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Improvement of dose distribution with irregular surface compensator in whole breast radiotherapy.

Hideki F, Nao K, Hiroyuki H, Hiroshi K, Haruyuki F - J Med Phys (2013)

Bottom Line: The Eclipse treatment planning system (Varian Medical Systems) was used for the dose calculation: For the physical wedge technique, the wedge angle was selected to provide the best dose homogeneity; for the ISC technique, the fluence editor application was used to extend the optimal fluence.These two treatment plans were compared in terms of doses in the planning target volume, the dose homogeneity index, the maximum dose, ipsilateral lung and heart doses for left breast irradiation, and the monitor unit counts required for treatment.However, the monitor unit counts were not significantly different between the techniques (P > 0.05).

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, Osaka Saiseikai Nakatsu Hospital, Osaka, Japan.

ABSTRACT
Aim of this study was to compare the dosimetric aspects of whole breast radiotherapy (WBRT) between an irregular surface compensator (ISC) and a conventional tangential field technique using physical wedges. Treatment plans were produced for 20 patients. The Eclipse treatment planning system (Varian Medical Systems) was used for the dose calculation: For the physical wedge technique, the wedge angle was selected to provide the best dose homogeneity; for the ISC technique, the fluence editor application was used to extend the optimal fluence. These two treatment plans were compared in terms of doses in the planning target volume, the dose homogeneity index, the maximum dose, ipsilateral lung and heart doses for left breast irradiation, and the monitor unit counts required for treatment. Compared with the physical wedge technique, the ISC technique significantly reduced the dose homogeneity index, the maximum dose, the volumes received at 105% of the prescription dose, as well as reducing both the ipsilateral lung and heart doses (P < 0.01 for all comparisons). However, the monitor unit counts were not significantly different between the techniques (P > 0.05). Thus, the ISC technique for WBRT enables significantly better dose distribution in the planning target volume.

No MeSH data available.


(a) Typical initial fluence pattern. (b) Fluence pattern after modification using the fluence editor tool
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Figure 1: (a) Typical initial fluence pattern. (b) Fluence pattern after modification using the fluence editor tool

Mentions: First, by viewing the dose distribution along the BEV, the fluence editor was manipulated to shield the breast areas receiving >105% of the prescribed dose. On the BEV windows, the value of the transmission factor of the hot spot regions was measured. The transmission factor was replaced by the paintbrush. The transmission factor of the cold spot regions was similarly replaced. The hot and cold spot regions could be modified by replacing the transmission factor. Fluence maps were converted to leaf sequences for dMLC delivery. After recalculation of dose distribution, if the dose remained >105%, the processes described were repeated to achieve an optimal dose distribution. A typical initial fluence pattern is presented in Figure 1a, and a fluence pattern after modification using the fluence editor is presented in Figure 1b.


Improvement of dose distribution with irregular surface compensator in whole breast radiotherapy.

Hideki F, Nao K, Hiroyuki H, Hiroshi K, Haruyuki F - J Med Phys (2013)

(a) Typical initial fluence pattern. (b) Fluence pattern after modification using the fluence editor tool
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3775034&req=5

Figure 1: (a) Typical initial fluence pattern. (b) Fluence pattern after modification using the fluence editor tool
Mentions: First, by viewing the dose distribution along the BEV, the fluence editor was manipulated to shield the breast areas receiving >105% of the prescribed dose. On the BEV windows, the value of the transmission factor of the hot spot regions was measured. The transmission factor was replaced by the paintbrush. The transmission factor of the cold spot regions was similarly replaced. The hot and cold spot regions could be modified by replacing the transmission factor. Fluence maps were converted to leaf sequences for dMLC delivery. After recalculation of dose distribution, if the dose remained >105%, the processes described were repeated to achieve an optimal dose distribution. A typical initial fluence pattern is presented in Figure 1a, and a fluence pattern after modification using the fluence editor is presented in Figure 1b.

Bottom Line: The Eclipse treatment planning system (Varian Medical Systems) was used for the dose calculation: For the physical wedge technique, the wedge angle was selected to provide the best dose homogeneity; for the ISC technique, the fluence editor application was used to extend the optimal fluence.These two treatment plans were compared in terms of doses in the planning target volume, the dose homogeneity index, the maximum dose, ipsilateral lung and heart doses for left breast irradiation, and the monitor unit counts required for treatment.However, the monitor unit counts were not significantly different between the techniques (P > 0.05).

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, Osaka Saiseikai Nakatsu Hospital, Osaka, Japan.

ABSTRACT
Aim of this study was to compare the dosimetric aspects of whole breast radiotherapy (WBRT) between an irregular surface compensator (ISC) and a conventional tangential field technique using physical wedges. Treatment plans were produced for 20 patients. The Eclipse treatment planning system (Varian Medical Systems) was used for the dose calculation: For the physical wedge technique, the wedge angle was selected to provide the best dose homogeneity; for the ISC technique, the fluence editor application was used to extend the optimal fluence. These two treatment plans were compared in terms of doses in the planning target volume, the dose homogeneity index, the maximum dose, ipsilateral lung and heart doses for left breast irradiation, and the monitor unit counts required for treatment. Compared with the physical wedge technique, the ISC technique significantly reduced the dose homogeneity index, the maximum dose, the volumes received at 105% of the prescription dose, as well as reducing both the ipsilateral lung and heart doses (P < 0.01 for all comparisons). However, the monitor unit counts were not significantly different between the techniques (P > 0.05). Thus, the ISC technique for WBRT enables significantly better dose distribution in the planning target volume.

No MeSH data available.