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Technique alternatives for breast radiation oncology: Conventional radiation therapy to tomotherapy.

Fournier-Bidoz N, Kirova Y, Campana F, El Barouky J, Zefkili S, Dendale R, Bollet MA, Mazal A, Fourquet A - J Med Phys (2009)

Bottom Line: This conventional approach can be improved by a field-in-field technique using the linac multi-leaf collimator (MLC).However, careful quality assurance of the treatment planning system must be performed.Tomotherapy is a valuable recourse for complex irradiations like bilateral breast or mammary plus axillary irradiation while a field-in-field associated with a unique isocenter technique can be used for majority of the patients.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, Institut Curie, 26 rue d'Ulm, Paris 75005, France.

ABSTRACT
Breast conserving radiotherapy uses tangential fields and compensating wedges. This conventional approach can be improved by a field-in-field technique using the linac multi-leaf collimator (MLC). A simplified field-in-field technique that planners can easily achieve and which improves dose uniformity in the breast volume is presented here. Field junction problems are more easily solved by the use of a virtual simulation. A unique isocenter can be set at the junction between the supra-clavicular field and the breast tangential fields. However, careful quality assurance of the treatment planning system must be performed. Tomotherapy has promising clinical advantages: the ability of a tomographic image to correct for random set-up errors, a continuous cranio-caudal delivery which suppresses junction problems, the conformality of the dose distribution throughout the complex volumes formed by the lymph nodes and the breasts. Tomotherapy is a valuable recourse for complex irradiations like bilateral breast or mammary plus axillary irradiation while a field-in-field associated with a unique isocenter technique can be used for majority of the patients.

No MeSH data available.


Sagittal dose distribution after adjustment of subfields weights: green iso-dose is 47.5 Gy (95%), yellow isodose is 49 Gy, maximum dose is 51 Gy
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Figure 0003: Sagittal dose distribution after adjustment of subfields weights: green iso-dose is 47.5 Gy (95%), yellow isodose is 49 Gy, maximum dose is 51 Gy

Mentions: At our Institute a field-in-field technique, that is easily achieved by the dosimetrists and applied to all breast patients treated at a linac with MLC, is used. The breast limits are determined by the physician by clinical palpation and marked by radio-opaque markers for CT acquisition. Two open photon tangents are set on the virtual simulation and dose distribution is calculated. The resulting plan is normalized at mid-separation between the two tangents entry points at central axis plane. Fifty grays are prescribed to that point. Iso-dose lines from 48 Gy to 53 Gy by step of 0.5 Gy are visualized on the sagittal plane. Two iso-dose lines which are significantly large and well separate from each other are chosen. The TPS (Eclipse, Varian) is able to show the 3D outline of each iso-dose projected on the tangent beam's eye view (BEV). As an example, Figure 2 shows the 51.5 Gy and 53 Gy iso-doses on the medial and lateral fields respectively. For each tangent one sub-field is created with the MLC shaped to one of the two iso-doses. Weights are subsequently adjusted so that the dose distribution is uniform within the PTV, as recommended by the ICRU guidelines (95% to 107%) at all levels in the breast [Figure 3]. The sub-field weights generally represent a four to eight per cent fraction of the treatment time for one field. We have fixed a minimum treatment time at 10 monitor units (MU). If the uniformity is obtained for less than 10 MU, one of the sub-fields is suppressed.


Technique alternatives for breast radiation oncology: Conventional radiation therapy to tomotherapy.

Fournier-Bidoz N, Kirova Y, Campana F, El Barouky J, Zefkili S, Dendale R, Bollet MA, Mazal A, Fourquet A - J Med Phys (2009)

Sagittal dose distribution after adjustment of subfields weights: green iso-dose is 47.5 Gy (95%), yellow isodose is 49 Gy, maximum dose is 51 Gy
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2807680&req=5

Figure 0003: Sagittal dose distribution after adjustment of subfields weights: green iso-dose is 47.5 Gy (95%), yellow isodose is 49 Gy, maximum dose is 51 Gy
Mentions: At our Institute a field-in-field technique, that is easily achieved by the dosimetrists and applied to all breast patients treated at a linac with MLC, is used. The breast limits are determined by the physician by clinical palpation and marked by radio-opaque markers for CT acquisition. Two open photon tangents are set on the virtual simulation and dose distribution is calculated. The resulting plan is normalized at mid-separation between the two tangents entry points at central axis plane. Fifty grays are prescribed to that point. Iso-dose lines from 48 Gy to 53 Gy by step of 0.5 Gy are visualized on the sagittal plane. Two iso-dose lines which are significantly large and well separate from each other are chosen. The TPS (Eclipse, Varian) is able to show the 3D outline of each iso-dose projected on the tangent beam's eye view (BEV). As an example, Figure 2 shows the 51.5 Gy and 53 Gy iso-doses on the medial and lateral fields respectively. For each tangent one sub-field is created with the MLC shaped to one of the two iso-doses. Weights are subsequently adjusted so that the dose distribution is uniform within the PTV, as recommended by the ICRU guidelines (95% to 107%) at all levels in the breast [Figure 3]. The sub-field weights generally represent a four to eight per cent fraction of the treatment time for one field. We have fixed a minimum treatment time at 10 monitor units (MU). If the uniformity is obtained for less than 10 MU, one of the sub-fields is suppressed.

Bottom Line: This conventional approach can be improved by a field-in-field technique using the linac multi-leaf collimator (MLC).However, careful quality assurance of the treatment planning system must be performed.Tomotherapy is a valuable recourse for complex irradiations like bilateral breast or mammary plus axillary irradiation while a field-in-field associated with a unique isocenter technique can be used for majority of the patients.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, Institut Curie, 26 rue d'Ulm, Paris 75005, France.

ABSTRACT
Breast conserving radiotherapy uses tangential fields and compensating wedges. This conventional approach can be improved by a field-in-field technique using the linac multi-leaf collimator (MLC). A simplified field-in-field technique that planners can easily achieve and which improves dose uniformity in the breast volume is presented here. Field junction problems are more easily solved by the use of a virtual simulation. A unique isocenter can be set at the junction between the supra-clavicular field and the breast tangential fields. However, careful quality assurance of the treatment planning system must be performed. Tomotherapy has promising clinical advantages: the ability of a tomographic image to correct for random set-up errors, a continuous cranio-caudal delivery which suppresses junction problems, the conformality of the dose distribution throughout the complex volumes formed by the lymph nodes and the breasts. Tomotherapy is a valuable recourse for complex irradiations like bilateral breast or mammary plus axillary irradiation while a field-in-field associated with a unique isocenter technique can be used for majority of the patients.

No MeSH data available.