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Purpose: To investigate short- and long-time-scale (3)He diffusion in asthma.Materials and Methods: A hybrid MRI sequence was developed to obtain co-registered short- and long-time-scale apparent diffusion coefficient (ADC) maps during a single breath-hold. The study groups were: asthma (n = 14); healthy (n = 14); chronic obstructive pulmonary disease (COPD) (n = 9). Correlations were made between mean-ADC and %ADC-abn (abnormal) (%pixels with ADC > mean +2 SD of healthy) at both time scales and spirometry. Sensitivities were determined using receiver operating characteristic (ROC) analysis.Results: For asthmatics, the short- and long-time-scale group-mean ADCs were 0.254 +/- 0.032 cm(2)/s and 0.0237 +/- 0.0055 cm(2)/s, respectively, representing a 9% and 27% (P = 0.038 and P = 0.005) increase compared to the healthy group. The group-mean %ADC-abn were 6.4% +/- 3.7% and 17.5% +/- 14.2%, representing a 107% and 272% (P = 0.004 and P = 0.006) increase. For COPD much greater elevations were observed. %ADC-abn provided better discrimination than mean-ADC between asthmatic and healthy subjects. In asthmatics ADC did not correlate with spirometry.Conclusion: With long-time scale (3)He diffusion magnetic resonance imaging (MRI) changes in lung microstructure were detected in asthma that more conspicuous regionally than at the short time scale. The hybrid diffusion method is a novel means of identifying small airway disease. [ABSTRACT FROM AUTHOR]

Purpose: To develop and test compressed sensing-based multiframe 3D MRI of grid-tagged hyperpolarized gas in the lung., Theory and Methods: Applying grid-tagging RF pulses to inhaled hyperpolarized gas results in images in which signal intensity is predictably and sparsely distributed. In the present work, this phenomenon was used to produce a sampling pattern in which k-space is undersampled by a factor of approximately seven, yet regions of high k-space energy remain densely sampled. Three healthy subjects received multiframe 3D 3 He tagging MRI using this undersampling method. Images were collected during a single exhalation at eight timepoints spanning the breathing cycle from end-of-inhalation to end-of-exhalation. Grid-tagged images were used to generate 3D displacement maps of the lung during exhalation, and time-resolved maps of principal strains and fractional volume change were generated from these displacement maps using finite-element analysis., Results: Tags remained clearly resolvable for 4-6 timepoints (5-8 s) in each subject. Displacement maps revealed noteworthy temporal and spatial nonlinearities in lung motion during exhalation. Compressive normal strains occurred along all three principal directions but were primarily oriented in the head-foot direction. Fractional volume changes displayed clear bilateral symmetry, but with the lower lobes displaying slightly higher change than the upper lobes in 2 of the 3 subjects., Conclusion: We developed a compressed sensing-based method for multiframe 3D MRI of grid-tagged hyperpolarized gas in the lung during exhalation. This method successfully overcomes previous challenges for 3D dynamic grid-tagging, allowing time-resolved biomechanical readouts of lung function to be generated., (© 2023 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals LLC on behalf of International Society for Magnetic Resonance in Medicine.)

Background: Hyperpolarized gas with helium (HHe-3) MR (magnetic resonance) is a noninvasive imaging method which maps and quantifies regions of ventilation heterogeneity (VH) in the lung. VH is an important feature of asthma, but little is known as to how VH informs patient phenotypes., Purpose: To determine if VH indicators quantified by HHe-3 MR imaging (MRI) predict phenotypic characteristics and map to regions of inflammation in children with problematic wheeze or asthma., Methods: Sixty children with poorly-controlled wheeze or asthma underwent HHe-3 MRI, including 22 with bronchoalveolar lavage (BAL). The HHe-3 signal intensity defined four ventilation compartments. The non-ventilated and hypoventilated compartments divided by the total lung volume defined a VH index (VHI %)., Results: Children with VHI % in the upper quartile had significantly greater airflow limitation, bronchodilator responsiveness, blood eosinophils, expired nitric oxide (FeNO), and BAL eosinophilic or neutrophilic granulocyte patterns compared to children with VHI % in the lower quartile. Lavage return from hypoventilated bronchial segments had greater eosinophil % than from ventilated segments., Conclusion: In children with asthma, greater VHI % as measured by HHe-3 MRI identifies a severe phenotype with higher type 2 inflammatory markers, and maps to regions of lung eosinophilia. Listed on ClinicalTrials. gov (NCT02577497)., (© 2021 Wiley Periodicals LLC.)

Background Apparent diffusion coefficient (ADC) maps of inhaled hyperpolarized gases have shown promise in the characterization of emphysema in patients with chronic obstructive pulmonary disease (COPD), yet an easily interpreted quantitative metric beyond mean and standard deviation has not been established. Purpose To introduce a quantitative framework with which to characterize emphysema burden based on hyperpolarized helium 3 ( 3 He) and xenon 129 ( 129 Xe) ADC maps and compare its diagnostic performance with CT-based emphysema metrics and pulmonary function tests (PFTs). Materials and Methods Twenty-seven patients with mild, moderate, or severe COPD and 13 age-matched healthy control subjects participated in this retrospective study. Participants underwent CT and multiple b value diffusion-weighted 3 He and 129 Xe MRI examinations and standard PFTs between August 2014 and November 2017. ADC-based emphysema index was computed separately for each gas and b value as the fraction of lung voxels with ADC values greater than in the healthy group 99th percentile. The resulting values were compared with quantitative CT results (relative lung area <-950 HU) as the reference standard. Diagnostic performance metrics included area under the receiver operating characteristic curve (AUC). Spearman rank correlations and Wilcoxon rank sum tests were performed between ADC-, CT-, and PFT-based metrics, and intraclass correlation was performed between repeated measurements. Results Thirty-six participants were evaluated (mean age, 60 years ± 6 [standard deviation]; 20 women). ADC-based emphysema index was highly repeatable (intraclass correlation coefficient > 0.99) and strongly correlated with quantitative CT ( r = 0.86, P < .001 for 3 He; r = 0.85, P < .001 for 129 Xe) with high AUC (≥0.93; 95% confidence interval [CI]: 0.85, 1.00). ADC emphysema indices were also correlated with percentage of predicted diffusing capacity of lung for carbon monoxide ( r = -0.81, P < .001 for 3 He; r = -0.80, P < .001 for 129 Xe) and percentage of predicted residual lung volume divided by total lung capacity ( r = 0.65, P < .001 for 3 He; r = 0.61, P < .001 for 129 Xe). Conclusion Emphysema index based on hyperpolarized helium 3 or xenon 129 diffusion MRI provides a repeatable measure of emphysema burden, independent of gas or b value, with similar diagnostic performance as quantitative CT or pulmonary function metrics. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Schiebler and Fain in this issue.

