Lung morphology: fast MR imaging assessment with a volumetric interpolated breath-hold technique: initial experience with patients

[Magnetic resonance imaging of the lung : State of the art]

Due to the low proton density of the lung parenchyma and the rapid signal decay at the air-tissue interfaces, for a long time the lungs were difficult to access using magnetic resonance imaging (MRI); however, technical advances could address most of these obstacles. Pulmonary alterations associated with tissue proliferation ("plus pathologies"), can now be detected with high diagnostic accuracy because of the locally increased proton density. Compared to computed tomography (CT), MRI provides a comprehensive range of functional imaging procedures (respiratory mechanics, perfusion and ventilation). In addition, as a radiation-free noninvasive examination modality, it enables repeated examinations for assessment of the course or monitoring of the effects of treatment, even in children. This article discusses the technical aspects, gives suggestions for protocols and explains the role of MRI of the lungs in the routine assessment of various diseases.

Motion-compensated low-rank reconstruction for simultaneous structural and functional UTE lung MRI

PURPOSE

Three-dimensional UTE MRI has shown the ability to provide simultaneous structural and functional lung imaging, but it is limited by respiratory motion and relatively low lung parenchyma SNR. The purpose of this paper is to improve this imaging by using a respiratory phase-resolved reconstruction approach, named motion-compensated low-rank reconstruction (MoCoLoR), which directly incorporates motion compensation into a low-rank constrained reconstruction model for highly efficient use of the acquired data.

THEORY AND METHODS

The MoCoLoR reconstruction is formulated as an optimization problem that includes a low-rank constraint using estimated motion fields to reduce the rank, optimizing over both the motion fields and reconstructed images. The proposed reconstruction along with XD and motion state-weighted motion-compensation (MostMoCo) methods were applied to 18 lung MRI scans of pediatric and young adult patients. The data sets were acquired under free-breathing and without sedation with 3D radial UTE sequences in approximately 5 min. After reconstruction, they went through ventilation analyses. Performance across reconstruction regularization and motion-state parameters were also investigated.

RESULTS

The in vivo experiments results showed that MoCoLoR made efficient use of the data, provided higher apparent SNR compared with state-of-the-art XD reconstruction and MostMoCo reconstructions, and yielded high-quality respiratory phase-resolved images for ventilation mapping. The method was effective across the range of patients scanned.

CONCLUSION

The motion-compensated low-rank regularized reconstruction approach makes efficient use of acquired data and can improve simultaneous structural and functional lung imaging with 3D-UTE MRI. It enables the scanning of pediatric patients under free-breathing and without sedation.

MR imaging of the airways

The need for airway imaging is defined by the limited sensitivity of common clinical tests like spirometry, lung diffusion (DLCO) and blood gas analysis to early changes of peripheral airways and to inhomogeneous regional distribution of lung function deficits. Therefore, X-ray and computed tomography (CT) are frequently used to complement the standard tests.As an alternative, magnetic resonance imaging (MRI) offers radiation-free lung imaging, but at lower spatial resolution. Non-contrast enhanced MRI shows healthy airways down to the first subsegmental level/4^th order (CT: eighth). Bronchiectasis can be identified by wall thickening and fluid accumulation. Smaller airways become visible, when altered by peribronchiolar inflammation or mucus retention (tree-in-bud sign).The strength of MRI is functional imaging. Dynamic, time-resolved MRI directly visualizes expiratory airway collapse down to the lobar level (CT: segmental level). Obstruction of even smaller airways becomes visible as air trapping on the expiratory scans. MRI with hyperpolarized noble gases (³He, ¹²⁹Xe) directly shows the large airways and peripheral lung ventilation. Dynamic contrast-enhanced MRI (DCE MRI) indirectly shows airway dysfunction as perfusion deficits resulting from hypoxic vasoconstriction of the dependent lung volumes. Further promising scientific approaches such as non-contrast enhanced, ventilation-/perfusion-weighted MRI from periodic signal changes of respiration and blood flow are in development.In summary, MRI of the lungs and airways excels with its unique combination of morphologic and functional imaging capacities for research (e.g., in chronic obstructive lung disease or asthma) as well as for clinical imaging (e.g., in cystic fibrosis).

The Application and Value of 3T Magnetic Resonance Imaging in the Display of Pulmonary Nodules

Objective

The aim of this study was to evaluate the sensitivity and accuracy of multi-sequence 3T magnetic resonance imaging (MRI) in the detection of different types of pulmonary nodules.

Methods

A total of 68 patients with pulmonary nodules identified using computed tomography (CT) subsequently underwent MRI. Using CT images with a slice thickness of 1 mm as the gold standard, the sensitivity of three MRI sequences in detecting different types of pulmonary nodules was calculated, and the image quality was also evaluated. Nodule types included solid nodules, ground glass nodules (GGN), and part-solid nodules (PSN). Statistical analyses of data were conducted using the software SPSS 21.0. The intra-class correlation coefficient was calculated in order to compare the consistency of nodule size in both MRI and CT.

Results

CT detected 188 pulmonary nodules in 68 patients, including 87 solid nodules and 101 sub-solid nodules, the latter comprising 46 PSNs and 55 GGNs. The average nodule diameter was approximately 7.7 mm. The sensitivity of MRI in detecting nodules ≥ 6 mm in diameter and those of > 8 mm in diameter was 92% and 100%, respectively, and the sequence with the highest detection rate was T2-BLADE. In relation to solid nodules, the sequence with the highest detection rate was T1 Star-VIBE, while the T2-BLADE sequence demonstrated the highest detection rate of sub-solid nodules. The image quality of the T1 Star-VIBE sequence was better than that of both the T2-HASTE and the T2-BLADE sequences. The consistency of CT and MRI sequences for nodule size was high with a consistency coefficient of 0.94–0.98.

Conclusion

The detection rate of MRI for nodules with a diameter of > 8 mm was 100%. The T2-BLADE sequence had the highest detection sensitivity. The sequence with the best image quality was the T1 Star-VIBE.

Magnetic resonance imaging-guided microwave ablation for lung tumor: a case report

Thoracoscopic surgery is considered to be the best treatment option for pulmonary lesions. However, for patients with clinical stage IIIA, surgery is not always feasible, due to a lack of sufficient lung function. Microwave ablation (MWA) is an appropriate, minimally invasive treatment option for these patients. In this case study, we present our initial experience with MWA guided by magnetic resonance imaging (MRI), in a patient with a lesion located in the right lower lobe. The patient was successfully ablated and achieved a long progression-free period.

The use of chest magnetic resonance imaging in interstitial lung disease: a systematic review

Thin-slices multi-detector computed tomography (MDCT) plays a key role in the differential diagnosis of interstitial lung disease (ILD). However, thin-slices MDCT has a limited ability to detect active inflammation, which is an important target of newly developed ILD drug therapy. Magnetic resonance imaging (MRI), thanks to its multi-parameter capability, provides better tissue characterisation than thin-slices MDCT.Our aim was to summarise the current status of MRI applications in ILD and to propose an ILD-MRI protocol. A systematic literature search was conducted for relevant studies on chest MRI in patients with ILD.We retrieved 1246 papers of which 55 original papers were selected for the review. We identified 24 studies comparing image quality of thin-slices MDCT and MRI using several MRI sequences. These studies described new MRI sequences to assess ILD parenchymal abnormalities, such as honeycombing, reticulation and ground-glass opacity. Thin-slices MDCT remains superior to MRI for morphological imaging. However, recent studies with ultra-short echo-time MRI showed image quality comparable to thin-slices MDCT. Several studies demonstrated the added value of chest MRI by using functional imaging, especially to detect and quantify inflammatory changes.We concluded that chest MRI could play a role in ILD patients to differentiate inflammatory and fibrotic changes and to assess efficacy of new ILD drugs.

