Objective To explore the radiation dose from body γ-knife treatment to the nontargeted region's sensitive organs before and after shielding.Methods 20 patients suffering tumors less than 5 cm were selected.Calibrated thermoluminescence dosimeters (TLD) were placed above the sensitive organs,such as lens,thyroid gland and sexual gland,to measure the radiation dose received before shielding.Different plans were prepared for the patients with lung and renicapsule tumors using calibrators of different size.Radiation dose was measured by the aid of water phantom.For selected lungtumor treatment plan,the radiation doses were measured at the same location on the water phantom shielded with and without 1,2 and 4 cm lead,respectively.Results The maximum doses were 1 023.3 mGy for lens,1 235.7 mGy for thyroid gland and 1 176.8 mGy for sexual glands after treatment,respectively,being higher on the left site than the right.The radiation doses to the sensitive organs were higher for the water phatom with more tartgted points,decreasing by 55％-91％ after being covered with 1,2 and 4 cm lead shieldings.There were significant differences in doses received before and after lead shielding (t =14.4,12.9,13.3,P ＜ 0.05).Conclusions In the course of body γ-knife treatment,the additional factors would increase the dose to the sensitive organs.Therefore,it is necessary to provide lead shielding protection to the teenagers and adults with fertility when they undergo body γ-knife treatment.Trial registration Chinese Clinical Trial Registry,ChiCTR-OOC-16008259.

OBJECTIVETo study the efficacy of B1 field shimming technique and evaluate the specific absorption rate (SAR) in ultra-high field magnetic resonance imaging (MRI) for MRI-guided high-intensity focused ultrasound (HIFU).

METHODSAn electromagnetic model of the female pelvis with a temperature gradient was established. B1 field homogeneity and local SAR were simulated and calculated using regular and optimized B1 shimming coefficients.

RESULTSThe maximum local SAR reached 10.24 W/kg, which exceeded the safe threshold of 10 W/kg, as calculated using regular B1 shimming coefficients in the normal model. Using the optimized B1 shimming coefficients, the maximum local SAR of the tissue was 9.65 W/kg, which was below the safe threshold.

CONCLUSIONThe temperature distributions in the body generated by ultrasound energy need to be considered in ultra-high field MRI-guided HIFU surgery. The proposed optimized B1 shimming strategy based on the temperature gradient can be used to control the local SAR levels.

Female ; High-Intensity Focused Ultrasound Ablation ; Humans ; Magnetic Resonance Imaging ; Pelvis ; Ultrasonic Therapy

BACKGROUNDS: Cardiovascular disease (CVD) remains the leading cause of deaths nationwide. However, little is understood about its temporal trend and corresponding influence on longevity improvements. We aimed to describe the updated tendency in CVD mortality and to quantify its impact on life expectancy (LE) increase in China. METHODS: All-cause mortality rates were calculated with population sizes from the National Bureau of Statistics and death counts from the National Health Commission. We estimated CVD mortality rates by allocating age- and sex-based mortality envelopes to each CVD subtype based on its proportion derived from the Disease Surveillance Points system. The probability of CVD premature deaths and LE were calculated with life tables and we adopted Arriaga's method to quantitate age- and cause-specific contributions to LE gains. RESULTS: During 2013 to 2018, the age-standardized mortality rate of CVD decreased from 289.69 (95% confidence interval [CI]: 289.03, 290.35)/100,000 to 272.37 (95%CI: 271.81, 272.94)/100,000, along with a decline in probability of CVD premature deaths from 9.05% (95%CI: 9.02%, 9.09%) to 8.13% (95%CI: 8.10%, 8.16%). The gap in CVD mortality across sexes expanded with more remarkable declines in females, especially for those aged 15 to 64 years. Among major subtypes, the probability of premature deaths from hemorrhage stroke declined fastest, while improvements of ischemic stroke and ischemic heart disease were limited, and there was an increase in stroke sequelae. LE in China reached 77.04 (95%CI: 76.96, 77.12) years in 2018 with an increase of 1.38 years from 2013. Of the total LE gains, 21.15% (0.29 years) were attributed to reductions of CVD mortality in the overall population, mostly driven by those aged >65 years. CONCLUSIONS The general process in reducing CVD mortality has contributed to longevity improvements in China. More attention should be paid to prevention and control of atherosclerotic CVD and stroke sequelae, especially for the elderly. Working-age males also deserve additional attention due to inadequate improvements.
Aged ; Male ; Female ; Humans ; Cardiovascular Diseases ; Life Expectancy ; China/epidemiology* ; Disease Progression ; Stroke ; Cause of Death