Carcinoma of the cervix is a global problem. Brachytherapy (BT) is one of the main
radiation therapy components used in the management of cervical cancer. With the
advent of scientific and technological developments in treatment planning, inverse optimization
in BT has been imposed; however, to harness the full potential of inverse
planning in brachytherapy, its thorough comparison with manual optimization methods
Although inverse optimization algorithms are based on different mathematical approaches,
their goals are similar. The underlying principles of these algorithms will
allow them to be applied with the aim of respecting normal structures absorbed dose
limits while delivering high enough tumouricidal dose.
In this work, the physical parameters minimum dose received by 98% and 90% of
the target volume represented by D98 and D90, respectively, were used to evaluate the
treatment plans with respect to the target while the minimum dose received by 2cm3
volume, D2cm3 , was used to investigate complications in organs at risk (OARs). The
conformity index (COIN), was used to describe the coverage of the target by the prescribed
dose (PD) and the fraction of each OAR volume that receives a critical dose,
which may cause complication. The treatment plan evaluation was also performed
in terms of the complication-free tumour control probability, P+. The physical and
radiobiological evaluation corresponding to plans obtained by the inverse planning
simulated annealing algorithm (IPSA) and the hybrid inverse planning optimization
(HIPO) have been compared with corresponding ones for plans obtained using a manual
graphical optimization method.
The main observations of this work are that well tuned class solutions of inverse
optimization methods are able to produce similar dose volume histograms to those
produced with manual graphical optimization and inverse methods have the potential
to spare organs at risk while delivering acceptable dose to the target. In addition, radiobiological
indexes such as the P+ can be useful complements to physical parameters
in treatment plan evaluation.
Stockholms universitets förlag, 2015.
Brachytherapy, treatment planning optimization, IPSA, HIPO, radiobiology, complicationfree