Stereotactic Radiation Therapy of Intracranial Lesions Methodologic Aspects

A technique for stereotactic radiation therapy of cerebral tumours and arteriovenous malformations using a linear accelerator (6 MV photons) is proposed. Treatment relies on a fixation system that permits a precise use of the coordinates estimated at stereotactic angiography or stereotactic computed tomography. The field of treatment can be exactly outlined in the CT images during repeat examinations, thus facilitating the recognition of changes induced by radiation. The system also allows the extent of the arteriovenous malformation, as seen at angiography, to be accurately traced in the CT sections thus enabling evaluation of possible radiation damage to surrounding brain structures. The precision of the method as well as its hypothetical merits and disadvantages are discussed. The number of patients treated is still small and the follow-up time is too short in the majority of cases to allow definite conclusions. Examples of preliminary results are given.     

Implantation Metastasis along the Stereotactic Biopsy Tract in Anaplastic Astrocytoma: A Case Report

Objective and importance: Stereotactic biopsy for brain lesion is usually a safe procedure and the reported rate of complication is minimal. Moreover, local seeding along the trajectory of the stereotactic biopsy is a rare complication. The authors report a case of metastatic implantation along the trajectory of the stereotactic biopsy in anaplastic astrocytoma. Clinical presentation: A 64-Year-old man who presented with a one-month history of speech and memory disturbance underwent magnetic resonance (MR) imaging that disclosed a large mass in the left basal ganglia and medial temporal region. Intervention: Under the impression of high-grade glioma, computed tomography guided stereotactic biopsy was performed using the Riechert–Mundinger system. The histologic diagnosis was anaplastic astrocytoma. MR images after two cycles of chemotherapy showed a small enhancing portion in the middle of the biopsy tract, which was considered a surgical artifact and not included in the field of the following conventional fractionated radiation therapy. MR images three months after the completion of radiation therapy revealed that the enhancing portion had become a larger mass irrespective of good control of the primary tumor. Conclusion: Our findings suggest that tumor seeding along the stereotactic biopsy trajectory must be considered if an enhancing lesion appears in the MR image following the stereotactic biopsy. The cause and the prevention of implantation metastasis along the stereotactic biopsy tract are also discussed.     

The CT scanner as a therapy machine

Many tumors in the brain and in other tissues can be delineated precisely in images obtained with a CT scanner. After the scan is obtained the patient is taken to another room for radiation therapy and is positioned in the beam with the aid of external markers, simulators or stereotactic devices. This procedure is time consuming and subject to error when precise localization of the beam is desired. The CT scanner itself, with the addition of a collimator, is capable of delivering radiation therapy with great precision without the need for external markers. The patient can be scanned and treated on the same table, the isocenter of the beam can be placed precisely in the center of the lesion, the beam can be restricted to just those planes in which the lesion appears several arcs can be obtained by simply tilting the gantry, and the position of the patient in the beam can be monitored continuously during therapy. We describe here the properties of the CTX, the CT scanner modified for therapy.     

CyberKnife放射治疗肿瘤的临床研究

CyberKnife是一种影像引导下的无框架立体定向放射治疗肿瘤的国际前沿性新技术。它可使其放射线到达传统立体定向放射外科治疗技术无法接近的病变部位;在放射治疗前和放疗的过程中,其先进的影像导航系统可对病灶进行准确的实时监控和跟踪;目标如有移动,会补偿性的自动修正治疗床的位置或射束的方向;非等中心照射特征可使放射线的剂量分布在病变部位达到最大程度的均匀性和适形度,消除以往传统立体定向放射外科治疗技术在靶区剂量分布方面存在的冷点和热点问题;既可以实施单次治疗,也可以进行分次照射,是真正意义上的全新概念的肿瘤立体定向放射外科治疗系统。     

Advantages of Radiation Therapy Simulation with 0.35 Tesla Magnetic Resonance Imaging for Stereotactic Ablation of Spinal Metastases

