Does the apex optimization line matter for single-channel vaginal cylinder brachytherapy planning?

Yusung Kim; Katherine Cabel; Wenqing Sun

doi:10.1002/acm2.12351

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Does the apex optimization line matter for single-channel vaginal cylinder brachytherapy planning?

Journal article

Open access

Peer reviewed

Does the apex optimization line matter for single-channel vaginal cylinder brachytherapy planning?

Yusung Kim, Katherine Cabel and Wenqing Sun

Journal of applied clinical medical physics, Vol.19(4), pp.307-312

07/2018

DOI: 10.1002/acm2.12351

PMCID: PMC6036350

PMID: 29766643

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Abstract

The objective of this study is to test the impact of the use of the apex optimization line for new vaginal cylinder (VC) applicators. New single channel VC applicators (Varian) that have different top thicknesses but the same diameters as the old VC applicators (2.0 cm diameter, 2.3, 2.6, 3.0, and 3.5 cm) were compared using phantom studies. Old VC applicator plans without the apex optimization line were also compared to the plans with an apex optimization line. The apex doses were monitored at 5 mm depth doses (eight points) where a prescription dose (Rx) of 6 Gy was prescribed. VC surface doses (eight points) were also analyzed. The new VC applicator plans without apex optimization line presented significantly lower 5-mm depth doses over the Rx (on average -31 ± 7%, P < 0.00001) due to thicker VC tops (3.4 ± 1.1 mm thicker with the range of 1.2-4.4 mm) than the old VC applicators. Old VC applicator plans also showed a statistically significant reduction (P < 0.00001) due to the Ir-192 source anisotropic effect at the apex region, but the percent reduction over the Rx was only -7 ± 9%. However, by adding the apex optimization line to the new VC applicator plans, the plans improved 5-mm depth doses (-7 ± 9% over Rx) that were not statistically different from old VC applicator plans (P = 0.923), along with apex VC surface doses (-22 ± 10% over old VC vs -46 ± 7% without using apex optimization line). The use of the apex optimization line is important in order to avoid significant additional cold doses (-24 ± 2%) at the prescription depth (5 mm) of the apex, specifically for the new VC applicators that have thicker tops. A template-based vaginal cylinder planning reduced the intra- and inter-planner variations of manual generation of apex optimization line, along with treatment time.

Radiotherapy Dosage

Humans

Vagina

Female

Brachytherapy

Iridium Radioisotopes

Radiotherapy Planning, Computer-Assisted

Details

Title: Subtitle: Does the apex optimization line matter for single-channel vaginal cylinder brachytherapy planning?
Creators: Yusung Kim - Department of Radiation Oncology, Carver College of Medicine, Iowa, City, IA, USA
Katherine Cabel - Department of Biomedical Engineering, College of Engineering, The University of Iowa, Iowa, City, IA, USA
Wenqing Sun - Department of Radiation Oncology, Carver College of Medicine, Iowa, City, IA, USA
Resource Type: Journal article
Publication Details: Journal of applied clinical medical physics, Vol.19(4), pp.307-312
DOI: 10.1002/acm2.12351
PMID: 29766643
PMCID: PMC6036350
NLM abbreviation: J Appl Clin Med Phys
ISSN: 1526-9914
eISSN: 1526-9914
Publisher: United States
Grant note: P30 CA086862 / NCI NIH HHS
Language: English
Date published: 07/2018
Academic Unit: Radiation Oncology
Record Identifier: 9984047752102771

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