Dosimetric effect of respiration-gated beam on IMRT delivery

Intensity modulated radiation therapy (IMRT) with a dynamic multileaf collimator (DMLC) requires synchronization of DMLC leaf motion with dose delivery. A delay in DMLC communication is known to cause leaf lag and lead to dosimetric errors. The errors may be exacerbated by gated operation. The purpose of this study was to investigate the effect of leaf lag on the accuracy of doses delivered in gated IMRT. We first determined the effective leaf delay time by measuring the dose in a stationary phantom delivered by wedge-shaped fields. The wedge fields were generated by a DMLC at various dose rates. The so determined delay varied from 88.3 to 90.5 ms. The dosimetric effect of this delay on gated IMRT was studied by delivering wedge-shaped and clinical IMRT fields to moving and stationary phantoms at dose rates ranging from 100 to 600 MU/min, with and without gating. Respiratory motion was simulated by a linear sinusoidal motion of the phantom. An ionization chamber and films were employed for absolute dose and 2-D dose distribution measurements. Discrepancies between gated and nongated delivery to the stationary phantom were observed in both absolute dose and 2-D dose distribution measurements. These discrepancies increased monotonically with dose rate and frequency of beam interruptions, and could reach 3.7% of the total dose delivered to a 0.6 cm3 ion chamber. Isodose lines could be shifted by as much as 3 mm. The results are consistent with the explanation that beam hold-offs in gated delivery allowed the lagging leaves to catch up with the delivered monitor units each time that the beam was interrupted. Low dose rates, slow leaf speeds and low frequencies of beam interruptions reduce the effect of this delay-and-catch-up cycle. For gated IMRT it is therefore important to find a good balance between the conflicting requirements of rapid dose delivery and delivery accuracy.     

Attenuation of intracavitary applicators in 192Ir-HDR brachytherapy

Unlike the penetrating monoenergetic 662 keV gamma rays emitted by 137Cs LDR sources, the spectrum of 192Ir used in HDR brachytherapy contains low-energy components. Since these are selectively absorbed by the high-atomic number materials of which intracavitary applicators are made, the traditional neglect of applicator attenuation can lead to appreciable dose errors. We investigated the attenuation effects of a uterine applicator, and of a set of commonly used vaginal cylinders. The uterine applicator consists of a stainless steel source guide tube with a wall thickness of 0.5 mm and a density of 8.02 g/cm3, whereas the vaginal cylinders consist of the same stainless steel tube plus concentric polysulfone cylinders with a radius of 1 or 2 cm and a density of 1.40 g/cm3. Monte Carlo simulations were performed to compute dose distributions for a bare 192Ir-HDR source, and for the same source located within the applicators. Relative measurements of applicator attenuation using ion-chambers (0.125 cm3) confirmed the Monte Carlo results within 0.5%. We found that the neglect of the applicator attenuation overestimates the dose along the transverse plane by up to 3.5%. At oblique angles, the longer photon path within applicators worsens the error. We defined attenuation-corrected radial dose and anisotropy functions, and applied them to a treatment having multiple dwell positions inside a vaginal cylinder.     

北京市东城区公共场所冷却塔使用状况及健康风险评估

目的了解北京市东城区公共场所冷却塔使用及卫生状况,评估各场所冷却塔军团菌病健康风险。方法2018年5—9月,采集东城区内三类共26家公共场所冷却塔冷却水,填写相关调查问卷,通过冷却塔军团菌病健康风险指数模型计算各场所健康风险。结果本次研究中各场所冷却水样本嗜肺军团菌检测均为阴性,合格率为100%。游离性余氯平均为0.15 mg/L。酒店类场所冷却塔规模、加药方式和频率与其他场所有明显差别。26家公共场所健康综合风险平均为61.49,其中军团菌增殖风险、含菌气溶胶传播风险、暴露人群易感风险分别为16.13、22.66和22.70。不同场所冷却塔军团菌病健康风险评估结果存在一定差异,医院类场所健康风险指数高于酒店和商场(F=3.78,P<0.05)。结论冷却塔军团菌病健康风险高低主要受公共场所周围易感人群影响,该地区相关卫生部门应加强对相关易感人群的保护,对各类场所相关政策法规进行制定、完善和实施。     

A head-to-head comparison of measurement properties of the EQ-5D-3L and EQ-5D-5L in acute myeloid leukemia patients

Quality of Life Research - This study aimed to compare the measurement properties of EQ-5D-3L(3L) and EQ-5D-5L(5L) in patients with acute myeloid leukemia (AML) in China. We consecutively recruited...     

