Purpose or Case Report: There is limited understanding and utilization of dynamic contrast enhancement MRI of marrow, periosteum and cartilage for diagnosis of musculoskeletal (MSK) disease in children. This is partly due to limited availability of pediatric disease models of marrow inflammation, infection, infiltration, or involvement by tumor. Herein we explore signal intensity time curves of relevant MSK targets using a 3D Golden-angle RAdial Sparse Parallel (GRASP) MRI technique. GRASP is an accelerated, free-breathing dynamic acquisition that has been shown to reduce the need for sedation. We aim to establish a baseline for normal enhancement characteristics of marrow, cartilage, synovium and periosteum of the growing skeleton in a sheep model as a precursor to translation to children.
Methods & Materials: GRASP data were acquired in 4 sheep using standard dose gadobutrol at 3 mL/sec. All studies were performed on a 3T system. GRASP data are acquired with consecutive radial spokes that are rotated by the golden angle. The data can be reconstructed into time-resolved dynamic frames with user-selectable temporal resolution during contrast passage (https://cai2r.net/research/radial-vibe-sequence). We reconstructed at a temporal resolution of 4.5s. Signal intensity curves were generated from regions-of-interests in: marrow of diaphysis, metaphysis, and epiphysis of the humerus, proximal humeral physis, periosteum of the proximal humerus, a thoracic vertebral body and an adjacent intervertebral disc.
Results: A sample data set is here https://www.dropbox.com/s/zmh5dakn847s6w0/20180727.mov
All structures exhibited onset of contrast-enhancement within approximately the same time frame after contrast administration, with a time to peak signal of <10s and with little washout over 180 seconds. There was no difference in the slope of wash-in and wash-out. However, the peak signal varied by anatomy. Specifically, signal in the diaphyseal marrow increased from 16% to 31% above baseline; metaphyseal marrow: 56% to 246%; physis: 155% to 206%; epiphyseal marrow: 54% to 96%; periosteum: 62% to 339%; intervertebral disc: 65% to 118%; and vertebral body: 155% to 321%.
Conclusions: GRASP allows rapid free-breathing characterization of contrast ehancement in the growing skeleton. It provides excellent anatomic delineation and can potentially demonstrate difference in peak signal between relevant MSK targets. We hope to translate our technique to children, and utilize it for qualitative and quantitative diagnosis of pediatric MSK disease.