Gamma Knife End-to-End verification
Gamma Knife radiosurgery is considered as the best treatment choice for all types of brain lesions (malignant or benign) and functional disorders of the brain. The introduction of the latest Gamma Knife treatment system, the Leksell Gamma Knife® IconTM, has extended the treatment options that Gamma Knife offers to single or hypo-fractionated Stereotactic Radiosurgery (SRS) treatments, using a stereotactic frame or a frameless thermoplastic mask, and can treat small or larger tumor volumes. A cone-beam computed tomography (CBCT) and a high-definition motion management system have been integrated allowing for frameless patient positioning and monitoring. Treatment Planning System is performed by Leksell GammaPlan® which includes the commonly used Tissue-Maximum-Ratio (TMR) and the recently introduced Convolution algorithms. The Convolution algorithm is based on a combination of the collapsed cone convolution and the pencil beam convolution offering a dose engine specifically designed for the calculation of the deposited dose in heterogeneous tissues.
The above new features have increased the requirements for spatial and dosimetric accuracy and precision leading to a more complex quality assurance (QA) program. This fact has highlighted the necessity of End-to-End testing during commissioning and on a periodic basis. The End-to-End procedure must include the Image-Guided Radiation Therapy (IGRT) process, the dosimetry of small fields, and the verification of the spatial accuracy in the stereotactic 3D space. RTsafe’s Prime anthropomorphic head phantom in combination with the Remote Dosimetry Services offered by RTsafe’s scientific personnel offers a comprehensive solution for the independent End-to-End validation of Gamma Knife® IconTM SRS treatments. Prime phantom based on an actual’s patient CT scan provides a true-to-life human anatomy with realistic contrast in MR and CT imaging enabling an authentic simulation of the treatment chain. The phantom is compatible with both frame and frameless treatment options without any variations from the actual workflow. RTsafe’s remote dosimetry service package provides point (OSLDs), 2D (EBT4 films) & 3D (polymer gel) dosimetric and geometric accuracy through independent dose measurements, assuring traceability to a secondary standard dosimetry laboratory.
Prime phantom combined with RTsafe’s dosimetry services is the most appropriate methodology for the commissioning/start-up (see Figure 1), periodic QA, validation of clinical parameters, training, and research of the Gamma Knife® IconTM system. The heterogeneous anatomical areas of the Prime enable the proper validation of the Convolution dose calculation algorithm through advanced dosimetry. Another important key feature is the End-to-End perspective, including the co-registration procedure between CBCT and CT images, since Prime provides real contrast between bone and soft tissue areas. A significant number of scientific papers on RTsafe’s technology have been published providing a piece of strong scientific evidence about the added value of RTsafe in SRS QA. One of these publications focuses on validating the PTV margin for Gamma Knife® IconTM frameless treatment using the Prime phantom.
For more information on RTsafe phantoms and services, please visit www.rt-safe.com.