高剂量率~(192)Ir后装腔内加外照射治疗宫颈癌的远期疗效分析

目的　分析高剂量率192 Ir后装腔内加外照射治疗宫颈癌的远期疗效及并发症。方法　对12 8例Ⅱ、Ⅲ期放疗后宫颈癌进行了回顾分析。其中Ⅱ期 47例 ,Ⅲ期 81例。全盆腔外照射DT2 0Gy/ 10次 ,全盆中间挡铅 4cmDT2 0Gy～ 30Gy/ 10次～ 15次 ;后装A点剂量 48Gy～ 5 6Gy/ 6次～ 7次。 结果　 1、3、5年生存率分别为 91 6 1%、81 8%和 6 7 36 % ;Ⅱ、Ⅲ期 1、3、5年生存率无统计学差异 (P >0 .0 5 ) ;远期严重并发症的发生率 7 0 3% (9/ 12 8)。结论　高剂量率192 Ir后装腔内加外照射治疗宫颈癌疗效肯定 ,并发症少。盆腔局部复发仍是放疗失败的主要原因。     

高剂量率192铱后装机腔内加外照射治疗宫颈癌60例临床分析

目的:探讨高剂量率192铱后装腔内加体外照射治疗宫颈癌的疗效及副作用等。方法:2005年3月至2007年1月本院放疗中心共60例宫颈癌患者,采用8MV-X线直线加速器全盆照射,开始体外全盆腔照射,5次/周,2Gy/次,剂量25-40Gy;然后中间挡铅,4个野照射,5次/周,2Gy/次,宫旁剂量20-25Gy:同时腔内治疗,1次/周,6Gy/次,剂量为35-40Gy。腔内治疗采用ZL-HDR18铱高剂量率后装治疗机,全部病例均宫颈阴道同时进行。腔内治疗每周1次,A点剂量36-40GY/6-7F/6-7w,腔内治疗当日停体外照射,治疗时间56-77天。结果:CR+PR 100%,随访超过3年,随访率达95%,3年生存率Ⅱ期88.3%,Ⅲ期82.9%;早期放射性直肠反应发生率为12.4%,膀胱反应发生率5.2%;晚期放射性直肠炎发生率13.8%,膀胱炎3.8%。结论:高剂量率192铱后装机腔内加体外治疗宫颈癌的疗效满意,患者生存率较高,耐受好,并发症少。     

High beta and electron dose from 192Ir: implications for "gamma" intravascular brachytherapy

PURPOSE: Trains of multiple 192Ir seeds are used in many clinical trials for intravascular brachytherapy. 192Ir source is commonly considered as a gamma emitter, despite the understanding that this radionuclide also emits a wide range of electron and beta energies, with a similar range of energy. The high dose from betas and electrons in the submillimeter range due to unsealed ends of seed sources should be precisely quantified to fully understand the backdrop for complications associated with 192Ir coronary artery brachytherapy. METHODS AND MATERIALS: Monte Carlo simulations (MCNP4C code) were performed for a model 5-seed 192Ir train used in SCRIPPS, GAMMA, and the Washington Radiation for In-Stent Restenosis (WRIST) randomized clinical trials. A stack of radiochromic films was also used to measure the dose distributions for an actual 6-seed train. RESULTS: In the submillimeter range very close to the source, Monte Carlo results show that betas and electrons deposit a higher dose than 192Ir photons (gamma and X-rays) over the interseed gap. A high luminal dose from the combined effects of betas, electrons, and photons emitted from 192Ir can be deposited, particularly between seeds. When prescribing 15 Gy at 2 mm, the combined dose can be as high as 160 Gy at 0.5 mm. Different peak doses near the interseed gaps were noted, which may be due to variability of seed-end surfaces and nonuniformity of seed activity within a real multiseed train. Dose-volume histograms (DVH) of lumen surfaces were evaluated for an eccentric seed train. The DVH parameters indicating the extent of hot spots in the lumen wall, DV(10), DV(5), DV(2), and DV(1) (dose received by 10, 5, 2, 1% respectively of the total lumen surface), can be as high as 55, 76, 81, and 155 Gy for a lumen with 3-mm diameter, and 75, 80, 110, and 158 Gy for a narrow 2-mm lumen. CONCLUSION: 192Ir multiple seed trains used in the SCRIPPS, GAMMA, and WRIST trials can deposit a very high dose to the luminal wall. A particularly high electron and beta dose can be delivered near the interseed gap if the source is not centered in the catheter and lumen. The dose from 192Ir betas and electrons may partially explain adverse outcomes reported from 192Ir multiseed clinical trials. Improvement of the encapsulation design to filter out the betas and electrons should be seriously considered.     

