Influence of manual segmentation in DIR on accumulated dose evaluation for cervical cancer
Elske Gort,
The Netherlands
PD-0397
Abstract
Influence of manual segmentation in DIR on accumulated dose evaluation for cervical cancer
Authors: Elske Gort1, Jannet C. Beukema1, Marjan J. Spijkerman-Bergsma1, Marianne L. de Vries-de Groot1, Stefan Both1, Johannes A. Langendijk1, Witold P. Matysiak1, Charlotte L. Brouwer2
1University Medical Center Groningen, Department of Radiation Oncology, Groningen, The Netherlands; 2University Medical Center Groningen, Department of Radiation Oncology, Groningen, The Netherlands
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Purpose or Objective
When treating cervical cancer patients
with VMAT, due to sensitivity to inter-fraction motion, adaptive strategies
could be required to maintain target coverage. Manual segmentation of CTV and
OARs on repeat-CT scans (reCTs) is time consuming and may delay decisions whether
to perform plan adaptations. Our aim was to investigate differences in clinical
decisions for re-planning based on manual vs automated dose accumulation.
Material and Methods
Twelve
cervical cancer patients were included in a prospective study undergoing 5
weekly reCTs. The primary and para-aortic lymph node target and OAR volumes were
manually segmented on all CTs. Clinical re-planning was performed for 3 patients. Two-arcs VMAT plans for 25 fractions of 1.8
Gy were made on the planning CT scan (planCT) and recalculated as well as robustly evaluated on
the reCTs [1]. Deformable
hybrid intensity and structure based image registrations were performed using
the manually segmented GTV, vagina, uterus and lymph nodes CTV as controlling
ROIs (DIR_manual) and without controlling ROIs (DIR_automated). The
target and OAR contours were warped using DIR_automated and resulting automated
versus manually segmented dose and volume differences were evaluated. The voxelwise
minimum (vox min) reCT doses were warped to the planCT using DIR_manual and
DIR_automated, and the different accumulated doses were compared, where the
criterion for acceptable coverage was ITV D98 > 95%.
Results
Manual vs automated segmented vox min lymph
nodes D98 (Gy) at reCTs showed a significant difference (Table 1). For the
other target volumes no significant dose differences were found. Regarding OAR doses, only bowel bag Dmean (Gy)
showed a significant difference. Manual vs automated segments showed only a
good concordance for lymph nodes, bone marrow and sacrum (concordance index ≥
0.8). For 7 patients, conclusions on accumulated vox min D98 ITV target
coverage were identical using DIR_automated vs DIR_manual. For 2 patients, DIR_manual
showed correctly that ITV coverage was not maintained in contrast to using DIR_automated
(Figure 1A, marked circular). For 1 patient’s evaluation, ITV coverage was
correctly maintained using DIR_manual in contrast to using DIR_automated. Out
of 10 clinically re-planned reCTs, manual in contrast to automated segmentation
showed correctly that individual coverage was not maintained for 4 GTV and
vagina, 3 uterus and 2 lymph nodes target volumes (Figure 1B, marked circular).
The ratio between automated vs manual segmented OAR volumes (cc) was close to 1
for all OARs, except for bladder and rectum (Figure 1C). Automated contour warping
of the bowel bag resulted in underestimation of the DVH (Figure 1D).
![](https://www.estro.org:443/ESTRO/media/Abstracts/870/641b14dc-6b6f-4ce1-ac8c-6b23dae75ff6.png)
![](https://www.estro.org:443/ESTRO/media/Abstracts/870/71161d4b-b94c-48a2-9214-ccbd2c8b6711.png)
Conclusion
Replacing
manual with automated CTV and OAR delineation could lead to missing the required
re-planning and inadequate estimation of individual target and OAR doses. Deep
learning CT segmentation and registration could be promising to improve the
quality of dose accumulation in a time effective manner.