分化型甲状腺癌患者131I治疗后体内残留放射性活度的评估

目的 评估分化型甲状腺癌(DTC)患者¹³¹I治疗后体内残留放射性活度.方法 本次前瞻性研究包括49例DTC患者,分为“清甲”(¹³¹I摧毁术后残留的甲状腺组织)与“清灶”(¹³¹I治疗甲状腺床残留甲状腺癌、甲状腺床复发灶和转移灶)组,于服¹³¹I后收集患者每次排泄尿液,测定患者每天每次通过尿液排泄的放射性活度及排泄的总放射性活度,进而估算患者体内残留的放射性活度.分别于服¹³¹I后2、6、24、48、72 h进行1 m处剂量当量率的测定,估算患者体内残留放射性活度达到400 MBq时1 m处剂量当量率.结果 服¹³¹I后2、6、24、48、72 h体内残留¹³¹I活度占服¹³¹I初始活度的百分比,“清甲”组分别为99%、72%、25%、15%、7%,1 m处剂量当量率分别为157、120、35、11、9 μSv/h;"清灶"组对应百分比分别为99%、71%、18%、7%、3%,1 m处剂量当量率分别为232、182、48、11、2 μSv/h.体内残留的放射性活度与1 m处剂量当量率呈正相关(r=0.94,P<0.001).“清甲”与“清灶”组服¹³¹I后48~72 h体内残留放射性活度分别为548~259及451~248 MBq,对应的1 m处剂量当量率为8~10 μSv/h.结论 DTC患者于服¹³¹I后48~72 h体内残留放射性活度达到国家标准规定的400 MBq,即DTC患者1 m处剂量当量率达到8~10 μSv/h方可出院.     

分化型甲状腺癌患者131I治疗后体内放射性总活度的变化及影响因素

目的 探讨¹³¹I治疗分化型甲状腺癌(differentiated thyroid carcinoma,DTC)术后患者体内放射性总活度的变化及其代谢的影响因素。方法 回顾性分析2021年9月至2022年4月于空军军医大学第二附属医院核医学科接受¹³¹I治疗的218例DTC术后患者的临床资料,根据服用¹³¹I的剂量分为低剂量组(≤3.7 GBq)171例和高剂量组(＞3.7 GBq)47例,使用全身动态辐射监测系统在服用¹³¹I后24、48及72 h测定体内¹³¹I残留活度并探讨其变化的影响因素。结果 服用¹³¹I后低剂量组24、48及72 h的体内¹³¹I残留活度均明显低于高剂量组(t=-7.46、-3.31、-2.01,P<0.05);低剂量组24、48 h出院达标率明显高于高剂量组(21.0%vs. 4.3%、98.2%vs. 89.4%,χ²=7.23、5.91,P<0.05),且所有患者在72 h均可达出院标准。单因素分析显示患者24及48 h体内¹³¹I残留活度与年龄、体质量指数(body mass index,BMI)、基础代谢率(basal metabolism rate,BMR)及促甲状腺激素(thyroid stimulating hormone,TSH)有关。多元线性回归分析显示低剂量组24 h时年龄越大、BMR越高、TSH水平越高,体内¹³¹I残留活度越大,48 h时BMI越大、TSH越高,体内¹³¹I残留活度越大;高剂量组24 h时年龄越大、BMR越高,体内¹³¹I残留活度越大。患者体内¹³¹I残留活度达到400 MBq的时间以24、36 h来分析其影响因素,结果显示以24 h为分界时,TSH水平越低,体内¹³¹I残留活度越低;以36 h为分界时,年龄越小、TSH水平越低、¹³¹I治疗剂量越小,体内¹³¹I残留活度越低。结论 年龄、BMI、BMR及TSH水平是¹³¹I治疗DTC术后患者体内放射性总活度的影响因素,联合上述指标进行辐射剂量评估可为调整患者住院时长提供参考。     

