Diffusion-tensor magnetic resonance imaging of the growth plates: substantiation of the method and evaluation of its reproducibility

INTRODUCTION: In recent years there is an increasing interest in assessing the state of the physis among pediatric orthopedic traumatologists, due to the availability of surgical correction of conditions associated with impaired growth plate function. Application of these methods requires dynamic assessment of the state of the physis. The existing methods for assessing the functional state of the physis are few and imperfect. Magnetic resonance imaging (MRI), in particular diffusion tensor imaging (DTI), is promising for assessing the growth plates. OBJECTIVE: To assess the possibility of applying DTI technique to assess the state of the physis (growth plate). MATERIALS AND METHODS: The study was approved by the local ethical committee of the Institute of the Human Brain named after N.P. Bekhtereva of Russian Academy of Sciences, protocol No. 32, dated 21.12.2020. Informed consent was obtained from each legal representative. At the Turner National Medical Research Center for Сhildren’s Orthopedics and Trauma Surgery of the Ministry of Health of the Russian Federation a standard magnetic resonance examination of the knee joints was performed, additionally diffusion tensor tomography was performed in 75 patients aged 4.1 to 14.3 years (41 males, 34 females), both deemed healthy and with a known physeal pathology. The studies were performed using a Philips Ingenia ElitionX machine with a magnetic field strength of 3 Tesla, DTI was performed in the coronal plane, TE=71.2 ms, TR=4000 ms, b-factor value 600 s/mm2, 15 diffusion directions were used, slice thickness was 3 mm without gaps, the matrix size was 1.25×1.25 mm. The resulting images were processed using the DSI Studio software, including tract construction, estimation of the total volume and average length of the tracts. The reproducibility of the technique was assessed. RESULTS: Higher volumes and mean tract lengths were found in healthy males at puberty compared to other groups. When assessing reproducibility, the standard deviations were about 10% of the final value. DISCUSSION : Images of growth plate tracts were obtained. In individuals of pubertal age that were deemed healthy, the tract volume values and the average length of the tracts were higher than in individuals of prepubertal age and those with pathological conditions affecting the state of the growth plates. The average tract length turned out to be more reproducible than the total tract volume parameter. CONCLUSION : With the help of DTI, it is possible to evaluate the arrangement of the structures in the growth plates.