Building blocks for thoracic MRI: Challenges, sequences, and protocol design

Adult chronic non-bacterial osteitis (CNO): An illustrated CT-based radiological guideline

Chronic non-bacterial osteitis (CNO) is a rare chronic auto-inflammatory bone disease. In adults, it primarily affects the axial skeleton, especially the anterior chest wall, followed by the spine and the mandible. Whole Body-MRI (WB-MRI) or computed tomography (CT) combined with nuclear imaging are the preferred imaging techniques for the diagnosis and monitoring of adult CNO. However, WB-MRI has several important limitations when addressing adult CNO, due to the difficult evaluation of bone marrow edema in areas of marked sclerosis.Extensive sclerosis is one of the most important radiological manifestations of the disease, together with hyperostosis, calcification of capsules and ligaments, ankylosis, erosions, and secondary degenerative changes, all easily assessable with CT, which also represents a technique available in the majority of hospitals and countries.CNO disease course is generally chronic, relapsing and remitting over time. For the evaluation of the disease activity, CT alone is insufficient, but it can be combined with sodium fluoride-18 positron emission tomography/computed tomography ([18F]NaF-PET/CT), which gives multiple advantages and strongly correlates with clinical disease activity, qualifying the imaging tool as a disease-monitoring instrument.This manuscript provides a comprehensive overview of characteristic CT features of adult CNO in different "target" locations of the axial skeleton, thereby helping to differentiate them from pitfalls, providing guidance in the (early) detection of the disease.

Expert consensus recommendations for the diagnosis and treatment of chronic non-bacterial osteitis (CNO) in adults

BACKGROUND

There is considerable practice variation in labelling, diagnosis and treatment of adults with sterile bone inflammation. We developed a expert consensus recommendations on the disease definition, diagnosis and treatment of this rare condition.

METHODS

Systematic literature review and Grading of Recommendations, Assessment, Development and Evaluations-based appraisal of evidence, two Delphi surveys and three digital and in-person consensus meetings with a multidisciplinary expert panel and patient representatives.

RESULTS

A consensus disease definition was developed and the term 'chronic non-bacterial osteitis' (CNO) is proposed to describe adults with sterile bone inflammation. For initial imaging evaluation of adults with suspected CNO, the panel recommends MRI or otherwise CT combined with nuclear imaging. Whole-body imaging at initial evaluation can be considered for diagnostic and prognostic purposes. Suggested first-line treatment in adults with active CNO includes nonsteroidal anti-inflammatory drugs/cyclooxygenase 2-inhibitors. Second-line treatment preferably consists of intravenous bisphosphonates, and otherwise tumour necrosis factor-α inhibitors. Choice between them should be individualised, considering the presence of additional inflammatory features. The panel further discusses outcome measures, follow-up and management of adverse events and complications.

CONCLUSIONS AND FUTURE PERSPECTIVES

These expert consensus recommendations are intended to support healthcare professionals worldwide in their care for adults with CNO. They also lay the groundwork for establishing international patient registries, translational research lines and multicentre trials, all of which are urgently required.

Unlocking the Potential of Chest MRI: Strategies for Establishing a Successful Practice

Chest MRI is a valuable tool for assessing chest structures, particularly when CT produces inconclusive results. MRI provides exceptional soft-tissue resolution and enables the determination of lesion location, size, and invasion into neighboring structures. Its applications span various clinical scenarios, including the differentiation of non-tumorous and tumorous conditions in the mediastinum or pleura, planning of surgical interventions and treatments for such tumors, evaluation of post-treatment recurrence, staging of lung cancer, and diagnosis of progressive massive fibrosis. Despite the technical hurdles posed by cardiac and respiratory motion, advancements in sequence and scan techniques have enabled high-quality chest MRI examinations to be conducted across diverse clinical settings. This pictorial essay aims to offer comprehensive resources and strategies for radiologists to integrate chest MRI into clinical practice and to overcome its present challenges.

