Machine learning-based computer-aided simple triage (CAST) for COVID-19 pneumonia as compared with triage by board-certified chest radiologists.

PURPOSE: Several reporting systems have been proposed for providing standardized language and diagnostic categories aiming for expressing the likelihood that lung abnormalities on CT images represent COVID-19. We developed a machine learning (ML)-based CT texture analysis software for simple triage based on the RSNA Expert Consensus Statement system. The purpose of this study was to conduct a multi-center and multi-reader study to determine the capability of ML-based computer-aided simple triage (CAST) software based on RSNA expert consensus statements for diagnosis of COVID-19 pneumonia. METHODS: For this multi-center study, 174 cases who had undergone CT and polymerase chain reaction (PCR) tests for COVID-19 were retrospectively included. Their CT data were then assessed by CAST and consensus from three board-certified chest radiologists, after which all cases were classified as either positive or negative. Diagnostic performance was then compared by McNemar's test. To determine radiological finding evaluation capability of CAST, three other board-certified chest radiologists assessed CAST results for radiological findings into five criteria. Finally, accuracies of all radiological evaluations were compared by McNemar's test. RESULTS: A comparison of diagnosis for COVID-19 pneumonia based on RT-PCR results for cases with COVID-19 pneumonia findings on CT showed no significant difference of diagnostic performance between ML-based CAST software and consensus evaluation (p > 0.05). Comparison of agreement on accuracy for all radiological finding evaluations showed that emphysema evaluation accuracy for investigator A (AC = 91.7%) was significantly lower than that for investigators B (100%, p = 0.0009) and C (100%, p = 0.0009). CONCLUSION: This multi-center study shows COVID-19 pneumonia triage by CAST can be considered at least as valid as that by chest expert radiologists and may be capable for playing as useful a complementary role for management of suspected COVID-19 pneumonia patients as well as the RT-PCR test in routine clinical practice.

Lung Magnetic Resonance Imaging: Technical Advancements and Clinical Applications.

ABSTRACT: Since lung magnetic resonance imaging (MRI) became clinically available, limited clinical utility has been suggested for applying MRI to lung diseases. Moreover, clinical applications of MRI for patients with lung diseases or thoracic oncology may vary from country to country due to clinical indications, type of health insurance, or number of MR units available. Because of this situation, members of the Fleischner Society and of the Japanese Society for Magnetic Resonance in Medicine have published new reports to provide appropriate clinical indications for lung MRI. This review article presents a brief history of lung MRI in terms of its technical aspects and major clinical indications, such as (1) what is currently available, (2) what is promising but requires further validation or evaluation, and (3) which developments warrant research-based evaluations in preclinical or patient studies. We hope this article will provide Investigative Radiology readers with further knowledge of the current status of lung MRI and will assist them with the application of appropriate protocols in routine clinical practice.

Chemical Exchange Saturation Transfer MRI: Capability for Predicting Therapeutic Effect of Chemoradiotherapy on Non-Small Cell Lung Cancer Patients.

BACKGROUND: Amide proton transfer (APT) weighted chemical exchange saturation transfer CEST (APTw/CEST) magnetic resonance imaging (MRI) has been suggested as having the potential for assessing the therapeutic effect of brain tumors or rectal cancer. Moreover, diffusion-weighted imaging (DWI) and positron emission tomography fused with computed tomography by means of 2-[fluorine-18]-fluoro-2-deoxy-D-glucose (FDG-PET/CT) have been suggested as useful in same setting. PURPOSE: To compare the capability of APTw/CEST imaging, DWI, and FDG-PET/CT for predicting therapeutic effect of chemoradiotherapy (CRT) on stage III non-small cell lung cancer (NSCLC) patients. STUDY TYPE: Prospective. POPULATION: Eighty-four consecutive patients with Stage III NSCLC, 45 men (age range, 62-75 years; mean age, 71 years) and 39 women (age range, 57-75 years; mean age, 70 years). All patients were then divided into two groups (Response Evaluation Criteria in Solid Tumors [RECIST] responders, consisting of the complete response and partial response groups, and RECIST non-responders, consisting of the stable disease and progressive disease groups). FIELD STRENGTH/SEQUENCE: 3 T, echo planar imaging or fast advanced spin-echo (FASE) sequences for DWI and 2D half Fourier FASE sequences with magnetization transfer pulses for CEST imaging. ASSESSMENT: Magnetization transfer ratio asymmetry (MTRasym ) at 3.5 ppm, apparent diffusion coefficient (ADC), and maximum standard uptake value (SUVmax, ) on PET/CT were assessed by means of region of interest (ROI) measurements at primary tumor. STATISTICAL TESTS: Kaplan-Meier method followed by log-rank test and Cox proportional hazards regression analysis with multivariate analysis. A P value <0.05 was considered statistically significant. RESULTS: Progression-free survival (PFS) and overall survival (OS) had significant difference between two groups. MTRasym at 3.5 ppm (hazard ratio [HR] = 0.70) and SUVmax (HR = 1.41) were identified as significant predictors for PFS. Tumor staging (HR = 0.57) was also significant predictors for OS. DATA CONCLUSION: APTw/CEST imaging showed potential performance as DWI and FDG-PET/CT for predicting the therapeutic effect of CRT on stage III NSCLC patients. LEVEL OF EVIDENCE: 2 TECHNICAL EFFICACY: Stage 1.

