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1069

Technical

MR Angiography David

J. Fillmore,1

of Vascular

E. Kent

Yucel,1

Susan

Grafts

E. Bniggs,1

Fred

Peripheral arterial occlusion in children, although not frequent, may result in growth disturbances in the affected extremity [1]. Arterial occlusion in children is usually due to trauma, either iatnogenic or environmental. MR angiography provides a new means of noninvasive vascular imaging that can be used to complement existing techniques for assessing graft patency such as Doppler sonognaphy, segmental pressure measurements, and evaluation of limb growth. We report our experience with this technique in four children.

All studies Electric

Techniques

were

Medical

of the

Systems,

six

studies,

on a Signa

Milwaukee,

WI).

1 .5-T MR scanner Time-of-flight

MR

(General angiog-

the

presaturation

slab

was

applied

inferior

to the imaged

volume. In the sixth study, an inferior presaturation pulse that tracks 5 mm behind the slice being imaged was applied (Fig. 1 B) [2]. Up to 60 slices were obtained per acquisition and reprocessed by using a maximum-intensity-projection (MIP) algorithm to form anteroposterior and oblique MR angiograms.

Population

of Patients

Four patients between 5 and 1 4 years old were evaluated. the patients required vascular grafts as the result of acquired

Two of mycotic

Received April 1 , 1991 : accepted after revision June 1 8, 1991. 1 Departments of Radiology and Surgery, Massachusetts General Hospital, 2 Department of Radiology, Cedars-Sinai Hospital, Los Angeles, CA 90048. AJR 157:1069-1071,

pseudoaneurysms One

was

pseudoaneurysm occlusion patient

of the

of the

graft.

were

thrombosis

artery.

artery

repeated grafts

during long-term for

popliteal

due

One

of patient

to a land-mine

examination

A total ofthree

to popliteal/tibial

Correlative

treated

popliteal

underwent

occluded

C. Waltman1

Arthun

that developed

patient

iliofemoral

after

arterial monitora posttraumatic was blast

treated injury.

replacement

and three superficial

for This

of

the

femoral

evaluated.

Studies

intraoperative

performed

raphy was performed in all cases. Axial sequential gradient-echo images were obtained with inferior presaturation and first-order flow compensation (Fig. 1A). Other parameters were 36-53/9.5-1 5.0 (TR/ TE), one or two excitations, 3- to 5-mm slice thickness, 24- to 40-cm field of view (FOV), flip angle 30-50#{176},and 1 28 phase-encoding steps. In five

and

Comparative examinations were available for all six grafts studied. All four patients had one or more arterial plethysmography studies. Three patients had duplex and color Doppler sonography. Results of

Subjects and Methoas MR Angiography

in Children

L. Steinberg,2

ing.

Note

November

1991 0361 -803X/91/1

575-1

069 © American

contrast

angiography

were

available

for

correlation

in

one patient, obtained on two separate occasions during graft revision. Routine diagnostic contrast angiography was available for correlation

in one patient. Surgical

correlation

was available in two patients.

Results With MR angiography, we accurately assessed graft patency and the status of the inflow and outhow vessels in five of the six grafts examined. All five graft occlusions were successfully identified (Figs. 1 and 2). One of the six grafts examined, thought to be occluded on the basis of arterial plethysmognaphy, was obscured by magnetic susceptibility artifact due to metallic clips at the operative site. The inflow and outflow vessels to this graft were shown to be patent. Duplex Doppler sonography subsequently showed patency of this graft. Clinically, this graft was thought to have become relatively stenotic because of the patient’s growth. In two

Boston,

Roentgen

MA 021 14. Address

Ray Society

reprint

requests

to E. K. Yucel.

1070

FILLMORE

ET

AL.

AJR:157,

November

1991

Fig. 1.-A, Axial gradient-echo (36/13/30#{176}) MR images through distal thigh with saturation band below imaged volume. Femoral vein (curved arrow) is not adequately suppressed. Small straight solid arrow = superficial femoral artery; open arrow = clip artifact from saphenous vein harvesting; large straight solid arrow = gad-

olinium

marker.

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B, Axial

gradient-echo

(50/9.5/50#{176}) MR

ages with tracking presaturation

im-

pulse with sig-

nal from artery only (arrow). Vein signal is completely suppressed. clip artifact from previous contralateral vein harvesting is again seen. C, Projection angiogram shows occlusion of popliteal artery (open arrow) and popliteal bypass graft with reconstitution of posterior (straight solid arrow) and anterior (curved arrow) tibial arteries. D, Longitudinal duplex Doppler sonogram of popliteal bypass graft confirms graft occlusion.

