HG-HDR18型^192Ir近距离后装机的维护、保养和故障排除

现代近距离后装治疗机由于其放射源铱(^192Ir)微型化，采用程控步进电机驱动，照射时间短，近放射源处局部剂量高，照射范围内剂量不均一，微机遥控等特点，近距离治疗已从传统的妇癌领域扩展到全身各部位多种癌瘤，如：鼻咽癌、鼻腔癌、食道癌、支气管肺癌、脑瘤、口腔癌、直肠癌、胰腺胆管、膀胱、宫颈癌、舌癌、喉癌、肝癌、乳腺癌、前列腺等等，治疗技术涉及腔管、组织间、术中和敷贴等多种施治方法，使大量手术拒治、外照射未控或复发的患者获得了再程治疗的机会，并有非常肯定的疗效。逐步形成远距离外照射治疗(加速器产生的X射线、^60Co产生的γ射线、深部及浅部X射线)与近距离后装治疗相配合的综合治疗方法，成为放射治疗发展的新趋势。     

WD—HDR18近距离遥控后装机检修方法2例

WD—HDR18是高剂量率、组织内、腔体内照射治疗遥控后装机，采用微型单粒高活度铱192放射源，利用内装模拟源装置和完整的计算机程序控制，操作简单。但由于真源（铱192）具有辐射，造成了有些故障无法到机房内实际观察和测量，给维修带来不便。这里简单介绍一下后装机两种故障的检修方法。     

共用机房后装机屏蔽罩的设计

我院BJ-6B型医用电子直线加速器与HY-HDR18型高剂量率近距离后装治疗机共用一个机房，因加速器与后装机分时使用，加速器的能量(6MeV)远高于后装机(铱-192)的能量(7平均能量为380KeV)，所以按标准加速器机房屏蔽要求设计。加速器与后装机共用和非共用机房的最主要区别是：接受加速器放疗的患者(含头部、体部X刀治疗患者)和放疗技术人员与后装放射源(平时不治疗病人时^192Ir在后装机的储源罐中)接触的时间大大增加。笔者设计、制成后装机屏蔽罩，增加了10mm铅防护，加大了防护的安全系数。现将制作过程介绍如下：     

后装机192Ir放射源到位精度及剂量重复性测量

后装机治疗 (brachytherapy)是将封装好的放射源 ,通过施源器或输源导管 ,用计算机将放射源植入患者的肿瘤部位进行照射治疗的 1种方法。由于放射源贴近肿瘤组织 ,源的到位精度及到位重复性直接影响肿瘤的辐射剂量分布。后装机1 92 Ir源的到位精度及重复性也是常规质量控制 (QC)和质量保证 (QA)的检查项目。目前已有商品化的QC检测工具[1 ] ,可以方便地完成HDR重要参数检测。当前国内许多放疗单位均未配备QC检测工具 ,本文作者介绍了采用普通直尺及剂量仪等一般工具测量1 92 Ir放射源的到位精度及重复性的方法 ,对临床后装治疗的质量…     

近距离治疗的临床放射生物学

近距离治疗是将放射性同位素植入或置于肿瘤周边的一种技术。中心高剂量及随着距离的增加剂量迅速衰减是其最大的特点。近距离治疗主要包括低剂量率、高剂量率和脉冲剂量率3种。近距离治疗的最大优势是保证肿瘤组织充足剂量的基础上降低周围正常组织的放射性损伤。临床近距离治疗技术的进步与其放射生物学特点联系紧密。临床近距离治疗放射生物学的基本概念主要包括剂量率效应、放射性损伤的修复、再氧合、细胞周期的再分布及再群体化。探索近距离治疗放射生物学与临床近距离治疗效果的关系,利用近距离治疗的放射生物学特点,指导临床上近距离治疗的具体应用需要大量转化医学的工作。最终的目的是增加肿瘤局部控制率、降低不良反应及提高患者最终的生存期。     

不同施源器对后装机192Ir放射源剂量分布的影响

后装机治疗 (brachytherapy)作为恶性肿瘤放射治疗中外照射的补充在国内的使用越来越普遍 ,每年约需要 6 0 0多颗放射源[1 ] ,它是将封装放射源通过施源器或输源导管 ,用计算机将放射源植入患者的肿瘤部位进行照射治疗的一种方法。施源器有两种类型 :金属硬质施源管和塑料施源软管。不同材料的施源器对1 92 Irγ射线的剂量吸收不同 ,必定造成放射源周围剂量分布的差异 ,了解这种剂量差异的程度对后装治疗的质量控制 (QC) ,后装治疗计划系统软件设计以及提高治疗的精确性具有一定的现实意义。一、材料和方法1 材料和仪器 :天津荣力公司生产…     

