Pulsed Electric Field Ablation versus Radiofrequency Thermal Ablation in Murine Breast Cancer Models: Anticancer Immune Stimulation, Tumor Response, and Abscopal Effects.

PURPOSE: To compare the immune response and survival after size-matched radiofrequency (RF) ablation and a proprietary form of pulsed electric field (PEF) ablation in murine tumors. MATERIAL AND METHODS: Orthotopically inoculated EMT6 or 4T1 murine tumors received sham, RF ablation, or PEF ablation. 4T1 tumor ablations included subgroups with intraperitoneal checkpoint inhibition immunotherapy (αPD-1). Blood was collected for cytokine profiling and flow cytometry. Tumor size was measured and survival was monitored. Tumor samples were processed for histology, immunohistochemistry, flow cytometry, and cytokine profiling. Lungs were collected from 4T1-bearing mice for hematoxylin and eosin histology to assess metastatic spread and abscopal effect induced by ablation. RESULTS: PEF elicited distinct immunomodulatory effects, with clear differences in serum and tumor cytokine profiles compared with RF ablation, including intratumoral downregulation of vascular endothelial growth factor, hypoxia-inducible factor 1α, c-MET, interleukin-10, Ki67, and tumor necrosis factor-α (all P < .05). PEF increased innate immune activation, with enhanced recruitment of dendritic cells, M1 macrophages, and natural killer cells coupled with a reduction in M2 macrophages and myeloid-derived suppressor cells (all P < .05). Concurrently, PEF strengthened adaptive immunity compared with RF ablation, characterized by increased antigen-specific T cells and decreased regulatory T cells (all P < .05). PEF stalled tumor growth and increased survival at the end of the study (≥4× versus RFA). Finally, PEF promoted an abscopal effect of clearing metastases in the lungs, which was stronger in combination with αPD-1 than with PEF alone. CONCLUSIONS: The proprietary form of PEF used in this study evoked a preferential immunostimulatory profile versus RF ablation thermal ablation in mice, with implications for enhancing the therapeutic effectiveness of checkpoint inhibition immunotherapy for immunotherapy-unresponsive tumors.

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.

Case 274: Cardiac Echinococcus.

HistoryA 47-year-old Sudanese man without a known remarkable medical history presented to the emergency department for a syncopal episode. The patient denied chest pain, dyspnea, focal weakness, or prior similar episodes. He was originally from north Sudan and eventually moved to Saudi Arabia, where he worked as a farm manager before emigrating to the United States years ago. Physical examination findings and routine laboratory values, including complete blood count and basic metabolic panels, were normal. Electrocardiography revealed nonspecific T-wave inversions, and a series of cardiac biomarkers were negative. A contrast material-enhanced CT angiography pulmonary embolism protocol and cardiac MRI were performed for further evaluation.

Case 274.

History A 47-year-old Sudanese man without a known remarkable medical history presented to the emergency department for a syncopal episode. The patient denied chest pain, dyspnea, focal weakness, or prior similar episodes. He was originally from north Sudan and eventually moved to Saudi Arabia, where he worked as a farm manager before emigrating to the United States years ago. Physical examination findings and routine laboratory values, including complete blood count and basic metabolic panels, were normal. Electrocardiography revealed nonspecific T-wave inversions, and a series of cardiac biomarkers were negative. A contrast material-enhanced CT angiography pulmonary embolism protocol and cardiac MRI were performed for further evaluation (Figs 1-4). [Figure: see text] [Figure: see text] [Figure: see text] [Figure: see text] [Figure: see text] [Figure: see text].

Diverse cardiopulmonary diseases are associated with distinct xenon magnetic resonance imaging signatures.

