Magnetic resonance imaging of the mediastinum, chest wall and pleura in children

Mediastinal thymoma: A difficult diagnosis in the pediatric age

Thymoma is a rare neoplasm of the anterior mediastinum, which originates from the epithelium of the thymic gland; it occurs mainly in middle-aged adults and is much less common in children. The tumor has slow growth and is asymptomatic in most pediatric cases, thus resulting in an accidental discovery; one-third of the young patient presents symptoms related to the compression of the tumor mass on the surrounding anatomic structures and/or related to paraneoplastic syndromes. Surgery is the treatment of choice and complete resection of the thymoma achieves excellent long-term results in terms of disease-free survival. In this article, we report the clinical case of a 21-month-old girl who came to our observation for persistent cough for over a month investigated with a chest X-ray, performed in another hospital. The X-ray showed an extensive opacification of the left hemithorax with contralateral dislocation of the mediastinum. The instrumental investigations carried out in our hospital (ultrasound, computed tomography, and magnetic resonance of the chest) showed a voluminous expansive mass of the left antero-superior mediastinum, which occupied the entire ipsilateral hemithorax and not dissociable from the thymus. At the histologic examination, the mass resulted to be a B1 thymoma with a low degree of malignancy according to the histologic classification of thymic tumors of the World Health Organization.

ACR Appropriateness Criteria® Imaging of Mediastinal Masses

Mediastinal masses can present with symptoms, signs, and syndromes or incidentally. Selecting the appropriate diagnostic imaging study for mediastinal mass evaluation requires awareness of the strengths and weaknesses of the various imaging modalities with regard to tissue characterization, soft tissue contrast, and surveillance. This publication expounds on the differences between chest radiography, CT, PET/CT, ultrasound, and MRI in terms of their ability to decipher and surveil mediastinal masses. Making the optimal imaging choice can yield diagnostic specificity, avert unnecessary biopsy and surgery, guide the interventionist when necessary, and serve as a means of surveillance for probably benign, but indeterminate mediastinal masses. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Large airway diseases in pediatrics: a pictorial essay

“Large airway diseases” is being used as an all-encompassing phrase to describe a broad spectrum of pathological entities, which involves the trachea, main, lobar, and segmental bronchi of up to 3 mm diameter. Imaging modalities such as radiography, computed tomography, and magnetic resonance imaging contribute to the identification and diagnosis of each entity. Knowledge of clinical information, normal cross-sectional anatomy, and imaging characteristics of large airway diseases is necessary for appropriate radiologic evaluation. This review provides information about congenital and acquired diseases of the large airways in the pediatric population.

Magnetic resonance imaging of the pediatric mediastinum

The mediastinum, the central anatomical space of the thorax, is divided by anatomical landmarks but not by physical boundaries. The mediastinum is a conduit, a space through which cranial nerves, important nerve branches, the sympathetic chain, vascular structures, and visceral structures, the trachea and esophagus pass. This arrangement allows contiguous extension or communication of disease along facial planes and through potential spaces to and from the head and neck or cervical spine, to and from the superior mediastinum, between superior and inferior mediastinal levels, and between inferior mediastinal spaces into the intra- and retroperitoneal spaces. Magnetic resonance imaging (MRI) of the mediastinum in children poses technical challenges, in particular cardiac and respiratory motion, and diagnostic challenges, including a broad range of tissue types and possible diagnoses. In this paper we review mediastinal anatomy, MRI sequences and protocol choices and include a short discussion of features and MRI findings of some of the congenital and acquired pathologies that are most often encountered in the pediatric mediastinum.

Free-breathing pediatric chest MRI: Performance of self-navigated golden-angle ordered conical ultrashort echo time acquisition

PURPOSE

To assess the feasibility and performance of conical k-space trajectory free-breathing ultrashort echo time (UTE) chest magnetic resonance imaging (MRI) versus four-dimensional (4D) flow and effects of 50% data subsampling and soft-gated motion correction.

MATERIALS AND METHODS

Thirty-two consecutive children who underwent both 4D flow and UTE ferumoxytol-enhanced chest MR (mean age: 5.4 years, range: 6 days to 15.7 years) in one 3T exam were recruited. From UTE k-space data, three image sets were reconstructed: 1) one with all data, 2) one using the first 50% of data, and 3) a final set with soft-gating motion correction, leveraging the signal magnitude immediately after each excitation. Two radiologists in blinded fashion independently scored image quality of anatomical landmarks on a 5-point scale. Ratings were compared using Wilcoxon rank-sum, Wilcoxon signed-ranks, and Kruskal-Wallis tests. Interobserver agreement was assessed with the intraclass correlation coefficient (ICC).

RESULTS

For fully sampled UTE, mean scores for all structures were ≥4 (good-excellent). Full UTE surpassed 4D flow for lungs and airways (P < 0.001), with similar pulmonary artery (PA) quality (P = 0.62). 50% subsampling only slightly degraded all landmarks (P < 0.001), as did motion correction. Subsegmental PA visualization was possible in >93% scans for all techniques (P = 0.27). Interobserver agreement was excellent for combined scores (ICC = 0.83).

CONCLUSION

High-quality free-breathing conical UTE chest MR is feasible, surpassing 4D flow for lungs and airways, with equivalent PA visualization. Data subsampling only mildly degraded images, favoring lesser scan times. Soft-gating motion correction overall did not improve image quality.

LEVEL OF EVIDENCE

2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:200-209.

Recurrent Pneumonia in Children: A Reasoned Diagnostic Approach and a Single Centre Experience

Recurrent pneumonia (RP), i.e., at least two episodes of pneumonia in one year or three episodes ever with intercritical radiographic clearing of densities, occurs in 7.7%–9% of children with community-acquired pneumonia. In RP, the challenge is to discriminate between children with self-limiting or minor problems, that do not require a diagnostic work-up, and those with an underlying disease. The aim of the current review is to discuss a reasoned diagnostic approach to RP in childhood. Particular emphasis has been placed on which children should undergo a diagnostic work-up and which tests should be performed. A pediatric case series is also presented, in order to document a single centre experience of RP. A management algorithm for the approach to children with RP, based on the evidence from a literature review, is proposed. Like all algorithms, it is not meant to replace clinical judgment, but it should drive physicians to adopt a systematic approach to pediatric RP and provide a useful guide to the clinician.