Value Of ¹⁸F-FDG PET/CT In The Diagnosis Of Inflammatory Bowel Disease （IBD）

[Objective]1. To explore the imaging characteristic,different morphological structure and metabolism of 18F-FDG PET/CT in the diagnosis of inflammatory bowel disease (IBD),and compared with MRI/CT and colonoscopy in the same term.2. To explore the activity of index evaluation value of 18F-FDG PET/CT in the diagnosis of inflammatory bowel disease (IBD).3. To analyze the correlation of 18F-FDG SUVmax and activity degree of IBD.[Materials and Methods]1.Case selectionThe clinicopathological datas of 75 patients with IBD confirmed by colonoscopy from March 2010 to March 2014 were reviewed retrospectively.30 of them are ulcerative colitis(UCs),including 16 men and 14 women, aged from 19 to 62 years old,with a mean age of 40.5 years old,and the rest are Crohn’ sdiseases (CDs),including 30 men and 15 women, aged from 8 to 68 years old, with a mean age of 38 years old. Each patient underwent a whole body 18F-FDG PET/CT scan and C Reactive Protein(CRP) examination before or after 18F-FDG PET/CT scan within one week. The 65 patients of 75 IBDs confirmed by endoscopy and pathologically,and the rest are confirmed by clinic comprehensive diagnosis.All patients were intended to the active phase group(48 patients) and the chronic phase group (27 patients).17 patients of 75 IBDs underwent 18F-FDG PET/CT and MRI/ contrast-enhanced CT in the same term.2. Imaging modality and imaging agentThe examinations were carried out using a GE Discovery LS PET/CT scanner (GE, Healthcare, and Waukesha, WI). The positron emitter was produced using the cyclotron of PET tracer (GE, Healthcare, Waukesha, WI).The tracer 18F-FDG, was manufactured automated by the tracer synthesis system of FDG Microlab (GE, Healthcare, Waukesha, WI), with a radiochemical purity> 95%.3. Imaging methods and conditionsAll of the patients underwent PET/CT scans after fasting at least 6 hours prior to examination, detect blood sugar, weighed, measuring height are required before injection imaging agent.18F-FDG with the dose of 5.5MBq/kg was administrated intravenously via a T tube. After about 60 minutes of relaxed rest in a supine position in dark rooms without visual or acoustic stimulations, the patients were asked to void and were then placed into the PET/CT scanner for image acquisition. The image acquisition included non-enhanced CT scan and PET scan covered the range from the head to the middle thigh, if necessary, add to sweep the lower limbs, collection of 6 to 8 beds.once more scan when the intestinal physiology absorb 18F-FDG too larger to identify the other disease.first of all,to take the CT scans,scan conditions for 140kv of voltage,160mA of current,0.75 of screw pitch,5mm of scan thickness,then take the PET/CT scan under the condition of keeping the checker positions, emission scanning 3min/beds.Patients remain calm breathing in place to ensure the match PET and CT images.after the completion of collection,the images were reconstructed by using the dedicated computer oerkstation of PET/CT.4. Image reconstruction and fusionPET images were reconstructed by using a standard iterative algorithm (ordered subset expectation maximization) with CT data being used for attenuation correction. The CT images were reconstructed by using a standard method.The thickness of each slice of PET and CT after reconstruction was 4.25mm. The acquired images of PET and CT were sent to the Xeleris (GE Medical Systems) workstation for image registration and fusion.5. PET/CT Image analysis5.1 Qualitative analysis PET, CT and PET/CT images were interpreted independently by three experienced senior physicians of nuclear medicine and three experienced senior physicians of CT diagnosis. After visually examining all images on the workstation, the reviewers reached a final diagnosis based mainly on fusion images of PET and CT. Any initial difference of opinion was resolved by consensus.5.2 Diagnostic criteria for 18F-FDG PET/CT of IBDMain observed target: ①the lesion site of the intestine;(2)the bowel wall was thichening, or not;③with or without the 18F-FDG uptake of intestine was high;④enteric cavity was narrowing,or not;⑤parenteral lesions,including whether the outside of intestine have effusion,the lymph nodes were increased around of mesenteric vessel,and has been forming fistula or intra-abdominal abscess. Diagnostic criteria for 18F-FDG PET/CT:segmental or successional high uptake of bowel wall,and the 18F-FDG uptake degree of lesions is higher than the around of normal tissue.CT show the bowel wall was thichening in the corresponding place,and the thichening of the range is more than a intestinal segment,with or without enteric cavity narrow,outside of intestine inflammatory effusion,fistula or intra-abdominal absces,lymph nodes around of mesenteric vessel,and so on.After excluding the physiological uptake,cancer,tuberculosis,and other disease considering IBD;If CT show the bowel wall was diffuse thichening and the range more than a intestinal segment,with outside of intestine inflammatory effusion,fistula or intra-abdominal abscess,lymph nodes around of mesenteric vessel,and so on,even if bowel wall without a high F-FDG uptake,also can consider IBD.5.3 The active level judge of IBDExcept physiological uptake,the 18F-FDG uptake is significantly higher than the surrounding tissues,with the inflammatory exudation outside of corresponding lesions intestinal segment, the bowel wall thickening,density is uneven,especially visible stratified contrast-enhanced by CT,and consider active stage,otherwise consider stable stage.5.4 