title: Interstitial irradiation of brain tumors, using a miniature radiosurgery device: initial experience.
abstract: OBJECTIVE
  This report describes the clinical evaluation of a novel stereotactic radiosurgical device for interstitial irradiation of malignant brain tumors.
  
  
  METHODS
  Fourteen patients with cerebral lesions less than 3.5 cm in greatest diameter were treated with a single fraction of stereotactic interstitial irradiation (average, 12.5 Gy). Clinical evaluation, Karnofsky Performance Scale ratings, and neuroimaging studies were obtained at 6-week intervals postoperatively to assess treatment response. Reduction or stabilization of tumor size on follow-up imaging was accepted as local control, whereas tumor enlargement indicated local failure.
  
  
  METHODS
  This battery-powered miniature x-ray generator device produces low-energy x-ray photons that are attenuated rapidly within tissue. A dose decline rate proportional to 1/r3 yields extremely sharp dose fall-off curves with minimal exposure to surrounding tissue. Dose rates of 200 cGy per minute are possible, allowing for the administration of 12.5 Gy to a lesion 3 cm in diameter in less than 1 hour.
  
  
  RESULTS
  Local control (stabilization or reduction in lesion size) was obtained in 10 of the 13 patients with tumors with follow-up of 1.5 to 36 months (mean, 12 mo). Of three patients with radiographic progression, recurrence was symptomatic in only one. All patients tolerated the procedure well, and most patients were discharged home the day after treatment. No new neurological deficits were noted after biopsy and irradiation.
  
  
  CONCLUSIONS
  Preliminary experience with this novel radiosurgical device has demonstrated its feasibility and safety. Clinical efficacy of this technique is now under investigation in an international multicenter study.
authors.affiliation: Department of Neurosurgery, Massachusetts General Hospital, Harvard Medical School, Boston, USA.
authors.forename: G R
authors.initials: GR
authors.lastname: Cosgrove
authors.forename: F H
authors.initials: FH
authors.lastname: Hochberg
authors.forename: N T
authors.initials: NT
authors.lastname: Zervas
authors.forename: F S
authors.initials: FS
authors.lastname: Pardo
authors.forename: R F
authors.initials: RF
authors.lastname: Valenzuela
authors.forename: P
authors.initials: P
authors.lastname: Chapman
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001918:Brachytherapy / Q000295:instrumentation*; D001932:Brain Neoplasms / Q000401:mortality / Q000532:radiotherapy / Q000556:secondary / Q000601:surgery*; D003131:Combined Modality Therapy; D004867:Equipment Design; D004869:Equipment Safety; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D016634:Radiosurgery / Q000295:instrumentation*; D018714:Radiotherapy, Adjuvant; D015996:Survival Rate; D016896:Treatment Outcome