乳腺癌波形蛋白表达的生物学意义

应用波形蛋白童克隆抗体（Ｖｉｍ）免疫组化ＡＢＣ法对７５例乳腺癌进行标记分析。结果显示，Ｖｉｍ阳性３４例，阳性率４５．３％。统计分析表明，Ｖｉｍ表达与肿瘤的组织学分级有关（Ｐ＜０．００５），Ｖｉｍ阳性肿瘤的ＡｇＮＯＲ均数大于阴性组）Ｐ＜０．０１），Ｖｉｍ阳性组病人的５年生存率低（Ｐ＜０．００５）。以上提示了乳腺癌Ｖｉｍ表达是肿瘤分化低、细胞增生活跃和病人预后不良的指征。     

应用AF系统治疗胸腰椎不稳定骨折17例临床分析

目的分析总结应用AF系统治疗胸腰椎不稳定骨折的效果与治疗时间选择的差异。方法对17例胸腰椎不稳定骨折采用AF治疗后进行回顾性总结性分析。结果17例胸腰椎不稳定骨折中爆裂型7例,屈曲压缩型9例,合并脱位1例,其中11例合并不同程度神经损伤,按Frankel分级,A级2例;B级2例;D级9级;E级4例。术后按Frankel分级神经功能恢复情况为:B级1例;C级2例;D级1例;E级13例。椎体高度及节段弧度恢复为:术前椎体前缘平均高度50%(25%~70%),术后平均高度为95%(75%~100%)。Cobb’s角,术前平均22°(12°~40°),术后平均2.4°(0°~10°)。结论胸腰椎不稳定骨折应用AF系统治疗效果满意,且手术疗效与时间成正比,越早手术则椎体高度的恢复及神经功能恢复越能接近正常。     

P_(16)蛋白在卵巢上皮性肿瘤的表达及临床意义

目的 :探讨P16蛋白在卵巢上皮性肿瘤中的表达及临床意义。方法 :采用SP免疫组化法检测P16蛋白在 82例卵巢上皮性肿瘤组织 (良性 2 0例 ,恶性癌 6 2例 )及 1 5例正常卵巢组织常规石蜡标本的表达。结果 :P16蛋白在卵巢上皮性癌中检出率为 5 3 2 % ,低于良性卵巢瘤 90 0 %及正常组织 93 3% (P <0 0 1 )。不同分化程度卵巢癌之间P16蛋白的阳性率无显著差别 (P >0 0 5 ) ,P16蛋白表达与临床分期及预后有关 (P <0 0 5 ,P <0 0 1 )。结论 :P16蛋白在卵巢上皮性恶性肿瘤的发生、发展中起作用 ,P16的缺失表达与卵巢癌的进展和预后不良有关。     

妊高征患者胎儿脐血流速度与围产儿预后的关系

目的：探讨妊高征患者胎儿脐动脉血流速度比值（Ｓ／Ｄ）与围产儿预后的关系,方法：应用彩色超声波对９８例妊高征患者胎儿脐动脉血流速度指数进行测量并与新生儿体重,新生儿Ａｐｇａｒ评分,羊水性质和围产期结局的关系进行分析,结果：９８例妊高征中有３４例围产儿预后良好,６４例围产儿预后不良,围产儿预后不良发生率,中,重度妊高征明显高于轻度妊高征（Ｐ〈０．０１）,Ｓ／Ｄ比值与围产儿预后的程度业的相关性,结论,产