用热释光法测量32P球囊和103Pd支架在血管内的剂量分布

本研究采用模拟实验方法，分别对^103Pd支架(简称支架)和^32P球囊(简称球囊)在血管内的剂量分布进行了测量，现报道如下。     

103Pd支架预防兔髂动脉支架后再狭窄的实验研究

目的 探讨^103Pd支架置入对兔髂动脉支架后再狭窄的预防作用。方法 20只新西兰大白兔按支架放射性活度分为6组[2．22(n=3)，5．55(n=4)，9．25(n=4)，14．8(n=3)。22．2(n=3)，33．3MBq(n=3)]，于每只动物一侧髂动脉内置入不同活度的^103Pd支架，对侧髂动脉内置入非放射性支架作对照。高脂饲养28d后进行髂动脉血管造影和定量组织病理学分析，观察治疗效果。结果 组织病理学定量分析示不同剂量^103Pd支架组新生内膜面积和狭窄百分比均明显低于对照组，但其效应不呈明显剂量依赖性。结论 ^103Pd支架能明显抑制支架置入后兔髂动脉新生内膜增生和支架后再狭窄的发生。     

32P液体球囊在血管内吸收剂量的研究

目的　研究32 P球囊在血管内的剂量分布。方法　用肌肉等效材料代替血管壁 ,采用热释光剂量学方法模拟测量靶血管轴向和径向吸收剂量率分布 ,并对相关影响因素 (球囊内压力 ,气泡 )进行了研究。结果　 3 0mm× 2 0mm 32 P球囊 ,活度为 92MBq时 ,血管表面平均吸收剂量率为0 48Gy min ,在径向 0 4mm处为 0 2 2Gy min。结论　血管壁表面剂量分布较均匀 ,径向剂量随距离迅速衰减 ,但存在诸多影响因素。     

103Pd对血管平滑肌细胞增殖和凋亡影响的实验研究

目的：研究^103Pd对血管平滑肌细胞（SMC）增殖和凋亡的影响。方法：将不同剂量^103Pd溶液加入SMC培养液中，72h时加入^103Pd衰变液作对照；应用^3H-TdR参入实验研究^103Pd对SMC增殖的影响，应用流式细胞仪检测^103Pd对SMC凋亡的影响。结果：^103Pd能明显抑制SMC增殖，并呈剂量依赖性。1.85MBq^103Pd对SMC增殖的抑制率为2.3％，几乎不能抑制SMC增殖；^103Pd剂量从7.4MBq增加到37.0MBq，增殖抑制率从41.6％上升至91.2％上升至91.2％，SMC增殖受到明显抑制。1.85-37.0MBq^103Pd均不能诱导SMC的明显凋恨，其凋亡率均小于4.0％。结论：^103Pd在体外能有效抑制SMC增殖。^103Pd抑制新生内膜形成的机制主要是抑制SMC增殖，而非诱导SMC的大量凋亡。     

β源支架剂量分布的蒙特卡罗算法

目的 比较数值积分和蒙特卡罗方法计算的放射性支架的剂量率分布。方法 以3种有代表性的剂量点核函数为计算模型，计算支架的剂量率分布。结果 分别计算了中心面的径向，支架表面及离支架表面0.5mm处的轴向剂量分布，径向最大差异为1．5％，轴向的差异也有1．5％之内。结论 3种函数用数值积分和蒙特卡罗方法计算的剂量分布是一致的，蒙特卡罗方法可用来计算放射性支架的剂量分布。     

血管内近距离放射治疗剂量影响因素的研究

目的　研究32 P球囊预防血管再狭窄的影响因素。方法　采用组织等效血管和热释光剂量学方法。结果　 2 5mm× 2 0mm空球囊内残留32 P对血管壁造成的剂量影响是 0 92Gy min。当球囊内导管偏离中心时 ,球囊外表面的吸收剂量将降低 2 0 %。气泡位置处的吸收剂量比球囊外表面平均吸收剂量低约 30 %。结论　32 P球囊表面轴向剂量分布较均匀 ,但径向吸收剂量随距离增加迅速减少。血管内近距离放射治疗有很好的临床应用前景。     

