Molecular Imaging Insight - May 2008 - (Page 18) [ Lung Cancer: Primary tumor in left lung with deposit in contralateral lung attached to chest wall. PET/CT performed on Siemens Biograph 40 for metastatic evaluation and RT planning. TrueD visualization of FDG PET/CT datasets with region of interest (ROI) drawn on FDG avid tumor in right lung adjacent to chest wall. Note central hypointensity of FDG uptake within tumor suggesting tumor necrosis. 3D volume ROI drawn on TrueD incorporates FDG avid tumor and excluded necrotic tissue. ROI saved as DICOM RT Structure sets for export to Radiation Treatment Planning system for simulation. Courtesy of MD Anderson Cancer Center, Orlando, Fla. ] that manages integration of the various scanners and workstations, and a sound working partnership with Siemens. The hospital also focused on training technical staff, so technologists understood how to acquire hybrid images for radiation therapy. Transforming treatment MD Anderson Cancer Center at Orlando Regional Healthcare in Orlando, Fla., is a multidisciplinary cancer care center committed to leading-edge treatment and superior patient care. The site installed a Siemens Medical Solutions Biograph 64 TruePoint PET/ CT scanner a year ago, and since then it has revamped its protocols for treatment of a number of cancers including early and stage three lung cancers and esophageal cancers. “Siemens Biograph 64 TruePoint PET•CT has dramatically changed the way we treat patients,” says Alan R. Forbes, MD, PhD, radiation section leader for thoracic/ head and neck and lymphoma/myeloma specialty sections. It’s difficult to balance the equation for effective radiation therapy of lung nodules. “The problem in treating lung cancer,” says Forbes, “is that the lung’s tolerance to radiation is low, but tumor requirements are high.” For example, in conventional arrangements, a tumor might require a 70 Gy dose, while the lung’s radiation tolerance is 15 Gy. “We’ve seen excellent advances in early stage lung cancer,” says Forbes. The new regimen calls for a four-day cycle of ablative radiation therapy; the very high cauterizing radiation dose destroys everything at the center of the beam. Results hover close to lobectomy, making the treatment a good option for borderline and nonsurgical candidates; however, there are downsides to ablative treatment. “There is no normal tissue sparing. If we were to hit a bronchus with the beam, it’s likely that it would be destroyed, which closes off the lung supplied by that bronchus. We have to be very accurate; volume and positioning are critical,” explains Forbes. The new protocol centers on the Biograph 64 TruePoint PET•CT. The team places fiducial markers in the lung and gates the tumor’s position to the respiratory cycle. The ability to gate the tumor is essential, enabling the team to narrow the beam and focus treatment on the nodule while avoiding the surrounding volume throughout the treatment. Consider as an example a typical early stage patient with a 1 cm nodule. The tumor might move 4 cm during respiration. With conventional imaging and planning, the radiation therapy team includes respiratory motion in the treatment volume to ensure a full dose reaches the tumor. Respiratory gating allows the team to trim the treatment volume and minimize the dose to normal tissue. “Biograph 64 TruePoint PET•CT provides an ideal imaging platform. 4D CT provides a crisp, clear view of the nodule and its movement during the respiratory cycle. The scanner makes it possible to offer ablative radiation therapy as a treatment option for many early stage lung cancer patients,” says Forbes. MolecularImaging.net PET and Cyclotron Unit and Department of Radiotherapy. Today, the hospital uses whole-body PET/CT as the standard of care for radiation therapy planning for head and neck, cervical, lymphoma and lung patients. In addition, the approach drives more precise treatment. “Before we implemented PET/CT for radiotherapy planning, we used RECIST criteria for malignant lymph nodes, which is 1 cm. Now, we include all PET positive lymph nodes in the radiation field despite their size,” explains Berthelsen. syngo TrueD software streamlines the treatment planning process by allowing users to fuse and compare PET/CT images. TrueD automates processes, so physicians can monitor functional and anatomical changes and adjust treatment as needed. “Although we have two PET/CT scanners and a dedicated PET scanner, we use Siemens Biograph 16 exclusively for radiation therapy planning because tumor delineation on the syngo workstation with TrueD software is very precise,” explains Berthelsen. State-of-the-art imaging equipment is only part of the equation for a successful PET/CT program in radiation oncology. Copenhagen University Hospital employs a collaborative approach that optimizes the expertise of multiple specialties. Nuclear medicine physicians tackle tumor delineation on the PET part of the hybrid scan. Next, CT images including the tumor delineation regions are sent from TrueD to the Varian Medical Systems Eclipse workstation, where radiation oncologists and radiologists partners to delineate margins on CT images. The process becomes slightly more complex with head and neck cases as PET/CT studies are fused with MRI results to create a more comprehensive picture of the disease and normal anatomy. Berthelsen credits the success of the program to close proximity of the PET/CT scanner and radiation therapy department. “Everyone and everything we need are in the same two departments, making it easy to coordinate among radiation oncologists, radiologists and nuclear medicine physicians,” Berthelsen says. Other factors in the success of the program include a dedicated IT staff 18 Molecular Imaging Insight | May 2008 http://MolecularImaging.net
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