State of the Art MR Imaging for Lung Cancer TNM Stage Evaluation.

Since the Radiology Diagnostic Oncology Group (RDOG) report had been published in 1991, magnetic resonance (MR) imaging had limited clinical availability for thoracic malignancy, as well as pulmonary diseases. However, technical advancements in MR systems, such as sequence and reconstruction methods, and adjustments in the clinical protocol for gadolinium contrast media administration have provided fruitful results and validated the utility of MR imaging (MRI) for lung cancer evaluations. These techniques include: (1) contrast-enhanced MR angiography for T-factor evaluation, (2) short-time inversion recovery turbo spin-echo sequences as well as diffusion-weighted imaging (DWI) for N-factor assessment, and (3) whole-body MRI with and without DWI and with positron emission tomography fused with MRI for M-factor or TNM stage evaluation as well as for postoperative recurrence assessment of lung cancer or other thoracic tumors using 1.5 tesla (T) or 3T systems. According to these fruitful results, the Fleischner Society has changed its position to approve of MRI for lung or thoracic diseases. The purpose of this review is to analyze recent advances in lung MRI with a particular focus on lung cancer evaluation, clinical staging, and recurrence assessment evaluation.

Computed DWI MRI Results in Superior Capability for N-Stage Assessment of Non-Small Cell Lung Cancer Than That of Actual DWI, STIR Imaging, and FDG-PET/CT.

BACKGROUND: Computed diffusion-weighted imaging (cDWI) is a mathematical computation technique that generates DWIs for any b-value by using actual DWI (aDWI) data with at least two different b-values and may improve differentiation of metastatic from nonmetastatic lymph nodes. PURPOSE: To determine the appropriate b-value for cDWI to achieve a better diagnostic capability for lymph node staging (N-staging) in non-small cell lung cancer (NSCLC) patients compared to aDWI, short inversion time (TI) inversion recovery (STIR) imaging, or positron emission tomography with 2-[fluorine-18] fluoro-2-deoxy-d-glucose combined with computed tomography (FDG-PET/CT). STUDY TYPE: Prospective. SUBJECTS: A total of 245 (127 males and 118 females; mean age 72 years) consecutive histopathologically confirmed NSCLC patients. FIELD STRENGTH/SEQUENCE: A 3 T, half-Fourier single-shot turbo spin-echo sequence, electrocardiogram (ECG)-triggered STIR fast advanced spin-echo (FASE) sequence with black blood and STIR acquisition and DWI obtained by FASE with b-values of 0 and 1000 sec/mm2 . ASSESSMENT: From aDWIs with b-values of 0 and 1000 (aDWI1000 ) sec/mm2 , cDWI using 400 (cDWI400 ), 600 (cDWI600 ), 800 (cDWI800 ), and 2000 (cDWI2000 ) sec/mm2 were generated. Then, 114 metastatic and 114 nonmetastatic nodes (mediastinal and hilar lymph nodes) were selected and evaluated with a contrast ratio (CR) for each cDWI and aDWI, apparent diffusion coefficient (ADC), lymph node-to-muscle ratio (LMR) on STIR, and maximum standard uptake value (SUVmax ). STATISTICAL TESTS: Receiver operating characteristic curve (ROC) analysis, Youden index, and McNemar's test. RESULTS: Area under the curve (AUC) of CR600 was significantly larger than the CR400 , CR800 , CR2000 , aCR1000 , and SUVmax . Comparison of N-staging accuracy showed that CR600 was significantly higher than CR400 , CR2000 , ADC, aCR1000 , and SUVmax , although there were no significant differences with CR800 (P = 0.99) and LMR (P = 0.99). DATA CONCLUSION: cDWI with b-value at 600 sec/mm2 may have potential to improve N-staging accuracy as compared with aDWI, STIR, and PET/CT. EVIDENCE LEVEL: 2 TECHNICAL EFFICACY: Stage 2.