103Pd支架预防血管成形术后再狭窄量效关系研究

目的　探讨1 0 3Pd支架对血管成形术后再狭窄预防作用的量效关系及是否导致边缘再狭窄。方法　 5 0只雄性新西兰兔随机分为普通支架组和核素支架各剂量组 (8只 组 )。支架植入术后 8周行腹主动脉血管内超声和造影检查。结果　核素支架组随剂量增加 ,支架段血管最小内径和支架段血管管腔切面积均增大 ,狭窄程度减小 ;核素支架 2 5及 35Gy组支架边缘段血管管腔内增生内膜切面积及外弹力板切面积变化 (缩小值 )均小于普通支架组 (P <0 .0 5 )。结论　1 0 3Pd支架可抑制支架内内膜增生 ,减轻支架内狭窄程度 ,且不引起边缘再狭窄。     

国产血管内^192Ir线源的放射剂量测定

目的 对国产血管内^192Ir线源的剂量分布进行评价，为动物实验和临床应用提供依据。方法 采用KodakX-omatV慢感光胶片，从平行和垂直于放射源长轴方向进行测量，径向测量时间为25、45、65和82s，轴向测定时间为25s，同时进行标准剂量的标定，通过胶片自动分析测量系统分析剂量分布和吸收剂量。参考AAPM TG No.60报告，采用Monte Carlo方法对放射源和辐射剂量进行理论计算，同时与采用AAPM TG No.43报告计算方法进行比较。结果 国产血管内^192Ir线源具有良好的剂量分布。AAPMTGNo.43报告计算方法比Monte Carlo方法高估32％的辐射剂量。结论国产^192Ir线源作为血管内放射源是可行的，采用慢感光胶片测定放射源的剂量分布是一种有效手段。     

103Pd种子源植入治疗肿瘤近期疗效观察

目的评估^103Pd种子源植入治疗恶性肿瘤的近期疗效。方法2l例确诊的恶性肿瘤患者，由治疗计划系统(TPS)通过不同术式植入^103Pd种子源(196．1—2127．5MBq)，其中15例采用均-布源，6例前列腺癌采用中心消融，外周布源。观察肿瘤大小、局部复发和远处转移情况；并按肿瘤放射协作组，欧洲肿瘤研究及治疗(RTOG／EORTC)急性或后期放疗副作用评分标准进行评分。结果随访期内2l例患者均未见局部复发和远处转移，RTOG／EORTC评分为0分19例，占90．5％，1分2例。占9．5％。结论^103Pd种子源植入治疗肿瘤近期效果安全可行。     

32P液体球囊在血管组织中的剂量分布

目的　研究放射性液体球囊治疗冠状动脉再狭窄时在血管组织内的剂量分布。方法　用模拟实验和理论计算两种方法估算剂量分布。结果　模拟测量和理论计算的剂量平均值分别为 9 0 ,9 7mGy·min-1 ,两者差异为 7 8%。结论　3 2 P液体球囊的剂量分布在轴向上均匀 ,在径向上快速衰减     

Absorbed dose calculations to blood and blood vessels for internally deposited radionuclides

At present, absorbed dose calculations for radionuclides in the human circulatory system used relatively simple models and are restricted in their applications. To determine absorbed doses to the blood and to the surface of the blood vessel wall, EGS4 Monte Carlo calculations were performed. Absorbed doses were calculated for the blood and the blood vessel wall (lumen) for different blood vessels sizes. The radionuclides chosen for this study were those commonly used in nuclear medicine. No penetration of the radionuclide into the blood vessel was assumed nor was cross fire between the vessel assumed. The results are useful in assessing the dose to blood and blood vessel walls for different nuclear medicine procedures.     

