Emission-guided radiation therapy: biologic targeting and adaptive treatment.

a i r m i P s s h d he past decade has witnessed sigificant growth in applications of tereotactic body radiation therapy SBRT), which involves delivering umoricidal doses of radiation in as ew as 1 to 5 fractions to tumors in he head and neck, lung, liver, panreas, spine, and prostate, with very igh (80%-98%) local control rates eported in a variety of studies. The ncrease in SBRT procedures can be argely attributed to the advent of n-board localization technologies hat include single and stereoscoic x-ray imaging, kilovoltage and egavoltage CT imaging, implantble fiducial transponders, ultraound imaging, and others. Onoard MRI radiotherapy systems re also emerging so that the covted soft tissue contrast of MRI ay be exploited for localization. n addition to target localization, n-board MRI has the potential to ore accurately estimate the dose elivered to sensitive organs during ach treatment. Stereotactic body radiation therpy requires precise localization beause of the very high doses (6-30 y) delivered for each fraction. merican Association of Physicists n Medicine Task Group 101 reently published a report on its recmmendations for SBRT practice 1]. In this report, it was emphaized that SBRT “requires a high evel of confidence in the accuracy f the entire treatment delivery proess.” Therefore, it is essential to