title: A simplified double-injection method to quantify cerebral blood flow and vascular reserve using iodine-123 IMP-SPECT.
abstract: We developed and evaluated a simplified double-injection method for iodine-123 N-isopropyl-p-iodoamphetamine (IMP) to quantify regional cerebral blood flow (rCBF) twice in a single SPECT session. The method enabled rapid calculations of rCBF with five 10-minute SPECT scans, a fixed distribution volume (Vd), and one-point arterial blood sampling to calibrate a standard input function (SIF).
  
  
  METHODS
  Sixty neurological patients were examined to measure rCBF twice in a single session of IMP-SPECT. Patients underwent frequent arterial blood sampling with two injections of IMP and acetazolamide challenge. We generated the SIF and determined the optimal Vd and calibration time (t(cal)) for the SIF in 30 patients. Validities of the fixed t(cal) and Vd were assessed in the remaining 30 patients. Simulation studies were also performed to evaluate the error sensitivity of the method.
  
  
  RESULTS
  The optimal t(cal) and Vd were 34 min and 30 ml/ml, respectively. The method was robust in rCBF calculation with noisy SPECT data and yielded rCBF with negligible bias and acceptable errors compared with those obtained by the double-injection method previously reported.
  
  
  CONCLUSIONS
  The method can be applied to measure rCBF twice in a single SPECT session more easily and less invasively.
authors.affiliation: Department of Nuclear Medicine and Diagnostic Imaging, Graduate School of Medicine, Kyoto University, Japan. toyo@kuhp.kyoto-u.ac.jp
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Toyoda
authors.forename: Sadahiko
authors.initials: S
authors.lastname: Nishizawa
authors.forename: Toshiki
authors.initials: T
authors.lastname: Shiozaki
authors.forename: Makoto
authors.initials: M
authors.lastname: Ueno
authors.forename: Junji
authors.initials: J
authors.lastname: Konishi
mesh_terms: D000368:Aged; D001921:Brain / Q000000981:diagnostic imaging; D002560:Cerebrovascular Circulation; D005260:Female; D006801:Humans; D007262:Infusions, Intravenous; D007275:Injections, Intravenous; D007457:Iodine Radioisotopes / Q000008:administration & dosage; D020367:Iofetamine / Q000008:administration & dosage; D008297:Male; D008875:Middle Aged; D008959:Models, Neurological; D019275:Radiopharmaceuticals / Q000008:administration & dosage; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods* / Q000706:statistics & numerical data
chemical_list: D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D020367:Iofetamine