The Use of Cone Beam Computed Tomography for Image Guided Gamma Knife Stereotactic Radiosurgery: Initial Clinical Evaluation

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• 作者：Winnie Li ; MRT(T) ; MSc^&lowast ; ; ^&dagger ; ; Young-Bin Cho ; PhD^&lowast ; ; ^&dagger ; ; Steve Ansell ; BSc^&lowast ; ; Normand Laperriere ; MD^&lowast ; ; ^&dagger ; ; Cynthia Mé ; nard ; MD^&lowast ; ; ^&dagger ; ; Barbara-Ann Millar ; MD^&lowast ; ; ^&dagger ; ; Gelareh Zadeh ; MD ; PhD^&Dagger ; ; ^§ ; ; Paul Kongkham ; MD ; PhD^&Dagger ; ; Mark Bernstein ; MD ; MHSc^&Dagger ; ; David A. Jaffray ; PhD^&lowast ; ; ^&dagger ; ; ^‖ ; Caroline Chung ; MD ; MSc ; CIP^&lowast ; ; ^&dagger ; ; ^{caroline.chung.md@gmail.com" class="auth_mail" title="E-mail the corresponding author}
• 刊名：International Journal of Radiation Oncology*Biology*Physics
• 出版年：2016
• 出版时间：1 September 2016
• 年：2016
• 卷：96
• 期：1
• 页码：214-220
• 全文大小：567 K

文摘

The present study used cone beam computed tomography (CBCT) to measure the inter- and intrafraction uncertainties for intracranial stereotactic radiosurgery (SRS) using the Leksell Gamma Knife (GK).

Methods and Materials

Using a novel CBCT system adapted to the GK radiosurgery treatment unit, CBCT images were acquired immediately before and after treatment for each treatment session within the context of a research ethics board–approved prospective clinical trial. Patients were immobilized in the Leksell coordinate frame (LCF) for both volumetric CBCT imaging and GK-SRS delivery. The relative displacement of the patient's skull to the stereotactic reference (interfraction motion) was measured for each CBCT scan. Differences between the pre- and post-treatment CBCT scans were used to determine the intrafraction motion.

Results

We analyzed 20 pre- and 17 post-treatment CBCT scans in 20 LCF patients treated with SRS. The mean translational pretreatment setup error ± standard deviation in the left-right, anteroposterior, and craniocaudal directions was −0.19 ± 0.32, 0.06 ± 0.27, and −0.23 ± 0.2 mm, with a maximum of −0.74, −0.53, and −0.68 mm, respectively. After an average time between the pre- and post-treatment CBCT scans of 82 minutes (range 27-170), the mean intrafraction error ± standard deviation for the LCF was −0.03 ± 0.05, −0.03 ± 0.18, and −0.03 ± 0.12 mm in the left-right, anteroposterior, and craniocaudual direction, respectively.

Conclusions

Using CBCT on a prototype image guided GK Perfexion unit, we were able to measure the inter- and intrafraction positional changes for GK-SRS using the invasive frame. In the era of image guided radiation therapy, the use of CBCT image guidance for both frame- and non–frame-based immobilization systems could serve as a useful quality assurance tool. Our preliminary measurements can guide the application of achievable thresholds for inter- and intrafraction discrepancy when moving to a frameless approach.