BACKGROUND: As an increasing number of patients exhibit concomitant cardiac and pulmonary disease, limitations of standard diagnostic criteria are more frequently encountered. Here, we apply noninvasive 129Xe magnetic resonance imaging (MRI) and spectroscopy to identify patterns of regional gas transfer impairment and haemodynamics that are uniquely associated with chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), left heart failure (LHF) and pulmonary arterial hypertension (PAH). METHODS: Healthy volunteers (n=23) and patients with COPD (n=8), IPF (n=12), LHF (n=6) and PAH (n=10) underwent 129Xe gas transfer imaging and dynamic spectroscopy. For each patient, three-dimensional maps were generated to depict ventilation, barrier uptake (129Xe dissolved in interstitial tissue) and red blood cell (RBC) transfer (129Xe dissolved in RBCs). Dynamic 129Xe spectroscopy was used to quantify cardiogenic oscillations in the RBC signal amplitude and frequency shift. RESULTS: Compared with healthy volunteers, all patient groups exhibited decreased ventilation and RBC transfer (both p≤0.01). Patients with COPD demonstrated more ventilation and barrier defects compared with all other groups (both p≤0.02). In contrast, IPF patients demonstrated elevated barrier uptake compared with all other groups (p≤0.007), and increased RBC amplitude and shift oscillations compared with healthy volunteers (p=0.007 and p≤0.01, respectively). Patients with COPD and PAH both exhibited decreased RBC amplitude oscillations (p=0.02 and p=0.005, respectively) compared with healthy volunteers. LHF was distinguishable from PAH by enhanced RBC amplitude oscillations (p=0.01). CONCLUSION: COPD, IPF, LHF and PAH each exhibit unique 129Xe MRI and dynamic spectroscopy signatures. These metrics may help with diagnostic challenges in cardiopulmonary disease and increase understanding of regional lung function and haemodynamics at the alveolar-capillary level.

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.

Hyperpolarized 129 Xe gas transfer MRI: the transition from 1.5T to 3T.

PURPOSE: Hyperpolarized 129 Xe MRI depicting 3D ventilation, interstitial barrier uptake, and transfer to red blood cells (RBCs) has emerged as a powerful new means of detecting pulmonary disease. However, given the challenging susceptibility environment of the lung, such gas transfer imaging has, thus far, only been implemented at 1.5T. Here, we seek to demonstrate the feasibility of Dixon-based 129 Xe gas transfer MRI at 3T. METHODS: Seven healthy subjects and six patients with pulmonary disorders were recruited to characterize 129 Xe spectral structure, optimize acquisition parameters, and acquire representative images. Imaging used randomized, gradient-spoiled 3D-radial encoding of 1000 gas (0.5° flip) and dissolved (20° flip) views, reconstructed into 3-mm isotropic voxels. The center of k-space was sampled when barrier and RBC compartments were 90° out of phase (TE90 ). A single dissolved phase spectrum was appended to the sequence to measure the global RBC-barrier ratio for Dixon-based decomposition. RESULTS: A 0.69 ms sinc was found to generate minimal off-resonance gas-phase excitation (3.0 ± 0.3% of the dissolved-phase), yielding a TE90 = 0.47 ± 0.02 ms. The RBC and barrier resonance frequencies were shifted by 217.6 ± 0.6 ppm and 197.8 ± 0.2 ppm. The RBC T 2 * was estimated to be ∼1.1 ms, and therefore each read-out was limited to 1.3 ms. 129 Xe gas and dissolved-phase images have sufficient SNR to produce gas transfer maps of similar quality and sensitivity to pathology, as previously obtained at 1.5T. CONCLUSIONS: Despite short dissolved-phase T 2 * , 129 Xe gas transfer MRI is feasible at 3T.

Association Between Pseudotumor Formation and Patient Factors in Metal-on-Metal Total Hip Arthroplasty Population.

