| BackgroundIn recent years, in China, with the improvement of people’s living standards, changes in lifestyle and diet habits of the public and the incidence of coronary heart disease (CHD)rate and mortality rate showed a trend of increasing year by year and age of onset showed younger phenomenon, now has become to seriously affect the residents health status and quality of life is one of the major diseases, especially the coastal economically developed areas more conspicuous. At the same time, people’s attention to their health and the promotion of China’s national health insurance policy, take the initiative to the hospital for treatment of patients with coronary heart disease is also more and more. At present, according to the severity of coronary heart disease, can be used to treat a method to have:drug treatment, interventional therapy and surgical coronary artery bypass grafting (CABG), which by interventional treatment of coronary artery stent implantation is commonly used in the patients with severe, so in recent years, to accept coronary vein stent implantation in the number of patients also showed increased year by year and the youth oriented tendency. Patients with coronary stent implantation will face several problems which have to be considered such as:stent patency, oral anticoagulation drugs, regular review of blood pressure, blood lipids, heart function assessment, etc.. Whether the stent restenosis is the primary consideration, if the stent restenosis may lead to some patients in the postoperative period of time will still have symptoms of coronary heart disease, and even the crisis of life. At this time, in the clinical, the patient’s coronary stent restenosis to make accurate judgment is very important, but also the future of the main basis for the corresponding treatment.At present can be used clinically to auxiliary examination method have five: ultrasonography (UD), coronary angiography (CAG), myocardial perfusion imaging (MIP), magnetic resonance imaging (MRI), multi-slice spiral CT angiography (CTA). Ultrasonography is noninvasive, cheap and convenient, but the coronary artery showed resolution limitation, which is difficult to distal vascular display; coronary artery angiography can show stent patency and hemodynamics, and the evaluation and treatment of heart function and spatial resolution, but its existence has certain restrictions for some complex parts of the lesions, it is difficult to make accurate diagnosis, and during angiography, the patients received large dose radiation; radionuclide myocardial perfusion imaging diagnosis of myocardial ischemia, coronary artery stent restenosis is only a good prediction, according to the aggregation and ventricular wall motion in myocardial nuclide, inference prediction of likely vascular stenosis, provide a reference for clinical treatment purpose, but myocardial perfusion imaging is an indirect imaging, can not directly display Stent graft cavity; nuclear magnetic resonance (NMR) no radiation damage, high resolution of soft tissue, blackblood technology can display the coronary artery wall, lumen and plaque, but there are also only can display with a diameter of more than 2mm vascular (this is the defects due to the limit of the spatial resolution) and nuclear magnetic resonance still exist distal vascular lumen display poor, check for a long time, the shortcomings of high cost, also due to the influence of metal artifacts, nuclear magnetic resonance imaging of coronary artery stent restenosis diagnostic images have deleted signal, can not clearly show the cavity of the stent. Multi-slice spiral CT (MSCT) created a noninvasive cardiovascular imaging is the first of its kind, scanning technology conditions gradually mature, so check the speed rapid increase, time-resolved and space resolution also increased significantly, scan time gradually shortened, patients received a radiation dose has been in reducing, simple operation, is on the clinical use of the very widely used for assessment of coronary stent restenosis preferred way. This study probes into the CTA internal correlative measuring parameters, including different algorithm produces dose and image quality analysis; and through and CAG diagnosis test method from the clinical diagnosis of coronary artery in stent restenosis of the sensitivity, specificity, positive predictive value, and negative predictive value of the four aspects of CTA evaluation value.ObjectiveTo evaluate the clinical application value of 256 slice spiral CT in evaluation of stent restenosis after coronary stent implantation, and to analyze and evaluate the radiation dose.Materials and Methods1. objectData sources in the Zhujiang Hospital in January 2013 to 2015 December 255 cases of percutaneous coronary interventional therapy (PCI) after stent implantation in patients with; in 255 patients with 84 cases of patients with symptoms of severe, such as chest tightness, palpitation, pain, angina pectoris, etc which had before the heart, hence the coronary angiography (CAG)2. equipmentsPhilips 256 slice spiral CT brilliance 256 iCT, Philips healthcare, Philips Medical angiography X-ray machine Allura CV20.3. Experimental groupingCollection, acquisition and analysis of the influence of different scanning on image quality and radiation dose of the experimental group:according to the CT scan mode (forward-looking gated acquisition; retrospectively gated acquisition and image reconstruction methods (iterative method of idose; filtered back projection (FBP),255 cases of patients were divided into four groups (A, B, C, D), group A as the iterative algorithm (idose) reconstruction and forward-looking gated acquisition; B group was filtered back projection (FBP) algorithm to reconstruct and forward-looking gated acquisition; group C as the iterative algorithm (idose) reconstruction and retrospective gating; D group is filtered back