| ObjectiveDual-source CT angiography on head and neck (CT angiography, CTA) is developed in recent years a non-invasive examination method of head and neck vascular lesions, how to fully apply the advantage of dual-source CT, CT radiation dose, which are using a minimum of head and neck vascular imaging is a problem to be solved, low doses of head and neck CT angiography is the future direction of development, so the research how to effectively reduce the radiation dose of head and neck CT vascular imaging will have important clinical significance.Study, head and neck artery stenosis caused by atherosclerosis is the main cause of brain, brain aneurysm is the most common reason cause bleeding in the brain, the case fatality rate up to 50%. The arterial lesions is discovered early, early detection, early diagnosis, early intervention is effective to prevent and improve the prognosis of head and neck vascular events and effective way. With mature CTA technology, head and neck CTA angiographic imaging has become a routine screening of high-risk vascular lesions in the crowd, especially in the neck artery stenosis and the diagnosis of intracranial aneurysms can replace DSA. Head and neck CT angiography can clearly show common carotid, internal carotid artery and vertebral basilar artery vascular images, willis ring, is widely used in head and neck vascular disease. At the same time, the radiation dose increasing brought by the CTA thought highly of by people more and more, how to reduce CT radiation dose has become one of the hot spot of current research. How to effectively reduce the radiation dose, is the focus of our medical imaging research of common problems. Now reduce the radiation dose of the main ways are:reduction of tube current and time of the product (mAs), lower tube voltage and increase the pitch method.This study was to explore the application of second generation dual-source CT alone, in view of the patients with normal body weight category, by adjusting the way of mAs, ensure the quality of diagnostic images, reduce the patients received effective radiation dose of CT. Research content includes the record of radiation dose was carried out on the data obtained and the subjective and objective evaluation of image quality of CT dose index, including volume dose length product, patients with head and neck artery CT value and image quality indicators for comparison and statistical analysis, clear the value of the second generation of dual-source CT in head and neck CTA.Methods40 cases of body mass index (BMI) in accordance with the world health organization (who) defined as normal weight category (BMI:18.5-24.9 kg/m2) the patients with head and neck CTA scanning, these patients were randomly divided into low dose or routine dose group, each group of 20 people. Using the second generation of dual-source CT in Siemens, on the head and neck is the first of a position as scanning, and then determine the scope of the scanning directly after dual-source enhancement scanning. Low dose group:2 tube A/B scan reference mAs set to 100/50 mAs; Conventional dose groups:2 tube A/B scan reference mAs keep 228/114 of the original mAs; Yu scan conditions are the same. Using Siemens special post-processing software "Inspace" image post-processing of two groups of patients, in order to better show the neck and intracranial arteries. Dual-source scan record low dose group and routine dose group of patients with radiation dose, the volumetric CT dose index (CT dosed index. The volume, CTDIvol) and dose length product (dosed length product, DLP). All patients’ images are the determination of the aortic arch, bilateral common carotid artery bifurcation, basal artery, bilateral siphon and bilateral middle cerebral artery M1 of CT value and SNR (signal-to-noise SNR) and contrast to noise ratio (contrast-to-noise CNR). Using two independent samples t test analysis and the data obtained from the objective evaluation of the image quality. Invite two experienced head and neck vascular diagnosis of doctors in the case of a double-blind, combined with cross-sectional images and MPR, CPR and MIP and VRT reconstruction image respectively on two groups of patients with image according to four points method to analyze subjective ratings. The Kappa score results consistency inspection two physicians.ResultsTwo groups of 40 patients were successfully completed the head and neck dual-source coronary CTA scanning, two doctors to image quality ratings of the two groups of patients with high consistency (Kappa value= 0.87). Low dose group of patients, on average, for image quality score (3.1±0.9), conventional dose group of patients with average for image quality score (3.3 ± 0.6) points, both there was no statistically significant difference (p> 0.05). Two groups of patient’s paragraphs of the blood vessels and comparing two CT value, SNR and CNR differences had no statistical significance (p> 0.05). The average effective radiation dose for patients with low dose group (0.94 ± 0.12 mSv), the conventional dose group of patients with average effective radiation dose for (2.19 ± 0.15 mSv), the difference was statistically significant (t= 29.251, p= 29.251).conelusionIn clinical work, with the development of CT equipment, under the premise that guarantee diagnostic image quality, adhere to the "can achieve reasonable as far as possible low dose* (as low as german-russian co-operation achievable, ALARA) principle. Each image doctor, technician must have profound understanding of the hazards of ionizing radiation, can’t put the good quality of CT images based on large amounts of radiation dose, CT radiation dose, reduce man-made factors to examinate the radiation injury of CT in the future development of the road a long way to go. Dual-source CT low-dose scanning in patients with normal BMI for head and neck CTA examination is feasible, does not affect the image quality, and the radiation dose can obviously drop, a drop of about 57.1%, worth clinical application and spread. |
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