131I标记抗表皮生长因子受体抗体靶向性纳米载体治疗胶质母细胞瘤的可行性实验研究

目的 构建¹³¹I标记抗表皮生长因子受体抗体(antiEGFR)靶向性的纳米载体,探讨其在细胞水平和动物体内用于胶质瘤治疗的可行性。方法 制备放射性碘(¹³¹I)标记的antiEGFR靶向性的纳米载体牛血清白蛋白聚己内酯复合物¹³¹I-antiEGFR-BSA-PCL。用共聚焦显微镜观察纳米载体能够与肿瘤细胞结合情况,用MTT法检测纳米载体的细胞毒性作用,摄碘率实验检测肿瘤细胞对放射性纳米载体的摄取。制备裸鼠种植瘤模型,通过瘤体内注射给药,观察裸鼠种植瘤的体积变化,通过SPECT显像观察药物在裸鼠体内的停留情况,并分析纳米载体在裸鼠体内的分布情况。结果 成功地制备了BSA-PCL及antiEGFR-BSA-PCL纳米载体。与BSA-PCL相比,antiEGFR-BSA-PCL更容易与肿瘤细胞结合。当放射性纳米载体的放射性活度达到0.925 MBq时,U251和U87细胞的生长抑制率¹³¹I-antiEGFR-BSA-PCL组均高于¹³¹I-BSA-PCL组(t=2.517、2.821,P<0.05),且均高于同组其他剂量(U251:t=2.148、2.693,P<0.05;U87:t=2.436、2.615,P<0.05)。裸鼠体内实验发现两种纳米载体瘤体内注射后均经过肝脏代谢。¹³¹I-antiEGFR-BSA-PCL组荷瘤裸鼠的种植瘤体积较¹³¹I-BSA-PCL组缩小更多(t=4.115,P<0.05)。结论 ¹³¹I-antiEGFR-BSA-PCL在体内外实验中均能够抑制胶质瘤生长,为胶质瘤的治疗和预后评估提供了一种新方法。     

甲状腺癌患者131I治疗过程中的外照射剂量水平分析

目的 通过测量甲状腺癌患者¹³¹I治疗过程中患者周围剂量当量率及住院期间胸前体表的累积剂量,探讨加强¹³¹I治疗过程中辐射防护问题。方法 在某开展甲状腺癌患者¹³¹I治疗的医院,选取接受¹³¹I治疗的患者78名,用γ辐射巡测仪测量患者服用¹³¹I药物后10 min、1、2、5 d共5个时间点的周围剂量当量率;测量距离分别为体表5、0.5和1 m处;测量方向为患者前后左右4个方向。用光激发光剂量计测量患者胸前位置住院期间（6 d）接受的累积吸收剂量。结果 服药后10 min患者胸前体表5 cm处周围剂量当量率最高可达4.81 mSv/h,患者出院前胸前体表5 cm处周围剂量当量率范围在2.6~64.1 μSv/h,住院期间患者胸前体表的累积剂量在15.9~58.8 mGy之间。服药10 min后3.7 GBq药剂量组与5.55 GBq药剂量组患者体表5 cm处剂量率差异有统计学意义（t=-6.11,P<0.05）,服药10 min后男性与女性患者体表5 cm处剂量率差异有统计学意义（t=4.52,P<0.05）,其他组别差异无统计学意义（P>0.05）。结论 在甲状腺癌患者¹³¹I治疗过程中,患者周围具有较高的辐射水平,应加强对患者的防护及管理,减少周围公众不必要的照射。     

核医学场所空气中131I浓度监测及工作人员内照射剂量评价探讨

目的 了解医疗机构¹³¹I治疗工作场所空气中¹³¹I核素的活度浓度水平，探讨通过空气采样方法估算工作人员内照射剂量的方法并分析其影响因素。方法 选取郑州市10家开展¹³¹I核素治疗的工作场所，采用空气采样方法采集¹³¹I治疗工作场所中放射性气溶胶，用高纯锗γ能谱仪进行γ放射性核素测定并推算工作场所空气中¹³¹I核素的活度浓度水平，根据测量结果和现场调查结果估算放射工作人员因¹³¹I核素吸入导致的内照射剂量。结果 19个分装间空气样品的¹³¹I活度浓度为0.087~570 Bq/m³，平均为（51.04±128.58）Bq/m³；11个病房空气样品的¹³¹I活度浓度为0.162~54.6 Bq/m³，平均为（7.97±15.89）Bq/m³。根据GBZ 129-2016《职业性内照射个人监测规范》推荐的典型工作时间估算，放射工作人员由于吸入¹³¹I核素导致的年待积有效剂量范围为2 μSv~10 mSv，平均为（0.61±1.80）mSv，年有效剂量均未超过国家标准所规定的剂量限值。结论 郑州市10家医疗机构核医学工作场所中¹³¹I核素活度浓度较高的样品多分布在甲状腺癌住院患者较多、核素操作量较大的三甲医院，由此导致的工作人员内照射剂量不容忽视。根据空气样品的测量结果估算内照射剂量带有很大不确定度，但空气采样方法可及时发现异常或事故情况下的放射性污染，为工作人员开展体外直接测量和内照射评价提供预警。     