Signal enhancement ratio imaging of the lung parenchyma with ultra-fast steady-state free precession MRI at 1.5T

BACKGROUND

Lung perfusion MRI after i.v. gadolinium (Gd) contrast administration is commonly based on spoiled gradient-echo acquisitions, such as volume-interpolated breath-hold examinations (VIBE), suffering from low signal-to-noise in the parenchyma.

PURPOSE

To investigate the lung signal enhancement ratio (SER) with ultra-fast steady-state free precession (ufSSFP) after Gd-administration.

STUDY TYPE

Retrospective.

SUBJECTS

Ten subjects with healthy lungs; nine patients with pulmonary diseases (chronic obstructive pulmonary disease [COPD], lung cancer, pulmonary fibrosis, lung contusion).

FIELD STRENGTH/SEQUENCE

VIBE and ufSSFP imaging of the chest was performed at 1.5T before and 3 minutes after i.v. gadobenate dimeglumine.

ASSESSMENT

A workflow including deformable image registration and median filtering was used to compute 3D SER maps. SER was analyzed in the lung, blood pool, liver, muscles, and fat. The artifacts were assessed by a radiologist. In the COPD patients, ufSSFP-SER was compared to ^99m Tc-MAA-SPECT/CT by visual scoring of lung enhancement deficits.

STATISTICAL TESTS

Mean signal, standard deviation (SD), intersubject SD, and coefficient of variation (CV) were calculated for SER. Statistical significance of differences in signal and artifacts were determined using Wilcoxon signed-rank paired test. Intermodality agreement between ufSSFP-SER and SPECT/CT was calculated by Cohen's kappa (κ_q ).

RESULTS

In healthy lungs, ufSSFP-SER (99% ± 23%, mean ± pooled intrasubject SD, CV = 23%) was significantly higher (P < 10^-3 ) and more homogeneous (P < 10^-3 ) than VIBE (47% ± 26%, CV = 57%). UfSSFP-SER was significantly higher (P < 10^-3 ) for the lungs (99% ± 9%, mean ± intersubject SD) than for the blood (81% ± 7%) and other tissues (liver 33% ± 8%, muscle 26% ± 5%, fat 2% ± 1%). In the lung ufSSFP-SER exhibits homogeneity on iso-gravitational planes, and an anterior-posterior gradient. In COPD patients, ufSSFP-SER was reduced and less homogeneous compared to the control group (73% ± 33%, mean ± pooled intrasubject SD, CV = 42%). ufSSFP-SER had moderate intermodality agreement with SPECT/CT (κ_q  = 0.64).

DATA CONCLUSION

UfSSFP-SER of the lung is a rapid and simple method. Our preliminary data show plausible results in different pulmonary diseases, motivating further evaluation in larger cohorts.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018.

Development of a Computerized 4-D MRI Phantom for Liver Motion Study

Purpose:

To develop a 4-dimensional computerized magnetic resonance imaging phantom with image textures extracted from real patient scans for liver motion studies.

Methods:

The proposed phantom was developed based on the current version of 4-dimensional extended cardiac-torso computerized phantom and a clinical magnetic resonance scan. Initially, the extended cardiac-torso phantom was voxelized in abdominal–chest region at the end of exhalation phase. Structures/tissues were classified into 4 categories: (1) Seven key textured organs, including liver, gallbladder, spleen, stomach, heart, kidneys, and pancreas, were mapped from a clinical T1-weighted liver magnetic resonance scan using deformable registration. (2) Large textured soft tissue volumes were simulated via an iterative pattern generation method using the same magnetic resonance scan. (3) Lung and intestine structures were generated by assigning uniform intensity with proper noise modeling. (4) Bony structures were generated by assigning the magnetic resonance values. A spherical hypointensity tumor was inserted into the liver. Other respiratory phases of the 4-dimensional phantom were generated using the backward deformation vector fields exported by the extended cardiac-torso program, except that bony structures were generated separately for each phase. A weighted image filtering process was utilized to improve the overall tissue smoothness at each phase.

Results:

Three 4-dimensional series with different motion amplitudes were generated. The developed motion phantom produced good illustrations of abdominal–chest region with anatomical structures in key organs and texture patterns in large soft tissue volumes. In a standard series, the tumor volume was measured as 13.90 ± 0.11 cm³ in a respiratory cycle and the tumor’s maximum center-of-mass shift was 2.95 cm/1.84 cm on superior–inferior/anterior–posterior directions. The organ motion during the respiratory cycle was well rendered. The developed motion phantom has the flexibility of motion pattern variation, organ geometry variation, and tumor modeling variation.

Conclusions:

A 4-D computerized phantom was developed and could be used to produce image series with synthetic magnetic resonance textures for magnetic resonance imaging research of liver motion.

Thoracic MRI evaluation of sarcoidosis in children

BACKGROUND

Childhood sarcoidosis is a very rare granulomatous disorder with an unknown etiology. Stage 1 disease is the most common whereas stages 2, 3, and 0 are rare in children.

OBJECTIVE

To evaluate thoracic findings of pediatric pulmonary sarcoidosis on MRI and to compare them with CT findings.

METHODS

Between August 2010 and May 2015, seven consecutive pediatric patients (four male, three female; age range: 8-18 years, mean age: 13.5 ± 3.01 years) who were diagnosed with sarcoidosis were enrolled in our study prospectively. Inclusion criterion was patients with stages 1-4 sarcoidosis who underwent contrast enhanced chest CT for initial diagnosis or follow-up evaluation of thoracic findings and exclusion criteria were patients with stage 0 disease with extra-pulmonary manifestations (n = 4).

RESULTS

Two patients who recovered from stage 2 to stage 0 were interpreted as normal. Five patients had abnormal findings on chest CT, including hilar/mediastinal lymphadenopathy (n = 5, 71%), nodules larger than 3 mm (n = 4, 57%), ground glass opacity (n = 4, 57%), thickening of the pleura/fissure (n = 3, 42%), interlobular septal thickening (n = 2, 28%), atelectasis (n = 1, 14%), consolidation (n = 1, 14%), bronchiectasis (n = 1, 14%), intraparenchymal and subpleural cysts (n = 1,14%), fibrotic bands (n = 1, 14%), and enlarged pulmonary artery (n = 1, 14%). Findings that were detected on CT but not observed by lung MRI were nodules <3 mm (n = 4, 57%), mild bronchiectasis and mild ground glass opacity (n = 1, 14%), and subpleural and intraparenchymal cysts (n = 1, 14%). The sensitivity and specificity of MRI were 85.2% and 100%, respectively. There was no statistically significant difference between lung MRI and CT in detecting the thoracic findings in stages 1, 2, and 4 sarcoidosis (P = 0.1336, 95%Cl).

CONCLUSION

Contrast-enhanced lung MRI with fast imaging sequences is a highly sensitive imaging modality and comparable with CT in evaluating both lung and cardiac abnormalities in pediatric sarcoidosis. Given there is no associated ionizing radiation, chest MRI is a promising imaging modality in this pediatric patient population. Pediatr Pulmonol. 2017;52:494-499. © 2016 Wiley Periodicals, Inc.