Evaluation of Pulmonary Nodules by Radiologists vs. Radiomics in Stand-Alone and Complementary CT and MRI

Increased attention has been given to MRI in radiation-free screening for malignant nodules in recent years. Our objective was to compare the performance of human readers and radiomic feature analysis based on stand-alone and complementary CT and MRI imaging in classifying pulmonary nodules. This single-center study comprises patients with CT findings of pulmonary nodules who underwent additional lung MRI and whose nodules were classified as benign/malignant by resection. For radiomic features analysis, 2D segmentation was performed for each lung nodule on axial CT, T2-weighted (T2w), and diffusion (DWI) images. The 105 extracted features were reduced by iterative backward selection. The performance of radiomics and human readers was compared by calculating accuracy with Clopper-Pearson confidence intervals. Fifty patients (mean age 63 +/- 10 years) with 66 pulmonary nodules (40 malignant) were evaluated. ACC values for radiomic features analysis vs. radiologists based on CT alone (0.68; 95%CI: 0.56, 0.79 vs. 0.59; 95%CI: 0.46, 0.71), T2w alone (0.65; 95%CI: 0.52, 0.77 vs. 0.68; 95%CI: 0.54, 0.78), DWI alone (0.61; 95%CI:0.48, 0.72 vs. 0.73; 95%CI: 0.60, 0.83), combined T2w/DWI (0.73; 95%CI: 0.60, 0.83 vs. 0.70; 95%CI: 0.57, 0.80), and combined CT/T2w/DWI (0.83; 95%CI: 0.72, 0.91 vs. 0.64; 95%CI: 0.51, 0.75) were calculated. This study is the first to show that by combining quantitative image information from CT, T2w, and DWI datasets, pulmonary nodule assessment through radiomics analysis is superior to using one modality alone, even exceeding human readers' performance.

18F-Sodium fluoride PET-CT visualizes disease activity in chronic nonbacterial osteitis in adults

Chronic nonbacterial osteitis (CNO) is a rare disease spectrum, which lacks biomarkers for disease activity. Sodium fluoride-18 positron emission tomography/computed tomography ([18F]NaF-PET/CT) is a sensitive imaging tool for bone diseases and yields quantitative data on bone turnover. We evaluated the capacities of [18F]NaF-PET/CT to provide structural and functional assessment in adult CNO. A coss-sectional study was performed including 43 adult patients with CNO and 16 controls (patients referred for suspected, but not diagnosed with CNO) who underwent [18F]NaF-PET/CT at our expert clinic. Structural features were compared between patients and controls, and maximal standardized uptake values (SUVmax [g/mL]) were calculated for bone lesions, soft tissue/joint lesions, and reference bone. SUVmax was correlated with clinical disease activity in patients. Structural assessment revealed manubrial and costal sclerosis/hyperostosis and calcification of the costoclavicular ligament as typical features associated with CNO. SUVmax of CNO lesions was higher compared with in-patient reference bone (mean paired difference: 11.4; 95% CI: 9.4-13.5; p < .001) and controls (mean difference: 12.4; 95%CI: 9.1-15.8; p < .001). The highest SUVmax values were found in soft tissue and joint areas such as the costoclavicular ligament and manubriosternal joint, and these correlated with erythrocyte sedimentation rate in patients (correlation coefficient: 0.546; p < .002). Our data suggest that [18F]NaF-PET/CT is a promising imaging tool for adult CNO, allowing for detailed structural evaluation of its typical bone, soft-tissue, and joint features. At the same time, [18F]NaF-PET/CT yields quantitative bone remodeling data that represent the pathologically increased bone turnover and the process of new bone formation. Further studies should investigate the application of quantified [18F]NaF uptake as a novel biomarker for disease activity in CNO, and its utility to steer clinical decision making.

Diagnostic and therapeutic practices in adult chronic nonbacterial osteomyelitis (CNO)

BACKGROUND

Chronic nonbacterial osteomyelitis (CNO) is a rare, and impactful auto-inflammatory bone disease occurring in children and adults. Clinical care for CNO is challenging, as the condition lacks validated classification criteria and evidence-based therapies. This study aimed to map the current diagnostic and therapeutic practices for CNO in adults, as a first step towards a standardized disease definition and future consensus treatment plans.