BACKGROUND: Pseudotumor formation from metal-on-metal (MoM) hip implants is associated with implant revision. The relationship between pseudotumor type and patient outcomes is unknown. METHODS: We retrospectively reviewed patients with a MoM total hip arthroplasty and metal artifact reduction sequence magnetic resonance imaging. Pseudotumors were graded using a validated classification system by a fellowship-trained radiologist. Patient demographics, metal ion levels, and implant survival were analyzed. RESULTS: Pseudotumors were present in 49 hips (53%). Thirty-two (65%) pseudotumors were cystic thin walled, 8 (16%) were cystic thick walled, and 9 (18%) were solid masses. Patients with pseudotumors had high offset stems (P = .030) but not higher metal ion levels. Patients with thick-walled cystic or solid masses were more likely to be symptomatic (P = .025) and were at increased risk for revision (P = .004) compared to patients with cystic lesions. CONCLUSION: Pseudotumor formation is present in 53% of patients with a MoM total hip arthroplasty, of which 40% were asymptomatic. Patients with thick-walled cystic and solid lesions were more likely to be symptomatic and undergo revision.

Impact of Fluoroscopically Guided Bone Biopsy on Antibiotic Management of Osteomyelitis in the Lower Extremity.

This study evaluated the impact of fluoroscopically guided percutaneous bone biopsy on altering antibiotic regimens in lower extremity osteomyelitis. Eighty-eight patients who received fluoroscopically guided bone biopsies were identified. There was bacterial growth in 28% of bone biopsies overall. The rate of positive culture was decreased in patients started on empiric antibiotics before biopsy (23%) compare with patients without empiric antibiotics (44%). Antibiotic regimens were changed in 24% of patients overall in response to culture data. The majority of positive biopsy cultures (76%) but minority of negative biopsy cultures (3%) resulted in a change to antibiotic regimens. The impact of percutaneous bone biopsy on antibiotic management of adult patients with osteomyelitis diagnosed by magnetic resonance imaging is modest and is decreased in patients previously started on antibiotics. Despite its modest impact, bone biopsy results can provide useful information in antibiotic management, especially when positive (Journal of Surgical Orthopaedic Advances 27(4):277-280, 2018).

How accurate is the label "allergic to iodinated contrast agents"?

BACKGROUND: Iodinated contrast agents (ICAs) are crucial to the use of many imaging studies. Reported allergies to ICAs in the medical record can interfere with optimal diagnostic imaging workups. PURPOSE: To investigate the accuracy with which the label "allergic to ICAs" is applied. MATERIAL AND METHODS: The medical records of 500 patients labeled "allergic to ICAs" at a single tertiary care hospital were reviewed. Patients were separated into three groups based on documentation in their medical records, as follows: Group 1, documented hypersensitivity reaction to ICAs; Group 2, documented ICA exposure with non-hypersensitivity adverse event (Group 2a) or without documented reaction (Group 2b); and Group 3, no documented prior exposure to an ICA. We then further reviewed the EMR to determine whether or not patients had subsequent administration of an ICA, whether or not they were given specific premedication, and whether or not they had a subsequent ICA-related event. RESULTS: A total of 16.6% of patients (n = 83) listed as "allergic to ICAs" had a documented hypersensitivity reaction following ICA administration (Group 1) while 58.6% (n = 293) of patients (Group 2) had a documented exposure to ICAs with either: (i) a non-hypersensitivity adverse event (23.5%, n = 69) or (ii) no record of a reaction to ICAs (76.5%, n = 224). The remaining 24.8% (n = 124), Group 3, had no record of exposure to an ICA, yet still carried the label. CONCLUSION: The majority of patients carrying the label "allergic to ICAs" had no record of a prior hypersensitivity reaction to ICAs.

Computed Tomography Volumetrics for Size Matching in Lung Transplantation for Restrictive Disease.

