Hyperpolarized 129Xe MRI and Spectroscopy of Gas-Exchange Abnormalities in Nonspecific Interstitial Pneumonia.

Background Recent studies demonstrate that antifibrotic drugs previously reserved for idiopathic pulmonary fibrosis (IPF) may slow progression in other interstitial lung diseases (ILDs), creating an urgent need for tools that can sensitively assess disease activity, progression, and therapy response across ILDs. Hyperpolarized xenon 129 (129Xe) MRI and spectroscopy have provided noninvasive measurements of regional gas-exchange abnormalities in IPF. Purpose To assess gas exchange function using 129Xe MRI in a group of study participants with nonspecific interstitial pneumonia (NSIP) compared with healthy control participants. Materials and Methods In this prospective study, participants with NSIP and healthy control participants were enrolled between November 2017 and February 2020 and underwent 129Xe MRI and spectroscopy. Quantitative imaging provided three-dimensional maps of ventilation, interstitial barrier uptake, and transfer into the red blood cell (RBC) compartment. Spectroscopy provided parameters of the static RBC and barrier uptake compartments, as well as cardiogenic oscillations in RBC signal amplitude and chemical shift. Differences between NSIP and healthy control participants were assessed using the Wilcoxon rank-sum test. Results Thirty-six participants with NSIP (mean age, 57 years ± 11 [standard deviation]; 27 women) and 15 healthy control participants (mean age, 39 years ± 18; two women) were evaluated. Participants with NSIP had no difference in ventilation compared with healthy control participants (median, 4.4% [first quartile, 1.5%; third quartile, 8.7%] vs 6.0% [first quartile, 2.8%; third quartile, 6.9%]; P = .91), but they had a higher barrier uptake (median, 6.2% [first quartile, 1.8%; third quartile, 23.9%] vs 0.53% [first quartile, 0.33%; third quartile, 2.9%]; P = .003) and an increased RBC transfer defect (median, 20.6% [first quartile, 11.6%; third quartile, 27.8%] vs 2.8% [first quartile, 2.3%; third quartile, 4.9%]; P < .001). NSIP participants also had a reduced ratio of RBC-to-barrier peaks (median, 0.24 [first quartile, 0.19; third quartile, 0.31] vs 0.57 [first quartile, 0.52; third quartile, 0.67]; P < .001) and a reduced RBC chemical shift (median, 217.5 ppm [first quartile, 217.0 ppm; third quartile, 218.0 ppm] vs 218.2 ppm [first quartile, 217.9 ppm; third quartile, 218.6 ppm]; P = .001). Conclusion Participants with nonspecific interstitial pneumonia had increased barrier uptake and decreased red blood cell (RBC) transfer compared with healthy controls measured using xenon 129 gas-exchange MRI and reduced RBC-to-barrier ratio and RBC chemical shift measured using spectroscopy. © RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Wild in this issue.

A protocol for quantifying cardiogenic oscillations in dynamic 129 Xe gas exchange spectroscopy: The effects of idiopathic pulmonary fibrosis.

The spectral parameters of hyperpolarized 129 Xe exchanging between airspaces, interstitial barrier, and red blood cells (RBCs) are sensitive to pulmonary pathophysiology. This study sought to evaluate whether the dynamics of 129 Xe spectroscopy provide additional insight, with particular focus on quantifying cardiogenic oscillations in the RBC resonance. 129 Xe spectra were dynamically acquired in eight healthy volunteers and nine subjects with idiopathic pulmonary fibrosis (IPF). 129 Xe FIDs were collected every 20 ms (TE  = 0.932 ms, 512 points, dwell time = 32 µs, flip angle ≈ 20°) during a 16 s breathing maneuver. The FIDs were pre-processed using the spectral improvement by Fourier thresholding technique (SIFT) and fit in the time domain to determine the airspace, interstitial barrier, and RBC spectral parameters. The RBC and gas resonances were fit to a Lorentzian lineshape, while the barrier was fit to a Voigt lineshape to account for its greater structural heterogeneity. For each complex resonance the amplitude, chemical shift, linewidth(s), and phase were calculated. The time-averaged spectra confirmed that the RBC to barrier amplitude ratio (RBC:barrier ratio) and RBC chemical shift are both reduced in IPF subjects. Their temporal dynamics showed that all three 129 Xe resonances are affected by the breathing maneuver. Most notably, several RBC spectral parameters exhibited prominent oscillations at the cardiac frequency, and their peak-to-peak variation differed between IPF subjects and healthy volunteers. In the IPF cohort, oscillations were more prominent in the RBC amplitude (16.8 ± 5.2 versus 9.7 ± 2.9%; P = 0.008), chemical shift (0.43 ± 0.33 versus 0.083 ± 0.05 ppm; P < 0.001), and phase (7.7 ± 5.6 versus 1.4 ± 0.8°; P < 0.001). Dynamic 129 Xe spectroscopy is a simple and sensitive tool that probes the temporal variability of gas exchange and may prove useful in discerning the underlying causes of its impairment.

