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SRS Delivery Systems.pptx
- 1. Dedicated LINACS for SRS/SBRT Kimal Honour Djam, MS(2),MA,PGA
- 2. Introduction: The systems are designed from the ground up to –integrate high-precision radiation dose delivery at a high dose rate –precise tumor localization using image-guided radiotherapy (IGRT) –deliver high-precision conformal doses to irregularly shaped tumors while sparing adjacent organs at risk, Each modality is distinguished by the beam produced and its modeling, treatment delivery, multileaf collimators (MLCs), applicators, dose rate, specialized treatment planning, and IGRT techniques used
- 3. 3 Main characteristics of SRS LINACS
- 4. 4 Main characteristics of SRS LINACS
- 5. 5 BRAINLAB NOVALIS AND THE NOVALIS Tx (Image courtesy of Brainlab AG) The Novalis radiosurgery platform The linac is a Varian accelerator whereas the beam-shaping device, the localization and tracking system, and the treatment planning system (TPS) are all Brainlab components for the Novalis The Novalis radiosurgery family delivers noninvasive, frameless, shaped-beam treatments for cancerous and noncancerous conditions of the entire body
- 6. 6 THE NOVALIS:KEY FEATURES AND COMPONENTS Novalis® radiosurgery accessories Varian/Brainlab Novalis® Tx radiosurgery system
- 7. 7 THE NOVALIS:KEY FEATURES AND COMPONENTS • The Novalis Tx system includes: • Energy: 6 to 20 MV, a special SRS 6 MV photon beam, going through a thinner flattening filter, is used, and the dose rate is 1000 monitor units (MU) per minute • Tungsten120-leaf high-definition (HD120®) MLC. It has 32 leaf pairs with 2.5 mm leaf width (projection at the isocenter), • surrounded by 28 leaf pairs of 5-mm projection width • iPlan RT for treatment planning(Pencil Beam (PB) or Monte Carlo (MC)); • ExacTrac and 6D robotic couch for image-guided patient positioning, correcting directional inaccuracies and rotational misalignments
- 8. 8 THE NOVALIS:KEY FEATURES AND COMPONENTS • PortalVisionTM, which offers treatment verification during dose delivery, and dosimetry QA for verifying system performance • On-Board Imager® (OBI), providing cone beam computed tomography (CBCT) for volumetric soft tissue discrimination and kilovoltage (kV) fluoroscopic imaging for respiratory motion verification (Brainlab) • Patient setup does not rely on source-to-skin distance (SSD) information; it uses external body markers and the ExacTrac system • The ODI is not blocked and SSD could be used in patient setup for conventional cases ? • For even smaller circular targets (trigeminal neuralgia), 1 cm or less, stereotactic cones are used (the penumbra is reduced, and the dose gradient is steep).
- 9. 9 THE NOVALIS:ExacTrac • It allows for patient setup with high-resolution stereo x-ray imaging • ExacTrac relies mostly on bony anatomy registration. For soft tissue targets, implanted fiducial markers are needed for localization • The ExacTrac X-Ray 6D system is mainly an integration of 2 subsystems: 1. an infrared (IR)-based optical positioning system (ExacTrac) for initial patient setup and precise control of couch movement, and 2. a radiographic kV x-ray imaging system (X-Ray 6D) for position verification and readjustment based on the internal anatomy or implanted fiducial
- 10. 10 THE NOVALIS: The Infrared Tracking System • The infrared tracking component of the ExacTrac X-Ray 6D system includes 2 stereoscopic IR cameras, passive IR reflecting spheres placed on a patient’s surface, and a reference device (the reference star) that contains 4 reflective circle. • The IR cameras, mounted from the ceiling, record the positions of IR reflective markers on the patient’s surface • The reference star attached to the couch, is used to precisely determine the couch’s movement
- 11. 11 THE NOVALIS: The Infrared Tracking System • During treatment, the real-time data obtained from this IR system is used to monitor the patient’s position for unexpected changes and/or to track motion for gated delivery
- 12. 12 THE NOVALIS:ExacTrac kV X-Ray System • ExacTrac consists of two kV x-ray units in the treatment room floor and two ceiling-mounted amorphous silicon flat panel detectors 1. the x-ray tubes and corresponding detector panels are in fixed positions, 2. the x-rays project in an oblique direction relating to the patients, 3. the source isocenter and source detector distance is relatively large (2.24 and 3.62 meters, respectively).