通过分析后装机控制文件解决后装计划部分执行问题

目的 通过分析和编辑后装机控制文件来解决后装计划部分执行问题。方法 通过记录治疗当时的放射源源强、患者已经受照时间、应用C语言程序追踪到患者部分治疗时紧急回源前最后驻留点位置以及放射源在最后驻留点位置已经驻留的时间,通过编辑后装机控制文件生成后续治疗文件,并应用固体水建立测量模型验证生成后续治疗文件的正确性。结果 对于测量模型中定义的A、B点剂量,Dose A4（后装计划中断前后A点受照剂量之和）与Dose A1（完整执行后装计划A点受照剂量）相差6.12%,Dose B4（后装计划中断前后B点受照剂量之和）与Dose B1（完整执行后装计划B点受照剂量）相差2.09%;MapCheck平面剂量Plane Dose 4（后装计划中断前后MapCheck平面剂量之和）与Plane Dose 1（完整执行后装计划MapCheck平面剂量）都呈现正梨形剂量分布,百分剂量差异4%以内的达到了93.8%,满足临床剂量要求。结论 后续治疗文件可以准确完成患者后装计划中未完成的部分,达到剂量分布要求。     

鼻咽癌根治性放射治疗的临床分析

目的：通过回顾性分析,了解鼻咽癌外照射及外放疗俣并近距离治疗的临床疗效。方法：自1992年1月－1997年1月,我科对首程收治的83例鼻咽癌患者,先采用常规外照射治疗,这根治剂量60－70Gy后,45例鼻咽腔内基本无病灶残存,结束放疗;对鼻咽腔内有残存病灶者38例采用后装近距离放射治疗方法补充照射剂量,近距离治疗总剂量一般为距施源器中轴8－12mm处12－20Gy／2－5次／周,每次4－6Gy。随诊为3年以上,随访率95．2％,失访4例,按死亡计算。结果：外照射治疗后病灶残存合并近距离组和单纯外放疗组的5年局部控制率分别为61．1％和56．5％,5年生存率分别为66．7％和59．1％。随访期内未见严重放射性并发发症。结论：（1）外照射治疗后,对鼻咽腔内有灶残存者合并近距离治疗,可提高鼻咽癌的局部控制率。（2）外放疗和近距离放射治疗的合理配合,不会增加严重放射并发症的发生率。     

施源器内径对后装治疗剂量分布的影响

近距离放射治疗在恶性肿瘤的治疗中具有重要地位,施源器是近距离放射治疗必须借助的工具之一,临床上用的施源器规格多样,内径大小不一.施源器内径大小是否会造成患者实际接受剂量与治疗计划中设定参考剂量的不符,对此鲜有报道.笔者通过实验对此进行验证,现报道如下.     

Development and comprehensive commissioning of an automated brachytherapy plan checker

PurposeTo present on the commissioning of an automated brachytherapy plan checker (BPC) for the evaluation of high-dose-rate brachytherapy treatment plans in support of standardized workflows and patient safety.Methods and MaterialsA BPC was developed using an applications programming interface in a commercial treatment planning system based on different inputs (e.g., regulations, professional society recommendations, and user feedback) and leveraged our experience with an in-house developed external beam plan checker. The BPC was commissioned using a comprehensive suite of test plans with known errors and anonymized clinical plans.ResultsDuring commissioning, the BPC was successfully executed on a total of 87 test plans. Commissioning tests spanned a range of treatment sites and evaluated that pass and fail states were correct. Administration settings were changed in a nonclinical database to evaluate tests involving the source and afterloader. Clinical testing of the BPC was then performed in parallel with a manual review process before clinical implementation.ConclusionsTo commission the BPC for clinical use, a comprehensive suite of test plans was developed and used to ensure the BPC correctly detected and reported errors. A summary of the test plans is presented to help guide users developing similar automated tools. The BPC represents a process-improvement initiative designed to reduce errors and improve safety for brachytherapy patients. By using a comprehensive test suite for commissioning, tests are available for periodic quality assurance and after software upgrades.     