The aim of this work was to develop a novel hybrid 3D hyperpolarized (HP) gas tagging MRI (t-MRI) technique and to evaluate it for lung respiratory motion measurement with comparison to deformable image registrations (DIR) methods. Three healthy subjects underwent a hybrid MRI which combines 3D HP gas t-MRI with a low resolution (Low-R, 4.5 mm isotropic voxels) 3D proton MRI (p-MRI), plus a high resolution (High-R, 2.5 mm isotropic voxels) 3D p-MRI, during breath-holds at the end-of-inhalation (EOI) and the end-of-exhalation (EOE). Displacement vector field (DVF) of the lung motion was determined from the t-MRI images by tracking tagging grids and from the High-R p-MRI using three DIR methods (B-spline based method implemented by Velocity, Free Form Deformation by MIM, and B-spline by an open source software Elastix: denoted as A, B, and C, respectively), labeled as tDVF and dDVF, respectively. The tDVF from the HP gas t-MRI was used as ground-truth reference to evaluate performance of the three DIR methods. Differences in both magnitude and angle between the tDVF and dDVFs were analyzed. The mean lung motion of the three subjects was 37.3 mm, 8.9 mm and 12.9 mm, respectively. Relatively large discrepancies were observed between the tDVF and the dDVFs as compared to previously reported DIR errors. The mean  ±  standard deviation (SD) DVF magnitude difference was 8.3  ±  5.6 mm, 9.2  ±  4.5 mm, and 9.3  ±  6.1 mm, and the mean  ±  SD DVF angular difference was 29.1  ±  12.1°, 50.1  ±  28.6°, and 39.0  ±  6.3°, for the DIR Methods A, B, and C, respectively. These preliminary results showed that the hybrid HP gas t-MRI technique revealed different lung motion patterns as compared to the DIR methods. It may provide unique perspectives in developing and evaluating DIR of the lungs. Novelty and Significance We designed a MRI protocol that includes a novel hybrid MRI technique (3D HP gas t-MRI with a low resolution 3D p-MRI) plus a high resolution 3D p-MRI. We tested the novel hybrid MRI technique on three healthy subjects for measuring regional lung respiratory motion with comparison to deformable image registrations (DIR) methods, and observed relatively large discrepancies in lung motion between HP gas t-MRI and DIR methods.

Background: Deformable image registration (DIR)-based lung ventilation mapping is attractive due to its simplicity, and also challenging due to its susceptibility to errors and uncertainties. In this study, we explored the use of 3D Hyperpolarized (HP) gas tagging MRI to evaluate DIR-based lung ventilation., Method and Material: Three healthy volunteers included in this study underwent both 3D HP gas tagging MRI (t-MRI) and 3D proton MRI (p-MRI) using balanced steady-state free precession pulse sequence at end of inhalation and end of exhalation. We first obtained the reference displacement vector fields (DVFs) from the t-MRIs by tracking the motion of each tagging grid between the exhalation and the inhalation phases. Then, we determined DIR-based DVFs from the p-MRIs by registering the images at the two phases with two commercial DIR algorithms. Lung ventilations were calculated from both the reference DVFs and the DIR-based DVFs using the Jacobian method and then compared using cross correlation and mutual information., Results: The DIR-based lung ventilations calculated using p-MRI varied considerably from the reference lung ventilations based on t-MRI among all three subjects. The lung ventilations generated using Velocity AI were preferable for the better spatial homogeneity and accuracy compared to the ones using MIM, with higher average cross correlation (0.328 vs 0.262) and larger average mutual information (0.528 vs 0.323)., Conclusion: We demonstrated that different DIR algorithms resulted in different lung ventilation maps due to underlining differences in the DVFs. HP gas tagging MRI provides a unique platform for evaluating DIR-based lung ventilation., (© 2018 American Association of Physicists in Medicine.)

Objective: The purpose of this study was to determine whether unenhanced MRI without sedation is a feasible substitute for dimercaptosuccinic acid (DMSA) scintigraphy in the detection of renal scars in pediatric patients., Subjects and Methods: Patients scheduled for 99m Tc-labeled DMSA scintigraphy for assessment of possible renal scars were recruited to undergo unenhanced MRI (free-breathing fat-suppressed T2-weighted single-shot turbo spin-echo and T1-weighted gradient-echo imaging, 13 minutes' total imaging time). Scintigraphic and MRI studies were evaluated by two independent blinded specialty-based radiologists. For each imaging examination, readers identified scars in upper, middle, and lower kidney zones and rated their diagnostic confidence and the quality of each study. The scintigraphic readers' consensus score opinion for the presence of scars was considered the reference standard., Results: DMSA scintigraphy showed scarring in 19 of the 78 (24.4%) evaluated zones and MRI in 18 of the 78 (23.1%). The two MRI readers found mean sensitivities of 94.7% and 89.5%, identical specificities of 100%, and diagnostic accuracies of 98.7% and 97.4%. Interobserver agreement was 98.7% for MRI and 92.3% for DMSA scintigraphy. The MRI readers were significantly more confident in determining the absence rather than the presence of scars (p = 0.02). MRI readers were more likely to rate study quality as excellent (84.6%) than were the scintigraphic readers (57.7%) (p = 0.024)., Conclusion: Unenhanced MRI has excellent sensitivity, specificity, diagnostic accuracy, and interobserver agreement for detecting renal scars in older children who do not need sedation. It may serve as a substitute modality, especially when DMSA is not available.

