title: Evaluation of the response of metastatic brain tumors to stereotactic radiosurgery by proton magnetic resonance spectroscopy, 201TlCl single-photon emission computerized tomography, and gadolinium-enhanced magnetic resonance imaging.
abstract: OBJECTIVE
  The goal of this study was to investigate the usefulness of proton (1H) magnetic resonance (MR) spectroscopy to evaluate the response of metastatic brain tumors to stereotactic radiosurgery (SRS) in comparison with Gd-enhanced MR imaging and single-photon emission computerized tomography with administration of thallium-201 chloride (201TlCl-SPECT).
  
  
  METHODS
  Forty patients with a total of 47 metastatic brain tumors were evaluated. The primary lesion was identified in all cases. Stereotactic radiosurgery was effective in 37 lesions. All patients were examined using Gd-enhanced MR imaging before and after SRS. Thalium-201 chloride was administered to 27 patients with 34 tumors and SPECT images were obtained. Proton MR spectroscopy was performed in 36 patients who harbored 43 tumors. On Gd-enhanced MR images, a decrease in the volume of the Gd-enhanced lesion and a change in the enhanced effect in the lesion after treatment were recognized as showing the effectiveness of SRS between 1 and 3 months or more (mean 8.54 +/- 3.58 weeks). In 201TlCl-SPECT studies, the ratio of lesion to normal brain decreased from 2 weeks to 2 months (mean 5.03 +/- 2.77 weeks) after radiosurgery. On 1H-MR spectroscopy images a high choline (Cho) peak and a lipid-dominant (Lip) peak were observed in 25 lesions and a high Cho peak and a lactate-dominant (Lac) peak were observed in 12 lesions before SRS. A decrease in the Cho peak, a disappearance of the Lac peak, and an increase in the Lip peak were observed between 1 week and 1 month (mean 2.76 +/- 1.62 weeks) after treatment.
  
  
  CONCLUSIONS
  Based on histopathological findings obtained at autopsy or at surgery, we assume that a high Cho peak may be observed in viable tumor tissue and a Lip peak in areas of necrosis. The results indicate that 1H-MR spectroscopy is potentially a more sensitive tool in evaluating the response to SRS than 201TlCl-SPECT or Gd-enhanced MR imaging and that it can be used earlier for this purpose than those other imaging methods.
authors.affiliation: Department of Neurosurgery and Radiology, Central Laboratory for Research and Education, Asahikawa Medical College, Asahikawa, Japan. tekimura-nsu@umin.ac.jp
authors.forename: Teruo
authors.initials: T
authors.lastname: Kimura
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Sako
authors.forename: Kunio
authors.initials: K
authors.lastname: Tanaka
authors.forename: Takumi
authors.initials: T
authors.lastname: Gotoh
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yoshida
authors.forename: Tamio
authors.initials: T
authors.lastname: Aburano
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Tanaka
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Arai
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Nakada
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D001921:Brain / Q000473:pathology / Q000601:surgery; D001932:Brain Neoplasms / Q000175:diagnosis / Q000556:secondary* / Q000601:surgery; D002794:Choline / Q000378:metabolism; D003287:Contrast Media; D005260:Female; D005500:Follow-Up Studies; D019786:Gadolinium DTPA; D006801:Humans; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted; D019344:Lactic Acid / Q000378:metabolism; D050356:Lipid Metabolism; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000175:diagnosis*; D016634:Radiosurgery; D012680:Sensitivity and Specificity; D013793:Thallium; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D003287:Contrast Media; D001224:Aspartic Acid; D019344:Lactic Acid; C027549:thallium chloride; C000179:N-acetylaspartate; D013793:Thallium; D019786:Gadolinium DTPA; D002794:Choline