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Cyberknife Radiosurgery

Individual Beam Sharpening Improves Composite Dose Fall-off Near a Target for Non-isocentric Cyberknife Radiosurgery (341-348)

Stereotactic radiosurgery (SRS) refers to a high dose of radiation delivered to a focal region of interest while maximizing the steep dose gradient to minimize dose to the surrounding normal tissues. Multiple factors can influence the dose fall-off, and the relative importance of such factors have not yet been characterized for non-isocentric Cyberknife SRS. Our aim was to investigate whether the composite dose fall-off near a target may be enhanced via sharpening the lateral beam profile (or penumbra) of each individual beam. Cyberknife beam profiles were fitted and parameterized to obtain a characteristic penumbra function for each collimator size. Simulated beam profiles with progressively sharper penumbras were then generated, and used to perform simulated treatment planning on seven pediatric intracranial arteriovenous malformations (AVMs) cases. Penumbra size was found to significantly influence the peripheral dose fall-off. Peripheral dose volumes were reduced by 5 to 10% with reductions in penumbra size ranging from 40 to 80%. Dose conformality and homogeneity were not significantly changed with decreasing penumbra size. Therefore, individual beam sharpening provides a straightforward way of improving the composite dose fall-off for non-isocentric Cyberknife SRS.

Key words: Radiosurgery; Cyberknife; Penumbra; Arteriovenous malformation.

This article can be cited as:
Wahl, M., Hwang, A., Nakamura, J., Barani, I., Fogh, S., Sneed, P., McDermott, M., Sahgal, A., Ma, L., Individual Beam Sharpening Improves Composite Dose Fall-off Near a Target for Non-isocentric Cyberknife Radiosurgery Technol Cancer Res Treat. 12, 341-348 (2013) DOI: 10.7785/tcrt.2012.500322


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Received: May 16, 2012; Revised: October 3, 2012; Accepted: October 18, 2012; Epub: January 25, 2013

TCRT August 2013

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Volume 12
No.4 (275-382)
August 2013
ISSN 1533-0338

DOI: 10.7785/tcrt.2012.500322

Michael Wahl, M.D.1
Andrew Hwang, Ph.D.1
Jean Nakamura, M.D.1
Igor Barani, M.D.1
Shannon Fogh, M.D.1
Penny Sneed, M.D.1
Michael McDermott, M.D.2
Arjun Sahgal, M.D.3
Lijun Ma, Ph.D.1*

1Department of Radiation Oncology, University of California, San Francisco 505 Parnassus Ave, San Francisco, CA, 94143-0226
2Department of Neurosurgery, University of California, San Francisco, 505 Parnassus Ave., Room 779 M, San Francisco, CA 94143-0112
3Department of Radiation Oncology, Sunnybrook Health Sciences Centre and the Princess Margaret Hospital, University of Toronto, 610 University Avenue, Toronto, Ontario, M6G 2M5, Canada