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 efficacy and safety of oral magnesium sulfate solution in split doses as bowel preparation in elderly patients undergoing colonoscopy.Methods A total of 368 elderly patients undergoing colonoscopy were enrolled at PLA General Hospital.The patients were randomly divided into magnesium sulfate solution orally in split doses group (group A,n=178) and single dose group (group B,n=190).Parameters including general information,defecation frequency,Boston bowel preparation score (BBPS),detection rate of lesions and adverse reactions.Results The frequency of defecations in group A was (7.6± 1.4),more than that in group B (6.6± 1.5) with statistical significance (P＜0.05).The duration of bowel preparation in group A was (128.6±25.3) min,shorter than that of group B (165.4±29.7) min (P＜0.05).The BBPS in group A was (8.09±0.67),better than that of group B (7.34±0.58) (P＜0.05).The detection rates of intestinal polyps and micropolyps (diameter＜0.5 cm) in group A were 73/178 (41.0％) and 51/178 (28.7％) respectively,compared with 58/190 (30.5％) and 37/190 (19.5％) in group B (both P＜0.05).In group A,8 patients reported adverse reactions as abdominal distension and discomfort.One patient had ST-T abnormality of electrocardiogram (ECG).No nausea or vomiting occurred,yet 2 cases needed enema for inadequate bowel preparation.Twenty-one cases in group B reported adverse events including 7 with nausea and vomiting.There were 13 patients treated with enema.Abnormal ECG was found in 4 patients in group B.The satisfaction rate of group A was 97.8％,higher than that of group B (91.6％) (P＜0.05).Conclusions The effect of bowel preparation of elderly patients with magnesium sulfate solution in split dose has a better tolerance,good cleaning effect and low incidence of adverse reactions.It is an ideal choice for the elderly to prepare colonoscopy.