131I标记纳米脂质体靶向治疗结肠癌的实验研究

目的 研究¹³¹I-antiEGFR-BSA-PCL对LS180细胞结肠癌裸鼠移植瘤内照射的治疗效果。方法 构建抗表皮生长因子受体(EGFR)标记的纳米脂质体及EGFR靶向性。通过荧光共聚焦显微镜、细胞摄碘实验观察纳米载体的靶向性及LS180细胞对其摄取情况。将裸鼠40只按随机数字表法分为4组,通过瘤体内注射的方式向移植瘤内分别注射74 MBq (740 MBq/ml) ¹³¹I-antiEGFR-BSA-PCL、¹³¹I-BSA-PCL、¹³¹I及相同体积的生理盐水。通过研究裸鼠体重、肿瘤体积、SPECT显像及组织病理学方法,观察纳米脂质体的抑瘤效果。结果 共聚焦实验显示,与BSA-PCL组相比,antiEGFR-BSA-PCL组细胞内绿色荧光较明显,其介导的胞吞效应显著。摄碘率实验中,LS180细胞对¹³¹I-antiEGFR-BSA-PCL的摄取率明显高于¹³¹I-BSA-PCL(t=2.77~5.40,P<0.01)。¹³¹I-antiEGFR-BSA-PCL组与¹³¹I-BSA-PCL组裸鼠肿瘤增殖均较慢,二者差异无统计学意义(P>0.05)。给药后72 h,¹³¹I-antiEGFR-BSA-PCL与¹³¹I-BSA-PCL的肿瘤摄取率分别为(21.61±1.01)和(20.58±0.65)% ID/g,均明显高于¹³¹I组(t=9.36、8.69,P<0.01)。SPECT显像显示纳米脂质体主要特异性积聚在肿瘤区。结论 ¹³¹I-antiEGFR-BSA-PCL对LS180结肠癌裸鼠移植瘤有明显的抑制作用。     

腹盆腔肿瘤125I粒子植入术后个体化防护临床研究

目的 研究腹盆腔肿瘤患者¹²⁵I粒子植入术后周围环境的受照剂量率及有效剂量,为不同人群的安全防护提供参考。方法 采用袖珍辐射仪,监测42例腹盆腔肿瘤患者¹²⁵I粒子植入术后24 h内,距离植入部位各方向不同距离的受照剂量率,比较不同方向不同距离的剂量率差异。对植入粒子的总活度与测量的剂量率及植入深度与标准活度下剂量率进行曲线拟合并得出关系方程。根据公式计算不同人群、不同距离受照射的剂量率与警戒时间的关系。结果 距垂直粒子植入部位30、50、100 cm的受照剂量率分别为（6.92±2.87）、（4.10±1.62）和（1.30±0.48）μSv/h,差异有统计学意义（χ²=73.71,P<0.05）。患者左、右侧面30、50、100 cm受照剂量率分别为（0.378±0.156）和（0.384±0.153）μSv/h、（0.170±0.089）和（0.176±0.086）μSv/h、（0.039±0.014）和（0.043±0.017）μSv/h,差异均有统计学意义（χ²=76.19、76.33,P<0.05）。垂直粒子植入部位的受照剂量率与植入粒子总活度及标准活度下剂量率与植入深度呈线性关系。患者对同住成年人无警戒时间,同床成年人、接触同事、同住未成年人及孕妇的警戒时间与剂量率的关系公式分别为：t（d）=-106.616+83.779lnD（t）、t（d）=26.556+85.933lnD（t）、t（d）=3.088+85.017lnD（t）。结论 ¹²⁵I粒子植入术后患者,监测其周边环境的辐射剂量在辐射安全范围内;且随着植入粒子总活度的减小及植入深度的增大剂量率减小;同时根据术后测得的剂量率或植入粒子的总活度、植入粒子的深度计算不同人群的警戒时间,进行个体化防护。     