- 13. 13 THE NOVALIS:Respiratory gating • The ExacTrac Adaptive Gating system uses stereoscopic kilovoltage radiographs for patient positioning and the IR marker detection system for respiratory tracking and gating of the treatment beam
- 14. 14 THE NOVALIS: Respiratory gating
- 15. 15 ACCURAY ROBOTIC RADIOSURGERY: THE CYBERKNIFE CyberKnife® VSI robotic radiosurgery system CyberKnife® M6TM radiosurgery suite with the InCiseTM MLC
- 16. 16 ACCURAY ROBOTIC RADIOSURGERY: THE CYBERKNIFE The target is fixed and is made of a tungsten alloy. The system has a straight- through waveguide, steering coils, no flattening filter, sealed air-filled ionization chambers, a primary collimator, and a secondary set having circular apertures with diameters ranging from 5 to 60 mm at a source-to-axis distance (SAD) of 80 cm It consists of two stacked hexagonal banks of tungsten blades forming a dodecagonal(?) opening
- 17. 17 THE TRILOGY SYSTEM The Varian Trilogy® is a comprehensive delivery system. It can be used for 3-D conformal radiation therapy (CRT), IMRT, IGRT, dynamic adaptive radiotherapy (DART), and both intracranial and extracranial stereotactic techniques The Trilogy platform combines a multimodality linac with MLC, advanced imaging capabilities, patient immobilization, target tracking and motion management, and treatment planning (Eclipse)
- 18. 18 THE TRUEBEAM SYSTEM This platform for image-guided radiotherapy and radiosurgery is a fully integrated system (imaging, beam delivery, and motion management) designed from the ground up to treat moving targets and to improve operation, precision, and speed The system also delivers Varian’s new gated RapidArc® radiotherapy, which compensates for tumor motion by synchronizing imaging with dose delivery during a continuous rotation around the patient.
- 19. 19 THE TRUEBEAM SYSTEM This platform for image-guided radiotherapy and radiosurgery is a fully integrated system (imaging, beam delivery, and motion management) designed from the ground up to treat moving targets and to improve operation, precision, and speed The system also delivers Varian’s new gated RapidArc® radiotherapy, which compensates for tumor motion by synchronizing imaging with dose delivery during a continuous rotation around the patient.
Editor's Notes
- The systems are designed from the ground up to integrate high-precision radiation dose delivery at a high dose rate and precise tumor localization using image-guided radiotherapy (IGRT deliver high-precision conformal doses to irregularly shaped tumors while sparing adjacent organs at risk, which makes them suitable for dose escalation protocols, potentially resulting in higher tumor control rates and fewer side effects Different manufacturers have adopted different technologies and incorporated different hardware and software tools into their designs. Each modality is distinguished by the beam produced and its modeling, treatment delivery, multileaf collimators (MLCs), applicators, dose rate, specialized treatment planning, and IGRT techniques used. Some of the commercially available technologies are different from the classical C-arm type accelerator (CyberKnife, Hi-ART, ViewRay, and Vero).
- 6D couch very important for SIMT cases.
- The Novalis® radiosurgery platform, featuring Novalis and Novalis Tx systems, brings together technologies from Varian Medical Systems, Inc. (Palo Alto, California) and Brainlab AG (Feldkirchen, Germany) to create a fully integrated SRS/SBRT solution (Solberg et al. 2001) The Novalis radiosurgery family delivers noninvasive, frameless, shaped-beam treatments for cancerous and noncancerous conditions of the entire body. The high-definition shaped beam technology dynamically conforms the treatment beam to the lesion while protecting surrounding healthy tissue. Although these machines do come with a stereotactic frame for SRS, the intracranial radiosurgery treatments are usually achieved without the invasive frame. With the use of robust IGRT methods and immobilization techniques, the quality of the SRS treatment is not compromised
- The Novalis radiosurgery family delivers noninvasive, frameless, shaped-beam treatments for cancerous and noncancerous conditions of the entire body. The treatment of a variety of intracranial targets is monitored by specific software tools. X-ray images are acquired and verified with the ExacTrac® x-ray 6D IGRT imaging system, during patient setup and treatment delivery. They provide detection and visualization of displacements.
