Skeletal age assessment in children using an open compact MRI system

Abstract

MRI may be a noninvasive and alternative tool for skeletal age assessment in children, although few studies have reported on this topic. In this article, skeletal age was assessed over a wide range of ages using an open, compact MRI optimized for the imaging of a child's hand and wrist, and its validity was evaluated. MR images and their three-dimensional segmentation visualized detailed skeletal features of each bone in the hand and wrist. Skeletal age was then independently scored from the MR images by two raters, according to the Tanner-Whitehouse Japan system. The skeletal age assessed by MR rating demonstrated a strong positive correlation with chronological age. The intrarater and inter-rater reproducibilities were significantly high. These results demonstrate the validity and reliability of skeletal age assessment using MRI.

Magnetic field shimming of a permanent magnet using a combination of pieces of permanent magnets and a single-channel shim coil for skeletal age assessment of children

“…We first performed coarse shimming with pieces of small permanent magnets and then performed SC shimming to correct the residual high-order spatial inhomogeneity. In addition, we obtain MR images of the left hands of human subjects with the sequences used for MR skeletal examination in the previous study [7] and show that image artifacts are sufficiently suppressed so that anatomical structures of bones necessary for skeletal age assessment are clearly visualized in the MR images.…”

“…Its size is about 66% of that of the magnetic circuit used in the previous work [7], which enhances the openness and compactness of the system. The distance from the edge of the magnetic circuit to the center was 20 cm.…”

“…We used a solenoid RF coil optimized for imaging a child's hand that was the same as the coil used in the previous work [7]. The coil was a 16-turn solenoid, 17.6 cm long, and was made by winding Cu foil (0.1 mm thick) around an oval acrylic pipe (aperture: 10 cm  5 cm; length of 220 mm; thickness of 4 mm) and divided in quarters with three chip capacitors (100 pF) to reduce stray capacitance between the hand and coil.…”

“…Although plain radiography has been the gold standard for skeletal age assessment, magnetic resonance imaging (MRI) has recently emerged as an alternative [4][5][6] because of its noninvasive and nonirradiative nature. In a previous study [7], we showed the validity of skeletal age assessment using an open, compact MRI system. However, the magnetic circuit used in the previous work was designed to image an adult hand [8][9][10], and was large for young children (620 mm × 1006 mm × 620 mm in size, 700 kg in weight).…”

“…The sequence parameters were the same as those used in the previous work [7]. Using the MR images, the skeletal age for the 4.9-year-old volunteer was rated according to the Tanner-Whitehouse (TW2) Japan RUS system (where RUS stands for the radius, ulna, and 11 short bones in rays 1, 3, and 5) [44].…”