Multireader Determination of Clinically Significant Obstruction Using Hyperpolarized 129Xe-Ventilation MRI.

OBJECTIVE: The objective of our study was to identify the magnitude and distribution of ventilation defect scores (VDSs) derived from hyperpolarized (HP) 129Xe-MRI associated with clinically relevant airway obstruction. MATERIALS AND METHODS: From 2012 to 2015, 76 subjects underwent HP 129Xe-MRI (48 healthy volunteers [mean age ± SD, 54 ± 17 years]; 20 patients with asthma [mean age, 44 ± 20 years]; eight patients with chronic obstructive pulmonary disease [mean age, 67 ± 5 years]). All subjects underwent spirometry 1 day before MRI to establish the presence of airway obstruction (forced expiratory volume in 1 second-to-forced vital capacity ratio [FEV1/FVC] < 70%). Five blinded readers assessed the degree of ventilation impairment and assigned a VDS (range, 0-100%). Interreader agreement was assessed using the Fleiss kappa statistic. Using FEV1/FVC as the reference standard, the optimum VDS threshold for the detection of airway obstruction was estimated using ROC curve analysis with 10-fold cross-validation. RESULTS: Compared with the VDSs in healthy subjects, VDSs in patients with airway obstruction were significantly higher (p < 0.0001) and significantly correlated with disease severity (r = 0.66, p < 0.0001). Ventilation defects in subjects with airway obstruction did not show a location-specific pattern (p = 0.158); however, defects in healthy control subjects were more prevalent in the upper lungs (p = 0.014). ROC curve analysis yielded an optimal threshold of 12.4% ± 6.1% (mean ± SD) for clinically significant VDS. Interreader agreement for 129Xe-MRI was substantial (κ = 0.71). CONCLUSION: This multireader study of a diverse cohort of patients and control subjects suggests a 129Xe-ventilation MRI VDS of 12.4% or greater represents clinically significant obstruction.

Multi-Institutional Evaluation of Digital Tomosynthesis, Dual-Energy Radiography, and Conventional Chest Radiography for the Detection and Management of Pulmonary Nodules.

Purpose To conduct a multi-institutional, multireader study to compare the performance of digital tomosynthesis, dual-energy (DE) imaging, and conventional chest radiography for pulmonary nodule detection and management. Materials and Methods In this binational, institutional review board-approved, HIPAA-compliant prospective study, 158 subjects (43 subjects with normal findings) were enrolled at four institutions. Informed consent was obtained prior to enrollment. Subjects underwent chest computed tomography (CT) and imaging with conventional chest radiography (posteroanterior and lateral), DE imaging, and tomosynthesis with a flat-panel imaging device. Three experienced thoracic radiologists identified true locations of nodules (n = 516, 3-20-mm diameters) with CT and recommended case management by using Fleischner Society guidelines. Five other radiologists marked nodules and indicated case management by using images from conventional chest radiography, conventional chest radiography plus DE imaging, tomosynthesis, and tomosynthesis plus DE imaging. Sensitivity, specificity, and overall accuracy were measured by using the free-response receiver operating characteristic method and the receiver operating characteristic method for nodule detection and case management, respectively. Results were further analyzed according to nodule diameter categories (3-4 mm, >4 mm to 6 mm, >6 mm to 8 mm, and >8 mm to 20 mm). Results Maximum lesion localization fraction was higher for tomosynthesis than for conventional chest radiography in all nodule size categories (3.55-fold for all nodules, P < .001; 95% confidence interval [CI]: 2.96, 4.15). Case-level sensitivity was higher with tomosynthesis than with conventional chest radiography for all nodules (1.49-fold, P < .001; 95% CI: 1.25, 1.73). Case management decisions showed better overall accuracy with tomosynthesis than with conventional chest radiography, as given by the area under the receiver operating characteristic curve (1.23-fold, P < .001; 95% CI: 1.15, 1.32). There were no differences in any specificity measures. DE imaging did not significantly affect nodule detection when paired with either conventional chest radiography or tomosynthesis. Conclusion Tomosynthesis outperformed conventional chest radiography for lung nodule detection and determination of case management; DE imaging did not show significant differences over conventional chest radiography or tomosynthesis alone. These findings indicate performance likely achievable with a range of reader expertise. © RSNA, 2016 Online supplemental material is available for this article.