- Some of the features of the Novalis system include an energy of 6 MV; a 52-leaf micro-MLC (Brainlab m3® high-resolution MLC), allowing for the delivery of highly conformal dose, improved margins, and better protection of surrounding tissue; Brainlab iPlan® Radiation Therapy (RT) Treatment Plan for treatment planning; and ExacTrac for accurate and automated patient positioning (Brainlab). The system includes a full range of stereotactic hardware for immobilization, setup, and QA, such as head rings, conical collimators, and target positioning hardware (Figure 4.3).
- To increase the steepness of the dose, the penumbra of the collimator system must be minimized. For radiosurgery, the recommended limit for dose gradient in the beam penumbra (from 80% to 20%) is at least 60%/3 mm. Most commercially available MLCs have a penumbra specification from 4 to 8 mm. The m3 micro-MLC has an effective penumbra of less than 3 mm for all SRS field sizes and meets the SRS requirements (Schell et al. 1995). The dose can then be tailored to the shape of the lesion while sparing healthy tissue.
- ExacTrac includes two different stereoscopic imaging systems. The real-time infrared (IR) system measures the position of the patient’s surface. It is used for initial patient positioning, monitoring patient position, and tracking patient motion during gated treatment delivery. ExacTrac also uses the IR images to move the 6D robotic couch with submillimeter precision and accuracy. The X-ray imaging system (ETX) gives accurate localization based on internal anatomy and/or implanted fiducials.
- It also comes with an integrated optical infrared tracking system for continuous monitoring of patient position throughout treatment. The system uses a pair of infrared video cameras to triangulate on an external set of fiducial markers, the Body Marker Array, which is affixed to the anterior thorax and/or abdomen of the patient (Brainlab). It is calibrated in the treatment reference space of the linear accelerator, and it controls the treatment couch motions, guiding the lesion to the linac isocenter. Two stereoscopic IR cameras, mounted from the ceiling, record the positions of IR reflective markers on the patient’s surface. From these images, the system computes the 3D position of the patient. The IR markers are positioned identically on the patient during CT simulation and at treatment time. Based on the treatment plan isocenter, the ExacTrac software calculates the shifts and rotations needed to bring the patient to the correct treatment location. Figure 3 shows the IR markers on a patient and the computer screen after alignment. This initial positioning is followed by more accurate X-ray positioning. During treatment, the real-time data obtained from this IR system is used to monitor the patient’s position for unexpected changes and/or to track motion for gated delivery. Because IR positioning is based on the patient’s external surface, it is inherently more accurate for cranial targets than for body targets. The reference star is a reference against which the movement of patient mounted markers is measured, and also to track couch location during the patient positioning process
- During treatment, the real-time data obtained from this IR system is used to monitor the patient’s position for unexpected changes and/or to track motion for gated delivery. Because IR positioning is based on the patient’s external surface, it is inherently more accurate for cranial targets than for body targets. The IR system samples marker positions at a frequency of 20 Hz and therefore may also be used to monitor patient motion. The y-axis is a 3-dimensional (3D) composite of the combined motion of 5 markers placed on a patient’s chest
- Two x-ray images are obtained after a patient is initially setup with the ExacTrac (infrared) system. These images are then compared with the patient’s 3-dimensional (3D) CT simulation images with the corresponding isocenter in terms of digital reconstructed radiography (DRR). The software provides several options for matching the images. The manual match and the 3D (3 degrees of freedom) fusion methods assume that the patient was setup with no rotational offsets
- Although it may be possible to track lung tumors directly using plane radiography,25 the ExacTrac Adaptive Gating system is currently designed to be used with radiopaque fiducial markers implanted near the target isocenter These markers are implanted before treatment planning begins and should be placed close enough to the target anatomy so that they can be seen within the field of view of the x-ray localization system at the time of treatment. It is assumed that the spatial relationship between markers and target anatomy will remain relatively fixed The 3D movement of the patient’s anterior surface is tracked via the IR markers and the anterior-posterior (A-P) component of this trajectory is used to monitor breathing motion. Target position is expected to be correlated with this breathing motion