Purpose: To evaluate T 2 , T2*, and signal-to-noise ratio (SNR) for hyperpolarized helium-3 ( 3 He) MRI of the human lung at three magnetic field strengths ranging from 0.43T to 1.5T., Methods: Sixteen healthy volunteers were imaged using a commercial whole body scanner at 0.43T, 0.79T, and 1.5T. Whole-lung T 2 values were calculated from a Carr-Purcell-Meiboom-Gill spin-echo-train acquisition. T2* maps and SNR were determined from dual-echo and single-echo gradient-echo images, respectively. Mean whole-lung SNR values were normalized by ventilated lung volume and administered 3 He dose., Results: As expected, T 2 and T2* values demonstrated a significant inverse relationship to field strength. Hyperpolarized 3 He images acquired at all three field strengths had comparable SNR values and thus appeared visually very similar. Nonetheless, the relatively small SNR differences among field strengths were statistically significant., Conclusions: Hyperpolarized 3 He images of the human lung with similar image quality were obtained at three field strengths ranging from 0.43T and 1.5T. The decrease in susceptibility effects at lower fields that are reflected in longer T 2 and T2* values may be advantageous for optimizing pulse sequences inherently sensitive to such effects. The three-fold increase in T2* at lower field strength would allow lower receiver bandwidths, providing a concomitant decrease in noise and relative increase in SNR. Magn Reson Med 78:1458-1463, 2017. © 2016 International Society for Magnetic Resonance in Medicine., (© 2016 International Society for Magnetic Resonance in Medicine.)

Purpose: To develop and evaluate a protocol for hyperpolarized helium-3 (HHe) ventilation magnetic resonance imaging (MRI) of the lungs of non-sedated infants and children., Materials and Methods: HHe ventilation MRI was performed on seven children ≤4years old. Contiguous 2D-spiral helium-3 images were acquired sequentially with a scan time of ≤0.2s/slice., Results: Motion-artifact-free, high signal-to-noise ratio (SNR) images of lung ventilation were obtained. Gas was homogeneously distributed in healthy individuals; focal ventilation defects were found in patients with respiratory diseases., Conclusion: HHe ventilation MRI can aid assessment of pediatric lung disease even at a young age., (Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.)

Purpose: The aim of the study was to determine whether hyperpolarized He diffusion-weighted magnetic resonance imaging detects abnormalities in the lungs in children with bronchopulmonary dysplasia (BPD) as compared with age-matched normal children., Materials and Methods: All experiments were compliant with Health Insurance Portability and Accountability Act (HIPAA) and performed with Food and Drug Administration approval under an IND application. The protocol was approved by our Institutional Review Board, and written informed consent was obtained. Hyperpolarized He diffusion-weighted magnetic resonance imaging was performed in 16 subjects with a history of preterm birth complicated by BPD (age range, 6.8 to 13.5 y; mean, 9.0 y) and in 29 healthy term-birth subjects (age range, 4.5-14.7 y; mean, 9.2 y) using a gradient-echo sequence with bipolar diffusion gradients and with measurements at 2 b values (0 and 1.6 s/cm). Age-related comparison of the whole-lung mean apparent diffusion coefficient (ADC), 90th percentile ADC, and percentage of whole-lung volume with ADC>0.2 cm/s between the 2 groups was examined using ordinary least-squares multiple regression., Results: The mean ADC was significantly greater in subjects with BPD (0.187 vs. 0.152 cm/s, P<0.001). The 90th percentile ADC and mean percentage lung volume with ADC>0.2 cm/s were also higher in the BPD group (0.258 vs. 0.215 cm/s, 30.3% vs. 11.9%, P<0.001 for both). The body surface area-adjusted ventilated lung volume was similar in the 2 groups (1.93 vs. 1.91 L, P=0.90)., Conclusions: Children with BPD had higher ADCs and the same lung volumes when compared with age-matched healthy subjects, suggesting that children with BPD have enlarged alveoli that are reduced in number.

Background: This pilot study evaluated the effect of short- and long-term ivacaftor treatment on hyperpolarized 3 He-magnetic resonance imaging (MRI)-defined ventilation defects in patients with cystic fibrosis aged ≥12years with a G551D-CFTR mutation., Methods: Part A (single-blind) comprised 4weeks of ivacaftor treatment; Part B (open-label) comprised 48weeks of treatment. The primary outcome was change from baseline in total ventilation defect (TVD; total defect volume:total lung volume ratio)., Results: Mean change in TVD ranged from -8.2% (p=0.0547) to -12.8% (p=0.0078) in Part A (n=8) and -6.3% (p=0.1953) to -9.0% (p=0.0547) in Part B (n=8) as assessed by human reader and computer algorithm, respectively., Conclusions: TVD responded to ivacaftor therapy. 3 He-MRI provides an individual quantification of disease burden that may be able to detect aspects of the disease missed by population-based spirometry metrics. Assessments by human reader and computer algorithm exhibit similar trends, but the latter appears more sensitive. www.clinicaltrials.gov identifier: NCT01161537., (Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.)

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.

Background: Lung ventilation defects identified by using hyperpolarized 3-helium gas ((3)He) lung magnetic resonance imaging (MRI) are prevalent in asthmatic patients, but the clinical importance of ventilation defects is poorly understood., Objectives: We sought to correlate the lung defect volume quantified by using (3)He MRI with clinical features in children with mild and severe asthma., Methods: Thirty-one children with asthma (median age, 10 years; age range, 3-17 years) underwent detailed characterization and (3)He lung MRI. Quantification of the (3)He signal defined ventilation defect and hypoventilated, ventilated, and well-ventilated volumes., Results: The ventilation defect to total lung volume fraction ranged from 0.1% to 11.6%. Children with ventilation defect percentages in the upper tercile were more likely to have severe asthma than children in the lower terciles (P = .005). The ventilation defect percentage correlated (P < .05 for all) positively with the inhaled corticosteroid dose, total number of controller medications, and total blood eosinophil counts and negatively with the Asthma Control Test score, FEV1 (percent predicted), FEV1/forced vital capacity ratio (percent predicted), and forced expiratory flow rate from 25% to 75% of expired volume (percent predicted)., Conclusion: The lung defect volume percentage measured by using (3)He MRI correlates with several clinical features of asthma, including severity, symptom score, medication requirement, airway physiology, and atopic markers., (Copyright © 2015 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.)