projection (FBP) algorithm to reconstruct and retrospectively gated acquisition.4.scanning modesThe patient supine, normal scanning, scanning and recording electrocardiogram, scanning direction for head foot direction. By using non-ionic contrast agent and Ultravist 370 iopromide (Ultravist)(Schering AG, Germany) by elbow vein double tube high pressure syringe placed in a forearm vein of 18G trocar through injection, injection rate for 4.5-5.OmL/s injection after fill at the same time injection 20ml of saline into right ventricle to eliminate the artifacts. More than 100 BPM, heart rate before the examination subjects using beta blockers reduce heart rate.CT scanning for aortic (AO) to the root of the left phrenic 5cm, total length 13cm, the automatic trigger acquisition mode, trigger points at the level of the Ao root, the trigger threshold for triggering the CT value 150HU. According to the difference of heart rate in patients with selected review retrospective ECG gating and prospective ECG gated scanning mode, heart rate greater than 75 BPM retrospective gating of scan acquisition mode, less than 75 BPM used prospectively gated scan acquisition mode. Scanning parameters:tube voltage 100kV-120kV, tube current 340mA-700mA and beam alignment 0.625mm, X-ray tube rotation time 0.27s,128 rows detector, matrix 512x512, FOV200-210mm, pitch (pitch) of 0.16, pre gated by axial scan mode were collected. Patients received radiation dose:CT dose length product (products dose-length, DLP).The effective radiation dose (ED) was calculated by the formula DLP X k (k=0.014mSv. mGy-1 cm-1)5. image processing and quality scoreIncome image layer thickness to 0.30mm, reconstruction interval of about 0.45 mm and reconstruction method with conventional filtered back projection algorithm (FBP) and recent applications of the iterative algorithm (idose), choose motion artifacts at least phase reconstruction of volume data, income data transmitted to the workstation Philips (Philips IntelliSpace portal v.4.0.410004), and by maximum intensity projection (MIP), multi planar reconstruction (MRP) and volume rendering (VR) etc. display of coronary artery stent location, shape and cavity. Give score of 255 cases of subjects of image quality and image quality by 4 points:1-image quality is excellent, the stent lumen clear display, artifact free; 2, good image quality, the stent lumen display fair, a small amount of artifacts, does not affect the diagnosis; 3 points and image quality, the stent lumen display, artifacts, does not affect the diagnosis; 4, poor image quality, unable to observe the stent lumen.6. diagnostic test evaluation indexThe clinical diagnosis and the dose of 98 stents in 84 patients with CTA and CAG were analyzed and compared. CTA and CAG clinical diagnosis of stent patency, and then the number of stents, the calculation of the sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy of CTA diagnosis of stent restenosis. The dose of CTA and CAG were collected in 84 patients, and the difference between the dose and the dose was analyzed.7. quality controlInstruments and equipment:used in the study of Philips 256 slice spiral CT and Philips Medical angiography X-ray machine are formal route through the procurement of equipment, to my unit performance acceptance work each year of detection performance, were in the State stipulated range. The inclusion and exclusion criteria for personnel:December January 2013 to 2015 in Zhujiang Hospital of Southern Medical University Hospital of coronary artery stent implantation and successful acquisition to patients with coronary angiography images. Exclusion criteria for hospitalization were not carried out CT angiography of coronary artery patients (atrial fibrillation and heart failure or of iodine contrast agent allergy, severe arrhythmia, severe respiratory function damage and not with the breath training is not in this study) and although the CT angiography of coronary artery, but image quality did not reach requirement of patients. To compare the difference between the CTA and CAG, serious symptoms, such as chest tightness, palpitation, heart pain, angina pectoris clinical manifestations of 84 patients, these patients and examination of CTA and CAG.Patients with oral metoprolol in patients with heart rate more than 100 BPM (beta-blocking) 50mg decreased heart rate. All patients were given respiratory training before examination. Renal insufficiency (Fm creatinine greater than 120mmol/L) using Visipaque 320 (Iodixanol Injection) (GE) as contrast agent. Image quality assessment:the image quality score by two experienced imaging diagnosis doctors with double blind analysis and scoring, the doctor asked for the intermediate title, engaged in cardiac CT angiography diagnosis for more than 5 years. Two people sentenced to a consensus that the adoption of its scoring standards, the score is not consistent with the two doctors together to discuss, to obtain a consensus of opinion after the record of its score.8.statistical and computational methodsStatistical analysis was performed using SPSS 20 software. Measurement data of the normal test obey normal distribution, described in x±s, two samples were compared by t-test, between groups (A, B, C, D) dose compared with single factor analysis of variance; variance not neat using Welch test, pairwise comparison with tamhane’s T 2 test. Between the different groups (A, B, C, D) between the image quality score, score (1,2,3,4) was used to compare the difference of independent samples of non parametric Kruskal Wallis rank sum test; diagnostic test index by using the expressed in percentage (%). Test level alpha=0.05. Non parametric test of the two two comparison of the test level using boffironi correction value alpha =0.05/6.Results1. basic information of cases:Of the 255 patients,173 were male and 82 were female. The average age was (31～83) years old. The