Magnetic resonance spectroscopy and perfusion weighted imaging as predictors for tumor response to gamma knife radiosurgery: A single center experience

Advances in radiation therapy for malignant neoplasms have produced techniques such as Gamma Knife radiosurgery, capable of delivering an ablative dose to a specific, irregular volume of tissue. However, efficient use of these techniques requires the identification of a target volume that will produce the best therapeutic response while sparing surrounding normal brain tissue. Accomplishing this task using conventional computed tomography (CT) and contrast-enhanced magnetic resonance imaging (MRI) techniques has proven difficult because of the difficulties in identifying the effective tumor margin. Magnetic resonance spectroscopic imaging (MRSI) has been shown to offer a clinically-feasible metabolic assessment of the presence and extent of neoplasm that can complement conventional anatomic imaging. This paper reviews current Gamma Knife protocols and MRSI acquisition, reconstruction, and interpretation techniques, and discusses the motivation for including magnetic resonance spectroscopy findings while planning focal radiation therapies. A treatment selection and planning strategy incorporating MRSI is then proposed, which can be used in the future to assess the efficacy of spectroscopy-based therapy planning.

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Comparison of Magnetic Resonance Spectroscopy and Perfusion-weighted Imaging in Presurgical Grading of Oligodendroglial Tumors

Neurosurgery ◽

10.1227/01.neu.0000157957.67708.3e ◽

2005 ◽

Cited By ~ 1

Keyword(s):

Magnetic Resonance ◽

Magnetic Resonance Spectroscopy ◽

Resonance Spectroscopy ◽

Oligodendroglial Tumors ◽

Perfusion Weighted Imaging

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Proton magnetic resonance spectroscopy imaging in the evaluation of patients undergoing gamma knife surgery for Grade IV glioma

Journal of Neurosurgery ◽

10.3171/jns.2004.101.3.0467 ◽

2004 ◽

Vol 101 (3) ◽

pp. 467-475 ◽

Cited By ~ 67

Author(s):

Antoinette A. Chan ◽

Aubrey Lau ◽

Andrea Pirzkall ◽

Susan M. Chang ◽

Lynn J. Verhey ◽

...

Keyword(s):

Magnetic Resonance ◽

Magnetic Resonance Spectroscopy ◽

Gamma Knife ◽

Proton Magnetic Resonance ◽

Proton Magnetic Resonance Spectroscopy ◽

Planning Process ◽

Resonance Spectroscopy ◽

Lesion Volume ◽

Content Type ◽

Fine Print

Object. The purpose of this study was to assess the differences in spatial extent and metabolic activity in a comparison of a radiosurgical target defined by conventional strategies that utilize the enhancing lesion and a metabolic lesion defined by proton magnetic resonance spectroscopy (MRS) imaging. The authors evaluated whether these differences manifest themselves in the clinical outcome of patients and assessed the value of incorporating 1H-MRS imaging—derived spatial information into the treatment planning process for gamma knife surgery (GKS). Methods. Twenty-six patients harboring Grade IV gliomas who had previously been treated with external-beam radiation therapy were evaluated by comparing the radiosurgically treated lesion volume with the volume of metabolically active tumor defined on 1H-MRS imaging. The cohort was evenly divided into two groups based on the percentage of overlap between the radiosurgical target and the metabolic lesion volumes. Patients with a percentage of overlap greater than 50% with respect to the metabolic lesion volume were classified as low risk and those with an overlap less than 50% were classified as high risk. Kaplan—Meier estimators were calculated using time to progression and survival as dependent variables. The metabolite levels within the metabolic lesion were significantly greater than those within the radiosurgical target (p ≤ 0.001). The median survival was 15.7 months for patients in the low-risk group and 10.4 months for those in the highrisk group. This difference was statistically significant (p < 0.01). Conclusions. Analysis of the results of this study indicates that patients undergoing GKS may benefit from the inclusion of 1H-MRS imaging in the treatment planning process.

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