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.

Objective:To improve the ability of aviation physicians and physical examiners in differential diagnosis of primary angiitis of the central nervous system (PACNS) and the level of aeromedical assessment by exploring the diagnosis and treatment of PACNS.Methods:The clinical diagnosis and treatment of a pilot with PACNS were reported and the related literatures were reviewed.Results:The clinical manifestation of the fighter trainer pilot was numbness of the left finger, and then gradually appeared numbness and weakness of the left face and left upper limb more than 1 month. The initial diagnosis was viral encephalitis and acute disseminated encephalomyelitis and the hormonal shock treatment was ineffective. The final diagnosis was PACNS. The patient′s condition was improved by cyclophosphamide shock treatment. Aeromedical assessment concluded that the pilot was temporarily grounded.Conclusions:Pilot with PACNS is rarely reported and easy to be misdiagnosed due to the clinical and imaging findings are lack of specificity. The aeromedical assessment of PACNS pilots should be individualized according to the severity of illness, type of aircraft and flight duties.

Objective:To improve the ability of aviation physicians and physical examiners in differential diagnosis of primary angiitis of the central nervous system (PACNS) and the level of aeromedical assessment by exploring the diagnosis and treatment of PACNS.Methods:The clinical diagnosis and treatment of a pilot with PACNS were reported and the related literatures were reviewed.Results:The clinical manifestation of the fighter trainer pilot was numbness of the left finger, and then gradually appeared numbness and weakness of the left face and left upper limb more than 1 month. The initial diagnosis was viral encephalitis and acute disseminated encephalomyelitis and the hormonal shock treatment was ineffective. The final diagnosis was PACNS. The patient′s condition was improved by cyclophosphamide shock treatment. Aeromedical assessment concluded that the pilot was temporarily grounded.Conclusions:Pilot with PACNS is rarely reported and easy to be misdiagnosed due to the clinical and imaging findings are lack of specificity. The aeromedical assessment of PACNS pilots should be individualized according to the severity of illness, type of aircraft and flight duties.

Objective:To summarize the diagnosis of a flying personnel with moyamoya disease.Methods:The clinical features of an aircrew with moyamoya disease which diagnosed in Air Force Medical Center were summarized and analyzed. Furthermore, the related literatures were reviewed.Results:The patient is a of 41-year-old male navigator. The Navigator usually felt dizzy in the training on the plateau. Also, his anti-anoxia ability was relatively weak. Digital subtraction angiography (DSA) showed the navigator was suffered from the moyamoya disease. Cerebral blood perfusion examination further confirmed moyamoya disease and indicated ipsilateral cerebral blood flow reduction. The conclusion of aviation medicine evaluation was flying qualification, and health level was class B.Conclusions:In most cases, the clinical symptoms of moyamoya disease are usually insignificant, and may not have cerebral infarction. So it’s easy to result in missed diagnosis. Therefore, more attention should be paid on aircrew’s cerebral blood perfusion examination upon his/her clinical symptoms.

Objective:To provide references for the diagnosis and aeromedical evaluation by analyzing the data of the flying personnel with cerebral arterial stenosis.Methods:The clinic and aeromedical evaluation data of the flying personnel, who were diagnosed as cerebral arterial stenosis when they hospitalized in Air Force Medical Center from September of 2009 to September of 2019, were reviewed.Results:Eight male flying personnel, aged 32-53 years old, were diagnosed as cerebral arterial stenosis. Five out of 8 flying personnel had the history of hypertension or smoking, and 2 suffered from arteritis. Among 3 neurological impairment cases, 1 was left carotid artery stenosis and 2 was middle cerebral artery stenosis or occlusion. Those 3 flying personnel were disqualified by aeromedical evaluation. The other 5 flying personnel without neurological impairment included 1 case of left subclavian artery stenosis with left renal artery stenosis, 1 case of intracranial stenosis of the left internal carotid artery, 2 cases of middle cerebral artery stenosis or occlusion, and 1 case of left anterior cerebral artery stenosis. Among them, 4 cases were diagnosed as silent brain infarction. The cerebral perfusion evaluation of those 4 cases indicated normal perfusion of the diseased vessels blood supply. Aeromedical waiver was decided upon the diagnosis as well as the considerations on the aircraft type they flied and their flight duty.Conclusion:The cerebral artery stenosis is living in flying personnel and atherosclerosis would be the main cause. Such clinical features as ischemic stroke or no neurological impairment may occur. The waiver should be considered according to the situations of cerebral perfusion and neurological impairment.

Objective:To summarize the diagnosis of a flying personnel with moyamoya disease.Methods:The clinical features of an aircrew with moyamoya disease which diagnosed in Air Force Medical Center were summarized and analyzed. Furthermore, the related literatures were reviewed.Results:The patient is a of 41-year-old male navigator. The Navigator usually felt dizzy in the training on the plateau. Also, his anti-anoxia ability was relatively weak. Digital subtraction angiography (DSA) showed the navigator was suffered from the moyamoya disease. Cerebral blood perfusion examination further confirmed moyamoya disease and indicated ipsilateral cerebral blood flow reduction. The conclusion of aviation medicine evaluation was flying qualification, and health level was class B.Conclusions:In most cases, the clinical symptoms of moyamoya disease are usually insignificant, and may not have cerebral infarction. So it’s easy to result in missed diagnosis. Therefore, more attention should be paid on aircrew’s cerebral blood perfusion examination upon his/her clinical symptoms.

Objective:To provide references for the diagnosis and aeromedical evaluation by analyzing the data of the flying personnel with cerebral arterial stenosis.Methods:The clinic and aeromedical evaluation data of the flying personnel, who were diagnosed as cerebral arterial stenosis when they hospitalized in Air Force Medical Center from September of 2009 to September of 2019, were reviewed.Results:Eight male flying personnel, aged 32-53 years old, were diagnosed as cerebral arterial stenosis. Five out of 8 flying personnel had the history of hypertension or smoking, and 2 suffered from arteritis. Among 3 neurological impairment cases, 1 was left carotid artery stenosis and 2 was middle cerebral artery stenosis or occlusion. Those 3 flying personnel were disqualified by aeromedical evaluation. The other 5 flying personnel without neurological impairment included 1 case of left subclavian artery stenosis with left renal artery stenosis, 1 case of intracranial stenosis of the left internal carotid artery, 2 cases of middle cerebral artery stenosis or occlusion, and 1 case of left anterior cerebral artery stenosis. Among them, 4 cases were diagnosed as silent brain infarction. The cerebral perfusion evaluation of those 4 cases indicated normal perfusion of the diseased vessels blood supply. Aeromedical waiver was decided upon the diagnosis as well as the considerations on the aircraft type they flied and their flight duty.Conclusion:The cerebral artery stenosis is living in flying personnel and atherosclerosis would be the main cause. Such clinical features as ischemic stroke or no neurological impairment may occur. The waiver should be considered according to the situations of cerebral perfusion and neurological impairment.

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.

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.