ELEKTA立体定向体架的质量保证和质量控制

引言目前,放射治疗仍是治疗恶性肿瘤的主要手段之一[1]。在放射治疗过程中,摆位是计划执行的一个重要环节。为了保证患者在定位、验证以及每次治疗时体位的一致性,需要用到体位固定装置[2,3]。立体定向体架是保证精确摆位、定位、治疗前验证等必不可缺的工具。体架的精确度直接影响治疗的效果,所以必须对体架进行定期的质量保证和质量控制检验。本文主要讨论ELEKTA体架的质量保证和质量控制的内容与方法。1材料与方法1.1一般材料ELEKTA SLi电子直线加速器、剂量仪(Famer2570/1B)、TOSHIBA模拟定位机、胶片、刻度尺、金属小球装置、ELEKTA体架。1.2定向坐标的校正将一个金属小球装置固定在预先设置的坐标上,见图1,拍验证片,以检查体架坐标系统(指示标尺与内置金属丝坐标系统)的一致性。(1)把带有定向坐标尺的体架放在治疗床上,用水平尺把体架调整水平。调整治疗床到一个适当的位置。(2)把金属小球装置放在定向标尺一个适当的坐标上,调整激光灯到同一个坐标。(3)调整机架角度为90°,用10cm×10cm射野进行曝光。摄影条件为:管电压40KV、管电流100mA、曝光时间0.1s。(4)冲洗胶片,计算体架内...     

双下肢辅助标记在立体定向体架固定盆腔肿瘤病人中的应用

[目的]评价放疗中使用立体定向体架配负压成型真空袋固定盆腔肿瘤病人时,除在胸骨选取摆位参考点之外,使用双下肢摆位标记（胫骨标记尺）能否提高治疗中心的精度。[方法]12例需要盆腔照射的病人分别使用A方法（胸骨选取摆位参考点＋胫骨标记尺）和B方法（胸骨选取摆位参考点）摆位固定,拍摄治疗射野证实片,同基准片比较产测量等中心各轴偏差。[结果]两种摆位方法均存在偏差,但偏差范围不同。其中A方法X,Y,Z轴偏差分别为1．47±1．05mm,1．2±0．75mm和1．46±0．52mm,B方法x,Y,z轴偏差分别为6．48±2．5mm,1．96±1．3mm和5．6±1．9mm。两组比较X．Z轴偏差有显著性差异（P〈O．001）。[结论]使用胫骨标记尺对双下肢进行辅助标记摆位能明显减少盆腔射野等中心摆位误差。     

Frame Slippage Verification in Stereotactic Radiosurgery

Purpose: To develop a method for detecting frame slippage in stereotactic radiosurgery by interactively matching in three dimensions Digitally Reconstructed Radiographs (DRRs) to portal images.Methods and Materials: DRRs are superimposed over orthogonal edge-detected portal image pairs obtained prior to treatment. By interactively manipulating the CT data in three dimensions (rotations and translations) new DRRs are generated and overlaid with the orthogonal portal images. This method of matching is able to account for ambiguities due to rotations and translations outside of the imaging plane. The matching procedure is performed with anatomical structures, and is used in tandem with a fiducial marker array attached to the stereotactic frame. The method is evaluated using portal images simulated from patient CT data and then tested using a radiographic head phantom.Results: For simulation tests a mean radial alignment error of 0.82 mm was obtained with the 3D matching method compared to a mean error of 3.52 mm when using conventional matching techniques. For the head phantom tests the mean alignment displacement error for each of the stereotactic coordinates was found to be Δx = 0.95 mm, Δy = 1.06 mm, Δz = 0.99 mm, with a mean error radial of 1.94 mm (SD = 0.61 mm).Conclusion: Results indicate that the accuracy of the system is appropriate for stereotactic radiosurgery, and is therefore an effective tool for verification of frame slippage.     