Proton Magnetic Resonance Imaging for Initial Assessment of Isolated Mycobacterium avium Complex Pneumonia

RATIONALE

Computed tomographic (CT) radiography is the reference standard for imaging Mycobacterium avium complex (MAC) lung infection. Magnetic resonance imaging (MRI) has been shown to be comparable to CT for characterizing other pulmonary inflammatory conditions, but has not been rigorously tested for imaging MAC pneumonia.

OBJECTIVES

To determine the feasibility of pulmonary MRI for imaging MAC pneumonia and to assess the degree of agreement between MRI and CT for assessing the anatomic features and lobar extent of MAC lung infections.

METHODS

Twenty-five subjects with culture-confirmed MAC pneumonia and no identified coinfecting organisms were evaluated by thoracic MRI and then by chest CT imaging performed up to 1 week later. After deidentification, first the MRI and then the CT scans were scored 2 weeks apart by two chest radiologists working independently of one another. Discrepancies were resolved by a third chest radiologist. The scans were scored for bronchiectasis, consolidation or atelectasis, abscess or sacculation, nodules, and mucus plugging using a three-point lobar scale (absent, <50% of lobe, and >50% of lobe). Agreement analyses and ordinary least products regressions were performed.

MEASUREMENTS AND MAIN RESULTS

A fixed bias was found between total CT and MRI scores, with CT scoring higher on average (median difference: 4 on a scale of 48; interquartile range: 3, 6). Fixed biases were found for bronchiectasis and consolidation or atelectasis subscale scores. Both fixed and proportional biases were found between CT and MRI mucus plugging scores. No bias was found between CT and MRI nodule scores. There was nearly perfect lobar percent agreement for more conspicuous findings such as consolidation or atelectasis and abscess or sacculation.

CONCLUSIONS

In this exploratory study of 25 adult patients with culture-proven MAC lung infection, we found moderate agreement between MRI and CT for assessing the anatomic features and lobar extent of disease. Given the feasibility of chest MRI for this condition, future work is warranted to assess the clinical impact of MRI compared with CT in assessing progression of untreated MAC infection and response to treatment over time.

Rapid 3D imaging of the lower airway by MRI in patients with congenital heart disease: A retrospective comparison of delayed volume interpolated breath-hold examination (VIBE) to turbo spin echo (TSE)

OBJECTIVE

When imaging the lower airway by MRI, the traditional technique turbo spin echo (TSE) results in high quality 2D images, however planning and acquisition times are lengthy. An alternative, delayed volume interpolated breath-holds examination (VIBE), is a 3D gradient echo technique that produces high spatial resolution imaging of the airway in one breath-hold. The objective of this study is to retrospectively evaluate the accuracy of lower airway measurements obtained by delayed VIBE when compared to TSE.

DESIGN

Patients with congenital heart disease who underwent a cardiac MRI (CMR) that included a delayed VIBE sequence from 5/2008 to 9/2013 were included. Standard TSE imaging was performed and delayed VIBE was acquired 5 min after gadolinium contrast administration. Airway measurements were made on both sequences by two observers in a blinded fashion to the other observer and other technique. Intraclass correlations (ICC) were calculated to assess for agreement between both techniques and the observers.

RESULTS

29 studies met inclusion criteria with a mean patient age of 8.8 years (2 months to 63 years) and mean patient weight of 30.2 kg (3.5-110). All delayed VIBE and TSE sequences were found to be of diagnostic quality. Mean acquisition time was shorter for the delayed VIBE (13.1 seconds) than TSE (949.9 seconds). Overall there was very good agreement between the delayed VIBE and TSE measurements for both observers (ICC 0.78-0.94) with the exception of the distal right bronchus (ICC 0.67) The interobserver agreement was also excellent for both TSE (ICC 0.78-0.96) and VIBE (ICC 0.85-0.96).

CONCLUSION

Delayed VIBE is rapid and at least as accurate as the alternative TSE imaging for assessment of the lower airway by MRI across a wide spectrum of patients.

Magnetic resonance imaging in lung: a review of its potential for radiotherapy

MRI has superior soft-tissue definition compared with existing imaging modalities in radiation oncology; this has the added benefit of functional as well as anatomical imaging. This review aimed to evaluate the current use of MRI for lung cancer and identify the potential of a MRI protocol for lung radiotherapy (RT). 30 relevant studies were identified. Improvements in MRI technology have overcome some of the initial limitations of utilizing MRI for lung imaging. A number of commercially available and novel sequences have shown image quality to be adequate for the detection of pulmonary nodules with the potential for tumour delineation. Quantifying tumour motion is also feasible and may be more representative than that seen on four-dimensional CT. Functional MRI sequences have shown correlation with flu-deoxy-glucose positron emission tomography (FDG-PET) in identifying malignant involvement and treatment response. MRI can also be used as a measure of pulmonary function. While there are some limitations for the adoption of MRI in RT-planning process for lung cancer, MRI has shown the potential to compete with both CT and PET for tumour delineation and motion definition, with the added benefit of functional information. MRI is well placed to become a significant imaging modality in RT for lung cancer.

Quiet Submillimeter MR Imaging of the Lung Is Feasible with a PETRA Sequence at 1.5 T

PURPOSE

To assess lung magnetic resonance (MR) imaging with a respiratory-gated pointwise encoding time reduction with radial acquisition (PETRA) sequence at 1.5 T and compare it with imaging with a standard volumetric interpolated breath-hold examination (VIBE) sequence, with extra focus on the visibility of bronchi and the signal intensity of lung parenchyma.

MATERIALS AND METHODS

The study was approved by the local ethics committee, and all subjects gave written informed consent. Twelve healthy volunteers were imaged with PETRA and VIBE sequences. Image quality was evaluated by using visual scoring, numbering of visible bronchi, and quantitative measurement of the apparent contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR). For preliminary clinical assessment, three young patients with cystic fibrosis underwent both MR imaging and computed tomography (CT). Comparisons were made by using the Wilcoxon signed-rank test for means and the McNemar test for ratios. Agreement between CT and MR imaging disease scores was assessed by using the κ test.

RESULTS

PETRA imaging was performed with a voxel size of 0.86 mm(3). Overall image quality was good, with little motion artifact. Bronchi were visible consistently up to the fourth generation and in some cases up to the sixth generation. Mean CNR and SNR with PETRA were 32.4% ± 7.6 (standard deviation) and 322.2% ± 37.9, respectively, higher than those with VIBE (P < .001). Good agreement was found between CT and PETRA cystic fibrosis scores (κ = 1.0).

CONCLUSION

PETRA enables silent, free-breathing, isotropic, and submillimeter imaging of the bronchi and lung parenchyma with high CNR and SNR and may be an alternative to CT for patients with cystic fibrosis.

Regional ventilation changes in severe asthma after bronchial thermoplasty with (3)He MR imaging and CT

PURPOSE

To quantify regional lung ventilation in healthy volunteers and patients with severe asthma (both before and after thermoplasty) by using a combination of helium 3 ((3)He) magnetic resonance (MR) imaging and computed tomography (CT), with the intention of developing more effective image-guided treatments for obstructive lung diseases.

