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The assessment of both pulmonary perfusion and ventilation is of crucial importance for a proper diagnosis of some lung diseases such as pulmonary embolism. In this study, we demonstrate the feasibility of combined magnetic resonance imaging lung ventilation and perfusion performed serially in rat lungs. Lung ventilation function was assessed using hyperpolarized 3He, and lung perfusion proton imaging was demonstrated using contrast agent injection. Both imaging techniques have been implemented using projection‐reconstruction sequences with free induction decay signal acquisitions. The study focused on fast three‐dimensional (3D) data acquisition. The projection‐reconstruction sequences used in this study allowed 3D data set acquisition in several minutes without high‐performance gradients. 3D proton perfusion/helium ventilation imaging has been demonstrated on an experimental rat model of pulmonary embolism showing normal lung ventilation associated with lung perfusion defect. Assuming the possibility, still under investigation, of showing lung obstruction pathologies using 3He imaging, these combined perfusion/ventilation methods could play a significant clinical role in the future for diagnosis of several pulmonary diseases. Magn Reson Med 41:645–648, 1999. © 1999 Wiley‐Liss, Inc.

The assessment of both pulmonary perfusion and ventilation is of crucial importance for a proper diagnosis of some lung diseases such as pulmonary embolism. In this study, we demonstrate the feasibility of combined magnetic resonance imaging lung ventilation and perfusion performed serially in rat lungs. Lung ventilation function was assessed using hyperpolarized ³He, and lung perfusion proton imaging was demonstrated using contrast agent injection. Both imaging techniques have been implemented using projection-reconstruction sequences with free induction decay signal acquisitions. The study focused on fast three-dimensional (3D) data acquisition. The projection-reconstruction sequences used in this study allowed 3D data set acquisition in several minutes without high-performance gradients. 3D proton perfusion/helium ventilation imaging has been demonstrated on an experimental rat model of pulmonary embolism showing normal lung ventilation associated with lung perfusion defect. Assuming the possibility, still under investigation, of showing lung obstruction pathologies using ³He imaging, these combined perfusion/ventilation methods could play a significant clinical role in the future for diagnosis of several pulmonary diseases. Magn Reson Med 41:645–648, 1999. © 1999 Wiley-Liss, Inc.

AbstractNeutron Spin-Filters (NSF) using gaseous polarized 3He have long been recognized as having enormous potential value in many polarized neutron scattering applications and, accordingly, ILL started a development program some years ago. This report gives an account of the present status of the project. Let us first briefly recall the reasons why the 3He-NSF is desirable as a generic polarization tool:Being a pure transmission device, NSF naturally decouples the neutron spin selection from other optical functions. Designing polarized instruments will be simplified having no geometrical constraints due to Bragg optics or beam deviation in the polarizer. Angular acceptance and energy band pass are much widened, making polarization handling much more compatible with focusing geometry and time of flight techniques.Gaseous NSF naturally achieves well-defined transmission functions. Quantitative interpretation of intensity measurements in polarization analysis mode will be much easier. Very homogeneous polarization will be achieved on large beam areas, a feature which is particularly attractive for precision measurements.Fully polarized 3He is meant to be an ideally effective NSF with 50 percent transmission of the incident unpolarized beam. Already with half 3He polarization, it seems that NSF can improve some existing instruments when polarizing crystals or super mirrors are not good reflectors. To understand this point, it is important to define and calculate a relevant quality factor in order to properly handle the tradeoff in between neutron polarization and neutron flux. As an example, we have been able to show [I] that the inverse standard deviation in the measurement of small magnetic structure factors is proportional to PdT, P being the neutron beam polarization and T the filter transmission. At optimum gas pressure, this quantity turns to be linearly proportional to the 3He polarization in such a way that we can say that present NSF are only a factor of two away from ideal. Improving the 3He polarization remains most important for polarization analysis work, where this quality factor is generally squared.