Transcript
Good afternoon. My mouth is so tired and rambling because of today's brain jogging, are you okay? Yes, good. My presentation is starting. What do you use? How do you use? Thanks. Thank you for chairman. Imaging Couch Top for Novalis is, needless to say, the using for robotic 6D correction system. Exact couch base and Imaging Couch Top unit control each translation shifts and correction angles, respectively. And from several investigators, X-rays attenuation was occurred by solid carbon-based fixation tools. I think there are two methods for correction to attenuation. At first, simulation-based correction, that is, corrected by RTPs with virtual couch function. Latest version of RTPs Novalis, that is i-plan version 4 is available to this correction method. Unfortunately, this i-plan version 4 is not commercially available in Japan. And second, dosimetry-based correction, that is, corrected by multiplication of correction factor. For example, specific QA-based correction factor. The next.
The background and purpose of this study. Imaging Couch Top was developed by medical intelligence corporation and used to Novalis Body system to correct each setup angle error. And Couch Top of our Novalis unit replaced from Exact Couch Top to Imaging Couch Top last year, and without changing the RTPs. ICT provides easy patient setup, but also significantly beam attenuation when beam passes through ICT. We evaluated megavoltage photon beam attenuation of ICT was evaluated and compared with ECT and other fixation tools. This slide shows materials and devices for in this study. Okay, for evaluation elements in this study, at first, effect of x-ray attenuation by passing ICT. Details are comparison between ECT and ICT. And two, compared to output factor.
And second, projection angle dependency was evaluated. And details are X-ray attenuation in each gantry angles, and compared to the fixation tools and ECT and ICT. And compared to assuming formula. Next. As a method of effect of X-ray attenuation by passing ICT slide shown here. Water equivalent phantom was put on the couch and six million X-ray delivered from floor to ceiling. Details of setting of this experiment as it's shown here. And the measurement was done in three situations. That is, the projection to a solid area of ECT, that is pattern A. And projection to mesh area of ECT, that is, pattern B. Projection to Imaging Couch Top is pattern C. And the Method 2, the projection angle dependency was evaluated. The chamber was fixed in center holder of water equivalent phantom. This shape was a sphere type. That phantom's diameter was 16 centimeter.
The measurement was performed on five situations. That is using Head-ring system and Type-S system and phantom on Exact Couch of center and with consider that side slider open and closed consideration. And without side slider open and closed consideration. And phantom Imaging Couch Top. This is assuming formula. This is the schematic view of Exam 2. The structure of ICT makes by homogeneous carbon such as thickness "t". And beam intensity on 8-centimeter depth without passing ICT and with passing ICT from gantry angle theta, were defined I zero and I theta respectively. So, I think the beam intensity and correction factor was defined here. And relationship alpha and theta and gantry angle were this. So, I think the assuming formula is defined this, correction factor equals this formula. This is the result of comparison of X-ray attenuation. Pink line is exact couch mesh type. And yellow line is projection to Imaging Couch Top. And blue line is projection to carbon area of ECT.
These results means Exact Couch Top of mesh area is hardly reduce the obtained charged dose. And similar value was appeared in ICT and the pattern A at Exact Couch Top percent. And Result 2. This slide shows the comparison between output factor and X-ray attenuation in using ICT. So, this slide shows significantly value reducing compared to water data. This value is meaning relative dose to this. This means in field size. And Result 3, the dependence of gantry angle for attenuation effect. This slide shows a 10 by 10 field size and 8 by 8 field size. Look at 120 degree and 240 degree, this areas shows the significantly value reduce in Imaging Couch Top values. This tendency appeared in each situations. That is, 10 by 10, and 8 by 8, and 6 by 6, and 4.2 by 4.2. This tendency was in same conditions. So, this is as result of comparison of correction factor. The pink line shows a measured value. And blue line shows assuming formula values. This fit to 150 to 180, so fitted.
This is highlight of results. The attenuation of photon beam by couch existed. Significant increase in beam attenuation as angle of incidence increases, ranging from 3.9% at 180 degrees to 7.2% at 120 degrees. An assuming formula fit to measurement value ranging from 150 to 180 degrees. So, discussions. Comparison of attenuation effect between ECT and ICTs. So, attenuation effect of ICT was the largest in three situations, which is 5% of attenuation at average. And exact couch mesh area hardly occurred the effect. And as a smaller field, attenuation effect was larger. And dependence of gantry angle on beam attenuation. As so, significantly, attenuation was occurred at 120 degrees which attenuated that 7.2%. An assuming formula for correction factor. Assuming formula had coincident, ranging from 150 to 180 degrees. An assuming formula of attenuation will be able to correct dose in treatment planning system, especially usefulness for dynamic conformal arc plan. I think, the dynamic conformal plan, it was using Brainscan calculated in 10 steps, 10-degree steps. So, that's formula for insert the two correct, the isocenter dose is feasible.