METHODS

A primary survey was spread among global rheumatological/bone networks and 57 experts as identified from literature (May 2022), covering terminology, diagnostic tools (clinical, radiological, biochemical) and treatment steps. A secondary survey (sent to primary survey responders in August 2022) further queried key diagnostic features, treatment motivations, disease activity and treatment response monitoring.

RESULTS

36 and 23 physicians completed the primary and secondary survey respectively. Diagnosis was mainly based on individual physician assessment, in which the combination of chronic relapsing-remitting bone pain with radiologically-proven osteitis/osteomyelitis, sclerosis, hyperostosis and increased isotope uptake on bone scintigraphy were reported indicative of CNO. Physicians appeared more likely to refer to the condition as synovitis, acne, pustulosis, hyperostosis, osteitis (SAPHO) syndrome in the presence of joint and skin pathology. MRI was most frequently performed, and the preferred diagnostic test for 47%. X-rays were second-most frequently used, although considered least informative of all available tools. Typical imaging features reported were hyperostosis, osteitis, osteosclerosis, bone marrow edema, while degeneration, soft tissue calcification, and ankylosis were not regarded characteristic. Inflammation markers and bone markers were generally regarded unhelpful for diagnostic and monitoring purposes and physicians infrequently performed bone biopsies. Management strategies diverged, including indications for treatment, response monitoring and declaration of remission. Step-1 treatment consisted of non-steroidal anti-inflammatory drugs/COX-2 inhibitors (83%). Common step 2-3 treatments were pamidronate, methotrexate, and TNF-a-inhibition (anti-TNFα), the latter two regarded especially convenient to co-target extra-skeletal inflammation in SAPHO syndrome. Overall pamidronate and anti-TNFα and were considered the most effective treatments.

CONCLUSIONS

Following from our survey data, adult CNO is a broad and insufficiently characterized disease spectrum, including extra-osseous features. MRI is the favoured imaging diagnostic, and management strategies vary significantly. Overall, pamidronate and anti-TNFα are regarded most successful. The results lay out current practices for adult CNO, which may serve as backbone for a future consensus clinical guideline.

Diffusion-weighted Imaging of the Chest: A Primer for Radiologists

Diffusion-weighted imaging (DWI) is a fundamental sequence not only in neuroimaging but also in oncologic imaging and has emerging applications for MRI evaluation of the chest. DWI can be used in clinical practice to enhance lesion conspicuity, tissue characterization, and treatment response. While the spatial resolution of DWI is in the order of millimeters, changes in diffusion can be measured on the micrometer scale. As such, DWI sequences can provide important functional information to MRI evaluation of the chest but require careful optimization of acquisition parameters, notably selection of b values, application of parallel imaging, fat saturation, and motion correction techniques. Along with assessment of morphologic and other functional features, evaluation of DWI signal attenuation and apparent diffusion coefficient maps can aid in tissue characterization. DWI is a noninvasive noncontrast acquisition with an inherent quantitative nature and excellent reproducibility. The outstanding contrast-to-noise ratio provided by DWI can be used to improve detection of pulmonary, mediastinal, and pleural lesions, to identify the benign nature of complex cysts, to characterize the solid portions of cystic lesions, and to classify chest lesions as benign or malignant. DWI has several advantages over fluorine 18 (18F)-fluorodeoxyglucose PET/CT in the assessment, TNM staging, and treatment monitoring of lung cancer and other thoracic neoplasms with conventional or more recently developed therapies. © RSNA, 2023 Quiz questions for this article are available in the supplemental material. Supplemental material and the slide presentation from the RSNA Annual Meeting are available for this article.

Sensitivity and specificity of magnetic resonance imaging in routine diagnosis of pulmonary lesions: a comparison with computed tomography

BACKGROUND

State-of-the-art thoracic magnetic resonance imaging (MRI) plays a complementary role in the assessment of pulmonary nodules/masses which potentially indicate to cancer. We aimed to evaluate the sensitivity and specificity of MRI in diagnosis of pulmonary nodules/masses.

