J Med Ultrasonics (2007) 34:73–74
DOI 10.1007/s10396-006-0133-8© The Japan Society of Ultrasonics in Medicine 2007

ULTRASOUND IMAGE OF THE MONTH
Hideyuki HASEGAWA · Hiroshi KANAI
Masataka ICHIKI · Fumiaki TEZUKA

Tissue structure of arterial wall revealed with elasticity imaging

Received: August 31, 2006 / Accepted: September 13, 2006

Keywords elasticity imaging · small strain · phased tracking
method · atherosclerosis

Ultrasonic elasticity imaging
A 63-year-old patient with arteriosclerosis obliterans wasscheduled to undergo bypass grafting surgery. Figure 1ashows a B-mode image of the femoral artery transcutaneously scanned by conventional diagnostic equipment (EUB655; Hitachi) before the surgery. The right edge of theB-mode image in Fig. 1a was kept 20 mm away from thedistal bifurcation so as to make the position of the pathological image coincide with that of the elasticity image.
As shown in Fig. 1a, the measured region shows diffuse
intimal thickening. An elasticity image of the posterior wall
was obtained (Fig. 1b) using the phased tracking method
proposed by our group.1–3 In Fig. 1b, the measured elasticity
image shows a layered structure. The luminal and outer regions are hard, and the region in the middle of the posteriorwall is softer than the luminal and outer regions.

Discussion
The measured elasticity image was compared with the pathological image of the corresponding section made after thesurgical extraction. During bypass grafting surgery, a string
was tied to the external surface of the anterior wall for
identification of the anterior and posterior walls, and theH. Hasegawa (*) · H. Kanai
Graduate School of Engineering, Tohoku University, 6-6-05 Aoba,Aramaki, Aoba, Sendai 980-8579, Japan
Tel. +81-22-795-7079, Fax +81-22-263-9230
e-mail: hasegawa@us.ecei.tohoku.ac.jp
M. Ichiki
Sendai Hospital of East Railway Company, Sendai, Japan
F. Tezuka
Sendai Medical Center, Sendai, Japan

artery was then dissected and extracted by referring tothe distance (20 mm) between the measured region and thedistal bifurcation.
The pathological image of the corresponding region isshown in Fig. 1c, and an enlarged view of the region surrounded by the cyan line in Fig. 1c is shown in Fig. 1e. InFig. 1c and 1e, collagen, smooth muscle, and elastin arestained in blue-green, red, and black, respectively. For detailed comparison of the measured elasticity distribution
with the pathological image, Fig. 1d shows the elasticity
distribution along the ultrasonic beam in the region surrounded by the cyan line in Fig. 1b. Surprisingly, the layered
tissue structure in Fig. 1e corresponds to the layered structure as revealed by the elasticity image shown in Fig. 1b as
well as the elasticity distribution shown in Fig. 1d. The hard
luminal region (Ra) in Fig. 1d was found to correspond tothe collagen-rich region of the intima and a part of the media in Fig. 1e. The relatively soft region (Rb) in the middleof the wall in Fig. 1d corresponds to the remaining part ofthe media with smooth muscle (Fig. 1e). The outer hardregion Rc in Fig. 1d corresponds to the collagen-rich adventitia in Fig. 1e. These results show that the elasticity image
measured by the newly developed transcutaneous ultrasound method1–3 successfully reveals the tissue structure of
the arterial wall.
Computed tomography (CT), magnetic resonance imaging (MRI), and ultrasonography, in which the morphology
and angiographic lumen of the artery can be evaluated, areused for conventional diagnosis of atherosclerosis.4–6 However, it is difficult to evaluate the regional mechanicalproperties of the arterial wall. Elasticity imaging with transcutaneous ultrasound provides additional useful information for diagnosis of atherosclerosis in clinical situations.
Furthermore, the proposed method can be installed indiagnostic ultrasound systems provided by various manufacturers. The ultrasound systems provided by Toshiba Co.,
Ltd. (Tokyo, Japan) and Aloka Co., Ltd. (Tokyo, Japan)
have already been used in our research,3,7 and real-timeequipment for elasticity imaging of the arterial walls is
being developed by Panasonic Co., Ltd. (Kanagawa, Japan)
for clinical studies.8

74
Fig. 1. a Ultrasonic B-mode
image of the femoral artery of
the 63-year-old male patient.
The right edge of the B-mode
image was kept 20 mm awayfrom the distal bifurcation. b
Elasticity image of the posteriorwall in the region surrounded by
the green line in a. c Pathologicalimage of the measured region in
the posterior wall. d Radial
elasticity distribution along theultrasonic beam, whichcorresponds to the region
surrounded by the cyan line in b.
e Enlarged view of the region
surrounded by the cyan line in c

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