Feasibility of combining MR perfusion, angiography, and 3He ventilation imaging for evaluation of lung function in a porcine model.

Rationale And Objective: To assess the feasibility of combining magnetic resonance (MR) perfusion, angiography, and 3He ventilation imaging for the evaluation of lung function in a porcine model.

Materials And Methods: Fourteen consecutive porcine models with externally delivered pulmonary emboli and/or airway occlusions were examined with MR perfusion, angiography, and 3He ventilation imaging. Ultrafast gradient-echo sequences were used for 3D perfusion and angiographic imaging, in conjunction with the use of contrast-agent injections.

Feasibility of diffusion-NMR surface-to-volume measurements tested by calculations and computer simulations.

It has been demonstrated previously that the surface-to-volume ratio S/V can be determined from the derivative of the time-dependent diffusion coefficient D(t), in the limit t --> 0. Several questions arise concerning the practicality of determining S/V by NMR. In particular, how large are the errors generated by (1) working outside the t --> 0 limit and (2) measuring D outside the b --> 0 limit, both for narrow and full-width gradient pulses? Here b is gamma2G2delta2Delta for narrow pulses and gamma2G2t3/12 for broad pulses.

Combined MR proton lung perfusion/angiography and helium ventilation: potential for detecting pulmonary emboli and ventilation defects.

Three-dimensional (3D) perfusion imaging allows the assessment of pulmonary blood flow in parenchyma and main pulmonary arteries simultaneously. MRI using laser-polarized (3)He gas clearly shows the ventilation distribution with high signal-to-noise ratio (SNR). In this report, the feasibility of combined lung MR angiography, perfusion, and ventilation imaging is demonstrated in a porcine model.

Quantitative in vivo assessment of lung microstructure at the alveolar level with hyperpolarized 3He diffusion MRI.

The study of lung emphysema dates back to the beginning of the 17th century. Nevertheless, a number of important questions remain unanswered because a quantitative localized characterization of emphysema requires knowledge of lung structure at the alveolar level in the intact living lung. This information is not available from traditional imaging modalities and pulmonary function tests.

Wall relaxation of 3He in spin-exchange cells.

The 3He longitudinal spin-relaxation rate T1-1 is crucial for production of highly polarized 3He by spin-exchange optical pumping. We show that T1-1 is increased by a factor of 2-20 solely by exposure of spin-exchange cells to a few-kG magnetic field. The original T1-1 can be restored by degaussing the cell.