title: 99Tcm-HMPAO SPET and cerebral blood flow: a study of CO2 reactivity.
abstract: Single photon emission tomography (SPET) studies using 99Tcm-HMPAO are in widespread use in the functional imaging of cerebral blood flow (CBF). While qualitatively the images correlate well with other imaging modalities, there are doubts as to the quantitative accuracy of this method. In particular, the uptake and subsequent retention of 99Tcm-HMPAO in conditions of high flow is known to be nonlinear. In this study, we compared the quantitative retention of 99Tcm-HMPAO in eight subjects under conditions of normo- and hypercapnia. There was no significant increase, despite a mean rise of the end tidal pCO2 from 5.06 to 7.06 kPa, a stimulus that is known to provoke an 80-100% rise in CBF. We conclude that SPET studies with 99Tcm-HMPAO provide excellent qualitative images of the distribution of CBF, but that quantitative data in ml hg-1 min-1 must be interpreted with caution.
authors.affiliation: Department of Surgical Neurology, National Hospital for Nervous Diseases, Queen Square, London, UK.
authors.forename: M S
authors.initials: MS
authors.lastname: Choksey
authors.forename: D C
authors.initials: DC
authors.lastname: Costa
authors.forename: F
authors.initials: F
authors.lastname: Iannotti
authors.forename: P J
authors.initials: PJ
authors.lastname: Ell
authors.forename: H A
authors.initials: HA
authors.lastname: Crockard
mesh_terms: D000328:Adult; D000368:Aged; D001812:Blood-Brain Barrier; D002245:Carbon Dioxide / Q000032:analysis; D002560:Cerebrovascular Circulation; D005189:False Positive Reactions; D005260:Female; D006801:Humans; D006935:Hypercapnia / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D015609:Organotechnetium Compounds / Q000493:pharmacokinetics*; D010091:Oximes / Q000493:pharmacokinetics*; D010313:Partial Pressure; D019690:Technetium Tc 99m Exametazime; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D015609:Organotechnetium Compounds; D010091:Oximes; D002245:Carbon Dioxide; D019690:Technetium Tc 99m Exametazime