Rotation of the Sacrum During Bellyboard Pelvic Radiotherapy

Kasabašić, Mladen; Faj, Dario; Ivković, Ana; Jurković, Slaven; Belaj, Nenad

doi:10.1016/j.meddos.2009.01.001

Cited by 15 publications

(13 citation statements)

References 4 publications

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“…Laursen et al already investigated residual rotations in cervix patients and their results were comparable with the ones of this study in particular with regard to pitch induced shifts [17]. Shifts related to rotation have been reported to be larger (up to 15 mm) in prone patients positioned with a belly-board [28]. Residual rotational errors after translational couch corrections were found to be of Σ = 5.1/ 5.5 mm in the AP direction in the L4/L5 region in a study by Ahmad et al [16].…”

Section: Discussionsupporting

confidence: 88%

Robustness of elective lymph node target coverage with shrinking Planning Target Volume margins in external beam radiotherapy of locally advanced cervical cancer

Berger

Fokdal

Assenholt

et al. 2019

Physics and Imaging in Radiation Oncology

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Background and purpose: Image-Guidance decreases setup uncertainties, which may allow for Planning Target Volume (PTV) margins reduction. This study evaluates the robustness of the elective lymph node target coverage to translational and rotational setup errors in combination with shrinking PTV margins and determines the gain for the Organs At Risk (OARs). Material and methods: Ten cervix cancer patients who underwent external beam radiotherapy with 45 Gy/25Fx were analysed. Daily Image-Guidance was based on bony registration of Cone Beam CT (CBCT) to planning CT (pCT) and daily couch correction (translation and yaw). On each pCT, four Volumetric Modulated Arc Therapy dose-plans were generated with PTV margins of 0, 3, 5 and 8 mm. The elective clinical target volume (CTV-E) was propagated from daily CBCTs to the pCT to evaluate daily CTV-E dose. Additional systematic translational isocenter shifts of 2 mm were simulated. D98% (dose received by 98% of the volume of interest) and D99.9% were extracted from each CTV-E for all dose-plans and scenarios. Total dose was accumulated by Dose-Volume Histogram addition. The dosimetric impact of PTV margin reduction on the OARs was evaluated through V30Gy (volume included within the 30 Gy isodose), V40Gy and body V43Gy. Results: When decreasing the PTV margin from 5 to 0 mm, bowel V30Gy was decreased by 13% (from 247 cm 3 to 214 cm 3), body V43Gy by 19% (from 1462 cm 3 to 1188 cm 3) and PTV by 39% (from 1416 to 870 cm 3). The dosimetric impact of combined systematic shifts and residual rotations on the elective target with a 0 mm PTV margin was a decrease of D98% (mean ± SD) from 44.1 Gy ± 0.4 Gy to 43.7 Gy ± 0.8 Gy and a minimum of 42.4 Gy. Conclusion: PTV margin reduction from 5 to 0 mm induced significant OARs dosimetric gains while elective target coverage remained robust to positioning uncertainties.

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Section: Discussionsupporting

confidence: 88%

Robustness of elective lymph node target coverage with shrinking Planning Target Volume margins in external beam radiotherapy of locally advanced cervical cancer

Berger

Fokdal

Assenholt

et al. 2019

Physics and Imaging in Radiation Oncology

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“… 8 In addition, prone with belly board has larger mean positioning errors compared to prone without, with the greatest difference in the AP direction (4.4 vs 2.3 mm). 8 , 27 Belly board setup is also susceptible to differences in rotation of the pelvis: a study 28 found that the sacrum-to-S1-vertebra angle varies by approximately ±10° over multiple fxs and may drift over the course of treatment.…”

Section: Resultsmentioning

confidence: 99%

In vivo Portal Imaging Dosimetry Identifies Delivery Errors in Rectal Cancer Radiotherapy on the Belly Board Device

Peca

Sinha

Brown

et al. 2017

Technol Cancer Res Treat

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Purpose:We recently developed a novel, open-source in vivo dosimetry that uses the electronic portal imaging device to detect dose delivery discrepancies. We applied our method on patients with rectal cancer treated on a belly board device.Methods: In vivo dosimetry was performed on 10 patients with rectal cancer treated prone on the belly board with a 4-field box arrangement. Portal images were acquired approximately once per week from each treatment beam. Our dosimetry method used these images along with the planning CT to reconstruct patient planar dose at isocenter depth.Results:Our algorithm proved sensitive to dose discrepancies and detected discordances in 7 patients. The majority of these were due to soft tissue differences between planning and treatment, present despite matching to bony anatomy. As a result of this work, quality assurance procedures have been implemented for our immobilization devices.Conclusion: In vivo dosimetry is a powerful quality assurance tool that can detect delivery discrepancies, including changes in patient setup and position. The added information on actual dose delivery may be used to evaluate equipment and process quality and to guide for adaptive radiotherapy.

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“…In our center, patients were treated in supine position and fixed with HipFix baseplate and thermoplastic trunk mask immobilization system. Although prone position has been shown to reduce small bowel within the treatment field 15 , 16 , it is also associated with considerable set-up errors (up to 15 mm) caused by pitch sacral rotations (-14°to 11.5°) 17 . Siddiqui et al 18 analyzed prone and supine patient setup errors.…”

Section: Discussionmentioning

confidence: 99%

How much margin do we need for pelvic lymph nodes irradiation in the era of IGRT?

Liu

Zhang

et al. 2018

J. Cancer

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Background and purpose: Image guided radiotherapy (IGRT) without 6 degree of freedom couch can only correct the translational setup errors of pelvic radiotherapy. But errors introduced by rotation and deformation of CTV can't be adjusted in most of IGRT systems. This article is to evaluate these errors and to provide recommendations on the margin needed in the era of IGRT.Material and methods: 218 patients who received pelvic radiotherapy in PUMC Hospital from 2012 to 2014 were included. A simulation CT and a CBCT were acquired for every patient. 3D and 6D registrations of CT and CBCT were applied. 9 bony landmarks were marked and distances of each landmark between CT and CBCT were measured in three directions.Results: Without image guidance, movements of landmarks in the directions of LR, AP and SI were 0.4 ± 2.5 mm, 1.3 ± 3.8 mm and 1.5 ± 5.0 mm respectively, with 3D-registration, movements were 0.0 ± 1.5 mm, 0.7± 2.8 mm and 0.6± 3.2 mm, and with 6D-registration, movements were 0.0 ± 0.5 mm, 0.2 ± 1.0 mm and 0.2 ± 1.1 mm in each direction.Conclusions: IGRT could reduce setup errors. IGRT with 6D treatment couches could further reduce setup errors compared to 3D couches. For centers without IGRT, we suggest CTV-PTV margins of 6 mm, 9 mm and 12 mm in LR, AP and SI directions respectively, margins of 3 mm, 6.5 mm and 7 mm for the use of daily IGRT with 3D couch and 2 mm, 3 mm and 3 mm for 6D couch.

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Rotation of the Sacrum During Bellyboard Pelvic Radiotherapy

Cited by 15 publications

References 4 publications

Robustness of elective lymph node target coverage with shrinking Planning Target Volume margins in external beam radiotherapy of locally advanced cervical cancer

Robustness of elective lymph node target coverage with shrinking Planning Target Volume margins in external beam radiotherapy of locally advanced cervical cancer

In vivo Portal Imaging Dosimetry Identifies Delivery Errors in Rectal Cancer Radiotherapy on the Belly Board Device

How much margin do we need for pelvic lymph nodes irradiation in the era of IGRT?

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