Stereotactic Radiosurgery and Stereotactic Body Radiotherapy in the Management of Oligometastatic Disease

Stereotactic radiosurgery (SRS) and stereotactic body radiotherapy (SBRT) represent non-invasive, efficacious and safe radiation treatments for the ablation of intracranial and extracranial metastases. Although the use of SRS has been established by level 1 evidence for patients presenting with up to three or four brain metastases for at least a decade, the paradigm of ablating a limited number of extracranial metastases (typically up to five, known as oligometastatic disease) has yet to be proven beyond the few reported but highly encouraging phase II randomised trials. In this overview, we summarise the phase III randomised controlled trials evaluating SRS for intact brain metastases and postoperative surgical cavities and introduce the limited literature and future concepts for treating patients with more than five intracranial metastases. Next, we summarise the published phase II randomised controlled trials specific to SBRT and oligometastatic disease, while briefly describing and contrasting the technical principles and biological mechanisms of SBRT versus conventional radiation. Phase III evidence for SBRT is needed, and we summarise ongoing trials in this overview. Ultimately, SRS and SBRT have become cornerstone therapeutic options for patients with oligometastatic disease and the future is bright for these patients, considering that not so long ago they were considered incurable and relegated to palliation alone.     

Reducing uncertainty in health-care resource allocation

A key task for health policymakers is to optimise the outcome of health care interventions. The pricing of a new generation of cancer drugs, in combination with limited health care resources, has highlighted the need for improved methodology to estimate outcomes of different treatment options. Here we introduce new general methodology, which for the first time employs continuous hazard functions for analysis of survival data. Access to continuous hazard functions allows more precise estimations of survival outcomes for different treatment options. We illustrate the methodology by calculating outcomes for adjuvant treatment of gastrointestinal stromal tumours with imatinib mesylate, which selectively inhibits the activity of a cancer-causing enzyme and is a hallmark representative for the new generation of cancer drugs. The calculations reveal that optimal drug pricing can generate all win situations that improve drug availability to patients, make the most of public expenditure on drugs and increase pharmaceutical company gross profits. The use of continuous hazard functions for analysis of survival data may reduce uncertainty in health care resource allocation, and the methodology can be used for drug price negotiations and to investigate health care intervention thresholds. Health policy makers, pharmaceutical industry, reimbursement authorities and insurance companies, as well as clinicians and patient organisations, should find the methodology useful.     

Cost-Effectiveness of Stereotactic Radiosurgery and Stereotactic Body Radiation Therapy in Treating Brain Metastases

Single-fraction stereotactic radiosurgery (SRS) is a highly used tool in managing brain metastases, alongside its multifraction counterpart – stereotactic body radiation therapy (SBRT). These radiation therapy techniques have been associated with excellent clinical outcomes, such as decreased local recurrence, increased survival, and improved palliative effects. However, present literature concerning the cost-effectiveness of these techniques remain scarce. Based on the current procedure terminology codes involving services provided during radiation consultation, treatment, and follow-up in our institution, 3-fraction SBRT with a 3-dimensional plan and intensity modulated radiation therapy cost 27% and 17% more than SRS, respectively. A 32% and 34% price increase can, respectively, be seen in 5-fraction SBRT with 3-dimensional plan and intensity modulated radiation therapy delivery sessions relative to 3-fraction SBRT administration. Cost savings between these procedures were associated with the radiation therapy delivery sessions instead of the treatment planning process. These analyses indicate that SRS appears to be a less expensive and time-intensive option than SBRT in our institution. However, additional comparative analyses regarding SRS and SBRT are needed to explore the clinical and financial benefits of these radiation therapy techniques.     

Current Evidence for Stereotactic Body Radiotherapy in Lung Metastases

Lung metastases are the second most common malignant neoplasms of the lung. It is estimated that 20–54% of cancer patients have lung metastases at some point during their disease course, and at least 50% of cancer-related deaths occur at this stage. Lung metastases are widely accepted to be oligometastatic when five lesions or less occur separately in up to three organs. Stereotactic body radiation therapy (SBRT) is a noninvasive, safe, and effective treatment for metastatic lung disease in carefully selected patients. There is no current consensus on the ideal dose and fractionation for SBRT in lung metastases, and it is the subject of study in ongoing clinical trials, which examines different locations in the lung (central and peripheral). This review discusses current indications, fractionations, challenges, and technical requirements for lung SBRT.