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。     

β核素球囊预防血管再狭窄的临床剂量估算

目的 探讨核素球囊内照射血管内的吸收剂量分布规律。方法 ①依据吸收剂量点核函数模拟计算^90Y、^186Re、^32P灌注球囊时血管组织中的吸收剂量率分布；②用非线性最小二乘法对吸收剂量率随球囊外径及组织深度的变化进行曲线拟合，并由此导出便于临床使用的经验公式。结果 球囊中吸收剂量率峰值出现在血管腔内球囊中，血管表面位于吸收剂量率曲线的拐点处，血管壁及周围组织中的吸收剂量率以近双指数方式下降。吸收剂量、持续照射时间、初始放射性浓度、组织深度及球囊外半径间的关系可用一经验公式表达。结论 血管组织中的β核素吸收剂量分布呈快速下降。该经验公式具有实用价值。     

用MCNP4b研究32P液体球囊吸收剂量分布

32P的液体β源球囊是治疗冠状动脉粥样硬化疾病的一种新方法,笔者曾报道32P液体球囊用Loevinger剂量点核解析函数计算的一维径向吸收剂量分布[1].本研究用模拟实验测量,改进的剂量点核函数和4b版蒙特卡罗输运代码(MCNP4b)3种方法估算32P液体球囊在血管模拟体内的吸收剂量.     

模拟测定103Pd放射性支架在血管中的剂量分布

目的 测定血管内^103Pd放射性支架的剂量分布。方法 采用肌肉组织等效材料代替血管壁，用热释光剂量计模拟测量血管内的剂量分布。结果 当支架活度为9．8MBq时，支架表面累积吸收剂量为9．8Gy(17d)。^103Pd支架表面的剂量分布随径向距离增加而迅速减少，在支架表面径向距离0．4mm处80％的剂量被血管壁吸收。结论 血管内^103Pd支架对血管周围的器官和组织无明显损害。     

188 Re液体血管内照射防治血管内膜损伤后再狭窄的实验研究

目的　研究1 88Re液体充盈球囊导管对兔血管再狭窄模型用不同剂量内照射后对增生内膜不同的剂量效应。方法　 16只新西兰白兔分成 2组 ,一侧下肢髂动脉行内膜剥脱术后 ,通过直径 2 5mm液体1 88Re充盈球囊导管分别给以 0、8和 15Gy剂量的血管内照射治疗。其中 8只兔的另一侧髂动脉仅行内膜剥脱术作为对照。 4周后处死动物 ,取出血管。组织经HE染色、VanGieson胶原染色、α 肌动蛋白免疫组化染色 ,通过图像分析系统分析 ,测定狭窄指数和增殖指数。结果　对照组、8和 15Gy组的狭窄指数分别为 0 49± 0 0 6、0 65± 0 0 5和 0 82± 0 0 5 ,增殖指数分别为 0 5 4±0 0 9、0 48± 0 0 6和 0 3 3± 0 0 4。 15Gy组增生的内膜明显下降 (P <0 0 5 ) ,而 8Gy组与对照组比较差异无显著性 (P >0 0 5 )。免疫组化显示增生的内膜主要是平滑肌细胞 (SMCs)。结论　在兔血管再狭窄模型中 ,用1 88Re液体充盈球囊导管内照射治疗 ,当接近血管内表面的吸收剂量达到 15Gy时能安全有效地抑制内膜平滑肌的增生     

放射性球囊内气泡对血管组织剂量分布的影响

目的：计算放射性球囊治疗冠状动脉再狭窄时球囊内气泡对血管的剂量分布影响。方法：采用Prestwich的剂量点核函数计算球囊周围的剂量分布，计算体积为0.02mL的气泡位于球囊壁中心和边缘两种情况下对球囊周围组织的剂量分布影响，并与无气泡的液体球囊比较。结果：气泡在球囊壁中心时，影响范围为4mm,球囊两侧的剂量不均匀最大可达38％；在边缘时，影响范围为6mm，剂量不均匀达47％。结论：球囊内气泡对血管组织的剂量分布有影响。     

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     

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。     

188Re灌注球囊照射预防兔血管再狭窄

目的观察188Re灌注球囊血管内照射对兔血管损伤后再狭窄的预防作用.方法应用球囊过度扩张损伤兔双侧髂动脉,随机选择一侧髂动脉进行188Re灌注球囊血管内局部照射,对受照射血管进行血管造影、组织病理学检查及增殖细胞核抗原(PCNA)染色分析.结果与非照射组血管比较,照射组血管直径较大[(1.94±0.19) vs (1.77±0.28) mm,P<0.05],新生内膜面积减少[(1.12±0.75) vs (2.17±1.21) mm2,P<0.01],狭窄面积百分比降低[(19.23±12.60)% vs (34.45±17.49)%,P<0.01],PCNA阳性率低[(3.75±2.09)% vs (5.64±1.74)%,P<0.05].0.5 mm深处组织吸收剂量为15 Gy.结论 188Re灌注球囊血管内照射能够抑制兔损伤血管再狭窄.     