192Ir近距离照射的剂量率效应研究

目的对１９２Ｉｒ高剂量率近距离治疗机在近距离放射治疗中的剂量率效应进行了实验室观察和探讨。方法分别在不同剂量率条件下（平均剂量率为４６．２９Ｇｙ／ｈ或５．７９Ｇｙ／ｈ）进行全腹或全胸１９２Ｉｒ近距离照射。观察指标为存活隐窝细胞数（小肠）和ＬＤ５０值（肺）。结果随平均剂量率的降低和照射时间的延长,早反应组织小肠和晚反应组织肺癌生物效应也会随之下降。不同剂量率照射后小肠的ＥＤ１０剂量之差为２．４６Ｇｙ［（１５．４１－１２．９５）Ｇｙ］,等效剂量降低了１６．０％;肺的ＬＤ５０剂量之差为４．２５Ｇｙ［（１３．２５－９．００）Ｇｙ］,等效剂量降低了３２．１％。结论在进行近距离放射治疗过程中,随剂量率的不同存在着对晚反应组织可能过量或肿瘤剂量不足的潜在生物学问题,该点应予注意。     

高剂量率^192铱后装机腔内加外照射治疗宫颈癌60例临床分析

目的：探讨高剂量率^192铱后装腔内加体外照射治疗宫颈癌的疗效及副作用等。方法：2005年3月至2007年1月本院放疗中心共60例宫颈癌患者,采用8MV-X线直线加速器全盆照射,开始体外全盆腔照射,5次/周,2Gy/次,剂量25-40Gy;然后中间挡铅,4个野照射,5次/周,2Gy/次,宫旁剂量20-25Gy：同时腔内治疗,1次/周,6Gy/次,剂量为35-40Gy。腔内治疗采用ZL-HDR18铱高剂量率后装治疗机,全部病例均宫颈阴道同时进行。腔内治疗每周1次,A点剂量36-40GY/6-7F/6-7w,腔内治疗当日停体外照射,治疗时间56-77天。结果：CR＋PR 100%,随访超过3年,随访率达95%,3年生存率Ⅱ期88.3%,Ⅲ期82.9%;早期放射性直肠反应发生率为12.4%,膀胱反应发生率5.2%;晚期放射性直肠炎发生率13.8%,膀胱炎3.8%。结论：高剂量率^192铱后装机腔内加体外治疗宫颈癌的疗效满意,患者生存率较高,耐受好,并发症少。     

兔髂动脉血管内照射的实验方法

目的用改进型后装治疗机进行血管内放疗的可行性研究。资料与方法用兔髂动脉行血管成形术,制成血管狭窄模型,用改进型后装治疗机及微型放射源１９２Ｉｒ进行兔髂动脉内放疗,预防血管成形术后再狭窄。结果６０只兔分为３组。１）放疗１０Ｇｙ组;２）放疗１８Ｇｙ组;３）对照组,只做球囊扩张血管损伤,不做放疗。放疗组及对照组均１００％成功。结论改进型后装治疗机在兔髂动脉扩张术后照射,安全可行。     

Dosimetric calculations and VIPAR polymer gel dosimetry close to the microSelectron HDR

In the present study, different dosimetric methods were investigated for their ability to predict the energy dose in the vicinity of the microSelectron HDR 192Ir brachytherapy source. The results of a time-efficient Sievert integral model of proven accuracy in the cm distance range from all 192Ir sources were benchmarked against accurate Monte Carlo derived dosimetric data in the close vicinity of the source. This comparison revealed that the Sievert model is capable of accurate dosimetry even in the mm distance range from the source. The dose rate distributions were compared with results obtained from different versions (v. 13.7 and 14.2.2) of the Plato BPS commercial treatment planning system, for an application following the Paris trial intravascular irradiation protocol. The results of brachytherapy planning system calculations were found reliable at radial distances of clinical relevance. Noticeable errors existed only in the extreme case of dose calculations at 2 mm from the source axis using Plato v. 13.7. Experimental dosimetric data for the intravascular application, as obtained through the VIPAR polymer gel-MRI method, were also evaluated for dose verification purposes. This method allowed with reasonable accuracy the verification of absolute dose distributions for peripheral vessel applications using 192Ir sources.     