BACKGROUND: There is no consensus on the optimal allograft sizing strategy for lung transplantation in restrictive lung disease. Current methods that are based on predicted total lung capacity (pTLC) ratios do not account for the diminutive recipient chest size. The study investigators hypothesized that a new sizing ratio incorporating preoperative recipient computed tomographic lung volumes (CTVol) would be associated with postoperative outcomes. METHODS: A retrospective single-institution study was conducted of adults undergoing primary bilateral lung transplantation between January 2016 and July 2020 for restrictive lung disease. CTVol was computed for recipients by using advanced segmentation software. Two sizing ratios were calculated: pTLC ratio (pTLCdonor/pTLCrecipient) and a new volumetric ratio (pTLCdonor/CTVolrecipient). Patients were divided into reference, oversized, and undersized groups on the basis of ratio quintiles, and multivariable models were used to assess the effect of the ratios on primary graft dysfunction and survival. RESULTS: CTVol was successfully acquired in 218 of 220 (99.1%) patients. In adjusted analysis, undersizing on the basis of the volumetric ratio was independently associated with decreased primary graft dysfunction grade 2 or 3 within 72 hours (odds ratio, 0.42; 95% CI, 0.20-0.87; P =.02). The pTLC ratio was not significantly associated with primary graft dysfunction. Oversizing on the basis of the volumetric ratio was independently associated with an increased risk of death (hazard ratio, 2.27; 95% CI, 1.04-4.99; P =.04], whereas the pTLC ratio did not have a significant survival association. CONCLUSIONS: Using computed tomography-acquired lung volumes for donor-recipient size matching in lung transplantation is feasible with advanced segmentation software. This method may be more predictive of outcome compared with current sizing methods, which use gender and height only.

Functional gas exchange measures on 129Xe MRI and spectroscopy are associated with age, sex, and BMI in healthy subjects.

Introduction: Hyperpolarized 129Xe MRI and spectroscopy is a rapidly growing technique for assessing lung function, with applications in a wide range of obstructive, restrictive, and pulmonary vascular disease. However, normal variations in 129Xe measures of gas exchange across healthy subjects are not well characterized, presenting an obstacle to differentiating disease processes from the consequences of expected physiological heterogeneity. Here, we use multivariate models to evaluate the role of age, sex, and BMI in a range of commonly used 129Xe measures of gas exchange. Materials and methods: Healthy subjects (N = 40, 16F, age 44.3 ± 17.8 yrs., min-max 22-87 years) with no history of cardiopulmonary disease underwent 129Xe gas exchange MRI and spectroscopy. We used multivariate linear models to assess the associations of age, sex, and body mass index (BMI) with the RBC:Membrane (RBC:M), membrane to gas (Mem:Gas), and red blood cell to gas (RBC:Gas) ratios, as well as measurements of RBC oscillation amplitude and RBC chemical shift. Results: Age, sex, and BMI were all significant covariates in the RBC:M model. Each additional 10 years of age was associated with a 0.05 decrease in RBC:M (p < 0.001), each additional 10 points of BMI was associated with a decrease of 0.07 (p = 0.02), and males were associated with a 0.17 higher RBC:M than females (p < 0.001). For Mem:Gas, male sex was associated with a decrease and BMI was associated with an increase. For RBC:Gas, age was associated with a decrease and male sex was associated with an increase. RBC oscillation amplitude increased with age and RBC chemical shift was not associated with any of the three covariates. Discussion: 129Xe MRI and spectroscopy measurements in healthy subjects, particularly the widely used RBC:M measurement, exhibit heterogeneity associated in part with variations in subject age, sex, and BMI. Elucidating the contributions of these and other factors to 129Xe gas exchange measurements is a critical component for differentiating disease processes from expected variation in healthy subjects. Notably, the Mem:Gas and RBC chemical shift appear to be stable with aging, suggesting that unexplained deviations in these metrics may be signs of underlying abnormalities.

MR Imaging for the Evaluation of Diffuse Lung Disease: Where Are We?

Patients with diffuse lung diseases require thorough medical and social history and physical examinations, coupled with a multitude of laboratory tests, pulmonary function tests, and radiologic imaging to discern and manage the specific disease. This review summarizes the current state of imaging of various diffuse lung diseases by hyperpolarized MR imaging. The potential of hyperpolarized MR imaging as a clinical tool is outlined as a novel imaging approach that enables further understanding of the cause of diffuse lung diseases, permits earlier detection of disease progression before that found with pulmonary function tests, and can delineate physiologic response to lung therapies.

Noninvasive diagnosis of pulmonary hypertension with hyperpolarised 129Xe magnetic resonance imaging and spectroscopy.

