Feasibility of gated IMRT

T. D. Solberg, T. J. Paul, R. A. Boone, N. N. Agazaryan, T. Urmanita, A. R. Arellano, J. Llacer, R. Fogg, J. J. DeMarco, J. B. Smathers

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Scopus citations


Recent years have seen the development of sophisticated delivery technologies designed to enhance the efficacy of clinical radiotherapy. In this study we evaluate the feasibility for combining two pivotal concepts, intensity modulated radiotherapy and respiratory gating, into a single effective therapeutic modality. Respiration is monitored in real-time through the use of cameras which track infrared-reflecting markers placed on the patient's surface. With a sampling rate of 5 Hz, normal breathing produces a simple sinusoidal pattern in three spatial dimensions. A software interface enables gating about exhalation. Radiation is delivered using a Novalis™ accelerator and integrated micro-multileaf collimator. The unit is capable of dynamic field shaping and IMRT. Other features making the Novalis ideally suited to gated IMRT include: high output (1200 mu/min) and the ability to start / stop the beam within 0.01 monitor unit. Beam triggering is facilitated through a clinical gating interface provided by the linac manufacturer. To evaluate the performance of the system, dose measurements were performed for dynamically wedged and IMRT fields. Gating frequency was varied from 0.2 to 1.0 Hz and monitor units were varied from 25 to 200. In this manner gating effects could be studied for a wide range of leaf speeds. Two-dimensional dose maps were obtained using an amorphous-silicon detector. Differences relative to gating frequency were observed only for low numbers of monitor units. Above 50 monitor units no variation exceeded 3.5%. In all cases, variations averaged over the entire field were less than 3.5% and less than 1% above 50 monitor units.

Original languageEnglish (US)
Title of host publicationAnnual International Conference of the IEEE Engineering in Medicine and Biology - Proceedings
EditorsJ.D. Enderle
Number of pages3
StatePublished - 2000
Event22nd Annual International Conference of the IEEE Engineering in Medicine and Biology Society - Chicago, IL, United States
Duration: Jul 23 2000Jul 28 2000


Other22nd Annual International Conference of the IEEE Engineering in Medicine and Biology Society
Country/TerritoryUnited States
CityChicago, IL

ASJC Scopus subject areas

  • Bioengineering


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