Radiation Oncology

The Department of Radiation Oncology offers a full range of radiation services.

IMRT (Intensity Modulated Radiation Therapy)

Intensity modulated radiation therapy (IMRT) is a major advancement in cancer treatment. IMRT makes use of a computer program which evaluates millions of possible beam arrangements and produces a clinically optimized plan that is then reviewed by a team of physicians and physicists to determine the final treatment plan. An IMRT treatment plan may consist of a hundred tiny beamlets to "paint" a target with higher radiation doses while sparing nearby healthy organs significantly more than traditional radiation therapy. This breakthrough technology enables the focusing of higher doses of cancer-killing x-rays on tumors while sparing surrounding healthy tissue. Clinical studies indicate that IMRT techniques make it possible to use higher dose levels and result in fewer short- and long-term side effects.

IMRT at Torrance Memorial Medical Center is distinctive for a number of reasons:

Ensured high quality:
Torrance Memorial uses Impac Software. This guarantees optimal quality patient care by constantly checking and documenting the delivered treatment angles. Physicians can confirm that the dose planned equals the dose given.

Specialized imaging of the target:
At Torrance Memorial, we are able to use the expertise and high quality of our radiology department to generate precise imaging of the tumor and surrounding normal tissues. We are able to superimpose different sets of images such as CT, MRI and PET scanning, and "fuse" these images in our radiation planning system to give the highest definition of the target.

Larger treatment area:
Other types of IMRT accelerators have smaller field sizes or windows through which to direct the radiation beam. This requires that the tumor be treated with a combination of IMRT and conventional therapy to cover the entire tumor. Because our maximum available field height is much larger (40 centimeters), we are able to deliver the entire treatment with IMRT technology.

Accurate localization of the target:
Some radiation targets can vary significantly from one day's treatment to the next. For example, the prostate gland can move at least 1/2 inch in various directions within the pelvis, because of differences in rectal and bladder filling. Normally with external beam irradiation, marks on the body are used to center the patient in the radiation field. However, the prostate gland may not be centered because of its motion within the body! This problem is solved by using a system of implanted gold seeds to find the prostate gland. Our IMRT process for prostate treatment includes daily localization of the prostate using these markers. The result is better accuracy in targeting the prostate and avoiding the rectum and bladder.

A team approach:
Torrance Memorial relies on a specially trained team for IMRT delivery. This team includes the radiation oncologist, medical radiation physicist, dosimetrist, radiation therapist, and radiation therapy nurse. The radiation oncologist, a specially trained physician who heads the treatment team, sets an individualized course of treatment with the help of the radiation physicist, who ensures the linear accelerator delivers the precise radiation dose and that computerized dose calculations are accurate. A dosimetrist works with the medical radiation physicist to calculate the IMRT fields and beam configurations necessary to deliver the dose prescribed by the radiation oncologist. A highly trained radiation therapist positions the patient on the treatment table and operates the machine. The radiation therapy nurse provides the patient with individualized teaching about the treatment and possible adverse reactions. The physician and the nurse provide supportive care throughout the course of treatment and its followup.

This picture shows the highly modulated radiation doses we can deliver to the prostate gland with IMRT. The prostate gland is the central structure, outlined by the inner red circle. You can see two tiny gold markers towards the middle of the prostate (they look white on this CT image). The bladder is the oval structure above the prostate, outlined in blue. The rectum is the tube-like structure behind the prostate, outlined in green. The series of colored circles around the prostate are called "isodose" lines. They show the very tight conformation of dose around the prostate, and the steep drop-off of dose to the bladder and rectum. The various dose levels are shown in the legend to the right. We know that the risk of long-term side effects in the bladder and bowel is much lower if we can minimize the dose to those organs.

