A Novel Method to Verify Gamma Knife Radioactive Source Count - Technology and Investment

TI > Vol.9 No.3, August 2018

A Novel Method to Verify Gamma Knife Radioactive Source Count ()

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Download as PDF (Size: 1075KB) PP. 154-160

DOI: 10.4236/ti.2018.93011 1,049 Downloads 1,992 Views

Author(s)

Hsein-Tang Tu^1,2, Cheng-Siu Chang^3,4, Chun-Yi Chuang⁴, Cheng-Wei Huang^5*, Wei-Jr Li⁶, Tzu-Chin Wu^3,4, Fu-Yu Feng⁷, Zih-Ping Ho⁸, Chuan-Fu Huang¹

Affiliation(s)

¹Gamma Knife Center, Chang Bing Show Chwan Memorial Hospital, Taiwan, China.
²Division of Pulmonary Medicine, Department of Internal Medicine, Chung-Shan Medical University Hospital, Taiwan, China.
³Departments of Neurosurgery, Chung-Shan Medical University Hospital, Taiwan, China.
⁴School of Medicine, Chung-Shan Medical University, Taiwan, China.
⁵Department of Internal Medicine, Kaiser Permanente Los Angeles Medical Center, Los Angeles, USA.
⁶Gamma Knife Center, China Medical University Hospital, Taiwan, China.
⁷Department of Medical Imaging, Show Chwan Memorial Hospital, Taiwan, China.
⁸Research Assistant Center, Show Chwan Memorial Hospital, Taiwan, China.

ABSTRACT

Background: Regulation requires periodic reconfirmation of the number of radioactive sources in Gamma Knife (GK). To comply with regulations, the total dose output (TDO) method, originally designed to verify amount of radiation received by patients, was adopted as a tool for source security. However, we suspect the TDO method may be unreliable in detecting small numbers of missing sources given that a 2% margin of error is allowed. We propose an alternate method using Gafchromic films to identify number of sources present. Method: To test the efficacy of the TDO method, we simulated real-life source loss by plugging up to 5 sources. TDO after plugging 0, 1, 2, 3, 4, and 5 sources were measured using GK 4C. Percentage change for each additional source plugged was computed. We then proceeded to test the film method. For GK 4C, 2 Gafchromic RTQA2 single sided films measuring 10 × 10 inch were first halved to 5 × 10 inch films. Four 5 × 10 inch films were then adhered to the inner surface of the 18 mm collimator. For GK Perfexion, 2 Gafchromic EBT3 double sided films measuring 10 × 12 inches were combined and rolled into a cone film and adhered to the collimator during installation. In both cases, the films were exposed to 0.5 Gy. Results: TDO was inversely related to the number of source plugged. TDO decreased by more than 2% after 5 plugs. The film method was able to outline all 201 and 192 Co sources for GK4Cand Perfexion respectively. Conclusion: A single lost source is hard to detect using the TDO method given that at least 5 sources had to be lost before the change in TDO will exceed the margin of error (±2%). The film method bypasses this limitation and offers an easy alternative to accurately obtain the number of sources.

KEYWORDS

Source, Security, Gamma Knife, Radiosurgery

Share and Cite:

Tu, H. , Chang, C. , Chuang, C. , Huang, C. , Li, W. , Wu, T. , Feng, F. , Ho, Z. and Huang, C. (2018) A Novel Method to Verify Gamma Knife Radioactive Source Count. Technology and Investment, 9, 154-160. doi: 10.4236/ti.2018.93011.

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