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Intravascular Sonography in the Detection of Arteriosclerosis and



             1990 ARRS                                              Intravascular     Sonography                                                                    in the
     Executive Council                                              Detection     of Arteriosclerosis                                                                   and
                 Award                                              Evaluation     of Vascular
                                                                    Interventional                                      Procedures

                      Christopher    E. Engeler1                        The purpose of this study was to evaluate               the use of intravascular           sonography         for
                           Joseph W. Yedlicka                       the detection    of arteriosclerosis       and to determine      the effects of vascular interventional
                     Janis Gissel Letourneau                        procedures on the arterial wall. A catheter-based                 20-MHz      transducer     was used. Forty
                                                                    patients were studied. Twelve had clinical evidence                  of peripheral      vascular disease,          13
            Wilfrido     R. Casta#{241}eda-ZU#{241}iga
                                                                    were healthy renal donors, and 15 underwent                 vascular      interventional     procedures.       The
                               David W. Hunter
                                                                    aorta   and the ipsilateral      iliac artery were examined             in real time under fluoroscopic
                                   Kurt Amplatz
                                                                    guidance    and the results were compared             with angiography.         Sonography       in eight of the
                                                                    13 renal donors showed            arterial wall abnormalities          in the absence        of angiographic
                                                                    evidence    of disease.     Sonography        of the 15 patients after angioplasty             or atherectomy
                                                                    demonstrated      plaque fractures,       intramural   dissections,      or atherectomy       grooves.
                                                                        Our experience      suggests      that intravascular     sonography        is of value in reducing           the
                                                                    use of angiography         to monitor progress          or complications         of vascular      interventional

                                                                       AJR      156:1087-1090, May 1991

                                                                        Miniaturization          of sonographic     transducers    has recently been achieved with
                                                                    transducer         crystal thicknesses       under 0.1 mm. Accordingly,          feasible   transducer
                                                                    frequencies          are in the range of 15-30 MHz. Axial resolution          is on the order of 0.1
                                                                    mm, as we have determined                   with a wire model in vitro. Such high-frequency
                                                                    sonognaphic            transducers     have been mounted         on catheters     for cross-sectional
                                                                    intraluminal        imaging. Either radial-array      or mechanical  scanning is possible [1]. The
                                                                    radial-array       transducer      has no moving parts; however,      the volume ofthe transducer
                                                                    increases        with the number of crystals               mounted       at the catheter        tip. With mechanical
                                                                    scanning,        the crystal      is rotated            to
                                                                                                                     360#{176} accumulate              B-mode    data for axial display.
                                                                    Both types oftransducers                   are now available commercially.               Current catheter             designs
                                                                    allow introduction      through 7- to 8-French sheaths and have over-the-wire            guidance
                                                                        This study focuses        on the demonstration     of arteriosclerotic    disease    with this
                                                                    technology,     including    the ability of sonography   to detect early arteriosclerosis,        to
                                                                    characterize      advanced      disease,   and to depict   the effects     of revascularization
                                                                    procedures         on the arterial            wall. The vessels          examined        include        the iliac arteries,
     Received   March
sion November 20, 1990.
                           21   ,1990:   accepted   after   revi-
                                                                                      femoral      arteries,       saphenous        vein     in situ    bypass      graft,      and      popliteal

   Presented   at the annual        meeting of the American
Roentgen     Ray Society,           Washington,    DC, May
1990.                                                               Materials        and    Methods
     IAll authors: Department  of Diagnostic   Radiol-
                                                                       Forty patients were examined with both conventional    angiography  and intravascular
ogy, Box 292 UMHC, The University of Minnesota
Hospital and Clinic, 420 Delaware     St. SE., Minne-               sonography. These included 13 renal donors 20-72 years old (mean age, 38 years), 12
apolis, MN 55455. Address     reprint requests   to C.              patients with symptoms of peripheral vascular disease, and 15 patients who had had 23
E. Engeler.                                                         interventional      vascular    procedures.       The   interventional      procedures       included       angioplasty      (13

