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

Objective:To explore the adjustment ranges of auto-segmentation contours for organs at risk (OAR) in patients with nasopharyngeal carcinoma and assess the dosimetric impacts of the contours from varying sources on radiotherapy plans.Methods:Twenty-five patients with early-stage nasopharyngeal carcinoma were investigated. Through expert delineation, deep learning-based automatic delineation, and atlas-based automatic delineation of their spinal cord, brainstem, optic nerves, optic chiasm, parotid glands, oral cavity, hypopharynx, and mandible, as well as expert correction of these automatic delineations, five structure sets were formed. Moreover, the contours delineated by experts (also referred to as the expert contours) of the target volumes and other OARs were copied into the images for subsequent research. The Dice similarity coefficients (DSCs) of the structure sets were calculated. Using the radiotherapy plans optimized based on expert contours as templates, the radiotherapy plans and dose distributions of all the structure sets were established. The expert contours and contours determined using automatic delineation and corrected by experts (also referred to as the corrected contours) were defined as clinical contours. Then, three research objectives were set: the dosimetric effects of inter-observer clinical contour variations, the impacts of contour variations on plan optimization, and the impacts of contour variations on plan evaluation.Results:The average DSC of the visual pathway was 0.62±0.10, lower than that of other OARs (0.86±0.04). After expert correction, the DSCs of contours obtained using deep learning- and atlas-based automatic delineation increased by 7.61% and 10.69%, respectively. For the dosimetric effects of inner-observer contour variations, the Dmax of the optic chiasm was the maximum (3.96±6.02)Gy, while the Dmean of the hypopharynx was the minimum (0.81±0.55 Gy). When the impacts of contour variations on plan optimization were assessed based on expert contours, the dose differences (Δ D) exceeding ±3 Gy accounted for 22%, 14%, 46%, and 42%, respectively for the spinal cord, brainstem, optic nerve, and optic chiasm and accounted for only 2% for other OARs. After expert correction, the Δ D between automatic and expert contours decreased, with Δ D exceeding ±3 Gy decreased by 16% and 14%, respectively for the optic nerves and optic chiasm. When the average distance of the overlap volume histogram (OVH) exceeded 3.5 cm, all Δ Dmax fell within ±3 Gy. When the average distance of OVH was greater than 1.5 cm, all Δ Dmean fell within ±2 Gy. For contours obtained using deep learning and atlas-based automatic delineation, the doses of 50.0%±17.3% and 52.6%±19.3% of patients fell within the dose ranges of clinical contours, respectively. The numbers of patients for whom the Dmax of the spinal cord, optic nerve, optic chiasm and the D1 cm 3 of the mandible in the two types of automatic contours fell within the dose ranges of clinical contours were statistically different ( t = -4.24, -3.99, -3.16, 3.51, P < 0.05). Conclusions:After expert correction, the automatic delineation results from different sources exhibited certain geometric differences. The expert correction reduced the impacts of automatic contours on plan optimization. The average distance of OVH is identified as an important feature used to determine dose differences. For small-volume serial organs close to the target volumes, meticulous corrections are required before applying auto-segmentation to clinical practice.

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