MATERIALS AND METHODS

With approval of the local institutional review board, informed consent, and an Investigational New Drug Exemption, six healthy volunteers and 10 patients with severe asthma were imaged in compliance with HIPAA regulations by using both multidetector CT and (3)He MR imaging. Individual bronchopulmonary segments were labeled voxel by voxel from the CT images and then registered to the (3)He MR images by using custom software. The (3)He signal intensity was then analyzed by evaluating the volume-weighted fraction of total-lung signal intensity present in each segment (segmental ventilation percentage [ SVP segmental ventilation percentage ]) and by identifying the whole-lung defect percentage and the segmental defect percentage. Of the 10 patients with asthma, seven received treatment with bronchial thermoplasty and were imaged with (3)He MR a second time. Changes in segmental defect percentages and whole-lung defect percentages are presented.

RESULTS

Ventilation measures for healthy volunteers yielded smaller segment-to-segment variation (mean SVP segmental ventilation percentage , 100% ± 18 [standard deviation]) than did the measures for patients with severe asthma (mean SVP segmental ventilation percentage , 97% ± 23). Patients with asthma also demonstrated larger segmental defect percentages (median, 13.5%; interquartile range, 8.9%-17.8%) than healthy volunteers (median, 6%; interquartile range, 5.6%-6.3%). These quantitative results confirm what is visually observed on the (3)He images. A Spearman correlation of r = -0.82 was found between the change in whole-lung defect percentage and the number of days between final treatment and second (3)He imaging.

CONCLUSION

Regional quantification of lung ventilation is indeed feasible and may be a useful technique for image-guided treatment of obstructive lung diseases, such as bronchial thermoplasty for severe asthma. In these patients, ventilation defects decreased as a function of time after treatment.

Phase-contrast X-ray CT imaging of esophagus and esophageal carcinoma

The electron density resolution is 1000 times higher for synchrotron-radiation phase-contrast CT imaging than conventional X-ray absorption imaging in light elements, with which high-resolution X-ray imaging of biological soft tissue can be achieved. In the present study, we used phase-contrast X-ray CT to investigate human resected esophagus and esophageal carcinoma specimens. This technology revealed the three-layer structure of the esophageal wall-- mucous, submucosa and muscular layers. The mucous and muscular layers were clearly separated by a loose submucosa layer with a honeycomb appearance. The surface of the mucous layer was smooth. In esophageal carcinoma, because of tumor tissue infiltration, the submucosa layer was absent, which indicated destruction of the submucosa. The boundary between normal tissue and tumor was comparatively fuzzy, the three-layer structure of the esophageal wall was indistinct. The surface of the mucous layer was rugose. The technology might be helpful in tumor staging of esophageal carcinoma.

Diagnostic accuracy of MRI-guided percutaneous transthoracic needle biopsy of solitary pulmonary nodules

OBJECTIVE

The purpose of our study was to evaluate the diagnostic accuracy of MRI-guided percutaneous transthoracic needle biopsy (PTNB) of solitary pulmonary nodules (SPNs).

METHODS

Retrospective review of 69 patients who underwent MR-guided PTNB of SPNs was performed. Each case was reviewed for complications. The final diagnosis was established by surgical pathology of the nodule or clinical and imaging follow-up. Pneumothorax rate and diagnostic accuracy were compared between two groups according to nodule diameter (≤2 vs. >2 cm) using χ (2) chest and Fisher's exact test, respectively.

RESULTS

The success rate of single puncture was 95.6 %. Twelve (17.4 %) patients had pneumothorax, with 1 (1.4 %) requiring chest tube insertion. Mild hemoptysis occurred in 7 (7.2 %) patients. All of the sample material was sufficient for histological diagnostic evaluation. Pathological analysis of biopsy specimens showed 46 malignant, 22 benign, and 1 nondiagnostic nodule. The final diagnoses were 49 malignant nodules and 20 benign nodules basing on postoperative histopathology and clinical follow-up data. One nondiagnostic sample was excluded from calculating diagnostic performance. A sensitivity, specificity, accuracy, positive predictive value, and negative predictive value in diagnosing SPNs were 95.8, 100, 97.0, 100, and 90.9 %, respectively. Pneumothorax rate, diagnostic sensitivity, and accuracy were not significantly different between the two groups (P > 0.05).

CONCLUSIONS

MRI-guided PTNB is safe, feasible, and high accurate diagnostic technique for pathologic diagnosis of pulmonary nodules.

Lung morphology assessment with balanced steady-state free precession MR imaging compared with CT

PURPOSE

To evaluate the utility of 1.5-T noncontrast magnetic resonance (MR) imaging of the lung parenchyma and to compare it with computed tomography (CT) in the assessment of interstitial lung disease and other morphologic lung abnormalities.

MATERIALS AND METHODS

Institutional review board approval was obtained for retrospective image analysis. A total of 236 patients who underwent MR imaging and CT as part of their assessment for suspected pulmonary hypertension were included in this study. Lung MR imaging was performed with a 1.5-T system as a stack of axial two-dimensional balanced steady-state free precession (bSSFP) acquisitions. Two radiologists independently evaluated CT and MR images for various morphologic abnormalities, such as pulmonary fibrosis, pleural and mediastinal disease, solid lesions, bronchial disease, and emphysema. Κ statistics were used to measure interobserver agreement.

RESULTS

Sensitivity and specificity of MR imaging in the identification of pulmonary fibrosis (n = 46) were 89% (95% confidence interval: 77%, 96%) and 91% (95% confidence interval: 76%, 98%), respectively, when compared with CT. In comparison to CT, MR imaging depicted 75% of ground-glass opacities. Nine of the 12 noncalcified nodules were identified on MR images. Lung nodules (75%, κ = 0.71) and effusions (100%, κ = 0.89) were also well visualized on MR images. MR imaging was however less effective in depicting emphysema (16%, κ = 0.60) and minor fibrosis (67%, κ = 0.79).

CONCLUSION

This study shows bSSFP MR imaging is inferior to CT in imaging parenchymal lung disease; however, this study does demonstrate for the first time a potential role for the bSSFP sequence as an alternative radiation-free noncontrast imaging modality for use in patients with pulmonary fibrosis.

MRI of the lung (2/3). Why … when … how?

BACKGROUND

Among the modalities for lung imaging, proton magnetic resonance imaging (MRI) has been the latest to be introduced into clinical practice. Its value to replace X-ray and computed tomography (CT) when radiation exposure or iodinated contrast material is contra-indicated is well acknowledged: i.e. for paediatric patients and pregnant women or for scientific use. One of the reasons why MRI of the lung is still rarely used, except in a few centres, is the lack of consistent protocols customised to clinical needs.

METHODS

This article makes non-vendor-specific protocol suggestions for general use with state-of-the-art MRI scanners, based on the available literature and a consensus discussion within a panel of experts experienced in lung MRI.

RESULTS

Various sequences have been successfully tested within scientific or clinical environments. MRI of the lung with appropriate combinations of these sequences comprises morphological and functional imaging aspects in a single examination. It serves in difficult clinical problems encountered in daily routine, such as assessment of the mediastinum and chest wall, and even might challenge molecular imaging techniques in the near future.

CONCLUSION

This article helps new users to implement appropriate protocols on their own MRI platforms. Main Messages • MRI of the lung can be readily performed on state-of-the-art 1.5-T MRI scanners. • Protocol suggestions based on the available literature facilitate its use for routine • MRI offers solutions for complicated thoracic masses with atelectasis and chest wall invasion. • MRI is an option for paediatrics and science when CT is contra-indicated.

