Abstract
Purpose of the study
The aim of this work was to study the influence of the slice orientation of T2 axial images in numerical measurements of DSCA and study the effect that this change of slice angle would have on the morphological grading assessment.
Methods and Results
TSE T2 three dimensional aquisition MRI studies reconstructed with OsiriX DICOM viewer from 32 patients were used. Patients included were a series of consecutive cases with either suspected spinal stenosis or low back pain. A total of 97 disc levels were studied and axial reconstructions were made at 0°, +10°, +20°, +30° relative to the disc space orientation. For each image, DSCA was digitally measured and a severity grade was assigned by two observers according to the recently-published 4-point (A-D) morphological grading system. Interobserver kappa score was 0.71. Statistical analysis of DSCA measurements was performed using kappa and t-tests. Comparing DCSA between 0° at each level and +10°, +20° and +30° slice orientation, a significant increase in surface area was found in each case (P<0.0001). % change in DSCA combining all disc levels comparing 0° and +10°: range -15.48% to +31.89% (SD 18.40%); 0° and +20°: range -24.00% to +143.82% (SD 20.45%); 0° and +30°: range -29.35% to +231.13% (SD 26.52%). At 13 disc levels, DSCA was <100mm2 at 0°, but changed to >100mm2 in three cases by a +10° increase, in five cases by a +20° increase and in 10 cases by a +30° increase. In only two out of 97 levels studied did the morphological grading change as the angle increased, one of which was not amongst those above (change in DSCA from <100mm2 to >100mm2).
Conclusion
MRI slice angle significantly affects DSCA, and thus potentially the decision taken regarding management whilst morphological grading is little affected by image acquisition technique.
