scholarly journals Magnetic resonance behavior of normal and diseased lungs: spherical shell model simulations

2000 ◽  
Vol 88 (4) ◽  
pp. 1155-1166 ◽  
Author(s):  
Carl H. Durney ◽  
Antonio G. Cutillo ◽  
David C. Ailion
Keyword(s):  
Lung Injury ◽  
Spin Echo ◽  
Theoretical Data ◽  
Alveolar Recruitment ◽  
Spherical Shells ◽  
Lung Inflation ◽  
Resonance Behavior ◽  
Tissue Interface ◽  
The Difference ◽  
Asymmetric Spin Echo

The alveolar air-tissue interface affects the lung NMR signal, because it results in a susceptibility-induced magnetic field inhomogeneity. The air-tissue interface effect can be detected and quantified by measuring the difference signal (Δ) from a pair of NMR images obtained using temporally symmetric and asymmetric spin-echo sequences. The present study describes a multicompartment alveolar model (consisting of a collection of noninteracting spherical water shells) that simulates the behavior of Δ as a function of the level of lung inflation and can be used to predict the NMR response to various types of lung injury. The model was used to predict Δ as a function of the inflation level (with the assumption of sequential alveolar recruitment, partly parallel to distension) and to simulate pulmonary edema by deriving equations that describe Δ for a collection of spherical shells representing combinations of collapsed, flooded, and inflated alveoli. Our theoretical data were compared with those provided by other models and with experimental data obtained from the literature. Our results suggest that NMR Δ measurements can be used to study the mechanisms underlying the lung pressure-volume behavior, to characterize lung injury, and to assess the contributions of alveolar recruitment and distension to the lung volume changes in response to the application of positive airway pressure (e.g., positive end-expiratory pressure).

Alveolar air-tissue interface and nuclear magnetic resonance behavior of lung

1991 ◽  
Vol 70 (5) ◽  
pp. 2145-2154 ◽  
Author(s):  
A. G. Cutillo ◽  
K. Ganesan ◽  
D. C. Ailion ◽  
A. H. Morris ◽  
C. H. Durney ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Spin Echo ◽  
Lung Water ◽  
Alveolar Air ◽  
Resonance Behavior ◽  
Theoretical Predictions ◽  
Free Induction ◽  
Tissue Interface ◽  
Nuclear Magnetic

Inflated lungs are characterized by a short nuclear magnetic resonance (NMR) free induction decay (rapid disappearance of NMR signal), likely due to internal (tissue-induced) magnetic field inhomogeneity produced by the alveolar air-tissue interface. This phenomenon can also be detected using temporally symmetric and asymmetric NMR spin-echo sequences; these sequences generate a pair of NMR images from which a difference signal (delta) is obtained (reflecting the signal from lung water experiencing the air-tissue interface effect). We measured delta in normal excised rat lungs at inflation pressures of 0-30 cmH2O for asymmetry times (a) of 1-6 ms. Delta was low in degassed lungs and increased markedly with alveolar opening when measured at a = 6 ms (delta 6 ms); delta 6 ms varied little during the rest of the inflation-deflation cycle. Delta 1 ms (a = 1 ms) did not vary significantly on inflation and deflation. Measurements of delta at a = 3 and 5 ms generally lay between those of delta 1 ms and delta 6 ms. These findings, which are consistent with theoretical predictions, suggest that measurements of delta at appropriate asymmetry times are particularly sensitive to alveolar opening and may provide a means of distinguishing alveolar recruitment from alveolar distension in the pressure-volume behavior of the lung.

scholarly journals Dynamic R2' Imaging can Be a Biomarker for Diagnosing and Staging Early Acute Kidney Injury in Animals

2021 ◽  
Vol 8 ◽  
Author(s):  
Bihui Zhang ◽  
Ziping Yao ◽  
Weizheng Gao ◽  
Chengyan Wang ◽  
Hanjing Kong ◽  
...  
Keyword(s):  
Acute Kidney Injury ◽  
Animal Models ◽  
Spin Echo ◽  
Transarterial Embolization ◽  
Kidney Injury ◽  
Clinical Settings ◽  
Spin Echo Sequence ◽  
The Difference ◽  
Asymmetric Spin Echo ◽  
And Control

