Local Setup Errors in Image-Guided Radiotherapy for Head and Neck Cancer Patients Immobilized With a Custom-Made Device

Giske, Kristina; Stoiber, Eva Maria; Schwarz, Michael; Stoll, Armin; Muenter, Marc W.; Timke, Carmen; Roeder, Falk; Debus, Jürgen; Huber, Peter E.; Thieke, Christian; Bendl, Rolf

doi:10.1016/j.ijrobp.2010.07.1980

Cited by 28 publications

(21 citation statements)

References 14 publications

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“…The patients were treated postoperatively for oropharyngeal cancer or received definitive radiation therapy for locally advanced hypopharyngeal cancer. To reduce pose variation all patients were immobilized with a customized scotch-cast head mask and a vacuum pillow [10]. A stereotactic head frame was used for daily positioning and image guidance was applied with an in-room, on-rails, single slice spiral CT-scanner (Primatom, Siemens, Erlangen).…”

Section: Methodsmentioning

confidence: 99%

“…Reasons for this uncertainties are mainly setup errors of the positioning devices [9], pose variations due to different bone and joint positions, soft tissue shift caused by muscle and organ activites as well as weight loss of the patients [10–13]. While rigid setup uncertainties can be compensated with rigid treatment couch corrections calculated from fraction control CT images in image guided radiation therapy (IGRT) [14], the remaining anatomical deformations of the tumor shape can compromise the dose coverage of the CTV [15,16].…”

Section: Introductionmentioning

confidence: 99%

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Comparison of Safety Margin Generation Concepts in Image Guided Radiotherapy to Account for Daily Head and Neck Pose Variations

et al. 2016

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PurposeIntensity modulated radiation therapy (IMRT) of head and neck tumors allows a precise conformation of the high-dose region to clinical target volumes (CTVs) while respecting dose limits to organs a risk (OARs). Accurate patient setup reduces translational and rotational deviations between therapy planning and therapy delivery days. However, uncertainties in the shape of the CTV and OARs due to e.g. small pose variations in the highly deformable anatomy of the head and neck region can still compromise the dose conformation. Routinely applied safety margins around the CTV cause higher dose deposition in adjacent healthy tissue and should be kept as small as possible.Materials and MethodsIn this work we evaluate and compare three approaches for margin generation 1) a clinically used approach with a constant isotropic 3 mm margin, 2) a previously proposed approach adopting a spatial model of the patient and 3) a newly developed approach adopting a biomechanical model of the patient. All approaches are retrospectively evaluated using a large patient cohort of over 500 fraction control CT images with heterogeneous pose changes. Automatic methods for finding landmark positions in the control CT images are combined with a patient specific biomechanical finite element model to evaluate the CTV deformation.ResultsThe applied methods for deformation modeling show that the pose changes cause deformations in the target region with a mean motion magnitude of 1.80 mm. We found that the CTV size can be reduced by both variable margin approaches by 15.6% and 13.3% respectively, while maintaining the CTV coverage. With approach 3 an increase of target coverage was obtained.ConclusionVariable margins increase target coverage, reduce risk to OARs and improve healthy tissue sparing at the same time.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Comparison of Safety Margin Generation Concepts in Image Guided Radiotherapy to Account for Daily Head and Neck Pose Variations

et al. 2016

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“…Patients were positioned using a stereotactic setup. Both, fixation and positioning setup have been described previously [4]. …”

Section: Methodsmentioning

confidence: 99%

“…It is deduced from a cohort of 45 patients. The additional margin amounts for 4 mm [4]. The margin is derived from local positioning uncertainties of the CTV region, however, in this study it is also applied to the eCTV to approximate the actually required margin.…”

Section: Methodsmentioning

confidence: 99%

“…These margins enlarge the high-dose region and thus worsen the dose distribution from the OARs point of view, since the distance between the avoidance structures and the dose gradients of the high-dose region is decreased. Further interfractional variations in the position of the OAR, which are known to occur in spite of elaborate patient fixation devices [4-6], may also lead to differences in the applied dose distribution.…”

Section: Introductionmentioning

confidence: 99%

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IGRT versus non-IGRT for postoperative head-and-neck IMRT patients: dosimetric consequences arising from a PTV margin reduction

Schwarz¹,

Giske²,

Stoll³

et al. 2012

Radiat Oncol

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BackgroundTo evaluate the impact of image-guided radiation therapy (IGRT) versus non-image-guided radiation therapy (non-IGRT) on the dose to the clinical target volume (CTV) and the cervical spinal cord during fractionated intensity-modulated radiation therapy (IMRT) for head-and-neck cancer (HNC) patients.Material and MethodsFor detailed investigation, 4 exemplary patients with daily control-CT scans (total 118 CT scans) were analyzed. For the IGRT approach a target point correction (TPC) derived from a rigid registration focused to the high-dose region was used. In the non-IGRT setting, instead of a TPC, an additional cohort-based safety margin was applied. The dose distributions of the CTV and spinal cord were calculated on each control-CT and the resulting dose volume histograms (DVHs) were compared with the planned ones fraction by fraction. The D50 and D98 values for the CTV and the D5 values of the spinal cord were additionally reported.ResultsIn general, the D50 and D98 histograms show no remarkable difference between both strategies. Yet, our detailed analysis also reveals differences in individual dose coverage worth inspection. Using IGRT, the D5 histograms show that the spinal cord less frequently receives a higher dose than planned compared to the non-IGRT setting. This effect is even more pronounced when looking at the curve progressions of the respective DVHs.ConclusionsBoth approaches are equally effective in maintaining CTV coverage. However, IGRT is beneficial in spinal cord sparing. The use of an additional margin in the non-IGRT approach frequently results in a higher dose to the spinal cord than originally planned. This implies that a margin reduction combined with an IGRT correction helps to maintain spinal cord dose sparing best as possible. Yet, a detailed analysis of the dosimetric consequences dependent on the used strategy is required, to detect single fractions with unacceptable dosimetric deviations.

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Longitudinal Prediction of Radiation-Induced Anatomical Changes of Parotid Glands During Radiotherapy Using Deep Learning

Lee

Alam

Nadeem

et al. 2020

Predictive Intelligence in Medicine

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Local Setup Errors in Image-Guided Radiotherapy for Head and Neck Cancer Patients Immobilized With a Custom-Made Device

Cited by 28 publications

References 14 publications

Comparison of Safety Margin Generation Concepts in Image Guided Radiotherapy to Account for Daily Head and Neck Pose Variations

Comparison of Safety Margin Generation Concepts in Image Guided Radiotherapy to Account for Daily Head and Neck Pose Variations

IGRT versus non-IGRT for postoperative head-and-neck IMRT patients: dosimetric consequences arising from a PTV margin reduction

Longitudinal Prediction of Radiation-Induced Anatomical Changes of Parotid Glands During Radiotherapy Using Deep Learning

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