Abstract
PURPOSE
The sigmoid is an important organ at risk for gynecological brachytherapy (BT). However,
the reliability of localization of high-dose regions during multi-fractionated treatment
is limited. This work reports the methodological development of sigmoid points to
summate multi-fractionated doses.
METHODS AND MATERIAL
Ten paired MRI data sets of ring-based intracavitary brachytherapy were obtained.
Simulating a virtual endoscope, a reference line was created along the central axis
of the anorectosigmoid for each implant. A trendline was generated, and linear dose
was determined. Three-dimensional (3D) coordinates of high-dose regions were identified,
and overlap was determined. In the next step, 3D coordinates of high-dose sigmoid
points were localized in reference to cervical os and re-verified for location in
reference to sigmoid lumen and corroboration with 2cc doses. With minor modifications,
sigmoid points were proposed.
RESULTS
In 6 of 10 patients, high-dose regions co-localized in subsequent fractions of BT.
Three high-dose regions were identified along the sigmoid length and proposed as sigmoid
points in reference to cervical os. (S1’= 0.5 cm right, 1.5 cm posterior, and 2.4
cm cranial; S2’ = 0.3 cm anterior and 4.5 cm cranial; S3’ = 2.7 cm left, 3 cm anterior,
and 3.6 cm cranial to the cervical os). S1’ and S2’ were located in the sigmoid in
70% and 60% of data sets. The mean difference between D2cc and S1’/S2’ was 0.30 Gy
and 1.06 Gy respectively. S3’ had limited corroboration to sigmoid lumen or 2 cc doses.
The points S1’ and S2’ were further modified (minor) for applicability and proposed
as sigmoid points 1 and 2 (SP1 0.5 right,1.5 posterior and 2.5 cm cranial to cervical
os and SP2 (0.5 cm anterior and 4.5 cm cranial to cervical os)).
CONCLUSION
SP1 and SP 2 are proposed as a surrogate for 2 cc sigmoid doses and may provide a
method of reliable inter-fraction dose summation. This pilot work requires further
validation.
Keywords
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Article info
Publication history
Published online: March 05, 2023
Accepted:
January 13,
2023
Received in revised form:
November 9,
2022
Received:
September 13,
2022
Publication stage
In Press Corrected ProofFootnotes
Disclosures: SC receives funding from Varian Alina Sturdza reports grants from Stiftung Philanthropie Österreich through Dr. Oliver Jungnickel during the conduct of the study; outside the submitted work AS receives grant from Elekta
This work was supported by Department of Science and Technology, India Austria mobility grant and he Centre for International Cooperation & Mobility (ICM) of the Austrian Agency for International Cooperation in Education and Research (OeAD-GmbH) Grant number: IN 02/2017.
Identification
Copyright
© 2023 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.