MRI of the lung (3/3)-current applications and future perspectives

Background

MRI of the lung is recommended in a number of clinical indications. Having a non-radiation alternative is particularly attractive in children and young subjects, or pregnant women.

Methods

Provided there is sufficient expertise, magnetic resonance imaging (MRI) may be considered as the preferential modality in specific clinical conditions such as cystic fibrosis and acute pulmonary embolism, since additional functional information on respiratory mechanics and regional lung perfusion is provided. In other cases, such as tumours and pneumonia in children, lung MRI may be considered an alternative or adjunct to other modalities with at least similar diagnostic value.

Results

In interstitial lung disease, the clinical utility of MRI remains to be proven, but it could provide additional information that will be beneficial in research, or at some stage in clinical practice. Customised protocols for chest imaging combine fast breath-hold acquisitions from a “buffet” of sequences. Having introduced details of imaging protocols in previous articles, the aim of this manuscript is to discuss the advantages and limitations of lung MRI in current clinical practice.

Conclusion

New developments and future perspectives such as motion-compensated imaging with self-navigated sequences or fast Fourier decomposition MRI for non-contrast enhanced ventilation- and perfusion-weighted imaging of the lung are discussed.

Main Messages

• MRI evolves as a third lung imaging modality, combining morphological and functional information.

• It may be considered first choice in cystic fibrosis and pulmonary embolism of young and pregnant patients.

• In other cases (tumours, pneumonia in children), it is an alternative or adjunct to X-ray and CT.

• In interstitial lung disease, it serves for research, but the clinical value remains to be proven.

• New users are advised to make themselves familiar with the particular advantages and limitations.

Diffusion-weighted MR-imaging for the detection of pulmonary nodules at 1.5 Tesla: intraindividual comparison with multidetector computed tomography

INTRODUCTION

To investigate the feasibility of diffusion-weighted imaging (DWI) MRI for detecting pulmonary nodules at 1.5 Tesla in comparison with standard multidetector computed tomography (MDCT).

METHODS

Twenty patients with disseminated cancer disease in which MDCT had assured the presence of at least one pulmonary nodule were examined using a respiratory-gated DWI MR-sequence. Grey scale inverted source images and coronal maximum intensity projection (MIP) images were consensually analysed by two experienced radiologists. Size and location of any nodule detected were assessed. Additionally, the readers evaluated each hemithorax for the presence of at least one nodule and applied a four-point conspicuity scale (1-hemithorax definitely affected; 4-hemithorax definitely not affected). MDCT data served as reference.

RESULTS

At MDCT, a total of 71 pulmonary noduIes was found (size 3-5mm, n=16; 6-9mm, n=22; ≥10mm, n=33). For the DWI MR-sequence, a sensitivity of 86.4% was calculated for nodules ranging 6-9mm and 97% for nodules ≥10mm. In contrast, only 43.8% of lesions ≤5mm was detected. The separate analysis of each hemithorax for the presence of at least one pulmonary nodule revealed a specificity rate, PPV and NPV of DWI-MR of 92.3%, 96% and 80%, respectively.

CONCLUSIONS

The presented study is the first to confirm the diagnostic potential of DWI-MR in the detection of solid lung nodules. This technique allows for the detection of nodules ≥6mm with reasonably high sensitivity rates (>86%). The observation of false positive findings decreases the accuracy of this approach compared with MDCT.

Micro soft tissues visualization based on x-ray phase-contrast imaging

The current imaging methods have a limited ability to visualize microstructures of biological soft tissues. Small lesions cannot be detected at the early stage of the disease. Phase contrast imaging (PCI) is a novel non-invasive imaging technique that can provide high contrast images of soft tissues by the use of X-ray phase shift. It is a new choice in terms of non-invasively revealing soft tissue details. In this study, the lung and hepatic fibrosis models of mice and rats were used to investigate the ability of PCI in microstructures observation of soft tissues. Our results demonstrated that different liver fibrosis stages could be distinguished non-invasively by PCI. The three-dimensional morphology of a segment of blood vessel was constructed. Noteworthy, the blood clot inside the vessel was visualized in three dimensions which provided a precise description of vessel stenosis. Furthermore, the whole lung airways including the alveoli were obtained. We had specifically highlighted its use in the visualization and assessment of the alveoli. To our knowledge, this was the first time for non-invasive alveoli imaging using PCI. This finding may offer a new perspective on the diagnosis of respiratory disease. All the results confirmed that PCI will be a valuable tool in biological soft tissues imaging.

The role of imaging techniques in the assessment of pulmonary circulation

Knowledge of the structure and function of pulmonary circulation has evolved considerably in the last few decades. The use of non-invasive imaging techniques to assess the anatomy and function of the pulmonary vessels and heart has taken on added importance with the recent advent of novel therapies. Imaging findings not only constitute a diagnostic tool but have also proven to be essential for prognosis and treatment follow-up. This article reviews the myriad of imaging methods currently available for the assessment of pulmonary circulation, from the simple chest X-ray to techniques that are more complex and promising, such as electrical impedance tomography.

Computed tomography and magnetic resonance imaging of pulmonary hypertension: Pulmonary vessels and right ventricle

Pulmonary hypertension (PH) is very heterogeneous and the classification identifies five major groups including many associated disease processes. The treatment of PH depends on the underlying cause and accurate classification is paramount. A comprehensive assessment to identify the cause and severity of PH is therefore needed. Furthermore, follow-up assessments are required to monitor changes in disease status and response to therapy. Traditionally, the diagnostic imaging work-up of PH comprised mainly echocardiography, invasive right heart catheterization, and ventilation/perfusion scintigraphy. Due to technical advances, multidetector row computed tomography (CT) and magnetic resonance imaging (MRI) have become important and complementary investigations in the evaluation of patients with suspected PH. Both modalities are reviewed and recommendations for clinical use are given.

Non-invasive microstructure and morphology investigation of the mouse lung: qualitative description and quantitative measurement

BACKGROUND

Early detection of lung cancer is known to improve the chances of successful treatment. However, lungs are soft tissues with complex three-dimensional configuration. Conventional X-ray imaging is based purely on absorption resulting in very low contrast when imaging soft tissues without contrast agents. It is difficult to obtain adequate information of lung lesions from conventional X-ray imaging.

METHODS

In this study, a recently emerged imaging technique, in-line X-ray phase contrast imaging (IL-XPCI) was used. This powerful technique enabled high-resolution investigations of soft tissues without contrast agents. We applied IL-XPCI to observe the lungs in an intact mouse for the purpose of defining quantitatively the micro-structures in lung.

FINDINGS

The three-dimensional model of the lung was successfully established, which provided an excellent view of lung airways. We highlighted the use of IL-XPCI in the visualization and assessment of alveoli which had rarely been studied in three dimensions (3D). The precise view of individual alveolus was achieved. The morphological parameters, such as diameter and alveolar surface area were measured. These parameters were of great importance in the diagnosis of diseases related to alveolus and alveolar scar.

CONCLUSION

Our results indicated that IL-XPCI had the ability to represent complex anatomical structures in lung. This offered a new perspective on the diagnosis of respiratory disease and may guide future work in the study of respiratory mechanism on the alveoli level.

