99Tcm-MIBI在小鼠肝脏细胞核内的吸收剂量分布研究

目的：尝试建立了一种微剂量估算模式，评估靶细胞核对放射性红物的准确吸收剂量率。方法：以^99Tc^m－甲氧基异丁基异腈（MIBI）为例，运用冰冻切片光镜放射自显影技术。观察小鼠尾静脉注射^99Tc^m-MIBI2h后，肝脏内放射性药物在亚细胞水平分布情况，探索一种符合实际分布情况的数学模式来估算肝细胞核的微剂量率，并与医学内照射剂量（MIRD）估算方式比较，判断两种剂量率估算方法的准确性。结果：^99Tc^m-MIBI在肝脏亚细胞水平的分布是不均匀的，实际肝细胞核微剂量率数值与利用MIRD模式估算的结果差异有非常显著性（P＜0．01）.结论：在^99Tc^m标记药物非均匀分布情况下，本文作者所建立的微剂量率估算模型，可替代MIRD模式，较准确地估算微剂量率。     

99mTc-DTPA细胞水平分布的实验研究

目的核医学中传统的MIRD剂量估算方法是假设放射性药物在器官内均匀分布,用器官的平均剂量描述每个细胞及细胞核的剂量.基于核素的微观分布数据,建立微剂量的剂量估算模式,从而为核医学中诊疗计划的制定、放射药物效果和危害的预测及评价、分子核医学研究提供基础的微剂量估算及其分布研究的方法和基础数据.方法采用了放射自显影术和冰冻切片技术,建立自显影银颗粒密度与放射性药物强度的刻度曲线,确定放射性药物99mTc-DTPA的微观分布.结果银颗粒密度与施入比活度的相关系数为0.9915,刻度系数为6.48×10-5Bq.细胞浆与细胞核的分布比为1.78.结论放射性药物在细胞水平的分布是不均匀的,因此在计算细胞水平的剂量时应考虑到其分布的不均匀性.     

外照射后肿瘤摄取99Tcm-MIBI与其死亡和增殖的关系

目的 探讨^99Tc^m－甲氧基异丁基异腈（MIBI）显像监测肿瘤放疗后细胞活力变化的可行性。方法 105只荷Ehrlich癌的雌性昆明小鼠按不同剂量（0、5、10、15、20Gy）行^60Co单次照射，并于照射前6h及照射后24、72和144h分别进行①^99Tc^m－MIBI显像及测量肿瘤组织放射性计数，计算肿瘤微分摄取率（DUR）及肿瘤与对侧正常组织的放射性比值（T／NT）；②测定肿瘤凋亡指数（AI）、肿瘤坏死面积百分比（PNA）和增殖细胞核抗原（PCNA）免疫组化染色积分吸光度（PCNA－IA）结果 照射后DUR、T／NT随剂量、时间的增加而逐渐减少。24h DUR、T／NT分别与增高的AI、PNA呈负相关，与减低的PCNA－IA呈正相关，r分别为－0．849、－0．829；－0．883、－0．855；0．789、0．742（n =33,P＜0．01）。     

^99Tc^m—MIBI显像检测乳腺癌多药耐药

探讨了乳腺癌组织的多药耐药现象的主要机制及P－糖蛋白（P－gp）、胎盘型谷胱甘肽硫转移酶（GST－π）与^99Tc^m－MIBI显像的关系。尽管献报道的实验结果不尽相同，但作为一种功能显像技术，^99Tc^m－MIBI SPECT显像能够用来研究乳腺癌细胞P－gp的表达，可以在体外无创性检测乳腺癌多药耐药，为指导乳腺癌的治疗提供参考。     

定量门控99Tcm-MIBI/201Tl心肌显像左心室射血分数正常参考值的建立

目的：应用定量门控^99Tc^m－甲氧基异丁基异腈（MIBI）和^201T1心肌显像测量静息左心室射血分数（LVEF），建立其正常参考值。方法；对277例患冠心病（CAD）低风险概率（＜10％）受检者行运动负荷－静息门控心肌断层显像。受检者分^99Tc^m－MIBI组（110例）和^201T1组（167例），各组再分无高血压（HBP）亚组（^99Tc^m－MIBI组85例，^201T1组128例）和HBP不伴左室肥厚9LVH）亚组（^99Tc^m－MIBI组25例，^201T1组39例）。采用QGSPECT专用分析程序测量静息LVEF。结果：^99Tc^m－MIBI组和^201T1组中HBP亚组的静息LVEF值均明显高于无HBP亚组（P均＜0．05），无HBP男性患者的静息LVEF值明显低于女性患者（P＜0．01）；无HBP者的心率、年龄与静息LVEF值间无线性相关（P均＞0．05）。^99Tc^m－MIBI组和^201T1组静息LVEF值均呈正态分布，其静息LVEF正常参考值分别为≥45％和≥43％。考虑性别影响，则^99Tc^m－MIBI组男性≥45％，女性≥48％；^201T1组男性≥42％，女性≥47％。结论：LVEF正常参考值有潜在的临床价值。     

