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The assessment of early pulmonary disease and its severity can be difficult in young children, as procedures such as spirometry cannot be performed on them. Computed tomography provides detailed structural images of the pulmonary parenchyma, but its major drawback is that the patient is exposed to ionizing radiation. In this context, magnetic resonance imaging (MRI) is a promising technique for the evaluation of pediatric lung disease, especially when serial imaging is needed. Traditionally, MRI played a small role in evaluating the pulmonary parenchyma. Because of its low proton density, the lungs display low signal intensity on conventional proton-based MRI. Hyperpolarized (HP) gases are inhaled contrast agents with an excellent safety profile and provide high signal within the lung, allowing for high temporal and spatial resolution imaging of the lung airspaces. Besides morphologic information, HP MR images also offer valuable information about pulmonary physiology. HP gas MRI has already made new contributions to the understanding of pediatric lung diseases and may become a clinically useful tool. In this article, we discuss the HP gas MRI technique, special considerations that need to be made when imaging children, and the role of MRI in 2 of the most common chronic pediatric lung diseases, asthma and cystic fibrosis. We also will discuss how HP gas MRI may be used to evaluate normal lung growth and development and the alterations occurring in chronic lung disease of prematurity and in patients with a congenital diaphragmatic hernia.

Although 3He MRI permits compelling visualization of the pulmonary air spaces, quantitation of absolute ventilation is difficult due to confounds such as field inhomogeneity and relative intensity differences between image acquisition; the latter complicating longitudinal investigations of ventilation variation with respiratory alterations. To address these potential difficulties, we present a 4-D segmentation and normalization approach for intra-subject quantitative analysis of lung hyperpolarized 3He MRI. After normalization, which combines bias correction and relative intensity scaling between longitudinal data, partitioning of the lung volume time series is performed by iterating between modeling of the combined intensity histogram as a Gaussian mixture model and modulating the spatial heterogeneity tissue class assignments through Markov random field modeling. Evaluation of the algorithm was retrospectively applied to a cohort of 10 asthmatics between 19-25 years old in which spirometry and 3He MR ventilation images were acquired both before and after respiratory exacerbation by a bronchoconstricting agent (methacholine). Acquisition was repeated under the same conditions from 7 to 467 days (mean ± standard deviation: 185 ± 37.2) later. Several techniques were evaluated for matching intensities between the pre and post-methacholine images with the 95th percentile value histogram matching demonstrating superior correlations with spirometry measures. Subsequent analysis evaluated segmentation parameters for assessing ventilation change in this cohort. Current findings also support previous research that areas of poor ventilation in response to bronchoconstriction are relatively consistent over time.

Accurate characterization of asthma severity is difficult due to the variability of symptoms. Hyperpolarized helium-3 MRI (H3HeMR) is a new technique in which the airspaces are visualized, depicting regions with airflow obstruction as “ventilation defects.” The objective of this study was to compare the extent of H3HeMR ventilation defects with measures of asthma severity and spirometry.

Background: Imaging of gas distribution in the lungs of patients with asthma has been restricted because of the lack of a suitable gaseous contrast agent. Hyperpolarized helium-3 (HHe3) provides a new technique for magnetic resonance imaging of lung diseases. Objective: We sought to investigate the use of HHe3 gas to image the lungs of patients with moderate or severe asthma and to assess changes in gas distribution after methacholine and exercise challenge. Methods: Magnetic resonance imaging was performed in asthmatic patients immediately after inhalation of HHe3 gas. In addition, images were obtained before and after methacholine challenge and a standard exercise test. Results: Areas of the lung with no signal or sharply reduced HHe3 signal (ventilation defects) are common in patients with asthma, and the number of defects was inversely related to the percent predicted FEV1(r= 0.71, P< .002). After methacholine challenge (n = 3), the number of defects increased. Similarly, imaging of the lungs after exercise (n = 6) showed increased ventilation defects in parallel with decreases in FEV1. The increase in defects after challenge in these 9 asthmatic patients was significant both for the number (P< .02) and extent (P< .02) of the defects. The variability and speed of changes in ventilation and the complete lack of signal in many areas is in keeping with a model in which the defects result from airway closure. Conclusion: HHe3 magnetic resonance provides a new technique for imaging the distribution of inhaled air in the lungs. The technique is suitable for following responses to treatment of asthma and changes after methacholine or exercise challenge. (J Allergy Clin Immunol 2003;111:1205-11.)

