<abstract xmlns="http://www.w3.org/1999/xhtml"><p>The purpose of the study was to analyze single fraction Gamma Knife stereotactic radiosurgery (SRS) for uveal melanoma (UM). In the treatment of UMs, the dose distribution exhibited by an irregular eye surface has more calculation uncertainty. A tissue-equivalent bolus was placed on the left eye surface of a human head-shaped phantom. It was assumed that the treated eye is fixed using retrobulbar anesthesia and suture on extraocular muscles for phantom study. Leksell stereotactic frame was fixed around phantom’s head and the stereotactic computed tomography (CT) was performed. Two sets of scans were acquired (a) without bolus and (b) with a bolus of 1.0 cm thickness. These scans were transferred into a treatment planning system (TPS). The skull contouring was performed using stereotactic CT images. The target, visual pathways, and eye lens were delineated in stereotactic CT space created on TPS. A clinical relevant plan was designed on the CT study set “a” to deliver a radiation dose of 30Gy at tumor margin. The plan superimposed over CT study set “b” and compiled for convincing treatment strategy. The tumor coverage was 95% at 50% prescription isodose line. The conformity index, selectivity and the gradient index were 1.27, 0.80 and 3.28 respectively. The left optic nerve and eye lens received a maximum dose of 11.1 Gy and 11.0 Gy respectively. The treatment plan overlay showed similar planning indices and critical organ doses. The plan comparison showed: an irradiated volume received the radiation dose > 15 Gy varies &lt; 1.0% whereas the volume received &lt; 15 Gy were larger (> 1.0%) in the study set “b”. The distant lateral points from the target volume which describe the phantom’s eyelid showed a radiation dose of 3.2 Gy - 2.5 Gy. The doses to these points were misled and ignored in the CT study set “a”. The eye bolus provides better dosimetric information in the estimation of low dose areas which is commonly misled on TPS in SRS planning for UMs.</p></abstract>

The purpose of the study was to analyze single fraction Gamma Knife stereotactic radiosurgery (SRS) for uveal melanoma (UM). In the treatment of UMs, the dose distribution exhibited by an irregular eye surface has more calculation uncertainty. A tissue-equivalent bolus was placed on the left eye surface of a human head-shaped phantom. It was assumed that the treated eye is fixed using retrobulbar anesthesia and suture on extraocular muscles for phantom study. Leksell stereotactic frame was fixed around phantom’s head and the stereotactic computed tomography (CT) was performed. Two sets of scans were acquired (a) without bolus and (b) with a bolus of 1.0 cm thickness. These scans were transferred into a treatment planning system (TPS). The skull contouring was performed using stereotactic CT images. The target, visual pathways, and eye lens were delineated in stereotactic CT space created on TPS. A clinical relevant plan was designed on the CT study set “a” to deliver a radiation dose of 30Gy at tumor margin. The plan superimposed over CT study set “b” and compiled for convincing treatment strategy. The tumor coverage was 95% at 50% prescription isodose line. The conformity index, selectivity and the gradient index were 1.27, 0.80 and 3.28 respectively. The left optic nerve and eye lens received a maximum dose of 11.1 Gy and 11.0 Gy respectively. The treatment plan overlay showed similar planning indices and critical organ doses. The plan comparison showed: an irradiated volume received the radiation dose > 15 Gy varies < 1.0% whereas the volume received < 15 Gy were larger (> 1.0%) in the study set “b”. The distant lateral points from the target volume which describe the phantom’s eyelid showed a radiation dose of 3.2 Gy - 2.5 Gy. The doses to these points were misled and ignored in the CT study set “a”. The eye bolus provides better dosimetric information in the estimation of low dose areas which is commonly misled on TPS in SRS planning for UMs.

Quantitative analysis of Gamma Knife stereotactic radiosurgery for uveal melanoma

Polish Journal of Medical Physics and Engineering

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

The purpose of the study was to analyze single fraction Gamma Knife stereotactic radiosurgery (SRS) for uveal melanoma (UM). In the treatment of UMs, the dose distribution exhibited by an irregular eye surface has more calculation uncertainty. A tissue-equivalent bolus was placed on the left eye surface of a human head-shaped phantom. It was assumed that the treated eye is fixed using retrobulbar anesthesia and suture on extraocular muscles for phantom study. Leksell stereotactic frame was fixed around phantom’s head and the stereotactic computed tomography (CT) was performed. Two sets of scans were acquired (a) without bolus and (b) with a bolus of 1.0 cm thickness. These scans were transferred into a treatment planning system (TPS). The skull contouring was performed using stereotactic CT images. The target, visual pathways, and eye lens were delineated in stereotactic CT space created on TPS. A clinical relevant plan was designed on the CT study set “a” to deliver a radiation dose of 30Gy at tumor margin. The plan superimposed over CT study set “b” and compiled for convincing treatment strategy. The tumor coverage was 95% at 50% prescription isodose line. The conformity index, selectivity and the gradient index were 1.27, 0.80 and 3.28 respectively. The left optic nerve and eye lens received a maximum dose of 11.1 Gy and 11.0 Gy respectively. The treatment plan overlay showed similar planning indices and critical organ doses. The plan comparison showed: an irradiated volume received the radiation dose > 15 Gy varies  1.0%) in the study set “b”. The distant lateral points from the target volume which describe the phantom’s eyelid showed a radiation dose of 3.2 Gy - 2.5 Gy. The doses to these points were misled and ignored in the CT study set “a”. The eye bolus provides better dosimetric information in the estimation of low dose areas which is commonly misled on TPS in SRS planning for UMs.

The purpose of the study was to analyze single fraction Gamma Knife stereotactic radiosurgery (SRS) for uveal melanoma (UM). In the treatment of UMs, the dose...

Quantitative analysis of Gamma Knife stereotactic radiosurgery for uveal melanoma

Published Online: Jun 25, 2020

Page range: 111 - 117

Received: Dec 05, 2019

Accepted: May 04, 2020

DOI: https://doi.org/10.2478/pjmpe-2020-0012

Keywords
Gamma Knife, phantom, bolus, stereotactic radiosurgery, uveal melanoma

© 2020 Raj Kishor Bisht et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Quantitative analysis of Gamma Knife stereotactic radiosurgery for uveal melanoma

Published Online: Jun 25, 2020

Page range: 111 - 117

Received: Dec 05, 2019

Accepted: May 04, 2020

DOI: https://doi.org/10.2478/pjmpe-2020-0012

KeywordsGamma Knife, phantom, bolus, stereotactic radiosurgery, uveal melanoma

© 2020 Raj Kishor Bisht et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Keywords
Gamma Knife, phantom, bolus, stereotactic radiosurgery, uveal melanoma