Iron content of the basal ganglia was investigated in 25 patients with idiopathic Parkinson's disease and 14 matched healthy control subjects using a partially refocused interleaved multiple echo sequence on a 1.5 Tesla MRI system. R(2)* (1/T(2)*) and R(2)' (1/T(2)') relaxation rates were higher in the substantia nigra of patients with Parkinson's disease, which indicates that iron content is elevated in this region. R(2)' was lower in the putamen, indicating reduced iron levels; reduction in this region was positively correlated with disease duration. Iron-related oxidative stress may contribute to the neurodegeneration of Parkinson's disease, which may lead to alterations in the iron levels of the striatum. We describe a simple, non-invasive technique for measuring iron content.

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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Mathematical models are required to estimate kinetic parameters of [1-(13)C] pyruvate-lactate interconversion from magnetic resonance spectroscopy data. One- or two-way exchange models utilizing a hypothetical approximation to the true arterial input function (AIF), (e.g. an ideal 'box-car' function) have been used previously. We present a method for direct measurement of the AIF in the rat. The hyperpolarized [1-(13)C] pyruvate signal was measured in arterial blood as it was continuously withdrawn through a small chamber. The measured signal was corrected for T1 relaxation of pyruvate, RF pulses and dispersion of blood in the chamber to allow for the estimation of the direct AIF. Using direct AIF, rather than the commonly used box-car AIF, provided realistic estimates of the rate constant of conversion of pyruvate to lactate, kpl, the rate constant of conversion of lactate to pyruvate klp, the clearance rate constant of pyruvate from blood to tissue, Kip, and the relaxation rate of lactate T1la. Since no lactate signal was present in blood, it was possible to use a simple precursor-product relationship, with the tumor tissue pyruvate time-course as the input for the lactate time-course. This provided a robust estimate of kpl, similar to that obtained using a directly measured AIF.

Purpose:To estimate the levels of basal ganglia iron levels in Parkinson's disease (PD) using the PRIME MR sequence at 3.0 Tesla, in relation to patients' motor symptom severity. Materials and Methods:Seventy patients with PD and 10 healthy controls underwent assessment of movement and MR imaging. Mean R 2 Ј relaxation rates were recorded in the substantia nigra, frontal white matter and in the rostral, mid, and caudal putamen.Results: R 2 Ј relaxation rates were significantly higher in patients with PD than in healthy controls. R 2 Ј in the most affected substantia nigra correlated with PD patients' motor symptom severity, but not with disease duration. Neuroradiological observation revealed a rostral to caudal "gradient" of putaminal hypointensity. This was substantiated by the finding that the mid and caudal putamen showed significantly higher R 2 Ј relaxation rates, consistent with higher iron levels in PD relative to the healthy controls.Conclusion: MRI at 3.0 Tesla suggests that substantia nigra iron levels are increased and linked to the severity of motor symptoms experienced in PD. Findings consistent with increased iron levels in the PD putamen are shown, in a region-specific rostral to caudal gradient.

High angular resolution diffusion tensor imaging may be more sensitive than conventional MRI or neurologic assessment to the upper motor neuron (UMN) pathology of ALS, but it lacks the specificity required of a diagnostic marker. Instead, it is potentially useful as a quantitative tool for monitoring the progression of UMN pathology.

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 ...

A method for 3D volume-localized quantification of pO2 in the lungs is presented that uses repetitive frame 3D gradient-echo imaging of 3 He. The method was demonstrated by experiments on 3 He phantoms containing known concentrations of O 2 and in vivo on a group of three healthy human volunteers. The results were compared with those obtained by equivalent 2D thin-slice and 2D projection methodologies, and were found to be consistent with published results from the 2D projection methodologies (pO 2 ‫؍‬ 0.09 -0.18 bar). Studies performed on the same subject, on three separate occasions, demonstrated a repeatability of pO 2 measurement to within 14% using the 3D technique. Experimental differences between the 2D and 3D methods were substantiated with theoretical and numerical analyses of the signal decay, which took into account the effects of out-of-slice diffusion as a source of error in the thin-slice 2D experiments. It is shown that the 2D thin-slice technique systematically underestimates pO2 when there is significant gas diffusion (factor of 4 underestimate for D ‫؍‬ 0.9 cm MRI of hyperpolarized (HP)3 He gas can provide high spatial and temporal resolution images of gas ventilation in the lungs and airways, as well as useful functional information (1). Potentially one of the most useful functional parameters is an estimate of the partial pressure of oxygen (pO 2 ) in the lungs and the rate of oxygen extraction (2-6). Accurate spatially localized pO 2 measurement with 3 He MRI would be clinically useful as a means of assessing lung ventilation-perfusion (V/Q). When paramagnetic oxygen mixes with polarized 3 He in the lungs, a marked reduction in the 3 He T 1 arises through the electron-nuclear spin dipolar coupling. Saam et al. (7) quantified the dependence of the 3 He T 1 on oxygen concentration with phantom experiments. This O 2 dependence of the 3 He T 1 was used by Deninger et al. (2,3) for in vivo quantification of pO 2 in a series of breath-hold experiments on pigs and humans. These in vivo experiments used images acquired from whole-lung projections (very thick 2D slices). This was done to maximize the signal-to-noise ratio (SNR) and to circumvent diffusion of polarized gas out of the slice during the significant inter-image delay time (typically up to 7 s) as a possible source of change in the time course of the in vivo 3 He signal. Moller et al. (5) estimated the degree of partial volume mixing of polarization due to gas diffusion for a 2D thin-slice experiment in the guinea pig lung. Assuming a 24 s total acquisition time and an apparent diffusion coefficient of D ϭ 0.16 cm 2 s -1 , they predicted that only 5% of the in-slice magnetization would be exchanged between adjacent slices. In addition, the recently published results by Jalali et al. (6) from 2D pO 2 experiments in porcine lungs, with 2-cm-thick slices, are in fair agreement with the results from a 2D porcine study with 18-cm-thick slices (2). These results suggest that diffusion between slices may not be a considerable problem; however, a...