METHODS

Sixty-eight patients with computed tomography (CT)-detected pulmonary nodules/masses underwent 3T MRI (T1-VIBE, T1-starVIBE, T2-fBLADE turbo spin-echo, and T2-SPACE). The detection rate was calculated for each of the different subgroups of pulmonary nodules according to lung imaging reporting and data system (Lung-RADS). The four MRI sequences were compared in terms of detection rate and image quality-signal to noise ratio (SNR), contrast to noise ratio (CNR) and 5-point scoring scale. Agreement of lesion size measurement between CT and MRI was assessed by intraclass correlation coefficient (ICC). The picture-SNR, lesion-SNR and CNR of each sequence were analyzed by Mann-Whitney U test.

RESULTS

In total, 232 pulmonary lesions were detected by CT. The CT showed 86 solid nodules (SNs) <6 mm, 15 SNs between 6-8 mm, 35 SNs between 8-15 mm, and 52 SNs between 15-30 mm. The T1-VIBE, T1-starVIBE, T2-fBLADE TSE and T2-SPACE sequences accurately detected 141 SNs (141/188, 75%/83.3%), 150 SNs (150/188, 79.8%/100%), 166 SNs (166/188, 88.3%/66.7%) and 169 SNs (169/188, 89.9%/53.3%), respectively. Four ground glass nodules (GGNs) (4/6) were detected by T2-fBLADE TSE. Twelve part-solid nodules (PSNs) (12/22) were detected by T1-VIBE and 20 PSNs (20/22) by T2-SPACE. A total of 100 lesions (2.2±1.4 cm, 0.8-7.3 cm) were accurately detected and measured by the four MRI sequences with ICC >0.96. The picture-SNR, lesion-SNR and CNR by T1-starVIBE were higher than those by T1-VIBE (P<0.001). The lesion-SNR and CNR by T2-fBLADE TSE were higher than those by T2-SPACE (P=0.006, 0.038). 86% of images by T1-starVIBE, 92% by T2-fBLADE TSE, 90% by T2-SPACE and 93% by T1-VIBE were scored 3 or more.

CONCLUSIONS

MRI achieves high sensitivity and specificity for different type of pulmonary nodules detection and is an effective alternative to CT as a diagnostic tool for pulmonary nodules.

Detection of lung lesions in breath-hold VIBE and free-breathing Spiral VIBE MRI compared to CT

BACKGROUND

Detection of pulmonary nodules in MRI requires fast imaging strategies without respiratory motion impairment, such as single-breath-hold Cartesian VIBE. As patients with pulmonary diseases have limited breath-hold capacities, this study investigates the clinical feasibility of non-Cartesian Spiral VIBE under free-breathing compared to CT as the gold standard.

METHODS

Prospective analysis of 27 oncological patients examined in PET/CT and PET/MR. A novel motion-robust 3D ultrashort-echo-time (UTE) MR sequence was evaluated in comparison with CT and conventional breath-hold MR. CT scans were performed under breath-hold in end-expiratory and end-inspiratory position (CT ex, CT in). MR data was acquired with non-contrast-enhanced breath-hold Cartesian VIBE followed by a free-breathing 3D UTE Spiral VIBE. Impact of respiratory motion on pulmonary evaluation was investigated by two readers in Cartesian VIBE, followed by UTE Spiral VIBE and CT ex and the reference standard of CT in. Diagnostic accuracy was calculated, and visual image quality assessed.

RESULTS

Higher detection rate and sensitivity of pulmonary nodules in free-breathing UTE Spiral VIBE in comparison with breath-hold Cartesian VIBE were found for lesions > 10 mm (UTE Spiral VIBE/VIBE/CT ex): 93%/54%/100%; Lesions 5-10 mm: 67%/25%/ 92%; Lesions < 5 mm: 11%/11%/78%. Lobe-based analysis revealed sensitivities and specificities of 64%/96%/41% and 96%/93%/100% for UTE Spiral VIBE/VIBE/CT ex.

