Objective To investigate the clinical features of internal carotid steal syndrome. Methods The clinical manifestations, CT or MRI, digital subtraction angiography, and blood flow compensation in 6 patients with internal carotid steal syndrome were analyzed. Results Of the 6 patients, 2 had unilateral internal carotid artery stenosis, 4 had severe stenosis (in which 2 were on the left side, 1 was on the right side, and 1 was on both sides). The clinical manifestations of the patients with internal carotid steal syndrome were watershed infarction and transient ischemic attack. Four patients had posterior circulation ischemia and 2 had anterior circulation ischemia. Digital subtraction angiography demonstrated that collateral circulation was established in all the 6 patients. The anterior communicating artery, posterior communicating artery, and pial artery were the common compensatory vessels. Conclusions Internal carotid artery steal syndrome can be presented as anterior or posterior circulation ischemia, and the collateral circulation plays an important role in the compensation.

Objective To explore the direction value of endovascular pressure differences in endovascular management of subclavian steal syndrome (SSS).Methods Eleven SSS patients accepted endovascular management,admitted to our hospital from January 2016 to December 2017,were collected in this study.Before and after operation,pressure-sensing wire was used to measure endovascular pressure differences (mean distal stenosis pressure minus mean proximal pressure),digital substraction angiography (DSA) was used to assess the stenotic rate,transcranial doppler (TCD) was used to assess the steal degrees,and electronic sphygmomanometer was used to measure the systolic pressure differences between bilateral brachial arteries.The pressure differences before and after endovascular management were compared.Before operation,the relations of pressure differences with stenotic rate,steal degrees and systolic pressure differences between bilateral brachial arteries were analyzed.After operation,the relations of pressure differences with stealing and clinical symptom improvements were analyzed.The predictive values of pressure differences and residual stenosis in clinic success were compared.Results (1) After operation,the blood stealing disappeared and the clinical symptoms improved in 10 patients;although residual stenotic rate of one patient decreased obviously,blood stealing and clinical symptoms still existed after operation;the clinic success rate was 90.9％(10/11).(2) Pressure differences before surgery ([11.2±5.7] mmHg) were significantly higher as compared with those after the surgery ([2.5±5.3] mmHg,P＜0.05).(3) Before operation,pressure differences were significantly correlated with stenotic rate (r=0.757,P=0.007) and bilateral systolic pressure differences (r=0.701,P=0.016).Six patients had pressure differences of 6-9 mmHg,enjoying degree I and Ⅱ of stealing,and 5 patients had pressure differences ≥ 10 mmHg,enjoying degree Ⅲ of stealing.(4) After operation,pressure difference was 18 mmHg in one patient without clinic success,but pressure differences were ≤ 3 mmHg in 10 patients with clinic success.(5) Significant difference was noted between the two clinic success indexes (residual stenotic rate ≤ 30％ by DSA and pressure differences ≤ 3 mmHg,P＜0.05).Conclusion Endovascular pressure differences can reflect the hemodynamic changes before and after endovascular management;as compared with residual stenosis,it is better to predict the clinic success after operation;it is useful to guide the endovascular management in the SSS patients.

Compared with conventional radiotherapy fields, small field has unique dosimetry characteristics such as high dose gradient, charged particle imbalance, and dose effect caused by source occlusion. These characteristics increase the difficulty of dose measurement and thus the uncertainty of clinical dose measurement, far exceeding the requirement of < 5% measurement error in ICRU 24 report. In recent years, with the development of new radiotherapy technologies, the minimum radiotherapy field can reach the millimeter level, and the single irradiation dose of hypofractionated radiotherapy can exceed 6 Gy. The larger dose gradient at the edge of radiotherapy field requires higher accuracy of dose measurement, and accurate small field dosimetry technologies have gradually become a research hotspot in the field of precision radiotherapy. In order to ensure the high accuracy of measurement, this paper reviews the research on small field dosimetry worldwide, and summarizes the key points of small field dosimetry. In this paper, the characteristics of small field dosimetry are introduced, and the current small field dosimetry technologies and optimization methods are summarized, including the optimization of detector selection and detector sensitive volume. The field output correction factor technologies are analyzed. In view of the difficulty in small field dosimetry, this paper provides suggestions on dosimetry based on clinical needs and the characteristics of medical linear accelerators. Our suggestions provide a scientific reference for small field dosimetry in clinical practice in radiotherapy institutions, and facilitate the development of radiotherapy dose verification.