Heterogeneity of Cerebral Blood Flow: a Fractal Approach

J. T. Kuikka; P. Hartikainen

doi:10.1055/s-0038-1632242

Nuklearmedizin - NuclearMedicine, Table of Contents

Nuklearmedizin 2000; 39(02): 37-42
DOI: 10.1055/s-0038-1632242

Original Article

Schattauer GmbH

Heterogeneity of Cerebral Blood Flow: a Fractal Approach

Heterogenität der Hirndurchblutung: eine fraktale Annäherung

J. T. Kuikka

¹Departments of Clinical Physiology and Neurology, Kuopio University Hospital and Niuvanniemi Hospital, Kuopio, Finland

,

P. Hartikainen

¹Departments of Clinical Physiology and Neurology, Kuopio University Hospital and Niuvanniemi Hospital, Kuopio, Finland

› Author Affiliations

Abstract

Summary

Aim: We demonstrate the heterogeneity of regional cerebral blood flow using a fractal approach and singlephoton emission computed tomography (SPECT). Method: Tc-99m-labelled ethylcysteine dimer was injected intravenously in 10 healthy controls and in 10 patients with dementia of frontal lobe type. The head was imaged with a gamma camera and transaxial, sagittal and coronal slices were reconstructed. Two hundred fifty-six symmetrical regions of interest (ROIs) were drawn onto each hemisphere of functioning brain matter. Fractal analysis was used to examine the spatial heterogeneity of blood flow as a function of the number of ROIs. Results: Relative dispersion (= coefficient of variation of the regional flows) was fractal-like in healthy subjects and could be characterized by a fractal dimension of 1.17 ± 0.05 (mean ± SD) for the left hemisphere and 1.15 ± 0.04 for the right hemisphere, respectively. The fractal dimension of 1.0 reflects completely homogeneous blood flow and 1.5 indicates a random blood flow distribution. Patients with dementia of frontal lobe type had a significantly lower fractal dimension of 1.04 ± 0.03 than in healthy controls. Conclusion: Within the limits of spatial resolution of SPECT, the heterogeneity of brain blood flow is well characterized by a fractal dimension. Fractal analysis may help brain scientists to assess age-, sex- and laterality-related anatomic and physiological changes of brain blood flow and possibly to improve precision of diagnostic information available for patient care.

Zusammenfassung

Ziel: Unter Einsatz einer fraktalen Annäherung und SPECT wird die Heterogenität der regionalen Hirndurchblutung demonstriert. Methode: Tc-99m-ECD wurde nach intravenöser Injektion bei zehn Gesunden sowie bei zehn Patienten mit Demenz vom Frontallappen-Typ eingesetzt. Aus dem SPECT-Umlauf wurden transaxiale, sagittale und koronare Schnitte rekonstruiert. 265 symmetrische Regions of Interest wurden im Gebiet der funktionellen grauen Substanz für jede Hemisphäre markiert. Die fraktale Analyse wurde eingesetzt zur Bestimmung der räumlichen Heterogenität der Hirndurchblutung als Funktion der ROI-Anzahl. Ergebnisse: Die relative Streuung (Variationskoeffizient der regionalen Durchblutung) war bei Gesunden fraktalähnlich geordnet und konnte durch eine Fraktaldimension von 1,17 ± 0,05 (Mittelwert ± Streubreite) für die linke Hemisphäre und von 1,15 ± 0,04 für die rechte Hemisphäre charakterisiert werden. Dabei entspricht eine Fraktaldimension von 1,0 einer völlig gleichmäßigen Durchblutung, ein Wert von 1,5 zeigt eine vollständig zufällige Verteilung an. Patienten mit Demenz des Frontallappen-Typs wiesen dagegen eine signifikant niedrigere fraktale Dimension von 1,04 ± 0,03 auf. Schlußfolgerung: Innerhalb der räumlichen Auflösungsgrenzen von SPECT kann die Heterogenität der Hirndurchblutung durch eine Fraktaldimension gut charakterisiert werden. Eine fraktale Analyse kann Hirnforschern bei der Abschätzung von Alters-, Geschlechtsund physiologischen Veränderungen sowie bei der anatomischen Seitenbetonung der Hirndurchblutung behilflich sein und möglicherweise auch die Genauigkeit der diagnostischen Information in der Patientenversorgung verbessern.

Keywords

Cerebral blood flow - dementia - fractal analysis - heterogeneity - SPECT

Schlüsselwörter

Zerebrale Hirndurchblutung - Demenz - fraktale Analyse - Heterogenität - SPECT

Full Text

References

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