国产血管内~(192)Ir线源的放射剂量测定

目的　对国产血管内192 Ir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 2 5、45、6 5和 82s ,轴向测定时间为 2 5s,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AAPMTGNo.6 0报告 ,采用MonteCarlo方法对放射源的辐射剂量进行理论计算 ,同时与采用AAPMTGNo.43报告计算方法进行比较。结果　国产血管内192 Ir线源具有良好的剂量分布。AAPMTGNo .43报告计算方法比MonteCarlo方法高估 32 %的辐射剂量。结论国产192 Ir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。     

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.     

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 distibution 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. Received 27 May and in revised form 7 September 1999     

Measurement of radiation absorbed dose in endovascular Ho-166 brachytherapy using a balloon angio-catheter

The purpose of this study was to estimate the absorbed dose distribution of Ho-166 endovascular beta irradiation using an angio-catheter. The liquid form of Ho-166 was produced at the Korea Atomic Energy Research Institute (KAERI) by an (n,gamma) reaction. Ho-166 has a half-life of 26.8 h and emits a high-energy beta particle with a maximum energy of 1.85 MeV. GafChromic film was used for the estimation of the absorbed dose of beta particles. A Co-60 teletherapy source and a 6 MV photon beam from a linear accelerator were used to generate dose-optical density calibration curves. The exposed films were read using a videodensitometer. With a modified micrometer, the film was positioned accurately on the surface of the balloon in water. The balloon was filled with Ho-166 solution to a pressure of 4 atm. Several film exposures were made with varying irradiation times and activities. The radiation absorbed dose rates were 1.02, 0.51 and 0.35 Gy x min(-1) x GBq(-1) x ml(-1) at the balloon surface, 0.5 and 1 mm from the balloon surface, respectively. The absorbed dose distribution revealed that Ho-166 is a good source for endovascular irradiation as the beta range is very short, avoiding unnecessary irradiation of normal tissue. A clinically applicable irradiation and duration of exposure were achievable utilizing our system.     

Monte Carlo dose simulation for intracoronary radiation therapy with a rhenium 188 solution-filled balloon with contrast medium

BACKGROUND: The therapeutic efficacy of percutaneous transluminal coronary angioplasty is limited by the incidence of restenosis. Intracoronary irradiation has shown to be effective in restenosis control by inhibiting the neointimal proliferation. METHODS AND RESULTS: Monte Carlo simulation has been performed to calculate the dose to the vessel wall for intracoronary irradiation with a rhenium 188 solution-filled balloon for restenosis inhibition. With a 3-mm-diameter and 30-mm-long balloon, the radiation dose at 1 mm from the balloon surface was 5.3% lower when the balloon structure was included in geometric modeling of the angioplasty catheter, as compared with that obtained by ignoring the structure. The additional dose reduction due to Hexabrix 320 contrast medium added in 30% of volume ratio was 4.7%. With regard to axial dose distribution, the dose was uniform over the balloon length except near the balloon end, at which the dose was reduced by 35% at a 1-mm-deep layer in the vessel wall. With the Re-188 solution mixed with 30% of Hexabrix 320 in volume ratio, the Re-188 activity to be injected for delivery of 15 Gy to the 1-mm-deep layer by 1-minute irradiation was 27.3 GBq/mL. CONCLUSIONS: Dose estimates produced in this study should be helpful in determining the Re-188 activity to be injected or the irradiation time for a varying situation in terms of length and diameter of the irradiated arterial segment and depth of the target layer.     

Quantification of horseradish peroxidase delivery into the arterial wall in vivo as a model of local drug treatment: Comparison between a porous and a gel-coated balloon catheter

Purpose: To quantify horseradish peroxidase (HRP) delivery into the arterial wall, as a model of local drug delivery, and to compare two different percutaneous delivery balloons. Methods: Perforated and hydrophilic hydrogel-coated balloon catheters were used to deliver HRP in aqueous solution into the wall of porcine iliac arteries in vivo. HRP solutions of 1 mg/ml were used together with both perforated and hydrophilic hydrogel-coated balloon catheters and 40 mg/ml HRP solutions were used with the hydrogel-coated balloon only. The amount of HRP deposited in the arterial wall was then determined photospectrometrically. Results: Using the 1 mg/ml HRP solution, the hydrogel-coated balloon absorbed 0.047 mg HRP into the coating. Treatment with this balloon resulted in a mean vessel wall concentration of 7.4 μg HRP/g tissue ± 93% (standard deviation) (n = 7). Treatment with the hydrogel-coated balloon that had absorbed 1.88 mg HRP into the coating (using the 40 mg/ml HRP solution) led to a mean vessel wall concentration of 69.5 μg HRP/g tissue ± 74% (n = 7). Treatment with the perforated balloon using 1 mg/ml aqueous HRP solution led to a mean vessel wall concentration of 174 μg/g ± 81% (n = 7). Differences between the hydrogel-coated and perforated balloons (1 mg/g solutions of HRP) and between hydrogel-coated balloons (0.047 mg vs 1.88 mg absorbed into the balloon coating) were significant (p < 0.05; two-sided Wilcoxon test). Conclusions: The use of a perforated balloon catheter allowed the delivery of a higher total amount of HRP compared with the hydrogel-coated balloon, but at the cost of a higher systemic HRP application. To deliver 174 μg HRP per gram of vessel wall with the perforated balloon, 6.5 ± 1.5 mg HRP were lost into the arterial blood (delivery efficiency range = 0.2%–0.3%). With 0.047 mg HRP loaded into the coating of the hydrogel balloon, 7.4 μg HRP could be applied to 1 g of vessel wall (delivery efficiency 1.7%), and with 1.88 mg HRP loaded into the coating of the hydrogel balloon, 69.5 μg HRP could be applied per gram of vessel wall (delivery efficiency 0.6%).     