Background: The diagnosis of pulmonary hypertension (PH) remains challenging. Pre- and post-capillary PH have different signatures on noninvasive 129Xe gas-exchange magnetic resonance imaging (MRI) and dynamic MR spectroscopy (MRS). We tested the accuracy of 129Xe MRI/MRS to diagnose PH status compared to right heart catheterisation (RHC). Methods: 129Xe MRI/MRS from 93 subjects was used to develop a diagnostic algorithm, which was tested in 32 patients undergoing RHC on the same day (n=20) or within 5 months (42±40 days) (n=12). Three expert readers, blinded to RHC, used 129Xe MRI/MRS to classify subjects as pre-capillary PH, post-capillary PH, no PH and no interstitial lung disease (ILD), or ILD. Results: For pre-capillary PH, 129Xe MRI/MRS diagnostic accuracy was 75% (95% CI 66-84) with a sensitivity of 67% (95% CI 54-79) and a specificity of 86% (95% CI 75-96); for post-capillary PH accuracy was 69% (95% CI 59-78) with sensitivity of 54% (95% CI 34-74) and specificity of 74% (95% CI 63-84). The model performed well in straightforward cases of pre-capillary PH but was less accurate in its diagnosis in the presence of mixed disease, particularly in the presence of ILD or combined post- and pre-capillary PH. Conclusion: This study demonstrates the potential to develop 129Xe MRI/MRS into a modality with good accuracy in detecting pre- and post-capillary PH. Furthermore, the combination of 129Xe dynamic MRS and gas-exchange MRI uniquely provide concurrent, noninvasive assessment of both haemodynamics and gas-exchange impairment that may aid in the detection of PH.

Prediction of lung malignancy progression and survival with machine learning based on pre-treatment FDG-PET/CT.

BACKGROUND: Pre-treatment FDG-PET/CT scans were analyzed with machine learning to predict progression of lung malignancies and overall survival (OS). METHODS: A retrospective review across three institutions identified patients with a pre-procedure FDG-PET/CT and an associated malignancy diagnosis. Lesions were manually and automatically segmented, and convolutional neural networks (CNNs) were trained using FDG-PET/CT inputs to predict malignancy progression. Performance was evaluated using area under the receiver operating characteristic curve (AUC), accuracy, sensitivity, and specificity. Image features were extracted from CNNs and by radiomics feature extraction, and random survival forests (RSF) were constructed to predict OS. Concordance index (C-index) and integrated brier score (IBS) were used to evaluate OS prediction. FINDINGS: 1168 nodules (n=965 patients) were identified. 792 nodules had progression and 376 were progression-free. The most common malignancies were adenocarcinoma (n=740) and squamous cell carcinoma (n=179). For progression risk, the PET+CT ensemble model with manual segmentation (accuracy=0.790, AUC=0.876) performed similarly to the CT only (accuracy=0.723, AUC=0.888) and better compared to the PET only (accuracy=0.664, AUC=0.669) models. For OS prediction with deep learning features, the PET+CT+clinical RSF ensemble model (C-index=0.737) performed similarly to the CT only (C-index=0.730) and better than the PET only (C-index=0.595), and clinical only (C-index=0.595) models. RSF models constructed with radiomics features had comparable performance to those with CNN features. INTERPRETATION: CNNs trained using pre-treatment FDG-PET/CT and extracted performed well in predicting lung malignancy progression and OS. OS prediction performance with CNN features was comparable to a radiomics approach. The prognostic models could inform treatment options and improve patient care. FUNDING: NIH NHLBI training grant (5T35HL094308-12, John Sollee).

Missed Incidental Pulmonary Embolism: Harnessing Artificial Intelligence to Assess Prevalence and Improve Quality Improvement Opportunities.