The hybrid 0.35T magnetic resonance imaging (MRI) and radiation therapy system functions in part as a simulation platform for treatment planning. We have found that the images generated are particularly helpful for planning of stereotactic radiation therapy for spinal metastases. Advantages include the following: (1) Low-field MRI mitigates magnetic susceptibility artifacts caused by spinal hardware. (2) Volumetric pulse sequence provides isotropic images for improved target delineation. (3) Wide-bore MRI in the radiation oncology department allows for easy simulation in treatment position for accurate fusion across imaging modalities. (4) When patients are treated on the MRI and radiation therapy hybrid device, adaptive radiation therapy is available for special situations to avoid mobile organs at risk.     

Radiothérapie stéréotaxique des méningiomes intracrâniens

Meningiomas are the most common non-malignant tumours of the brain. Gross-total resection remains the preferred treatment, if achievable without morbidity. Radiation therapy is advocated for inoperable, incompletely resected, or recurrent grade 1 tumours, if there is a progressive, symptomatic lesion, or in case of functional impairment. Postoperative radiation therapy is recommended for grade 2 or 3 lesions. Fractionated stereotactic radiotherapy and stereotactic radiosurgery are high precision techniques, allowing good sparing of surrounding tissues. Fractionated stereotactic radiotherapy and stereotactic radiosurgery give comparable results, with excellent 5-year tumour control rates of more than 90% for benign meningiomas. Toxicity is low and seems equivalent, despite a biased use of fractionated stereotactic radiotherapy for larger meningiomas, close to critical structures. Fractionated stereotactic radiotherapy seems to be of special interest in the treatment of cavernous sinus or optic pathways meningiomas. The different therapeutic modalities should be discussed by a multidisciplinary team.     

Heavy charged-particle stereotactic radiosurgery: cerebral angiography and CT in the treatment of intracranial vascular malformations

A method is described for stereotactic localization of intracranial arteriovenous malformations (AVM) and for calculating treatment plans for heavy charged-particle Bragg peak radiosurgery. A stereotactic frame and head immobilization system is used to correlate the images of multivessel cerebral angiography and computed tomography. The AVM is imaged by angiography, and the frame provides the stereotactic coordinates for transfer of this target to CT images for the calculation of treatment plans. The CT data are used to calculate the residual ranges and compensation for the charged-particle beam required for each treatment port. Three-dimensional coordinates for the patient positioner are calculated, and stereotactic radiosurgery is performed. Verification of the accuracy of the stereotactic positioning is obtained with computer-generated overlays of the vascular malformation, stereotactic fiducial markers, and bony landmarks on orthogonal radiographs immediately prior to treatment. Using these procedures, the accuracy of the repositioning of the patient at each of a series of imaging and treatment procedures is typically within 1 mm in each of three orthogonal planes.     

Radiological assessment after stereotactic body radiation of lung tumours

The increasing use of stereotactic body radiation therapy for lung tumours comes along with new post-therapeutic imaging findings that should be known by physicians involved in patient follow-up. Radiation-induced lung injury is much more frequent than after conventional radiation therapy, it can also be delayed and has a different radiological presentation. Radiation-induced lung injury after stereotactic body radiation therapy involves the lung parenchyma surrounding the target tumour and appears as a dynamic process continuing for years after completion of the treatment. Thus, the radiological pattern and the severity of radiation-induced lung injury are prone to changes during follow-up, which can make it difficult to differentiate from local recurrence. Contrary to radiation-induced lung injury, local recurrence after stereotactic body radiation therapy is rare. Other complications mainly depend on tumour location and include airway complications, rib fractures and organizing pneumonia. The aim of this article is to provide a wide overview of radiological changes occurring after SBRT for lung tumours. Awareness of changes following stereotactic body radiation therapy should help avoiding unnecessary interventions for pseudo tumoral presentations.     