Physical characteristics of the Selectron high dose rate intracavitary afterloader

The physics measurements on a Selectron high dose-rate afterloading cobalt-60 unit are reported. The installation was found to be acceptable from the standpoint of radiation safety and cost effectiveness; hospital bed space was saved as treatment could be on an outpatient basis. A source calibration 4% higher than the value stated by the manufacturer was obtained. Measurement of the ratio of exposure rate in water to that in air confirmed the calibration and the applicability of correction factors for routine clinical dosimetry recommended in the literature.     

Clinical commissioning of Laitinen Stereoadapter for fractionated stereotactic radiotherapy

The Laitinen Stereoadapter 5000 from Sandstroem Trade and Technology was acceptance tested and commissioned for clinical use in a Fractionated Stereotactic Radiotherapy Program at our facility. The frame was implemented to function as a localization device for target delineation rather than as an immobilization device. The frame is of non-invasive nature utilizing ear plugs and a nasion bridge adapter as the connecting points with the patient’s head. The reproducibility of the head frame position with respect to external skull reference points was tested. CT and MRI imaging studies were performed on a patient phantom with the stereoadapter in place. The target was delineated and target coordinates were calculated for two implanted targets. The phantom was positioned according to the target coordinates on a Siemens MXE Linear Accelerator by aid of the target positioning lasers. Radiographic port film images were taken with the circular fields typically used in stereotactic radiosurgery. A complete treatment isodose plan was performed and dosimetric accuracy was tested by positioning a small volume ionization chamber at the center of the target volume in the head phantom. The results of these tests were found to be clinically acceptable.     

Clinical commissioning of Laitinen Stereoadapter for fractionated stereotactic radiotherapy

The Laitinen Stereoadapter 5000 from Sandstroem Trade and Technology was acceptance tested and commissioned for clinical use in a Fractionated Stereotactic Radiotherapy Program at our facility. The frame was implemented to function as a localization device for target delineation rather than as an immobilization device. The frame is of non-invasive nature utilizing ear plugs and a nasion bridge adapter as the connecting points with the patient’s head. The reproducibility of the head frame position with respect to external skull reference points was tested. CT and MRI imaging studies were performed on a patient phantom with the stereoadapter in place. The target was delineated and target coordinates were calculated for two implanted targets. The phantom was positioned according to the target coordinates on a Siemens MXE Linear Accelerator by aid of the target positioning lasers. Radiographic port film images were taken with the circular fields typically used in stereotactic radiosurgery. A complete treatment isodose plan was performed and dosimetric accuracy was tested by positioning a small volume ionization chamber at the center of the target volume in the head phantom. The results of these tests were found to be clinically acceptable.     

术中125I粒子植入治疗复发性脑胶质瘤的临床研究

目的探讨复发性脑胶质瘤术中mI粒子植入治疗的近期治疗效果及并发症。方法回顾性分析58例复发性脑胶质瘤患者资料,其中,23例患者行单纯手术,另外35例利用计算机三维治疗计划系统于术前或术中制定治疗计划,术中依据所制定的剂量,在肿瘤切除后的瘤床上植入mI粒子,处方剂量为140～188Gy。术后每2个月复查CT或MRI进行验证和质量评估,随访8～32个月,比较分析两组患者的肿瘤复发率、生存期及放射性并发症。结果单纯手术组中有20例复发,复发率为87．0％;有3例死于术后并发症。术中mI粒子植入治疗组中有23例复发,复发率为65．7％;有5例死于术后并发症,4例发生顽固性脑水肿,3例发生放射性脑坏死。术中“I粒子植入治疗组肿瘤复发时间f（97．5±15．3）周】明显长于单纯手术组【（62．5±13．6）周]（t=9．21,P〈0．05）,生存期[（60．3±7．1）周】亦明显长于单纯手术组[（43．1±5．5）周1（t=13．03,P〈0．05）。单因素变量分析结果显示,世界卫生组织肿瘤病理分级与肿瘤切除程度是影响患者生存率的独立因素。结论术中125I粒子植入治疗可降低脑胶质瘤的复发率,有效增加复发性脑胶质瘤患者的生存时间。     

Rectal and oesophageal treatment by the Selectron High Dose Rate afterloader

Rectal and oesophageal intracavitary treatments have been administered by the Selectron High Dose Rate afterloader. The treatment time is of the order of a few minutes which makes the use of a high dose rate advantageous as compared to medium and low dose rate procedures. Localizing techniques as well as dosimetry are discussed.     