Uncovering a third dissolved-phase 129 Xe resonance in the human lung: Quantifying spectroscopic features in healthy subjects and patients with idiopathic pulmonary fibrosis.

PURPOSE: The purpose of this work was to accurately characterize the spectral properties of hyperpolarized 129 Xe in patients with idiopathic pulmonary fibrosis (IPF) compared to healthy volunteers. METHODS: Subjects underwent hyperpolarized 129 Xe breath-hold spectroscopy, during which 38 dissolved-phase free induction decays (FIDs) were acquired after reaching steady state (echo time/repetition time = 0.875/50 ms; bandwidth = 8.06 kHz; flip angle≈22 °). FIDs were averaged and then decomposed into multiple spectral components using time-domain curve fitting. The resulting amplitudes, frequencies, line widths, and starting phases of each component were compared among groups using a Mann-Whitney-Wilcoxon U test. RESULTS: Three dissolved-phase resonances, consisting of red blood cells (RBCs) and two barrier compartments, were consistently identified in all subjects. In subjects with IPF relative to healthy volunteers, the RBC frequency was 0.70 parts per million (ppm) more negative (P = 0.05), the chemical shift of barrier 2 was 0.6 ppm more negative (P = 0.009), the line widths of both barrier peaks were ∼2 ppm narrower (P < 0.001), and the starting phase of barrier 1 was 20.3 ° higher (P = 0.01). Moreover, the ratio RBC:barriers was reduced by 52.9% in IPF (P < 0.001). CONCLUSIONS: The accurate decomposition of 129 Xe spectra not only has merit for developing a global metric of pulmonary function, but also provides necessary insights to optimize phase-sensitive methods for imaging 129 Xe gas transfer. Magn Reson Med 78:1306-1315, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Single-breath clinical imaging of hyperpolarized (129)Xe in the airspaces, barrier, and red blood cells using an interleaved 3D radial 1-point Dixon acquisition.

PURPOSE: We sought to develop and test a clinically feasible 1-point Dixon, three-dimensional (3D) radial acquisition strategy to create isotropic 3D MR images of (129)Xe in the airspaces, barrier, and red blood cells (RBCs) in a single breath. The approach was evaluated in healthy volunteers and subjects with idiopathic pulmonary fibrosis (IPF). METHODS: A calibration scan determined the echo time at which (129)Xe in RBCs and barrier were 90° out of phase. At this TE, interleaved dissolved and gas-phase images were acquired using a 3D radial acquisition and were reconstructed separately using the NUFFT algorithm. The dissolved-phase image was phase-shifted to cast RBC and barrier signal into the real and imaginary channels such that the image-derived RBC:barrier ratio matched that from spectroscopy. The RBC and barrier images were further corrected for regional field inhomogeneity using a phase map created from the gas-phase (129)Xe image. RESULTS: Healthy volunteers exhibited largely uniform (129)Xe-barrier and (129)Xe-RBC images. By contrast, (129)Xe-RBC images in IPF subjects exhibited significant signal voids. These voids correlated qualitatively with regions of fibrosis visible on CT. CONCLUSIONS: This study illustrates the feasibility of acquiring single-breath, 3D isotropic images of (129)Xe in the airspaces, barrier, and RBCs using a 1-point Dixon 3D radial acquisition.

Persistent pulmonary subsolid nodules with solid portions of 5 mm or smaller: Their natural course and predictors of interval growth.

