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. 2013 Dec;5(4):250-7.
doi: 10.5114/jcb.2013.39453. Epub 2013 Dec 18.

Dosimetric impacts of applicator displacements and applicator reconstruction-uncertainties on 3D image-guided brachytherapy for cervical cancer

Joshua Schindel  1 , Winson Zhang  1 , Sudershan K Bhatia  2 , Wenqing Sun  2 , Yusung Kim  2
Affiliations

Dosimetric impacts of applicator displacements and applicator reconstruction-uncertainties on 3D image-guided brachytherapy for cervical cancer

Joshua Schindel et al. J Contemp Brachytherapy. 2013 Dec.

Abstract

Purpose: To quantify the dosimetric impact of applicator displacements and applicator reconstruction-uncertainties through simulated planning studies of virtual applicator shifts.

Material and methods: Twenty randomly selected high-dose-rate (HDR) titanium tandem-and-ovoid (T&O) plans were retrospectively studied. MRI-guided, conformal brachytherapy (MRIG-CBT) plans were retrospectively generated. To simulate T&O displacement, the whole T&O set was virtually shifted on treatment planning system in the cranial (+) and the caudal (-) direction after each dose calculation. Each shifted plan was compared to an unshifted plan. To simulate T&O reconstruction-uncertainties, each tandem and ovoid was separately shifted along its axis before performing the dose calculation. After the dose calculation, the calculated isodose lines and T&O were moved back to unshifted T&O position. Shifted and shifted-back plan were compared.

Results: Regarding the dosimetric impact of the simulated T&O displacements, rectal D2cc values were observed as being the most sensitive to change due to T&O displacement among all dosimetric metrics regardless of point A (p < 0.013) or MRIG-CBT plans (p < 0.0277). To avoid more than 10% change, ± 1.5 mm T&O displacements were accommodated for both point A and MRIG-CBT plans. The dosimetric impact of T&O displacements on sigmoid (p < 0.0005), bladder (p < 0.0001), HR-CTV (p < 0.0036), and point A (p < 0.0015) were significantly larger in the MRIG-CBT plans than point A plans. Regarding the dosimetric impact of T&O reconstruction-uncertainties, less than ± 3.0 mm reconstruction-uncertainties were also required in order to avoid more than 10% dosimetric change in either the point A or MRIG-CBT plans.

Conclusions: The dosimetric impact of simulated T&O displacements was significantly larger in the MRIG-CBT plans than in the point A plans. Either ± 3 mm T&O displacement or a ± 4.5 mm T&O reconstruction-uncertainty could cause greater than 10% dosimetric change for both point A plans and MRIG-CBT plans.

Keywords: 3D image; applicator shifts; brachytherapy; cervical cancer; dosimetry; high-dose-rate.

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Figures

Fig. 1
Fig. 1
The simulated T&O displacements on a treatment planning system by virtual shifting whole T&O (A). The original unshifted plans of conventional, point A technique (B) and MRIG-CBT (C). The resulting isodose lines due to –20 mm shift for conventional plan (D) and MRIG-CBT plan (E)
Fig. 2
Fig. 2
The simulated T&O reconstruction uncertainties on a treatment planning system by shifting each tandem and ovoid (A). The resulting isodose lines of conventional plan (B) and MRIG-CBT plan (C) after –10 mm shift to simulate T&O reconstruction uncertainties and dose calculation. To evaluate their dosimetric impacts, the plans of B and C were compared to their simulated, delivered plans (D and E, respectively) that were created by shifting T&O back to their original position and dose calculation
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References

    1. Viswanathan AN, Erickson BA. Three-dimensional imaging in gynecologic brachytherapy: a survey of the American Brachytherapy Society. Int J Radiat Oncol Biol Phys. 2010;76:104–109. - PubMed
    1. Haie-Meder C, Pötter R, Van Limbergen E, et al. Recommendations from gynaecological (GYN) GEC-ESTRO Working Group (I): concepts and terms in 3D image based 3D treatment planning in cervix cancer brachytherapy with emphasis on MRI assessment of GTV and CTV. Radiother Oncol. 2005;74:235–245. - PubMed
    1. Pötter R, Haie-Meder C, Van Limbergen E, et al. Recommendations from gynaecological (GYN) GEC ESTRO working group (II): concepts and terms in 3D image-based treatment planning in cervix cancer brachytherapy-3D dose volume parameters and aspects of 3D image-based anatomy, radiation physics, radiobiology. Radiother Oncol. 2006;78:67–77. - PubMed
    1. Hellebust TP, Kirisits C, Berger D, et al. Recommendations from gynaecological (GYN) GEC-ESTRO working group: considerations and pitfalls in commissioning and applicator reconstruction in 3D image-based treatment planning of cervix cancer brachytherapy. Radiother Oncol. 2010;96:153–160. - PubMed
    1. Viswanathan AN, Dimopoulos J, Kirisits C, et al. Computed tomography versus magnetic resonance imaging-based contouring in cervical cancer brachytherapy: results of a prospective trial and preliminary guidelines for standardized contours. Int J Radiat Oncol Biol Phys. 2007;68:491–498. - PubMed

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