Clinical commissioning of online seed matching protocol for prostate radiotherapy

Objectives

Our aim was to clinically commission an online seed matching image-guided radiotherapy (IGRT) protocol using modern hardware/software for patients undergoing prostate radiotherapy. An essential constraint was to achieve this within a busy centre without reducing patient throughput, which had been reported with other techniques.

Methods

45 patients had 3 fiducial markers inserted into the prostate and were imaged daily using kilovoltage orthogonal images with online correction applied before treatment. A total of 1612 image pairs were acquired and analysed to identify interfractional motion, seed migration and interobserver variability, and assess ease of use.

Results

This method of IGRT was implemented successfully in our centre with no impact on treatment times and patient throughput. Systematic (Σ) interfractional set-up errors were 2.2, 2.7 and 3.9 mm in right–left (RL), superoinferior (SI) and anteroposterior (AP) directions, respectively. Random (σ) interfractional set-up errors were 3.2 (RL), 3.7 (SI) and 5.7 mm (AP). There were significant differences between patients. Seed migration and interobserver variability were not significant issues.

Conclusions

The described technique is facilitated by the advanced imaging system, allowing a fast and effective method of correcting set-up errors before treatment. Extended implementation of this technique has improved treatment delivery to the majority of our prostate radiotherapy patients. The measurement of interfractional motion in this study is potentially valuable for margin reduction in intensity-modulated radiotherapy/volumetric arc therapy.

Advances in knowledge

This technique can be used within treatment time constraints, benefiting large numbers of patients by helping to avoid geographical miss and potentially reducing toxicity to organs at risk.External beam radiotherapy is a well-established treatment modality in the radical treatment of prostate cancer [1]. To minimise biochemical failure rates, doses of >72 Gy are required [2]. However, dose escalation is associated with additional long-term toxicity such as proctitis, faecal urgency and rectal bleeding, which have a significant impact on quality of life [3,4]. To help maximise the conformality of the dose to the prostate and limit the dose to normal tissues, advanced planning methods such as intensity-modulated radiotherapy (IMRT) and volumetric arc therapy (VMAT) have been developed. These novel delivery systems create highly conformal radiation plans resulting in a reduced margin for geometric set-up error compared with the previous technique of three- or four-field conformal plans. When using new technologies, therefore, accurate treatment verification procedures are vital to prevent geographical miss and limit normal tissue toxicity [5].Treatment verification has traditionally been performed using offline protocols. Megavoltage images created from the treatment beam [previously using X-ray film but currently with electronic portal imaging devices (EPIDs)] are reviewed retrospectively and the position of bony anatomy is compared with that on a reconstructed planning CT scan. Any large or consistent variation in position is managed with a shift in beam position for future radiation fractions, thus compensating for systematic errors [6,7].This approach has two main limitations. All forms of geometric uncertainties must be incorporated into set-up margins, and offline review cannot correct for any random set-up errors. As a result, larger margins are required, giving larger planning target volumes (PTVs) and causing irradiation of larger volumes of adjacent organs at risk (OARs) [8]. Possibly of greater significance is the reliance on matching bony anatomy, as it has been demonstrated that the prostate moves independently of bone [9,10]. Interfractional motion of the prostate has been reported to be significant, especially in the anteroposterior (AP) direction where bladder and rectal filling can cause displacement [11].It has been reported that clinical implementation of new and complex radiotherapy techniques in the UK has often been slow compared with other European countries. Jefferies et al [12] and Mayles [13] conducted audits between 2007 and 2009 and showed low implementation rates for IMRT, and to a lesser extent for image-guided radiotherapy (IGRT), which were primarily attributed to lack of equipment, staffing (all disciplines) and funding.An existing linear accelerator (Varian Clinac® 21EX, Varian Medical Systems, Palo Alto, CA) was upgraded with the Varian® On-Board Imager® (OBI; Varian Medical Systems) at the end of 2008, and two new linear accelerators with OBIs were commissioned in 2009. We were keen to see this facility implemented in a timely manner, given that a significant group of patients stood to benefit. Patient workload constraints demanded that there should be no reduction in patient throughput.We were aware of the use of fiducial markers (implanted radio-opaque seeds) for verification of prostate treatment set-up [14] which could overcome the problem associated with bony matching, which was our clinical standard at that time. Much of the early work with seeds relied on megavoltage imaging using EPIDs, but there are reports of problems with image quality and identification of individual seeds [14-16]. Incidence of seed migration or loss is generally low [10,15,17-20] and this may be especially so when seeds are implanted transperitoneally rather than transrectally.Importantly, it was reported that additional time to perform the matching and make corrections to set-up can add significantly to the overall time required for patient treatment [15,16].By utilising the Varian kilovoltage imaging, integrated matching software and remote application of couch corrections, we thought it would possible to apply this new technique without impacting on treatment times and patient throughput. As the fiducial matching technique was already clinically established elsewhere, it allowed implementation to be classified as a service development rather than an experimental or research study. This would facilitate faster implementation, as internal approval would suffice. We recognised the need for a robust system of staff training.Our objective, therefore, was to establish a clinical system for fiducial matching for patients requiring radiotherapy to the prostate gland, with the aim of improving treatment quality for a large number of patients.We describe our training and implementation techniques and present our results on interfractional motion, seed migration and interobserver variability relating to groups and individual patients.     