Purpose: To evaluate regional anisotropy of lung-airspace orientation by assessing the dependence of helium-3 ((3) He) apparent diffusion coefficient (ADC) values on the direction of diffusion sensitization at two field strengths., Materials and Methods: Hyperpolarized (3) He diffusion-weighted magnetic resonance imaging (MRI) of the lung was performed at 0.43T and 1.5T in 12 healthy volunteers. A gradient-echo pulse sequence was used with a bipolar diffusion-sensitization gradient applied separately along three orthogonal directions. ADC maps, median ADC values, and signal-to-noise ratios were calculated from the diffusion-weighted images. Two readers scored the ADC maps for increased values at lung margins, major fissures, or within focal central regions., Results: ADC values were found to depend on the direction of diffusion sensitization (P < 0.01, except for craniocaudal vs. anteroposterior directions at 1.5T) and were increased at the lateral and medial surfaces for left-right diffusion sensitization (12 of 12 subjects); at the apex and base (9 of 12), and along the major fissure (8 of 12), for craniocaudal diffusion sensitization; and at the most anterior and posterior lung (10 of 12) for anteroposterior diffusion sensitization. Median ADC values at 0.43T (0.201 ± 0.017, left-right; 0.193 ± 0.019, craniocaudal; and 0.187 ± 0.017 cm(2) /s, anteroposterior) were slightly lower than those at 1.5T (0.205 ± 0.017, 0.197 ± 0.017 and 0.194 ± 0.016 cm(2) /s, respectively; P < 0.05)., Conclusion: These findings indicate that diffusion-weighted hyperpolarized (3) He MRI can detect regional anisotropy of lung-airspace orientation, including that associated with preferential orientation of terminal airways near pleural surfaces., (© 2015 Wiley Periodicals, Inc.)

Purpose: We aimed to evaluate the safety and efficacy of fluoroscopically placed jejunal extension tubes (J-arm) in patients with existing gastrostomy tubes., Methods: We conducted a retrospective review of 391 J-arm placements performed in 174 patients. Indications for jejunal nutrition were aspiration risk (35%), pancreatitis (17%), gastroparesis (13%), gastric outlet obstruction (12%), and other (23%). Technical success, complications, malfunctions, and patency were assessed. Percutaneous gastrostomy (PEG) tube location, J-arm course, and fluoroscopy time were correlated with success/failure. Failure was defined as inability to exit the stomach. Procedure-related complications were defined as adverse events related to tube placement occurring within seven days. Tube malfunctions and aspiration events were recorded and assessed., Results: Technical success was achieved in 91.9% (95% CI, 86.7%-95.2%) of new tubes versus 94.2% (95% CI, 86.7%-95.2%) of replacements (P = 0.373). Periprocedural complications occurred in three patients (0.8%). Malfunctions occurred in 197 patients (50%). Median tube patency was 103 days (95% CI, 71-134 days). No association was found between successful J-arm placement and gastric PEG tube position (P = 0.677), indication for jejunal nutrition (P = 0.349), J-arm trajectory in the stomach and incidence of malfunction (P = 0.365), risk of tube migration and PEG tube position (P = 0.173), or J-arm length (P = 0.987). A fluoroscopy time of 21.3 min was identified as a threshold for failure. Malfunctions occurred more often in tubes replaced after 90 days than in tubes replaced before 90 days (P < 0.001). A total of 42 aspiration events occurred (OR 6.4, P < 0.001, compared with nonmalfunctioning tubes)., Conclusion: Fluoroscopy-guided J-arm placement is safe for patients requiring jejunal nutrition. Tubes indwelling for longer than 90 days have higher rates of malfunction and aspiration.

Purpose: To develop and validate a method for acquiring helium-3 ((3) He) and proton ((1) H) three-dimensional (3D) image sets of the human lung with isotropic spatial resolution within a 10-s breath-hold by using compressed sensing (CS) acceleration, and to assess the fidelity of undersampled images compared with fully sampled images., Methods: The undersampling scheme for CS acceleration was optimized and tested using (3) He ventilation data. Rapid 3D acquisition of both (3) He and (1) H data during one breath-hold was then implemented, based on a balanced steady-state free-precession pulse sequence, by random undersampling of k-space with reconstruction by means of minimizing the L1 norm and total variance. CS-reconstruction fidelity was evaluated quantitatively by comparing fully sampled and retrospectively undersampled image sets., Results: Helium-3 and (1) H 3D image sets of the lung with isotropic 3.9-mm resolution were acquired during a single breath-hold in 12 s and 8 s using acceleration factors of 2 and 3, respectively. Comparison of fully sampled and retrospectively undersampled (3) He and (1) H images yielded mean absolute errors <10% and structural similarity indices >0.9., Conclusion: By randomly undersampling k-space and using CS reconstruction, high-quality (3) He and (1) H 3D image sets with isotropic 3.9-mm resolution can be acquired within an 8-s breath-hold., (© 2014 Wiley Periodicals, Inc.)

IgG4-associated cholangitis can mimic hilar cholangiocarcinoma. Previously reported patients with IgG4-associated cholangitis mimicking cholangiocarcinoma had elevated serum IgG4 levels and long-segment biliary strictures. However, in the absence of other diagnostic criteria for malignancy, IgG4-associated cholangitis should remain a consideration among patients with normal serum IgG4 and a hilar mass suspicious for cholangiocarcinoma. The presence of a hilar mass and a malignant-appearing biliary stricture in two patients with normal serum IgG4 prompted further evaluation and subsequent concomitant liver and bile duct resection and reconstruction. The diagnosis of IgG4-associated cholangitis was established during the pathologic evaluation of the resected specimens. IgG4-associated cholangitis is a known imitator of hilar cholangiocarcinoma and should be considered in the differential diagnosis even among serologically IgG4-negative patients with a hilar mass prior to operative resection.

Hyperpolarized (HP) gases are a new class of contrast agents that permit to obtain high temporal and spatial resolution magnetic resonance images (MRI) of the lung airspaces. HP gas MRI has become important research tool not only for morphological and functional evaluation of normal pulmonary physiology but also for regional quantification of pathologic changes occurring in several lung diseases. The purpose of this work is to provide an introduction to MRI using HP noble gases, describing both the basic principles of the technique and the new information about lung disease provided by clinical studies with this method. The applications of the technique in normal subjects, smoking related lung disease, asthma, and cystic fibrosis are reviewed., (Copyright © 2014 SERAM. Published by Elsevier España, S.L.U. All rights reserved.)

