Cone Beam Computed Tomography Image Guidance System for a Dedicated Intracranial Radiosurgery Treatment Unit

Ruschin, Mark; Komljenovic, Philip T.; Ansell, Steve; Ménard, Cynthia; Bootsma, G; Cho, Young Bin; Chung, Caroline; Jaffray, David A.

doi:10.1016/j.ijrobp.2012.03.022

Cited by 37 publications

(37 citation statements)

References 19 publications

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“…As shown in Table 2, cases exceeding such thresholds can be replanned in order to bring them in closer to guideline values. Similarly, for targets less than 30 cm 3 , we expect normal brain tissue V28.8 < 16 cm 3 , V25 < 24 cm 3 , and V20 < 38 cm 3 . Special considerations for targets overlapping with OARs are also factored in when evaluating plans, as data for dose falloff (GI or R50) deviate more often from best-fit curves as shown in Figure 2.…”

Section: Discussionmentioning

confidence: 79%

“…17 Although the present work is hypofractionated and considers much larger TVs, their GI outcomes were approximately 4.7, which is consistent with our GI outcomes for small lesions (Figure 2). Similarly, Audet et al report their findings for VMAT using up to 6 noncoplanar arcs in series of 12 patients receiving single fraction SRS for relatively small isolated lesions (max 29 cm 3 ). 28 The study by Audet et al typically used multiple isocenters if any target was greater than 3.5 cm away from an isocenter, which is an approach similar to ours.…”

Section: Discussionmentioning

confidence: 90%

“…These results have established in-house guidelines as a benchmark for treatment planning quality; in particular, our clinical outcomes for local control and radiation necrosis are consistent with expected outcomes. 23 For example, for targets less than 30 cm 3 , we strive to achieve R50 less than 8 mm, otherwise, we strive for R50 less than 10 mm. As shown in Table 2, cases exceeding such thresholds can be replanned in order to bring them in closer to guideline values.…”

Section: Discussionmentioning

confidence: 99%

“…We recorded the mean dose for each prescription level as well as the volume (cm 3 ) receiving x (Vx, Gy), which is defined as the absolute volume of tissue (in cm 3 ) receiving dose x or above, where x ranges from 5 Gy up to 30 Gy. A value of x ¼ 28.8 Gy was included since it is equivalent to 14 Gy in single fraction based on the linear-quadratic model and has been implicated to be correlated with increased risk of necrosis in a single report.…”

Section: Reported Metrics For Normal Brain Tissuementioning

confidence: 99%

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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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Section: Discussionmentioning

confidence: 79%

Section: Discussionmentioning

confidence: 90%

Section: Discussionmentioning

confidence: 99%

Section: Reported Metrics For Normal Brain Tissuementioning

confidence: 99%

See 2 more Smart Citations

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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“…These systems involve placing the patient in a thermoplastic mask, performing a cone beam CT prior to every treatment, and then using registration software to match the CT simulation to the cone beam CT. The translational and rotational shifts generated by the matching algorithm are then physically applied to the treatment couch to further refine the target alignment, achieving millimeter to sub-millimeter accuracy (Tryggestad et al, 2011;Ohtakara et al, 2012;Rosenfelder et al, 2013;Ruschin et al, 2013).…”

Section: Evolution Of Fractionated Radiotherapy Technologymentioning

confidence: 99%

Linear Accelerator-Based Fractionated Radiotherapy

Ali

2015

Craniopharyngiomas

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Cone‐Beam CT image contrast and attenuation‐map linearity improvement (CALI) for brain stereotactic radiosurgery procedures

Hashemi

Huynh

Sahgal

et al. 2018

J Applied Clin Med Phys

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A Contrast and Attenuation‐map Linearity Improvement (CALI) framework is proposed for cone‐beam CT (CBCT) images used for brain stereotactic radiosurgery (SRS). The proposed framework is tailored to improve soft tissue contrast of a new point‐of‐care image‐guided SRS system that employs a challenging half cone beam geometry, but can be readily reproduced on any CBCT platform. CALI includes a pre‐ and post‐processing step. In pre‐processing we apply a shading and beam hardening artifact correction to the projections, and in post‐processing step we correct the dome/capping artifact on reconstructed images caused by the spatial variations in X‐ray energy generated by the bowtie‐filter. The shading reduction together with the beam hardening and dome artifact correction algorithms aim to improve the linearity and accuracy of the CT‐numbers (CT#). The CALI framework was evaluated using CatPhan to quantify linearity, contrast‐to‐noise (CNR), and CT# accuracy, as well as subjectively on patient images acquired on a clinical system. Linearity of the reconstructed attenuation‐map was improved from 0.80 to 0.95. The CT# mean absolute measurement error was reduced from 76.1 to 26.9 HU. The CNR of the acrylic insert in the sensitometry module was improved from 1.8 to 7.8. The resulting clinical brain images showed substantial improvements in soft tissue contrast visibility, revealing structures such as ventricles which were otherwise undetectable in the original clinical images obtained from the system. The proposed reconstruction framework also improved CT# accuracy compared to the original images acquired on the system. For frameless image‐guided SRS, improving soft tissue visibility can facilitate evaluation of MR to CBCT co‐registration. Moreover, more accurate CT# may enable the use of CBCT for daily dose delivery measurements.

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Cone Beam Computed Tomography Image Guidance System for a Dedicated Intracranial Radiosurgery Treatment Unit

Cited by 37 publications

References 19 publications

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

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

Linear Accelerator-Based Fractionated Radiotherapy

Cone‐Beam CT image contrast and attenuation‐map linearity improvement (CALI) for brain stereotactic radiosurgery procedures

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