Objective To optimize the dose distribution of postoperative brachytherapy for linear keloids,and to investigate the effects of the number of radiation sources n,source-to-skin distance d,and source spacing a on dose distribution,thereby providing a reasonable radiation source arrangement scheme for radiotherapy in narrow and elongated wound areas.Methods A one-dimensional idealized model was established.Based on the inverse-square law,dose distributions were calculated under combinations of differentn(4,6,8,10)and d(from 0.3 to 2.0 cm).The proportions of dose-effective areas(90%-110%of the prescribed dose)and penumbra areas(20%-80%of the prescribed dose)were analyzed to evaluate the rationality of dose distribution.Results When d/a slightly exceeded 0.5,the proportion of the effective area reached its peak,and the proportion of the penumbra area was relatively low.An excessively small d/a led to cold spots in the irradiated area,while an excessively large d/a expanded the penumbra area.Increasing n significantly reduced the penumbra range and improved dose homogeneity.Conclusion The dose distribution is most reasonable when d/a is slightly greater than 0.5,and a multi-source arrangement(n≥6)is preferred to enhance dose homogeneity.This study provides guidance for parameter optimization in brachytherapy for keloids.

Objective To optimize the dose distribution of postoperative brachytherapy for linear keloids,and to investigate the effects of the number of radiation sources n,source-to-skin distance d,and source spacing a on dose distribution,thereby providing a reasonable radiation source arrangement scheme for radiotherapy in narrow and elongated wound areas.Methods A one-dimensional idealized model was established.Based on the inverse-square law,dose distributions were calculated under combinations of differentn(4,6,8,10)and d(from 0.3 to 2.0 cm).The proportions of dose-effective areas(90%-110%of the prescribed dose)and penumbra areas(20%-80%of the prescribed dose)were analyzed to evaluate the rationality of dose distribution.Results When d/a slightly exceeded 0.5,the proportion of the effective area reached its peak,and the proportion of the penumbra area was relatively low.An excessively small d/a led to cold spots in the irradiated area,while an excessively large d/a expanded the penumbra area.Increasing n significantly reduced the penumbra range and improved dose homogeneity.Conclusion The dose distribution is most reasonable when d/a is slightly greater than 0.5,and a multi-source arrangement(n≥6)is preferred to enhance dose homogeneity.This study provides guidance for parameter optimization in brachytherapy for keloids.

A group of compounds structurally related to tetrahydrocannabinol or capable of binding to cannabinoid receptors are collectively referred to as cannabinoids. Cannabinoids can be divided into plant derived cannabinoids， synthetic cannabinoids， and endogenous cannabinoids. Δ-9-THC is the only psychoactive compound in plant cannabinoids. Cannabis with Δ-9-THC>0.3% is internationally listed as a prohibited drug， while cannabis with Δ-9-THC<0.3% is industrial cannabis. Due to its low addiction and high commercial value， it is allowed to be added to food in many countries. More and more industrial cannabis foods become popular， and the detection/analysis of cannabinoid compounds in cannabis foods is particularly important； In addition to industrial cannabis， which is widely used in food， there are also various new drugs， synthetic cannabinoids， disguised as conventional food， which can cause the social problems and increase the food safety risks. This article will elaborate on the regulatory status of cannabinoid compounds in food， In order to promote the safety supervision of the domestic cannabis food.

ObjectiveIn order to ensure the food safety of cultured aquatic products in China， strengthen the supervision and improve detection efficiency， a high-throughput screening method for drug residues in aquatic products by mass spectrometry is to be developed. MethodsLiquid chromatography-electrostatic field track well high resolution mass spectrometry and C₁₈ column were used to separate and collect the information of ion fragments and retention time of 195 veterinary drug standards in positive ion mode， and drug residues in aquatic products were extracted by organic solvents. ResultsThe mass spectrum database and detection methods of 195 veterinary drug standards were established， and a pre-treatment method was developed for extracting veterinary drug residues from aquatic products by acetonitrile and ethyl acetate. The detection method was sensitive， accurate， simple and rapid， and the adding standard recovery of more than 80% compounds reached 70%‒110%. ConclusionThe establishment of this method can quickly and massively screen drug residues in aquatic products， provide technical support for food safety risk monitoring and supervision， cope with the increasing demand for aquatic products and aquaculture volume year by year， and provide a theoretical basis for the subsequent development of mass spectrometry high-throughput detection methods.