Assessment of radiation safety instructions to patients based on measured dose rates following prostate brachytherapy

PURPOSE: To validate radiation safety instructions to patients and to evaluate the potential radiation doses to members of the public after (125)I or (103)Pd prostate implantation. METHODS AND MATERIALS: Radiation dose rate measurements were made in the immediate postoperative period on 636 consecutive patients with stage T1-T2 prostate cancer who underwent transperineal (125)I or (103)Pd implantation at Memorial Sloan-Kettering Cancer Center during the period from August 1995 through January 2003. RESULTS: The mean radiation dose rate at the anterior skin surface following a prostate implant was 37 microSv/hr for (125)I and 8 microSv/hr for (103)Pd. At 30 cm from the anterior skin surface, these dose rates were reduced to 6 microSv/hr for (125)I and 3 microSv/hr for (103)Pd. At 1 m from the anterior skin surface the dose rates from both types of implants were reduced to less than 1 microSv/hr. The effect of body weight on dose rates from (125)I sources was examined for a select sub-group of patients and the measured dose rate was found to decrease with increasing body weight. In another group of patients, dose rate measurements were made on both lateral skin surfaces and were less than 16.8 microSv/hr in all cases. Assuming a 33% occupancy factor and utilizing the mean measured dose rate for (125)I, the time required to reach an effective dose equivalent limit of 5 mSv for caregivers was estimated to be 19 days on contact with the skin surface. Using a similar calculation, the lifetime doses for (125)I at a distance of 30 cm from the anterior skin surface, as well as the lifetime doses for (103)Pd on contact with the skin surface and at 30 cm from the anterior skin surface can be shown to be less than 5 mSv. CONCLUSIONS: The large number of cases available for this study permits a validation of radiation safety recommendations and provides concrete information from which the permitted exposure times following implantation can be estimated. The data support the conclusion that patients treated with these implants do not represent a radiation risk to members of the public.     

Whole-body distribution and dosimetry of O-(2-[18F]fluoroethyl)-L-tyrosine

The whole-body distribution of O-(2-[(18)F]fluoroethyl)- l-tyrosine (FET) was studied in seven patients with brain tumours by positron emission tomography (PET). Based on the IMEDOSE and MIRDOSE procedures, radiation absorbed doses were estimated from whole-body PET scans acquired approximately 70 and 200 min after i.v. injection of 400 MBq FET. After injection of FET, the peak of radioactivity in the blood was observed after 1.5 min, and a plateau of nearly constant radioactivity was reached at 20 min. The whole-body distribution of FET showed the highest activities in the urinary tract. All other organs exhibited only moderate FET uptake (SUV 相似文献   

Dose rate dependence of the relative biological effectiveness of 103Pd for continuous low dose rate irradiation of BA1112 rhabdomyosarcoma cells in vitro relative to acute exposures

PURPOSE: To measure the relative biological effectiveness (RBE) of continuous low dose rate irradiation (CLDRI) using 103Pd sources relative to acute high dose rate irradiations (AHDRI) from a 250 kVp x-ray beam and an x-ray beam having an equivalent mono-energetic photon energy equal to the average energy of the 103Pd source for BA1112 rhabdomyosarcoma cells. MATERIALS AND METHODS: A customized 103Pd irradiator was built to provide CLDRI using 103Pd at different dose rates relevant to clinical interstitial brachytherapy to BA1112 rhabdomyosarcoma cells growing in exponential phase in culture. A special x-ray beam that simulates the photon energies emitted by the 103Pd source was also developed to provide acute high dose rate irradiation at those energies. Cell survival curves from different irradiation conditions were measured. The RBE with respect to AHDRI using standard 250 kVp x-rays was determined from the doses required to achieve a cell surviving faction of 0.01. RESULTS: For acute irradiation, the RBE of the x-rays simulating (103)Pd was 1.24 relative to 250 kVp x-rays. A profound dose rate effect was observed at low dose rates in the range of 6.8 - 14.4 cGy/h that are typical of permanent interstitial brachytherapy. At cell-surviving fraction of 0.01, the RBE of CLDRI at 6.8 and 14.4 cGy/h using 103Pd sources was reduced by a factor of 3 and 2, respectively, relative to the acute exposure. This observation is in good agreement with recent in vivo tumor cure studies performed on BA1112 tumor. CONCLUSION: The relative biological effectiveness of the photons emitted by 103Pd depends on both the linear energy transfer (LET) of the low energy photons and the dose rate of the irradiation. The higher LET of 103Pd photons is biologically more effective in killing BA1112 tumor cells compared to conventional 250 kVp x-rays when both are delivered at the same dose rate. But the gain in RBE that results from the higher LET can be quickly negated by the reduced dose rate of the irradiation.     

