Large-Bore CT System Developed for Radiation Therapy

A new computed tomography (CT) system was specially developed for use in radiation therapy and allows more precision in therapy planning and cancer treatment—particularly under difficult situations, such as obese patients and artifacts from metal implants and tumor motion. Moreover, the technology is the first to exploit the benefits of dual-energy CT for radiation therapy.

At the Second Forum of the European Society for Therapeutic Radiology and Oncology (ESTRO) held April 19-23, 2013, in Geneva, Switzerland, Siemens Healthcare (Erlangen, Germany) presented the new RT Pro edition of the Somatom Definition AS Open 20/64 large-bore CT system.

With the RT Pro edition—as well as the other imaging radiotherapy systems exhibited in Geneva—and as part of the company’s Agenda 2013 sector initiative, Siemens and Varian Medical Systems also introduced new software interfaces that incorporate Siemens’ Primus and Oncor linear accelerators with Varian’s (Palo Alto, CA, USA) Aria oncology information system, the first outcome of the joint development work within the framework of the strategic partnership between the two companies.

Radiation therapy requires high-quality diagnostic images for exact treatment planning and thus for the successful treatment of cancer. This involves more than only identifying the exact location of the tumor. To precisely compute the radiation dose for radiation therapy, it must be possible to see the outer contours of the patient even when they lie outside the normal scan field of view (FoV), e.g., in the instance of obese patients. The HD FoV Pro functionality of the Somatom Definition AS Open-RT Pro edition system uses sophisticated algorithms to intelligently calculate body contours and tissue attenuation outside the normal scan field. The outcome is an improved, geometrically correct depiction of the body contours and a consistent image of tissue density inside and outside the FoV. This provides radiation therapy staff with informative images for planning treatment even in the case of obese patients.

For the many patients with metal implants, i.e., dental fillings, artificial hips, and pacemakers, artifacts appear in the clinical images and this interferes with the visualization of tumors and surrounding organs. With the help of the Maris (metal artifact reduction in image space) functionality, these artifacts are decreased, thereby enhancing the localization and contouring of tissue structures and streamlining the treatment planning process.

Breathing normally changes the position of the tissue structures to be treated, making it more difficult to define the volume of the tumor to be irradiated and to protect the surrounding healthy tissues. With the Motion Management Pro module of Somatom Definition AS Open-RT Pro edition, Siemens provides a thorough tool for analyzing tumor motion during the breathing cycle. For example, when planning treatment for lung cancer, this makes possible to irradiate the correct target volume, at the right time within the breathing cycle, and with the precise dose.

With the RT Pro edition, Siemens is also making the benefits of dual-energy CT imaging available to CT systems with the extra-large 80-cm gantry. Dual-energy CT imaging performs two sequential spiral scans at different energy levels and then merges them in a single dataset during postprocessing. The dual-energy images can be utilized to reduce metal artifacts or accurately evaluate tissue density, and therefore to calculate the optimal dose.

Siemens plans to deliver new RT Pro edition systems at the end of April 2013. An upgrade for the installed base will be available as of mid-May 2013.

As part of their worldwide partnership in radiotherapy and radio surgery, Varian Medical Systems and Siemens Healthcare have jointly developed software interfaces that connect the Siemens linear accelerator (Linac) with Varian’s Aria oncology information system. This enables users of Siemens Linacs Primus and Oncor to connect their systems to Aria, thereby giving them the option to transition to this modern and feature-rich OIS when it is time to update equipment in the department.

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