PURPOSE: Incidental pulmonary embolism (IPE) can be found on body CT. The aim of this study was to evaluate the feasibility of using artificial intelligence to identify missed IPE on a large number of CT examinations. METHODS: This retrospective analysis included all single-phase chest, abdominal, and pelvic (CAP) and abdominal and pelvic (AP) CT examinations performed at a single center over 1 year, for indications other than identification of PE. Proprietary visual classification and natural language processing software was used to analyze images and reports from all CT examinations, followed by a two-step human adjudication process to classify cases as true positive, false positive, true negative, or false negative. Descriptive statistics were assessed for prevalence of IPE and features (subsegmental versus central, unifocal versus multifocal, right heart strain or not) of missed IPE. Interrater agreement for radiologist readers was also calculated. RESULTS: A total of 11,913 CT examinations (6,398 CAP, 5,515 AP) were included. Thirty false-negative examinations were identified on CAP (0.47%; 95% confidence interval [CI], 0.32%-0.67%) and nineteen false-negative studies on AP (0.34%; 95% CI, 0.21%-0.54%) studies. During manual review, readers showed substantial agreement for identification of IPE on CAP (κ = 0.76; 95% CI, 0.66-0.86) and nearly perfect agreement for identification of IPE on AP (κ = 0.86; 95% CI, 0.76-0.97). Forty-nine missed IPEs (0.41%; 95% CI, 0.30%-0.54%) were ultimately identified, compared with seventy-nine IPEs (0.66%; 95% CI, 0.53%-0.83%) identified at initial clinical interpretation. CONCLUSIONS: Artificial intelligence can efficiently analyze CT examinations to identify potential missed IPE. These results can inform peer-review efforts and quality control and could potentially be implemented in a prospective fashion.

Using hyperpolarized 129Xe gas-exchange MRI to model the regional airspace, membrane, and capillary contributions to diffusing capacity.

Hyperpolarized 129Xe MRI has emerged as a novel means to evaluate pulmonary function via 3D mapping of ventilation, interstitial barrier uptake, and RBC transfer. However, the physiological interpretation of these measurements has yet to be firmly established. Here, we propose a model that uses the three components of 129Xe gas-exchange MRI to estimate accessible alveolar volume (VA), membrane conductance, and capillary blood volume contributions to DLCO. 129Xe ventilated volume (VV) was related to VA by a scaling factor kV = 1.47 with 95% confidence interval [1.42, 1.52], relative 129Xe barrier uptake (normalized by the healthy reference value) was used to estimate the membrane-specific conductance coefficient kB = 10.6 [8.6, 13.6] mL/min/mmHg/L, whereas normalized RBC transfer was used to calculate the capillary blood volume-specific conductance coefficient kR = 13.6 [11.4, 16.7] mL/min/mmHg/L. In this way, the barrier and RBC transfer per unit volume determined the transfer coefficient KCO, which was then multiplied by image-estimated VA to obtain DLCO. The model was built on a cohort of 41 healthy subjects and 101 patients with pulmonary disorders. The resulting 129Xe-derived DLCO correlated strongly (R2 = 0.75, P < 0.001) with the measured values, a finding that was preserved within each individual disease cohort. The ability to use 129Xe MRI measures of ventilation, barrier uptake, and RBC transfer to estimate each of the underlying constituents of DLCO clarifies the interpretation of these images while enabling their use to monitor these aspects of gas exchange independently and regionally.NEW & NOTEWORTHY The diffusing capacity for carbon monoxide (DLCO) is perhaps one of the most comprehensive physiological measures used in pulmonary medicine. Here, we spatially resolve and estimate its key components-accessible alveolar volume, membrane, and capillary blood volume conductances-using hyperpolarized 129Xe MRI of ventilation, interstitial barrier uptake, and red blood cell transfer. This image-derived DLCO correlates strongly with measured values in 142 subjects with a broad range of pulmonary disorders.

Ferumoxytol-enhanced MR Venography of the Central Veins of the Thorax for the Evaluation of Stenosis and Occlusion in Patients with Renal Impairment.

