Abstract
Purpose
Reduction of the number of implantation needles for prostate brachytherapy will shorten
the duration of implantation procedures and possibly reduce trauma-related morbidity.
The purpose of this study was to investigate possibilities for the minimization of
the number of needles and to investigate the consequences for the dose distribution.
Methods and Materials
A planning study for six different prostate volumes was performed. The number of needles
was minimized by changing fixed 1 cm interseed spacing to free interseed spacing within the needles and by increasing
the seed activity. Dose–volume parameters of prostate and organs at risk (OAR) bladder,
rectum, and urethra were determined. For plans with different needle and seed configurations,
the sensitivity for random seed placement inaccuracies was tested. Dose distributions
of realized implants based on fixed (n=21) and free interseed spacing (n=21) were compared.
Results
The average number of needles (±1 standard deviation) could be reduced from 18.8±3.6 to 12.7±2.9 (−33%) when changing from fixed interseed spacing to free interseed spacing and
subsequently to 7.3±1.0 (−42%) by increasing the seed strength from 0.57 U to 1.14 U. These needle reductions resulted in increased dose inhomogeneity within the prostate
and increased sensitivity of dose–volume parameters of the OAR for random geometrical
inaccuracies. Introduction of free interseed spacing in our clinic resulted in very
satisfactory dose coverage of the prostate (D90=172±17 Gy), while the average number of needles was reduced by 30%.
Conclusions
Substantial reduction of the number of implantation needles is possible without compromising
adequate dose coverage of the prostate. However, the chance of an unpredicted high
dose to the OAR increases as fewer needles are used.
Keywords
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Article Info
Publication History
Published online: August 09, 2010
Accepted:
July 9,
2009
Received in revised form:
July 8,
2009
Received:
November 26,
2008
Identification
Copyright
© 2010 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.