Efficacy of Ultrashort Echo Time Pulmonary MRI for Lung Nodule Detection and Lung-RADS Classification.

Background Pulmonary MRI with ultrashort echo time (UTE) has been compared with chest CT for nodule detection and classification. However, direct comparisons of these methods' capabilities for Lung CT Screening Reporting and Data System (Lung-RADS) evaluation remain lacking. Purpose To compare the capabilities of pulmonary MRI with UTE with those of standard- or low-dose thin-section CT for Lung-RADS classification. Materials and Methods In this prospective study, standard- and low-dose chest CT (270 mA and 60 mA, respectively) and MRI with UTE were used to examine consecutive participants enrolled between January 2017 and December 2020 who met American College of Radiology Appropriateness Criteria for lung cancer screening with low-dose CT. Probability of nodule presence was assessed for all methods with a five-point visual scoring system by two board-certified radiologists. All nodules were then evaluated in terms of their Lung-RADS classification using each method. To compare nodule detection capability of the three methods, consensus for performances was rated by using jackknife free-response receiver operating characteristic analysis, and sensitivity was compared by means of the McNemar test. In addition, weighted κ statistics were used to determine the agreement between Lung-RADS classification obtained with each method and the reference standard generated from standard-dose CT evaluated by two radiologists who were not included in the image analysis session. Results A total of 205 participants (mean age: 64 years ± 7 [standard deviation], 106 men) with 1073 nodules were enrolled. Figure of merit (FOM) (P < .001) had significant differences among three modalities (standard-dose CT: FOM = 0.91, low-dose CT: FOM = 0.89, pulmonary MRI with UTE: FOM = 0.94), with no evidence of false-positive findings in participants with all modalities (P > .05). Agreements for Lung-RADS classification between all modalities and the reference standard were almost perfect (standard-dose CT: κ = 0.82, P < .001; low-dose CT: κ = 0.82, P < .001; pulmonary MRI with UTE: κ = 0.82, P < .001). Conclusion In a lung cancer screening population, ultrashort echo time pulmonary MRI was comparable to standard- or low-dose CT for Lung CT Screening Reporting and Data System classification. © RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Wielpütz in this issue.

Comparison of Interobserver Agreement and Diagnostic Accuracy for IASLC/ITMIG Thymic Epithelial Tumor Staging Among Co-registered FDG-PET/MRI, Whole-body MRI, Integrated FDG-PET/CT, and Conventional Imaging Examination with and without Contrast Media Administrations.

RATIONALE AND OBJECTIVES: The purpose of this study was to compare the interobserver agreements and diagnostic accuracies for IASLC/ITMIG (International Association for the Study of Lung Cancer/International Thymic Malignancies Interest Group) thymic epithelial tumor staging of co-registered fluorodeoxyglucose positron emission tomography/magnetic resonance imaging (FDG-PET/MRI), MRI, integrated fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT), and conventional imaging examination. MATERIALS AND METHODS: Prospective whole-body MRI including diffusion-weighted imaging, integrated PET/CTs, conventional imaging examinations, pathological examinations, and surgical reports, as well as follow-up examinations, were performed for 64 consecutive patients with thymic epithelial tumor. All FDG-PET/MRIs were co-registered PET data with MRI. TNM staging was evaluated by two radiologists on the basis of the IASLC/ITMIG thymic epithelial tumor staging system. Kappa statistics were determined for evaluations of agreements of all factors between each of the methods and final diagnosis. Finally, the diagnostic accuracy of each factor and of determination of the clinical stage was statistically compared to each other using McNemar test. RESULTS: Agreements for all factors between each method and final diagnosis were assessed as fair, moderate, substantial, or almost perfect (0.28 ≤ kappa value ≤ 0.80; P < .0001). Diagnostic accuracy for N factor of PET/MRI (93.8% [60/64]) and MRI (93.8% [60/64]) was significantly higher than that of conventional imaging examination (81.3% [52/64] vs PET/MRI and MRI; P = .008). In addition, diagnostic accuracy for staging of PET/MRI (84.4% [54/64]) and MRI (84.4 [54/64]) was significantly higher than that of conventional imaging examination (71.9% [46/64] vs PET/MRI and MRI; P = .008). CONCLUSIONS: Whole-body PET/MRI, MRI, and PET/CT have better interobserver agreements and accuracies than conventional imaging examination for the new IASLC/ITMIG thymic epithelial tumor staging.

State-of-the-art MR Imaging for Thoracic Diseases.

