Assessment and characterization of the total geometric uncertainty in Gamma Knife radiosurgery using polymer gels

Moutsatsos, A.; Karaiskos, P.; Petrokokkinos, L.; Sakelliou, L.; Pantelis, E.; Georgiou, Evangelos; Torrens, Michael; Seimenis, Ioannis

doi:10.1118/1.4789922

Cited by 25 publications

(71 citation statements)

References 54 publications

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“… 17 In this work, in contrast to our previous studies 8 , 17 , 25 where the reversed gradient technique 3 , 4 , 17 , 19 , 20 , 25 – 27 was used to distinguish and characterize different sources of system-related geometric distortion (including those induced by stereotactic accessories such as the immobilization frame used in Gamma Knife SRS applications 17 ), distortion assessment relied entirely on 1 MR scan, as has been demonstrated elsewhere. 5 – 7 , 28 , 29 Consequently, both sequence-independent (ie, arising from gradient nonlinearity) and sequence-dependent distortions 3 , 25 , 30 , 31 (ie, distortions related to B 0 inhomogeneity, chemical shift artifacts, and susceptibility differences) were taken into account. However, chemical shift artifacts are not relevant in a phantom study, while susceptibility-induced distortions (stemming from acrylic-copper sulfate solution susceptibility difference) are uniform throughout the entire geometry and, inevitably, cancel out during the spatial registration step.…”

Section: Discussionmentioning

confidence: 99%

MRI-Related Geometric Distortions in Stereotactic Radiotherapy Treatment Planning: Evaluation and Dosimetric Impact

Pappas

Alshanqity

Moutsatsos

et al. 2017

Technol Cancer Res Treat

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In view of their superior soft tissue contrast compared to computed tomography, magnetic resonance images are commonly involved in stereotactic radiosurgery/radiotherapy applications for target delineation purposes. It is known, however, that magnetic resonance images are geometrically distorted, thus deteriorating dose delivery accuracy. The present work focuses on the assessment of geometric distortion inherent in magnetic resonance images used in stereotactic radiosurgery/radiotherapy treatment planning and attempts to quantitively evaluate the consequent impact on dose delivery. The geometric distortions for 3 clinical magnetic resonance protocols (at both 1.5 and 3.0 T) used for stereotactic radiosurgery/radiotherapy treatment planning were evaluated using a recently proposed phantom and methodology. Areas of increased distortion were identified at the edges of the imaged volume which was comparable to a brain scan. Although mean absolute distortion did not exceed 0.5 mm on any spatial axis, maximum detected control point disposition reached 2 mm. In an effort to establish what could be considered as acceptable geometric uncertainty, highly conformal plans were utilized to irradiate targets of different diameters (5-50 mm). The targets were mispositioned by 0.5 up to 3 mm, and dose–volume histograms and plan quality indices clinically used for plan evaluation and acceptance were derived and used to investigate the effect of geometrical uncertainty (distortion) on dose delivery accuracy and plan quality. The latter was found to be strongly dependent on target size. For targets less than 20 mm in diameter, a spatial disposition of the order of 1 mm could significantly affect (>5%) plan acceptance/quality indices. For targets with diameter greater than 2 cm, the corresponding disposition was found greater than 1.5 mm. Overall results of this work suggest that efficacy of stereotactic radiosurgery/radiotherapy applications could be compromised in case of very small targets lying distant from the scanner’s isocenter (eg, the periphery of the brain).

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Section: Discussionmentioning

confidence: 99%

MRI-Related Geometric Distortions in Stereotactic Radiotherapy Treatment Planning: Evaluation and Dosimetric Impact

Pappas

Alshanqity

Moutsatsos

et al. 2017

Technol Cancer Res Treat

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“…Other sources, such as static field inhomogeneity and eddy currents are also known to affect image accuracy, and these are generally dependent on the sequence used and the nature of the tissue interfaces imaged, whereas gradient non-linearity is a function of the MR system itself, regardless of the sequence chosen [4,5]. Efforts to address sequence-specific distortion have had some success though residual distortion is often dominated by effects of gradient non-linearity [16,19,29,34,35]. The present investigation focuses on the clinical significance of gradient non-linearity effects because correction of this source of inaccuracy has not been widely adopted in clinical practice [16,17].…”

