title: Diagnostic value of thallium-201 chloride single-photon emission computerized tomography in differentiating tumor recurrence from radiation injury after gamma knife surgery for metastatic brain tumors.
abstract: OBJECTIVE
  The authors assessed the diagnostic value of 201Tl Cl single-photon emission computerized tomography (SPECT), performed after gamma knife surgery (GKS) for metastatic brain tumors in differentiating tumor recurrence from radiation injury.
  
  
  METHODS
  Of 6503 metastatic brain tumors treated with GKS, 201Tl SPECT was required in 72 to differentiate between tumor recurrence and radiation injury. When the Tl index was greater than 5, the lesion was diagnosed as a tumor recurrence. When the index was < 3.0 it was called radiation injury. In cases with a Tl index between 3 and 5, 201Tl SPECT was repeated once per month until the Tl index was greater than 5 or less than 3. If the Tl index fluctuated between 3 and 5 for 2 months, the lesion was diagnosed as radiation injury. The final diagnosis was based on histological examination or clinical course. The sensitivity of the method was 91%; thus 201Tl SPECT is effective for differentiating between tumor recurrence and radiation injury in metastatic brain tumors treated with GKS. Caution is necessary, however, for the following reasons: 1) simple interinstitutional comparisons of Tl indices are not possible because measurement methods are institute specific; 2) steroid administration decreases the Tl index to a variable degree; and 3) a severe radiation injury lesion, as is often seen after repeated GKS or very high dose GKS, may have a Tl index greater than 5.
  
  
  CONCLUSIONS
  Used with critical insight 201Tl Cl SPECT can be useful in distinguishing between tumor regrowth and radiation necrosis in patients with cerebral metastases.
authors.affiliation: Department of Neurosurgery, Chiba Cardiovascular Center, Ichihara, Japan. QWT03231@nifty.ne.jp
authors.forename: Toru
authors.initials: T
authors.lastname: Serizawa
authors.forename: Naokatsu
authors.initials: N
authors.lastname: Saeki
authors.forename: Yosmhinori
authors.initials: Y
authors.lastname: Higuchi
authors.forename: Junichi
authors.initials: J
authors.lastname: Ono
authors.forename: Shinji
authors.initials: S
authors.lastname: Matsuda
authors.forename: Makoto
authors.initials: M
authors.lastname: Sato
authors.forename: Masamichi
authors.initials: M
authors.lastname: Yanagisawa
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Iuchi
authors.forename: Osamu
authors.initials: O
authors.lastname: Nagano
authors.forename: Akira
authors.initials: A
authors.lastname: Yamaura
mesh_terms: D000368:Aged; D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000556:secondary* / Q000601:surgery*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local; D016609:Neoplasms, Second Primary; D011832:Radiation Injuries / Q000000981:diagnostic imaging* / Q000453:epidemiology* / Q000473:pathology; D013793:Thallium; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: C027549:thallium chloride; D013793:Thallium