S-Nitrosoglutathione is an endogenous airway smooth muscle relaxant. Increased airway S-nitrosoglutathione breakdown occurs in some asthma patients. We asked whether patients with increased airway catabolism of this molecule had clinical features that distinguished them from other asthma patients. We measured S-nitrosoglutathione reductase expression and activity in bronchoscopy samples taken from 66 subjects in the Severe Asthma Research Program. We also analysed phenotype and genotype data taken from the program as a whole. Airway S-nitrosoglutathione reductase activity was increased in asthma patients (p=0.032). However, only a subpopulation was affected and this subpopulation was not defined by a "severe asthma" diagnosis. Subjects with increased activity were younger, had higher IgE and an earlier onset of symptoms. Consistent with a link between S-nitrosoglutathione biochemistry and atopy: 1) interleukin 13 increased S-nitrosoglutathione reductase expression and 2) subjects with an S-nitrosoglutathione reductase single nucleotide polymorphism previously associated with asthma had higher IgE than those without this single nucleotide polymorphism. Expression was higher in airway epithelium than in smooth muscle and was increased in regions of the asthmatic lung with decreased airflow. An early-onset, allergic phenotype characterises the asthma population with increased S-nitrosoglutathione reductase activity., (Copyright ©ERS 2015.)

Background & Aims: This study's aim was to assess the histological and metabolic effects of n-3 polyunsaturated fatty acids (PUFAs) vs. placebo while adjusting for the impact of age and weight change in NASH patients. (ClinicalTrials.gov: NCT00681408)., Methods: Forty-one subjects with non-cirrhotic NASH were enrolled, and 34 completed the study. 17 received n-3 fish oil 3000 mg/day and 17 received placebo daily for 1 year with typical counselling on caloric intake and physical activity for all subjects., Results: N-3- and placebo-treated groups showed no significant difference for the primary end point of NASH activity score (NAS) reduction ⩾ 2 points without fibrosis progression after adjustment for known covariates (n-3, 4/17 (23.5%); placebo, 3/17, (17.6%), p = 0.99). Among subjects with increased or stable weight, n-3 subjects showed a larger decrease in liver fat content by MRI than placebo-treated subjects (p = 0.014 for 2nd quartile, p = 0.003 for 3rd quartile of weight change). N-3 treatment showed significant fat reduction on the paired analysis of image-assisted fat morphometry regardless of weight loss or gain. Exercise capacity remained markedly reduced in all subjects. No independent effects on markers of hepatocyte injury or insulin sensitivity indices were observed., Conclusion: N-3 PUFAs at 3000 mg/day for one year did not lead to an improvement in the primary outcome of histological activity in NASH patients (⩾ 2 point NAS reduction). N-3 led to reduced liver fat by multiple measures. Other metabolic effects were not seen, although no detrimental effects were apparent. Whether longer duration, higher dose, or different composition of n-3 therapy would lead to additional benefits is uncertain., (Copyright © 2014 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.)

Purpose: Determine the incidence and amount of isolated pelvic fluid in males, stratified by age, on outpatient pelvic magnetic resonance imaging (MRI) examinations performed for lower back or extremity pain., Methods: After institutional review board approval, 161 pelvic MRIs performed on males for musculoskeletal or neurologic indications over an 18-month period were retrospectively reviewed for isolated pelvic fluid by 2 radiologists. Patients with a potential etiology for the fluid were excluded. Volume and maximal 2-dimensional measurements of fluid were calculated. Statistical analysis included logistic regression, Wilcoxon rank-sum, and χ tests., Results: Twenty (44.4%) of 45 patients 5 to 29 years old, 5 (10%) of 50 patients 30 to 49 years old, and 4 (6.1%) of 66 patients older than 50 years had isolated pelvic fluid (P < 0.001). Mean volume of fluid was 2.5 mL; 97% (28/29) had less than 10 mL. Mean maximal 2-dimensional measurement was 2.1 cm; 93% (27/29) had less than 6 cm(2)., Conclusions: Isolated fluid is greater than 7 times more common on outpatient pelvic MRIs in males younger than 30 years compared with men older than 49 years. Fluid rarely exceeded 10 mL or 6 cm(2).

Purpose: To determine whether helium-3 diffusion MR can detect the changes in the lungs of healthy nonsmoking individuals who were regularly exposed to secondhand smoke., Materials and Methods: Three groups were studied (age: 59 ± 9 years): 23 smokers, 37 exposure-to-secondhand-smoke subjects, and 29 control subjects. We measured helium-3 diffusion values at diffusion times from 0.23 to 1.97 s., Results: One-way analysis of variance revealed that the mean area under the helium-3 diffusion curves (ADC AUC) of the smokers was significantly elevated compared with the controls and to the exposure-to-secondhand-smoke subjects (P < 0.001 both). No difference between the mean ADC AUC of the exposure-to-secondhand-smoke subjects and that of the controls was found (P = 0.115). However, application of a receiver operator characteristic-derived rule to classify subjects as either a "control" or a "smoker," based on ADC AUC, revealed that 30% (11/37) of the exposure-to-secondhand subjects were classified as "smokers" indicating an elevation of the ADC AUC., Conclusion: Using helium-3 diffusion MR, elevated ADC values were detected in 30% of nonsmoking healthy subjects who had been regularly exposed to secondhand smoke, supporting the concept that, in susceptible individuals, secondhand smoke causes mild lung damage., (Copyright © 2013 Wiley Periodicals, Inc.)

