scholarly journals Evaluation of the Efficacy of Rotational Corrections for Standard-Fractionation Head and Neck Image-Guided Radiotherapy

2019 ◽  
Vol 18 ◽  
pp. 153303381985382 ◽  
Author(s):  
Joseph S. Kung ◽  
William T. Tran ◽  
Ian Poon ◽  
Eshetu G. Atenafu ◽  
Lorraine Courneyea ◽  
...  
Keyword(s):  
Head And Neck ◽  
Degrees Of Freedom ◽  
Mixed Model ◽  
Intensity Modulated Radiotherapy ◽  
Target Volume ◽  
Cone Beam ◽  
Positional Accuracy ◽  
Image Guided Radiotherapy ◽  
Intensity Modulated ◽  
6 Degrees Of Freedom

Purpose: Modern linear accelerators are equipped with cone beam computed tomography and robotic couches that can correct for errors in the translational (X, Y, Z) and rotational (α, β, γ) axes prior to treatment delivery. Here, we compared the positional accuracy of 2 cone beam registration approaches: (1) employing translational shifts only in 3 degrees of freedom (X, Y, Z), versus; (2) using translational-rotational shifts in 6 degrees of freedom (X, Y, Z, α, β, γ). Methods: This retrospective study examined 140 interfraction cone beam images from 20 patients with head and neck cancer treated with standard intensity-modulated radiation therapy. The cone beam images were matched to planning simulation scans in 3, then in 6 degrees of freedom, using the mandible, clivus, and C2 and C7 vertebrae as surrogate volumes. Statistical analyses included a generalized mixed model and was used to assess whether there were significant differences in acceptable registrations between the 2 correction methods. Results: The rates of improvement with corrections in 6 degrees of freedom for the mandible with a 5-mm expansion margin were 54.55% ( P = .793), for the clivus 85.71% ( P = .222), and for C7 87.50% ( P = .015). There was a 100% increase in acceptability for the C2 vertebra within the 5-mm margin ( P < .001). For the 3-mm expansion margin, the rates of improvement for the mandible, clivus, C2, and C7 were 63.16% ( P = .070), 91.30% ( P = .011), 84.21% ( P = .027), and 76.92% ( P < .001), respectively. Conclusions: Significant registration improvements with the use of rotational corrections with a 5-mm expansion margin are only seen in the C7 vertebra. At the 3-mm margin, significant improvements are found for the C2, C7, and clivus registrations, suggesting that intensity-modulated radiotherapy treatments for head and neck cancers with 3-mm planning target volume margins may benefit from corrections in 6 degrees of freedom.

scholarly journals Evaluation of interfraction patient setup errors for image-guided prostate and head-and-neck radiotherapy using kilovoltage cone beam and megavoltage fan beam computed tomography

2013 ◽  
Vol 12 (4) ◽  
pp. 334-343 ◽  
Author(s):  
X. Sharon Qi ◽  
Sutan Wu ◽  
Francis Newman ◽  
X. Allen Li ◽  
Angie Y. Hu
Keyword(s):  
Computed Tomography ◽  
Head And Neck ◽  
Target Volume ◽  
Cone Beam ◽  
Setup Errors ◽  
Image Guided Radiotherapy ◽  
Image Guided ◽  
Significant Difference ◽  
Late Stages ◽  
Head And Neck Radiotherapy

AbstractPurposeTo analyse interfraction setup using two different image guidance modalities for prostate and head-and-neck (H&N) cancer treatment.Materials and methodsSeventy-two prostate and 60 H&N cancer patients, imaged with kilovoltage cone beam computed tomography (KVCBCT) or megavoltage fan beam computed tomography (MVFBCT), were studied retrospectively. The daily displacements in mediolateral (ML), craniocaudal (CC) and anteroposterior (AP) dimensions were investigated. The setup errors were calculated to determine the clinical target volume to planning target volume (CTV-to-PTV) margins.ResultsBased on 1,606 KVCBCT and 2,054 MVFBCT scans, average interfraction shifts in ML, CC and AP direction for H&N cases were 0·5 ± 1·5, −0·3 ± 2·0, 0·3 ± 1·7 mm using KVCBCT, 0·2 ± 1·9, −0·2 ± 2·4 and 0·0 ± 1·7 mm using MVFBCT. For prostate cases, average interfraction displacements were −0·3 ± 3·9, 0·2 ± 2·4, 0·4 ± 3·8 mm for MVFBCT and −0·2 ± 2·7, −0·6 ± 2·9, −0·5 ± 3·4 mm for KVCBCT. The calculated CTV-to-PTV margins, if determined by image-guided radiotherapy (IGRT) data, were 5·6 mm (H&N) and 7·8 mm (prostate) for MVFBCT, compared with 4·8 mm and 7·2 mm for KVCBCT. We observed no statistically significant difference in daily repositioning using KVCBCT and MVFBCT in early, middle and late stages of the treatment course.ConclusionIn the absence of IGRT, the CTV-to-PTV margin determined using IGRT data, may be varied for different imaging modalities for prostate and H&N irradiation.

Review of Monoisocentric Split-Field Technique for Conventional and IMRT Treatment in Head and Neck Cancers: Technical Limitations and Approaches for Optimization

2005 ◽  
Vol 4 (1) ◽  
pp. 107-113 ◽  
Author(s):  
Khaled Abdel-Hakim ◽  
Tetsuo Nishimura ◽  
Michikatsu Takai ◽  
Harumi Sakahara
Keyword(s):  
Head And Neck ◽  
Intensity Modulated Radiotherapy ◽  
Target Volume ◽  
Head And Neck Cancers ◽  
Random Errors ◽  
Field Technique ◽  
Intensity Modulated ◽  
Field Matching ◽  
Split Field ◽  
Lower Neck

The importance of treatment planning of head and neck malignancies arises from the necessity to achieve homogenous doses to localized target volume surrounded by normal structures, which can produce acute and long-term morbidity. In many radiotherapy departments, a commonly employed strategy is a 3-field technique. Bilateral parallel-opposed fields are matched to anterior lower neck field. In recent years, Intensity Modulated Radiotherapy (IMRT) is used to radiate head and neck tumors. When the target extends to the lower neck regions, abutment of upper IMRT and lower neck fields is required. Field matching represents a technical challenge for the medical physicist, medical engineer, and radiation oncologist to treat multiple fields while avoiding their overlap on the spinal cord. The monoisocentric split field technique has recently become a common technique to achieve matchline homogenous dose while respecting normal tissue tolerance. The aim of this work is to review merits, limitations, and recent approaches to optimize matchline dose in monoisocentric technique in conventional and intensity modulated radiotherapy for head and neck cancers. Although the technique has many advantages, it is subjected to some systematic and random errors due to equipment and patient setup inaccuracies. To decrease the magnitude of matchline inhomogeneities, customized penumbra generator or multileaf collimator have been used. Both methods are viable and represent alternative approaches to the problem of field matching using the asymmetric jaws.

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