TY - JOUR
T1 - Does the apex optimization line matter for single-channel vaginal cylinder brachytherapy planning?
AU - Kim, Yusung
AU - Cabel, Katherine
AU - Sun, Wenqing
N1 - Publisher Copyright:
© 2018 University of Iowa. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.
PY - 2018/7
Y1 - 2018/7
N2 - 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.
AB - 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.
KW - cervical cancer
KW - high-dose-rate brachytherapy
KW - high-dose-rate brachytherapy treatment planning
KW - optimization
KW - vaginal cylinder planning
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U2 - 10.1002/acm2.12351
DO - 10.1002/acm2.12351
M3 - Article
C2 - 29766643
AN - SCOPUS:85049622650
SN - 1526-9914
VL - 19
SP - 307
EP - 312
JO - Journal of applied clinical medical physics
JF - Journal of applied clinical medical physics
IS - 4
ER -