Intensity Modulated Radiation Therapy (IMRT) is the most advanced form of external beam radiation therapy available for cancer treatment today. It delivers a high dose of radiation to well-defined cancerous tissue while avoiding the healthy tissue surrounding the tumor. The goal of this treatment is to match the intensity of the radiation beam to the density of the tumor being treated. “More simply put,” says Dr. Nisar Syed, Medical Director of Radiation Oncology at Long Beach Memorial Radiation Oncology Center, “IMRT gives clinicians the option to increase the intensity of the radiation beam in sections where the tumor is thicker, and decrease radiation beam in sections where the tumor is thinner.” IMRT allows for very precise external beam radiotherapy treatments, which are more effective than a single large radiation beam passing through the body. With IMRT, radiation field is effectively broken up into thousands of tiny radiation beams of varying weight delivered with laser accuracy; these beams enter the body from many angles and intersect on the cancerous tissue to deliver the radiation treatment.

IMRT capitalizes on several technological advances, including advanced diagnostic imaging, powerful computing and treatment-planning software that maps out a specialized individual treatment plan. A sophisticated tool called a dynamic multi-leaf collimator, which has 80 computer-controlled moveable "fingers," is used to shape the beam of radiation while controlling the intensity of the beam in any given location. With its greater precision, IMRT can be used to treat tumors that might otherwise be considered untreatable because of their proximity to vital organs and other bodily structures.

The Process
The first step a patient must make is to setup an appointment for a consultation with a physician in the Radiation Oncology Center. Prior to the consultation, the radiation oncologist will review the patient’s medical history, including any prior cancer treatments. During the consultation, a thorough examination will be performed and detailed treatment options discussed with the patient. The patient will have ample time to ask any questions pertaining to different treatment options.

Once the patient has decided on IMRT as their treatment of choice, a flurry of activity begins. The patient is first scheduled for a special CAT Scan (CT), which is performed in the Radiation Oncology’s modern CT suite. In addition to the radiation oncologist(s), a medical dosimeterist, a medical physicist, and CT simulation therapist are also present during the simulation in the CT room to assure that the correct information is collected during this critical step.

The CT images are then viewed by the team and electronically transferred to a sophisticated computer for 3D dimensional reconstruction. At this point, our dosimeterist, Kanitta Vasna, in conjunction with the radiation oncologist outlines the tumor and the normal tissues on all of the CT slices. The computer uses this information to create a 3 dimensional representation of the tumor as well as the critical normal tissues. The team can then view the shape of the tumor at any angle and see which critical tissue or organ is in danger of getting unnecessarily irradiated.

After the completion of this step, all images are sent to another powerful computer for the creation of the final IMRT treatment plan. Our senior medical physicist, Anil Sharma Ph.D., continues working on the treatment plan by assigning varying dose limits to the tumor and the critical structures. The computer program, using artificial intelligence, evaluates millions of possible beam arrangements and creates a clinically optimized treatment plan based on a few constraints set by the physicians and Dr. Sharma. This plan maximizes the radiation dose delivered to the tumor while minimizing the radiation dose delivered to the surrounding normal tissues. An example of a constraint for a tumor located around the spinal cord would be to have a maximum of 10% of the total radiation delivered to the spinal cord while the tumor receiving 100% of the dose. Quite simply, this means that the entire tumor will receive a maximum amount of radiation while the healthy spinal cord, surrounded by cancer, will receive only a small amount of radiation.

The Implementation of IMRT at Long Beach Memorial Hospital
The physicians, physicists and management of our Radiation Oncology Center had the foresight to recognize the potential medical benefits of IMRT about 5 years ago. They began mapping out a capital purchasing and training schedule for the successful implementation of an IMRT program at that time. To do this, staff teamed up with industry leader and long-term business partner, Varian Medical Systems of Palo Alto, California. The initial estimate of the cost was around 2.5 million dollars. Because of the complexity and the cost of the project, we devised a 4-year capital purchase plan and implementation schedule. During the first year of the plan, we upgraded our existing 2100C linear accelerator with a Multi-Leaf Collimator system. The installation of this device allowed for complex conformal radiation treatments by creating radiation portals matching the shape of tumors. It also reduced the need for manufacturing individualized radiation beam shaping devices for each patient. These devices, made from low-melting metal alloys, were heavy to lift and had to be placed between the head of the linear accelerator and the patient for each radiation beam.

The following year we purchased a new radiation treatment planning system optimized for IMRT. This program uses a very advanced computing methodology (Inverse Planning) by incorporating artificial intelligence to develop individualized radiation treatment plans. We also purchased a device called a Water Phantom, which is used for the precise measurement of radiation coming out of a linear accelerator. A Water Phantom is an absolutely necessary piece of equipment designed to collect detailed information about the physical characteristics of the radiation beams used for IMRT. Throughout that year, Varian Medical Systems upgraded our multi-leaf collimator and licensed our institution for IMRT treatments at no additional cost to the Medical Center.

The next two years were spent constructing a new CT room for installation of our modern CT machine, manufactured by Picker. Picker has packaged a high quality CT machine to include a powerful computer system and state-of-the-art image processing software that replaces the x-ray based radiation therapy simulator. This CT-based simulator allowed the clinician to view tumors in three dimensions by reconstruction the patient’s body in the computer’s memory from CT slices. This system also reduced the simulation time for patients from one hour to only 30 minutes, thus improving the comfort level of the patient.

The last piece of the puzzle fell into place with the purchase of a Varis Radiation Oncology Information System, also known as a Record and Verify System. This system is required for the delivery of IMRT, as these treatments are too complex for manual operation. During a conventional radiation treatment, a radiation therapy technologist may deliver up to six beams of radiation from six different angles targeting the center of the tumor. In contrast, a typical IMRT treatment may employee up 3000 tiny pencil-thin beams or “beamlets” each with a different intensity. Only a combination of a powerful computer with a sophisticated radiation delivery system can control these processes and keep record of them. Our medical physicists and dosimetrist enter each patient’s treatment parameters into Varis for accurate treatment delivery.

Varis uses two computer servers in its current configuration to support one of our two linear accelerators. These servers are placed in the Data Center, located in the basement of the professional building. They are connected by the radiology network to the 2100C Varian linear accelerator, Picker CT, and AcQSim Virtual Simulation workstation. They are also connected to a host of treatment planning systems all developed by Varian Medical Systems (Cadplan Plus, Helios inverse treatment planning system, Soma Vision, High Dose Rate brachytherapy treatment planning system and Eclipse treatment planning system). In its final configuration, Varis will employ one more computer server and will connect to our second linear accelerator, digital radiation portal imaging devices, digital film printers and High Dose Rate Remote After loader machine. It will manage and store all medical images generated by our department. Additionally, it will connect to the Hospital’s PACS System (Picture Archiving and Communications Systems) to retrieve diagnostic images stored in digital format generated by CT, MRI, PET, Ultrasound and x-rays for comparative studies and treatment planning purposes.

The implementation of IMRT at LBMMC has not only been a great technical achievement, it has been financial success as well. We treated our first IMRT patient in March of 2002 and until October 2002 have treated more than 50 patients using this advanced technology. Medicare published fee schedule for IMRT daily treatments reimbursements are four times more than conventional radiation treatment. By dividing the project into multiple years however, we are able to spread the costs over four to five years. Each step of the project has its own specific clinical and financial goals that contribute to our overall goal of bringing this very advanced radiation treatment to our community. IMRT is an innovative approach to cancer treatment. Like other new treatment procedures, it will be further refined in the future, and may even be used outside of oncology field.