Purpose: To use a combination of helium-3 (3-He) magnetic resonance imaging (MRI) and proton single-shot fast spin echo (SSFSE) to compare ventilated lung volumes in groups of "healthy" smokers, smokers diagnosed with moderate chronic obstructive pulmonary disease (COPD), and never-smokers. Materials and Methods:All study participants were assessed with spirometry prior to imaging. 3-He images were collected during an arrested breath hold, after inhaling a mixture of 200 mL of hyperpolarized 3-He/800 mL of N 2 . Proton SSFSE images were acquired after inhaling 1 liter of room air. The ventilated volume for each study participant was calculated from the 3-He images, and a ratio was calculated to give a percentage ventilated lung volume.Results: Never-smokers exhibited a 90% mean ventilated volume. The mean ventilated lung volumes for healthy smokers and smokers diagnosed with COPD were 75.2% and 67.6%, respectively. No correlation with spirometry was demonstrated for either of the smoking groups. Conclusion:Combined 3-He/Proton SSFSE MRI of the lungs is a noninvasive method, using nonionizing radiation, which demonstrates ventilated airspaces and enables the calculation of ventilated lung volumes. This method appears to be sensitive to early obstructive changes in the lungs of smokers. HYPERPOLARIZED HELIUM-3 (3-He) magnetic resonance imaging (MRI) is an emerging technique, which has been shown to produce high-resolution images of ventilated human airspaces (1,2). Proton MRI of the lungs has long been regarded to be of limited use in lung imaging due to cardiac motion artifacts, low proton density, and large magnetic susceptibility gradients associated with lung tissue. However, with ongoing development of fast imaging sequences, proton MRI of the lungs is now enjoying somewhat of a renaissance (3,4). In this work single-shot fast spin echo (SSFSE) breathhold images of the lungs were used to calculate a thoracic volume (5), and 3-He ventilation images were used to calculate a ventilated volume (6 -8) for each study participant. A ratio of ventilated volume to thoracic volume was calculated to give a percentage ventilated lung volume. MATERIALS AND METHODSThe local research ethics committee gave approval, and written informed consent was obtained from each study participant. The lungs of 13 volunteers (5 male, 8 female; mean age ϭ 51; range ϭ 40 -62) and 5 patients with chronic obstructive pulmonary disease (COPD) (2 male, 3 female; mean age ϭ 53; range ϭ 47-61) were imaged using proton SSFSE MRI and 3-He MRI in the coronal plane. All participants were assessed with spirometry prior to imaging and assigned to three groups: eight healthy never-smokers, five "healthy" smokers with a smoking history of Ͼ10 pack years, and five smokers with moderate COPD as demonstrated by spirometry and clinical history. Thus, COPD was defined as a subject who is symptomatic (chronic cough and shortness of breath), and the spirometric indices are 30% Ͻ forced expiratory volume in one second (FEV1) Ͻ 80% of the predicted value in comb...

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A radial projection sliding-window sequence has been developed for imaging the rapid flow of 3 He gas in human lungs. The short echo time (TE) of the radial sequence lends itself to fast repetition times, and thus allows a rapid update in the image when it is reconstructed with a sliding window. Oversampling in the radial direction combined with angular undersampling can further reduce the time needed to acquire a complete image data set, without significantly compromising spatial resolution. Controlled flow phantom experiments using hyperpolarized 3 He gas exemplify the temporal resolution of the method. In vivo studies on three healthy volunteers, one patient with chronic obstructive pulmonary disease (COPD), and one patient with hemiparalysis of the right diaphragm demonstrate that it is possible to accurately resolve the passage of gas down the trachea and bronchi and into the peripheral lung. Hyperpolarized 3 He gas MRI has been shown to be effective in visualizing breath-hold images of ventilation in humans (1). With optical pumping techniques, polarization levels far in excess of those attainable at thermal equilibrium in a B 0 field of 1.5 T can be attained. Because this polarization is not constrained by processes of saturation recovery, imaging with very fast repetition times (TRs) at a high signal-to-noise ratio (SNR) is a realistic prospect in vivo. This has enabled the dynamic study of gas inhalation with repetitive-frame fast imaging techniques. The study of ventilation dynamics may provide insights into lung pathophysiology, including air-trapping in chronic obstructive pulmonary disease (COPD). Previous dynamic studies performed on human subjects have used low flip angle, short-TR spin warp gradient-echo sequences (2,3); gradient-echo EPI (4); and, most recently, interleaved spiral sequences (5). Single-shot EPI might appear to be the logical way to rapidly monitor the passage of inhaled gas, because a flip angle of 90°will convert all the polarization to transverse magnetization in one shot, and subsequent signal can therefore be equated to fresh influx of gas. However, diffusion attenuation constrains the spatial resolution attainable with EPI (4), and field inhomogeneity can severely distort the images in the coronal and sagittal planes. Salerno et al. (5) developed a 24-interleave spiral sequence for dynamic 3 He imaging that offers good spatial resolution, is robust to motion and susceptibility effects, and provides repeated sampling of central and outer kspace per RF excitation (view). This last feature means that fluoroscopic sliding-window reconstruction techniques (6) can be effectively applied, as dynamic contrast changes pertaining to gas flow dynamics are updated on each view. In a study of guinea pig lung ventilation, Viallon et al. (7) presented a radial projection cine sequence. This was used to sample k-space in a continuously revolving pattern. When combined with a sliding-window reconstruction this produced high-quality images with a fast pseudotemporal image refresh rate. The ...