- The 3D movement of the patient’s anterior surface is tracked via the IR markers and the anterior-posterior (A-P) component of this trajectory is used to monitor breathing motion. Target position is expected to be correlated with this breathing motion The ExacTrac system plots breathing motion vs. time, and a gating reference level is specified on this breathing trace (Fig. 4). The gating level is the amplitude of the breathing trace at which the kV x-ray images for patient localization will be triggered The images are obtained sequentially at the instant the breathing trace crosses this level during the exhale phase. Because the patient will be localized based on these images, the gating level should be set at the same phase in the breathing cycle at which the planning CT data was obtained. Within each image, the user locates the positions of the implanted fiducials. From these positions, the system reconstructs the 3D geometry of the implants and determines the shifts necessary to bring them into alignment with the implants’ orientation as determined from the planning CT. These localization shifts are then made to the patient just as with the basic ExacTrac system. Once the patient has been positioned in this way, the target will pass through the linac isocenter as the breathing trace passes through the gating level Finally, a gating window (Fig. 4) is determined. The system can gate the beam in both inhale and exhale phases of the breathing cycle; however, the treatment beam is gated during the exhale phase because hysteresis of target motion has been observed during the breathing cycle.41 Localization is also performed in the exhale phase; therefore, it is expected that the target is most accurately positioned here
- The CyberKnife is a frameless robotic system for radiosurgery that consist of a lightweight linear accelerator, a robotic delivery system, and noninvasive image-guided localization to delivers a great number of independently targeted, non-coplanar radiation beams with high precision under continuous X-ray and optic image guidance for motion management. The primary control point of the CyberKnife operational system is a graphical user interface delivery system that initiates and monitors operations of the different components. During treatment delivery, the software monitors the system status and safety controls, reports errors, manages the patient database and records treatment data log files for post-treatment assessment and analysis. The target localization system (TLS) is composed of two orthogonally positioned diagnostic X-ray sources and two corresponding amorphous silicon plates. They provide near real-time digital X-ray images of the patient in the treatment position. During patient setup, the target position is determined (relative to nearby bony anatomy or, in extracranial treatments, implanted fiducials) by comparison of the left anterior oblique (LAO) and right anterior oblique (RAO) X-rays, with digitally reconstructed radiographs (DRRs) in the same LAO and RAO positions derived from the preoperative CT scans. The system uses a movable treatment table to position the patient before treatment. This operating table can be moved automatically along five axes (three translations and two rotations). The final rotational movement (yaw) is applied manually. The newly developed robotic couch (RoboCouch Patient Positioning System, Accuray Incorporated) can be adjusted entirely robotically (i.e., based on image information and without intervention by the user) in all 6 axes
- The target is fixed and is made of a tungsten alloy. The linac is mounted on a highly maneuverable robotic manipulator arm This manipulator can position the linac with 6 degrees of freedom and 0.12-mm precision. The system has a straight-through waveguide, steering coils, no flattening filter, sealed air-filled ionization chambers, a primary collimator, and a secondary set having circular apertures with diameters ranging from 5 to 60 mm at a source-to-axis distance (SAD) of 80 cm. Since 2008, a collimator It consists of two stacked hexagonal banks of tungsten blades forming a dodecagonal opening. It can be set to 12 circular field sizes (from 5 to 60 mm, nominally equal to the system’s 12 fixed collimator sizes). This allows the use of several different aperture sizes in a single treatment plan, optimizing dosimetry and treatment time for SRS. The beam flatness is within 14% when measured at a depth of 5 cm, a SAD of 80 cm, and a secondary collimator of 4 cm.