103Pd放射性支架持续照射犬胆管的放射性损伤的实验研究

目的　寻找动物胆管金属内支架植入方法 ,观察动物胆管植入1 0 3 Pd放射性支架 ,胆管腔内照射的放射性损伤。方法　实验动物为雄性健康杂种犬 ,体重 1 5～ 2 0kg。麻醉下经手术植入1 0 3 Pd放射性金属支架于犬的胆管腔内 ,1 0 3 Pd的放射性活度分别为 1 2 5× 1 0 4kBq、1 6 6× 1 0 4kBq、2 2 2× 1 0 4kBq、2 5 9× 1 0 4kBq、2 9 6× 1 0 4kBq和 3 7× 1 0 5kBq ,植入后 30d取出1 0 3 Pd放射性金属支架和胆管 ,后者经组织切片HE染色 ,光镜下进行放射性损伤的评价。结果　放射性活度为 1 2 5× 1 0 4kBq ,光镜下可观察到黏膜损伤 ;放射性活度为 2 2 2× 1 0 4kBq时胆管放射性损伤达肌层 ;放射性活度为3 7× 1 0 5kBq时放射性损伤达胆管壁外膜 ,出现胆管穿孔。根据不同放射性活度照射后 ,胆管的放射性损伤的放射性活度效应曲线得出 ,ED50 为 2 8 2× 1 0 4kBq。结论　1 0 3 Pd金属支架胆管腔内近距离照射有明显的剂量 效应关系 ,为该放射性支架应用于临床治疗胆管良、恶性狭窄提供重要的实验依据     

Three-dimensional radiobiologic dosimetry: application of radiobiologic modeling to patient-specific 3-dimensional imaging-based internal dosimetry.

Phantom-based and patient-specific imaging-based dosimetry methodologies have traditionally yielded mean organ-absorbed doses or spatial dose distributions over tumors and normal organs. In this work, radiobiologic modeling is introduced to convert the spatial distribution of absorbed dose into biologically effective dose and equivalent uniform dose parameters. The methodology is illustrated using data from a thyroid cancer patient treated with radioiodine. METHODS: Three registered SPECT/CT scans were used to generate 3-dimensional images of radionuclide kinetics (clearance rate) and cumulated activity. The cumulated activity image and corresponding CT scan were provided as input into an EGSnrc-based Monte Carlo calculation: The cumulated activity image was used to define the distribution of decays, and an attenuation image derived from CT was used to define the corresponding spatial tissue density and composition distribution. The rate images were used to convert the spatial absorbed dose distribution to a biologically effective dose distribution, which was then used to estimate a single equivalent uniform dose for segmented volumes of interest. Equivalent uniform dose was also calculated from the absorbed dose distribution directly. RESULTS: We validate the method using simple models; compare the dose-volume histogram with a previously analyzed clinical case; and give the mean absorbed dose, mean biologically effective dose, and equivalent uniform dose for an illustrative case of a pediatric thyroid cancer patient with diffuse lung metastases. The mean absorbed dose, mean biologically effective dose, and equivalent uniform dose for the tumor were 57.7, 58.5, and 25.0 Gy, respectively. Corresponding values for normal lung tissue were 9.5, 9.8, and 8.3 Gy, respectively. CONCLUSION: The analysis demonstrates the impact of radiobiologic modeling on response prediction. The 57% reduction in the equivalent dose value for the tumor reflects a high level of dose nonuniformity in the tumor and a corresponding reduced likelihood of achieving a tumor response. Such analyses are expected to be useful in treatment planning for radionuclide therapy.     

Dosimetry of iodine-123 iomazenil in humans

The distribution of the central benzodiazepine receptor specific ligand iodine-123 iomazenil was investigated in seven human adults from whole-body scans, blood samples and urine collected up to 24 h after injection. Using 12 source organs, the MIRD method was applied to calculate the absorbed radiation dose of the radioligand in various organs. The urinary bladder wall (0.15 mGy/MBq), lower large intestinal wall (0.071 mGy/MBq) testes (0.044 mGy/MBq) and upper large intestined wall (0.038 mGy/MBq) received the highest absorbed doses. The average effective dose equivalent of ¹²³I-IBZM for adults was estimated to be 0.033 mSv/MBq.     