The nuclear spin polarization of the noble gas isotopes 3He and 129Xe can be increased using optical pumping methods by four to five orders of magnitude. This extraordinary gain in polarization translates directly into a gain in signal strength for MRI. The new technology of hyperpolarized (HP) gas MRI holds enormous potential for enhancing sensitivity and contrast in pulmonary imaging. This review outlines the physics underlying the optical pumping process, imaging strategies coping with the nonequilibrium polarization, and effects of the alveolar microstructure on relaxation and diffusion of the noble gases. It presents recent progress in HP gas MRI and applications ranging from MR microscopy of airspaces to imaging pulmonary function in patients and suggests potential directions for future developments. Magn Reson Med 47:1029–1051, 2002. © 2002 Wiley‐Liss, Inc.

An optimized interleaved‐spiral pulse sequence, providing high spatial and temporal resolution, was developed for dynamic imaging of pulmonary ventilation with hyperpolarized 3He, and tested in healthy volunteers and patients with lung disease. Off‐resonance artifacts were minimized by using a short data‐sampling period per interleaf, and gradient‐fidelity errors were compensated for by using measured k‐space trajectories for image reconstruction. A nonsequential acquisition order was implemented to improve image quality during periods of rapid signal change, such as early inspiration. Using a sliding‐window reconstruction, cine‐movies with a frame rate of 100 images per second were generated. Dynamic images demonstrating minimal susceptibility‐ and motion‐induced artifacts were obtained in sagittal, coronal, and axial orientations. The pulse sequence had the flexibility to image multiple slices almost simultaneously. Our initial experience in healthy volunteers and subjects with lung pathology demonstrated the potential of this new tool for capturing the features of lung gas‐flow dynamics. Magn Reson Med 4:667–677, 2001. © 2001 Wiley‐Liss, Inc.

Asthma is a disease characterized by chronic inflammation and reversible obstruction of the small airways resulting in impaired pulmonary ventilation. Hyperpolarized 3He magnetic resonance (MR) lung imaging is a new technology that provides a detailed image of lung ventilation. Hyperpolarized 3He lung imaging was performed in 10 asthmatics and 10 healthy subjects. Seven asthmatics had ventilation defects distributed throughout the lungs compared with none of the normal subjects. These ventilation defects were more numerous and larger in the two symptomatic asthmatics who had abnormal spirometry. Ventilation defects studied over time demonstrated no change in appearance over 30–60 minutes. One asthmatic subject was studied twice in a three‐week period and had ventilation defects which resolved and appeared in that time. This same subject was studied before and after bronchodilator therapy, and all ventilation defects resolved after therapy. Hyperpolarized 3He lung imaging can detect the small, reversible ventilation defects that characterize asthma. The ability to visualize lung ventilation offers a direct method of assessing asthmatics and their response to therapy. J. Magn. Reson. Imaging 2001;13:378–384. © 2001 Wiley‐Liss, Inc.

The safety data from the phase II clinical trial of ferumoxtran‐10, an ultrasmall superparamagnetic iron oxide contrast agent, are presented. One hundred and four patients with focal liver or spleen pathologies underwent ferumoxtran‐10‐enhanced magnetic resonance (MR) imaging at doses of 0.8, 1.1, and 1.7 mg Fe/kg. Overall, 15% patients reported a total of 33 adverse events, regardless of causality. The adverse events most frequently seen were dyspnea (3.8%), chest pain (2.9%), and rash (2.9%). No serious adverse events were reported during the 48 hour observation period. There were no clinically significant effects on vital signs, physical examination, and laboratory results. Ferumoxtran‐10 is a safe and well tolerated MR contrast agent.J. Magn. Reson. Imaging 1999;9:291–294. © 1999 Wiley‐Liss, Inc.