放射性125I粒子植入对人肺腺癌裸鼠移植瘤微血管生成的影响

目的 探讨放射性¹²⁵I粒子植入对人肺腺癌裸鼠移植瘤微血管生成的影响及其作用机制。方法 制备人肺腺癌细胞A549裸鼠皮下移植瘤模型24只,采用随机数字表法分为4组,每组6只,0、22.2、29.6 MBq组和对照组。用18 G植入针在各组裸鼠瘤体内分别植入放射活度为0、22.2和29.6 MBq ¹²⁵I粒子,每个移植瘤内植入一枚,对照组不予处理。观察肿瘤生长情况,每4天测量肿瘤大小。30 d后处死裸鼠,绘制肿瘤生长曲线。瘤组织免疫组织化学S-P法检测微血管密度（microvascular density,MVD）,并分别用RT-PCR、Western blot法检测血管内皮生长因子（vascular endothelial growth factor,VEGF）和缺氧诱导因子-1α（hypoxia inducible factor-1α,HIF-1α）的mRNA及蛋白的表达。结果 粒子植入治疗后54 d,22.2、29.6 MBq组移植瘤体积明显小于对照组（q=14.117、17.075,P<0.05）,但0 MBq组与对照组、22.2与29.6 MBq组瘤体积差异均无统计学意义（P>0.05）。CD34阳性染色结果显示,22.2 MBq组的MVD为522±119,29.6 MBq组为491±121,明显低于对照组的922±260（q=4.826、5.197,P<0.05）,但0 MBq组与对照组、22.2 MBq组与29.6 MBq组差异均无统计学意义（P>0.05）。RT-PCR检测表明,22.2 MBq组的VEGF和HIF-1α mRNA相对表达量分别为0.279±0.0659和0.370±0.0857,29.6 MBq组为0.215±0.0620、0.278±0.0651,均低于对照组（q=18.881、17.211和15.376、14.733,P<0.05）,但0 MBq组与对照组、22.2 MBq组与29.6 MBq组之间差异均无统计学意义（P>0.05）。Western blot结果显示,22.2 MBq组与29.6 MBq组瘤组织VEGF和HIF-1α蛋白表达均明显减少,与对照组相比,差异有统计学意义（q=5.848、6.263和6.560、7.576,P<0.05）,但0 MBq组与对照组以及22.2 MBq组与29.6 MBq组差异均无统计学意义（P>0.05）。结论 放射性¹²⁵I粒子植入能有效抑制人肺腺癌裸鼠移植瘤微血管生成。     

呋塞米介入对18 F-脱氧葡萄糖正电子发射计算机断层显像的放射防护作用

目的 探讨呋塞米介入¹⁸F-脱氧葡萄糖(¹⁸F-FDG)正电子发射计算机断层显像(PET/CT)的放射防护作用。方法 146例患者按随机数表法随机分为两组,实验组74例,对照组72例。试验组注射前口服呋塞米40 mg,正常对照组未行特殊处理,¹⁸F-FDG注射60、120 min后,分别在其正面前胸、腹水平测量0.5 m处周围剂量当量率。结果 试验组注射¹⁸F-FDG后60 min胸部及腹部、120 min胸部及腹部的周围剂量当量率分别为(30.80±8.61)、(41.38±11.06)、(18.26±4.85)和(24.66±6.50)μSv/h,均低于对照组,差异有统计学意义(t=15.36、13.13、18.73、17.29,P＜0.05)。试验组和对照组的纵隔SUV_max、肝脏SUV_max差异无统计学意义(P＞0.05)。多因素分析显示,是否服用速尿、体表面积是影响周围剂量当量率的主要影响因素(t=-13.52、2.96,P＜0.05),年龄、性别对周围剂量当量率的影响不明显(P＞0.05)。结论 呋塞米介入可促进排尿,在不影响影像质量的前提下有效降低了受检者的体内辐射,有较好的放射防护作用。     