OBJECTIVE: To investigate the natural course of persistent pulmonary subsolid nodules (SSNs) with solid portions ≤5 mm and the clinico-radiological features that influence interval growth over follow-ups. METHODS: From 2005 to 2013, the natural courses of 213 persistent SSNs in 213 patients were evaluated. To identify significant predictors of interval growth, Kaplan-Meier analysis and Cox proportional hazard regression analysis were performed. RESULTS: Among the 213 nodules, 136 were pure ground-glass nodules (GGNs; growth, 18; stable, 118) and 77 were part-solid GGNs with solid portions ≤5 mm (growth, 24; stable, 53). For all SSNs, lung cancer history (p = 0.001), part-solid GGNs (p < 0.001), and nodule diameter (p < 0.001) were significant predictors for interval growth. On subgroup analysis, nodule diameter was an independent predictor for the interval growth of both pure GGNs (p < 0.001), and part-solid GGNs (p = 0.037). For part-solid GGNs, lung cancer history (p = 0.002) was another significant predictor of the interval growth. Interval growth of pure GGNs ≥10 mm and part-solid GGNs ≥8 mm were significantly more frequent than in pure GGNs <10 mm (p < 0.001) and part-solid GGNs <8 mm (p = 0.003), respectively. CONCLUSION: The natural course of SSNs with solid portions ≤5 mm differed significantly according to their nodule type and nodule diameters, with which their management can be subdivided. KEY POINTS: • Pure GGNs ≥10 mm have significantly more frequent interval growth than those <10 mm. • Part-solid GGNs ≥8 mm have significantly more frequent interval growth than those <8 mm. • Management of SSNs with solid portions ≤5 mm can be subdivided by diameter.

Radiographic Imaging of Community-Acquired Pneumonia: A Case-Based Review.

The chest radiograph is the most common imaging examination performed in most radiology departments, and one of the more common indications for these studies is suspected infection. Radiologists must therefore be aware of less common radiographic patterns of pulmonary infection if they are to add value in the interpretation of chest radiographs for this indication. This review uses a case-based format to illustrate a range of imaging findings that can be associated with acute pulmonary infection and highlight findings that should prompt investigation for diseases other than community-acquired pneumonia to prevent misdiagnosis and delays in appropriate management.

Quantitative analysis of hyperpolarized 129Xe ventilation imaging in healthy volunteers and subjects with chronic obstructive pulmonary disease.

In this study, hyperpolarized (129) Xe MR ventilation and (1) H anatomical images were obtained from three subject groups: young healthy volunteers (HVs), subjects with chronic obstructive pulmonary disease (COPD) and age-matched controls (AMCs). Ventilation images were quantified by two methods: an expert reader-based ventilation defect score percentage (VDS%) and a semi-automated segmentation-based ventilation defect percentage (VDP). Reader-based values were assigned by two experienced radiologists and resolved by consensus. In the semi-automated analysis, (1) H anatomical images and (129) Xe ventilation images were both segmented following registration to obtain the thoracic cavity volume and ventilated volume, respectively, which were then expressed as a ratio to obtain the VDP. Ventilation images were also characterized by generating signal intensity histograms from voxels within the thoracic cavity volume, and heterogeneity was analyzed using the coefficient of variation (CV). The reader-based VDS% correlated strongly with the semi-automatically generated VDP (r = 0.97, p < 0.0001) and with CV (r = 0.82, p < 0.0001). Both (129) Xe ventilation defect scoring metrics readily separated the three groups from one another and correlated significantly with the forced expiratory volume in 1 s (FEV1 ) (VDS%: r = -0.78, p = 0.0002; VDP: r = -0.79, p = 0.0003; CV: r = -0.66, p = 0.0059) and other pulmonary function tests. In the healthy subject groups (HVs and AMCs), the prevalence of ventilation defects also increased with age (VDS%: r = 0.61, p = 0.0002; VDP: r = 0.63, p = 0.0002). Moreover, ventilation histograms and their associated CVs distinguished between subjects with COPD with similar ventilation defect scores, but visibly different ventilation patterns.

Preliminary evaluation of biplane correlation (BCI) stereographic imaging for lung nodule detection.

