The Value Of DTI And T2-mapping For Evaluation Of Spinal Radiculits In Animal Models

PartⅠ Optimization of Diffusion Tensor Sequence For LumbosacralSpinal Nerve Roots in Animal ModelsObjective: To determine the fit parameters of diffusion tensor imagingin the imaging of lumbosacral spinal nerve roots.Materials and Methods:20healthy adult Chinese piglets were scannedwith DTI using three different imaging parameters. At first diffusion gradientdirections and b-value were fixed to a constant value and pigs were thenscanned thrice adjusting slice thickness and gap to three different values,namely2mm/0mm,3mm/0mm and4mm/0mm respectively. With secondsetup of parameter, slice thickness and gap between each slices and b valuewere fixed with three variable diffusion gradient direction viz.6,15,25respectively while the third setup of parameter diffusion gradient directions,slice thickness and gap were fixed with variable b value400s/mm2;600s/mm2;800s/mm2. Thereafter, original images of DTI were transferred to theworkstation to reconstruct the fractional anisotropy map and apparentdiffusion coefficient map, which were interpreted by two experiencedradiologist to analyze the image quality of the original and processed imagesand to score them individually. Finally, the difference between the qualities ofimage with each parameter was compared using Wilcoxon rank sum test andStudent-Newman-Keuls test.Results: In parameters with fixed diffusion gradient and b value, themean score of image quality was found to be2.65±0.489,2.50±0.512, 2.40±0.502adjusting the thickness and gap to2mm/0mm,3mm/0mm and4mm/0mm respectively. No significant statistical difference were noted (p>0.05). While fixing slice thickness gap and b value to a constant value, themean score of image quality was found to be1.35±0.501,2.35±0.489,2.65±0.476for diffusion gradient directions:6,15,25respectively. Imagequality was found to be better with diffusion gradient directions of25ascompared to that of15and6(p <0.05). In parameters with variable b value inwhich the slice thickness, gap and diffusion gradient were kept at constant,the image quality mean scores were1.70±0.470,2.65±0.489,2.45±0.510for bvalue respectively. Image quality with b value of600s/mm2and800s/mm2were similar in resolution to each other (p>0.05) but better than imageobtained with b value of400s/mm2(p <0.05)Conclusion: The optimal slice thickness gap, diffusion gradient and bvalue for better DTI image resolution in scanning pig’s lumbosacral spinalnerve roots were2mm/0mm,25, and600s/mm2respectively.Part Ⅱ The Value of DTI and T2-Mapping for Evaluation ofNon-Comppressive Spinal Radiculitis in Piglets ModelsObjective: To study the value of DTI and T2-mapping in the diagnosisof non-compressive lumbar disc herniation.Materials and Methods: Seven healthy adult Chinese piglets werescanned with DTI and T2-mapping under general anaesthesia before injectingCT guided2ml nucleus homogenate into one side of intervertebral foramen toinduce nerve root inflammation.14days post induction of nerve rootinflammation, the pigs were scanned with DTI and T2mapping at3T MRI toobtain FA, ADC and T2values of bilateral L5, L6, S1spinal nerve roots.Finally the FA, ADC and T2value of each inflammation induced nerve root were compared with their contralateral normal nerve roots as well as with thethe ipsilateral nerve root value obtained before induction of inflammation.Results:The mean FA, ADC and T2values of bilateral nerve roots were0.506±0.055vs0.514±0.039，1.156±0.129vs1.161±0.135，52.486±1.461vs52.138±1.326respectively. Statistically, there was no significant differencebetween the bilateral nerve roots (p>0.05).After induction of inflammation, the mean FA value of the contralateralnerve roots, the inflamed spinal nerve roots and nerve roots prior toinflammation induction were0.506±0.055vs0.394±0.1791vs0.531±0.048.We found that there was statistical difference (p <0.05)After induction of inflammation, the mean ADC value of thecontralateral nerve roots, the inflamed spinal nerve roots and nerve roots priorto inflammation induction were1.156±0.129vs1.564±0.1240respectively. Wefound that there was statistical difference (p <0.05).After induction of inflammation, the mean T2value of the contralateralnerve roots, the inflamed spinal nerve roots and nerve roots prior toinflammation induction were52.486±1.461vs63.224±2.111respectively. Wefound that there was statistical difference (p <0.05).Pathological finding of the induced nerve root inflammation revealedthat there were edema, infiltration of inflammatory cell and damage of themembrane structure.Conclusion: The diffusion-parameters of DTI and T2relaxationproperties can reflect the characteristics of radiculitis caused by nucleus fluidleaked from adjacent disc.