Purpose: To develop an automated segmentation method to differentiate the ventilated lung volume on (3) He magnetic resonance imaging (MRI)., Materials and Methods: Computational processing (CP) for each subject consisted of the following three essential steps: 1) inhomogeneity bias correction, 2) whole lung segmentation, and 3) subdivision of the lung segmentation into regions of similar ventilation. Evaluation consisted of two comparative analyses: i) comparison of the number of defects scored by two human readers in 43 subjects, and ii) simultaneous truth and performance level estimation (STAPLE) in 18 subjects in which the ventilation defects were manually segmented by four human readers., Results: There was excellent correlation between the number of ventilation defects tabulated by CP and reader #1 (intraclass correlation coefficient [ICC] = 0.86), CP and reader #2 (ICC = 0.85), and between the two readers (ICC = 0.97). The STAPLE results from the second analysis yielded the following sensitivity/specificity numbers: CP (0.898/0.905), radiologist #1 (0.743/0.897), radiologist #2 (0.501/0.985), radiologist #3 (0.898/0.848), and the first author (0.600/0.984)., Conclusion: We developed and evaluated an automated method for quantifying the ventilated lung volume on (3) He MRI. The findings strongly indicate that our proposed algorithmic processing may be a reliable, automatic method for quantitating ventilation defects., (Copyright © 2011 Wiley-Liss, Inc.)

Background: High-quality preoperative cross-sectional imaging is vital to accurately stage patients with pancreatic ductal adenocarcinoma (PDAC). We hypothesized that imaging performed at a high-volume pancreatic cancer center with pancreatic imaging protocols more accurately stages patients compared with pre-referral imaging., Methods: We retrospectively reviewed data from all patients with PDAC who presented to the surgical oncology clinic at our institution between June 2005 and August 2009. Detailed preoperative imaging, staging, and operative data were collected for each patient., Results: A total of 230 patients with PDAC were identified, of which 169 had pre-referral imaging. Patients were selectively reimaged at our institution based on the quality and timing of imaging at the outside facility: 108 (47%) patients were deemed resectable, 54 (23.5%) were deemed borderline-resectable, and 68 (29.5%) were deemed unresectable. Of the resectable patients, 99 opted for resection. Eighty-two of those 99 patients underwent preoperative imaging at our institution, and of these 27% had unresectable disease at the time of surgery compared with 47% of patients who only had pre-referral imaging (p = 0.14). Reimaging altered staging and changed management in 56% of patients. Among that group were 55 patients, categorized as resectable on pre-referral imaging, who on repeat imaging were deemed to be borderline resectable (n = 27) or unresectable (n = 28)., Conclusions: Pancreas-protocol imaging at a high-volume center improves preoperative staging and alters management in a significant proportion of patients with PDAC who undergo pre-referral imaging. Thus, repeat imaging with pancreas protocols and dedicated radiologists is justified at high-volume centers.

Objective: Preoperative staging of pancreatic cancer is crucial for proper therapy. Through this study, we aimed to compare the ability of endoscopic ultrasound (EUS) and magnetic resonance imaging (MRI) to effectively detect and stage pancreatic cancer., Methods: One hundred twenty-seven patients undergoing EUS-fine-needle aspiration and MRI for the workup of pancreatic cancer were captured in a prospective database for comparison. The final surgical stage was recorded in patients who went to surgery., Results: Of 127 patients, 48 were surgically explored, and of these, 22 (46%) underwent pancreaticoduodenectomy. Agreement in the patients' staging between EUS and MRI was 94 (74%) of 127. Magnetic resonance imaging was more likely to report metastatic disease or arterial involvement. The overall correlation between EUS and MRI was marginal (κ = 0.42; 95% CI, 0.26-0.58). Of the 48 surgically explored patients, 12 (25%) were understaged by MRI, 13 (27%) were understaged by EUS, and 1 (2%) were overstaged. Endoscopic US and MRI had a sensitivity of 34 (97.2%) of 35 for stage II tumors and 35 (100%) of 35 for lower-stage tumors, respectively., Conclusion: Endoscopic US and MRI had marginal correlation for staging, especially the more advanced tumors. Although EUS has the added advantage of tissue acquisition for confirmation, the tumors understaged by both the modalities were different. Therefore, both tests should be performed for accurate staging.

Background: Patients with borderline resectable pancreatic ductal adenocarcinoma (PDA) represent a high-risk group of patients due to tumor or patient-related characteristics. The optimal management of these patients has not been fully defined., Materials and Methods: All patients undergoing evaluation for PDA between 2005 and 2008 were identified. Clinical, radiographic, and pathological data were retrospectively reviewed. Patients were staged as borderline resectable using the M.D. Anderson Cancer Center (MDACC) classification., Results: A total of 170 patients with PDA were identified, 40 with borderline resectable disease. Of these, 34 borderline resectable patients (85%) completed neoadjuvant therapy and were restaged; pancreatic resection was completed in 16 patients (46%). Also, 8 patients completed 50 Gy of radiation in 28 fractions in 6 weeks, whereas 8 patients received 50 Gy in 20 fractions in 4 weeks plus chronomodulated capecitabine. An R0 resection was achieved in 12 of the 16 patients (75%). Also, 5 patients (63%) treated in 20 fractions had >90% pathologic response versus 1 (13%) treated in 28 fractions (P < .05). Borderline resectable patients completing surgery had similar survival to patients with resectable disease who underwent surgery. Patients receiving accelerated fractionation radiation had improved survival compared with patients treated with standard fractionation protocol., Conclusions: A neoadjuvant approach to borderline resectable PDA identifies patients who are most likely to benefit from pancreatic resection. Preoperative capecitabine-based chemoradiation is an effective, well-tolerated treatment for these patients. Neoadjuvant therapy for borderline resectable PDA warrants further investigation using treatment schedules that can safely intensify irradiation dose.

Asthma is a chronic inflammatory disease that affects both the large and small airways and results in bronchoconstriction, mucous hypersecretion, smooth muscle hypertrophy, and subepithelial fibrosis. To gain insight into the pathophysiology of asthma, chest computed tomography (CT) has been investigated as a noninvasive method to evaluate airway wall thickness of medium and large airways. Hyperpolarized gas MRI can assess the functional alterations of airflow within the lung resulting from the structural changes in the airways. In this article, we review the application of CT-based techniques and hyperpolarized gas MRI to study structural and functional changes in asthma. From the result of studies with CT and hyperpolarized gas MRI, it is becoming apparent that asthma has a regional distribution within the lung, that is, some areas of the lung are more affected than others. Furthermore, there appears to be some persistence to this distribution which may explain the observed patterns of airway remodeling and provide targets for localized therapies such as local application of anti-inflammatory agents or bronchial thermoplasty. Thus, cross sectional imaging in asthma is providing new insights into the pathophysiology of the disease and has the potential to become essential in the guidance of localized treatments., (Copyright © 2010 Wiley-Liss, Inc.)