average age was (56+7.1) years. The clinical symptoms, patients have different degree such as palpitation, chest tightness, chest pain, angina, etc..2.the results of image quality and the exposure doseAccording to the preset standard, the parameters of the scanning parameters are set on the 256 layer spiral CT of PHILPS, including the voltage and current of the tube. All patients examined use instant ECG heart rate display, more than 75 BPM patients by retrospective gating of scanning, less than 75 beats/min with a prospective gating scan, subjects using iterative algorithm (idose) and filter back projection algorithm (FBP) reconstruction.Among the 255 cases,239 cases were collected successfully, accounting for 93.7% of all samples. There were 16 cases of the patients who could not be used for image analysis, accounting for 6.3% of all samples.A total of 255 patients were placed 328 stents, with an average of 1.3 implants.328 stents in the CTA images can clearly show that there are 306, accounting for 93.3% of the total number of stents,22 pieces of false shadow can not be clearly displayed, accounting for 6.7% of the total number of stents.In 255 patients,84 patients due to subjective clinical symptoms are more serious, such as the emergence of angina and other reasons, so at the same time the coronary angiography (CAG) and stenting and coronary CT angiography (CTA) intervals from 1 day to 6 years range. In 255 cases,84 cases (98 stents) were examined by CTA and CAG, all stents were evaluated, and the stent lumen showed clearly. CAG display stent lumen patency for 79, stent restenosis for the 19. CTA display stent lumen patency for 80, stent restenosis for the 18.3. Image quality analysis of four groups of patients with CTA scanThe CTA image quality of 255 patients who had been divided into groups of A, B, C, D four groups was evaluated, and the results were shown below:Image quality analysis shows that:A, B, C, D group differences in image quality without statistical significance (x2=0.957, P> 0.05); 1,2,3,4 scores between the differences have statistical significance (x2=179.13, P< 0.05), two two comparison:1 points and other scores between; 2 points and 3 points,4 points difference between all have statistical significance (Z=9.978,7.589,6.463,7.936, 6.679,4.162, P< 0.05/6)4.CTA diagnostic test analysisCTA and CAG diagnosis result analysis:in 84 patients also received CTA and CAG were 98 stents image for clinical diagnosis, diagnosis of stent patency:CAG for 79 medals, CTA for 80 pieces, diagnosis of stent restenosis:CAG for 19 gold medals, CTA 18 medals; CTA in the diagnosis of stent lumen restenosis sensitivity was 94.7%, specificity was 100%, positive predictive value was 100%, the negative predictive value was 98.8%. The diagnostic accuracy rate was 98.9%.5.results of radiation doses of four groups of patients were scanned at CTAIn 255 cases of subjects in 16 cases because of the heart rate, breathing, arrhythmia or patient motion and lead to image quality of 4 points, can not be used for clinical diagnosis and evaluation.The results of variance analysis showed that there were significant differences in the radiation dose between A, B, C, D four groups (F=3936.43, P< 0.05), among which the A group was the lowest, while the D group was the highest. Two two comparison shows:A and A, B and C, A and D, B and C, D and B, C and D are statistically significant differences (P< 0.05)Analysis of radiation dose in 6 patients with different scanning modes and reconstruction methods:A group:using the iterative algorithm (iDose) reconstruction method and the use of prospective gated acquisition. There were 68 cases in this group, the average number of DLP (CT dose length product) was (196.05.5 ± 2.87) mGy X cm, the effective radiation dose ED was (2.37 ± 0.33) mSv.B group:the use of filtered back projection (FBP) algorithm to reconstruct the way and with a prospective gated acquisition. There were 57 cases in this group, the average number of DLP (CT dose length product) was (218.96 ± 4.51) mGy X cm, and the effective radiation dose ED was (3.07±0.48) mSv.C group:using iterative algorithm (iDose) reconstruction method and using retrospective gating acquisition. There were 79 cases in this group, and the DLP (CT dose length product) was (664.88 ± 5.15) mGy ×cm, and the effective radiation dose ED was (9.31 ±0.64) mSv.D group:using filtered back projection (FBP) algorithm reconstruction method and using retrospective gating acquisition. There were 51 cases in this group, and the DLP (CT dose length product) was (928.99 ± 9.33) mGy ×cm, and the effective radiation dose ED was (13.01 ±0.93) mSv.An effective dose of four groups of patients to accept the results, by the results of the analysis of variance showed that a, B, C, D four groups of patients with effective dose difference was statistically significant (F=3936.43, P< 0.05), which a group of effective dose lowest group D, and the effective dose is the highest. Further two two comparison showed that:A group and B group, C group and D group; B group and C group, D group, C group and D group were statistically significant difference between the patients (P< 0.05)ConclusionsThe iterative algorithm (idose) reconstruction and the use of forward-looking gated coronary angiography (CTA) inspection, can get to meet the demand of the clinical diagnosis of image quality, and enable subjects to take the lowest doses of radiation. Therefore,256 slice spiral CT coronary angiography is a reliable, low radiation dose, the convenient operation and evaluation of the PCI bracket restenosis inspection method can clearly show the cavity of the stent and to PCI with stent implantation after follow-up has great clinical value, is in the treatment of non coronary artery stent implantation of in stent restenosis after evaluating the preferred way. |
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