Abstract
Lung MRI makes it possible to replace up to 90% of CT examinations with radiation-free magnetic resonance diagnostics of the lungs without suffering any diagnostic loss. The individual radiation exposure can thus be relevantly reduced. This applies in particular to children who repeatedly require sectional imaging of the lung, e.g., in tumor surveillance or in chronic lung diseases such as cystic fibrosis. In this paper we discuss various factors that favor the establishment of lung MRI in the clinical setting. Among the many sequences proposed for lung imaging, respiration-triggered T2-W turbo spin-echo (TSE) sequences have been established as a good standard for children. Additional sequences are mostly dispensable. The most important pulmonary findings are demonstrated here in the form of a detailed pictorial essay. T1-weighted gradient echo sequences with ultrashort echo time are a new option. These sequences anticipate signal loss in the lung and deliver CT-like images with high spatial resolution. When using self-gated T1-W ultrashort echo time 3-D sequences that acquire iso-voxel geometry in the sub-millimeter range, secondary reconstructions are possible.
Highlights
Lung MRI offers the possibility of functional assessment regarding ventilation and perfusion [2], which can only be achieved with functional diagnostics or nuclear medical methods at this point
The exclusively morphological evaluation of the lung with conventional MR proton imaging has become the method of first choice at many pediatric radiology facilities when sectional imaging of the lung is necessary [5, 6]
The correct indication and the preselection of children with a so-called MR-plus pathology are crucial for successful MRI diagnostics of the lungs
Summary
Most pediatric radiology institutions exclusively use T2-weighted breath-triggered turbo spin-echo (TSE) sequences with long echo traction; these sequences show good T2-contrast of the pathologies against the dark lung This results in largely artifact-free, sharp images. In the case of abscessing pneumonia has the use of a breath-triggered T1-W gradient echo sequence proved to be effective because abscesses in T2-W sequences can have the same signal intensity as the infiltrated lung tissue In these rare cases, a diffusion-weighted imaging (DWI) sequence can help to differentiate between serous and purulent fluid accumulations (Table 3). Assuming an adequate examination technique, MRI diagnostics is on a par with CT for these diseases This includes all lung diseases with alveolar exudation and infiltration by infections [24, 25], tissue proliferation such as tumors or metastases [22], malformations such as sequesters [26] and cystic fibrosis, which is important in pediatric pulmonology [27]. The ventilation, perfusion and dynamic flow-volume loop maps are reconstructed entirely after the image acquisition using complex registration and post-processing algorithms, which are currently available as a research tool
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