Lung morphology assessment using MRI: a robust ultra-short TR/TE 2D steady state free precession sequence used in cystic fibrosis patients

To evaluate feasibility and diagnostic quality of ultra-short TR/TE two-dimensional (2D) steady state free precession (SSFP) MRI for cystic fibrosis (CF) patients. We performed lung MRI at 1.5 Tesla in 20 CF-patients (6-17 years, 12 males). Axial, coronal, and sagittal sections were acquired in inspiration and expiration with maximum breath-hold time 10 s. MR and CT images were scored using a modified Brody scoring system to assess bronchiectasis, mucous plugging, atelectasis/consolidations, and air trapping. All images were scored by two experienced observers. A complete MR investigation took maximally 15 min. Maximal breath-holds were only 10 s and well tolerated. MRI identified major bronchiectasis, mucous plugging and atelectasis. End-expiratory scans showed patches of parenchyma with reduced signal intensity that may corresponded to areas of trapped air on expiratory CT scans. This MRI protocol based on ultra-short TR/TE 2D SSFP is quick and well tolerated and provides highly relevant imaging features as seen on CT in CF patients. Most importantly, the SNR of the expiratory scans enables to visualize air trapping. The preliminary results of this study suggest MRI as a noteworthy additional imaging tool for routine monitoring of CF patients.

Detection of pulmonary nodules with move-during-scan magnetic resonance imaging using a free-breathing turbo inversion recovery magnitude sequence

PURPOSE

Detection of pulmonary metastases is still a challenging task for magnetic resonance imaging (MRI). It was the aim of this study to evaluate the potential of a free-breathing move-during-scan turbo inversion recovery magnitude sequence for the detection of pulmonary nodules.

MATERIALS AND METHODS

The sensitivities and positive-predictive values of 2 radiologists to detect pulmonary nodules in 41 move-during-scan MRI examinations of 38 patients with different malignancies were calculated and subgroup analyses according to lesion size and localization were performed. Multidetector computed tomography served as the standard of reference. Additionally, 6 radiologists rated the confidence for the presence of nodular lesions in 212 regions-of-interest, which were randomly selected to represent lesions of various sizes as well as negative findings. Receiver-operator-characteristic was performed.

RESULTS

Three hundred twenty-one nodules were found in 30 patients by multidetector computed tomography. Sensitivity and specificity of MRI to detect pulmonary nodules larger than 3 mm on a per-patient basis were 81.8% and 94.7%, respectively. On a per-lesion basis, MRI revealed a sensitivity of 79.0% to 80.7% for lesions larger than 3 mm, if high conspicuity ratings were counted as positive, and 84.6%, if medium and high conspicuity ratings were counted as positive. Sensitivity increased uniformly with lesion size, and all lesions larger than 12 mm were detected. Receiver-operator-characteristic analysis revealed a mean accuracy of 0.90 and sensitivities over 90% for lesions larger than 3 mm with a specificity of 96.1%. For lesions larger than 6 mm the accuracy was 0.99.

CONCLUSION

Detection of pulmonary nodules with a move-during-scan turbo inversion recovery magnitude sequence is feasible. Excellent detection of lesions larger than 6 mm is achievable with free-breathing moving-table MRI.

MR for the evaluation of obstructive pulmonary disease

Obstructive lung diseases include emphysema, chronic bronchitis, chronic obstructive pulmonary disease, asthma, and cystic fibrosis. These diseases are a heterogeneous group of pulmonary disorders that share in common obstruction of air flow and deranged gas exchange. Traditionally these diseases are evaluated with clinical testing, such as pulmonary function tests, but such tests provide only global measures of respiratory function. MR techniques designed for obstructive lung disease have the capability of directly imaging the anatomic and pathophysiologic derangements and may prove useful for monitoring response to therapy.

MR imaging of the chest: A practical approach at 1.5T

Magnetic resonance imaging (MRI) is capable of imaging infiltrative lung diseases as well as solid lung pathologies with high sensitivity. The broad use of lung MRI was limited by the long study time as well as its sensitivity to motion and susceptibility artifacts. These disadvantages were overcome by the utilisation of new techniques such as parallel imaging. This article aims to propose a standard MR imaging protocol at 1.5T and presents a spectrum of indications. The standard protocol comprises non-contrast-enhanced sequences. Following a GRE localizer (2D-FLASH), a coronal T2w single-shot half-Fourier TSE (HASTE) sequence with a high sensitivity for infiltrates and a transversal T1w 3D-GRE (VIBE) sequence with a high sensitivity for small lesions are acquired in a single breath hold. Afterwards, a coronal steady-state free precession sequence (TrueFISP) in free breathing is obtained. This sequence has a high sensitivity for central pulmonary embolism. Distinct cardiac dysfunctions as well as an impairment of the breathing mechanism are visible. The last step of the basic protocol is a transversal T2w-STIR (T2-TIRM) in a multi-breath holds technique to visualize enlarged lymph nodes as well as skeletal lesions. The in-room time is approximately 15min. The extended protocol comprises contrast-enhanced sequences (3D-GRE sequence (VIBE) after contrast media; about five additional minutes). Indications are tumorous lesions, unclear (malignant) pleural effusions and inflammatory diseases (vaskulitis). A perfusion analysis can be achieved using a 3D-GRE in shared echo-technique (TREAT) with a high temporal resolution. This protocol can be completed using a MR-angiography (3D-FLASH) with high spatial resolution. The in-room time for the complete protocol is approximately 30min.

Optimal breathing protocol for dynamic contrast-enhanced MRI of solitary pulmonary nodules at 3T

The purpose of this study was to evaluate optimal breathing maneuvers that minimize lung parenchymal movement for dynamic contrast-enhanced MRI (DCE-MRI), which requires longer scan times, beyond the limit of a single breath hold. A healthy volunteer was scanned on a 3T MR scanner using two different breathing maneuvers. In the first, the healthy volunteer was instructed to hold his breath as much as possible and breathe in between breath holds while an image was obtained. In the second, the volunteer was instructed to breathe shallowly and freely throughout the scan. On the obtained images, the excursion of the highest point of the right diaphragm and the pulmonary vessel branches located in the four different anatomic regions of the lung were measured in two orthogonal planes. A patient with a solitary pulmonary nodule (SPN) underwent DCE-MRI utilizing a 2D spoiled gradient-echo (SPGR) sequence while the patient breathed shallowly and freely during the scan. The standard deviations of the excursion of the highest point and selected pulmonary vessels were much smaller during shallow, free breathing maneuver scans than those during breath hold maneuver scans. A dynamic perfusion-fitting curve of the SPN was obtained during the DCE-MRI using shallow free breathing. Shallow, free breathing allows smaller diaphragmatic cranial caudal and lung parenchymal displacements. Therefore, it can be useful during exams where targeting of the lesion is necessary, in studies with long scan times, such as dynamic MRI. This breathing maneuver makes it possible to analyze SPN with DCE-MRI while making use of the advantages of a higher magnetic field in conjunction.

Morphological and functional imaging in COPD with CT and MRI: present and future

Chronic obstructive pulmonary disease (COPD) is one of the leading causes of morbidity and mortality worldwide. COPD is defined by irreversible airflow obstruction. It is a heterogeneous disease affecting the airways (i.e. chronic bronchitis, airway collapse), the parenchyma (i.e. hyperinflation, air trapping and emphysematous destruction) as well as the vasculature (i.e. hypoxic vasoconstriction, rarefication and pulmonary arterial hypertension) with different severity during the course of the disease. These different aspects of COPD can be best addressed by imaging using a combination of morphological and functional techniques. Three-dimensional high-resolution computed tomography (3D-HRCT) is the technique of choice for morphological imaging of the lung parenchyma and airways. This morphological information is to be accomplished by functional information about perfusion, regional lung mechanics, and ventilation mainly provided by MRI. The comprehensive diagnostic possibilities of CT complemented by MRI will allow for a more sensitive detection, phenotype-driven characterization and dedicated therapy monitoring of COPD as presented in this review.

