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Dosimetric and radiobiological evaluation of hybrid inverse planning and optimization for cervical cancer brachytherapy
Stockholm University, Faculty of Science, Department of Physics. Eduardo Mondlane University, Mozambique.
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2015 (English)In: Anticancer Research, ISSN 0250-7005, E-ISSN 1791-7530, Vol. 35, no 11, 6091-6096 p.Article in journal (Refereed) Published
Abstract [en]

Aim: To compare manual graphical optimization (GrO) with hybrid inverse planning optimization (HIPO) of cervical cancer brachytherapy treatment plans using physical and radiobiological tools. Patients and Methods: Ten patients suffering from cervical cancer, treated with pulsed brachytherapy using GrO plans, were included in the study. For each patient, four different HIPO class solutions with different dose objectives to the target and constraints to the organs at risk (OAR) produced four optimized plans, that were each compared to the corresponding GrO plan. Class solution in HIPO is a set of parameters consisting of dose constraints and penalty weights, which are used for optimization. The comparison was based on the following dosimetric parameters: conformity index (COIN), minimum dose received by 98% and 90% of the high-risk clinical target volume (represented by D98 and D90, respectively), and the minimum dose imparted to 2 cm3 (D2cm3) of the most exposed OAR i.e. bladder, sigmoid colon or rectum. The HIPO class solution which produced plans with overall better dosimetric parameters was selected and its plans were compared with manual GrO plans from a radiobiological viewpoint based on the calculated complication-free tumour control probability, P+. Results: The average COIN for the GrO and the selected HIPO plans were 0.22 and 0.30, respectively. The median COIN of the GrO and the HIPO plans were not statistically different (p>0.05, Wilcoxon test). The relative percentage difference of the averaged P+ values between the HIPO and GrO plans evaluated together with the external beam radiation therapy plans was 0.01%, 0.37% and 0.98% for the bladder, sigmoid colon and rectum, respectively. The lowest P+ value for all the plans was 98.44% for sigmoid colon. Conclusion: HIPO presented comparable results in relation to manual planning with respect to dosimetric and radiobiological parameters.

Place, publisher, year, edition, pages
2015. Vol. 35, no 11, 6091-6096 p.
Keyword [en]
Pulsed brachytherapy, optimization, radiobiology, treatment planning, HIPO
National Category
Cancer and Oncology
URN: urn:nbn:se:su:diva-120468ISI: 000363794900042OAI: diva2:852685
Available from: 2015-09-09 Created: 2015-09-09 Last updated: 2016-05-03Bibliographically approved
In thesis
1. Optimization of brachytherapy for cervical cancer using inverse planning algorithms.
Open this publication in new window or tab >>Optimization of brachytherapy for cervical cancer using inverse planning algorithms.
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

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

is warranted.

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.

Place, publisher, year, edition, pages
Stockholms universitets förlag, 2015
Brachytherapy, treatment planning optimization, IPSA, HIPO, radiobiology, complicationfree
National Category
Physical Sciences
Research subject
Medical Radiation Physics
urn:nbn:se:su:diva-121548 (URN)
Available from: 2016-05-03 Created: 2015-10-07 Last updated: 2016-05-03Bibliographically approved

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Toma-Dasu, Iuliana
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