Inter- and Intrafraction Patient Positioning Uncertainties for Intracranial Radiotherapy: A Study of Four Frameless, Thermoplastic Mask-Based Immobilization Strategies Using Daily Cone-Beam CT

Tryggestad, E.; Christian, Matthew; Ford, Eric; Kut, Carmen; Le, Yi; Sanguineti, Giuseppe; Song, Danny Y.; Kleinberg, Lawrence

doi:10.1016/j.ijrobp.2010.06.022

Cited by 112 publications

(110 citation statements)

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“…Guckenberger et al (3) utilized CBCT and Elekta XVI software to measure interfractional positioning errors, whereas Tryggestad et al (5) utilized daily pre‐ and post‐treatment CBCT for these measurements. In Tryggestad's study, we listed the data obtained using their #4 immobilization device, which was their most robust immobilization system and utilized a similar three‐point customized CMB strategy as ours.…”

Section: Discussionmentioning

confidence: 99%

“…CBCT is available on most modern linacs and used for setup verification because of its capability to acquire volumetric images 3 , 4 , 5 , 6 . In‐room orthogonal X‐ray systems, such as the Brainlab ExacTrac X‐ray 6D system (Brainlab AG, Feldkirchen, Germany), are common add‐ons that allow for 6D setup verification and corrections prior to and during treatment 7 , 8 …”

Section: Introductionmentioning

confidence: 99%

“…Compared to stereotactic head frame systems, frameless systems have the advantage of improved patient safety and comfort, with more convenient clinical and technical workflow. The inter‐ and intrafractional setup errors for head and neck patients immobilized with thermoplastic masks have been extensively investigated 5 , 9 , 10 . Other immobilization devices, such as customizable head cushions and mouth pieces, can be coupled to the thermoplastic mask to further restrict patient motion (5) …”

Section: Introductionmentioning

confidence: 99%

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Improved setup and positioning accuracy using a three‐point customized cushion/mask/bite‐block immobilization system for stereotactic reirradiation of head and neck cancer

Wang

Tung

et al. 2016

J Applied Clin Med Phys

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The purpose of this study was to investigate the setup and positioning uncertainty of a custom cushion/mask/bite‐block (CMB) immobilization system and determine PTV margin for image‐guided head and neck stereotactic ablative radiotherapy (HN‐SABR). We analyzed 105 treatment sessions among 21 patients treated with HN‐SABR for recurrent head and neck cancers using a custom CMB immobilization system. Initial patient setup was performed using the ExacTrac infrared (IR) tracking system and initial setup errors were based on comparison of ExacTrac IR tracking system to corrected online ExacTrac X‐rays images registered to treatment plans. Residual setup errors were determined using repeat verification X‐ray. The online ExacTrac corrections were compared to cone‐beam CT (CBCT) before treatment to assess agreement. Intrafractional positioning errors were determined using prebeam X‐rays. The systematic and random errors were analyzed. The initial translational setup errors were −0.8±1.3 mm, −0.8±1.6 mm, and 0.3±1.9 mm in AP, CC, and LR directions, respectively, with a three‐dimensional (3D) vector of 2.7±1.4 mm. The initial rotational errors were up to 2.4° if 6D couch is not available. CBCT agreed with ExacTrac X‐ray images to within 2 mm and 2.5°. The intrafractional uncertainties were 0.1±0.6 mm, 0.1±0.6 mm, and 0.2±0.5 mm in AP, CC, and LR directions, respectively, and 0.0∘±0.5°, 0.0∘±0.6°, and −0.1∘±0.4∘ in yaw, roll, and pitch direction, respectively. The translational vector was 0.9±0.6 mm. The calculated PTV margins normalmPTVfalse(90,95false) were within 1.6 mm when using image guidance for online setup correction. The use of image guidance for online setup correction, in combination with our customized CMB device, highly restricted target motion during treatments and provided robust immobilization to ensure minimum dose of 95% to target volume with 2.0 mm PTV margin for HN‐SABR.PACS number(s): 87.55.ne

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Improved setup and positioning accuracy using a three‐point customized cushion/mask/bite‐block immobilization system for stereotactic reirradiation of head and neck cancer

Wang

Tung

et al. 2016

J Applied Clin Med Phys

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“…Previous studies showed that with the indexed immobilization devices, the patient setup error could be within 0.3 cm. ( 23 – 24 ) Furthermore, an appropriate safety margin between the radiation field edge and metallic frames should be considered when defining the beam arrangement in treatment planning.…”

Section: Discussionmentioning

confidence: 99%

Evaluating and modeling of photon beam attenuation by a standard treatment couch

Dai

et al. 2011

J Applied Clin Med Phys

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The purpose of this study was to evaluate beam attenuation by treatment couch and build a treatment couch model in TPS to check for beam–couch intersection at the planning stage and deal with beam attenuation by treatment couch in dose calculation. In this study, a standard treatment couch, Siemens ZXT couch, has been incorporated into Pinnacle3 8.0 TPS, based on an existing TPS tool, model‐based segmentation (MBS). This was done by generating the couch's model from contours of the couch, together with the density information. Both the geometric and dosimetric accuracy of the couch model were evaluated. The test of beam–couch intersection prediction showed good agreement between predicted and measured results, and the differences were within 1° gantry rotation. For individual posterior oblique beams, the attenuation by metallic frames and PMMA couch top could reach nearly as high as 60% and 10%, respectively. For several posterior oblique beams (180°, 220°, 235°) that attenuated by the PMMA couch top, the calculated and measured dose distributions were compared. The dose differences at central axis were within 1%, and almost all points agreed with the calculations when the DD and DTA criteria of 3%/3 mm were adopted. The difference between calculated and measured attenuation factors were within 0.5%. This study demonstrates that the couch model created by MBS, which contains geometric and density information of the couch, can be used to detect the beam–couch intersection, and also is able to provide an accurate representation of the couch top attenuation properties in patient dose calculation.PACS numbers: 87.55.D‐, 87.55.Gh, 87.55.km