CONCLUSION

Free-breathing UTE Spiral VIBE indicates higher sensitivity for detection of pulmonary nodules than breath-hold Cartesian VIBE and is a promising but time-consuming approach. However, sensitivity and specificity of inspiratory CT remain superior in comparison and should be preferred for detection of pulmonary lesions.

Novel Thoracic MRI Approaches for the Assessment of Pulmonary Physiology and Inflammation

Excessive pulmonary inflammation can lead to damage of lung tissue, airway remodelling and established structural lung disease. Novel therapeutics that specifically target inflammatory pathways are becoming increasingly common in clinical practice, but there is yet to be a similar stepwise change in pulmonary diagnostic tools. A variety of thoracic magnetic resonance imaging (MRI) tools are currently in development, which may soon fulfil this emerging clinical need for highly sensitive assessments of lung structure and function. Given conventional MRI techniques are poorly suited to lung imaging, alternate strategies have been developed, including the use of inhaled contrast agents, intravenous contrast and specialized lung MR sequences. In this chapter, we discuss technical challenges of performing MRI of the lungs and how they may be overcome. Key thoracic MRI modalities are reviewed, namely, hyperpolarized noble gas MRI, oxygen-enhanced MRI (OE-MRI), ultrashort echo time (UTE) MRI and dynamic contrast-enhanced (DCE) MRI. Finally, we consider potential clinical applications of these techniques including phenotyping of lung disease, evaluation of novel pulmonary therapeutic efficacy and longitudinal assessment of specific patient groups.

Added Value of Magnetic Resonance Imaging for the Evaluation of Mediastinal Lesions

The high soft tissue contrast and tissue characterization properties of magnetic resonance imaging allow further characterization of indeterminate mediastinal lesions on chest radiography and computed tomography, increasing diagnostic specificity, preventing unnecessary intervention, and guiding intervention or surgery when needed. The combination of its higher soft tissue contrast and ability to image dynamically during free breathing, without ionizing radiation exposure, allows more thorough and readily appreciable assessment of a lesion's invasiveness and assessment of phrenic nerve involvement, with significant implications for prognostic clinical staging and surgical management.

Magnetic Resonance Angiography of the Thoracic Vasculature: Technique and Applications

Magnetic resonance angiography (MRA) is a powerful clinical tool for evaluation of the thoracic vasculature. MRA can be performed on nearly any magnetic resonance imaging (MRI) scanner, and provides images of high diagnostic quality without the use of ionizing radiation. While computed tomographic angiography (CTA) is preferred in the evaluation of hemodynamically unstable patients, MRA represents an important tool for evaluation of the thoracic vasculature in stable patients. Contrast-enhanced MRA is generally performed unless there is a specific contraindication, as it shortens the duration of the exam and provides images of higher diagnostic quality than noncontrast MRA. However, intravenous contrast is often not required to obtain a diagnostic evaluation for most clinical indications. Indeed, a variety of noncontrast MRA techniques are used for thoracic imaging, often in conjunction with contrast-enhanced MRA, each of which has a differing degree of reliance on flowing blood to produce the desired vascular signal. In this article we review contrast-enhanced MRA, with a focus on contrast agents, methods of bolus timing, and considerations in imaging acquisition. Next, we cover the mechanism of contrast, strengths, and weaknesses of various noncontrast MRA techniques. Finally, we present an approach to protocol development and review representative protocols used at our institution for a variety of thoracic applications. Further attention will be devoted to additional techniques employed to address specific clinical questions, such as delayed contrast-enhanced imaging, provocative maneuvers, electrocardiogram and respiratory gating, and phase-contrast imaging. The purpose of this article is to review basic techniques and methodology in thoracic MRA, discuss an approach to protocol development, and illustrate commonly encountered pathology on thoracic MRA examinations. Level of Evidence 5 Technical Efficacy Stage 3.