Monte Carlo calculation of the TG-43 dosimetric parameters of a new BEBIG Ir-192 HDR source.

BACKGROUND AND PURPOSE: High dose rate (HDR) brachytherapy is a highly extended practice in clinical brachytherapy today. Quality dose rate distribution datasets of the HDR sources used in a clinical treatment are required. Because of the different source designs, a specific dosimetry dataset is required for each source model. In the recently published BRAPHYQS-ESTRO Report, an overview of available dosimetric data for all HDR Ir-192 sources is given, pointing out the lack of data for one of the sources that is used by the BEBIG MultiSource afterloading system (BEBIG GmbH, Germany). The purpose of this study is to obtain detailed dose rate distributions in liquid water media around this source. MATERIAL AND METHODS: The Monte Carlo code GEANT4 was used to estimate dose rate in water and air-kerma strength around the Ir-192 source. All the details of the stainless steel encapsulated BEBIG HDR 1.1mm in external diameter has been included in the simulation. RESULTS: A complete dosimetric dataset for the BEBIG Ir-192 HDR source is presented. TG43 dosimetric functions and parameters have been obtained as well as a 2D rectangular dose rate table, consistent with the TG43 dose calculation formalism. The dosimetric parameters and functions obtained for the BEBIG HDR source have been compared with that obtained in the literature for others HDR sources, showing that the use of specific datasets for this new source is justified. CONCLUSIONS: This dataset can be used as input in the TPS and to validate its calculations. As policy of BRAPHYQS-ESTRO task group, this dataset will be incorporated to the website: available to users in excel format.     

高剂置率近距离放射治疗鼻咽癌的近期临床观察

本文报告48例采用外照射加腔内后装治疗鼻咽癌患者.其中计划性内、外照射29例,外照射未控补加腔内治疗9例,外照射放疗后鼻咽局部复发10例、腔内治疗使用~192Lr放射源,外照射总量5000~8500cGy.腔内治疗每次参考点剂量500~l000cG,总量1500~2500cGy.总鼻咽局部控制率91.7%.高于单纯外照射.为顽固性鼻咽癌的治疗提供了新方法.     

High-dose-rate brachytherapy using molds for oral cavity cancer: The technique and its limitations

Background. With the availability of a high-dose-rate (HDR) remote afterloading device, a Phase I/11 protocol was initiated at our institution to assess the toxicity and efficacy of HDR intracavitary brachytherapy, using molds, in the treatment of squamous cell carcinomas of the oral cavity. Methods. Eight patients with squamous cell carcinoma of the oral cavity were treated by the technique. The primary sites of the tumors were the buccal mucosa, oral floor, and gingiva. Two of the buccal mucosal cancers were located in the retromolar trigon. For each patient, a customized mould was fabricated, in which two to four afterloading catheters were placed for an ¹⁹²Ir HDR source. Four to seven fractions of 3–4 Gy, 5 mm below the mould surface, were given following external radiation therapy of 40–60 Gy/2 Gy. The total dose of HDR brachytherapy ranged from 16 to 28 Gy. Results. Although a good initial complete response rate of 7/8 (88%) was achieved, there was local recurrence in four of these seven patients. Both of the retromolar trigon tumors showed marginal recurrence. No serious (e.g., ulcer or bone exposure) late radiation damage has been observed thus far in the follow up period of 15–57 months. Conclusions. High-dose-rate brachytherapy using the mold technique seems a safe and useful method for selected early and superficial oral cavity cancer. However, it is not indicated for thick tumors and/or tumors located in the retromolar trigon.     

A new re-entrant ionization chamber for the calibration of iridium-192 high dose rate sources.

