| Background and PurposeBackground and Purpose carotid artery diseases are closely related to the ischemic cerebrovascular diseases. As a result, accurate assessment of the ICA diseases is greatly significant to the prevetion of-ischemic cerebrovascular diseases. Presently,Digital substraction angiography (DSA) is thought as the "gold standards" in diagnosis of ICA diseases. However, DSA is charactered by invasion and expensiveness, which limit its using. With the advantage of simpleness, noninvasion and high diagnostic value, magnetic resonance angiography (MRA) or computed tomography (CTA) is also employed in detecting ICA diseases, but these two methods are also expensive and there exist some error in assessing luminal stenosis. High frequency linear-array probe is the first choice in examining ICA diseases, which is simple, noninvasive, repeatable, high accuracy, etc. However, High frequency linear-array probe can not detect blood flow in the distal extracranial ICA and the luminal intima. And stenosis, dysplasia, thrombosis and other diseases are frequently occurred in the distal extracranial ICA, which affect the quality of patients' life. Some scholars once using the low frequency convex array abdominal probe scanning, which is charactered by low frequency, strong penetration and wide scanning, often could obtain satisfactory image of the proximal ICA or more remote section, and could accurately assess the degree of luminal stenosis based on color flow filling and blood flow velocity. Yet the results showed that this method was ineffective for the section of ICA near the skull base and poor quality of two-dimensional image,spillover of color flow signal and so on affected its accurate assessment of the diseases. Other scholars using the intracavitary convex array probe placed in the neck scanning ICA through surface by the advantage of low frequency, wide fan, small probe and avoidance of mandible, could get a good two-dimensional and color flow images. Although this method overcame the disadvantage of flow signal spillover by low frequency convex array probe and other shortcomings, it still could not display the distal extracranial ICA, particularly the section near the skull base. Yassaka et al firstly reported scanning with an intracavitary convex array probe placed into the oral cavity could get a good two-dimensional and color flow image of distal extracranial ICA and skull base section, thereby enhancing the detection rate of middle and distal section ICA. As researches in this fields have not been reported,this study is to explore the feasibility of detecting the distal extracranial internal carotid artery by intracavitary convex array probe by Transoral Carotid Ultrasonogralhy, further assess the disease section and provide valuable clinical diagnostic information.Materials and Methods1 Subjects Patients aged 25-66 years old coming to Nanfang Hosipital for examination of ICA in the division of ultrasound are collected. There are total 15 males and 13 females, which averagely aged at 45±11 years old. Inclusion and exclusion criteria:healthy examiners which without heart diseases and cerebrovascular diseases history, without hypertension, diabetes and hyperlipidemia history were included in the study. Patients with intima-media thickness of common carotid artery (CCA)>1.0mm were excluded in this study.2 Equipment In this study, we used Philips IU22 CDFI, high frequency linear transducer for the L12-5,a frequency of 5.0-12.0MHz; abdominal low frequency convex array probe for the C5-2, a frequency of 2.0-5.0MHz; cavity convex array probe for the C8-4,a frequency of 4.0-8.0MHz; and used the equipment built in "prostatectomy" preconditions for scanning.3 Scanning methods In this study, using Philips IU22 CDFI,28 cases were examined by high frequency linear probe, low frequency convex array probe, convex array probe through the neck cavity surface, convex array probe through the oral cavity channels making ICA two-dimensional, color Doppler, and spectral Doppler imaging scanning. A key optimization technology (i-scan) was used to adjust the two-dimensional image, and scanning depth was designed as 4.0-5.0 cm (the depth can be adjusted according to patients' size).Color scale was adjusted as 14-17 cm/s and gain was middlely adjusted. We used i-scan technique to adjust Doppler frequency. Doppler beam and blood sampling angle was designed as<60°.4 Data processing and image analysis All data will be saved into the machine built-in disk after scanning and be analyzed. For convenience, worse ICA image displays in the detecting results were excluded. Coordinate with the the examiners' respiratory rate, left and right sizes ICA of examiners were detected differently by high frequency linear probe, abdominal low-frequency probe, intraluminal convex array probe through neck surface and intraluminal convex array probe through oral cavity, including the two-dimensional,color Doppler, spectral Doppler for horizontal, vertical standard section scanning. Measurement data including the ICA diameter, imaging length, peak systolic velocity (PSV), end diastolic velocity (EDV), resistant index(RI). Additionally, detection by intraluminal convex array