- Email: [email protected]
2319
S388
I. J. Radiation Oncology
● Biology ● Physics
Volume 66, Number 3, Supplement, 2006
grade 2 rectal bleeding, with a median time from the completion of HDR-BT to the occurrence of 11 months (7–14 months). No patients developed grade 3 or more severe rectal complication. The incidence of acute and late toxicity did not differ significantly according to the fractionation schema of HDR-BT. Conclusions: The results of this study demonstrated that HDR-BT combined with hypofractionated EBRT was effective and feasible as a safe method for escalating the total dose to the prostate with acceptable risk of acute and late GU and GI toxicities. Author Disclosure: T. Akimoto, None; H. Katoh, None; K. Shirai, None; K. Harada, None; K. Ito, None; T. Yamamoto, None; T. Nakano, None.
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Quantification of Intrafraction Prostate Motion and Shape Change Using Multiple Implanted Fiducials
S. Friesen, L. Court, A. D’Amico, C. Tempany, R. Cormack Brigham & Women’s Hospital, Boston, MA Purpose/Objective(s): To quantify intrafraction shifts and shape change of the prostate by using brachytherapy seeds as surrogate fiducial markers. Materials/Methods: Twelve patients who had previously received brachytherapy treatment for prostate cancer with implanted I-125 seeds underwent a dynamic MR imaging study where 3 MR series were obtained over a period of 10 minutes (the approximate time required for an external radiation therapy fraction). Using Eclipse planning software, 10 individual fiducial markers (I-125 seeds) were identified at various locations throughout the gland. The same markers were identified in each of the 3 MR series, and their positions were normalized to a bony landmark to remove any patient motion effects. Changes in the coordinates of the markers were used to quantify shifts of different portions of the prostate (i.e. shape change). Results: Of the 12 patients analyzed, 10 showed no significant prostate motion (less than 3mm shift of any one marker). A global posterior shift (4.5⫾0.13mm) was noted in one patient between the first and second MR series. A second patient showed a posterior shift of 7mm at the superior end of the prostate, compared to no change at the inferior end. This is equivalent to a change in pitch of 8-degrees. Conclusions: In most cases there was no significant motion or shape change. However, for two cases (15%) there was a significant motion/shape change which, depending on PTV margins, could have moved part of the prostate out of the treatment fields. It may, therefore, be useful to either monitor prostate position during treatment, or attempt prostate immobilization (e.g. using an endorectal balloon).
Author Disclosure: S. Friesen, None; L. Court, None; A. D’Amico, None; C. Tempany, None; R. Cormack, None.
I. J. Radiation Oncology
● Biology ● Physics
Volume 66, Number 3, Supplement, 2006
grade 2 rectal bleeding, with a median time from the completion of HDR-BT to the occurrence of 11 months (7–14 months). No patients developed grade 3 or more severe rectal complication. The incidence of acute and late toxicity did not differ significantly according to the fractionation schema of HDR-BT. Conclusions: The results of this study demonstrated that HDR-BT combined with hypofractionated EBRT was effective and feasible as a safe method for escalating the total dose to the prostate with acceptable risk of acute and late GU and GI toxicities. Author Disclosure: T. Akimoto, None; H. Katoh, None; K. Shirai, None; K. Harada, None; K. Ito, None; T. Yamamoto, None; T. Nakano, None.
2319
Quantification of Intrafraction Prostate Motion and Shape Change Using Multiple Implanted Fiducials
S. Friesen, L. Court, A. D’Amico, C. Tempany, R. Cormack Brigham & Women’s Hospital, Boston, MA Purpose/Objective(s): To quantify intrafraction shifts and shape change of the prostate by using brachytherapy seeds as surrogate fiducial markers. Materials/Methods: Twelve patients who had previously received brachytherapy treatment for prostate cancer with implanted I-125 seeds underwent a dynamic MR imaging study where 3 MR series were obtained over a period of 10 minutes (the approximate time required for an external radiation therapy fraction). Using Eclipse planning software, 10 individual fiducial markers (I-125 seeds) were identified at various locations throughout the gland. The same markers were identified in each of the 3 MR series, and their positions were normalized to a bony landmark to remove any patient motion effects. Changes in the coordinates of the markers were used to quantify shifts of different portions of the prostate (i.e. shape change). Results: Of the 12 patients analyzed, 10 showed no significant prostate motion (less than 3mm shift of any one marker). A global posterior shift (4.5⫾0.13mm) was noted in one patient between the first and second MR series. A second patient showed a posterior shift of 7mm at the superior end of the prostate, compared to no change at the inferior end. This is equivalent to a change in pitch of 8-degrees. Conclusions: In most cases there was no significant motion or shape change. However, for two cases (15%) there was a significant motion/shape change which, depending on PTV margins, could have moved part of the prostate out of the treatment fields. It may, therefore, be useful to either monitor prostate position during treatment, or attempt prostate immobilization (e.g. using an endorectal balloon).
Author Disclosure: S. Friesen, None; L. Court, None; A. D’Amico, None; C. Tempany, None; R. Cormack, None.