A re-entrant (well-type) ionization chamber has been designed and fabricated at the University of Wisconsin for use with iridium-192 high dose-rate (HDR) remote after-loading brachytherapy devices. The chamber was designed to provide an ionization current of about 10(-8) ampere with a nominal 10 curie iridium-192 source. A narrow opening is provided into the sensitive volume of the chamber to insert a Nucletron MicroSelectron catheter, or catheters with similar diameters from other HDR manufacturers. The chamber exhibits a flat response (+/- 0.1%) for any source position within +/-4 mm of the chamber center. A 300 volt chamber bias yields a 99.96% ion collection efficiency. The chamber is capable of being calibrated directly with an iridium-192 source which has in turn been calibrated with thimble-type ion chambers. Reproducibility for readings in the current mode for 10 consecutive insertions of the MicroSelectron iridium-192 HDR source is within 0.02% or less. Two thimble chambers calibrated by the U.S. National Institute of Standards and Technology provide calibration traceability of iridium-192 HDR sources and re-entrant chambers to a primary national standards laboratory. Results of activity measurements of 6 commercial iridium-192 HDR sources are reported.     

192Ir or 125I prostate brachytherapy as a boost to external beam radiotherapy in locally advanced prostatic cancer: a dosimetric point of view.

PURPOSE: This work aims at comparing the dosimetric possibilities of 125I or 192Ir prostate brachytherapy (Bt) as a boost to external beam radiotherapy in the treatment of locally advanced adenocarcinoma. METHODS AND MATERIALS: From 1/1997 to 12/2002, 260 patients were treated. Until 12/2001 a low dose rate (LDR) treatment with 192Ir wires was used, later replaced by a high dose rate (HDR) delivered with an 192Ir stepping source technology. For the present work, we selected 40 patients including the last 20 treated, respectively, by LDR and HDR. The planning CT Scans of all these 40 patients were transferred into the 3D Prowess system for 125I permanent implants design according to the Seattle method. The reference data for dosimetric comparisons were the V100 and the prescribed dose for 192Ir as well as the dose delivered with 125I techniques to the 192Ir V100. We compared V100-150 data as well as doses to the organs at risks (OR) and cold spots (CS). RESULTS: The V100 is 85.3+/-8% for 192Ir LDR and 96+/-2% for HDR techniques (P < 0.0001). In comparison with 125I, the 192Ir LDR mode induces higher hyperdosage volumes inside the CTV but also more CS, while maximal doses to urethra and rectum are, respectively, 17 and 39% less with 125I (P < 0.0001). In comparison with the 192Ir HDR mode, 125I Bt induces higher hyperdosage volumes and slightly more CS deliberately planned around the bladder neck. If delivered doses to urethra are identical, those to the 20% anterior part of the rectum are 33% less with 125I (P < 0,0001). The 125I Bt technique was only possible in 24 out of the 40 patients studied due to pelvic bone arch interference. CONCLUSIONS: At the present time, there is no evident dosimetric superiority of one Bt method when all the criteria are taken into account. However, improving Bt techniques to implant any prostatic size could found the superiority of the 125I or permanent implants. 125I indeed allows large hyperdosage volumes inside the CTV in comparison with 192Ir HDR techniques while lowering doses to OR and minimizing CS.     

Dosimetric characterizations of GZP6 60Co high dose rate brachytherapy sources: application of superimposition method

Background

Dosimetric characteristics of a high dose rate (HDR) GZP6 Co-60 brachytherapy source have been evaluated following American Association of Physicists in MedicineTask Group 43U1 (AAPM TG-43U1) recommendations for their clinical applications.

Materials and methods

MCNP-4C and MCNPX Monte Carlo codes were utilized to calculate dose rate constant, two dimensional (2D) dose distribution, radial dose function and 2D anisotropy function of the source. These parameters of this source are compared with the available data for Ralstron ⁶⁰Co and microSelectron¹⁹²Ir sources. Besides, a superimposition method was developed to extend the obtained results for the GZP6 source No. 3 to other GZP6 sources.

