The Value Of Virtual Monoenergetic Imaging And Multi-parameter Imaging Of The Spectral CT In The Activity And Severity Of Crohn ’s Disease

Part ⅠApplication value of virtual monoenergetic imaging in improving image quality of computed tomography enterography on spectral CT Objective To explore the application value of virtual monoenergetic imaging in improving enterography image quality of inflammatory bowel disease（IBD）on dual-layer detector spectral CT and to determine the optimal keV for displaying the inflammation of intestine.Methods 33 cases of Crohn’s disease（CD）,31 cases of ulcerative colitis（UC）examined by computed tomography enterography（CTE）in the First Affiliated Hospital of Kunming Medical University from April 2021 to June 2022 were retrospectively analyzed.The CTE examination on the new dual-layer detector spectral CT and the colonoscopy were performed within one week,and then the original venous images were reconstructed to obtain conventional mixed energy images and virtual monoenergetic 40～70 keV images.One-way ANOVA was used to compare the CT values,background noise,signal-to-noise ratio（SNR）and contrast noise ratio（CNR）among conventional mixed energy images and 40～70 keV VMI.The 5-grade grading method were applied for subjective evaluation,and the Kruskal-Wallis H test is used to compare the differences in 5 groups.Paired χ² test or Fisher exact probability was used to test the difference between optimal VMI image and conventional mixed energy images in evaluating active inflammatory bowel disease.Results In virtual monoenergetic imagings,the CT values,SNR and CNR of the intestinal lesions were highest on 40 keV group:215.0（178.6,250.3）HU、25.2（17.4,38.2）、18.8（11.7,29.9）,and decreasing with the increasing of energy levels,and the differences in CT values and CNR between groups are statistically significant（P <0.001）,The difference of CT values,SNR,CNR between 70 keV and mixed energy groups was not statistically significant（P >0.05）.The noise of the mixed energy image was the largest（9.3±4.0）,and was statistically difference from the VMI image groups（P <0.05）,while the noise difference between the VMI groups was not statistically significant（P >0.05）.In subjective evaluation of VMI images,40 keV group was highest in subjective score（The scores of the two physicians were 4.77 ±0.52 and 4.80 ± 0.48）and decreasing with the increasing of energy levels,and the difference between the each two groups was statistically significant（P <0.001）;there is no difference in image quality score of 70 keV and the mixed energy group（P >0.05）.There was no significant difference between VMI 40 keV image and mixed-energy image in evaluating active inflammatory bowel disease（P = 0.200）.Conclusion The dual-layer detector spectral CT low-level VMI can optimize the image quality of CTE in IBD,and is useful to evaluate the intestinal inflammatory range.Among them,the VMI 40 keV image has the best display on both the objective and subjective evaluation,can increase the diagnostic confidence in active inflammatory bowel disease and it is suitable for clinical promotion and use.Part ⅡApplication value of the multi-parameter imaging on spectral CT in evaluation the activity and severity of Crohn ’s diseaseObjective To explore the application value of the multi-parameter imaging on spectral CT in quantitative evaluation of the activity and severity of Crohn ’s disease（CD）.Methods 50 cases of Crohn’s disease examined by CTE in the First Affiliated Hospital of Kunming Medical University from April 2021 to November 2022 were retrospectively analyzed.These patients were divided into the mild activity group（16cases）,the moderate to severe activity group（20 cases）,and the complication group（14 cases）according to the Simplified Endoscopic activity Score for Crohn disease（SES-CD）and complications.The CTE examination on the new dual-layer detector spectral CT and the colonoscopy were performed within one week,and then the conventional mixed energy images and 40 keV virtual virtual monoenergetic imaging（VMI）,iodine concentration（IC）and Z effective maps（Zeff）were reconstructed.The corresponding values of the lesion and the abdominal aorta at the L3 level were measured.Then use the value of lesion divided by aorta obtained VMI NCT40 keV、NIC、NZeff.One-way ANOVA was used to compare the differences of multi-parameter VMI CT40_keV,IC,Zeff,VMI NCT40 keV,NIC and NZeff among the three groups on arterial phase,venous phase and delayed phase.The receiver operating characteristic（ROC）curve was drawn for the parameters with statistically significant differences,and the area under the curve（AUC）was calculated to test the diagnostic efficacy of each parameter.The optimal threshold,sensitivity and specificity of each parameter were determined according to the Youden index.The classification items of image feature analysis of conventional CTE were analyzed by chi-square test or Fisher exact probability method.Results The parameters of spectral CT increased along with the increase of activity and severity classification.There were significant differences in VMI CT _{40 keV}、IC、Zeff 、 VMINCT40 keV 、 NIC and NZeff between mild activity group and moderate-severe activity group in arterial phase and venous phase（P < 0.05）.The ROC curve showed that the evaluation efficiency of each parameter in the venous phase was higher than that in the arterial phase.The prediction efficiency of the combined parameters in the arterial phase and the venous phase was better than single parameter.The prediction efficiency of the combined parameter in the venous phase was the best,and the AUC value、sensitivity and specificity were 0.964、88.9% and94.2%.There were significant differences in VMI CT _{40 keV}、IC、Zeff、VMI NCT _{40 keV}、NIC and NZeff between mild activity group and complication group in delay phase（P< 0.05）.The ROC curve showed that the parameters of the delayed phase had a well prediction effect on the complications,and the AUC value、sensitivity and specificity were 0.937、95.2% and 89.5%.In the conventional CTE image features,the intestinal wall thickness increased with the severity of the disease.Intestinal wall stratification enhancement,periintestinal exudation/inflammation,comb sign and adjacent mesenteric fat proliferation increased with the severity of the disease（P < 0.05）.Conclusion The multi-parameter values of spectral CT have good application value in activity classification of CD in arterial phase and venous phase,and the venous phase is the best,while the multi-parameter values have good diagnostic efficacy in distinguishing mild activity of CD and possible complications in delayed phase.Combined with the characteristics of conventional CTE images,it has better evaluation efficiency for the activity classification and severity of CD,and provides reference for clinical treatment.