- Varian’s linac is characterized by a gridded electron gun that controls the beam from full on to full off in 2 to 3 ms, a waveguide, and an achromatic three-field bending magnet coupled with a 3-D servo-system and a solenoid (Varian Medical Systems) Real-time beam steering and dual sealed ion chambers working as a feedback loop to keep this steering accurate result in a tightly focused beam with optimal flatness, symmetry, and dosimetry. The 2-mm circular focal spot allows for steeper dose gradients and sharper portal images. new Varian linacs is an energy switch that optimizes the guide length to deliver the highest dose rates for all energies up to 1000 MU/min for stereotactic beams at maximum dose depth (dmax) and 100-cm SAD The Trilogy has a separate small filter optimized for small field treatments in the 6-MV high dose rate mode (HDRM) of 1000 MU/min The MillenniumTM MLC is a two-bank, 120-leaf collimator with 5-mm leaf widths at the isocenter for the central 20 cm of the 40 × 40 cm field. The small leaf resolution makes it suitable for small lesions as in stereotactic treatments. Fast leaf speed and interdigitation capabilities result in shorter treatment times. The MLC operates in static, dynamic (step-and-shoot and sliding window delivery), and conformal arc modes. For stereotactic techniques, the Trilogy Tx model comes with the HD120 MLC and conical collimators. The maximum field size for SRS is 15 × 15 cm in HDRM, and the maximum dose per field is 6000 MUs (Varian Medical Systems)
- Varian’s linac is characterized by a gridded electron gun that controls the beam from full on to full off in 2 to 3 ms, a waveguide, and an achromatic three-field bending magnet coupled with a 3-D servo-system and a solenoid (Varian Medical Systems) Real-time beam steering and dual sealed ion chambers working as a feedback loop to keep this steering accurate result in a tightly focused beam with optimal flatness, symmetry, and dosimetry. The 2-mm circular focal spot allows for steeper dose gradients and sharper portal images. new Varian linacs is an energy switch that optimizes the guide length to deliver the highest dose rates for all energies up to 1000 MU/min for stereotactic beams at maximum dose depth (dmax) and 100-cm SAD The Trilogy has a separate small filter optimized for small field treatments in the 6-MV high dose rate mode (HDRM) of 1000 MU/min The MillenniumTM MLC is a two-bank, 120-leaf collimator with 5-mm leaf widths at the isocenter for the central 20 cm of the 40 × 40 cm field. The small leaf resolution makes it suitable for small lesions as in stereotactic treatments. Fast leaf speed and interdigitation capabilities result in shorter treatment times. The MLC operates in static, dynamic (step-and-shoot and sliding window delivery), and conformal arc modes. For stereotactic techniques, the Trilogy Tx model comes with the HD120 MLC and conical collimators. The maximum field size for SRS is 15 × 15 cm in HDRM, and the maximum dose per field is 6000 MUs (Varian Medical Systems)
- Varian’s linac is characterized by a gridded electron gun that controls the beam from full on to full off in 2 to 3 ms, a waveguide, and an achromatic three-field bending magnet coupled with a 3-D servo-system and a solenoid (Varian Medical Systems) Real-time beam steering and dual sealed ion chambers working as a feedback loop to keep this steering accurate result in a tightly focused beam with optimal flatness, symmetry, and dosimetry. The 2-mm circular focal spot allows for steeper dose gradients and sharper portal images. new Varian linacs is an energy switch that optimizes the guide length to deliver the highest dose rates for all energies up to 1000 MU/min for stereotactic beams at maximum dose depth (dmax) and 100-cm SAD The Trilogy has a separate small filter optimized for small field treatments in the 6-MV high dose rate mode (HDRM) of 1000 MU/min The MillenniumTM MLC is a two-bank, 120-leaf collimator with 5-mm leaf widths at the isocenter for the central 20 cm of the 40 × 40 cm field. The small leaf resolution makes it suitable for small lesions as in stereotactic treatments. Fast leaf speed and interdigitation capabilities result in shorter treatment times. The MLC operates in static, dynamic (step-and-shoot and sliding window delivery), and conformal arc modes. For stereotactic techniques, the Trilogy Tx model comes with the HD120 MLC and conical collimators. The maximum field size for SRS is 15 × 15 cm in HDRM, and the maximum dose per field is 6000 MUs (Varian Medical Systems)