The purpose of this study was to evaluate the safety and efficacy of a manganese chloride‐based oral magnetic resonance (MR) contrast agent during a Phase III multisite clinical trial. Two hundred seventeen patients were enrolled who were already scheduled for MRI of the abdomen and/or pelvis. In this group of patients, it was postulated that the use of an oral agent would better allow discrimination of pathology from bowel. Patients with known gastrointestinal pathology including peptic ulcer disease, inflammatory bowel disease, obstruction, or perforation were excluded to minimize confounding variables that could affect the safety assessment. Of these 217 patients, 18 received up to 900 mL of placebo, and 199 patients were given up to 900 mL of a manganese chloride‐based oral contrast agent, LumenHance® (Bracco Diagnostics, Inc.). Safety was determined by comparing pre‐ and post‐dose physical examinations, vital signs, and laboratory examinations and by documenting adverse events. Efficacy was assessed by unblinded site investigators and two blinded reviewers who compared pre‐ and post‐dose T1‐ and T2‐weighted MRI scans of the abdomen and/or pelvis. In 111 (57%) of the 195 cases evaluated for efficacy by site investigators (unblinded readers), MRI after LumenHance provided additional diagnostic information. Increased information was found by two blinded readers in 52% and 51% of patients, respectively. In 44/195 cases (23%) unblinded readers felt the additional information would have changed patient diagnosis and in 50 patients (26%), it would have changed management and/or therapy. Potential changes in patient diagnosis or management/therapy were seen by the two blinded readers in 8–20% of patients. No clinically significant post‐dose laboratory changes were seen. Forty‐eight patients (24%) receiving LumenHance and four patients (22%) receiving placebo experienced one or more adverse events. Gastrointestinal tract side effects were most common, seen in 29 (15%) of LumenHance patients and in 3 (17%) of the placebo patients. LumenHance is a safe and efficacious oral gastrointestinal contrast agent for MRI of the abdomen and pelvis.J. Magn. Reson. Imaging 1999;10:15–24. © 1999 Wiley‐Liss, Inc.

Purpose:To determine the accuracy and optimal threshold values of duplex ultrasonography (US) in assessing restenosis of renal artery stents.

Using a new method of xenon laser‐polarization that permits the generation of liter quantities of hyperpolarized 129Xe gas, the first 129Xe imaging results from the human chest and the first 129Xe spectroscopy results from the human chest and head have been obtained. With polarization levels of approximately 2%, cross‐sectional images of the lung gas‐spaces with a voxel volume of 0.9 cm3(signal‐to‐noise ratio (SNR), 28) were acquired and three dissolved‐phase resonances in spectra from the chest were detected. In spectra from the head, one prominent dissolved‐phase resonance, presumably from brain parenchyma, was detected. With anticipated improvements in the 129Xe polarization system, pulse sequences, RF coils, and breathing maneuvers, these results suggest the possibility for 129Xe gas‐phase imaging of the lungs with a resolution approaching that of current conventional thoracic proton imaging. Moreover, the results suggest the feasibility of dissolved‐phase imaging of both the chest and brain with a resolution similar to that obtained with the gas‐phase images.

Changes in uterine zonal anatomy in six women during a cycle of treatment with clomiphene citrate is studied by magnetic resonance imaging. There was a rapid rate of increase in endometrial thickness during the periovulatory period that was similar to the pattern seen in a prior study of women with normal (nonstimulated) cycles. Junctional zone thickness did not parallel the endometrial pattern and differed from the response seen in nonstimulated cycles. Results of large scale studies may help to further understand the effects of these medications.

A better understanding of the imaging features, patterns of growth, classification systems, and surgical resectability of cholangiocarcinomas can help radiologists guide surgical management and treatment.