PURPOSE: To assess the diagnostic performance of ferumoxytol-enhanced MR venography for the detection of thoracic central vein stenosis or occlusion with conventional venography as the reference standard. MATERIALS AND METHODS: In this retrospective study, consecutive patients from May 2012 to December 2018 underwent dedicated ferumoxytol-enhanced MR venography of the thoracic central veins and conventional venography within 6 months for detecting central venous stenosis. The central veins were divided into seven segments for evaluation. MR venography images were evaluated by three radiologists for presence of stenosis or occlusion. Interobserver agreement was assessed using Fleiss κ. RESULTS: A total of 35 patients were included (mean age, 49 years; age range, 12-75 years; 18 females). Of the 122 total venous segments with corresponding conventional venography, 73 were stenotic or occluded. The sensitivity and specificity for detection of stenosis or occlusion was 99% and 98%, respectively. The sensitivity and specificity for detecting occlusion alone was 96% and 98%, respectively. MR venography readers demonstrated moderate agreement in their ability to grade stenosis or occlusion (κ = 0.59). There were no adverse events related to contrast agent administration. CONCLUSION: Ferumoxytol-enhanced MR venography demonstrated excellent sensitivity and specificity for detection of thoracic central vein stenosis or occlusion.© RSNA, 2020See also the commentary by Finn in this issue.

Utilization of 19F MRI for Identification of Iraq-Afghanistan War Lung Injury.

INTRODUCTION: There is mounting evidence of respiratory problems related to military service in the Middle East in the past two decades due to environmental exposures during deployment (eg, sand storms and burn pits). This pilot study tests the hypothesis that regional lung function in subjects with prior deployment in Iraq and/or Afghanistan with suspected War Lung Injury (WLI) would be worse than subjects with normal lung function. MATERIALS AND METHODS: Five subjects meeting the inclusion and exclusion criteria were recruited for this pilot study. All subjects underwent spirometry, high-resolution chest computed tomography imaging, and 19F MRI. RESULTS: While the WLI subjects had normal pulmonary function tests and normal high-resolution chest computed tomography evaluations, their regional lung function from 19F MRI was abnormal with compartments with poor function showing slower filling time constants for ventilation. The scans of suspected WLI subjects show higher fractional lung volume with slow filling compartments similar to patients with chronic obstructive pulmonary disease in contrast to normal subjects. CONCLUSIONS: This is consistent with our premise that WLI results in abnormal lung function and reflects small airways dysfunction and suggests that we may be able to provide a more sensitive tool for evaluation of WLI suspected cases.

Generalized Linear Binning to Compare Hyperpolarized 129Xe Ventilation Maps Derived from 3D Radial Gas Exchange Versus Dedicated Multislice Gradient Echo MRI.

RATIONALE: Hyperpolarized 129Xe ventilation MRI is typically acquired using multislice fast gradient recalled echo (GRE), but interleaved 3D radial 129Xe gas transfer MRI now provides dissolved-phase and ventilation images from a single breath. To investigate whether these ventilation images provide equivalent quantitative metrics, we introduce generalized linear binning analysis. METHODS: This study included 36 patients who had undergone both multislice GRE ventilation and 3D radial gas exchange imaging. Images were then quantified by linear binning to classify voxels into one of four clusters: ventilation defect percentage (VDP), Low-, Medium- or High-ventilation percentage (LVP, MVP, HVP). For 3D radial images, linear binning thresholds were generalized using a Box-Cox rescaled reference histogram. We compared the cluster populations from the two ventilation acquisitions both numerically and spatially. RESULTS: Interacquisition Bland-Altman limits of agreement for the clusters between 3D radial vs GRE were (-7% to 5%) for VDP, (-10% to 14%) for LVP, and (-8% to 8%) for HVP. While binning maps were qualitatively similar between acquisitions, their spatial overlap was modest for VDP (Dice = 0.5 ± 0.2), and relatively poor for LVP (0.3 ± 0.1) and HVP (0.2 ± 0.1). CONCLUSION: Both acquisitions yield reasonably concordant VDP and qualitatively similar maps. However, poor regional agreement (Dice) suggests that the two acquisitions cannot yet be used interchangeably. However, further improvements in 3D radial resolution and reconciliation of bias field correction may well obviate the need for a dedicated ventilation scan in many cases.