How does Intensity Modulated Radiation Therapy (IMRT) differ from robotic radiosurgery and the CyberKnife System?

IMRT, Intensity Modulated Radiation Therapy, is a form of radiation therapy incorporating multi-leaf collimators on standard gantry-based linac delivery systems to better "shape" the radiation beams to the lesion volume. IMRT also utilizes inverse treatment planning software to optimize dose distribution. This is generally accepted as an improvement over conventional radiation therapy (XRT) systems; however it is still limited by many of the same constraints as conventional radiation therapy. IMRT differs from CyberKnife radiosurgery in several fundamental ways: • Accuracy — IMRT systems register target location only at the beginning of a treatment and cannot localize and compensate for a moving target during the actual treatment. The CyberKnife System combines image guidance and computer controlled robotics to continuously track, detect and correct for tumor and patient movement throughout the treatment, providing greater accuracy when compared to an IMRT system. • Fractionation — ...  more