A biplane correlation (BCI) imaging system obtains images that can be viewed in stereo, thereby minimizing overlapping structures. This study investigated whether using stereoscopic visualization provides superior lung nodule detection compared to standard postero-anterior (PA) image display. Images were acquired at two oblique views of ±3° as well as at a standard PA position from 60 patients. Images were processed using optimal parameters and displayed on a stereoscopic display. The PA image was viewed in the standard format, while the oblique views were paired to provide a stereoscopic view of the subject. A preliminary observer study was performed with four radiologists who viewed and scored the PA image then viewed and scored the BCI stereoscopic image. The BCI stereoscopic viewing of lung nodules resulted in 71 % sensitivity and 0.31 positive predictive value (PPV) index compared to PA results of 86 % sensitivity and 0.26 PPV index. The sensitivity for lung nodule detection with the BCI stereoscopic system was reduced by 15 %; however, the total number of false positives reported was reduced by 35 % resulting in an improved PPV index of 20 %. The preliminary results indicate observer dependency in terms of relative advantage of either system in the detection of lung nodules, but overall equivalency of the two methods with promising potential for BCI as an adjunct diagnostic technique.

Chronic obstructive pulmonary disease: safety and tolerability of hyperpolarized 129Xe MR imaging in healthy volunteers and patients.

PURPOSE: To evaluate the safety and tolerability of inhaling multiple 1-L volumes of undiluted hyperpolarized xenon 129 ((129)Xe) followed by up to a 16-second breath hold and magnetic resonance (MR) imaging. MATERIALS AND METHODS: This study was approved by the institutional review board and was HIPAA compliant. Written informed consent was obtained. Forty-four subjects (19 men, 25 women; mean age, 46.1 years ± 18.8 [standard deviation]) were enrolled, consisting of 24 healthy volunteers, 10 patients with chronic obstructive pulmonary disease (COPD), and 10 age-matched control subjects. All subjects received three or four 1-L volumes of undiluted hyperpolarized (129)Xe, followed by breath-hold MR imaging. Oxygen saturation, heart rate and rhythm, and blood pressure were continuously monitored. These parameters, along with respiratory rate and subjective symptoms, were assessed after each dose. Subjects' serum biochemistry and hematology were recorded at screening and at 24-hour follow-up. A 12-lead electrocardiogram (ECG) was obtained at these times and also within 2 hours prior to and 1 hour after (129)Xe MR imaging. Xenon-related symptoms were evaluated for relationship to subject group by using a χ(2) test and to subject age by using logistic regression. Changes in vital signs were tested for significance across subject group and time by using a repeated-measures multivariate analysis of variance test. RESULTS: The 44 subjects tolerated all xenon inhalations, no subjects withdrew, and no serious adverse events occurred. No significant changes in vital signs (P > .27) were observed, and no subjects exhibited changes in laboratory test or ECG results at follow-up that were deemed clinically important or required intervention. Most subjects (91%) did experience transient xenon-related symptoms, most commonly dizziness (59%), paresthesia (34%), euphoria (30%), and hypoesthesia (30%). All symptoms resolved without clinical intervention in 1.6 minutes ± 0.9. CONCLUSION: Inhalation of hyperpolarized (129)Xe is well tolerated in healthy subjects and in those with mild or moderate COPD. Subjects do experience mild, transient, xenon-related symptoms, consistent with its known anesthetic properties.

A computerized scheme for lung nodule detection in multiprojection chest radiography.