0361 -803X/91/1      565-1087                                       lesions), atherectomy (seven lesions), stent placement (three lesions), or a combination of
to   American   Roentgen        Ray Society                         these techniques (seven lesions). Seven patients underwent iliac artery angioplasty. Three
1088                                                                                                                                       ENGELER          ET AL.                                                                           AJR:156,      May 1991

patients               had common                         iliac artery          stenting           after angioplasty                   had failed.          thickness      of advanced           intimal     deposits.      The spectrum          of arterioscle-
Angioplasty and/or atherectomy were used in five superficial femoral                                                                                        rosis is summarized            in Figure 1.
arteries, two popliteal arteries, and one saphenous vein in situ bypass                                                                                           A catheter-based             miniature      sonographic          device      was      used     in all
graft.                                                                                                                                                      patients (Boston Scientific                  Corp., Watertown,          MA). With this system,
   A member of the angiography         team ran the sonographic equip-                                                                                      the     transducer       crystal       with     a resonant         frequency         of 20         MHz    is
ment, making measurements         of stenoses with the built-in software                                                                                    mounted        at the end of a flexible shaft. It is rotated at 900 rpm within
and recording still images on film. The real-time images were inter-                                                                                        a 6.6-French         sheath   of 1 00-cm         length.     Sterile   water     provides      acoustic
preted by at least two radiologists present during the procedure.                                                                                           coupling between the transducer crystal and the sheath. B-mode
   The presence of a three-layered arterial wall representing the tunica                                                                                                                 rotation of the transducer.
                                                                                                                                                            scans are obtained by 360#{176}                          Real-time
intima,               media,           and         adventitia            was           documented            and          abnormal                echo-     images    are displayed      at 1 5 frames     per second by the supporting,
genicity or thickening    evaluated.     The arterial                                                 walls were characterized                              dedicated sonographic         instrumentation     (Diasonics,  Inc., Milpitas, CA).
by established      sonographic      criteria [2-5j.                                                   Increased  echogenicity                              After diagnostic     conventional     angiography,     the sonographic      catheter
corresponded to a higher lipid content of an atheroma, and acoustical                                                                                       assembly was introduced percutaneously     through a 7-French sheath
shadowing represented focal or plaquelike calcifications in advanced                                                                                        and guided fluoroscopically to the area of interest.
lesions.               The hypoechoic                          media           served             as a baseline                 to assess             the         No complications             related      to the sonographic              catheter      were       en-
                                                                                                                                                            countered.       We usually limited the sonographic                         examination            to less
                                                                                                                                                            than 1 0 mm. Access to the vessels of interest was direct and did not
                                                                                                                                                            require the use of the available over-the-wire guidance capability.



    Atheroma                                                                                                         kltwTiaI      Theckefliflg
                                                                                                                                                                  In eight of the 13 renal donors,                       several abnormalities                  of the
                                                                                                                                                            arterial wall were shown by sonography        but were not detected
                                                                                                                                                            by angiography:      fatty streaks,  diffuse or asymmetric      intimal
                                                                                                                                                            thickening   (Fig. 2), and focal calcified lesions. A three-layered
                                                                                                                                                            appearance            of the vessel              wall, an appearance                      thought        by
         Sclerosis                                                                                               ktlmsI         L,id   Accumuistion         some investigators      to be a normal sonographic            finding [3],
                                                                                                                                                            was not appreciated       in the aorta or iliac arteries in five of the
                                                                                                                                                            renal donors     and was most apparent          in patients       with ad-
                                                                                                                                                            vanced arteriosclerosis      in whom diffuse intimal thickening        was
                                                                Medial      Fibrosis
          .;,-          Medlel                                                                           Intimal     or                                        In the 1 2 patients   with known peripheral       vascular     disease,
                        Muscle        Fibers                   :.    Thrornbus                           Medal       Fibrosis
                                                                                                                                                            sonograms      of the aorta and iliac arteries          revealed      more
                 4,     caosesteroi            crystals              eiat         caicification          Lipid     Deposits
                                                                                                                                                            extensive         arteriosclerotic              changes         than were evident                  angio-
    Fig. 1.-Schematic                                     representation                of pathologic            spectrum               of arterio-         graphically. The character     and transmural   extent of disease
sclerosis.                                                                                                                                                  as well as the cross-sectional    analysis of the vascular lumen

