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.

Objective To evaluate the clinical value and efficacy of transcatheter preoperative superselective arterial embolization in sacral or ilium tumors.Methods The procedures of superselective arterial embolization with gelfoam were performed in 15 cases. The lesions included giant cell tumor of bone (n = 5) , aneurysmal bone cyst (n = 2) ,chordoma (n = 2) , metastatic tumor (n = 4)and chondrosarcoma (n = 3) . The operations of resection were done 1 to 5 days after superselective arterial embolization.Results Angiograms showed marked reduction (80% or more) of the tumor's staining after embolization. In this series ,the average blood loss was 1100 ml ,during operations(aranged from 500 ml to 2600 ml),and all tumors were completely resected.Conclusion Preoperative transcatheter selective arterial embolization is an effective and safe method in reducing blood loss during operations and improving therapeutic effect for sacroiliac tumors.