PURPOSE: Our previous study indicated that multiprojection chest radiography could significantly improve radiologists' performance for lung nodule detection in clinical practice. In this study, the authors further verify that multiprojection chest radiography can greatly improve the performance of a computer-aided diagnostic (CAD) scheme. METHODS: Our database consisted of 59 subjects, including 43 subjects with 45 nodules and 16 subjects without nodules. The 45 nodules included 7 real and 38 simulated ones. The authors developed a conventional CAD scheme and a new fusion CAD scheme to detect lung nodules. The conventional CAD scheme consisted of four steps for (1) identification of initial nodule candidates inside lungs, (2) nodule candidate segmentation based on dynamic programming, (3) extraction of 33 features from nodule candidates, and (4) false positive reduction using a piecewise linear classifier. The conventional CAD scheme processed each of the three projection images of a subject independently and discarded the correlation information between the three images. The fusion CAD scheme included the four steps in the conventional CAD scheme and two additional steps for (5) registration of all candidates in the three images of a subject, and (6) integration of correlation information between the registered candidates in the three images. The integration step retained all candidates detected at least twice in the three images of a subject and removed those detected only once in the three images as false positives. A leave-one-subject-out testing method was used for evaluation of the performance levels of the two CAD schemes. RESULTS: At the sensitivities of 70%, 65%, and 60%, our conventional CAD scheme reported 14.7, 11.3, and 8.6 false positives per image, respectively, whereas our fusion CAD scheme reported 3.9, 1.9, and 1.2 false positives per image, and 5.5, 2.8, and 1.7 false positives per patient, respectively. The low performance of the conventional CAD scheme may be attributed to the high noise level in chest radiography, and the small size and low contrast of most nodules. CONCLUSIONS: This study indicated that the fusion of correlation information in multiprojection chest radiography can markedly improve the performance of CAD scheme for lung nodule detection.

Biplane correlation imaging: a feasibility study based on phantom and human data.

The objective of this study was to implement and evaluate the performance of a biplane correlation imaging (BCI) technique aimed to reduce the effect of anatomic noise and improve the detection of lung nodules in chest radiographs. Seventy-one low-dose posterior-anterior images were acquired from an anthropomorphic chest phantom with 0.28° angular separations over a range of ±10° along the vertical axis within an 11 s interval. Similar data were acquired from 19 human subjects with institutional review board approval and informed consent. The data were incorporated into a computer-aided detection (CAD) algorithm in which suspect lesions were identified by examining the geometrical correlation of the detected signals that remained relatively constant against variable anatomic backgrounds. The data were analyzed to determine the effect of angular separation, and the overall sensitivity and false-positives for lung nodule detection. The best performance was achieved for angular separations of the projection pairs greater than 5°. Within that range, the technique provided an order of magnitude decrease in the number of false-positive reports when compared with CAD analysis of single-view images. Overall, the technique yielded ~1.1 false-positive per patient with an average sensitivity of 75%. The results indicated that the incorporation of angular information can offer a reduction in the number of false-positives without a notable reduction in sensitivity. The findings suggest that the BCI technique has the potential for clinical implementation as a cost-effective technique to improve the detection of subtle lung nodules with lowered rate of false-positives.

The effects of ambient lighting in chest radiology reading rooms.

Under typical dark chest radiography reading room conditions, a radiologist's pupils contract and dilate as their visual focus intermittently shifts between the high luminance monitor and the darker background wall, resulting in increased visual fatigue and degradation of diagnostic performance. A controlled increase of ambient lighting may minimize these visual adjustments and potentially improve comfort and accuracy. This study was designed to determine the effect of a controlled increase of ambient lighting on chest radiologist nodule detection performance. Four chest radiologists read 100 radiographs (50 normal and 50 containing a subtle nodule) under low (E=1 lx) and elevated (E=50 lx) ambient lighting levels on a DICOM-calibrated, medical-grade liquid crystal display. Radiologists were asked to identify nodule locations and rate their detection confidence. A receiver operating characteristic (ROC) analysis of radiologist results was performed and area under ROC curve (AUC) values calculated for each ambient lighting level. Additionally, radiologist selection times under both illuminance conditions were determined. Average AUC values did not significantly differ (p>0.05) between ambient lighting levels (estimated mean difference=-0.03; 95% CI, (-0.08, 0.03)). Average selection times decreased or remained constant with increased illuminance. The most considerable decreases occurred for false positive identification times (35.4±18.8 to 26.2±14.9 s) and true positive identification times (29.7±18.3 to 24.5±15.5 s). No performance differences were statistically significant. Study findings suggest that a controlled increase of ambient lighting within darkly lit chest radiology reading rooms, to a level more suitable for performance of common radiological tasks, does not appear to have a statistically significant effect on nodule detection performance.

Radiographic Imaging of Community-Acquired Pneumonia: A Case-Based Review.

The chest radiograph is the most common imaging examination performed in most radiology departments, and one of the more common indications for these studies is suspected infection. Radiologists must therefore be aware of less common radiographic patterns of pulmonary infection if they are to add value in the interpretation of chest radiographs for this indication. This review uses a case-based format to illustrate a range of imaging findings that can be associated with acute pulmonary infection and highlight findings that should prompt investigation for diseases other than community-acquired pneumonia to prevent misdiagnosis and delays in appropriate management.