    Fig. 2.-45-year-old      renal donor with normal aortogram.                                                                                                                                      Fig.    3.-64-year-old          man       with     claudication.
    A, Sonogram     of fatty streak, seen as bright intimal echoes at 6 o’clock position in upper abdominal                                                                                      Sonogram    of large,        soft atheroma          in common iliac
aorta (arrow).                                                                                                                                                                                   artery. Hypoechoic           tunica media            (arrow) deline-
    B, Distal abdominal aorta. Asymmetric echogenic thickening of intima on sonogram is character-                                                                                               ates original lumen.
istic of early atheromatous disease.
AJR:156,   May 1991                            INTRAVASCULAR                 SONOGRAPHY                 IN ARTERIOSCLEROSIS                                                     1089

was possible           on the sonograms              (Fig. 3). The information                     Discussion
gained by sonography               was most striking in two areas: (1) for
the analysis of the composition                 of the arteriosclerotic           abnor-               It is possible     with high-resolution       sonography       to differen-
mality,     for example,          the presence          of lipids or calcium             in        tiate the layers of the arterial wall [3-5].              We were able to
atheromata,         which could not be displayed                   by conventional                 identify all three layers in 35 of the 40 patients               studied.     The
angiography;          and (2) in the determination               of the degree of                  inability to visualize the three layers of the arterial wall in five
underlying        diffuse     arteriosclerotic        disease,      which was not                  renal donors may be due to the thinness of the intima in these
apparent       angiographically          because of its circumferential              dis-          healthy individuals.
tnibution.     In the absence of focal lesions, such a vessel may                                      Intimal hyperplasia      is particularly    evident in vascular        grafts
appear normal on angiograms.                                                                       when veins have been used as arterial                    conduits      for long
    In the 15 patients           who underwent           interventional        revascu-            periods of time. Progressive           luminal narrowing      leads to recur-
larization      procedures        (Figs. 4-6), sonography                provided     the          rent arterial insufficiency.       Intimal hyperplasia      in a 1 5-year-old
following information:           diagnosis     of complications          such as local             saphenous       vein graft is demonstrated          sonographically       in Fig-
 perforation      of the arterial wall after atherectomy                   (one case);             ure 4. Atherectomy          was an effective         method     for removing
 presence       of intimal dissections          after angioplasty          (1 0 cases);            hyperplastic      intimal deposits      in this case.
fractured      plaques (six cases); and evidence                  of an incomplete                    We observed           great variations           in the size and echogenicity
 result of the initial revasculanization             procedures,        indicating    the          of pathologic    arterial deposits,     as has been noted by other
 need for additional          intervention       (seven cases). This decision                      investigators   [2-5].    Simple atheromas     are echogenic owing
was based on the sonographic                   findings alone.                                     to the deposition       of lipids in the tunica intima. Even small,


A                                                               B                                                                 C
    Fig. 4.-is-year-old       saphenous   vein in situ bypass graft.
    A, Angiogram        shows irregular contours.
    B, Sonogram       shows severe, asymmetric       intimal hyperplasia.      Echogenic      adventitia   (arrow)   is at perimeter   of pathologic     proliferation.
    C, Sonogram        shows incomplete,   eccentric    removal of intimal     hyperplasia      after atherectomy.

    Fig. 5.-46-year-old      diabetic   man.
    A, sonogram    shows large, calcified      flap with
acoustical   shadowing    inferiorly  in common     iliac
artery after angioplasty.    Pressure    gradient is 20
mm Hg across lesion.
    B, Good sonographic      result after stent place-
ment. No pressure gradient.
1090                                                                            ENGELER       ET AL.                                                                         AJR:156,      May 1991

                                                                                                                                       Fig. 6.-48-year-old  diabetic patient with pop-
                                                                                                                                  liteal artery medial sclerosis.
                                                                                                                                      A, Sonogram shows irregularities of calcified
                                                                                                                                  vessel wall, due to atherectomy.
                                                                                                                                     B, Bursting   of calcified             media     at 7 o’clock
                                                                                                                                  position after angioplasty.

