183 CT planning of HDR breast implants: A contribution to quality assurance

Abstract

The purpose of this presentation is to describe the procedure of the interstitial boost therapy planning in breast cancer irradiation in the Hospital of Sisters of Mercy in Linz, Austria. The use of a boost irradiation at the primary tumour site is associated with an increased local control. Maximum effectiveness of the boost irradiation depends on accurate location of the target volume which is the surgical tumour bed. There are some reports about localization techniques of the boost volume for external irradiation. Less has been reported about the target volume localization of HDR interstitial implants of the breast. We have introduced the development of a treatment planning method to obtain accurately located interstitial implants and homogenous dose distributions and therefore full coverage of the target volume. At the time of the boost irradiation, treatment planning is started in the simulator room, to define the needle position and therefore the target volume represented by the implanted clips. Then the implantation is done in the afterloading room. A device for patient transportation between Indium unit, simulator and CT scanner has been constructed. The implanted needles and the clips are visualized by means of the CT-scanner. So the source dwell position and therefore the length to be irradiated can be determined in order to provide adequate coverage of the clipped tumour bed. The isodose distribution and the relationship to the surrounding tissues is obtained by the planning compute of the remote afterloading device. So the source dwell times can be determined if there will be an overdosage for the normal tissues. We conclude that this procedure with careful attention to the source position by CT planning results in an accurate treatment of the target volume. The implant and the dose distribution to the surrounding normal tissues are documented by the CT images. The planning procedure is made feasible by the use of the special transportation device and has the advantage of patient immobilization. The purpose of this presentation is to describe the procedure of the interstitial boost therapy planning in breast cancer irradiation in the Hospital of Sisters of Mercy in Linz, Austria. The use of a boost irradiation at the primary tumour site is associated with an increased local control. Maximum effectiveness of the boost irradiation depends on accurate location of the target volume which is the surgical tumour bed. There are some reports about localization techniques of the boost volume for external irradiation. Less has been reported about the target volume localization of HDR interstitial implants of the breast. We have introduced the development of a treatment planning method to obtain accurately located interstitial implants and homogenous dose distributions and therefore full coverage of the target volume. At the time of the boost irradiation, treatment planning is started in the simulator room, to define the needle position and therefore the target volume represented by the implanted clips. Then the implantation is done in the afterloading room. A device for patient transportation between Indium unit, simulator and CT scanner has been constructed. The implanted needles and the clips are visualized by means of the CT-scanner. So the source dwell position and therefore the length to be irradiated can be determined in order to provide adequate coverage of the clipped tumour bed. The isodose distribution and the relationship to the surrounding tissues is obtained by the planning compute of the remote afterloading device. So the source dwell times can be determined if there will be an overdosage for the normal tissues. We conclude that this procedure with careful attention to the source position by CT planning results in an accurate treatment of the target volume. The implant and the dose distribution to the surrounding normal tissues are documented by the CT images. The planning procedure is made feasible by the use of the special transportation device and has the advantage of patient immobilization.