Purpose: To analyze clinical outcome and define indications of MR-Total Spine Projection ( MR-TSP)in follow-up of scoliosis. The method was developed at our institution three years ago and allows imaging the whole spine and measurement of Cobb angles respectively reducing radiation exposure of children with scoliosis.
Methods and Materials: 115 patients ( 45 male/70 female) aged 6 to 18 years ( mean 14 )were examined at an 1.5 T Gyroscan ACS-NT Powertrack 6000 (Philips Medical Systems). Using the body coil coronal 3D EPI-sequences (TR/TE/flip angle/FOV:18/9.0/20/450) or 3D FFE-sequences (TR/TE/flip angle/FOV:18/4.5/20/450)of the upper and lower spine were performed. The data were postprocessed with a PC using a special self-developed program resulting in coronal and sagittal projections of the whole spine. The scoliotic curves were measured using the Cobb method and compared to the results of the upright standing radiographs of the whole spine by two experienced investigators ( one radiologist, one orthopedic surgeon ).
Results: 310 MR-TSP were obtained in 115 patients ( basic studies and follow-up controls ). No technical limitations for the MR examinations were found. In n=5 cases the following curve measurement failed due to metallic artifacts of braces. Scoliotic curves ranged from less than 10 in screening examinations to 57 degrees. The differences between the results of the MR-TSP ( obtained in supine position) compared to the upright standing radiographs ranged from 0 to 29 degrees. The mean deviation varied due to anatomical localization (thoracic, thoracic and lumbar, lumbar curve)and severity (mild, moderate or severe) of scoliosis. Overestimation of the Cobb angle was seen in only n=18, ranging from 0.5 to 13.5 degrees, mean was 3.3 degrees. Depending on the different position underestimation of the curves occured more frequently in n=132, ranging from 0.5 to 29 degrees, mean = 6.2 degrees. When screening examinations and special cases are excluded a mean of 5.1 degrees was found. Criteria were defined in which cases a deviation of 5 degrees can be tolerated cause classification of severity and treatment of the scoliosis are not distortet.
Conclusion: This MR-based procedure allows documentation of the whole spine (cervical, thoracic and lumbar segments) as a total spine image as well as scoliotic curve measurement. Basic studies have to be compared to an actual X-ray. In the majority of our cases MR-TSP could be recommended to replace some radiograph follow-up examinations and reduce the radiation exposure in juveniles with scoliosis.
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