Since thoracic MR imaging was first used in a clinical setting, it has been suggested that MR imaging has limited clinical utility for thoracic diseases, especially lung diseases, in comparison with x-ray CT and positron emission tomography (PET)/CT. However, in many countries and states and for specific indications, MR imaging has recently become practicable. In addition, recently developed pulmonary MR imaging with ultra-short TE (UTE) and zero TE (ZTE) has enhanced the utility of MR imaging for thoracic diseases in routine clinical practice. Furthermore, MR imaging has been introduced as being capable of assessing pulmonary function. It should be borne in mind, however, that these applications have so far been academically and clinically used only for healthy volunteers, but not for patients with various pulmonary diseases in Japan or other countries. In 2020, the Fleischner Society published a new report, which provides consensus expert opinions regarding appropriate clinical indications of pulmonary MR imaging for not only oncologic but also pulmonary diseases. This review article presents a brief history of MR imaging for thoracic diseases regarding its technical aspects and major clinical indications in Japan 1) in terms of what is currently available, 2) promising but requiring further validation or evaluation, and 3) developments warranting research investigations in preclinical or patient studies. State-of-the-art MR imaging can non-invasively visualize lung structural and functional abnormalities without ionizing radiation and thus provide an alternative to CT. MR imaging is considered as a tool for providing unique information. Moreover, prospective, randomized, and multi-center trials should be conducted to directly compare MR imaging with conventional methods to determine whether the former has equal or superior clinical relevance. The results of these trials together with continued improvements are expected to update or modify recommendations for the use of MRI in near future.

Small Cell Lung Cancer Staging: Prospective Comparison of Conventional Staging Tests, FDG PET/CT, Whole-Body MRI, and Coregistered FDG PET/MRI.

BACKGROUND. Whole-body MRI and FDG PET/MRI have shown encouraging results for staging of thoracic malignancy but are poorly studied for staging of small cell lung cancer (SCLC). OBJECTIVE. The purpose of our study was to compare the performance of conventional staging tests, FDG PET/CT, whole-body MRI, and FDG PET/MRI for staging of SCLC. METHODS. This prospective study included 98 patients (64 men, 34 women; median age, 74 years) with SCLC who underwent conventional staging tests (brain MRI; neck, chest, and abdominopelvic CT; and bone scintigraphy), FDG PET/CT, and whole-body MRI within 2 weeks before treatment; coregistered FDG PET/MRI was generated. Two nuclear medicine physicians independently reviewed conventional tests and FDG PET/CT examinations in separate sessions, and two chest radiologists independently reviewed whole-body MRI and FDG PET/MRI examinations in separate sessions. Readers assessed T, N, and M categories; TNM stage; and Veterans Administration Lung Cancer Study Group (VALSG) stage. Reader pairs subsequently reached consensus. Stages determined clinically during tumor board sessions served as the reference standard. RESULTS. Accuracy for T category was higher (p < .05) for whole-body MRI (94.9%) and FDG PET/MRI (94.9%) than for FDG PET/CT (85.7%). Accuracy for N category was higher (p < .05) for whole-body MRI (84.7%), FDG PET/MRI (83.7%), and FDG PET/CT (81.6%) than for conventional staging tests (75.5%). Accuracy for M category was higher (p < .05) for whole-body MRI (94.9%), FDG PET/MRI (94.9%), and FDG PET/CT (94.9%) than for conventional staging tests (84.7%). Accuracy for TNM stage was higher (p < .05) for whole-body MRI (88.8%) and FDG PET/MRI (86.7%) than for FDG PET/CT (77.6%) and conventional staging tests (72.4%). Accuracy for VALSG stage was higher (p < .05) for whole-body MRI (95.9%), FDG PET/MRI (95.9%), and FDG PET/CT (98.0%) than for conventional staging tests (82.7%). Interobserver agreement, expressed as kappa coefficients, ranged from 0.81 to 0.94 across imaging tests and staging endpoints. CONCLUSION. FDG PET/CT, whole-body MRI, and coregistered FDG PET/MRI outperformed conventional tests for various staging endpoints in patients with SCLC. Whole-body MRI and FDG PET/MRI outperformed FDG PET/CT for T category and thus TNM stage, indicating the utility of MRI for assessing extent of local invasion in SCLC. CLINICAL IMPACT. Incorporation of either MRI approach may improve initial staging evaluation in SCLC.

Inspiratory/expiratory xenon-enhanced area-detector CT: Capability for quantitative assessment of lung ventilation changes in surgically treated non-small cell lung cancer patients.