冰冻切片放射自显影技术在微剂量研究中的应用

目的 用放射自显影技术观察放射性核素在细胞水平的分布。方法 采用放射自显影和冰冻切片技术,建立银颗粒密度与放射性药物强度的刻度曲线,确定放射性药物131I和99mTc的微观分布,基于核素的微观分布数据,建立微剂量的剂量估算模式。结果 银颗粒密度与施入放射性药物比活度的相关系数分别为0.9915和0.9963,刻度系数分别为1.59×10-4Bq和6.48×10-5Bq。结论 131I和99mTc在细胞水平的分布是不均匀的,银颗粒多数分布在细胞质中,因此在计算细胞水平的剂量时应考虑到其分布的不均匀性。     

^99Tc^m—MIBI用于乳腺癌诊断的评价

^99Tc^m－MIBI（^99Tc^m－甲氧基异丁基异腈）用于乳腺癌原发病灶诊断具有较高的灵敏度、特异性和准确率，与其他检测技术的对比研究显示其具有良好的应用前景，与其他检测技术联合应用可进一步提高诊断的准确性。     

脑灌注显像剂99Tcm-MPBDA的研制与动物实验

目的 研制一种新的SPECT脑灌注显像剂。方法 将化学合成的N2S三齿配体2－巯基丙基－1,2－苯二胺（MPBDA）用^99Tc^m标记：25只昆明种小白鼠静脉注射100μL555-740kBq^99Tc^m-MPBDA进行体内生物分布实验;2只健康恒河猴（4－6kg)静脉快速注入218．3－333MBq^99Tc^mMPBDA或^99Tc^m双半胱乙脂（ECD）后分别即刻连续动态采集和给药后70min行全身显像和脑断层显像;2组小鼠和3只家兔分别进行了急性毒理和热原实验。结果 ^99Tc^m－MPBDA的产率和放化纯度分别大于95％和97％。小鼠体内分布实验结果表明^99Tc^m－MPBDA能在脑内浓聚并具有很好的脑滞留,血清除半衰期小于15min。猴脑动态血流灌注显像示注药后2min脑放射性达高峰,1h脑放射性占2min的83．0％,70min后入脑量高达2．76％ID,略低于^99Tc^m－ECD（2．9％ID）。断层显像可见大脑灰白质对比度好,影像轮廓较清晰。小鼠和兔子注射^99Tc^m－MPBDA后均无毒副反应。结论 研制的^99Tc^m－MPBDA具有^99Tc^m－ECD相近的脑血流灌注显像性能,用于活体安全可靠。     

99 Tcm-HL91脑缺血半暗带显像的实验研究

目的 观察^99Tc^m－4，9－二氮－3，3，10，10－四甲基十二烷－2，11－二酮肟（HL91）在局部脑缺血模型脑组织中分布特点。方法 建立31只大鼠避部脑缺血模型，对^99Tc^m－HL91在正常大鼠体内以及在动物模型脑组织中的分布进行研究，同时对动物模型脑组织行放射自显影研究。结果 ^99Tc^m－HL91静脉注射后主要分布于肝、肾、小肠，正常脑组织放射性较低。患／健侧大脑中动脉主要供血区（靶区）单位质量放射性比值与对照组相比差异均有显著性，且随时间的延长而逐渐增高。动物模型脑组织自显像图像均可见靶区放射性明显高于对侧镜像部位，经计算机图像分析系统进行图像分析和数据处理后，同一时相靶与非靶区单位面积净吸光度值差异有显著性，各时相靶／非靶比值与对照组比较差异均有显著性，且随注射药物时间的延长而增高。结论 ^99Tc^m－HL91能够选择性地浓集于缺血缺氧的脑组织中，清除延缓，可用于急性脑卒中缺血半暗带的探测。     

