorithms were applied to determine the candidate regions which may contain nodules and the gray value of a nodule is typically considered to be a local extremum, but not necessarily a maximum, as it differs in signal from the surrounding parenchyma. Fuzzy C-means(FCM), which is an optimization algorithm to classify the image into C clusters based on the distance of the pixels to the cluster center in the feature domain, was used to segment the image. This is followed by a morphological smoothing, identification and analysis of candidate regions by computing properties which include area, centroid location, shape in a two-dimensional slice and connectivity in three dimensional space. Candidate regions whose properties are similar to that of nodules are extracted as the final result.
Frontiers in the Convergence of Bioscience and Information Technologies, 2007. FBIT 2007; 11/2007
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ABSTRACT: With respect to an arbitrary configuration of a deformed structure, two sets of incremental equations are proposed for the
deformation analysis of revolution shells and diaphragms loaded by both lateral pressures and the initial stresses produced
in manufacturing. These general equations can be reduced to the simplified Koiter's Reissner-Meissner-Reissner (RMR) equations
and the simplified Reissner's equations, when the initial stresses are set to zero. They can also be deduced to the total
Lagrange form or the updated Lagrange form, respectively, as the structure is specified as the un-deformed or the former-deformed
configurations. These incremental equations can be easily transformed into finite difference forms and solved by common numerical
solvers of ordinary differential equations. Some numerical examples are presented to show the applications of the incremental
equations to the deep shell of revolution and the corrugated diaphragms used in microelectronical mechanical system (MEMS).
The results are in good agreement with those from finite element method (FEM).
Acta Mechanica Sinica 01/2006; 21(6):592-600. · 0.86 Impact Factor
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ABSTRACT: We present a structured light system to dynamically measure human chest wall motion for respiratory volume estimation. Based on a projection of an encoded color pattern and a few active markers attached to the trunk, respiratory volumes are obtained by evaluating the 3-D topographic changes of the chest wall in an anatomically consistent measuring region during respiration. Three measuring setups are established: a single-sided illuminating-recording setup for standing posture, an inclined single-sided setup for supine posture, and a double-sided setup for standing posture. Results are compared with the pneumotachography and show good agreement in volume estimations [correlation coefficient: R>0.99 (P<0.001) for all setups]. The isovolume tests present small variations of the obtained volume during the isovolume maneuver (standard deviation<0.085 L for all setups). After validation by the isovolume test, an investigation of a patient with pleural effusion using the proposed method shows pulmonary functional differences between the diseased and the contralateral sides of the thorax, and subsequent improvement of this imbalance after drainage. These results demonstrate the proposed optical method is capable of not only whole respiratory volume evaluation with high accuracy, but also regional pulmonary function assessment in different chest wall behaviors, with the advantage of whole-field measurement.
Journal of Biomedical Optics 15(2):026013. · 3.16 Impact Factor
