The Clinical Research Of HDCT With ASIR Reconstruction In Intestinal Imaging

Background and Purpose:Samall intestine is the longest part of the digestine tract, and its accounted about 75% of the total length of the gastrointestinal tract,and its Starting at the antrum secluded entrance, issued the ileum distal to the ileocecal junction.the most important places for human food digestion and nutrient absorption of various digestive juices in the small intestine in chymedecomposition, afterdigestion and absorption of residues excreted. Small intestinal disease is very common, some were intestinal primary disease, and some were secondary disease. Once the small intestine diseases, It can cause digestion and absorption barriers, some of the primary disease can even cause other systems of the body a series of related symptoms. With the improvement of living standards of the people and the way people work, life style and dietary changes in the structure, gastrointestinal diseases showed a rising trend, the small intestine disease incidence is also increasing. But the lengthy small intestine and mutual folding of the physiological and anatomical characteristics, the cause of small bowel diseases diagnosis method is relatively scarce, and in the diagnostic of imaging, the inspection of small bowel diseases has been a blind spot. There are several common intestinal diagnostic methods such as oral barium small bowel imaging,small bowel barium double contrast small bowel magnetic resonance imaging, MRI and multislice spiral CT enterography imaging methods, In recent years, the clinical use other methods, such as double balloon enteroscopy and small bowel capsuleits own advantages and disadvantages of endoscopy, a variety of inspection methods. The main subject of multislice spiral CT enterography imaging method is to diagnose the small bowel disease, in order to observe its effect. Conventional small bowel contrast need to do the whole abdomen scan, so the effective radiation dose for each position up to 11.7 mSv, (single serial scan), On the other hand in order to increase the sensitivity and specificity of the lesions showed increase in the detection of positive lesions rate, small intestine CT angiography is often necessary for dual-phase or three scanning of the whole abdomen (unenhanced added enhancements), which will undoubtedly further increase the scanning radiation dose. And the dose of ionizing radiation in recent years has more and more attentionned for human. So my topic select whom body mass index in less than normal, and clinical suspicion of intestinal diseases and some people do healthy subjects, expand the small intestine contrast study with Gem CT low-dose scanning, combined with the latest iteration of the Adaptive Statistical Iterative Reconstruction technology (ASIR) technology designed to explore the clinical value of small bowel disease with the low dose scanning.Materials and methods:(1)General InformationSelect 120 patients(male71 49 female, age 16-78 years old, average 39.7 years) from April 2010 to March 2011 in our hospital or outpatient who visits in patients and suspected has small bowel disease and randomly divided them into three groups (A, B, and C), And all of them made full abdominal CT scanning, The average age of group A patients (40.8±15.4Y), group B patients with average age (37.6±14.1 Y), group C patients with average age (36.9±16.8Y)). Group A conventional-dose scan, B and C the two groups for the experimental group, respectively, take low-dose scan. All patients included in this subject body mass index (body mass index, BMI= body mass/height 2)<25Kg/m2. All patients had no intravenous bolus injection of contrast agent to enhance scans contraindications, and accept the HDCT small bowel imaging, to complete the entire scanning process.(2) Prepare in advanceTwo days before the test, all patients with small bowel imaging needs of low-fat, low fiber, liquid diet, check the first 8-12 hours of oral laxatives, fasting before the test meal. Ask the patient a history of allergies, Patients who have a history of glaucoma, prostatic hypertrophy, embolism, and dysuria were banned intramuscular injection of hydrochloric acid 654-2 injection, the patient if the symptoms of acute intestinal obstruction can not oral contrast to those who do not do this check.(3) Equipment and scanning methodsWith GE gem CT (Discovery 750HD) models, scan range from the top of diaphragm to the pubic symphysis. Scanning technical parameters fixed noise index, a fixed tube voltage 120KVP, automatic mA range (100-600mA), pitch 1.375:1, collimator width of 128 X 0.625mm. Different groups of noise (noise index, NI) settings are as follows:A, B, C noise NI by default 9,12,14; in group A with conventional-dose scan, group B and group C with low-dose scan, on the basis of the original scan data, respectively, an image of the group B patients with 50% ASIR reconstruction image of the group C patients with 70% ASIR reconstruction, respectively, two different sets of images, denoted B50 is C70, reconstruction slice thickness 5mm, interval of 5mm.The sweep of the scanning sequence level plus dual-phase enhanced scan, the cubital vein injection of nonionic contrast agent to 3.5 ml/s,100ml/bottle, dose 1.5ml/kg. After injection, aortic CT value 200HU automatically trigger the arterial phase scan (diagnostic delay time 5s), generally 25s～30s; 40s vein phase scans in the arterial phase on the basis of delay, usually 65～70s. Retrospective image slice thickness 0.625mm, ADW4.4 workstation deal with reconstruction after the necessary number of, for example, multi-planar reconstruction (Multi Planar’s Reformation MPR), maximum intensity projection (Maximum of Intensity Projection is the MIP) and volume rendering (Volume Rendering, VR), in order to meet the diagnostic needs.