probe through oral cavity also need the distance from ICA and oral mucosal surface. Different sets of data were got by three skilled sonographer had not been informed of the case history and three times measurements were averaged.5 Statistical analysis The data were processed by SPSS 13.0 statistical analysis package. Measurement data were indicated as x±s. Two samples were compared with the two-sample t test.Multiple groups samples firstly have an analysis of variance, then homogeneity of variance were conducted with the LSD method of multiple comparisons among groups. If variance is missing, the Welch testing and Dunnetts' T3 test were differently used processing an overall test and multiple comparisons. P<0.05 indicates statistical significance.ResultA high frequency linear transducer, low frequency convex array probe and convex array probe through the neck surface scanning imaging analysis on the ICA1.1 ICA diameter:The ICA diameter by high frequency linear array probe, low frequency convex array probe and convex array probe through the neck surface scanning was (0.55±0.09) cm, (0.55±0.09) cm, (0.56±0.11)cm,it showed no significant difference among three group (P=0.67).1.2 The length of the ICA:detection of high frequency linear array probe length, low-frequency convex array probe and the cavity surface convex array probe by the neck, the ICA observed in scanning length, respectively (2.17±0.57) cm, (4.46±0.67) cm, (3.13±0.58) cm, there is statistically significant difference among three group(P=0.01).The results showed that ultrasound imaging of ICA, the length of low-frequency convex array probe is greater than the cavity convex array probe, the cavity convex array probe greater than the high-frequency linear transducer.2 the feasibility analysis by convex array probe through the oral cavity test of the distal extracranial ICA.2.1 the success rate:Of 28 cases of subjects,26 patients completed the ICA-oral ultrasonography, the success rate of checking is 93.1%.2.2 image analysis of ICA:ICA convex array probe imaging of intra-oral scanning get a clear image of the distal extracranial ICA, the observed length is 3.55±0.17 cm. Combined with color Doppler flow imaging (CDFI) or power Doppler imaging (PDI),the vascular structures image of the distaLICA can clearly be shown.2.3 The diameter of ICA:The left and right sides inner diameter of the distal extracranial ICA by the convex array probe through the oral cavity ultrasound scanning were (0.46±0.15) cm, (0.46±0.14) cm, no significant difference between both (P=0.94).2.4 The length of the ICA:The left and right side distal extracranial ICA imaging length, by the convex array probe through the oral cavity ultrasound scanning were respectively (3.47±0.14) cm, (3.62±0.15) cm, no significant difference between the two (P=0.45).2.5 The blood flow velocity of ICA:The left and right sides PSV of the distal extracranial ICA, by the convex array probe through the oral cavity ultrasound scanning, were (76.3±12.7) cm/s, (72.6±10.9) cm/s, no significant difference between the two (P=0.460). The left and right sides EDV of the distal extracranial ICA, by the convex array probe through the oral cavity ultrasound scanning, respectively (37.8±10.8) cm/s, (33.6±11.4) cm/s, no significant difference between the two (P=0.380).RI of the distal extracranial ICA, by the convex array probe through the oral cavity ultrasound scanning, were (0.56±0.11),(0.54±0.13), no significant difference between the two (P=0.29). 2.6 The distance from the anterior surface of ICA to the oral mucosa:The distance from the anterior surface of ICA to the oral mucosa between the left and right sides, by the convex array probe through the oral cavity ultrasound scanning, respectively were(1.18±0.23)cm,(1.18±0.28)cm, no statistical comparison between the two school differences (P=0.16).Conclusion1 The convex array probe through the oral cavity scan can obtained a clear image of the distal extracranial ICA. Combined with CDFI or PDI, the distal vascular structure of the distal extracranial ICA can clearly indicated,it can obtained a good two-dimensional, color and Doppler flow spectrum spectrum,and provide valuable diagnostic information of ICA distal.2 Combined with high frequency linear array probe the proximal segment of the ICA, the distal extracranial ICA with intra-oral means of convex array probe scanning, can be shown a more complete whole section of extracranial ICA, It would have greater help to the ICA lesions and differential diagnosis diagnosis.3 When a patient is obesity, stubby neck or arterial bifurcation position is high, combination the convex array probe intra-oral cavity and neck surface scanning, it can be good for the whole section of two-dimensional, color and the Doppler frequency spectrum of ICA, can make up for poor penetration of high frequency ultrasound, the shortcomings of low frequency of the abdominal ultrasound resolution, while avoiding the ultrasound examination of extracranial ICA blind. Different types of probes and equipment conditions combined to better show the entire ICA.It can provide valuable information for assessment and clinical treatment.
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