碘治疗工作场所空气中131I的监测结果与分析

目的 了解碘治疗工作场所空气中¹³¹I气溶胶的活度浓度,估算核医学科医务人员吸入¹³¹I所致内照射剂量。方法 使用CF-1001BRL型便携式大容量空气采样器,采用碘盒收集山东省6家医院核医学科碘治疗工作场所空气中的¹³¹I气溶胶,利用HPGe-γ能谱仪对样品进行测量,得到6家医院碘治疗工作场所中¹³¹I的活度浓度值,并估算医务人员的内照射剂量。结果 6家医院碘治疗工作场所空气中¹³¹I的活度浓度范围为3.64~2.94×10³Bq/m³,控制区（病房、患者通道、分装间、远程操作给药室）¹³¹I的浓度水平明显高于监督区,监督区¹³¹I的浓度最高的是医护通道,为2.62×10²Bq/m³。核医学科医务人员两种职业待积有效剂量估算值为0.07~5.68 mSv,均未超过国家规定限值。结论 医院核医学科碘治疗工作场所仍存在不可忽视的¹³¹I气溶胶污染现象,应面向全国各地区核医学科开展内照射监测,探索更加合理的防护标准和方法。     

人体中的镭-226、镭-228、钋-210、铅-210

本文报道了广东阳江高本底地区6名、对照地区8名人尸体的骨²²⁶Ra、²²⁶Ra的浓度以及部分居民内脏器官中。²¹⁰Po、²¹⁰Pb的浓度。结果轰明阳江高本底地区和对照地区居民骨镭-226、镭-228的浓度分别为29.9pCi/kg, 26.9pCi/kgl 8.7pCi/kg, 8.2pCi/kg.由此估算出阳江高本底地区屠民骨中²²⁶Ra、²²⁸Ra的负薄璧及对骨衬、骨髓所产生的剂量当量分别为对照地区民民的3.4倍, 3.3倍。两地区居民内脏器官中^{210Po、210Pb的测定分析铡数较少但仍看出, 高本底地区均明显高于对照地区.}     

226Ra 228Ra 210Pb和210Po在水生生物及食物链中转移规律的探讨

目的 为了解天然放射性核素²²⁶Ra、²²⁸Ra、²¹⁰Pb与²¹⁰Po在水生物及食物链中转移和蓄积情况。方法 定点采集养殖水产品及栖息环境中水与底质沉积物, 按不同的实验需要, 每个鲜样分别剥取肉, 骨(壳),鳞片和胃肠。烹饪样品, 洗净、称重、清炖, 熟后分离出骨(壳),余为食物。样品分别测定²²⁶Ra、²²⁸Ra、²¹⁰Pb和²¹⁰Po含量。数据按统计学要求处理, 配对数据, 作了配对显着性检验。结果 ²²⁶Ra、²²⁸Ra和²¹⁰Pb主要沉积于骨(壳)中, 浓集系数为10²～10³,肉中为10⁰～10².²¹⁰Po主要蓄积在水生物胃肠中, 浓集系数在10²～10⁴,鱼类胃肠与贝类肉中可达10⁴.水产食品烹饪加工过程²²⁶Ra、²²⁸Ra和²¹⁰Pb在食物链中转移不明显, 经配对显着性检验, 差异无显着性(P0.05);然而210Po在淡水鱼类和虾类中转移是明显的, 肉配对检验有非常显着性差别(P<0.01).结论水生物对²²⁶Ra、²²⁸Ra、²¹⁰Pb和²¹⁰Po有很强浓集能力。     

Production of large quantities of 90Y by ion-exchange chromatography using an organic resin and a chelating agent