Lung MRI at 1.5 and 3 Tesla

OBJECTIVES

To compare the image quality and lesion contrast of lung MRI using 5 different pulse sequences at 1.5 T and 3 T.

MATERIALS AND METHODS

Lung MRI was performed at 1.5 T and 3 T using 5 pulse sequences which have been previously proposed for lung MRI: 3D volumetric interpolated breath-hold examination (VIBE), true fast imaging with steady-state precession (TrueFISP), half-Fourier single-shot turbo spin-echo (HASTE), short tau inversion recovery (STIR), T2-weighted turbo spin-echo (TSE). In addition to 4 healthy volunteers, 5 porcine lungs were examined in a dedicated chest phantom. Lung pathology (nodules and infiltrates) was simulated in the phantom by intrapulmonary and intrabronchial injections of agarose. CT was performed in the phantom for correlation. Image quality of the sequences was ranked in a side-by-side comparison by 3 blinded radiologists regarding the delineation of pulmonary and mediastinal anatomy, conspicuity of pulmonary nodules and infiltrates, and presence of artifacts. The contrast of nodules and infiltrates (CNODULES and CINFILTRATES) defined by the ratio of the signal intensities of the lesion and adjacent normal lung parenchyma was determined.

RESULTS

There were no relevant differences regarding the preference for the individual sequences between both field strengths. TSE was the preferred sequence for the visualization of the mediastinum at both field strengths. For the visualization of lung parenchyma the observers preferred TrueFISP in volunteers and TSE in the phantom studies. At both field strengths VIBE achieved the best rating for the depiction of nodules, whereas HASTE was rated best for the delineation of infiltrates. TrueFISP had the fewest artifacts in volunteers, whereas STIR showed the fewest artifacts in the phantom. For all but the TrueFISP sequence the lesion contrast increased from 1.5 T to 3 T. At both field strengths VIBE showed the highest CNODULES (6.6 and 7.1) and HASTE the highest CINFILTRATES (6.1 and 6.3).

CONCLUSION

The imaging characteristics of different pulse sequences used for lung MRI do not substantially differ between 1.5 T and 3 T. A higher lesion contrast can be expected at 3 T.

MRI of the lung: Value of different turbo spin-echo, single-shot turbo spin-echo, and 3D gradient-echo pulse sequences for the detection of pulmonary metastases

PURPOSE

To compare the value of different MRI sequences of the lung for the detection of pulmonary metastases.

MATERIALS AND METHODS

A total of 28 patients with 225 pulmonary metastases confirmed at multidetector-row computed tomography (MDCT) underwent MRI of the lung, including breathhold T2-weighted single-shot turbo spin-echo (half-Fourier single-shot turbo spin-echo [HASTE] and inversion recovery [IR]-HASTE) and conventional turbo spin-echo (TSE and short-tau inversion recovery [STIR]) sequences, a respiratory- and pulse-triggered black-blood STIR sequence (triggered STIR), and breathhold pre- and postcontrast volumetric interpolated 3D gradient-echo (VIBE) sequences. MR images were reviewed by three independent observers and results were correlated with MDCT, which served as standard of reference. Lesion-to-lung contrast-to-noise ratios (CNRs) and image artifacts were also assessed.

RESULTS

CNRs were highest on TSE images (P < 0.001). Mean sensitivities for lesion detection with triggered STIR, TSE, and STIR were 72.0%, 69.0%, and 63.4%, respectively. With HASTE, IR-HASTE, and pre- and postcontrast VIBE, significantly lower sensitivities were obtained (P < 0.05), although artifacts due to physiological motion were less distinct with these sequences compared to TSE and STIR (P < 0.05).

CONCLUSION

Conventional TSE sequences are more sensitive in depicting pulmonary metastases than single-shot TSE or 3D gradient-echo sequences. Respiratory and pulse triggering can improve lesion detection, but increases acquisition time substantially.

Preoperative assessment and follow-up of congenital abnormalities of the pulmonary arteries using CT and MRI

Congenital heart disease (CHD), including complex anomalies of the pulmonary arteries, are now earlier diagnosed and treated. Due to improvements in interventional and surgical therapy, the number of patients with the need for follow-up examinations is increasing. Pre- and postinterventional imaging should be done as gently as possible, avoiding invasive techniques if possible. With the technical improvement of multidetector-row computed tomography (MDCT) and magnetic resonance imaging (MRI), both techniques are increasingly used for noninvasive assessment of the pulmonary vasculature in children with CHD. Knowledge of the most common diseases affecting the pulmonary vasculature and the kind of surgical and interventional procedures is essential for optimal imaging planning. This is especially important because interventions can be positively influenced by high-quality imaging. Therefore, the most common diseases and procedures are described and imaging modality of choice and important image findings are discussed.

Total-body MR-imaging in oncology

Although MRI is an effective modality in oncology, state-of-the-art total-body MRI (TB-MRI) in the past was infeasible in the diagnostic work-up, due to the need for repeated examinations with repositioning and separate surface coils to cover all body parts. To overcome this limitation, either a moving table platform in combination with the body-coil or a special designed rolling table platform with one body phased-array coil have been implemented with promising results for both tumor staging and metastases screening. Since 2004, state-of-the-art TB-MR imaging with high spatial resolution has become feasible using a newly developed 1.5 Tesla TB-MRI system with multiple receiver channels. This review gives an overview based on the recent literature as well as our own experience concerning the possibilities, challenges, and limitations of TB-MRI in oncology, emphasizing both oncological staging and early tumor detection in asymptomatic subjects.

Prospective comparison of the impact on treatment decisions of whole-body magnetic resonance imaging and computed tomography in patients with metastatic malignant melanoma

Patient management and treatment strategies for metastatic melanoma depend largely on the stage of metastatic disease. The aim of this study was to compare contrast-enhanced whole-body magnetic resonance imaging (wbMRI) and whole-body computed tomography (wbCT) to detect distant metastases for staging. A total of 43 patients (41 with completed wbCT and wbMRI examination) with known American Joint Committee on Cancer (AJCC) stage III-IV malignant melanoma were examined and 775 metastases were identified by both methods. Whole-body CT was able to detect 522 metastases, whereas wbMRI found 730 metastases. Whole-body CT identified 188 pulmonary metastases, compared with 143 metastases detected by wbMRI. In kidneys, adrenal glands and lymph nodes, respectively, wbCT and wbMRI detected the same number of lesions. Whole-body MRI detected more metastases than wbCT in liver (detection rate 122/199), spleen (26/54), subcutaneous tissue (39/61), muscle (4/11), bone marrow (23/132) and brain (15/25). Therapy was modified as a consequence of wbMRI findings in 10/41 (24%) patients. In conclusion, wbMRI detected clearly more malignant melanoma metastases in most organ systems with the exception of lung metastases. More accurate and complete staging by wbMRI has an impact on treatment strategy in about one-quarter of the patients.

A Comparison of Whole-Body MRI and CT for the Staging of Lymphoma

OBJECTIVE

Our objective was to compare whole-body MRI and CT for the staging of lymphoma.