Radiosurgery Treatment Planning

The Gamma Knife (Leksell Gamma Unit; Elekta Radiosurgery, Inc, Atlanta, GA) and specially adapted linear accelerators are the systems most commonly used for intracranial stereotactic external beam irradiation. Both systems deliver collimated radiation to a treatment isocenter and a stereotactic head frame is required to align each target or portion of the target with this isocenter. Image acquisition and treatment planning define how the target is to be treated using one or more treatment positions. Diagnostic images are required to link the target volume with the stereotactic frame coordinate system. The number of diagnostic imaging modalities and the corresponding diagnostic technique(s) selected for optimum target localization are determined by the nature of the target and surrounding structures. The diagnostic modalities presented in this article include magnetic resonance imaging, magnetic resonance angiography, computerized tomography, and x-ray angiography. This review covers the fundamentals of radiosurgical treatment planning using the Gamma Knife as the system of reference.     

Fractionated radiotherapy of small inoperable lesions of the brain using a non-invasive stereotactic frame

Arteriovenous malformations (AVMs) and benign or low grade, small malignant tumors can be treated by stereotactic radiotherapy in a single fraction. This report describes a technique for stereotactic treatment of small lesions using conventional, fractionated, photon beam irradiation. The Laitinen's stereoadapter, non-invasive head frame was used. This device was tested for accuracy by serial mountings and found to be accurate within 1 mm. The accuracy of the dose delivered was within 2%. Adaptation of this device to the linear accelerator required the design of secondary circular collimators which decreased the penumbra from 3-4 mm to 2-3 mm. The dose fall off outside the target volume is steep enough when using two non-coplanar arcs (90 to 10% within 1 cm). Thermoluminescent dosimetry (TLD) in a humanoid phantom showed good correlation with the calculated dose. This system permits delivery of fractionated radiation therapy to small volumes, easily and accurately, under stereotactic conditions.     

Radiothérapie en conditions stéréotaxiques des gliomes de haut grade : une revue de la littérature

The purpose of this literature systematic review was the use of stereotactic radiotherapy in glioma. Research was performed in Medline/PubMed and associated references found in published articles without publication date limit. The quality of series is variable and many biases can be evidenced. Only two randomized trials have been published using stereotactic radiotherapy for up-front treatment. There is a lack of evidence of survival advantages to use this treatment at the time of diagnosis or relapse. There is also insufficient evidence regarding the benefice/harms in the use of stereotactic fractionated radiation therapy for patients with glioma. No recommendations can be enounced. Stereotactic irradiation as boost in primary diagnosed glioma or relapsed tumour is not associated with survival improvement. For relapsed patients, treatment needs to be discussed according to the other treatment options.     

Association d’une chimiothérapie ou d’un traitement ciblé à une irradiation stéréotaxique : état des lieux et recommandations préliminaires

The clinical management of systemic treatments and irradiation has long been studied for conventional irradiation. Yet, many associations are of difficult management and some drugs are contra-indicated in the concomitant setting owing to excessive toxicities. Sequential regimens using a therapeutic window of variable duration (based on drug half-life and tissue wash out) between each modality may be preferred for easier logistics and to avoid toxicities. The use of intra- and extracranial stereotactic ablative radiation therapy (hypofractionated) is expanding rapidly. Yet, little is known regarding associations between stereotactic ablative radiation therapy and systemic treatments. The short stereotactic ablative radiation therapy course in one day to two weeks offers a theoretical advantage compared to longer conventional irradiation with respect to shorter discontinuation of therapy. This may be of particular interest in situations where cancer is addicted to systemic treatment. While it is believed that stereotactic ablative radiation therapy might be safer because of limited irradiation volumes and steep gradients sparing most organs at risk, it should be noted that irradiation of normal tissues cannot be considered null; that stereotactic ablative radiation therapy has vascular effects in addition to other cell death radiation-induced mechanisms and cancer progression with discontinuation of systemic treatment is often reversible. To date, based on several phase II studies, combined stereotactic ablative radiation therapy and cetuximab can be recommended in head and neck tumours. Other stereotactic ablative radiation therapy-based combinations require prospective phase I–II studies and sufficient therapeutic window (in the order of at least 5 half-lives) between the systemic and local modalities must be left in routine practice.     