So, Discussion 3. And needless to say, Brainscan cannot correct attenuation of ICT during treatment planning, so actual irradiation beam through ICT will be underdose compared with planning dose. Significant increase in beam attenuation as angle of incidence increases, therefore 1.04 to 1.07 of attenuation correction factor should be used to correct isocenter dose when beam will pass through ICT. So, in conclusions. The attenuation of photon beam and its projection angle dependence by ICT existed. Simple method using correction factor was feasible to correct isocenter dose when an attenuation effect could not consider and correct by RTPs. And I hope nearly, sorry, I hope... I want to use latest version of i-plan and pass the [inaudible 00:13:26] in Japan, my hope for Brainlab. This slide shows differences in this study. Thank you for attention. Thank you.
The background and purpose of this study. Imaging Couch Top was developed by medical intelligence corporation and used to Novalis Body system to correct each setup angle error. And Couch Top of our Novalis unit replaced from Exact Couch Top to Imaging Couch Top last year, and without changing the RTPs. ICT provides easy patient setup, but also significantly beam attenuation when beam passes through ICT. We evaluated megavoltage photon beam attenuation of ICT was evaluated and compared with ECT and other fixation tools. This slide shows materials and devices for in this study. Okay, for evaluation elements in this study, at first, effect of x-ray attenuation by passing ICT. Details are comparison between ECT and ICT. And two, compared to output factor.
And second, projection angle dependency was evaluated. And details are X-ray attenuation in each gantry angles, and compared to the fixation tools and ECT and ICT. And compared to assuming formula. Next. As a method of effect of X-ray attenuation by passing ICT slide shown here. Water equivalent phantom was put on the couch and six million X-ray delivered from floor to ceiling. Details of setting of this experiment as it's shown here. And the measurement was done in three situations. That is, the projection to a solid area of ECT, that is pattern A. And projection to mesh area of ECT, that is, pattern B. Projection to Imaging Couch Top is pattern C. And the Method 2, the projection angle dependency was evaluated. The chamber was fixed in center holder of water equivalent phantom. This shape was a sphere type. That phantom's diameter was 16 centimeter.
The measurement was performed on five situations. That is using Head-ring system and Type-S system and phantom on Exact Couch of center and with consider that side slider open and closed consideration. And without side slider open and closed consideration. And phantom Imaging Couch Top. This is assuming formula. This is the schematic view of Exam 2. The structure of ICT makes by homogeneous carbon such as thickness "t". And beam intensity on 8-centimeter depth without passing ICT and with passing ICT from gantry angle theta, were defined I zero and I theta respectively. So, I think the beam intensity and correction factor was defined here. And relationship alpha and theta and gantry angle were this. So, I think the assuming formula is defined this, correction factor equals this formula. This is the result of comparison of X-ray attenuation. Pink line is exact couch mesh type. And yellow line is projection to Imaging Couch Top. And blue line is projection to carbon area of ECT.
These results means Exact Couch Top of mesh area is hardly reduce the obtained charged dose. And similar value was appeared in ICT and the pattern A at Exact Couch Top percent. And Result 2. This slide shows the comparison between output factor and X-ray attenuation in using ICT. So, this slide shows significantly value reducing compared to water data. This value is meaning relative dose to this. This means in field size. And Result 3, the dependence of gantry angle for attenuation effect. This slide shows a 10 by 10 field size and 8 by 8 field size. Look at 120 degree and 240 degree, this areas shows the significantly value reduce in Imaging Couch Top values. This tendency appeared in each situations. That is, 10 by 10, and 8 by 8, and 6 by 6, and 4.2 by 4.2. This tendency was in same conditions. So, this is as result of comparison of correction factor. The pink line shows a measured value. And blue line shows assuming formula values. This fit to 150 to 180, so fitted.
This is highlight of results. The attenuation of photon beam by couch existed. Significant increase in beam attenuation as angle of incidence increases, ranging from 3.9% at 180 degrees to 7.2% at 120 degrees. An assuming formula fit to measurement value ranging from 150 to 180 degrees. So, discussions. Comparison of attenuation effect between ECT and ICTs. So, attenuation effect of ICT was the largest in three situations, which is 5% of attenuation at average. And exact couch mesh area hardly occurred the effect. And as a smaller field, attenuation effect was larger. And dependence of gantry angle on beam attenuation. As so, significantly, attenuation was occurred at 120 degrees which attenuated that 7.2%. An assuming formula for correction factor. Assuming formula had coincident, ranging from 150 to 180 degrees. An assuming formula of attenuation will be able to correct dose in treatment planning system, especially usefulness for dynamic conformal arc plan. I think, the dynamic conformal plan, it was using Brainscan calculated in 10 steps, 10-degree steps. So, that's formula for insert the two correct, the isocenter dose is feasible.
So, Discussion 3. And needless to say, Brainscan cannot correct attenuation of ICT during treatment planning, so actual irradiation beam through ICT will be underdose compared with planning dose. Significant increase in beam attenuation as angle of incidence increases, therefore 1.04 to 1.07 of attenuation correction factor should be used to correct isocenter dose when beam will pass through ICT. So, in conclusions. The attenuation of photon beam and its projection angle dependence by ICT existed. Simple method using correction factor was feasible to correct isocenter dose when an attenuation effect could not consider and correct by RTPs. And I hope nearly, sorry, I hope... I want to use latest version of i-plan and pass the [inaudible 00:13:26] in Japan, my hope for Brainlab. This slide shows differences in this study. Thank you for attention. Thank you.