PURPOSE: To evaluate the capability of inspiratory/expiratory Xe-enhanced ADCT for assessment of changes in pulmonary function and regional ventilation of surgically treated NSCLC patients. METHOD AND MATERIALS: Forty consecutive surgically treated NSCLC patients underwent pre- and postoperative inspiratory/expiratory Xe-enhanced ADCT and pulmonary function tests. For each patient, pre- and post-operative data were analyzed and pre- and post-operative wash-in (WI) and wash-out (WO) indexes and ventilation ratio (VR=[WI-WO]/WI) maps generated by means of pixel-by-pixel analyses. Differences between pre- and postoperative WI (ΔWI), WO (ΔWO) and VR (ΔVR) were also determined. To determine the relationship between all ventilation index changes and pulmonary functional loss, Pearson's correlation was used to correlate each ventilation index change with the corresponding pulmonary functional parameter change. In addition, stepwise regression analysis was performed for all ventilation index changes and each corresponding pulmonary functional parameter change. RESULTS: FEV1/FVC% change showed fair or good and significant correlations with ΔWI (r = 0.39, p = 0.01) and ΔVR (r = 0.68, p = 0.001), %FEV1 change good or moderate and significant correlations with ΔWI (r = 0.56, p = 0.0001) and ΔVR (r = 0.76, p < 0.0001), and %VC change moderate yet significant correlation with ΔWI (r = 0.65, p < 0.0001) and ΔVR (r = 0.67, p < 0.0001). Stepwise regression analysis demonstrated that FEV1/FVC% change (r2 = 0.56, p < 0.0001) significantly affected two factors, ΔVR (p < 0.0001) and ΔWI (p = 0.006), as did %FEV1 change (r2 = 0.68, p < 0.0001) [ΔVR (p < 0.0001) and ΔWI (p = 0.0001)], and %VC change (r2 = 0.63, p < 0.0001) [ΔVR (p < 0.0001) and ΔWI (p = 0.0001)]. CONCLUSION: Inspiratory/expiratory Xe-enhanced ADCT has the potential to demonstrate that pre- and postoperative ventilation status of surgically treated NSCLC patients correlates with pulmonary function.

Comparison of Diagnostic Accuracy for TNM Stage Among Whole-Body MRI and Coregistered PET/MRI Using 1.5-T and 3-T MRI Systems and Integrated PET/CT for Non-Small Cell Lung Cancer.

OBJECTIVE. The purpose of this study was to compare diagnostic accuracy of TNM stage for whole-body MRI and coregistered PET/MRI using 1.5-T and 3-T MRI systems and PET/CT in patients with non-small cell lung cancer (NSCLC). SUBJECTS AND METHODS. A total of 104 patients with pathologically diagnosed NSCLC underwent whole-body MRI at 1.5 T and 3T and integrated PET/CT, as well as a combination of surgical, pathologic, or follow-up examinations. Whole-body MR images obtained by the five sequences were combined with the PET part of the PET/CT using proprietary software for the PET/MRI studies. The TNM stage obtained with all methods was visually assessed. Kappa statistics were used to determine agreement between TNM stage assessment and final diagnoses, and the McNemar test was used to compare diagnostic accuracy of all methods. RESULTS. Findings of TNM stage on whole-body MRI using 3-T (κ, 0.87; p < 0.0001) and 1.5-T (κ, 0.83; p < 0.0001) systems and for coregistered PET/MRI using a 3-T system (PET/MRI3T; κ, 0.85; p < 0.0001) were rated as significant and almost perfect, and findings for coregistered PET/MRI using a 1.5-T system (PET/MRI1.5T; κ, 0.80; p < 0.0001) and PET/CT (κ, 0.73; p < 0.0001) were rated significant and substantial. Diagnostic accuracy of whole-body MRI using the 3-T system was 88.5% (92/104; p = 0.0002, and using the 1.5-T system it was 84.6% (88/104; p = 0.004); results for PET/MRI3T and PET/MRI1.5T were 86.5% (90/104; p = 0.001) and 81.7% (85/104; p = 0.03), respectively, which were both significantly better than accuracy of results for PET/CT at 76.0% (79/104). Moreover, diagnostic accuracy of whole-body MRI using a 3-T system was significantly higher than that of PET/MRI using a 1.5-T system (p = 0.02). CONCLUSION. Whole-body MRI and coregistered PET/MRI using 3-T and 1.5-T systems are as accurate or more accurate than PET/CT, whereas differences between 3-T and 1.5-T MRI systems are not considered significant.

Dynamic Contrast-enhanced Area-detector CT vs Dynamic Contrast-enhanced Perfusion MRI vs FDG-PET/CT: Comparison of Utility for Quantitative Therapeutic Outcome Prediction for NSCLC Patients Undergoing Chemoradiotherapy.