ACCULOC image-guided patient localization system

The higher doses and tighter margins associated with IMRT require highly accurate tumor localization. ACCULOC -- an image-guided patient localization system-provides this type of high-precision localization for every IMRT dose delivered. The system uses implanted fiducial technology (tiny gold markers) to provide submillimeter localization accuracy for IMRT. The target location is registered with the treatment beam for precise dose delivery. ISOLOC software accounts for rotation using a 3D algorithm. The detailed images provided by our amorphous silicon portal imaging system on the treatment couch afford daily, real-time, image-guided setup by providing precise moves of the treatment couch to achieve exact target alignment.

3-D Conformal Radiation Therapy

3-D conformal radiation therapy utilizes CT based treatment planning with three dimensional rendering of the tumor volume and normal structures. This allows for very precise delivery of radiation doses and better avoidance of normal tissues. This technique has been well applied to localized tumors such as prostate cancer limited to the prostate gland. It can also be used to treat other localized cancers.

Our 3-dimensional treatment planning is performed with the XiO system by Computerized Medical Systems, Inc. CT images from the medical center's CT scanners are electronically transferred to the treatment planning computer in the Radiation Oncology department. Both conventional and CT-simulation techniques may be used. The physicians have the ability to review and approve treatment plans using the FocalVue application. This allows visualization of the radiation dose from many angles. To better delineate the tumor volume and normal structures, the FocalFusion option is available, which allows a patient's CT, MR and PET images to be merged. The treatment planning software allows full use of the linear accelerator's multileaf collimators for conformal beams. Treatment plan parameters are then downloaded into the IMPAC Record-and-Verify system for accurate dose delivery.

Conventional External Beam Radiation Therapy

Conventional external beam radiation therapy utilizes a medical linear accelerator to deliver radiation treatments to somewhat larger treatment areas. CT based treatment planning is frequently used and every effort is made to exclude as much of the normal tissues from the treatment area. Verification or "port films" are taken to assure proper setup.

Intracavitary Therapy

Intracavitary therapy is a form of internal radiation therapy. It is often used for cervical or uterine cancer. It involves the placement of a special intrauterine or intravaginal applicator under anesthesia. This applicator then holds the radiation sources for delivering treatment. This type of internal treatment allows the placement of the radiation close to the tumor so that higher doses of radiation can be given.

Interstitial Therapy

Interstitial therapy is another form of internal radiation therapy. It involves the placement of radioactive sources (seeds) directly into involved tissues. Interstitial therapy has been successfully used to treat prostate cancer and other cancers. We have used prostate seed implants at Torrance Memorial Medical Center for over eight years.

---

EQUIPMENT

Clinac 2100 C

The Clinac 2100 C is capable of generating both high and low energy x-ray beams as well as a range of electron energies. This allows for versatility in treating both deep and more shallow tumors. It is equipped with a multileaf collimator which allows for exact beam shaping. It is fully computer integrated with numerous precision and safety monitoring features.

Clinac 6-100 EX

The Clinac 6-100 EX generates 6 MeV x-rays which are ideal for many types of cancer treatments such as breast cancer and head and neck cancers. It is equipped with a multileaf collimator to allow for precise beam shaping. The "portal vision" feature allows for immediate digital verification imaging to check field placement. It is fully computer integrated.

Portal Vision

Both linear accelerators are equipped with Portal Vision which allow for on-line radiographic imaging of the treatment area. This allows for verification of the treatment area and accurate daily set ups.

Ximatron Simulator

The Varian Ximatron Simulator assists in the set up and placement of radiation field arrangements for accurate and reproducible treatment planning.

IMPAC Record and Verify System

The radiation treatments are monitored and recorded by the IMPAC "record-and-verify" computer system. The system has safety interlocks that assist the radiation therapists in delivering the treatments safely and accurately.

Medtec Exact Top Treatment Tables

Both linear accelerators and the Ximatron simulator are fitted with Exact Top treatment tables. These are high strength carbon fiber treatment tables with special locking features to secure immobilization devices. This allows for immobilizaton of the treatment area and improves the accuracy of set up and day to day treatment.