The Diagnostic Value Of Dual-detector Spectral CT In Lumbar Intervertebral Disc Degeneration

PART ONE: THE DIAGNOSTIC VALUE OF DUALDETECTOR SPECTRAL CT FOR EVALUATING LUMBAR INTERVERTEBRAL DISC DEGENERATIVE CHANGEObjective: Based on the degree of lumbar intervertebral disc degeneration(LIDD)evaluated by magnetic resonance imaging(MRI),we explored the feasibility of electron density image(EDM),calcium suppression image(Ca Supp)and EDM + Ca Supp fusion image of dual-layer detector spectral CT to evaluate IDD.Methods: 65 patients with lumbar spine MRI and DLCT scan within 1 month were retrospectively collected and analyzed.Modified Pfirrmann Grades(m PG)were evaluated on sagittal T2-weighted imaging(T2WI)of lumbar MRI,and the degree of IDD was divided into 1-5 grades.The regions of interest(ROI)were placed in the nucleus pulposus area of the intervertebral disc axis on the Intelli Space Portal(ISP)to obtain the average CT value(Hounsfield-unit,HU),CT * value and electron density(ED)value of the nucleus pulposus.Two diagnosticians visually graded the intervertebral disc in pseudo-color EDM,Ca Supp,and fusion images,and divided it into three levels according to the color difference between the nucleus pulposus and the annulus fibrosus,they used 5-point scale for subjective image quality assessment,and used noise,signal-to-noise ratio(SNR),and contrast to noise ratio(CNR)to compare the objective image quality of standard CT(SC),EDM,and Ca Supp images.Kappa test was used to analyze the consistency of m PG grading,three visual grading and subjective image quality evaluation between the two physicians.Spearman rank correlation test was used to compare the correlation between mean CT value,ED value and m PG,and the correlation between three visual grades and m PG grade.Tambane ’s T2 test was used for pairwise comparison between groups.Results: 1.There was a positive correlation between CT value and ED value of the total nucleus pulposus(r = 0.788,P < 0.001),and there was also a positive correlation of each m PG grade nucleus pulposus.The m PG grade was positively correlated with the average ED value,CT * value and ED value of the nucleus pulposus(P < 0.001),average CT value,ED value and CT * value of m PG low grade and high grade were statistically different(P < 0.05).2.The three visual grades were positively correlated with the m PG grade and the average ED value and CT * value of the nucleus pulposus.There were statistical differences in the pairwise comparisons of grade I,grade II and grade III(P < 0.001),and there were statistical differences in the ED value and CT* value of the nucleus pulposus in different grades(P < 0.001).3.The two readers evaluated the consistency of pseudo-color EDM,Ca Supp,EDM+ Ca Supp fusion images(k=0.693,0.643,0.665).Subjective image quality ranking from high to low: pseudo-color EDM > Ca Supp > fusion image,image noise: EDM <Ca Supp < SC image,CNR: EDM > Ca Supp > SC,SNR: EDM > Ca Supp > SC,the difference was statistically significant(P < 0.001).Conclusion: The visual grading of pseudo-color EDM,Ca Supp,EDM + Ca Supp fusion images of intervertebral disc has a good correlation with m PG grading,which can directly reflect the degree of intervertebral disc degenerative change.ED value and CT * value can quantitatively study intervertebral disc degenerative change,and EDM image has best quality,that can be used as a tool to evaluate IDD.PART TWO: THE DIAGNOSTIC VALUE OF DUALDETECTOR SPECTRAL CT FOR EVALUATING LUMBAR INTERVERTEBRAL DISC PROTRUSIONObjective: Based on the evaluation results by magnetic resonance T2 WI images,we explored the DLCT spectral images with the highest diagnostic efficiency for evaluating the degree of intervertebral disc herniation/ bulging and spinal stenosis.Methods: 65 patients with lumbar spine MRI and DLCT scan within 1 month were retrospectively collected and analyzed.Two senior diagnosticians diagnosed each disc herniation / bulging and the degree of spinal stenosis at the corresponding level based on MRI images as a reference standard.SC,gray-scale and pseudo-color Ca Supp images,EDM images,and pseudo-color Ca Supp+EDM fusion images were reconstructed on the ISP post-processing platform.A physician with 3 years of radiological diagnosis experience evaluated each disc herniation/bulging and the degree of spinal stenosis at the corresponding level in the above images.We use 2 × 2 cross table to calculate sensitivity,specificity,negative prediction value(NPV)and positive prediction value(PPV)of each image,the receiver operating characteristics(ROC)curve was drawn to analyze the diagnostic efficacy,which was expressed by area under curve(AUC).The Wilcoxon signed rank test was used to evaluate the difference in the diagnosis of disc herniation by each image.Kappa test was used to analyze the consistency between the evaluation results on each spectral reconstruction image and the MRI results.Results: 1.Compared with SC images,spectral CT reconstruction images significantly improve the diagnostic efficacy of disc herniation/bulging and spinal stenosis,also to the benefit of judging the location of disc herniation.The diagnostic efficacy of pseudo-color images is higher than that of gray-scale images.Pseudo-color EDM images have the most advantages in diagnosing disc herniation/bulging,and spinal stenosis.2.At the level of each disc,the diagnostic sensitivity of DLCT spectral reconstruction images was higher than SC images in the diagnosis of disc herniation,but the specificity was not improved.Conclusion: The diagnostic efficacy of DLCT gray-scale and pseudo-color spectral images for lumbar disc herniation,bulging and spinal stenosis is higher than SC images,also is helpful to judge the location of lumbar disc herniation.The diagnostic accuracy is significantly improved with using spectral reconstruction.Pseudo-color EDM images have the most advantages in judging lumbar disc herniation and bulging.