عنوان

Proton magnetic resonance of lung

Number

TLpq304505344

.Language of Text, Soundtrack etc

انگلیسی

Title Proper

Proton magnetic resonance of lung

General Material Designation

[Thesis]

First Statement of Responsibility

M. R. Estilaei

Subsequent Statement of Responsibility

A. Mackay

Name of Publisher, Distributor, etc.

The University of British Columbia (Canada)

Date of Publication, Distribution, etc.

1998

Specific Material Designation and Extent of Item

124

Dissertation or thesis details and type of degree

Ph.D.

Body granting the degree

The University of British Columbia (Canada)

Text preceding or following the note

1998

Text of Note

Proton nuclear magnetic resonance H NMR was used to investigate the entire signal from excised lung tissue. The free induction decay signal contained a motionally restricted component which decayed in a few 10's of usd\mu susd and a mobile component which persisted about 10 ms or longer. The motionally restricted component was characterized by the second moment of its lineshape which had an average value of 3.42 (0.25) usd\timesusd 10 This value was about 1/3 of the rigid lattice usdM\sb2usd value, indicating that long: macromolecules undergo considerable anisotropic motion on the NMR timescale. The mobile component of the lung was characterized by its T2 relaxation times which relate to the microscopic tissue environment. Due to the inhomogeneous nature of the structure and biochemical composition of lung, a smooth T2 distribution was assumed. The mobile signal consistently showed four resolvable components of T2 range: 2-6, 10-40, 80-110, and 190-400 ms. The 2-6 ms component was present in a fully dehydrated preparation and was therefore assigned to a non-aqueous lung constituent. Collagen is a major protein present in lung tissue and has high tensile strength, rigidity and binding affinity for water. For this reason, the dependence of the second moment, T2 relaxation times, and T2 relaxation amplitudes on collagen content were studied. To determine the lung wet/dry ratio, the hydrogen content per unit mass for lung parenchyma and water were estimated in two ways: (1) on the basis of chemical content, and (2) on the basis of comparison of restricted and mobile signals to the gravimetric (G) water content for a lung-sample studied at a wide range of water contents. Lung Wet/Dry weight ratios were estimated from the free induction decays and compared with gravimetric measurements. The ratio of (Wet/Dry){NMR}/(Wet/Dry){G} was 1.00 (0.08) and 1.00 (0.05) for the two methods of estimation. The water content measurements were validated and T2 distributions were determined in inflated, deflated, and perfused lungs on a clinical 1.5 T MRI scanner. The mean difference between the gravimetric and MRI water contents was usd{-}4.1g\pm 7.6\%usd and an excellent linear correlation squared usd(R\sp2=0.98)usd was observed between the two independent measurements. A spherical shell model was tailored to characterize the susceptibility-induced magnetic field gradients in inflated lung and a simulation was performed to assess the effect of diffusion alone on the T2 decay curve. This approach demonstrated that the multiexponential nature of the T2 distribution was largely due to diffusion of water molecules in the magnetic field gradients. This study also enabled measurements of the inherent T2 relaxation. The estimation of the magnetic field gradients facilitated measurement of the apparent diffusion coefficient by collecting images at a fixed imaging time using a multiecho pulse sequence with different echo spacing. The apparent diffusion coefficient decreased from about usd1.1\times 10\sp{-5}cm\sp2/susd to usd1.7\times 10\sp{-6}cm\sp2/susd as diffusion time increased from 12 to 60 ms. (Abstract shortened by UMI.)

collagen

Health and environmental sciences

Radiology

A. Mackay

M. R. Estilaei

Electronic name

p

[Thesis]

276903

a

Y