32P液体球囊血管内照射预防血管成形术后再狭窄

目的 探讨^32P液体球囊血管内近距离照射治疗对防止血管成形术后再狭窄的量效关系及其抑制再狭窄发生的可能机制。方法 27只雌性大白兔据动脉球囊扩张损伤后，实验组(18只)分别给予3、9、18和36Gy^32P液体球囊行内照射治疗，对照组(9只)灌注生理盐水。术后于不同时间点取材，行HE染色、增殖细胞核抗原(PCNA)免疫组织化学染色以及电镜观察血管组织形态学的改变，用计算机图像分析法测量管腔面积和内膜面积。结果 对照组血管内膜明显增生，管腔变狭窄。18Gy组血管壁平滑肌细胞增殖明显受抑，细胞凋亡增加，管腔面积无明显丢失；36GY组血栓形成明显；3和9Gy组均未观察到明显的生物效应。结论 ^32P液体球囊血管内照射可防止血管成形术后再狭窄发生，其机制可能为抑制血管壁平滑肌细胞增殖，促进其凋亡及改善血管重塑形。     

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.     

Rectal wall sparing by dosimetric effect of rectal balloon used during intensity-modulated radiation therapy (IMRT) for prostate cancer.

The use of an air-filled rectal balloon has been shown to decrease prostate motion during prostate radiotherapy. However, the perturbation of radiation dose near the air-tissue interfaces has raised clinical concerns of underdosing the prostate gland. The aim of this study was to investigate the dosimetric effects of an air-filled rectal balloon on the rectal wall/mucosa and prostate gland. Clinical rectal toxicity and dose-volume histogram (DVH) were also assessed to evaluate for any correlation. A film phantom was constructed to simulate the 4-cm diameter air cavity created by a rectal balloon. Kodak XV2 films were utilized to measure and compare dose distribution with and without air cavity. To study the effect in a typical clinical situation, the phantom was computed tomography (CT) scanned on a Siemens DR CT scanner for intensity-modulated radiation therapy (IMRT) treatment planning. A target object was drawn on the phantom CT images to simulate the treatment of prostate cancer. Because patients were treated in prone position, the air cavity was situated superiorly to the target. The treatment used a serial tomotherapy technique with the Multivane Intensity Modulating Collimator (MIMiC) in arc treatment mode. Rectal toxicity was assessed in 116 patients treated with IMRT to a mean dose of 76 Gy over 35 fractions (2.17-Gy fraction size). They were treated in the prone position, immobilized using a Vac-Loktrade mark bag and carrier-box system. Rectal balloon inflated with 100 cc of air was used for prostate gland immobilization during daily treatment. Rectal toxicity was assessed using modifications of the Radiation Therapy Oncology Group (RTOG) and late effects Normal Tissue Task Force (LENT) scales systems. DVH of the rectum was also evaluated. From film dosimetry, there was a dose reduction at the distal air-tissue interface as much as 60% compared with the same geometry without the air cavity for 15-MV photon beam and 2x2-cm field size. The dose beyond the interface recovered quickly and the dose reductions due to air cavity were 50%, 28%, 11%, and 1% at 2, 5, 10, and 15 mm, respectively, from the distal air-tissue interface. Evaluating the dose profiles of the more clinically relevant situation revealed the dose at air-tissue interface was approximately 15% lower in comparison to that without an air cavity. The dose built up rapidly so that at 1 and 2 mm, there was only an 8% and 5% differential, respectively. The dosimetric coverage at the depth of the posterior prostate wall was essentially equal with or without the air cavity. The median follow-up was 31.3 months. Rectal toxicity profile was very favorable: 81% (94/116) patients had no rectal complaint while 10.3% (12/116), 6.9% (8/116), and 1.7% (2/116) had grade 1, 2, and 3 toxicity, respectively. There was no grade 4 rectal toxicity. DVH analysis revealed that none of the patients had more than 25% of the rectum receiving 70 Gy or greater. Rectal balloon has rendered anterior rectal wall sparing by its dosimetric effects. In addition, it has reduced rectal volume, especially posterior and lateral rectal wall receiving high-dose radiation by rectal wall distension. Both factors may have contributed to decreased rectal toxicity achieved by IMRT despite dose escalation and higher than conventional fraction size. The findings have clinical significance for future very high-dose escalation trials whereby radiation proctitis is a major limiting factor.