Dosimetry of rhenium-188 diethylene triamine penta-acetic acid for endovascular intra-balloon brachytherapy after coronary angioplasty

To examine the possibility of using rhenium-188 diethylene triamine penta-acetic acid (DTPA) for endovascular intra-balloon brachytherapy after angioplasty, dose distribution around the balloon was calculated and validated by film dosimetry. Medical internal radiation dosimetry (MIRD) was calculated assuming that the balloon had ruptured and that the contents had been released into the systemic circulation. 188Re-perrhenate eluate from the 188W/188Re generator was concentrated using an ion column and used to label DTPA. The dose distribution around the angioplasty balloon (20 mm length, 3 mm diameter cylinder) was estimated by Monte Carlo simulation using the EGS4 code. The time required for 17.6 Gy to be absorbed at 1 mm from the balloon's surface following application of 3700 MBq/ml of 188Re was found to be 278 s. Fifty percent of the energy was deposited in the first millimetre of the vessel wall from the balloon's surface. The calculated radiation absorbed dose agreed with that measured by film dosimetry, which was performed using a water phantom, with errors ranging from 9.4% to 17%. Upon balloon rupture the total amount of 188Re-DTPA was presumed to enter the systemic circulation. The resulting radiation absorbed dose was calculated using the MIRDOSE3 program and residence times obtained from dogs and amounted to 0.0056 mGy/MBq to the whole body and 4.56 mGy/MBq to the urinary bladder. The absorbed dose of 188Re-DTPA to the whole body was one-tenth of that of 188Re-perrhenate. A window-based program was developed to calculate the exposure time and the radiation dose absorbed as a function of the 188Re concentration and the arbitrary distance from the balloon to the surrounding tissues. We conclude that 188Re-DTPA is easy to prepare, safe to use and suitable for intra-balloon brachytherapy after coronary angioplasty.     

32P-磷酸铬-聚L乳酸粒子组织间植入对犬长期毒性研究

目的 探讨³²P-磷酸铬-聚L乳酸粒子(³²P-CP-PLLA)间质植入比格犬的安全性和毒性。方法 30只比格犬,随机分成不同药物(³²P-CP-PLLA和胶体³²P-CP)、剂量(185、370和740 MBq)和部位(肝脏和臀大肌)10组(n=3)。术后定期称体重,检测实验室指标,测量血液、排泄物放射性计数率值,动态γ显像和组织形态学观察。结果 γ显像示胶体肝脏组全肝显影,放射性不均匀分布,余组局部放射性持续浓聚,肝脏未见显影。肝内注射胶体³²P-CP 471.67 MBq/m²,全肝吸收剂量为31 Gy,无肝功能损伤;注射794.28 MBq/m²,全肝吸收剂量为56 Gy,有较强的肝毒性及全身毒副作用。肝内植入1588.89 MBq/m²的³²P-CP-PLLA粒子,植入区肝组织的吸收剂量为89.83~178.68 Gy,未见肝功能受损。肝脏胶体370 MBq组分别于23、29和45 d死亡肝纤维化5项全程均值明显高于其他各组。有效半减期:³²P-CP-PLLA平均为11.78 d;³²P-CP肝脏组为6.82 d,肌肉组为8.73 d。组织学表现:肝脏胶体370 MBq组4周内见肝细胞中、重度肝细胞损伤,4~6周出现肝细胞坏死及增生;其余各组4周内见轻~中度肝细胞水肿,8周后未见异常。肌肉给药各组主要表现为横纹肌细胞一过性水肿变性。 血液中放射性计数率值粒子组随时间呈现锯齿状缓慢递减,胶体组呈指数下降。结论 ³²P-CP-PLLA粒子具有在植入部位不迁移,可体内降解,无明显毒副作用等优良特性,适治于不同血供的实体肿瘤。比格犬肝脏能接受³²P-CP致死剂量2倍活度的放射性粒子的辐射。