A computational framework is described that was developed for quantitative analysis of hyperpolarized helium-3 MR lung ventilation image data. This computational framework was applied to a study consisting of 55 subjects (47 asthmatic and eight normal). Each subject was imaged before and after respiratory challenge and also underwent spirometry. Approximately 1600 image features were calculated from the lungs in each image. Both the image and 27 spirometric features were ranked based on their ability to characterize clinical diagnosis using a mutual information-based feature subset selection algorithm. It was found that the top image features perform much better compared with the current clinical gold-standard spirometric values when considered individually. Interestingly, it was also found that spirometric values are relatively orthogonal to these image feature values in terms of informational content., ((c) 2010 Wiley-Liss, Inc.)

Purpose: To propose and test the feasibility of a novel method for quantifying 3D regional pulmonary kinematics from hyperpolarized helium-3 tagged MRI in human subjects using a tailored image processing pipeline and a recently developed nonrigid registration framework., Materials and Methods: Following image acquisition, inspiratory and expiratory tagged (3)He magnetic resonance (MR) images were preprocessed using various image filtering techniques to enhance the tag surfaces. Segmentation of the three orthogonal sets of tag planes in each lung produced distinct point-set representations of the tag surfaces. Using these labeled point-sets, deformation fields and corresponding strain maps were obtained via nonrigid point-set registration. Kinematic analysis was performed on three volunteers., Results: Tag lines in inspiratory and expiratory images were coregistered producing a continuous 3D correspondence mapping. Average displacement and directional strains were calculated in three subjects in the inferior, mid, and superior portions of the right and left lungs. As expected, the predominant direction of displacements with expiration is from inferior to superior., Conclusion: Kinematic quantitation of pulmonary motion using tagged (3)He MRI is feasible using the applied image preprocessing filtering techniques and nonrigid point-set registration. Potential benefits from regional pulmonary kinematic quantitation include the facilitation of diagnosis and local assessment of disease progression., (Copyright 2010 Wiley-Liss, Inc.)

A pulse-sequence strategy was developed for generating regional maps of alveolar oxygen partial pressure (pO2) in a single 6-sec breath hold, for use in human subjects with impaired lung function. Like previously described methods, pO2 values are obtained by measuring the oxygen-induced T1 relaxation of inhaled hyperpolarized 3He. Unlike other methods, only two 3He images are acquired: one with reverse-centric and the other with centric phase-encoding order. This phase-encoding arrangement minimizes the effects of regional flip-angle variations, so that an accurate map of instantaneous pO2 can be calculated from two images acquired a few seconds apart. By combining this phase-encoding strategy with variable flip angles, the vast majority of the hyperpolarized magnetization goes directly into the T1 measurement, minimizing noise in the resulting pO2 map. The short-breath-hold pulse sequence was tested in phantoms containing known O2 concentrations. The mean difference between measured and prepared pO2 values was 1 mm Hg. The method was also tested in four healthy volunteers and three lung-transplant patients. Maps of healthy subjects were largely uniform, whereas focal regions of abnormal pO2 were observed in diseased subjects. Mean pO2 values varied with inhaled O2 concentration. Mean pO2 was consistent with normal steady-state values in subjects who inhaled 3He diluted only with room air., (Copyright (c) 2009 Wiley-Liss, Inc.)

Imaging techniques of the lung continue to advance, with improving ability to image the more distal airways. Two imaging techniques are reviewed: computed tomography and magnetic resonance with hyperpolarized helium-3.

Purpose: To develop a dynamic magnetic resonance imaging (MRI) tagging technique using hyperpolarized helium-3 (HP He-3) to track lung motion., Methods and Materials: An accelerated non-Cartesian k-space trajectory was used to gain acquisition speed, at the cost of introducing image artifacts, providing a viable strategy for obtaining whole-lung coverage with adequate temporal resolution. Multiple-slice two-dimensional dynamic images of the lung were obtained in three healthy subjects after inhaling He-3 gas polarized to 35%-40%. Displacement, strain, and ventilation maps were computed from the observed motion of the grid peaks., Results: Both temporal and spatial variations of pulmonary mechanics were observed in normal subjects, including shear motion between different lobes of the same lung., Conclusion: These initial results suggest that dynamic imaging of grid-tagged hyperpolarized magnetization may potentially be a powerful tool for observing and quantifying pulmonary biomechanics on a regional basis and for assessing, validating, and improving lung deformable image registration algorithms.

Purpose: To determine changes in regional airflow obstruction over time in the lungs of patients with asthma, as demonstrated with hyperpolarized helium 3 ((3)He) magnetic resonance (MR) imaging, and to assess correlations with disease severity and use of asthma medications., Materials and Methods: Institutional review board approval and written informed consent were obtained for this HIPAA-compliant study. Use of (3)He was approved by the U.S. Food and Drug Administration. Forty-three patients underwent 103 MR imaging studies in total; 26 were imaged twice within 42-82 minutes (same day), and 17 were imaged on 3 days between 1 and 476 days (multiday). Each day, spirometry was performed, disease severity was determined, and the use of asthma medications was recorded. Images were reviewed in a pairwise fashion to determine total ventilation defect number, defects in same location between imaging studies, and size. Parametric and nonparametric statistical methods were used., Results: For the same-day examinations, the mean number of defects per image section was similar at baseline and repeat imaging (1.8 +/- 1.9 [standard deviation] vs 1.6 +/- 1.9, respectively; P = .15), with 75% of defects remaining in the same location and 71% of these not changing size. For the multiday examinations, the mean number of defects per section was higher for study 2 (2.4 +/- 1.5) than study 1 (1.7 +/- 0.9, P = .02), was lower for study 3 (1.5 +/- 1.1) than for study 2 (P < .01), and was similar for studies 1 and 3 (P = .56). Time between examinations was not associated with change in mean number of defects per section (median intrasubject correlation [r(m)] = 0.01, P = .64) or change in spirometric values (range of r(m) values: -0.56 to -0.31; range of P values: .09-.71). Defects in the same location decreased with time (r(m) = -0.83, P < .01), with 67% persisting between studies 1 and 2 (median interval, 31 days), 43% persisting between studies 2 and 3 (median interval, 41 days), and 38% persisting between studies 1 and 3 (median interval, 85 days); 46%-58% of defects remained unchanged in size. These trends were the same regardless of disease severity or medication use., Conclusion: In asthma, focal airflow impediment within the lungs can be markedly persistent over time, regardless of disease severity or treatment.

