Wall-to-lumen ratio of intracranial arteries measured by indocyanine green angiography.
BACKGROUND
The wall-to-lumen ratio (WLR) is an important parameter in vascular medicine because it indicates the character of vascular wall as well as the degree of stenosis. Despite the advances in medical imaging technologies, it is still difficult to measure the thin-walled normal intracranial arteries, and the reports on the WLR of normal intracranial artery are limited. It might be possible to calculate the WLR using the indocyanine green (ICG) angiography, which is used to observe intracranial vessels during microsurgery.


OBJECTIVE
To evaluate the WLR of normal intracranial arteries using ICG angiography.


METHODS
From the three cases in which ICG angiography was recorded with a ruler during microsurgery, 20 measurement points were chosen for the analysis. The ICG was injected intravenously with a dose of 0.2 mg/kg, and the vessels were inspected at high magnification using an operating microscope equipped with near-infrared illumination system. The vessel outer diameter and the luminal diameter were measured using the images before and after the ICG arrival based on the pixel ratio method using a ruler as reference, respectively. The WLR was calculated as 0.5 × (vessel outer diameter - vessel luminal diameter).


RESULTS
The WLR (mean ± standard deviation) of normal intracranial arteries was 0.086 ± 0.022. The WLR tended to be high in small arteries.


CONCLUSIONS
The WLR of normal intracranial arteries calculated using ICG angiography was consistent with the WLR reported in the previous reports based on human autopsy.
Department of Neurosurgery, Graduate School of Medicine, The University of Tokyo, Bunkyo, Tokyo, Japan.
Daichi
D
Nakagawa
Department of Neurosurgery, Graduate School of Medicine, The University of Tokyo, Bunkyo, Tokyo, Japan.
Masaaki
M
Shojima
Department of Neurosurgery, Graduate School of Medicine, The University of Tokyo, Bunkyo, Tokyo, Japan.
Masanori
M
Yoshino
Department of Neurosurgery, Graduate School of Medicine, The University of Tokyo, Bunkyo, Tokyo, Japan.
Taichi
T
Kin
Department of Neurosurgery, Graduate School of Medicine, The University of Tokyo, Bunkyo, Tokyo, Japan.
Hideaki
H
Imai
Department of Neurosurgery, Graduate School of Medicine, The University of Tokyo, Bunkyo, Tokyo, Japan.
Seiji
S
Nomura
Department of Clinical Information Engineering, Graduate School of Medicine, The University of Tokyo, Bunkyo, Tokyo, Japan.
Toki
T
Saito
Department of Neurosurgery, Graduate School of Medicine, The University of Tokyo, Bunkyo, Tokyo, Japan.
Hirofumi
H
Nakatomi
Department of Clinical Information Engineering, Graduate School of Medicine, The University of Tokyo, Bunkyo, Tokyo, Japan.
Hiroshi
H
Oyama
Department of Neurosurgery, Graduate School of Medicine, The University of Tokyo, Bunkyo, Tokyo, Japan.
Nobuhito
N
Saito
In vivo; indocyanine green angiography; intracranial artery; normal; vascular wall; wall-to-lumen ratio
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