Background: Early diagnosis of acute kidney injury (AKI) is essential in clinical settings. None of the current biomarkers are widely applied. The combination of pulse-shifting multi-echo asymmetric spin-echo sequence (psMASE) and a modified hemodynamic response imaging (HRI) technique is promising. The purpose of this study was to evaluate the feasibility of psMASE combined with HRI in detecting early ischemic AKI in animal models of different severities.Methods: Twenty rabbits were divided into four groups (mild, moderate, and severe AKI and control groups). Transarterial embolization with different doses of microspheres was performed to establish AKI animal models of different severities. The 3T psMASE and HRI scans of kidneys were conducted. The R2*, R2, and R2' during room air and gas stimulation were acquired and the difference of R2' (dR2') was evaluated in different AKI groups.Results: The values were not different in R2* and R2 during room air and in R2* and R2, and R2' during gas stimulation. The value of R2' was significantly different during room air (P = 0.014), but the difference was only found between control and moderate/severe AKI groups (P = 0.032 and 0.022). The values of dR2' were different among groups (P < 0.0001) and differences between every two groups except comparison of moderate and severe AKI groups were significant (P < 0.01).Conclusion: The dR2' imaging acquired by a combination of renal psMASE and HRI technique can serve as a potential quantitative biomarker for early detection and staging of AKI.

COMPARISON OF VARIOUS MRI FAT SUPPRESSION TECHNIQUES ON A WATER-FAT PHANTOM AT 1.5 T

2017 ◽  
Vol 29 (02) ◽  
pp. 1750015
Author(s):  
Hui-Chun Wang ◽  
Po-Chou Chen ◽  
Chun-Hsiung Chou ◽  
Cherng-Gueih Shy ◽  
Jo-Chi Jao
Keyword(s):  
Spin Echo ◽  
Fat Suppression ◽  
Time Inversion ◽  
Oil In Water ◽  
Iterative Decomposition ◽  
The Difference ◽  
Soft Tissue Diseases ◽  
Magnetic Resonance Imaging Mri ◽  
Fat Suppression Techniques ◽  
Clinical Mri

Nowadays, magnetic resonance imaging (MRI) has been widely applied for diagnosis of soft-tissue diseases. Most clinical MRI protocols use fat suppression (FS) methods to suppress fat signal, reduce chemical shift artifacts, and increase conspicuity of lesions. To understand the advantages, disadvantages, and clinical applications of the most commonly used FS methods is an important issue. The aim of this study was to evaluate FS performance of six FS methods on a fat-water phantom at 1.5[Formula: see text]T. The six MRI methods included iterative decomposition of water and fat with echo asymmetry and least squares estimation (IDEAL), short inversion time inversion recovery (STIR), and four chemical presaturation (Chem Presat) methods. The phantom was composed of homogeneous oil-in-water emulsions with various fat contents ranging from 0 to 100% in increments of 10%. The difference between the suppressed fat fractions (FS fractions) and the true fat fractions of the phantom was used as an index of FS performance. The correlations and levels of agreement (LOAs) between the FS fractions determined using each FS method and the true fat fractions of the phantom were analyzed. From the phantom study, it was found that FSE T2 FS, STIR and IDEAL could achieve more accurate FS fractions than the other three methods. The FS fractions determined using FSE T2 FS, STIR and IDEAL were in a good agreement. On the contrary, T2-weighted spin echo Chem Presat had the most inaccurate quantification of FS fractions among these six FS methods. Both the ranks of signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs) of the phantom were IDEAL [Formula: see text] FSE T2 FS [Formula: see text] STIR. The FS performance of these six FS methods in clinical use needs further study.