PURPOSE: To directly compare the utility for therapeutic outcome prediction of dynamic first-pass contrast-enhanced (CE)-perfusion area-detector computed tomography (ADCT), MR imaging assessed with the same mathematical method and 2-[fluorine-18]-fluoro-2-deoxy-d-glucose-positron emission tomography combined with CT (PET/CT) for non-small cell lung cancer (NSCLC) patients treated with chemoradiotherapy. MATERIALS AND METHODS: Forty-three consecutive stage IIIB NSCLC patients, consisting of 25 males (mean age ± standard deviation: 66.6 ± 8.7 years) and 18 females (66.4 ± 8.2 years) underwent PET/CT, dynamic CE-perfusion ADCT and MR imaging, chemoradiotherapy, and follow-up examination. In each patient, total, pulmonary arterial, and systemic arterial perfusions were calculated from both perfusion data and SUVmax on PET/CT, assessed for each targeted lesion, and averaged to determine final values. Receiver operating characteristics analyses were performed to compare the utility for distinguishing responders from non-responders using Response Evaluation Criteria in Solid Tumor (RECIST) 1.1 criteria. Overall survival (OS) assessed with each index were compared between two groups by means of the Kaplan-Meier method followed by the log-rank test. RESULTS: Area under the curve (Az) for total perfusion on ADCT was significantly larger than that of pulmonary arterial perfusion (P < 0.05). Az of total perfusion on MR imaging was significantly larger than that of pulmonary arterial perfusion (P < 0.05). Mean OS of responder and non-responder groups were significantly different for total and systemic arterial (P < 0.05) perfusion. CONCLUSION: Dynamic first-pass CE-perfusion ADCT and MR imaging as well as PET/CT are useful for early prediction of treatment response by NSCLC patients treated with chemoradiotherapy.

Solitary pulmonary nodule: Comparison of quantitative capability for differentiation and management among dynamic CE-perfusion MRI at 3 T system, dynamic CE-perfusion ADCT and FDG-PET/CT.

PURPOSE: To prospectively compare the capability of dynamic first-pass contrast-enhanced (CE) perfusion MR imaging with ultra-short TE and area-detector CT (ADCT), analyzed with the same mathematical methods, and that of FDG-PET/CT for diagnosis and management of solitary pulmonary nodules (SPNs). METHODS AND MATERIALS: Our institutional review board approved this study and written informed consent was obtained from all subjects. A total 57 consecutive patients with 71 nodules prospectively underwent dynamic CE-perfusion ADCT and MR imaging with ultra-short TE, FDG-PET/CT, as well as microbacterial and/or pathological examinations. The nodules were classified into malignant nodules (n = 45) and benign nodules (n = 26). Pulmonary arterial, systemic arterial and total perfusions were determined by means of dual-input maximum slope models on ADCT and MR imaging and maximum values of standard uptake values (SUVmax) on PET/CT. Receiver operating characteristic (ROC) analysis was performed for each index, and sensitivity, specificity and accuracy were compared by McNemar's test. RESULTS: Areas under the curve (Azs) of total perfusion on ADCT (Az = 0.89) and MR imaging (Az = 0.88) were significantly larger than those of systemic arterial perfusion and MR imaging (p<0.05). Accuracy of total perfusion on ADCT (87.3% [62/71]) and MR imaging (87.3% [62/71]) was significantly higher than that of systemic arterial perfusion for both methods (77.5% [55/71] p = 0.02) and SUVmax (78.9% [56/71], p = 0.03). CONCLUSION: Dynamic CE-perfusion MR imaging with ultra-short TE and ADCT and have similar potential capabilities, and are superior to FDG-PET/CT in this setting.

Radiation dose reduction techniques for chest CT: Principles and clinical results.

Computer tomography plays a major role in the evaluation of thoracic diseases, especially since the advent of the multidetector-row CT (MDCT) technology. However, the increase use of this technique has raised some concerns about the resulting radiation dose. In this review, we will present the various methods allowing limiting the radiation dose exposure resulting from chest CT acquisitions, including the options of image filtering and iterative reconstruction (IR) algorithms. The clinical applications of reduced dose protocols will be reviewed, especially for lung nodule detection and diagnosis of pulmonary thromboembolism. The performance of reduced dose protocols for infiltrative lung disease assessment will also be discussed. Lastly, the influence of using IR algorithms on computer-aided detection and volumetry of lung nodules, as well as on quantitative and functional assessment of chest diseases will be presented and discussed.

Whole-Body MRI: Comparison of Its Capability for TNM Staging of Malignant Pleural Mesothelioma With That of Coregistered PET/MRI, Integrated FDG PET/CT, and Conventional Imaging.