focal echogenic         deposits      could be detected             in eight of the 13        of atherectomy          over angioplasty.           This situation       is found in
renal donors without             corresponding           angiographic        abnormali-       severe intimal hyperplasia             and large intimal flaps. In the case
ties. An increased fibrous component                      is expected      to decrease        of severe calcific medial sclerosis,              atherectomy       weakened         the
echogenicity.        Calcification       of an atheroma             is obvious     when       wall sufficiently      for angioplasty         to be performed            after initial
there is total reflection          of the ultrasound            beam. Early investi-          attempts      with angioplasty         had failed to permanently             increase
gators have correlated             images from a prototype                 high-resolu-       the lumen diameter            (Fig. 6). In other situations,          atherectomy
tion intravascular           sonographic           unit in vitro with histologic              may be used as a secondary                    procedure       to remove         intimal
findings [3, 6]. Figures 2 and 3 show variations                         of atheroma-         flaps caused by angioplasty.
tous disease.                                                                                     Intravascular     stents are designed            to overcome       the inherent
    Circumferential         vascular       calcification       is shown       well with       capacity     of vessels        to collapse.      The true lumen of a stent
intravascular       sonography         in patients with medial sclerosis,                 a   cannot be established             without the use of several radiographic
vascular      disease      typically      encountered           in association       with     projections.      We have confirmed           the proper expansion            of three
long-standing        diabetes mellitus. Ultrasound                 waves are unable           iliac artery stents with intravascular                  sonography         and were
to pass beyond the highly reflective                     tunica media. The calci-             able to measure the cross-sectional                   area of a stented vessel
fications     of medial sclerosis            and more focal arteriosclerotic                  directly and establish           the relationship      of the stent to adjacent
disease can be differentiated               sonographically.          Figure 6 shows          structures      such as other vessels or masses.                 In the long-term
a case of severe medial sclerosis                  in a popliteal     artery.                 follow-up     of stents, intravascular          sonography        may be used to
   Intravascular        sonography         can     both    characterize         the   dis-    evaluate      endothelialization.         Figure 5 shows          a case of iliac
eased vessel as well as confirm                  the effect of angioplasty.           The     artery stent placement.
cross-sectional         image furnished          by intravascular         sonography
can be used to calculate               the area and flow through a vessel.
This information         is similar to that given by measured                  pressure       REFERENCES
gradients      and is most likely more accurate                   in situations      with
                                                                                               1 . Bom N, ten Hoff H, Lancee CT, Gussenhoven                         WJ, Bosch JG. Early and
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[7]. Breaks       in the vessel wall, either in the intima or media,                               tients with peripheral       vascular disease. Radiology             1990:175:61-70

may be visualized,             particularly      if this occurs         in a calcified         3. Gussenhoven       WJ, Essed CE, Frietman P. et al. Intravascular                       echographic
                                                                                                   assessment     of vessel wall characteristics:             a correlation      with histology.     lnt
lesion. Intimal flaps are commonly                    encountered         after angio-
                                                                                                   J Card Imaging i989;4: 105-116
plasty but may not be evident                     in single, or even multiple,                 4. Picano E, Landini L, Distante A, Benassi A, Sarnelli R, LAbbate                         A. Fibrosis,
angiographic        projections.        Such flaps greatly increase the risk                       lipids, and calcium in human atherosclerotic                 plaque: in vitro differentiation
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intravascular       sonography          has aided in recognizing           these com-
                                                                                               5. Eckmann      A, Kuhn FP, StOrkel 5, GrOnninger                  J, Kaiser L. Sonomorpholo-
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or stenting       procedures         in about half of the cases (Figs. 5A                          und     Grenzen        der      hochauflOsenden             B-Scan-Sonographie.               ROFO
and 6B).                                                                                           1988:149(1):      15-21

    Intravascular       sonography         characterizes        arterial disease by            6. Meyer CR, Chiang EH, Fechner KP, Fitting DW, Williams                    DM, Buda AJ.
                                                                                                  Feasibility of high-resolution,   intravascular      ultrasonic    imaging catheters.
demonstrating          the thickness          and composition             of the wall.
                                                                                                  Radiology 1988:168:113-116
While further experience                is necessary,      it is notable that the              7. White NW Jr, Yock PG. Intravascular          ultrasound:     catheter-based    Doppler
larger the pathologic           deposits,      the greater the relative merits                    and two-dimensional      imaging. Cardiol Clin 1989:7(3):525-535


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