The performance of a system composed of an organic cation exchanger (Dowex 50Wx8) and a chelating agent (EDTA) previously described for the successful production of (90)Y via a (90)Sr/(90)Y generator is assessed under dynamic conditions. In an attempt to overcome the established limitation of ion-exchange resins for the separation of subcurie quantities of activity, (90)Y is repeatedly isolated from an 11.8-GBq (320 mCi) (90)Sr cow using a three-column tandem arrangement. The high recovery and radionuclidic purity obtained for (90)Y and the parameters of the separation (time, eluant concentration, pH and flow rate range) strongly suggest that Ci quantities of (90)Y can be handled satisfactorily by the ion-exchange method. No replacement or treatment of the cow, low waste generation and (90)Sr losses less than 0.1% after each run were observed during the present study which, in combination with the low cost of this resin, may result in an attractive alternate method for the production of large quantities of (90)Y.     

Rapid determination of Sr impurities in freshly “generator eluted” Y for radiopharmaceutical preparation

⁹⁰Y is one of the most useful radionuclides for radioimmunotherapeutic applications and has a half-life (t_1/2=64.14 h) suitable for most therapeutic applications, beta particles of high energy and decays to a stable daughter. It is significant that ⁹⁰Y is available conveniently and inexpensively from a radionuclide “generator” by decay of its parent, ⁹⁰Sr. Nevertheless, current and planned clinical applications with [⁹⁰Y] labelled compounds employ activity levels that cannot be readily obtained from an in-house generator, but from commercial sources. We have evaluated Eichrom's Sr-resin, either as an “in-house” generator or as a fast QC method for analysis of ⁹⁰Y solutions.In particular, for the development as a generator, we investigated the percentage of the radio-Sr in the first 8 M HNO₃ eluate: in this fraction the concentration of ⁹⁰Sr must be smaller than 10⁻⁵% (recommendations of the International Commission on Radiological Protection). For evaluation as a rapid QC method, we analyzed the concentration of ⁹⁰Y in all the fractions containing “only” radio-Sr: ⁹⁰Y should not be present in these eluates. After the collection of β⁻ and γ spectra and analysis of them, we concluded that commercial Sr-resin minicolumn cannot give us the results expected; we developed an in-house system loaded with 4 mL of Sr-resin which gave better results as a generator and a rapid QC method.     

Radiobiological Issues in the Anomalous Enhanced Effect of Low-dose-rate Fission-spectrum Neutrons: Reply to Letter to the Editor by G. W. Barendsen

Summary

The influence of diet or its ingredients on ¹⁴¹Ce absorption and retention was investigated in six-day-old rats. Animals were fed over 8 h with cow's milk, rat diet or a mixture of rat diet ingredients (fish meal, sunfiower meal, alfalfa, cane molasses and premix) labelled with ¹⁴¹Ce. Whole-body radioactivity was determined in a double crystal scintillation counter every 24 h over a six-day period. Gut, liver, kidney and femur retention and cerium distribution in the gut was determined at the end of the experiment. Compared to milk diet, administration of rat diet or ingredients caused respectively 3 and 7·5 times lower whole body retention. Carcass retention was reduced by rat diet or ingredients 2–3 times and intestinal retention 3 and 8 times respectively. Irrespective of the dietary treatment the main site of cerium intestinal retention was the ileum. Our present results indicate that some compounds of rat diet might be considered as a means of reducing cerium absorption and intestinal retention in the very young.     

Pre-therapeutic dosimetry and biodistribution of 86Y-DOTA-Phe1-Tyr3-octreotide versus 111In-pentetreotide in patients with advanced neuroendocrine tumours

