Hypofixation and hyperfixation of Tc-99m-hexamethyl propyleneamine oxime in subacute cerebral infarction

Citation
K. Ogasawara et al., Hypofixation and hyperfixation of Tc-99m-hexamethyl propyleneamine oxime in subacute cerebral infarction, J NUCL MED, 41(5), 2000, pp. 795-799
Citations number
16
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Radiology ,Nuclear Medicine & Imaging","Medical Research Diagnosis & Treatment
Journal title
JOURNAL OF NUCLEAR MEDICINE
ISSN journal
0161-5505 → ACNP
Volume
41
Issue
5
Year of publication
2000
Pages
795 - 799
Database
ISI
SICI code
0161-5505(200005)41:5<795:HAHOTP>2.0.ZU;2-A
Abstract
The relationship between hypofixation and hyperfixation of Tc-99m-hexamethy l propyleneamine oxime (Tc-99m-HMPAO) remains unclear. The purpose of this study was to compare Tc-99m-HMPAO SPECT with regional cerebral blood flow ( CBF) imaging using Xe-133 inhalation in patients with subacute cerebral inf arction and to investigate the behavior of Tc-99m-HMPAO in the infarct area using dynamic SPECT. Methods:Xe-133 and consecutive Tc-99m-HMPAO SPECT stu dies, the latter of which consisted of dynamic and static scanning, were pe rformed on 51 patients (22 women, 29 men; age range, 40-83 y; mean age, 61 y) with cortical infarction in the middle cerebral artery territory 13-15 d after stroke onset. One region of interest (ROI) was drawn in the infarct area. The control ROI was mirrored to the contralateral side, and the same set of ROIs was applied to ail SPECT studies. Fractional fixation of Tc-99m -HMPAO in the infarct area was evaluated relatively as the ratio of the inf arct-to-control region in Tc-99m-HMPAO Static tomograms/the ratio of the in farct-to-control region in CBF images using Xe-133 inhalation and was class ified as hyperfixation when this value was >1.1 and hypofixation when this value was <0.9. To investigate the behavior of Tc-99m-HMPAO in the infarct area, the second (36-72 s after tracer injection) and eighth (252-288 s aft er tracer injection) of 8 dynamic scans were selected, and the washout rate was calculated using the formula: 1 - (mean count in the eighth scan/mean count in the second scan). Results: The infarct area showed hyperfixation o f Tc-99m-HMPAO when CBF in the area was 35 mL/100 g/min or less and showed hypofixation when CBF was >45 mL/100 g/min. The washout rate was usually ne gative when CBF imaging using Xe-133 inhalation was <20 mL/100 g/min but wa s positive when it was >45 mL/100 g/min. The washout rate was negative when the infarct area showed hyperfixation of Tc-99m-HMPAO but was positive whe n it showed hypofixation, Conclusion: (TC)-T-99m-HMPAO SPECT underestimates CBF in high-flow regions and overestimates CBF in low-flow regions of suba cute cerebral infarction. Tc-99m-HMPAO hypofixation and hyperfixation are a ssociated with backdiffusion from the brain to blood and gradual accumulati on of hydrophilic metabolites, respectively. Dynamic images should be usefu l for discriminating between Tc-99m-HMPAO hypofixation and hyperfixation.