C

D

cases, surgery was performed on the basis of the MR angiographic findings, and the MR findings were confirmed. Discussion Series of children with vascular injury reported in the sungical literature document that most of these injuries are due to iatnogenic trauma, including arterial catheterization for diagnostic arteniography, transcatheter therapeutic procedures, and invasive hemodynamic monitoring [3-5]. Arterial occlusion occurs in 3-5% of diagnostic cardiac catheterizations in children [6] and is more common in interventional cardiac catheterizations in children [3, 4]. It also occurs in peripheral and umbilical arterial catheterization performed for hemodynamic monitoring [5] and diagnostic arteniography for noncardiac indications. Methods used to evaluate these vascular injuries in children have been quite variable. Catheter angiography is frequently

used in the acute setting, particularly if the injury is seen before the catheterization is completed. Serial evaluation of the peripheral pulses is routinely used with the addition of Doppler techniques to complement physical examination. Use of duplex Doppler and color Doppler techniques to evaluate the puncture site has been reported [7, 8]. IV digital subtnaction angiography has also been used to image vascular injury in children [3]. MR angiography reliably shows the status of the inflow vessels supplying the vascular graft, the status of the graft, and the status of the outflow vessels supplied by the graft in standard anteropostenior and oblique projections, which are readily comparable to standard contrast angiograms. By using tracking spatial presaturation pulses, venous flow signal can be suppressed throughout the imaging volume, facilitating identification of the arterial anatomy in the neprojected images. A stationary venous saturation pulse outside the imaging volume may result in recovery of venous signal with overlap

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AJA:157,

November

MR

1991

ANGIOGRAPHY

OF

VASCULAR

GRAFTS

IN CHILDREN

1071

completely by showing the status of the graft and the inflow and outflow vessels. MR angiognaphy can supplant catheter angiography in the follow-up of many of these patients. In conjunction with impedance plethysmography, a completely noninvasive physiologic and anatomic assessment of this population can be done. Continued improvement in MR angiognaphic techniques, including shorten echo times and more rapid imaging (e.g., tunboFLASH and echoplanar) may substantially shorten imaging times in the near future. These data can provide vascular surgeons and cardiologists caning for these children with a better understanding of the natural history of this problem and a better means of gauging the need and effectiveness of operative intervention in these patients. Fig. 2.-Left

posterior

oblique

projection

angiogram

(36/13/45#{176})shows

occlusion of left external iliac artery and iliofemoral bypass graft. Distal end of patent common iliac artery (curved arrow) and reconstituted common femoral artery (long arrow) can be identified. Open arrow = left iliac vein. Right iliac artery and vein are overlapped in this projection.

REFERENCES 1 . Bloom JD, Mozersky DJ, Buckley CJ, et al. Defective limb growth as a complication of catheterization of the femoral artery. Surg Gynecol Obstet

1974:138:524-526

of venous structures in the subsequent reprojections. Figures 1 A and 1 B, with and without a tracking presaturation pulse, respectively, show the dramatic improvement in venous signal suppression when this technique is used. The presence of metallic clips immediately adjacent to the graft in one patient precluded adequate evaluation of the graft itself, although the inflow and outflow vessels were readily shown. Despite the presence of thrombus in the occluded graft shown in Figure 1 , the signal intensity of the clot was insufficient on these flow-sensitive sequences to appear on the MIP neconstructions. In this group of children, we have shown that MR angiognaphy can accurately and noninvasively show vascular graft patency. We were able to characterize five of six grafts

2. Keller PJ, Drayer BP, Fram EK, Williams KD, Dumoulin CL, Souza SP. MR angio9raphy with two-dimensional acquisition and three-dimensional display. Radiology 1989:173:527-532 3. Burrows PE, Bensen LN, Williams WG, et al. Iliofemoral arterial complications of balloon angioplasty for systemic obstructions in infants and children. Circulation 1990:82:1697-1704 4. Fellows KE, Radtke W, Keane JF, Lock JE. Acute complications of catheter therapy for congenital heart disease. Am J Cardiol 1987:60:679-683 5. Flanigan DP, Keifer TJ, Schuller JJ, et al. Experience with iatrogenic pediatric vascular injuries: incidence, etiology, management and results. Ann Surg 1983:198(4):430-439 6. Stanger P. Heymann MA, Tamoft H, et al. Complications of cardiac catheterization of neonates, infants, and children: a three-year study. Circulation 1974:50:595-608 7. Taylor LM, Troutman A, Feliciano P, et al. Late complications after femoral artery catheterization in children less than five years of age. J Vasc Surg

1990:11:297-306 8. Sacks D, Robinson catheterization:

ML, Perlmutter

duplex

evaluation.

GS. Femoral arterial injury following Med 1989:8:241-246

J Ultrasound

MR angiography of vascular grafts in children.

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