Imagerie inter- et intrafractions en radiothérapie stéréotaxique extracrânienne : quelles solutions pour quelles tumeurs ?

Due to high dose gradients, stereotactic body radiation therapy requires high precision in the location of the tumour. Uncertainties in the positioning can introduce serious damage on organs at risk and consequently can reduce tumour local control. A better tumour location can be achieved by controlling its position with an efficient inter and intrafraction imaging procedure. The various imaging techniques available on treatment systems are presented and performances are discussed. Finally, propositions are given in terms of imaging system according to the location treated by stereotactic body radiation therapy.     

Avis du groupe de travail missionné par l’Autorité de sûreté nucléaire concernant la radiothérapie stéréotaxique

PurposeAt the request of the French nuclear safety authority (Autorité de Sûreté Nucléaire, ASN) a working party of multidisciplinary experts was initiated to elaborate a report regarding propositions for the clinical practice of stereotactic radiation therapy and the related medical physics.Material and methodsSeveral stereotactic radiation therapy experts were audited by the working party, especially neurosurgeons and neuroradiologists, as well as radiation oncologists, medical physicists and radiation technologists. An international survey was conducted looking at legal requirements and guidelines concerning stereotactic radiation therapy. A national survey was conducted in France among 29 departments performing stereotactic radiation therapy. The working party report was submitted for advice to the permanent group of medical experts of ASN.ResultsAmong the 13 countries who responded, very few have legal documents. Some of them are stating that stereotactic radiation therapy must be performed in a radiotherapy department and only by well-trained professionals. Guidelines describing the role of each participant have been published in the USA. In France, stereotactic radiation therapy is performed with dedicated machines or adapted linear accelerators. In 2009, within the 29 departments, 4247 patients were treated with stereotactic radiation therapy representing 4% of the patients treated with external beam radiation therapy. Intracranial lesions were: 3383 and extracranial: 864. The working party of multidisciplinary experts made 7 recommendations. The first one saying that stereotactic radiation therapy must be considered as a radiotherapy. The permanent group of medical experts is asking to modify the “décret du 19 mars 2007” regarding “radiosurgery”.ConclusionThe medical benefit of stereotactic radiation therapy is well admitted and it is an increasingly used technique. This work through practical guidelines and legal propositions intends to promote a well-controlled development of this radiotherapy technique.     

A three-dimensional volume visualization package applied to stereotactic radiosurgery treatment planning

A comprehensive software package has been developed for visualization and analysis of 3-dimensional data sets. The system offers a variety of 2- and 3-dimensional display facilities including highly realistic volume rendered images generated directly from the data set. The package has been specifically modified and successfully used for stereotactic radiosurgery treatment planning. The stereotactic coordinate transformation is determined by finding the localization frame automatically in the CT volume. Treatment arcs are specified interactively and displayed as paths on 3-dimensional anatomical surfaces. The resulting dose distribution is displayed using traditional 2-dimensional displays or as an isodose surface composited with underlying anatomy and the target volume. Dose volume histogram analysis is an integral part of the system. This paper gives an overview of volume rendering methods and describes the application of these tools to stereotactic radiosurgery treatment planning.     