Background and Purpose: Unresectable cholangiocarcinoma is an intractable disease marked by recurrent bouts of biliary obstruction and infection. Traditional treatment methods provide only symptomatic relief and no proven survival advantage. We assessed the tolerability of helical tomotherapy intensity modulated radiotherapy (IMRT) with concurrent capecitabine and photodynamic therapy (PDT) in patients with unresectable hilar cholangiocarcinoma., Methods: Ten patients with unresectable hilar cholangiocarcinoma were treated with helical tomotherapy IMRT. An accelerated dose of 50 Gy in 20 fractions (2.5 Gy/fraction) was used. Planning target volume (PTV) consisted of a 1.5 cm radial expansion and a 2 cm craniocaudal expansion of the magnetic resonance imaging and/or contrast enhanced computed tomography-defined gross target volume. PTV ranged from 123 cc to 693 cc (mean 349 cc). Concurrent chronomodulated capecitabine was administered on days of irradiation. Six patients received PDT., Results: All patients developed side effects, including grade 2 nausea, and 9 of 10 experienced mild fatigue. Patients lost 3% of their body weight on average. Three patients required brief hospital admission and stent revision for cholangitis during chemoradiotherapy. Capecitabine was discontinued in one patient and decreased in dose for another due to increasing liver enzymes. Median overall survival was 13 months, and median disease-free survival was 10 to 11 months. One patient underwent successful cadaveric liver transplant after chemoradiotherapy and remains disease free 2 years later., Conclusions: Concurrent chemoradiotherapy with helical tomotherapy IMRT and capecitabine in conjunction with PDT is well tolerated in patients with hilar cholangiocarcinoma.

Rationale and Objectives: Diffusion magnetic resonance imaging (MRI) with hyperpolarized (3)He gas is a powerful technique for probing the characteristics of the lung microstructure. A key parameter for this technique is the diffusion time, which is the period during which the atoms are allowed to diffuse within the lung for measurement of the signal attenuation. The relationship between diffusion time and the length scales that can be explored is discussed, and representative, preliminary results are presented from ongoing studies of the human lung for diffusion times ranging from milliseconds to several seconds., Materials and Methods: (3)He diffusion MRI of the human lung was performed on a 1.5T Siemens Sonata scanner. Using gradient echo-based and stimulated echo-based techniques for short and medium-to-long diffusion times, respectively, measurements were performed for times ranging from 2 milliseconds to 6.5 seconds in two healthy subjects, a subject with subclinical chronic obstructive pulmonary disease and a subject with bronchopulmonary dysplasia., Results: In healthy subjects, the apparent diffusion coefficient decreased by about 10-fold, from approximately 0.2 to 0.02 cm(2)/second, as the diffusion time increased from approximately 1 millisecond to 1 second. Results in subjects with disease suggest that measurements made at diffusion times substantially longer than 1 millisecond may provide improved sensitivity for detecting certain pathologic changes in the lung microstructure., Conclusions: With appropriately designed pulse sequences it is possible to explore the diffusion of hyperpolarized (3)He in the human lung over more than a 1,000-fold variation of the diffusion time. Such measurements provide a new opportunity for exploring and characterizing the microstructure of the healthy and diseased lung.

A stimulated-echo-based technique was developed to measure the regional apparent diffusion coefficient (ADC) of hyperpolarized 3He during a single breathhold for diffusion times of 25 ms or greater. Compared to previous methods, a substantially shorter minimum diffusion time was achieved by decoupling diffusion sensitization from image acquisition. A hyperpolarized-gas phantom was used to validate the method, which was then tested in four healthy subjects in whom regional ADC maps were acquired with diffusion times of 50, 200, and 1500 ms and a tag wavelength of 5 or 10 mm. ADC values from healthy subjects were in good agreement with reported literature values and decreased with increasing diffusion time. Mean ADC values were approximately 0.07, 0.03, and 0.015 cm2/s for diffusion times of 50, 200, and 1500 ms, respectively. ADC maps were generally homogeneous, with similar mean values when measured with the same parameters in different subjects., ((c) 2008 Wiley-Liss, Inc.)

A new technique is demonstrated in six healthy human subjects that combines grid-tagging and hyperpolarized helium-3 MRI to assess regional lung biomechanical function and quantitative ventilation. 2D grid-tagging, achieved by applying sinc-modulated RF-pulse trains along the frequency- and phase-encoding directions, was followed by a multislice fast low-angle shot (FLASH)-based acquisition at inspiration and expiration. The displacement vectors, first and second principal strains, and quantitative ventilation were computed, and mean values were calculated for the upper, middle, and lower lung regions. Displacements in the lower region were significantly greater than those in either the middle or upper region (P < 0.005), while there were no significant differences between the three regions for the two principal strains and quantitative ventilation (P = 0.11-0.92). Variations in principal strains and ventilation were greater between subjects than between lung zones within individual subjects. This technique has the potential to provide insight into regional biomechanical alterations of lung function in a variety of lung diseases.

Purpose: To measure lung motion between end-inhalation and end-exhalation using a hyperpolarized helium-3 (HP (3)He) magnetic resonance (MR) tagging technique., Methods and Materials: Three healthy volunteers underwent MR tagging studies after inhalation of 1 L HP (3)He gas diluted with nitrogen. Multiple-slice two-dimensional and volumetric three-dimensional MR tagged images of the lungs were obtained at end-inhalation and end-exhalation, and displacement vector maps were computed., Results: The grids of tag lines in the HP (3)He MR images were well defined at end-inhalation and remained evident at end-exhalation. Displacement vector maps clearly demonstrated the regional lung motion and deformation that occurred during exhalation. Discontinuity and differences in motion pattern between two adjacent lung lobes were readily resolved., Conclusions: Hyperpolarized helium-3 MR tagging technique can be used for direct in vivo measurement of respiratory lung motion on a regional basis. This technique may lend new insights into the regional pulmonary biomechanics and thus provide valuable information for the deformable registration of lung.