hNIS基因的组织特异性表达介导肝癌细胞摄取99Tcm

目的探讨人钠／碘同向转运体（hNIS）基因在肝癌细胞中的组织特异性表达介导^99Tc^m摄取的可行性。方法构建鼠白蛋白基因启动子／增强子（mAlb）引导下hNIS和潮酶素共同表达的逆转录病毒载体，该重组逆转录病毒感染大鼠肝癌细胞MH3924A建立稳定表达细胞系，用^125I摄取实验证实hNIS基因的功能表达。建立肝癌移植瘤大鼠模型。在体内和体外水平评价重组肝癌细胞对^99Tc^m的摄取和流出。绘制时间-放射性曲线和体内外放射性分布图。结果重组质粒构建成功。体外培养条件下，hNIS基因稳定转染细胞系摄取^99Tc^m高出野生型肝癌细胞254倍。50μmol／L NaClO3和500μmol／L哇巴因（Ouabain）可分别使MHm AlbhNIS6细胞摄取^99Tc^m降低97．56％和88．20％（P均〈0．01）。而^99Tc^m流出迅速，有效半减期不足2min，应用^99Tc^m／γ相机系统获得了转染肿瘤的清晰图像及定量数据，注射^99Tc^m O4^-后30min，MHmAlbhNIS6细胞形成的移植瘤摄取^99Tc^m比对照组高4倍。结论证实hNIS基因在肝癌细胞中的组织特异性表达介导^99Tc^m摄取；利用^99Tc^m／γ相机系统可无创、简单、定量检测hNIS基因的表达。     

Effects of mucus thickness and goblet cell hyperplasia on microdosimetric quantities characterizing the bronchial epithelium upon radon exposure

Purpose: The most exposed tissue upon radon exposure is the bronchial epithelium where goblet cells serve as responsive and adaptable front-line defenders. They can rapidly produce a vast amount of mucus, and can change in number, in response to airway insults. The objective of the present study is to quantify the effects of mucus discharge and goblet cell hyperplasia on the microscopic dose consequences of macroscopic radon exposures.

Methods: For this purpose, computational models of the bronchial epithelium and alpha-particle transport have been prepared and applied to quantify the hits received and doses absorbed by cell nuclei in case of different mucus thicknesses and goblet cell number.

Results and conclusions: Both mucus discharge and induction of goblet cell hyperplasia reduce radiation burden at the cellular level, and as such they both can be considered as radioadaptive responses to radon exposure. As compared to basal cell hyperplasia, goblet cell hyperplasia is more effective in reducing the microscopic dose consequences of a given macroscopic exposure. Such changes in exposure geometry highlight the need for improvements in the application of biokinetic and dosimetry models for incorporated radionuclides as well as the dose and dose rate effectiveness factor.     

Yttrium-90 Activity Quantification in PET/CT–Guided Biopsy Specimens from Colorectal Hepatic Metastases Immediately after Transarterial Radioembolization Using Micro–CT and Autoradiography

PurposeTo evaluate the yttrium-90 (⁹⁰Y) activity distribution in biopsy tissue samples of the treated liver to quantify the dose with higher spatial resolution than positron emission tomography (PET) for accurate investigation of correlations with microscopic biological effects and to evaluate the radiation safety of this procedure.Materials and MethodsEighty-six core biopsy specimens were obtained from 18 colorectal liver metastases (CLMs) immediately after ⁹⁰Y transarterial radioembolization (TARE) with either resin or glass microspheres using real-time ⁹⁰Y PET/CT guidance in 17 patients. A high-resolution micro–computed tomography (micro-CT) scanner was used to image the microspheres in part of the specimens and allow quantification of ⁹⁰Y activity directly or by calibrating autoradiography (ARG) images. The mean doses to the specimens were derived from the measured specimens’ activity concentrations and from the PET/CT scan at the location of the biopsy needle tip for all cases. Staff exposures were monitored.ResultsThe mean measured ⁹⁰Y activity concentration in the CLM specimens at time of infusion was 2.4 ± 4.0 MBq/mL. The biopsies revealed higher activity heterogeneity than PET. Radiation exposure to the interventional radiologists during post-TARE biopsy procedures was minimal.ConclusionsCounting the microspheres and measuring the activity in biopsy specimens obtained after TARE are safe and feasible and can be used to determine the administered activity and its distribution in the treated and biopsied liver tissue with high spatial resolution. Complementing ⁹⁰Y PET/CT imaging with this approach promises to yield more accurate direct correlation of histopathological changes and absorbed dose in the examined specimens.     