Results

The simulated value for dose rate constant for GZP6 source was 1.104±0.03 cGyh-1U-1. The graphical and tabulated radial dose function and 2D anisotropy function of this source are presented here. The results of these investigations show that the dosimetric parameters of GZP6 source are comparable to those for the Ralstron source. While dose rate constant for the two ⁶⁰Co sources are similar to that for the microSelectron¹⁹²Ir source, there are differences between radial dose function and anisotropy functions. Radial dose function of the ¹⁹²Ir source is less steep than both ⁶⁰Co source models. In addition, the ⁶⁰Co sources are showing more isotropic dose distribution than the ¹⁹²Ir source.

Conclusions

The superimposition method is applicable to produce dose distributions for other source arrangements from the dose distribution of a single source. The calculated dosimetric quantities of this new source can be introduced as input data to the GZP6 treatment planning system (TPS) and to validate the performance of the TPS.     

Endobronchial radiation therapy (EBRT) in the management of lung cancer.

Between October 1987 and November 1988, 19 endobronchial Iridium-192 line source placements were attempted in 17 patients with advanced incurable lung cancer. Approximately 30 Gy was delivered to the endobronchus using a low dose rate (LDR) afterloading technique delivering a mean dose of 70 cGy/hr at 5 mm. Improvement in subjective symptoms was noted in 67% of evaluable patients whereas objective responses defined by chest X ray and bronchoscopy were noted in 26% and 60%, respectively. No significant morbidity was observed. The radiation exposure to health care workers was low ranging from 10 to 40 mRem per treatment course with most of the staff receiving less than 10 mRem per treatment course (minimal detectable level 10 mRem). The results of this series are compared with selected series using low dose rate as well as intermediate dose rate (IDR) and high dose rate (HDR) endobronchial radiation therapy (EBRT). Based on bronchoscopic responses from the selected series reviewed, both HDR low total dose per treatment (range 7.5-10 Gy) and LDR high total dose per treatment (range 30-50 Gy) are effective in palliating the vast majority of patients with endobronchial lesions. Intermediate dose rate is also effective using fractions similar to high dose rate but total dose similar to low dose rate. The efficacy of endobronchial radiation therapy in the palliative setting suggest a possible role for endobronchial radiation therapy combined with external beam irradiation with or without chemotherapy in the initial management of localized lung cancer. Defining the optimal total dose, dose rate, and the exact role of endobronchial radiation therapy in the management of lung cancer will require large cooperative trials with standardization of techniques and definitions.     

Recommendations for implementation of high dose rate 192Ir brachytherapy in developing countries by the Advisory Group of International Atomic Energy Agency.

PURPOSE: To provide recommendations for the implementation of high dose rate (HDR) 192Ir brachytherapy technology in developing countries.METHODS: An Advisory Group Meeting of the International Atomic Energy Agency (IAEA) met to address the implementation of HDR 192Ir brachytherapy technology in developing countries. These recommendations reflect only the personal opinions of the authors and do not necessarily represent the opinion of the IAEA.RESULTS: An HDR treatment system should be purchased as a complete unit that includes the 192Ir radioactive source, source loading unit, applicators, treatment planning system, and control console. Infrastructure support may require additional or improved buildings and procurement of or access to new imaging facilities. A supportive budget is needed for quarterly source replacement and the annual maintenance necessary to keep the system operational. The radiation oncologist, medical physicist, and technologist should be specially trained before HDR can be introduced. Training for the oncologist and medical physicist is an ongoing process as new techniques or sites of treatment are introduced. Procedures for quality assurance (QA) of patient treatment, and the planning system must be introduced. Emergency procedures with adequate training of all associated personnel must be in place.CONCLUSIONS: The decision to select HDR in preference to alternate methods of brachytherapy is influenced by the ability of the machine to treat a wide variety of clinical sites. In departments with personnel and budgetary resources to support this equipment appropriately, economic advantage becomes evident only if large numbers of patients are treated. Intangible benefits of source safety, personnel safety, and easy adaptation to fluctuating demand for treatments also require consideration when evaluating the need to introduce this treatment system.     