Purpose For the internal radiotherapy of neuroendocrine tumours, the somatostatin analogue DOTATOC labelled with ⁹⁰Y is frequently used [⁹⁰Y-DOTA-Phe¹-Tyr³-octreotide (SMT487-OctreoTher)]. Radiation exposure to the kidneys is critical in this therapy as it may result in renal failure. The aim of this study was to compare cumulative organ and tumour doses based upon dosimetric data acquired with the chemically identical ⁸⁶Y-DOTA-Phe¹-Tyr³-octreotide (considered as the gold standard) and the commercially available ¹¹¹In-pentetreotide.Methods The cumulative organ and tumour doses for the therapeutic administration of 13.32 GBq ⁹⁰Y-DOTA-Phe¹-Tyr³-octreotide (three cycles, each of 4.44 GBq) were estimated based on the MIRD concept (MIRDOSE 3.1 and IMEDOSE). Patients with a cumulative kidney dose exceeding 27 Gy had to be excluded from subsequent therapy with ⁹⁰Y-DOTA-Phe¹-Tyr³-octreotide, in accordance with the directives of the German radiation protection authorities.Results The range of doses (mGy/MBq ⁹⁰Y-DOTA-Phe¹-Tyr³-octreotide) for kidneys, spleen, liver and tumour masses was 0.6–2.8, 1.5–4.2, 0.3–1.3 and 2.1–29.5 (⁸⁶Y-DOTA-Phe¹-Tyr³-octreotide), respectively, versus 1.3–3.0, 1.8–4.4, 0.2–0.8 and 1.4–19.7 (¹¹¹In-pentetreotide), with wide inter-subject variability. Despite renal protection with amino acid infusions, estimated cumulative kidney doses in two patients exceeded 27 Gy.Conclusion Compared with ⁸⁶Y-DOTA-Phe¹-Tyr³-octreotide, dosimetry with ¹¹¹In-pentetreotide overestimated doses to kidneys and spleen, whereas the radiation dose to the tumour-free liver was underestimated. However, both dosimetric approaches detected the two patients with an exceptionally high radiation burden to the kidneys that carried a potential risk of renal failure following radionuclide therapy.     

Comparison of extraarticular leakage values of radiopharmaceuticals used for radionuclide synovectomy

OBJECTIVES: Radionuclide synovectomy is a reliable therapy in patients with chronic synovitis. However, radiation doses delivered to non-target organ systems due to leakage of radioactive material from the articular cavity are an important disadvantage of this procedure. In this study we compared extraarticular leakage values of the 3 commonly used radiopharmaceuticals; 90Y-citrate, 90Y-silicate and 186Re-sulfide colloid. MATERIALS AND METHODS: Thirty-five patients with persistent synovitis were enrolled in the study. Twenty-two hemophilic, 8 rheumatoid arthritis and 5 patients with pigmented villonodular synovitis were studied. 90Y labeled silicate and citrate were used for knee joints and 186Re-sulfide for intermediate sized joints. Radiocolloid leakage values were evaluated using a gamma camera with 20% window centered over the bremsstrahlung photopeak of 90Y and a respective window over the 137 keV photopeak of 186Re. Regions of interest were drawn over the injection site, the regional lymph nodes and the background areas. Leakage of radiocolloid was calculated by dividing the counts/pixel in the regional lymph node area to the counts/pixel in the injection site. RESULTS: No visible leakage was observed. The median leakage values calculated for 90Y-citrate, 90Y-silicate and 186Re-sulfide were found as 1.9%, 2.4% and 2.7%, respectively. The difference between the variability of leakage values was not statistically significant (p > 0.05). CONCLUSION: There was no significant difference in terms of extraarticular leakage between 9Y-citrate, 9Y-silicate and 186Re-sulfide radiocolloids.     

Comparison of [18F]FDG-PET and L-3[123I]-iodo-alpha-methyl tyrosine (I-123 IMT)-SPECT in primary lung cancer

OBJECTIVE: The aim of this study was to evaluate L-3[123I]-iodo-alpha-methyl tyrosine (IMT)-SPECT and FDG-PET in pulmonary lesions suspected to be lung cancer. METHODS: Whole body PET (measured transmission corrected emission scans) was performed 45 minutes after i.v. injection of 222-370 MBq (6-10 mCi) 18F-FDG on a Siemens PET scanner (ECAT EXACT 47) including 5-6 bed positions. 123I-IMT-SPECT (chest) was performed after injection of 370 MBq (10 mCi) with a dual head camera (Picker Prism 2000) and commercially available reconstruction algorithms. Ten patients (6 male and 4 female) with suspected lung cancer were investigated. The results were compared to histological findings after surgery or bronchoscopic biopsies and CT. RESULTS: 123I-IMT-SPECT and FDG-PET were able to detect all 9 cases of lung cancer (1-8 cm in diameter). One case was true negative. Both imaging methods were true positive with respect to mediastinal lymph node metastases in one patient. The tumor/background ratio was higher with PET (8.20 vs. 2.84). CONCLUSION: Despite the limited number of patients it may be concluded that IMT-SPECT as well as FDG-PET are suited to correctly diagnose lung cancer. Nevertheless, FDG-PET, if available, seems to be better suited because of the higher tumor/background ratio and better resolution.     

