| Home | E-Submission | Sitemap | Contact Us |  
J Korean Soc Ther Radiol Oncol > Volume 16(3); 1998 > Article
The Journal of the Korean Society for Therapeutic Radiology and Oncology 1998;16(3): 325-335.
Evaluation of Tissue Inhomogeneity for Gamma-knife Radiosurgery Using Film Dosimetry
Heung Lae Cho, Seung Chang Sohn, Hyun Suk Suh
1Department of Radiation Oncology, Inje University, College of Medicine, Pusan Paik Hospital, Pusan, Korea.
2Department of Radiation Oncology, Seoul Paik Hospotal, Pusan, Korea.
Since the mid cranial fossa is composed of various thickness of bone, the tissue inhomogeneity caused by bone would produce dose attenuation in cobalt-60 gamma knife irradiation. The correction factor for bone attenuation of cobalt-60 which is used for gamma knife source is -3.5%. More importantly, nearly all the radiosurgery treatment planning systems assume a treatment volume of unit density; any perturbation due to tissue inhomogeneity is neglected. This study was performed to confirm the bone attenuation in mid cranial fossa using gamma knife.
Computed tomography was performed after Leksell stereotactic frame had been fixed to the Alderson Rando phantom (human phantom) skull area. Kodak X-omat V film was inserted into two sites of pituitary adenoma point and acoustic neurinoma point, and irradiated by gamma knife with 14mm and 18mm collimator. An automatic scanning densitometer with a 1mm aperture is used to measure the dose profile along the x and y axis.
Isodose curve constriction in mid cranial fossa is observed with various ranges. Pituitary tumor point is greater than acoustic neurinoma point (0.2-3.0 mm vs. 0.1-1.3 mm) and generally 14 mm collimator is greater than 18mm collimator (0.4-3.0 mm vs. 0.2-2.2 mm). Even though the isodose constriction is found, constriction of 50% isodose curve which is used for treatment reference line does not exceed 1 mm. This range is too small to influence the treatment planning and treatment results.
Radiosurgery planning system of gamma knife does not show significant error to be corrected without consideration of bone attenuation.
Key Words: Gamma knife, Tissue heterogeneity, Film dosimetry
PDF Links  PDF Links
Full text via DOI  Full text via DOI
Download Citation  Download Citation
Related article
Editorial Office
Department of Radiation Oncology, Samsung Medical Center,
Proton Therapy Center, B2, 81, Irwon-ro, Gangnam-gu, Seoul 06351, Republic of Korea
Tel : +82-2-3410-3617
E-mail: rojeditor@gmail.com, roj@kosro.or.kr
Copyright © The Korean Society for Radiation Oncology.                      Developed in M2PI
Close layer
prev next