An equation to QA check the total treatment time for single-catheter HDR brachytherapy.
OBJECTIVE
To develop a simple equation that can be used to quickly QA check the total treatment time needed for straight or moderately bending, single-catheter implants from the treatment length and dose-prescription depth. A method to quickly check the total treatment time is useful for high dose rate (HDR) treatments, but may be most useful for intravascular patients that are catheterized while planning the treatment.


METHODS
Nucletron-Oldelft treatment planning software was used to plan treatments with treatment lengths from 50 to 200 mm, and dose-prescription depths from 2 to 14 mm. For each plan, dose points were defined at a fixed depth away from the catheter. Doses were calculated, normalized, and optimized using the dose points. From these plans, a single equation was developed for the total treatment time as a function of treatment length and dose-prescription depth.


RESULTS
Total treatment time increases linearly with treatment length and supra-linearly with dose-prescription depth. A difference of 3% or more between the treatment time determined by the QA check equation and by the treatment planning software will alert the clinician and physicist to check for potential errors in dose prescription, prescription depth, source activity, treatment length, or inadvertent modifications to physics parameters used in the treatment planning software.


CONCLUSIONS
The simple equation that is developed can be used to quickly and accurately QA check the total treatment time needed for straight or moderately bending, single-catheter implants.
Rogus
R D
RD
Department of Radiation Oncology, University of California Davis Cancer Center, Sacramento 95817, USA.
Smith
M J
MJ
Kubo
H D
HD
D001918:Brachytherapy / Q000379:methods*; D016014:Linear Models; D055585:Physical Phenomena; D010825:Physics; D011874:Radiometry / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D013997:Time Factors