Step 1: Comparison of measured data
Comparison of data measured with & without IQM in plotting tank (6, 10 & 6FFF).
Conclusion
- No significant differences in O/P factors was detected.
- The beam attenuation is found to be a fixed amount for each energy.
- IQM has little effect on PDD beyond Dmax or on profiles <20x20cm.
- For 6 & 10 MV modelling at larger radial distances needed review.
Step2: Comparison with existing clinical models
Step3: Initial validation
Conclusions
- The build up region is modified by the presence of the IQM, reducing ‘skin sparing’.
- Smaller field PDDs & Profiles are not affected by IQM.
- Larger fields have shoulders drop, more notably at shallower depths.
- Adjustment of arbitrary fluence profile improved agreement – but not observable clinical benefit.
- Clinical models acceptable at 6MV & 10MV.
- Simple correction factor to change MUs was all that was required in Pinnacle 9.8.
- Validation of your clinical models necessary when integrating the IQM into your planning system, but modifications are likely to be small.
