Transforming radiation oncology’s new vision
As the pioneer in image guided radiation therapy (IGRT), it was logical for Elekta to point the way to IGRT’s next dimension: incorporating more intelligence and automation into what IGRT-equipped systems “see” to further refine targeting accuracy. As in the development of Elekta Synergy, Elekta’s first IGRT treatment system, the company once again leveraged our collaborative relationships with customer partners to gain insight in research and product development. Through these efforts, Elekta is addressing the needs of healthcare systems and patients by reducing hospitalization costs and providing better treatment options.
The technology on which these recent IGRT advancements is based is Elekta Synergy®, the first linear accelerator to bring 3D image guidance into the treatment process—enabling soft tissue imaging with the patient in the treatment position at the time of treatment. This critical technological advance has enabled clinicians, on a daily basis, to correct patient setup errors and increase treatment accuracy. Elekta Synergy is the only treatment system with a fully integrated imaging workflow.
Providing key imaging tools, Elekta Synergy addresses one of the most significant treatment challenges: organ motion. These imaging tools include 3D volumetric cone-beam imaging for soft tissue visualization; 2D real-time, fluoroscopic-like imaging for targets that move frequently; and 2D kV imaging for standard and orthogonal planar imaging.
New XVI tools critical in breathing motion management and better targeting
Elekta refers to its soft tissue visualization capability and associated tools as X-Ray Volume Imaging or XVI. The latest iteration of XVI, version 4.5, includes two key feature sets known as Symmetry™ and Intuity™, both CE-marked for commercial distribution in Europe. Both Symmetry and Intuity do more than merely improve visualization—they exploit the very capability of integrated imaging to automate the process of tumor targeting, thereby improving workflow. They also enhance clinical judgment by giving physicians more insight into the motion and position of targets and healthy tissues.
Symmetry—managing respiratory motion
Building on the foundation of Elekta Synergy, Symmetry is the next generation of image guidance, providing a simple and intuitive way to increase efficiency, reduce margins and maximize the probability of symmetrical dose distributions. The results are new approaches to the treatment of thoracic cancers that instill greater physician confidence to treat moving targets aggressively without compromising the safety of adjacent critical structures. Designed to help manage respiratory motion, Symmetry includes 4D acquisition (i.e, time is the fourth dimension), in-line reconstruction and automated 4D registration. These tools assist in determining a time-weighted average position of the tumor for each treatment. This solution is unique to Elekta and differs from other systems on the market, which use external surrogates, such as a belt or reflective markers.
A problem with surrogates is that they don’t necessarily have a stable relationship with the internal anatomy1. In addition, many lung cancer patients exhibit significant baseline shifts2 in tumor position during their course of treatment. Symmetry characterizes the extent of tumor motion and provides correction vectors to reposition the target to the original planned position. Removal of baseline shifts supports the delivery of conventional treatments with only small margins required for breathing motion3.
In a recent study, investigators led by S.S. Korreman found that the impact of 4D daily image guidance in the context of patient respiratory management was considerably more important than beam gating in margin reduction. They concluded that gated beam delivery is “neglible compared to the effects of 4D-CT and respiratory correlated image guidance for most patients.” The potential reductions in field margins ranged from 17-40 percent.4
Symmetry workflow is straightforward. The patient has a planning CT scan followed by the Symmetry acquisition and reconstruction. Symmetry registration occurs automatically, after which clinicians can perform patient shifts and subsequently deliver the treatment.
Once again, it should be acknowledged that evidence collected by leading clinical partners using Elekta Synergy has contributed to the improved understanding of respiratory motion and the development of Symmetry.
Intuity—redefining image guidance
Intuity builds on XVI imaging technology to add a new level of image guidance. The key to excellence in IGRT is to understand the continuous changes in the positional relationships of both tumor and healthy tissues during the course of a patient’s treatment. This understanding brings the opportunity to manage such changes and to optimize dose placement. Intuity is the key to this breakthrough and moves IGRT technology toward even greater sophistication.
The important capabilities of Intuity are:
Critical structure avoidance: New functionality adds to the confidence of accurate tumor location, by providing assurance that changes in internal anatomy have not put adjacent critical structures at increased risk since the original treatment plan was established.
Shaped registration region of interest: A new tool to contribute to the clinical flexibility of Elekta IGRT is the ability to use a shaped registration region of interest that allows high conformance to relevant anatomy during the registration process. This means that even in complex cases, the need for manual intervention will be reduced and confidence in the results of automated registration is increased.
3D automated seed matching: Intuity brings 3D automated seed matching, which is optimized for high density implanted marker, facilitating fast, efficient registration, while still providing full 3D anatomical information.