Rapid synthesis and in vitro and in vivo evaluation of folic acid derivatives labeled with fluorine-18 for PET imaging of folate receptor-positive tumors

In an attempt to visualize folate receptors that overexpress on many cancers, [¹⁸F]-fluorobenzene and pyridinecarbohydrazide-folate/methotrexate conjugates ([¹⁸F]-1, [¹⁸F]-2-folates and [¹⁸F]-8, [¹⁸F]-9-MTXs) were synthesized by the nucleophilic displacement reactions using ethyl-trimethylammonium-benzoate and pyridinecarboxylate precursors. The intermediates ethyl [¹⁸F]-fluorinated benzene and pyridine esters were reacted with hydrazine to produce the [¹⁸F]-fluorobenzene and pyridinecarbohydrazides, followed by coupling with N-hydroxysuccinimide-folate/MTX. Radiochemical yields were greater than 80% (decay corrected), with total synthesis time of less than 45 min. Radiochemical purities were always greater than 97% without high-performance liquid chromatography purification. These synthetic approaches hold considerable promise as rapid and simple method for the radiofluorination of folate derivatives with high radiochemical yield in short synthesis time. In vitro tests on KB cell line showed that significant amount of the radioconjugates were associated with cell fractions, and in vivo characterization in normal Balb/c mice revealed rapid blood clearance of these radioconjugates with excretion predominantly by the urinary and partially by the hepatobiliary systems. Biodistribution studies in nude mice bearing human KB cell line xenografts demonstrated significant tumor uptake and favorable biodistribution profile for [¹⁸F]-2-folate over the other conjugates. The uptake in the tumors was blocked by excess coinjection of folic acid, suggesting a receptor-mediated process. Micro-positron emission tomography images of nude mice bearing human KB cell line xenografts confirmed these observations. These results demonstrate that [¹⁸F]-2-folate may be useful as molecular probe for detecting and staging of folate receptor-positive cancers, such as ovarian cancer and their metastasis as well as monitoring tumor response to treatment.     

Repeated 0.5-Gy γ-ray irradiation attenuates autoimmune manifestations in MRL-lpr/lpr mice

Purpose: MRL-lpr/lpr mice, a model for various autoimmune diseases, were repeatedly irradiated with 0.5 Gy of γ-rays, and changes in their autoimmune manifestations were investigated.

Materials and methods: MRL-lpr/lpr mice at 13 weeks of age were maintained in plastic cages and exposed whole-body to 0.5 Gy γ-ray irradiation from a ¹³⁷Cs source 5 times per week for 4 weeks, from the time they were 13 weeks old until they reached 17 weeks old. Changes of autoimmune manifestations were examined 3 weeks later at the 20th week.

Results: Splenomegaly, lymphadenopathy, and proteinuria in MRL-lpr/lpr mice were clearly ameliorated by a total dose of 10 Gy (0.5 Gy/day×5 days/week for 4 weeks). Histologically severe disease-specific damage to the kidney and the salivary gland, i.e., glomerulonephritis and sialoadenitis, was also improved after irradiation. CD3⁺ CD4^? CD8^? CD45R/B220⁺ T cell numbers, which proliferate abnormally in MRL-lpr/lpr mice, were significantly decreased by the irradiation, possibly through induction of apoptosis. The elevated NO₂^? and NO₃^? (NO_x^?) production by macrophages of MRL-lpr/lpr mice was lowered by the irradiation. The irradiation also prolonged the life span of MRL-lpr/lpr mice. These phenomena may contribute to the amelioration of autoimmune manifestations in MRL-lpr/lpr mice exposed to repeated small-doses of γ-rays.

Conclusions: Repeated small-dose γ-ray exposure ameliorates the autoimmune manifestations in MRL-lpr/lpr model mice.