CONCLUSION

Whole-body MRI represents an alternative to CT in the staging of lymphoma, with an ability to stage disease, identify lymph nodes greater than 1.2 cm, and the additional ability to evaluate for the presence or absence of disease spread to bone marrow. CT allows detection of more nodes (< 1.2 cm) than MRI but this does not alter tumor stage.

Dynamic magnetic resonance imaging of solitary pulmonary nodules: utility of kinetic patterns in differential diagnosis

OBJECTIVE

The aim of this study was to evaluate the clinical feasibility of dynamic magnetic resonance (MR) imaging with a 3-dimensional (3D) gradient recalled echo (GRE) volumetric interpolated breath-hold examination (VIBE) sequence to differentiate between benign and malignant solitary pulmonary nodules (SPNs).

METHODS

Dynamic 3D GRE VIBE was performed in 45 patients with SPNs. For each lesion, the morphologic parameters, including the edge configuration, presence of peripheral enhancement (PE), and an internal signal on T2-weighted images, and the kinetic enhancement parameters were evaluated.

RESULTS

All 29 of the malignant SPNs had internal enhancement, whereas 13 (81%) of the benign SPNs did not exhibit internal enhancement. A washout pattern was only observed in the malignant SPNs. The presence of PE was found in 56% of the benign SPNs and in 50% of the malignant SPNs. The lesion size was significantly different between malignant SPNs with PE and those without PE (P <0.01). The positive predictive value for malignancy was 91% (29 of 32 malignant SPNs). The negative predictive value was 100% (13 of 13 benign SPNs).

CONCLUSIONS

A combination of morphologic criteria and kinetic information is useful for differentiating between benign and malignant SPNs. In particular, internal enhancement with PE and positive visual washout is thought be a useful tool.

Fast T1- and T2-weighted pulmonary MR-imaging in patients with bronchial carcinoma

PURPOSE

A prospective study to evaluate the diagnostic potential and limitations of three fast MRI sequences in patients with bronchial carcinoma based on the comparison with spiral CT.

MATERIAL AND METHODS

Three fast chest MRI sequences from 20 patients with central or peripheral bronchial carcinoma were evaluated by two observers for relation of tumour to adjacent structures, lymph node enlargement, additional pulmonary lesions and artefacts. The information from MR-imaging was compared with the results from spiral CT. MRI comprised a T1-3D-GRE breath-hold examination ("VIBE", TR/TE 4.5/1.9 ms, flip-angle 12 degrees , matrix 502 x 512, 2.5 mm coronal slices), a breath-hold, T2-HASTE sequence (TR/TE 2000/43 ms, matrix 192 x 256, 10 mm coronal slices) and a respiration-triggered T2-TSE sequence (TR/TE 3000-6000/120 ms, matrix 270 x 512, 6 mm transverse slices). The FOV was adapted individually (380-480 mm).

RESULTS

The presence of the primary bronchial carcinoma and infiltration of thoracic structures by tumour tissue could be demonstrated by all sequences. VIBE sequence was more suitable for detecting small pulmonary nodules than the other MRI examinations, but compared to CT still 20% of these lesions were missed. Contrary to VIBE and T2-weighted TSE scans, HASTE sequence was limited in imaging mediastinal lymph nodes due to missing relevant findings in 2/20 patients. HASTE images significantly provided the lowest rate of artefacts in imaging lung parenchyma (P < 0.001 in peripheral parenchyma), but spatial resolution was limited in this sequence. Concerning the differentiation between tumour and adjacent atelectasis (n = 8), T2-weighted TSE imaging was superior to CT and VIBE in all cases and to HASTE sequence in 4/8 patients.

CONCLUSION

The combination of VIBE and HASTE sequence allows for an adaequate imaging of thoracic processes in patients with bronchial carcinoma, limited only in visualizing small pulmonary nodules. To obtain more detail resolution and to differentiate tumour tissue from adjacent atelectasis, T2-TSE examination may be added in selected cases.

Fast Whole-Body Assessment of Metastatic Disease Using a Novel Magnetic Resonance Imaging System

OBJECTIVE

The objective of this study was to investigate the clinical use of a novel whole-body magnetic resonance imaging (MRI) system for comprehensive assessment of tumor spread in clinical routine.

MATERIAL AND METHODS

Sixty-five patients with different tumors with known metastatic disease and 6 healthy volunteers were included. High-resolution MRI from head to toe was performed using multiple phased-array surface coil elements, 24 independent receiver channels, and an integrated parallel acquisition technique (iPAT). A total room time of less than 60 minutes was required. Whole-body MRI and conventional spiral computed tomography (CT) were independently evaluated and compared in terms of feasibility, location/number of detected metastases, and therapeutic relevance.

RESULTS

Whole-body MRI was successfully performed in 68 of 71 subjects. Compared with CT, more metastases were detected by MRI in 11 of 63 patients (17%), particularly in brain, liver, spleen, lymph nodes, bone marrow, muscle, and subcutaneous fat tissue. According to these findings, therapy had to be modified in 6 of 63 patients (10%).

CONCLUSIONS

High-resolution whole-body MRI is feasible in clinical routine within 1 single examination and offers great potential for fast assessment of individual tumor spread and total tumor burden.

[Oncologic screening with whole-body MRI: possibilities and limitations]

In the last decade the interest in radiological screening examination increased among informed laymen enormously. Independent from the evidence of whole-body examinations for cancer prevention the discussion about screening must again be considered again due to the newest technical developments, since MRI of the whole-body with high spatial resolution is feasible now within one single examination. The newest system permits simultaneous connection of up to 76 coil elements and signal reception from 32 independent receiving channels. Whole-body MRI including magnetic resonance colonography (MRC) is feasible within 60 min. In this review potential investigation protocols will be presented. Potentials, challenges and limitations of whole-body MRI in the prevention of the malignancies most frequently leading to death are discussed on the basis own experiences examples and the literature.

MR imaging of lung parenchyma at 0.2 T: evaluation of imaging techniques, comparative study with chest radiography and interobserver analysis

The purpose of this study was to evaluate low-field MR imaging of the lung parenchyma in comparison with postero-anterior (PA) and lateral chest radiographs (CR). One hundred one prospectively randomized patients who had received routine CR were additionally examined with magnetic resonance imaging (MRI) at 0.2 T. Utilized sequences were: constructive interference in steady state (CISS), true fast imaging in steady state precession (True-FISP) and T1-weighted spin-echo (T1SE). Consensus reading of two observers was performed for CR. Three other observers analyzed hardcopies of the MRI examinations for each sequence independently. The individual results for the comparisons between the sequences and CR were calculated using kappa coefficients with their corresponding confidence intervals. Additionally, an interobserver analysis was performed. The proportions of agreement for the three sequences compared with CR were high, with 0.93 for CISS, 0.89 for True-FISP and 0.91 for T1SE. The kappa coefficients and the corresponding confidence intervals were 0.81 [0.68; 0.95] for CISS, 0.72 [0.57; 0.88] for True-FISP and 0.78 [0.65; 0.92] for T1SE. Concerning CISS, differences between MRI and CR were mainly related to advantages resulting from cross-sectional imaging. The smallest 95% lower confidence bound of the three kappa measures for comparing the MR readers with each other was 0.97, indicating a high interobserver agreement. Low-field MRI of the lung parenchyma using the CISS sequence is well comparable with chest radiography and demonstrates slight advantages resulting from the cross-sectional imaging technique.