(4) Image qualitySubjective evaluation:Each set of images includding the reconstructed image transmitted to the PACS, shielding every patients all scan parameters and related information. Respectively choose the same level reconstruction sequence to compare the image quality for the same patient, Select the approximate level of comparison for different patients, For example,the liver parenchyma select the second hepatic hilum, small intestine and intestinal fat image monitoring select the waist 1 vertebral level. A fixed standard abdominal window width and window level. Be judged on image quality by 2 independent senior radiologists for disease diagnosis, differences of opinion, through consultation, to reach agreement. Quantitative evaluation of image quality based on the anatomical structure, the observation of abdominal parenchymal organs (liver), the small intestinal mucosa, small intestine showed the structural clarity and noise of the intestinal weeks fat and mesenteric vessels. On image quality with a 5-point rating:unqualified, can not meet the diagnostic requirements for 1 minute; less able to meet the diagnosis of the basic requirements, but can not satisfy the differential diagnosis of the need for 2 minutes; in general, to meet the diagnostic requirements for 3 minutes; good to meet the diagnostic requirements for 4 minutes; outstanding, to meet the diagnostic requirements for 5 minutes. Quantitative score of≥3 points was considered the image quality to meet the clinical needs.Objective evaluation:measurement of each group of the liver, spleen substance and mesenteric fat regions of interest (of VOI:100mm2) CT value and its standard deviation, standard deviation instead of the objective image noise (SD), and calculate the signal-to-noise ratio (SNR), contrast letter noise ratio (CNR). Appropriate statistical analysis of the obtained data.(5) The radiation dose:Recorded three groups of patients received radiation parameters:volumetric CT dose index (CT dose index voulme, CTDIvol), dose-length product (a dose length product, DLP) is generated by the machine automatically calculate and estimate the effective dose (Effective Dose, the, ED), the formula ED=DLPX0.015.(6) Statistical methods: Use SPSS 17.0 statistical software, measurement data are expressed(x±s).The difference between the groups A, B, B50, C, C70 set of CT values, the noise (SD) signal-to-noise ratio (SNR), contrast to noise ratio (CNR) using single-factor analysis of variance or Kruskal-Wallis rank sum test, The measure between the number of pairwise comparisons of LSD-t test or Bonferonni correction test; The B、C and B50. C70 between the two sets of the original image, noise (SD the differences between groups comparison), the signal-to-noise ratio (SNR), contrast to noise ratio (CNR) using independent samples t test; About A、B、C three groups of age, body mass index (BMI), CT dose index (CTDIvol) dose length product (DLP), the effective dose (ED) measurement data indicators of differences in the single factor analysis of variance; Two physicians using a five-point scale to assess the image quality and consistency in the evaluation of interobserver Kappa test,≥0.75 on behalf of consistent good,0.4-0.75 on behalf of the consistency,and<0.75 is less consistently.Results:(1) three groups of patients, the average height, body mass index were no significant differences (P> 0.05). Contrast between the three groups of the original image excellent score group differences, pairwise comparisons of group A and group B, group A and group C, group B and group C there were significant differences. No significant pairwise differences between the two sets of images in group A and re-B50, C70 group, and the score results can meet the diagnostic needs. Contrast to noise (SD) between the signal-to-noise ratio (SNR), contrast to noise ratio (CNR) contrast were different between groups, pairwise comparisons of group A and group B, group A and group C, group B and the difference between group C were statistically significant, but no significant pairwise differences between group A, B50 and C70 group group. The image data group C noise, group A SNR and CNR values. Group A CTDIvol (14.07±2.19) of mGy, CTDIvol Group B (9.13±2.11) of mGy, CTDIvol group C (6.64±0.94) of mGy between the two groups statistically significant pairwise differences. Group B compared with group A (CTDIvol) and dose length product (DLP) were reduced by 35.11% and 34.23%, Group C reduced more for 52.81% and 56.08%, respectively.(2) the subjective rating of image quality, the two physicians’evaluation of group A, B50, and C70 group results can meet the clinical diagnostic needs, two physicians three sets of image evaluation of the consistency of medium (average Kappa value of 0.469). Accompanying NI values increased, the reduction of radiation dose, group A, group B, group C, three sets of image quality score, followed by decline in group A, the highest scores, group C the lowest score (liver parenchyma score of 2.7). Select a different region of interest of the differences in scores of the same score in the substance of the liver, spleen and other organs results of B, and C group compared with group A score significantly decreased, while the small intestine, the intestinal wall, mesenteric fat and mesenteric vessels display B, C, two sets of score compared with group A score has also been reduced, but the degree does not reduce significantly the substance of the liver, spleen and other organs. Image quality rating by the the ASIR renewal B50 group and the C70 group compared with group A are almost the same.(3) the small intestine of all subjects with CT angiography showed positive results of 78 cases, of which up to 21 cases of infectious diseases, tumors and tumor-like lesions of 19 cases,9 cases of vascular tumors and vascular lesions,7 cases of lymphoma, intestinal diverticula 5 cases of colon placeholder eight cases, liver adenoma, intestinal obstruction in three cases, two cases of rectal cancer, descending colon, lymphoma, colon cancer with liver parenchyma multiple transfer one cases, multiple intra-abdominal small stromal tumors one cases. Conclusion:(1) HDCT can in a stable image quality at the same time, greatly reduce scanning radiation dose.(2) ASIR Adaptive Statistical Iterative Reconstruction technology can reduce the noise rise adequately, restrain the artifact, improve the quality of image when the low doses scanning were taken.(3) Different ASIR reconstruction make the different value of the noise level for the image change.