Whole-Body MRI in Children: Current Imaging Techniques and Clinical Applications

Abstract

Whole-body magnetic resonance imaging (MRI) is increasingly used in children to evaluate the extent and distribution of various neoplastic and non-neoplastic diseases. Not using ionizing radiation is a major advantage of pediatric whole-body MRI. Coronal and sagittal short tau inversion recovery imaging is most commonly used as the fundamental whole-body MRI protocol. Diffusion-weighted imaging and Dixon-based imaging, which has been recently incorporated into whole-body MRI, are promising pulse sequences, particularly for pediatric oncology. Other pulse sequences may be added to increase diagnostic capability of whole-body MRI. Of importance, the overall whole-body MRI examination time should be less than 30-60 minutes in children, regardless of the imaging protocol. Established and potentially useful clinical applications of pediatric whole-body MRI are described.

Keywords: Infants and children; Systemic disease; Tumor; Whole-body MRI.

Fig. 1. 16-year-old boy with testicular rhabdomyosarcoma.

A. Coronal short tau inversion recovery (STIR) whole-body magnetic resonance imaging (MRI) obtained with dual-source parallel radiofrequency excitation technology at 3T reveals residual dielectric shading artifact (arrows) at medial aspect of left buttock and thigh. B. Coronal STIR whole-body MRI obtained at 1.5T demonstrates no substantial dielectric shading artifact throughout entire body.

Fig. 2. 11-year-old girl with Ewing sarcoma of cervical spine.

Compared with coronal short tau inversion recovery (STIR) whole-body MRI obtained with quadrature body coil approach at 1.5T (A), coronal STIR whole-body MRI obtained with sliding surface coil approach at 1.5T shows higher signal-to-noise ratio and spatial resolution (B). Longitudinal coverage of sliding surface coil approach is limited by 125 cm. Thus, both legs below low calves (arrows) were not included in this case due to this limitation (B).

Fig. 3. 2-year-old boy with infantile fibrosarcoma at craniocervical junction.

Coronal (A) and sagittal (B) short tau inversion recovery whole-body magnetic resonance imaging obtained with combined neurovascular and spine coils at 3T show high signal-to-noise ratio and spatial resolution (B). Spine coils provide high signals sufficient for imaging anterior body parts of this thin, small child.

Fig. 4. Advantages of T2-weighted Dixon fast spin echo whole-body magnetic resonance imaging (MRI) in adult volunteer.

Compared with coronal short tau inversion recovery whole-body MRI obtained at 3T showing incomplete fat suppression (A), coronal T2-weighted fast spin echo whole-body MRI with Dixon-based fat saturation at 3T (B) clearly demonstrates improved fat suppression throughout entire body except for left leg in lowest station (arrows) caused by fat-water swapping error. Motion artifacts in thorax and upper abdomen are less pronounced on T2-weighted fast spin echo imaging (B).

Fig. 5. 1-year-old boy with neuroblastoma.

Coronal T1-weighted Dixon-based fat-only (A) and water-only (B) whole-body magnetic resonance imaging at 3T shows that these two image types are swapped at second station covering thoracic region.

Fig. 6. 14-year-old boy with leukemia.

A. Coronal pre-contrast T1-weighted whole-body magnetic resonance imaging (MRI) at 1.5T shows that majority of normal fatty marrow is replaced by leukemic cells. B. Coronal post-contrast fat-saturated T1-weighted MRI at 1.5T reveals not only diffuse abnormal bone marrow enhancement but also extensive osteonecrosis in proximal humeri, distal femurs, and proximal tibias.

Fig. 7. 4-year-old boy with B-cell lymphoma.

Compared with coronal post-contrast in-phase whole-body magnetic resonance imaging (MRI) at 3T (A), normal bone marrow demonstrates dark signal intensity on coronal post-contrast opposed-phase whole-body MRI at 3T (B). In contrast, marrow-replacing lymphoma lesion in right tibia (arrowheads) remains hyperintense on opposed-phase image (B).

Fig. 8. 10-year-old boy with Burkitt lymphoma.

A. Initial coronal whole-body apparent diffusion coefficient (ADC) map at 1.5T shows restricted water diffusion in all bone marrow and multiple variable-sized renal masses, indicating viable tumors. B. Follow-up coronal whole-body ADC map at 1.5T obtained 9 days after induction chemotherapy demonstrates markedly increased water diffusion in lesions suggesting favorable treatment response.

Fig. 9. Whole-body magnetic resonance imaging (MRI) using continuously moving table approach in adult volunteer.

A. Low-resolution coronal reformatted fast gradient-echo whole-body MRI using continuously moving table approach (table feed, 46.9 mm/sec) at 3T was used as scout view for whole-body MRI or MR/positron emission tomography. High-resolution coronal reformatted fat-saturated T1-weighted gradient echo (B) and T2-weighted half-Fourier-acquired singe-shot turbo spin echo (C) whole-body MRIs using continuously moving table approach at 3T were obtained at much slower table feed (8.9 mm/sec). Compared with coronal Dixon-based fat-saturated T2-weighted fast spin echo whole-body MRI acquired with conventional multi-station approach (D), longitudinal coverage of high-resolution whole-body MRI acquired with continuously moving table approach is slightly limited (B, C) and stepping artifacts may degrade image quality (C).

Fig. 10. 15-year-old boy with neurofibromatosis type II and plexiform schwannomas.

A. Coronal short tau inversion recovery whole-body magnetic resonance imaging at 3T shows widespread plexiform schwannomas along nerve roots. Largest lesion (arrows) is noted in right suprarenal region. B. Plexiform schwannomas along cervical nerve roots are nicely delineated on curved planar reformatted post-contrast three-dimensional fluid attenuation inversion recovery image at 3T.

Fig. 11. 10-year-old girl with juvenile dermatomyositis.

A. Coronal short tau inversion recovery whole-body magnetic resonance imaging (MRI) at 1.5T reveals extensive muscular hyperintensity and reticular subcutaneous hyperintensity. B. Mild contrast enhancement in active dermatomyositis lesions is shown on coronal post-contrast fat-saturated T1-weighted gradient echo whole-body MRI at 1.5T.

Fig. 12. 6-year-old girl with juvenile rheumatoid arthritis.

Coronal short tau inversion recovery (STIR) post-contrast fat-saturated coronal three-dimensional T1-weighted gradient-echo magnetic resonance image (MRI) at 1.5T. Periarticular soft tissue T2 hyperintensity and enhancement around both shoulder and knee joints (arrows) suggesting active synovitis are identified on STIR (A) and post-contrast fat-saturated T1-weighted gradient echo (B) whole-body MRIs at 1.5T.