Semi-quantitative AnalysisLesion with abnormal 18F-FDG uptake was identified by three experienced senior physicians of PET/CT. The maximum standardized uptake value (SUVmax) was calculated automatically by the workstation by setting the regions of interest (ROI) on the lesion.6. The clinical diagnosis and staging of IBD6.1 Endoscopic examination obtainsing the pathology results by digestive department doctor operating colonoscopy,keeping record intestinal lesion manifestation and then diagnosis:(1) the site of the intestinal lesions;(2) the nature of the intestinal lesions, such as hyperplasia,ulcer of intestinal mucosa, or narrow, etc.The time interval of Endoscopic and 18F-FDG PET/CT examination was less than 2 weeks.6.2 Diagnostic standard CD and UC diagnostic were used to reference the consensus opinion of our country about inflammatory bowel disease:considering the IBD that must be look at clinical manifestations, colonoscopy, imaging examination histopathologic results and to comprehensive analysis before diagnosis.6.3 Clinical type UC included first episode type,chronic recurrent type,chronic continuous type,fulminant type.CD can be divided into mild,moderate and severe according to severity.7. Statistical analysisStatistical Package for the Social Sciences (SPSS) 17.0 (SPSS Inc., Chicago, IL) was used for statistical analysis. The thickness and SUVmax of the lesion was expressed as mean±standard deviation (X±S).75 cases of IBD patients, the relationship of activity and SUVmax of the lesion, using correlation analysis. The SUVmax in the UCs group and CDs group was used for two independent samples t test,so do the SUVmax in the active stage group and stable stage group, ROC curve drawing and about an index method is used to explore SUVmax appropriate boundary values. The lesion pathogenic site and relevance ratio of kinds of examination techniques in the UC group and CD group with 75 cases were tested by Pearson Chi-square. P<0.05 was considered statistically significant.[Results]1.18F-FDG PET/CT accurately deteced 65 patients with IBD, while located CT diagnosed 55 patients with IBD. The diagnostic sensitivities between 18F-FDG PET/CT and located CT were significantly different(86.7% vs.73.3%,χ2=4.167 P<0.05). The rates of qualitative diagnosis in 18F-FDG PET/CT and located CT were 70.6% and 68.0%, respectively. There were no statistical significance between them.2.The results of 18F-FDG PET/CT were compared with endoscopy.65 (65/75,86.7%) patients were detected by 18F-FDG PET/CT,10 (10/75,13.3%) patients had not been detected.69 (69/75,92.0%) patients were detected by endoscopy,6 (6/75,8.0%) pateents had not been detected.33 (33/75,44.0%) cases result of 18F-FDG PET/CT was agreement with endoscopy. (24/75,32.0%) cases result of 18F-FDG PET/CT was’t completely same,and 21 (21/24,87.5%) cases of them were more lesions diagnosed by 18F-FDG PET/CT then endoscopy,3 (3/24,12.5%) cases were more lesions diagnosed by endoscopy then 18F-FDG PET/CT. The lesions diagnosed by 18F-FDG PET/CT PET/CT were completely different from enteroscope in 8 patients (8/75,10.7%),2 (2/8,25.0%) cases of them were confirmed different pathological site, and negative diagnosed by endoscopy occurred in 6 cases (6/8,75.0%),which were confirmed by clinical and 18F-FDG PET/CT.Among the 65 patients diagnosed by 18F-FDG PET/CT,18F-FDG PET/CT detected 156 lesions, while enteroscope detected 120 lesions only. There were 40 patients showed diffuse high uptake of 18F-FDG in intestinal wall among the 65 patients, however, enteroscope showed mild mucosa injury in 18 patients.3.18F-FDG PET/CT accurately deteced 65 patients with 75 IBDs,Forty-eight of 65 patients detected by F-FDG PET/CT were proven clinically to be in active stage, and the rest were in stable stage. There was a linear correlation between CRP and SUVmax in active stage(r=0.453,P< 0.01),but in stable stage, CRP was not correlated with SUVmax(r=0.193,P>0.05).4. Forty-eight of 75 patients were in active stage by clinical diagnosis, and the rest were in stable stage.The SUVmax of active phase group (8.50±4.14)was significantly higher than that of the chronic phase group (5.39±2.63). Using a rut-off value of 6.35 on the ROC curve for determining active phase and chronic phase of IBD,the sensitivity, spetificity and accuracy was 68.8(33/48),77.8%(21/27)and 72%(54/75),respectively.5.17 patients of 75 IBDs underwent 18F-FDG PET/CT and MRI/ contrast-enhanced CT in the same term,13 (13/17,76.5%) cases of them were in active stage by clinical diagnosis, among which 10 (10/13,76.9%) cases with MRI/ contrast-enhanced CT were positive,and 3 (3/13,23.1%) cases were negative,only found intestinal wall incrassation 4 (4/17,23.5%) cases were in stable stage, all of them were negative. While 13 (13/17,76.5%) cases with 18F-FDG PET/CT were positive in all seven patients,among which all of them were in active stage. The relevance ratio of 18F-FDG PET/CT were significantly higher than MRI/ contrast-enhanced CT (p<0.05)[Conclusions]1.Most IBD were 18F-FDG positive,and easy to find,so 18F-FDG PET/CT has important clinical value for IBD.2.18F-FDG PET/CT may be helpful to comparable assess the activity of IBD. It was a supplementary diagnosed tool to detect lesions under the epithelium of bowel, which were often false-negative in enteroscope examinations.It is valuable to guide clinical treatment.3.18F-FDG PET/CT is more easy to find the IBD than MRI/contrast-enhanced CT,most of all it is valuable for identifying the activity evaluation of IBD,it can discover the mild lesions which MRI/contrast-enhanced CT can’t.