IGRT and emerging treatment techniques
In addition to refining the automation of the integrated imaging workflow, Elekta is at the forefront of methods that dramatically increase treatment speed. Most notable is volumetric modulated arc therapy, which Elekta calls Elekta VMAT. Entering its third year of commercial availability, Elekta VMAT (which has both CE-marking and 510(k) verifications) has garnered more than 200 orders, with many customers using the arc-based technique clinically since 2008. These clinical Elekta VMAT users have employed the method on the company’s Elekta Synergy system to treat hundreds of patients worldwide. With Elekta VMAT, single or multiple radiation beams sweep in uninterrupted arc(s) around the patient, reducing treatment delivery times from the eight to 12 minutes required for standard radiation therapy to as few as two minutes. The application of a technique such as VMAT—which entails rapid, continuous changing of the beam shape, dose rate and gantry speed over 360 degrees of arc—demands the advanced imaging capabilities of IGRT. Elekta VMAT delivers the highest levels of accuracy when used with Elekta VolumeView™ 3D IGRT to help ensure accurate patient set-up; size, shape, and position of target compared to plan; and size, shape, and position of organs at risk, compared to plan.
The entire treatment strategy, from planning to delivery, can easily be controlled from a single workstation supported by an electronic medical record (EMR) and paperless workflow using the MOSAIQ® Oncology Information System.
Over ten years of research in collaboration with members of the Elekta IMRT Consortium and the Elekta Synergy Research Group led to the creation of both Elekta Synergy and Elekta VMAT.
Diverse solutions support diverse oncology department needs
While IGRT is among the most visible areas of Elekta innovation, the range of Elekta support solutions is comprehensive, and growing to meet the needs of the 21st century oncology department. Two of Elekta’s newest works in progress innovations are the Apex dynamic multileaf collimator (DMLC) and the Fraxion patient immobilization system.
Apex is a new add-on DMLC that builds on the proven technology of the 3mm, 5mm and 7mm DMLCs and provides a solution for programs to expand into stereotactic radiosurgery and stereotactic radiation therapy. Apex features 56 2.5mm leaf pairs and a generous 14cm x 12cm field size, the largest commercially available.
The Fraxion system features a unique patented vacuum mouth piece, thermoplastic mask and an invasive frame to immobilize the patient. The non-invasive carbon fiber frame will help clinicians achieve optimal accuracy and precision, which is crucial to effective intracranial fractionated stereotactic therapy.
The vision for success today and tomorrow
Image guidance using daily cone beam CT has become a clinical requirement in increasing numbers of cancer programs. Elekta’s imaging solutions combine the most powerful 2D, 3D and 4D imaging tools available with advanced workflow management and storage solutions. New tools enable clinicians to see and use even greater volumes of imaging data to guide the treatment process. Daily imaging at ultra-low doses offers clear benefits to patients, and oncology imaging solutions from Elekta are designed to extend those benefits to more cancer patients without increasing the burden of complex imaging workflows on therapists and oncologists.
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Notes
1. CORRELATION OF LUNG TUMOUR MOTION WITH EXTERNAL SURROGATE INDICATORS OF RESPIRATION. JEREMY D.P. HOISAK, KATHARINA E. SIXEL,
ROMEO TIRONA, PATRICK C.F. CHEUNG, JEAN-PHILIPPE PIGNOL. Int. J. Radiation Oncology Biol. Phys., Vol. 60, No. 4, pp. 1298–1306, 2004
2. VARIABILITY OF FOUR-DIMENSIONAL COMPUTED TOMOGRAPHY PATIENT MODELS JAN-JAKOB SONKE, PH.D., JOOS LEBESQUE, PH.D., M.D., AND
MARCEL VAN HERK, PH.D. Int. J. Radiation Oncology Biol. Phys., Vol. 70, No. 2, pp. 590–598, 2008
3. COMPARISON OF DIFFERENT STRATEGIES TO USE FOUR-DIMENSIONAL COMPUTED TOMOGRAPHY IN TREATMENT PLANNING FOR LUNG CANCER
PATIENTS. JOCHEM W. H. WOLTHAUS, M.SC., JAN-JAKOB SONKE, PH.D., MARCEL VAN HERK, PH.D., JOSE´ S. A. BELDERBOS, M.D., PH.D., MADDALENA
M. G. ROSSI, D.C.R. (R.), R.T.T., JOOS V. LEBESQUE, M.D., PH.D., AND EUGE`NE M. F. DAMEN, PH.D. Int. J. Radiation Oncology Biol. Phys., Vol. 70, No.
4, pp. 1229–1238, 2008
4. LUNG CANCER RADIOTHERAPY WITH RESPIRATORY MANAGEMENT: THE EFFECT OF BEAM GATING ON TREATMENT FIELD MARGINS IS NEGLIBLE. S.S. KORREMAN, G.F. PERSSON, D.E. NYGAARD AND C. BRINK. Int. J. Radiation Oncology Biol. Phys., Vol. 75, No. 3, Supplement 1, pp. S75, 2009.