Impact of Residual Setup Error on Parotid Gland Dose in Intensity-Modulated Radiation herapy with or without Planning Organ-at-Risk Margin

Delana, Anna; Menegotti, L.; Bolner, Andrea; Tomio, L.; Valentini, A.; Lohr, Frank; Vanoni, Valentina

doi:10.1007/s00066-009-1888-9

Cited by 16 publications

(17 citation statements)

References 26 publications

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“…This increase in mean parotid dose was due to both uncertainties in patient set-up and radiation-induced reduction in tumour and parotid volumes, with a medial shift of the parotids' centre of volumes into the high-dose region [52,[56][57][58]. The effect of set-up uncertainties on the parotid dose distribution can be reduced via the use of daily image-guided radiotherapy (IGRT) or the addition of a PRV margin [59,60]. Adaptive radiotherapy (ART) can also result in more effective sparing of the parotid gland by taking tumour and normal tissue changes into account, with subsequent modification of the original IMRT plans [61].…”

Section: Dosimetric Impact Of Interobserver Variation In Parotid Glanmentioning

confidence: 99%

Interobserver variation in parotid gland delineation: a study of its impact on intensity-modulated radiotherapy solutions with a systematic review of the literature

Loo

Martin²,

Smith³

et al. 2012

The British Journal of Radiology

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Objectives: This study evaluates the interobserver variation in parotid gland delineation and its impact on intensity-modulated radiotherapy (IMRT) solutions. Methods: The CT volumetric data sets of 10 patients with oropharyngeal squamous cell carcinoma who had been treated with parotid-sparing IMRT were used. Four radiation oncologists and three radiologists delineated the parotid gland that had been spared using IMRT. The dose-volume histogram (DVH) for each study contour was calculated using the IMRT plan actually delivered for that patient. This was compared with the original DVH obtained when the plan was used clinically. Results: 70 study contours were analysed. The mean parotid dose achieved during the actual treatment was within 10% of 24 Gy for all cases. Using the study contours, the mean parotid dose obtained was within 10% of 24 Gy for only 53% of volumes by radiation oncologists and 55% of volumes by radiologists. The parotid DVHs of 46% of the study contours were sufficiently different from those used clinically, such that a different IMRT plan would have been produced. Conclusion: Interobserver variation in parotid gland delineation is significant. Further studies are required to determine ways of improving the interobserver consistency in parotid gland definition.

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Section: Dosimetric Impact Of Interobserver Variation In Parotid Glanmentioning

confidence: 99%

Interobserver variation in parotid gland delineation: a study of its impact on intensity-modulated radiotherapy solutions with a systematic review of the literature

Loo

Martin²,

Smith³

et al. 2012

The British Journal of Radiology

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“…Numerous publications have suggested appropriate PTV and PRV margins for three‐dimensional conformal and intensity‐modulated radiation therapy, ranging from 2‐5 mm for head and neck, depending on immobilization and frequency of image guidance 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 and 3‐10 mm for prostate depending on frequency of image guidance 33 , 34 , 35 . Some authors have suggested the conventional 5 mm margin for head and neck is conservative and margin reduction may be possible, 24 , 25 , 27 , 29 but others have reported local setup uncertainties meet or exceed 5 mm 26 , 28 , 36 …”

Section: Discussionmentioning

confidence: 99%

Deformable image registration and interobserver variation in contour propagation for radiation therapy planning

Riegel

Antone

Zhang

et al. 2016

J Applied Clin Med Phys

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Deformable image registration (DIR) and interobserver variation inevitably introduce uncertainty into the treatment planning process. The purpose of the current work was to measure deformable image registration (DIR) errors and interobserver variability for regions of interest (ROIs) in the head and neck and pelvic regions. Measured uncertainties were combined to examine planning margin adequacy for contours propagated for adaptive therapy and to assess the trade‐off of DIR and interobserver uncertainty in atlas‐based automatic segmentation. Two experienced dosimetrists retrospectively contoured brainstem, spinal cord, anterior oral cavity, larynx, right and left parotids, optic nerves, and eyes on the planning CT (CT1) and attenuation‐correction CT of diagnostic PET/CT (CT2) for 30 patients who received radiation therapy for head and neck cancer. Two senior radiation oncology residents retrospectively contoured prostate, bladder, and rectum on the postseed‐implant CT (CT1) and planning CT (CT2) for 20 patients who received radiation therapy for prostate cancer. Interobserver variation was measured by calculating mean Hausdorff distances between the two observers' contours. CT2 was deformably registered to CT1 via commercially available multipass B‐spline DIR. CT2 contours were propagated and compared with CT1 contours via mean Hausdorff distances. These values were summed in quadrature with interobserver variation for margin analysis and compared with interobserver variation for statistical significance using two‐tailed t‐tests for independent samples (α=0.05). Combined uncertainty ranged from 1.5‐5.8 mm for head and neck structures and 3.1‐3.7 mm for pelvic structures. Conventional 5 mm margins may not be adequate to cover this additional uncertainty. DIR uncertainty was significantly less than interobserver variation for four head and neck and one pelvic ROI. DIR uncertainty was not significantly different than interobserver variation for four head and neck and one pelvic ROI. DIR uncertainty was significantly greater than interobserver variation for two head and neck and one pelvic ROI. The introduction of DIR errors may offset any reduction in interobserver variation by using atlas‐based automatic segmentation.PACS number(s): 87.57.nj, 87.55.D‐

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“…Currently, CBCT images are compared with original treatment plans for the most accurate positioning setup [5,6,9,10,14,17,18,25,28].…”

Section: Phase-specific Cone Beam Computed Tomography Reduces Reconstmentioning

confidence: 99%

Phase-specific cone beam computed tomography reduces reconstructed volume loss of moving phantom

Chao

Chen²,

et al. 2011

Strahlenther Onkol

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Impact of Residual Setup Error on Parotid Gland Dose in Intensity-Modulated Radiation herapy with or without Planning Organ-at-Risk Margin

Cited by 16 publications

References 26 publications

Interobserver variation in parotid gland delineation: a study of its impact on intensity-modulated radiotherapy solutions with a systematic review of the literature

Interobserver variation in parotid gland delineation: a study of its impact on intensity-modulated radiotherapy solutions with a systematic review of the literature

Deformable image registration and interobserver variation in contour propagation for radiation therapy planning

Phase-specific cone beam computed tomography reduces reconstructed volume loss of moving phantom

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