Available online at www.sciencedirect.com

Magnetic Resonance Imaging 29 (2011) 975 – 984

MR signal change in venous thrombus relates organizing process andthrombolytic response in rabbit
Yasuyoshi Kuroiwa a,b,d , Atsushi Yamashita b , Tosiaki Miyati d , Eiji Furukoji c ,Misaki Takahashi b , Toshiya Azuma c , Hiroshi Sugimura c , Taketoshi Asanuma e ,Shozo Tamura c , Keiichi Kawai d,f , Yujiro Asada b,⁎a
Department of Radiological Technology, Koga General Hospital, Miyazaki, Japan
Department of Pathology, Faculty of Medicine, University of Miyazaki, Miyazaki, Japanc
Department of Radiology, Faculty of Medicine, University of Miyazaki, Miyazaki, Japand
Division of Health Sciences, Graduate School of Medical Science, Kanazawa University, Ishikawa, Japane
Department of Veterinary Sciences, Faculty of Agriculture, University of Miyazaki, Miyazaki, Japanf
Biomedical Imaging Research Center, University of Fukui, Fukui, Japan
Received 21 October 2010; revised 18 April 2011; accepted 22 April 2011b

Abstract
Venous thrombus is subsequently organized and replaced by fibrous connective tissue. However, the sequential changes in venous
thrombi are not reliably detected by current noninvasive diagnostic techniques. The purpose of this study is to reveal whether magnetic
resonance (MR) can detect venous thrombus, define thrombus age and predict thrombolytic responses. Thrombus in the rabbit jugular vein
was imaged with a 1.5-T MR system at 4 h and at 1, 2 and 4 weeks using three-dimensional (3D) fast asymmetric spin echo T2-weighted(T2W) and 3D-gradient echo T1-weighted (T1W) sequences. The jugular veins were histologically assessed at each time point. Magnetic
resonance imaging (MRI) was also performed in vivo before and 30 min after tissue plasminogen activator (t-PA) administration. The
thrombi in MRI were comparable in size to histological sections. The signal intensity (SI) of thrombi at 4 h was heterogeneously high or low
on T2W or T1W images, respectively. The SI of thrombi on T2W images decreased time-dependently, but increased on T1W images at 1 and2 weeks. Morphological analysis showed time-dependent decreases in erythrocyte, platelet and fibrin areas and time-dependent increases insmooth muscle cell, macrophage, collagen and iron areas. The t-PA administration significantly decreased thrombus volume at 4 h but not at
1, 2 and 4 weeks. Venous thrombosis can be reliably and noninvasively detected by MRI. Measurement of SI might support assessments ofthrombus age and thrombolytic response.
© 2011 Elsevier Inc. All rights reserved.
Keywords: Magnetic resonance imaging; Signal intensity; Thrombolysis

1. Introduction
Deep venous thrombosis (DVT) and pulmonary embolism, which are collectively termed venous thromboembolism, comprise a major medical concern in Europe andNorth America, especially among the elderly [1]. Although
they can arise in veins of the limbs as well as in renal,
mesenteric, splenic, portal or cerebral veins, they mainly
develop in the deep veins of the lower legs. Venous⁎ Corresponding author. Tel.: +81 985 85 2810; fax: +81 985 85 7614.
E-mail address: yasada@fc.miyazaki-u.ac.jp (Y. Asada).
0730-725X/$ – see front matter © 2011 Elsevier Inc. All rights reserved.
doi:10.1016/j.mri.2011.04.015

thrombus initially consists of erythrocytes, platelets andfibrin [2,3] that become organized and replaced withfibrous connective tissue [4,5]. However, sequentialchanges in venous thrombi are not reliably detected bycurrent noninvasive diagnostic techniques, such as ultrasonography and computed tomography [6].
Thrombolytic therapy can be effective against DVT,
resulting in rapid clot lysis, less impaired venous hemodynamics and reduced long-term morbidity from chronic
venous insufficiency as compared with anticoagulant treatment alone [7,8]. Because thrombolytic therapy results in a
substantial increase in risk of bleeding compared with anticoagulant treatment alone, to predict the outcome of976

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thrombolytic therapy in patients with DVT is of particularconcern. To clinically evaluate the age of thrombus and to
predict responses to thrombolytic therapy are difficult.
Magnetic resonance imaging (MRI) for DVT was
introduced in the early 1990s, and it is more accurate thanconventional venography and ultrasonography [9–12]. A
variety of techniques have been described, including a twodimensional (2D) time-of-flight (TOF) angiography witharterial flow suppression, three-dimensional (3D) T1weighted prepared gradient echo sequence with fat saturation
and a contrast-enhanced T1 fast field echo [13]. Although an
animal study has advocated using MRI to detect venous
thrombosis, MR images and age-related changes have notbeen adequately characterized [14]. Magnetic resonanceimaging generates high tissue contrast in terms of biophysical and biochemical parameters. We therefore examined theability of MRI to detect venous thrombosis, define thrombus
age and predict thrombolytic responses in a rabbit model ofvenous thrombosis.