In vivo localization of Ga-citrate in rat liver as determined by cell fractionation with isopycnic rate-zonal ultracentrifugation

The in vivo behaviour of Ga-67 citrate was studied, using a rat liver model, and the mechanisms of cellular uptake were investigated by observing the time course of the raidonuclide in subcellular liver cell fractions. Modified continuous ultracentrifugation was used to successively fractionate the homogenates according to isopycnic and rate-zonal principles. To collect the cell nuclei, a special technique, which consisited of supplementing the outer sucrose layer with cesium chloride to increase density, was applied to trap nuclei with isopycnic equilibrium. We isolated nuclei, mitchondria, lysosomes and peroxysomes, microsomes, and the cell supernatant in a sufficiently purified state. By this method, the in vivo localization of Ga-67 was studied. At 30 min after intravenous injection, radioactivity was found mainly in the cell supernatant, the radioactivity peak corresponded to 5 S. However, after 24 h, the radioactivity was localized in the heavier fraction containing lysosomes and heavy endoplasmic reticulum. No intranuclear localization was observed. In spite of the difficulty in completely separating the lysosomal fraction from heavy endoplasmic reticulum, our results suggest the participation of heavy endoplasmic reticulum in gallium localization.     

Nonuniformity of tumor dose in radioimmunotherapy

The conventional approach to calculating tumor radiation dose from internally administered radioisotopes is by the MIRD schema. The raw input data for such dose calculations is obtained by immunoscintigraphic methods, PLANAR or SPECT imaging. Limitations in the spatial resolution of these techniques can lead to a considerable underestimate of the gross variation in tumor dose. The use of radiolabeled monoclonal antibodies for therapy can result in large nonuniformities in tumor dose. This paper discusses how antibody distribution can influence the energy deposition in the nuclei of target cells. Heterogeneity of antibody binding will lead to an expected decrease in the effectiveness of the radiation delivered. However, enhanced cell killing is possible if the radiolabeled Ab binds to the cell surface membrane and may be further enhanced if the Ab is internalized. Calculations are presented for two cases: (a) a three-dimensional random packing arrangement of cells as a model of the astructural nondifferentiated form seen in some tumors, and (b) differentiated carcinoma of the colon with the cells in tubules. Results for the magnitude of the mean energy deposition to individual cell nuclei from: (a) cell membrane bound 211At, 199Au, 131I, and 90Y-labeled Abs, and (b) a uniform distribution of these sources, as a function of internuclear distance for the two histologies are presented. Energy deposition in tumor cell nuclei from membrane bound radiolabeled antibody may be several times greater than estimated with the assumption of a uniform source distribution.     

Some microdosmetric data on Astatine-211.

Radionuclides which emit short range, high LET radiations such as alpha and Auger electrons have very promising applications in cancer therapy. Such radionuclides should eventually be incorporated into cell nuclei to achieve high radiotoxic effectiveness. This means that the dose distribution within the cell nucleus at microscopic levels is very important for comparison of the real differences between the radiotoxic effectiveness of different radionuclides. An experimental setup to determine real dose absorption on the microscopic scale is extremely difficult to design. For this reason, calculation procedures for microscopic dose absorption are of special interest for the diagnostic and therapeutic applications of radionuclides which emit short-range and high LET radiations. A specific calculation method for microscopic energy absorptions within the cell nucleus from Auger electrons of 125I was described earlier. In this study, the radiotoxic effectiveness of 211At and 125I has been compared using the data obtained by this calculation method. The data obtained show clearly that the radiotoxicity of the alpha and Auger emitter radionuclide 211At is comparable to that of 125I.     

Quantitative ex vivo and in vitro receptor autoradiography using 11C-labeled ligands and an imaging plate: a study with a dopamine D2-like receptor ligand [11C]nemonapride.

Ex vivo and in vitro autoradiography (ARG) with radioluminography is a useful technique to characterize newly developed 11C-labeled positron emission tomography (PET) tracers and to apply them to biological and pharmacological studies. In this report, we have described a method of evaluating the radioactivity distribution quantitatively in ex vivo and in vitro ARG using imaging plates and a dopamine D2-like receptor ligand [11C]nemonapride as a model compound. The photo-stimulated luminescence (PSL) values of the rat brain section provided by the imaging plates showed an excellent linear relationship with the radioactivity in a wide range under constant slice-thickness, although the PSL values slightly decreased with increasing slice-thickness both in ex vivo and in vitro ARG. The injection dose of 11C-tracers for ex vivo ARG was also discussed. We found saturable binding sites of [11C]nemonapride in the cortex besides the striatum both ex vivo and in vitro.     

Dosimetry at the cellular level of Kupffer cells after technetium-99m-sulphur colloid injection.

