Chest examinations in children with real-time magnetic resonance imaging: first clinical experience

Abstract

Background Real-time magnetic resonance imaging (MRI) based on a fast low-angle shot technique 2.0 (FLASH 2.0) is highly effective against artifacts caused due to the bulk and pulmonary and cardiac motions of the patient. However, to date, there are no reports on the application of this innovative technique to pediatric lung MRI. Objective This study aimed to identify the limits of resolution and image quality of real-time lung MRI in children and to assess the types and minimal size of lesions with these new sequences. Materials and methods In this retrospective study, pathological lung findings in 87 children were classified into 6 subgroups, as detected on conventional MRI: metastases and tumors, consolidation, scars, hyperinflation, interstitial pathology and bronchiectasis. Subsequently, the findings were grouped according to size (4–6 mm, 7–9 mm and ≥ 10 mm) and evaluated for visual delineation of the findings (0 = not visible, 1 = hardly visible and 2 = well visualized). Results Real-time MRI allows for diagnostic, artifact-free thorax images to be obtained, regardless of patient movements. The delineation of findings strongly correlates with the size of the pathology. Metastases, consolidation and scars were visible at 100% when larger than 9 mm. In the 7–9 mm subgroup, the visibility was 83% for metastases, 88% for consolidation and 100% for scars in T2/T1 weighting. Though often visible, smaller pathological lesions of 4–6 mm in size did not regularly meet the expected diagnostic confidence: The visibility of metastases was 18%, consolidation was 64% and scars was 71%. Diffuse interstitial lung changes and hyperinflation, known as “MR-minus pathologies,” were not accessible to real-time MRI. Conclusion The method provides motion robust images of the lung and thorax. However, the lower sensitivity for small lung lesions is a major limitation for routine use of this technique. Currently, the method is adequate for diagnosing inflammatory lung diseases, atelectasis, effusions and lung scarring in children with irregular breathing patterns or bulk motion on sedation-free MRI. A medium-term goal is to improve the diagnostic accuracy of small nodules and interstitial lesions.

Imaging of Acute Complications of Community-Acquired Pneumonia in the Paediatric Population—From Chest Radiography to MRI

“…Movement and breathing by the child do not cause artefacts either [30]. To date, this technique has only been available in research settings and is limited to a single MRI brand [31]. Spatial resolution…”

“…Movement and breathing by the child do not cause artefacts either [30]. To date, this technique has only been available in research settings and is limited to a single MRI brand [31]. Spatial resolution of MRI is usually lower than CT, but new sequences, like ultra-short and zero echo time sequences, allow isotropic voxel sizes of around 1 mm [32].…”

Real-time MRI: a new tool of radiologic imaging in small children

“…1 Schematic illustration of a vendor-neutral data flow for generating real-time MR images using the volume coverage sequence as an example (blue pathway). The real-time technology integrates seamlessly into the standard MR workstation workflow like any genuine, conventional MR sequence [ 20 ] …”

“…Therefore, both are often performed with the more stable proton-density weighting and the contrast-rich T2/T1 weighting. Even small lesions, such as metastases, can often be detected above a diameter of 4 mm (Video 7 ), but only lesions larger than 10 mm can be depicted securely [ 20 ]. Therefore, rt-MRI of the lungs is not yet ready for screening for small metastases.…”