Imaging of Smoking and Vaping Related Diffuse Lung Injury.

Lung injury associated with smoking tobacco or other substances results in a variety of clinical presentations and imaging patterns, depending on mechanism of injury and substance inhaled. Patients may present in the acute setting, as in the case of acute eosinophilic pneumonia, e-cigarette or vaping product use-associated lung injury, crack lung, or heroin inhalation. They may present with subacute shortness of breath and demonstrate findings of pulmonary Langerhans cell histiocytosis, respiratory bronchiolitis, or desquamative interstitial pneumonia. Alternatively, they may present with chronic dyspnea and demonstrate findings of emphysema or smoking-related interstitial lung fibrosis.

Diffusion-weighted hyperpolarized 129Xe MRI in healthy volunteers and subjects with chronic obstructive pulmonary disease.

Given its greater availability and lower cost, (129) Xe apparent diffusion coefficient (ADC) MRI offers an alternative to (3) He ADC MRI. To demonstrate the feasibility of hyperpolarized (129) Xe ADC MRI, we present results from healthy volunteers (HV), chronic obstructive pulmonary disease (COPD) subjects, and age-matched healthy controls (AMC). The mean parenchymal ADC was 0.036 ± 0.003 cm(2) sec(-1) for HV, 0.043 ± 0.006 cm(2) sec(-1) for AMC, and 0.056 ± 0.008 cm(2) sec(-1) for COPD subjects with emphysema. In healthy individuals, but not the COPD group, ADC decreased significantly in the anterior-posterior direction by ∼ 22% (P = 0.006, AMC; 0.0059, HV), likely because of gravity-induced tissue compression. The COPD group exhibited a significantly larger superior-inferior ADC reduction (∼ 28%) than the healthy groups (∼ 24%) (P = 0.00018, HV; P = 3.45 × 10(-5) , AMC), consistent with smoking-related tissue destruction in the superior lung. Superior-inferior gradients in healthy subjects may result from regional differences in xenon concentration. ADC was significantly correlated with pulmonary function tests (forced expiratory volume in 1 sec, r = -0.77, P = 0.0002; forced expiratory volume in 1 sec/forced vital capacity, r = -0.77, P = 0.0002; diffusing capacity of carbon monoxide in the lung/alveolar volume (V(A) ), r = -0.77, P = 0.0002). In healthy groups, ADC increased with age by 0.0002 cm(2) sec(-1) year(-1) (r = 0.56, P = 0.02). This study shows that (129) Xe ADC MRI is clinically feasible, sufficiently sensitive to distinguish HV from subjects with emphysema, and detects age- and posture-dependent changes.

Managing Incidental Findings on Thoracic CT: Lung Findings. A White Paper of the ACR Incidental Findings Committee.

The ACR Incidental Findings Committee presents recommendations for managing incidentally detected lung findings on thoracic CT. The Chest Subcommittee is composed of thoracic radiologists who endorsed and developed the provided guidance. These recommendations represent a combination of current published evidence and expert opinion and were finalized by informal iterative consensus. The recommendations address commonly encountered incidental findings in the lungs and are not intended to be a comprehensive review of all pulmonary incidental findings. The goal is to improve the quality of care by providing guidance on management of incidentally detected thoracic findings.

Nonsurgical extracardiac vascular shunts in the thorax: clinical and imaging characteristics.

Extracardiac nonsurgical vascular shunts in the thorax are a group of well-recognized heterogeneous conditions, frequently symptomatic, in which there is diversion of blood flow from one vessel to another or from a vessel to a cardiac chamber. The authors describe and classify many of these nonsurgical extracardiac shunts or fistulas according to their source and endpoint (eg, systemic-to-systemic, systemic-to-pulmonic, pulmonic-to-systemic, and pulmonic-to-pulmonic) and to whether the oxygenated blood mixes with deoxygenated systemic venous flow (left-to-right shunts), deoxygenated blood bypasses the pulmonary capillary bed (right-to-left shunts), or oxygenated blood recirculates (left-to-left shunts). Clinical manifestations and imaging appearances of these conditions are highlighted.