OBJECTIVE: The purpose of this study was to compare the diagnostic accuracy of whole-body MRI, coregistered FDG PET/MRI, integrated FDG PET/CT, and conventional imaging examination including bone scintigraphy, contrast-enhanced brain MRI, and CT for malignant pleural mesothelioma (MPM) staging according to the new International Association for the Study of Lung Cancer (IASLC) system. SUBJECTS AND METHODS: The study subjects were 23 consecutively registered patients with MPM (15 men, eight women; mean age, 68 years for both sexes) who had prospectively undergone whole-body FDG PET/CT, whole-body MRI, conventional radiologic examination, surgical or conventional treatments, pathologic examination, and follow-up conventional imaging examinations between January 2011 and December 2017. TNM staging was evaluated by two independent readers. Kappa statistics and chi-square tests were used for evaluation agreements on each factor and clinical stage between each method and final diagnosis. The diagnostic accuracy of each method was statistically compared by use of McNemar test. RESULTS: The kappa values for each factor between each method and final diagnosis were significant (p < 0.0001) and ranged between 0.33 and 0.91. Kappa values between final diagnosis and stage evaluation were also significant (p < 0.0001) and ranged between 0.57 and 0.91. The diagnostic accuracy of N and stage assessment of whole-body MRI and FDG PET/MRI was significantly higher than that of conventional imaging examination (N factor, p < 0.05; stage, p < 0.05). CONCLUSION: The diagnostic accuracy of whole-body MRI, FDG PET/MRI, and FDG PET/CT for TNM stage assessment based on the new IASLC MPM staging system is greater than that of conventional imaging examination.

Morphologic Characterization of Pulmonary Nodules With Ultrashort TE MRI at 3T.

OBJECTIVE: Ultrashort TE (UTE) MRI has been shown to deliver high-resolution images comparable to CT images. Here we evaluate the potential of UTE-MRI for precise lung nodule characterization. SUBJECTS AND METHODS: Fifty-one patients (mean [± SD] age, 68.7 ± 10.8 years) with 119 nodules or masses (mean size, 17.4 ± 16.3 mm; range, 4-88 mm) prospectively underwent CT (1-mm slice thickness) and UTE-MRI (TE, 192 µs; 1 mm3 resolution). Two radiologists assessed nodule dimensions and morphologic features (i.e., attenuation, margins, and internal lucencies), in consensus for CT and in a blinded fashion for UTE-MRI. Sensitivity, specificity, and kappa statistics were calculated in reference to CT. RESULTS: Readers 1 and 2 underestimated the nodules' long axial diameter with UTEMRI by 1.2 ± 3.4 and 2.1 ± 4.2 mm, respectively (p < 0.001). The sensitivity and specificity of UTE-MRI for subsolid attenuation were 95.9% and 70.3%, respectively, for reader 1 and 97.1% and 71.4%, respectively, for reader 2 (κ = 0.71 and 0.68). With regard to margin characteristics, for lobulation, sensitivity was 70.6% and 54.9%, and specificity was 93.2% and 96.3% for readers 1 and 2, respectively; for spiculation, sensitivity was 61.5% and 48.0%, and specificity was 95.2% and 95.0%; and for pleural tags, sensitivity was 87.0% and 73.3%, and specificity was 93.8% and 95.0%. Finally, for internal lucencies, sensitivity was 72.7% and 61.3%, and specificity was 96.1% and 97.3% for readers 1 and 2, respectively (κ = 0.64-0.81 for reader 1 and 0.48-0.72 for reader 2). Interreader agreement for attenuation, margin characteristics, and lucencies was substantial to almost perfect with few exceptions (κ = 0.51-0.90). CONCLUSION: UTE-MRI systematically underestimated dimension measurements by approximately 1-2 mm but otherwise showed high diagnostic properties and interreader agreement, yet unprecedented by MRI, for nodule morphologic assessment.

Amide proton transfer-weighted imaging to differentiate malignant from benign pulmonary lesions: Comparison with diffusion-weighted imaging and FDG-PET/CT.

