Original ContributionApplication of Proton Chemical Shift Imaging in Monitoring of Gamma Knife Radiosurgery on Brain Tumors
Introduction
Gamma knife radiosurgery is a stereotactic radiation therapy using a multicobalt unit supplied by Elekta (Stockholm, Sweden).[1] It enables us to irradiate intracranial targets sharply and accurately with high dosages.[2] This treatment was started with relief of pain caused by thalamic lesions[3] and has been applied to many benign brain tumors and arteriovenous malformations.4, 5, 6, 7, 8, 9, 10 It has also been applied to malignant tumors such as metastases11, 12 or malignant glioma[13] with good results.
In spite of its effectiveness, there remains some difficulty in evaluating change in the treated lesion. With conventional computed tomography or magnetic resonance imaging (MRI), the lesion may seem to increase in size after treatment, and it is difficult to determine whether it is tumor recurrence or radiation necrosis. There are some reports that differentiation between radiation necrosis and tumor recurrence in gamma knife treatment can be made by positron emission tomography with [18F] fluorodeoxyglucose,14, 15 although currently this is available at only a limited number of facilities.
Proton chemical shift imaging (1H-CSI) is performed with a conventional magnetic resonance (MR) unit, which is a noninvasive and more popular modality than positron emission tomography. 1H-CSI has been applied to many brain lesions, such as ischemia, tumors, and degenerative diseases, but not yet proved its utility in the clinic. In this study, we assessed the efficacy of 1H-CSI in monitoring radiosurgery.
Section snippets
Materials and Methods
Six patients (three women, three men; age range, 13–63 years; mean, 50 ± 18 years) underwent radiosurgery. The patient population comprised four patients with metastases, one patient with astrocytoma, and one patient with meningioma. The histology and origin were confirmed by clinical findings and open surgery. The tumor volume at the time of treatment varied from 3.3 to 12.7 cm3 (8.7 cm3 ± 3.2). The marginal radiation dose was 12–30 Gy (22.0 ± 6.0 Gy), and the maximum dose was 24-60 Gy (41.5 ±
Results
In Case 1, tumor size decreased from 9.4 cm3 to 5.9 cm3, and severe headache disappeared 1 month after radiosurgery. The cystic portion of the lesion gradually increased in size and the tumor grew to a size of 4.1 cm3 2 months after treatment. There was no tumor regrowth for 25 months after treatment. A markedly increased Cho signal was seen from the tumor center before radiosurgery, and it decreased in level 1 month after treatment. The normalized Cho showed a statistically significant
Discussion
1H-CSI is a noninvasive method of observing in vivo metabolism in the human brain. The major resonances observed are Cho, Cr, and NAA.[19] This Cho peak consists of many compounds such as glycerylphosphorylcholine and phosphorylcholine, with a relatively small contribution from free choline.20, 21 Cho is believed to reflect membrane constituents[22] and to participate in membrane synthesis and degeneration. Typical spectra from brain tumors demonstrate very high Cho, which therefore may reflect
Conclusion
1H-CSI is a noninvasive technique performed with a popular MR system. Cho from this 1H-CSI study has a correlation with loss of tumor viability. 1H-CSI can be use to differentiate between radiation necrosis and recurrent tumor. Further, 1H-CSI is very helpful in monitoring of the radiosurgery on brain tumors.
Acknowledgements
Acknowledgment—We are very grateful to Hiroaki Asano, Department of Hygiene, Kyoto Prefectural University of Medicine, for all his help with the statistical analysis.
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Quantitative analysis of spatial averaging effect on chemical shift imaging SNR and noise coherence with k-space sampling schemes
2019, Magnetic Resonance ImagingCitation Excerpt :In vivo chemical shift imaging (CSI) or MRS imaging (MRSI) provides a unique imaging tool for mapping cerebral metabolites and metabolic rates, and studying neurochemistry and neuroenergetics [1–7]. In particular, with increasing recognition of complex neurological disorders/disease, CSI has been clinically useful for the improved diagnosis in the infected tissue and longitudinal monitoring of the disease progress [8], and for advancing the understanding of pathophysiological mechanisms underlying diseases [9–12]. Due to low concentration of detectable brain metabolites in a range of few mM, signal-to-noise ratio (SNR) of CSI is a key consideration for in vivo metabolite quantification that is essential for reliable neurochemical profiling in the human brain [13–16].
Long-term normal-appearing brain tissue monitoring after irradiation using proton magnetic resonance spectroscopy in vivo: Statistical analysis of a large group of patients
2006, International Journal of Radiation Oncology Biology PhysicsCitation Excerpt :This provides a unique opportunity to study the effect of radiation on the living normal human brain by means of proton magnetic resonance spectroscopy (1H MRS) in vivo. That method allows noninvasive measurement on metabolites in the brain and is widely used in monitoring treatment response of brain tumors after radiotherapy (4–24). The response of normal tissues to radiation is more predictable than for tumors, however, as the former are less heterogeneous in their cellular composition (25).
Metabolite Changes in BT4C Rat Gliomas Undergoing Ganciclovir-Thymidine Kinase Gene Therapy-induced Programmed Cell Death as Studied by <sup>1</sup>H NMR Spectroscopy in Vivo, ex Vivo, and in Vitro
2003, Journal of Biological ChemistryCitation Excerpt :Consistent with this observation, Kizu et al. showed that in the brain tumors after radiosurgery metabolites become undetectable in the necrotic tissue. In some cases, however, macroscopically necrotic tissue showed strong signals from both lipids and CHO (33). Severe decline in CHO has also been observed in tumors responding to radiation (34).
MR-visible lipids and the tumor microenvironment
2011, NMR in Biomedicine