A comparison of survival rates for treatment of melanoma metastatic to the brain

Introduction: A retrospective review of 91 patients with brain metastases from malignant melanoma treated at New York University Medical Center between 1989-1999. Overall survival was the outcome evaluated. Methods: Charts of 91 patients having malignant melanoma with brain metastases were reviewed. Cases were stratified according to therapy: surgical excision, surgical excision plus whole brain radiation therapy, gamma knife stereotactic radiosurgery, gamma knife stereotactic radiosurgery plus whole brain radiation therapy, and whole brain radiation therapy alone. Patients treated with gamma knife stereotactic radiosurgery plus radiation therapy were combined with patients treated with surgical excision plus radiation therapy and compared to those treated with radiation therapy alone. Prognostic characteristics of the two groups were compared and survival curves were generated using the Kaplan-Meier method. The Cox proportional hazards model was used to control for prognostic factors that differed between the groups. Results: Patients treated with gamma knife stereotactic radiosurgery or surgical excision plus radiation therapy were younger, less likely to present with symptoms, and presented with fewer metastases to the brain than patients treated with radiation therapy alone. A survival benefit of 7.3 months (p = 0.05) was found to be associated with gamma knife radiosurgery or surgical excision plus radiation therapy over radiation therapy alone after controlling for differences in age, number of brain lesions, and presence of symptoms. Discussion: This retrospective study of 91 patients treated for melanoma metastases to the brain attempts to examine the effectiveness of different treatments in prolonging survival. Our results suggest that surgical excision or stereotactic radiosurgery with gamma knife in addition to radiation therapy may be more effective than radiation alone at prolonging survival for patients with a limited number of brain lesions. Conclusion: Survival of patients with melanoma metastases to the brain may be prolonged by treatment with gamma knife stereotactic radiosurgery or surgical excision plus whole brain radiation therapy.     

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.     

肝癌立体定向体部放射治疗的剂量学研究

目的:探讨立体定向体部放射治疗(stereotactic body radiotherapy,SBRT)在原发性肝癌(Primary he-patic carcinoma,PHC)放疗中的剂量学特点和临床价值,证实SBRT是PHC放射治疗的发展方向。方法:2009年1月至8月,可行放疗的PHC患者50例,CT薄层定位扫描,将图像分别输入SBRT和三维适形放射治疗(3DCRT)计划系统,同一病例做两个治疗计划,对靶区内剂量分布、危及器官(OARs)受量、适形度等进行对比。结果:SBRT计划中靶区剂量显著高于3DCRT,正常肝脏和邻近OARs的重要剂量学指标均显著性低于3DCRT,两计划中适形指数(CI)和病灶覆盖率(Coverage)无统计学差异(P>0.05),均匀指数(HI)对比差异有显著性(P<0.05)。SBRT治疗后3个月左右复查CT,观察疗效。50例患者均完成治疗和接受随访复查,局部控制率为88%,半年、1年生存率分别为86%、70%。不良反应少且轻,经处理可缓解消失。结论:SBRT在肝癌放疗中具有明显的剂量学优势,值得推广运用。     

食管癌的立体适形放疗和同步化疗

目的应用立体适形放射治疗技术并同步化学治疗食管癌,评价疗效和并发症.方法 52例食管癌给予立体适形放射治疗和同步化疗.放疗:2～2.2GY/次/天,5次/周,共计35次;5～8个共面适形固定野,总剂量70～76GY.化疗:顺氨氯铂20mg,5-氟脲嘧啶500 mg,每周一次,放疗开始即同步使用化疗,化疗在放疗前进行.结果治疗后1月～6月复查食管X片和CT,肿瘤缩小50%以上者92.31%(48/52);1年、3年和5年生存率分别为78.85%(41/52);41.46%(17/41);26.92%(7/26).结论立体适形放射治疗和同步化学治疗食管癌,疗效较好,并发症少,是不能手术患者的较好的一种治疗方式.     

螺旋断层放疗在肿瘤治疗中的应用

螺旋断层放疗是CT和直线加速器结合的放疗设备,具有360度照射、兆伏级螺旋CT(MVCT)影像引导、自适应计划等技术,可进行调强放疗、自适应放疗、立体定向外科等多种功能,适应证广泛.