The radiation dose to Kupffer cells was estimated at the cellular level after intravenous injection of 99mTc labeled sulphur colloids in rats. The results were then compared with those obtained using macroscopic dosimetry. From the microscopy appearance observed using a "track" microautoradiographic method (MAR), it was shown that only 0.2% of the Kupffer cells were actually involved in the pinocytosis of radioactive colloids. For each electronic emission from 99mTc (Auger and internal conversion), the fraction of the emitted energy actually absorbed within the Kupffer cell was calculated using the values provided by Berger. About 15% of the total energy emitted by electrons was absorbed in 0.2% of the Kupffer cells. If these results are extrapolated to humans, the dose absorbed by the labeled cells can be estimated to be between 0.5 and 0.9 Gy/MBq. This represents about 15,000 times the average electron dose to the liver as estimated from macrodosimetric methods. In cases such as this one where an important distribution heterogeneity is expected, dosimetric estimations at a cellular level may be particularly useful.     

Effects of Anaesthetic Agent on [31P]NMR High-energy Phosphates and Regional Distributions of Intravascular Oxyhaemoglobin Saturations

Abstract

Purpose: The biological response of tissue exposed to radiations emitted by internal radioactivity is often correlated with the mean absorbed dose to a tissue element. However, experimental studies show that even when the mean absorbed dose to the tissue element is constant, the response of the cell population within the tissue element can vary significantly depending on the distribution of radioactivity at the cellular and multicellular levels. The present work develops theoretical models to simulate these observations.

Materials and methods: Two theoretical models were created to simulate experimental three-dimensional cell culture models with homogeneous and inhomogeneous tissue environments. The cells were assigned activities according to lognormal distributions of an alpha particle emitter or a monoenergetic electron emitter. Absorbed doses to the cell nuclei were assessed with point-kernel geometric-factor and Electron Gamma Shower version nrc (EGSnrc) Monte Carlo radiation transport simulations, respectively. The self- and cross-dose to individual cell nuclei were calculated and a Monte Carlo method was used to determine their fate. Survival curves were produced after tallying the live and dead cells.

Results: Both percent cells labeled and breadth of lognormal distribution affected the dose distribution at the cellular level, which in turn, influenced the shape of the cell survival curves.

Conclusions: Multicellular Monte Carlo dosimetry-models offer improved capacity to predict response to radiopharmaceuticals compared to approaches based on mean absorbed dose to the tissue.     

Kinetics of micronucleus induction by 125I-labelled thyroid hormone in hormone-responsive cells.

Two cell lines, CHO and GC, different in their tissue origin, were investigated with the aim of discovering the correlation between the level of 125I-T3 binding and chromosomal damage induced by 125I decay. Incubation of cells with 125I-T3 has been performed in two exposure schedules: continuous incubation for one to six cell cycles and a pulse-chase schedule involving exposure for one cell cycle. The cellular uptake of 125I-T3, its compartmentization and kinetics were different in the two cell lines. GC cells contained about 7 times more 125I-T3 than CHO cells when incubated with the same external 125I activity concentration (74 kBq of 125I-T3 ml-1 medium). Approximately 70% of the cellular 125I-T3 was found in nuclei of GC cells and only 5% in the nuclei of CHO cells. During the long-term incubation of GC cells with 74 kBq of 125I-T3 ml-1 medium, the 125I activity concentration in cells and their nuclei initially decreased by a half, and thereafter reached a plateau after the third doubling time. In CHO cells and nuclei a very slow linear increase of 125I activity was observed. In GC cells, micronucleus frequency was found to be correlated with nuclear 125I activity. One cell cycle pulse labelling with 74 kBq of 125I-T3 ml-1 medium caused a significant enhancement of micronucleus frequency above the control level during six doubling times, with a maximum at the first post-labelling doubling time. In GC cells continuously incubated with 74 kBq of 125I-T3 ml-1 medium, the micronucleus frequency increased with the incubation time. A model of T3 receptor-dependent dose delivery to nuclei of GC cells continuously incubated with 125I-T3 is proposed. The frequency of micronuclei in the CHO cell line continuously incubated with 125I-T3 did not differ significantly from the control, whereas in the pulse-chase schedule the mean frequency of micronucleated binuclear cells was lower during 4 post-labelling doubling times (significantly at the first and second post-labelling doubling time and insignificantly at the later doubling times) than in the control. Incubation of GC cells with various activity concentrations in medium for four cell cycles resulted in a linear increase of 125I activity in cells and nuclei; however, with a saturation in the region of highest 125I-T3 concentrations used. The frequency of binuclear cells bearing micronuclei was linearly dependent on the nuclear 125I-T3 concentration.