Co-60 tomotherapy: A treatment planning investigation
Custom profiles created for the 2 cm (solid) and 2.8 cm (dashed) diameter cylindrical sources.
Scaled version of the MLC and source configuration used to make the profile measurements in Sec. II A. Note that for points away from the beam centerline, a decreasing amount of the source is seen from the profile plane because of the narrowing gap formed by the top and bottom of the MLC leaf opening.
The calculated (dashed) and measured (solid) profiles for one and four, 0.625 cm wide MLC leaf openings.
The calculated profiles for a 1 cm MLC leaf opening using the Gaussian source modeling parameter in PINNACLE (dashed lines) and custom source profiles (solid lines). Gaussian standard deviation values were chosen to provide the same FWHM as the custom source profiles (0.68 and 0.97 cm for the 2.0 and 2.8 cm diameter sources, respectively).
Profiles for sequential and simultaneous leaf openings with the 2.0 cm Co-60 source. In each figure the fine black lines represent adjacent single leaf openings and the heavier black line the profile are obtained by superimposing the adjacent single leaf opening profiles. The gray lines are measured profiles for leaves opened simultaneously and the dashed black lines are the sequential leaf profiles multiplied by the factor given in the legend.
Grayscale images depicting the thread effect simulated in PINNACLE with a 30 cm diameter cylindrical phantom and open fan beams of 4.8 cm slice width and a pitch of 0.5. Each beam has the same Co-60 beam parameters except the source size increases from 0.1 cm FWHM in (a) to 2.0 cm and 2.8 cm diameter cylindrical sources in (b) and (c), respectively. Dual-slice delivery with the 2.0 cm diameter source is shown in (d).
Prostate patient DVH results for the segmental IMRT plan (solid lines) and Co-60 tomotherapy plan with a 2.0 cm diameter source (dashed lines).
H&N patient DVH results for the segmental IMRT plan (solid lines) and Co-60 tomotherapy with a 2.0 cm diameter source (dashed lines).
Brain patient DVH results for the segmental IMRT plan (solid lines) and Co-60 tomotherapy with a 2.0 cm diameter source (dashed lines).
Brain patient DVH results for the Co-60 tomotherapy plan with a 2.0 cm diameter source (solid lines) and a 2.8 cm diameter source (dashed lines).
Treatment times for the three clinical cases planned delivered with segmental IMRT and Co-60 tomotherapy with 2.0 cm cylindrical source. Dual-slice treatment times are also estimated for the 2.0 cm diameter source.
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