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“…10,11 Furthermore, head immobilization requirements have changed with hypofractionated SRT delivered with the patient's head immobilized in a simple thermoplastic mask. 2,12 This practice does require a planning target volume (PTV) margin, which can be a drawback given the potential for significant increases in the TV and resulting volume of normal brain tissue being irradiated. 13 The benefits of hypofractionated frameless delivery may outweigh the disadvantage of applying a PTV margin and include improved patient comfort and compliance, the ability to dose-escalate and potentially reduce the risk of complications like necrosis due to the advantages of fractionation on the normal brain tissue.…”

Section: Introductionmentioning

confidence: 99%

Investigation of Dose Falloff for Intact Brain Metastases and Surgical Cavities Using Hypofractionated Volumetric Modulated Arc Radiotherapy

Ruschin

Lee

Beachey

et al. 2015

Technol Cancer Res Treat

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Introduction: Intact brain metastases tend to be small and spherical compared to postsurgery brain cavities, which tend to be large and irregular shaped and, as a result, a challenge with respect to treatment planning. The purpose of the present study is to develop guidelines for normal brain tissue dose and to investigate whether there is a dependence on target type for patients treated with hypofractionated volumetric modulated arc radiotherapy (HF-VMAT). Methods: Treatment plans from a total of 100 patients and 136 targets (55 cavity and 81 intact) were retrospectively reviewed. All targets were treated with HF-VMAT with total doses ranging between 20 and 30 gray (Gy) in 5 fractions. All plans met institutional objectives for organ-at-risk constraints and were clinically delivered. Dose falloff was quantified using gradient index (GI) and distance between the 100% and 50% isodose lines (R50). Additionally, the dose to normal brain tissue (brain contour excluding all gross tumor or clinical target volumes) was assessed using volume receiving specific doses (Vx) where x ranged from 5 to 30 Gy. Best-fit curves using power law relationships of the form y ¼ ax b were generated for GI, R50, and Vx (normal brain tissue) versus target volume. Results: There was a statistically significant difference in planning target volume (PTV) for cavities versus intact metastases with mean volumes of 37.8 cm 3 and 9.5 cm 3 , respectively (P < .0001). The GI and R50 were statistically different: 3.4 and 9.8 mm for cavities versus 4.6 and 8.3 mm for intact metastases (P < .0001). The R50 increased with PTV with power law coefficients (a, b) ¼ (6.3, 0.12) and (5.9, 0.15) for cavities and intact, respectively. GI decreased with PTV with coefficients (a, b) ¼ (5.9, À0.18) and (5.7, À0.14) for cavities and intact, respectively. The normal brain tissue Vx also exhibited power law relationships with PTV for x ¼ 20 to 28.8 Gy.In conclusion, target volume is the main predictor of dose falloff. The results of the present study can be used for determining target volume-based thresholds for dose falloff and normal brain tissue dose-volume constraints.Keywords hypofractionated VMAT, brain, stereotactic radiosurgery, treatment planning Abbreviations CBCT, cone beam computed tomography; CI, conformity index; CT, computed tomography; CTV, clinical target volume; GI, gradient index; GTV, gross tumor volume; Gy, gray; HF-VMAT, hypofractionated volumetric modulated arc radiotherapy; HI, heterogeneity index; IMRT, intensity modulated radiation therapy; MD, maximum dose; MLC, multileaf collimator; MU, monitor unit; OAR, organ at risk; PD, prescribed dose; PIV, prescription isodose volume; PIV half , volume of 50% of the prescription isodose; PTV, planning target volume; QA, quality assurance; R50, radial difference between equivalent spherical volumes corresponding to the 100% and 50% isodose lines; R Eq (V), radius of an equivalent sphere with volume V; RI, regularity index; RTOG, radiation therapy oncology group; SRS, stereotactic radiosurg...

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Inter- and Intrafraction Patient Positioning Uncertainties for Intracranial Radiotherapy: A Study of Four Frameless, Thermoplastic Mask-Based Immobilization Strategies Using Daily Cone-Beam CT

Cited by 112 publications

References 11 publications

Improved setup and positioning accuracy using a three‐point customized cushion/mask/bite‐block immobilization system for stereotactic reirradiation of head and neck cancer

Improved setup and positioning accuracy using a three‐point customized cushion/mask/bite‐block immobilization system for stereotactic reirradiation of head and neck cancer

Evaluating and modeling of photon beam attenuation by a standard treatment couch

Investigation of Dose Falloff for Intact Brain Metastases and Surgical Cavities Using Hypofractionated Volumetric Modulated Arc Radiotherapy

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