ABSTRACT
PURPOSE: To describe the design and performance of a novel frameless system for radiosurgery. This technology, called image-guided radiosurgery (IGR), eliminates the need for stereotactic frame fixation by relating the identified lesion to radiographic landmarks. CONCEPT: IGR uses a lightweight x-band linear accelerator, computer-controlled robotic arm (Fanuc manipulator [Fanuc Robotics North America, Inc., Rochester Hills, MI]), paired orthogonal x-ray imagers, and a computer workstation that performs rapid image-to-image registration. During radiosurgery, the x-ray imaging system determines the location of the lesion and communicates these coordinates to the robot, which adjusts the pointing of the linear accelerator beam to maintain alignment with the target. RATIONALE: Existing stereotactic techniques require rigid cranial fixation to establish and maintain a system of reference for targeting. Such frames cause pain for the patient, limit the use of fractionation, and necessitate a prolonged period of general anesthesia if children are to be treated. Furthermore, skeletal or any other type of rigid fixation is difficult to achieve beyond the cranium. IGR was designed to overcome these limitations, which are inherent to nearly all current radiosurgical methods. DISCUSSION: Preliminary testing and early clinical experience have demonstrated the practicality and potential of the IGR concept and have identified the most important directions for improvement. For example, an IGR prototype accurately tracked target displacements in three dimensions but showed reduced accuracy when confronted by rotational movements. This observation led to development of a new generation of tracking algorithm that promises to improve tracking in all six dimensions. Further experience indicated that improvements in the quality of the x-ray images were needed to allow the system to locate and treat target sites outside the cranium. Consequently, a new x-ray imaging technology with superior resolution and increased sensitivity has been added to the system. These improvements should make it possible to apply IGR techniques to a variety of targets located throughout the body. This article describes and critiques the components of the IGR and summarizes our preliminary clinical experience.
ABSTRACT
The majority of newly diagnosed patients are expected to survive Hodgkin's disease because of effective therapies established during past 30 years. Long-term observations from large populations of treated patients have disclosed a variety of late effects of the disease and its therapy have contributed morbidity and excess mortality to Hodgkin's disease survivors. Secondary cancers have continued to accrue, and the risk relative to the general population has increased to 6.4 (95% confidence intervals: 5.5 to 7.3) in updated experience at Stanford University. Risks are significantly elevated for leukemia (primarily after chemotherapy regimens containing alkylating agents); non-Hodgkin's lymphoma; and tumors of the lung, breast, soft tissues, bone, stomach, pancreas, salivary gland, thyroid, and cutaneous melanoma. Early cardiovascular disease has also been observed and numerically exceeds second cancers as a cause of death in patients with early stage Hodgkin's disease (49 v 47 cases). Pulmonary dysfunction, thyroid dysfunction, infertility, psychosocial changes, gastrointestinal problems, soft-tissue changes, alterations in immunity, and risks for infection have also affected some treated patients. As these problems have been recognized, treatment approaches have been modified over the last 10 to 15 years, and early data suggest a decrease in some treatment sequellae.