Section: Discussionmentioning

confidence: 99%

Distortion Inherent to Magnetic Resonance Imaging (MRI) Can Lead to Geometric Miss in Radiosurgery Planning

Seibert

White

Kim

et al. 2014

International Journal of Radiation Oncology*Biology*Physics

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“…Traditional frame‐based GK utilizing the indicator box localization has been used successfully for decades in the treatment of thousands of cranial targets . Generally, system accuracy literature for this workflow has reported very lower error between 0.5 and 1 mm though with possible exceptions of up to 1.6 mm in special circumstances . The confidence in this technique is high, but also the error margin is small as a “tolerable” accuracy limit has been proposed of 1.3 mm with emphasis that smaller is still better .…”

Section: Sources Of Uncertaintymentioning

confidence: 99%

Gamma Knife^® icon CBCT offers improved localization workflow for frame‐based treatment

Duggar

Morris

Fatemi

et al. 2019

J Applied Clin Med Phys

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Object: The purpose of this study was to compare two methods of stereotactic localization in Gamma Knife treatment planning: cone beam computed tomography (CBCT) or fiducial. While the fiducial method is the traditional method of localization, CBCT is now available for use with the Gamma Knife Icon. This study seeks to determine whether a difference exists between the two methods and then whether one is better than the other regarding accuracy and workflow optimization.Methods: Cone beam computed tomography was used to define stereotactic space around the Elekta Film Pinprick phantom and then treated with film in place. The same phantom was offset known amounts from center and then imaged with CBCT and registered with the reference CBCT image to determine if measured offsets matched those known. Ten frameless and 10 frame-based magnetic resonance imaging (MRI) to CBCT patient fusions were retrospectively evaluated using the TG-132 TRE method. The stereotactic coordinates defined by CBCT and traditional fiducials were compared on the Elekta 8 cm Ball phantom, an anthropomorphic phantom, and actual patient data. Offsets were introduced to the anthropomorphic phantom in the stereotactic frame and CBCT's ability to detect those offsets was determined.Results: Cone beam computed tomography defines stereotactic space well within the established limits of the mechanical alignment system. The CBCT to CBCT registration can detect offsets accurately to within 0.1 mm and 0.5°. In all cases, some disagreement existed between fiducial localization and that of CBCT which in some cases was small, but also was as high as 0.43 mm in the phantom domain and as much as 1.54 mm in actual patients. Conclusion:Cone beam computed tomography demonstrates consistent accuracy in defining stereotactic space. Since both localization methods do not agree with each other consistently, the more reliable method must be identified. Cone beam computed tomography can accurately determine offsets occurring within stereotactic space that would be nondiscernible utilizing the fiducial method and seems to be more reliable. Using CBCT localization offers the opportunity to streamline workflow

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Assessment and characterization of the total geometric uncertainty in Gamma Knife radiosurgery using polymer gels

Cited by 25 publications

References 54 publications

MRI-Related Geometric Distortions in Stereotactic Radiotherapy Treatment Planning: Evaluation and Dosimetric Impact

MRI-Related Geometric Distortions in Stereotactic Radiotherapy Treatment Planning: Evaluation and Dosimetric Impact

Distortion Inherent to Magnetic Resonance Imaging (MRI) Can Lead to Geometric Miss in Radiosurgery Planning

Gamma Knife^® icon CBCT offers improved localization workflow for frame‐based treatment

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Assessment and characterization of the total geometric uncertainty in Gamma Knife radiosurgery using polymer gels

Cited by 25 publications

References 54 publications

MRI-Related Geometric Distortions in Stereotactic Radiotherapy Treatment Planning: Evaluation and Dosimetric Impact

MRI-Related Geometric Distortions in Stereotactic Radiotherapy Treatment Planning: Evaluation and Dosimetric Impact

Distortion Inherent to Magnetic Resonance Imaging (MRI) Can Lead to Geometric Miss in Radiosurgery Planning

Gamma Knife® icon CBCT offers improved localization workflow for frame‐based treatment

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Product

Resources

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Gamma Knife^® icon CBCT offers improved localization workflow for frame‐based treatment