术中125I粒子植入治疗复发性脑胶质瘤的临床研究

目的 探讨复发性脑胶质瘤术中125I粒子植入治疗的近期治疗效果及并发症。 方法 回顾性分析58例复发性脑胶质瘤患者资料, 其中, 23例患者行单纯手术, 另外35例利用计算机三维治疗计划系统于术前或术中制定治疗计划, 术中依据所制定的剂量, 在肿瘤切除后的瘤床上植入125I粒子, 处方剂量为140~188 Gy。术后每2个月复查CT或MRI进行验证和质量评估, 随访8~32个月, 比较分析两组患者的肿瘤复发率、生存期及放射性并发症。 结果 单纯手术组中有20例复发, 复发率为87. 0%;有3例死于术后并发症。术中125I粒子植入治疗组中有23例复发, 复发率为65. 7%;有5例死于术后并发症, 4例发生顽固性脑水肿, 3例发生放射性脑坏死。术中125I粒子植入治疗组肿瘤复发时间[(97. 5±15. 3)周]明显长于单纯手术组[(62. 5±13. 6)周](t= 9. 21, P < 0. 05), 生存期[(60. 3±7. 1)周]亦明显长于单纯手术组[(43. 1±5. 5)周](t=13. 03, P < 0. 05)。单因素变量分析结果显示, 世界卫生组织肿瘤病理分级与肿瘤切除程度是影响患者生存率的独立因素。 结论 术中125I粒子植入治疗可降低脑胶质瘤的复发率, 有效增加复发性脑胶质瘤患者的生存时间。     

Declining brachytherapy utilization for high-risk prostate cancer—Can clinical pathways reverse the trend?

PurposeAlthough external beam radiation therapy (EBRT) plus a brachytherapy boost (BB) offers a 20% improvement in biochemical progression-free survival compared with dose-escalated EBRT alone for men with intermediate and high-risk prostate cancer, population studies show a concerning decline in BB utilization.MethodsWe modified our clinical pathway (CP) in January 2016 to indicate EBRT with BB as first-choice modality for high-risk prostate cancer, based on preliminary findings of Androgen Suppression Combined with Elective Nodal and Dose-Escalated Radiation Therapy. A retrospective review was performed on 659 patients with high-risk prostate cancer treated with definitive intent EBRT ± BB within a network of 19 sites between December 2011 and July 2017. χ² test was used to determine changes in practice pattern before vs. after CP modification.ResultsBefore CP modification, 25.2% of patients were planned for BB, compared with 45.4% afterward (p < 0.001). Among 23 nonbrachytherapist physicians, utilization of BB increased from 3.4% to 14.8% (p < 0.001) after CP modification. Among nine brachytherapists, utilization increased from 46.4% to 55.6% (p = 0.120). Among patients treated by a nonbrachytherapist who did not receive BB, the reason was physician preference in 59.7%, patient preference in 19.9%, and other in 20.4%.ConclusionBased on recent evidence suggesting improved biochemical progression-free survival with use of BB for high-risk prostate cancer, we modified our CP, after which we observed increased use of a BB across a network, especially among physicians who do not perform brachytherapy. However, physician preference remains the most significant factor in the nonutilization of BB. New mechanisms are needed to overcome this barrier.