Response of alveolar epithelial solute permeability to changes in lung inflation

1980 ◽  
Vol 49 (6) ◽  
pp. 1032-1036 ◽  
Author(s):  
E. A. Egan
Keyword(s):  
Pore Radius ◽  
Alveolar Epithelium ◽  
Molecular Size ◽  
High Volume ◽  
Lung Inflation ◽  
Solute Permeability ◽  
Alveolar Epithelial ◽  
The Difference ◽  
Total Capacity ◽  
Inflation Volume

The relation between the solute permeability of th alveolar epithelium, characterized as a pore radius, and lung inflation was studied in anesthetized dogs. Pore radius was calculated from measurements of the rate of efflux of several radiolabeled solutes of known molecular size from alveolar saline. Individual animals were studied at two or more separate inflation volumes. The pore radius during the first volume studied averaged 20 A in high-volume animals (mean inflation 82% of capacity) and 15 A at lower volume (mean inflation, 47% of capacity). The difference was significantly P < 0.05. Lungs inflated to total capacity showed free solute movement across the lung epithelium. Increasing inflation volume in an animal always produced a larger pore radius. Decreasing the inflation volume did not produce a smaller pore radius; it remained the same or became larger. Volume induced increases in lung epithelial solute permeability do not reverse immediately at lower volumes, suggesting this phenomenon represents lung injury.

Nuclear magnetic resonance hahn spin-echo decay (T2) in live rats with endotoxin lung injury

1993 ◽  
Vol 29 (4) ◽  
pp. 441-445 ◽  
Author(s):  
Sumie Shioya ◽  
Rebecca Christman ◽  
David C. Ailion ◽  
Antonio G. Cutillo ◽  
K. Craig Goodrich
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Lung Injury ◽  
Spin Echo ◽  
Nuclear Magnetic

Mapping of the cerebral response to acetazolamide using graded asymmetric spin echo EPI

2005 ◽  
Vol 23 (9) ◽  
pp. 907-920 ◽  
Author(s):  
Bhashkar Mukherjee ◽  
Mark Preece ◽  
Gavin C. Houston ◽  
Nikolas G. Papadakis ◽  
T. Adrian Carpenter ◽  
...  
Keyword(s):  
Spin Echo ◽  
Asymmetric Spin Echo

SU-FF-I-70: Asymmetric Spin Echo in FMRI at 3T: A Quantitative Evaluation of BOLD Response and Signal Drop Off

2006 ◽  
Vol 33 (6Part4) ◽  
pp. 2013-2013
Author(s):  
P Hou ◽  
J Steinberg ◽  
D Chen ◽  
F moeller ◽  
P Narayana
Keyword(s):  
Quantitative Evaluation ◽  
Spin Echo ◽  
Bold Response ◽  
Asymmetric Spin Echo

Effects of lung inflation and blood flow on capillary transit time in isolated rabbit lungs

1992 ◽  
Vol 72 (6) ◽  
pp. 2420-2427 ◽  
Author(s):  
P. M. Wang ◽  
C. D. Fike ◽  
M. R. Kaplowitz ◽  
L. V. Brown ◽  
I. Ayappa ◽  
...  
Keyword(s):  
Blood Flow ◽  
Transit Time ◽  
Transpulmonary Pressure ◽  
Lung Inflation ◽  
Video Signals ◽  
Pulmonary Capillary ◽  
Direct Measurements ◽  
Video Microscope ◽  
The Difference ◽  
Group 2

In a previous study, direct measurements of pulmonary capillary transit time by fluorescence video microscopy in anesthetized rabbits showed that chest inflation increased capillary transit time and decreased cardiac output. In isolated perfused rabbit lungs we measured the effect of lung volume, left atrial pressure (Pla), and blood flow on capillary transit time. At constant blood flow and constant transpulmonary pressure, a bolus of fluorescent dye was injected into the pulmonary artery and the passage of the dye through the subpleural microcirculation was recorded via the video microscope on videotape. During playback of the video signals, the light emitted from an arteriole and adjacent venule was measured using a video photoanalyzer. Capillary transit time was the difference between the mean time values of the arteriolar and venular dye dilution curves. We measured capillary transit time in three groups of lungs. In group 1, with airway pressure (Paw) at 5 cmH2O, transit time was measured at blood flow of approximately 80, approximately 40, and approximately 20 ml.min-1.kg-1. At each blood flow level, Pla was varied from 0 (Pla less than Paw, zone 2) to 11 cmH2O (Pla greater than Paw, zone 3). In group 2, at constant Paw of 15 cmH2O, Pla was varied from 0 (zone 2) to 22 cmH2O (zone 3) at the same three blood flow levels. In group 3, at each of the three blood flow levels, Paw was varied from 5 to 15 cmH2O while Pla was maintained at 0 cmH2O (zone 2).(ABSTRACT TRUNCATED AT 250 WORDS)

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