Abstract
AbstractBackgroundRecent investigations demonstrate a strong potential for cobalt-60 (Co-60)-based teletherapy. The influence of the lower energy and penetration of a cobalt-60 beam compared with linear accelerator beams is negligible for intensity-modulated radiotherapy.PurposeThe aim of this research is to investigate source head fluence modulation in cobalt-60 teletherapy by using a three-dimensional (3D) physical compensator and secondary collimator jaw motion.Materials and methodsThe Oncentra treatment planning system was used to develop three hypothetical plans by secondary collimator jaw motion. A clinical MDS Nordion Equinox 80 cobalt-60 teletherapy unit was used to acquire conventional water phantom beam characteristics. Fluence modulation experiments were executed at 5·0 cm depth in a PTW universal intensity-modulated radiation therapy (IMRT) verification phantom using calibrated Gafchromic external beam therapy 2 (EBT2) and RTQA2-1010 film batches. Gafchromic EBT2 film was used to sample intensity maps generated by secondary collimator jaw motion, yet Gafchromic RTQA2-1010 film sampled maps from the 3D physical compensator. The solid-state drives used were 75·0 and 74·3 cm for the Gafchromic EBT2 and Gafchromic RTQA2-1010 film measurements.ResultsA 2D gamma index analysis was coded to compare EBT2 film measurements with Digital Imaging and Communications in Medicine data. This analysis was also used to verify film measurements versus Monte-Carlo simulations.ConclusionLateral beam profiles generated from water phantom measurements were used to establish source head fluence modulation on the film measurements. The source head fluence of a cobalt-60 teletherapy beam could be modulated by secondary collimator jaw motion and using a 3D physical compensator.
Highlights
IntroductionCobalt-60 teletherapy units and linear accelerator systems (linacs) were introduced nearly simultaneously in the early 1950s and emerged as rival technologies for external beam therapyThe potential of Co-60 teletherapy in advanced radiation oncology mode with Monte-Carlo (MC) dose planning and verification has not been probed for the past few decades, even though it may offer similar advantages as linear accelerators. A few advanced radiation treatment planning studies have been done for Co-60 teletherapy, this modality involves a high-energy photon beam. Intensity-modulated radiation therapy (IMRT) with Co-60 teletherapy can be suitable for complex superficial anatomic sites, and it can minimise the incidence of radiation toxicity in proximal organ at risk volume. Integrating technologies like multileaf collimator in Co-60 teletherapy units can facilitate automated treatment. It is important for medical physicists to consider the role of Co-60 teletherapy in advanced technologies like intensity-modulated radiation therapy (IMRT). Co-607 based radiation therapy continues to play a significant role in developing countries where access to radiation therapy is extremely limited and in industrialised countries
Intensity-modulated radiation therapy (IMRT) with Co-60 teletherapy9,10 can be suitable for complex superficial anatomic sites, and it can minimise the incidence of radiation toxicity in proximal organ at risk volume
Preferential modulated source head fluences were achieved by sequences of square and rectangular field segments that were symmetric about the axial and sagittal planes
Summary
Cobalt-60 teletherapy units and linear accelerator systems (linacs) were introduced nearly simultaneously in the early 1950s and emerged as rival technologies for external beam therapyThe potential of Co-60 teletherapy in advanced radiation oncology mode with Monte-Carlo (MC) dose planning and verification has not been probed for the past few decades, even though it may offer similar advantages as linear accelerators. A few advanced radiation treatment planning studies have been done for Co-60 teletherapy, this modality involves a high-energy photon beam. Intensity-modulated radiation therapy (IMRT) with Co-60 teletherapy can be suitable for complex superficial anatomic sites, and it can minimise the incidence of radiation toxicity in proximal organ at risk volume. Integrating technologies like multileaf collimator in Co-60 teletherapy units can facilitate automated treatment. It is important for medical physicists to consider the role of Co-60 teletherapy in advanced technologies like IMRT. Co-607 based radiation therapy continues to play a significant role in developing countries where access to radiation therapy is extremely limited and in industrialised countries.. Purpose: The aim of this research is to investigate source head fluence modulation in cobalt teletherapy by using a three-dimensional (3D) physical compensator and secondary collimator jaw motion. Fluence modulation experiments were executed at 5·0 cm depth in a PTW universal intensity-modulated radiation therapy (IMRT) verification phantom using calibrated Gafchromic external beam therapy 2 (EBT2) and RTQA2-1010 film batches. Gafchromic EBT2 film was used to sample intensity maps generated by secondary collimator jaw motion, yet Gafchromic RTQA2-1010 film sampled maps from the 3D physical compensator. Results: A 2D gamma index analysis was coded to compare EBT2 film measurements with Digital Imaging and Communications in Medicine data This analysis was used to verify film measurements versus Monte-Carlo simulations. The source head fluence of a cobalt-60 teletherapy beam could be modulated by secondary collimator jaw motion and using a 3D physical compensator
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