The optimization of dose delivery for intraoperative high-dose-rate radiation therapy using curved HAM applicators.
OBJECTIVE
To determine the effect of the curvature of Harrison-Anderson-Mick applicators on the dose distribution in high-dose-rate intraoperative radiation therapy (HDR-IORT).


METHODS
Treatment planning was performed with flat applicators using (192)Ir as the radioactive source, and dwell times were optimized using dose-point optimization techniques. These optimized dwell times were then used for the curved applicators, and the dose distributions that would actually be delivered to patients were determined.


RESULTS
The dose directly below the central catheter was strongly dependent on the curvature of the applicator. Steep parabolic curves caused underdoses of as much as 19% at a point 1cm from the convex side of the applicator. The rate of dose reduction with increasing distance from the applicator surface was also a function of the curvature of the applicator.


CONCLUSIONS
The curvature of the applicator profoundly affects dosimetry and can be exploited to optimize coverage of the target during HDR-IORT procedures. To ensure accurate dose delivery, these dose perturbations must be accounted for in the planning process. We recommend maintaining a dosimetry atlas of various applicator sizes and curvatures in addition to one for flat applicators.
Beddar
A Sam
AS
Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA. abeddar@mdanderson.org
Krishnan
Sunil
S
Briere
Tina M
TM
Wang
Xiaochun
X
Delclos
Marc E
ME
Ballo
Matthew T
MT
Das
Prajnan
P
Gould
Spencer
S
Horton
John L
JL
Crane
Christopher H
CH
D001918:Brachytherapy / Q000295:instrumentation; D004867:Equipment Design; D006801:Humans; D007430:Intraoperative Care; D007496:Iridium Radioisotopes / Q000627:therapeutic use; D015642:Radiology, Interventional; D019275:Radiopharmaceuticals / Q000627:therapeutic use; D011878:Radiotherapy / Q000295:instrumentation*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D013499:Surface Properties; D013997:Time Factors
D007496:Iridium Radioisotopes; D019275:Radiopharmaceuticals