First clinical experience with a remote afterloading system for low dose rate interstitial breast implants

A new remote afterloading system, developed for low or medium dose rate brachytherapy has been clinically evaluated. With this apparatus, the Micro-Selectron, up to 15 ¹⁹²Ir wires or seeds encapsulated in a plastic tubing can be loaded simultaneously into implants. Improved radiological protection for the medical staff has now been achieved with this apparatus. One hundred and sixty patients have been treated so far with breast implants using remote afterloading. The mean error frequency over the last year was about one error every 10 treatments of which about half could be considered as machine failures. All treatments could, however, be finished by using spare channels of the afterloader. We have found that a set of 45 source assemblies is adequate for the loading of the breast-needle implants performed in our institute. Every 6 to 8 weeks a new set of ¹⁹²Ir sources is prepared.     

Does inverse planning applied to Iridium192 high dose rate prostate brachytherapy improve the optimization of the dose afforded by the Paris system?

BACKGROUND AND PURPOSE: The purpose of the work is to analyse for 192Ir prostate brachytherapy (BT) some of the different steps in optimizing the dose delivered to the CTV, urethra and rectum. MATERIALS AND METHODS: Between 07/1998 and 12/2001, 166 patients were treated with 192Ir wires providing a low dose rate, according to the Paris system philosophy and with the 2D version of the treatment planning IsisR. 40-45 Gy were delivered after an external beam radiotherapy of 40 Gy. The maximum tolerable doses for BT were 25 Gy to the anterior third of the rectum on the whole length of the implant (R dose) and 52 Gy to the urethra on a 1cm length (Umax). A Umax/CTV dose ratio >1.3 represented a pejorative value as the planned dose of 40-45 Gy could not be achieved. On the other side a ratio 1.25 decreased significantly with optimization required on CTV contours and additional constraints on urethra while the R/CTV ratio was maintained under 0.55. For initial Umax/CTV >1.3 or >1.25 but 相似文献   

Role of interstitial brachytherapy in the treatment of malignant disease.

Interstitial brachytherapy was first applied using radium needles, with minimum protection of physicians and nurses. Modern techniques involve the use of radionuclide (192)Ir as the source used in computer-controlled remote afterloading machines, which can deliver a high dose rate (HDR). Treatment planning is also undertaken with the use of computers and anatomical cross-section images using CT, ultrasound and MRI. This review presents these modern techniques for tumors of a series of body sites: prostate, head and neck, breast, bladder, brain, and for soft-tissue sarcomas. Low dose rate (LDR) interstitial brachytherapy techniques are also included in this review since in some body sites there is a choice between HDR and LDR.     

Percutaneous and endobronchial high dose rate brachytherapy for lung cancer

Endobronchial and percutaneous high dose rate (HDR) brachytherapy was performed with a microSelectron HDR using iridium-192 as a radiation source. As spontaneous pain was uncontrollable by external beam radiation (EBR), chemotherapy, hyperthermia or a combination of these treatment methods, three patients with lung cancer infiltration into the chest wall underwent percutaneous HDR brachytherapy for palliation of severe pain. Selectron needles were inserted under CT guidance and the irradiation dose was set to 10 or 12 Gy at the point 1 cm from the center of the radiation source. A total of 2-4 selectron needles was introduced by means of a template. Irradiation was performed once a week for 1-2 weeks depending on the degree of alleviation of spontaneous pain. In all 3 cases, alleviation of spontaneous pain occured within 7 days after the completion of HDR brachytherapy, and the mean pain score decreased from a value of 2 to 1 within 2 weeks. After discharge from the hospital, the pain score remained between 1-4 in all 3 patients. One problem in percutaneous brachytherapy is the possible hindrance of multiple selectron needle insertion through the template by the ribs depending on the location of the lesion. Six patients aged 51-75 years were subjected to endobronchial HDR brachytherapy. Two of these patients had postoperative recurrence of lung cancer, and 3 patients received concomitant chemotherapy. Brachytherapy was performed 3.4 months (average) after the administartion of 40-70 Gy of EBR. Endobronchial irradiation was performed at a dose of 7 Gy, measured at 1 cm from the center of the radiation source, once a week over a 3 week period for a total of 21 Gy. With the exception of 2 patients who died due to systemic exacerbation, local control of the illness has been good. In endobronchial HDR brachytherapy, it is important to develop a system for altering radiation dose in response to changes in the caliber of the tracheobronchial tree and the degree of the tumor invasion under the bronchial mucosa.