PURPOSE: To compare the capability of amide proton transfer-weighted (APTw) imaging, diffusion-weighted imaging (DWI), and FDG-PET/CT for the differentiation of malignant from benign pulmonary nodules. MATERIALS AND METHODS: In all, 82 consecutive patients with pulmonary nodules underwent APTw imaging and DWI with a 3T system, and FDG-PET/CT. All nodules were divided as either malignant (n = 49) or benign (n = 39) groups based on pathological and follow-up examinations. To evaluate the capability for differentiation of malignant from benign nodules, magnetization transfer ratio asymmetry (MTRasym )(3.5ppm) on APTw imaging, apparent diffusion coefficient (ADC), and maximum value of standard uptake value (SUVmax ) were assessed. Receiver operating characteristic (ROC) analyses were performed to computationally determine each feasible threshold value. Next, McNemar's test was used for comparing diagnostic performance with each other as well as with a combination of the significant factors determined by multivariate logistic regression analysis. RESULTS: Although sensitivity of ADC was significantly higher than that of MTRasym (3.5 ppm) (P = 0.002) and SUVmax (P = 0.004), specificity of MTRasym (3.5 ppm) and SUVmax was significantly higher than that of ADC (P < 0.05). Sensitivity of combined MTRasym (3.5ppm) with SUVmax was significantly higher than that of MTRasym (3.5ppm) (P = 0.001) and SUVmax (P = 0.002) alone. Moreover, specificity and accuracy of combined MTRasym (3.5ppm) with SUVmax were significantly higher than that of ADC (specificity: P = 0.002, accuracy: P = 0.008). CONCLUSION: APTw imaging appears to be as useful as DWI and FDG-PET/CT for differentiation of malignant from benign nodules. LEVEL OF EVIDENCE: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:1013-1021.

Comparison of fat suppression capability for chest MR imaging with Dixon, SPAIR and STIR techniques at 3 Tesla MR system.

PURPOSE: To directly compare fat suppression efficacy of Dixon, spectral attenuated inversion recovery (SPAIR) and short tau inversion recovery (STIR) techniques for a 3T MR system. MATERIALS AND METHODS: Nineteen consecutive patients (11 men, 8 women; mean age 67.9years) underwent chest MR imaging. Contrast-noise ratio (CNR) between muscle and fat (CNRFat) was calculated by ROI measurement. Then, two radiologists used a five-point scale for visual assessment of image quality, fat suppression capability and lesion detection. Next, the quantitative calculations obtained with all three techniques were compared by means of Tukey's honest significant difference (HSD) test. Inter-observer agreements were assessed by kappa statistics and χ2 test. Fisher's least significant difference (LSD) test was used for comparison among all scores. RESULTS: CNRFat of SPAIR were significantly higher than those of Dixon and STIR (p<0.001). Inter-observer agreements were assessed as significantly moderate, substantial or almost perfect (0.51<κ<0.89, p<0.0001). Total image quality and fat suppression capability of Dixon and STIR were significantly higher than those of SPAIR (p<0.001). CONCLUSION: Dixon technique has better fat suppression capability on T2-weighted turbo SE imaging than SPAIR technique on chest MR imaging examined with a 3T MR system, although it can't substitute STIR technique on fat suppression and lesion visualization.

Dynamic Contrast-Enhanced Perfusion Area-Detector CT: Preliminary Comparison of Diagnostic Performance for N Stage Assessment With FDG PET/CT in Non-Small Cell Lung Cancer.

OBJECTIVE: The objective of our study was to directly compare the capability of dynamic first-pass contrast-enhanced (CE) perfusion area-detector CT (ADCT) and FDG PET/CT for differentiation of metastatic from nonmetastatic lymph nodes and assessment of N stage in patients with non-small cell lung carcinoma (NSCLC). SUBJECTS AND METHODS: Seventy-seven consecutive patients, 45 men (mean age ± SD, 70.4 ± 5.9 years) and 32 women (71.2 ± 7.7 years), underwent dynamic first-pass CE-perfusion ADCT at two or three different positions for covering the entire thorax, FDG PET/CT, surgical treatment, and pathologic examination. From all ADCT data for each of the subjects, a whole-chest perfusion map was computationally generated using the dual- and single-input maximum slope and Patlak plot methods. For quantitative N stage assessment, perfusion parameters and the maximum standardized uptake value (SUVmax) for each lymph node were determined by measuring the relevant ROI. ROC curve analyses were performed for comparing the diagnostic capability of each of the methods on a per-node basis. N stages evaluated by each of the indexes were then statistically compared with the final pathologic diagnosis by means of chi-square and kappa statistics. RESULTS: The area under the ROC curve (Az) values of systemic arterial perfusion (Az = 0.89), permeability surface (Az = 0.78), and SUVmax (Az = 0.85) were significantly larger than the Az values of total perfusion (Az = 0.70, p < 0.05) and distribution volume (Az = 0.55, p < 0.05). For each of the threshold values, agreement for systemic arterial perfusion calculated using the dual-input maximum slope model was substantial (κ = 0.70, p < 0.0001), and agreement for SUVmax was moderate (κ = 0.60, p < 0.0001). CONCLUSION: Dynamic first-pass CE-perfusion ADCT is as useful as FDG PET/CT for the differentiation of metastatic from nonmetastatic lymph nodes and assessment of N stage in patients with NSCLC.