2. Materials and methods
2.1. Venous thrombus formation in rabbit jugular vein
The Animal Care Committees of our institutions
approved the animal research protocols, which conformed
to the Guide for the Care and Use of Laboratory Animals
published by the US National Institutes of Health.
Table 1 shows the protocol in this study. Thirty-nine male
Japanese white rabbits weighing 2.5 to 3.0 kg were fed with aconventional diet. All surgical manipulations proceeded
under aseptic conditions and general anesthesia induced via
an intravenous (iv) injection of pentobarbital (25 mg/kg,
body weight). Thrombi were generated in the right jugularveins by a combination of endothelial denudation induced
by inserting a 4F balloon catheter (Edwards Lifesciences,
Irvine, CA, USA) into the right jugular vein and vessel
ligation (blood stasis) [15] achieved by ligating 12 mm of
the jugular vein. The jugular veins (n=6 each) werevisualized by MRI at 4 h and at 1, 2 and 4 weeks after theprocedure, and images were analyzed at 3-mm intervals. At
each time point, rabbits (n=3 each) were injected withheparin (500 U/kg, iv) and then sacrificed with an overdose of pentobarbital (60 mg/kg, iv) for histological analysis.
The animals were perfused with 50 ml of 0.01 mol/L
phosphate-buffered saline and then perfusion-fixed with

Table 1
Experimental design
Time after venous thrombus initiation 4 hSequential MRI (n=3)
MRI and histological analysis (n=12)
MRI before and 30 min after
t-PA (n=24)

1 week 2 weeks 4 weeks

n=3 →n=3 n=3n=6 n=6

→
n=3
n=6

→
n=3
n=6

4% paraformaldehyde for histological and immunohistochemical evaluation.
The jugular veins were also visualized by MRI before and30 min after an infusion of tissue plasminogen activator (tPA, 600,000 U/kg/h) at 4 h and at 1, 2 and 4 weeks after theprocedure to determine the effects of thrombolytic therapy(n=6 each).
2.2. MR imaging
Four hours and 1, 2 and 4 weeks after thrombus formation, the rabbits were anesthetized and placed in the left
decubitus position in a 1.5-T superconductive magnet unit
(Excelart Vantage XGV Power Plus Package, Toshiba
Medical Systems, Tokyo, Japan) using a 200-mm quadrature transmitter/receiver coil. The localizer consists of fast,multislice, multistack (axial, sagittal and coronal images)
segmented field echo localizer scans of the jugular vein(repetition time, 160 ms; echo time, 5 ms; flip angle, 30°;slice thickness, 3 mm; field of view, 200×200 mm; matrix,
128×256). From axial images of the jugular vein, a second
coronal scout with a reduced slice thickness (1 mm) was
obtained along its major axis. The ligated sutures, trachea or
the carotid artery served as a landmark to position MR
cross-sectional images of the jugular vein. Three-dimensional fast asymmetric spin echo (FASE) T2-weighted
images (T2WIs) with fat suppression were acquired with arepetition time (TR) and echo time (TE) of 2000/60 ms and
120 ms, and 3D-gradient echo T1-weighted images(T1WIs) with fat suppression were acquired with a TR, TE
and flip angle (FA) of 38 ms, 5 ms and 20° and 40°. Further
MR imaging parameters included the following: field ofview, 120×120 mm; matrix, 256×256 (zero-filled interpolated to 512×512 to reduce partial-volume effects in imaging
pixels) [16]; a 3mm slice thickness; and one signal average.
The voxel size of the MR images of jugular vein thrombi was
0.47×0.47×3 mm.
2.3. Image and data analysis
The MR images (n=3 per vein) were further analyzed
using a Macintosh computer and matched with corresponding histopathological sections of jugular vein specimens.
Cursors for regions of interest defined by one observer wereplaced within the thrombus to measure cross-sectional area,
signal intensity (SI), and T1 and T2 relaxation times. The
cross-sectional area of the thrombus was determined for both
MR images by manual tracing using Image J (US National
Institutes of Health, Bethesda, MD, USA). To determine MR
SI changes in the organizing processes of venous thrombus,
we assessed the intrinsic MR properties of thrombi by measuring the SI relative to the reference muscle using theformula SI (%)=100×(SI thrombus/SI muscle) on the T2WIs
and T1WIs. The standard reference was immediately adjacent muscle tissue that was equidistant from the quadraturecoil. The SI of the thrombus was assessed in its lengthwise
central portion excluding the proximal and distal edges. The

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T1 and T2 relaxation times were derived from the following
respective equations: [17]


T1 =
ln
T2 =

TR

sinacos bIb − sinbcos aIa
sinaIb − sinbIa

TE2 − TE1 
In II122.4. Immunohistochemistry of rabbit venous thrombus
The jugular veins with thrombi were fixed in 4%
paraformaldehyde for 24 h at 4°C, embedded in paraffinand sectioned (3 μm) for staining with hematoxylin and eosin(HE), Berlin blue (Fe3+) Sirius red (collagen) and with
antibodies against platelet glycoprotein (GP) IIb/IIIa (Affinity
Biologicals Inc., Ancaster, ON, Canada), rabbit fibrin (a giftfrom Takeda Chemical Industries, Ltd., Osaka, Japan), muscle
actin (HHF35, DAKO, Glostrup, Denmark) and rabbit
macrophages (RAM11, DAKO) [18]. The sections werethen stained with Envision, anti-mouse IgG secondary
antibody and horseradish peroxidase connected with apolymer (DAKO), or donkey anti-sheep IgG secondary
antibody (Jackson ImmunoResearch, Inc., West Grove, PA,
USA). Horseradish peroxidase activity was visualized using
3,3′-diaminobenzidine tetrahydrochloride, and the sections
were faintly counterstained with Meyer's hematoxylin.
Immunostaining controls included nonimmune mouse IgG
or nonimmune sheep serum instead of the primary antibodies.
Areas of erythrocytes, iron, collagen and positive immunostaining in thrombi were analyzed using a color imaging
morphometry system (Win Roof, Mitani, Fukui, Japan).
Briefly, eosin-positive erythrocytes and Berlin-blue-positive,
Sirius-red-positive or immunopositive areas were extractedusing specific protocols based on the color parameters of hue,lightness and saturation. The data are expressed as ratios (%) of
eosin-positive erythrocytes as well as Berlin-blue-positive,
Sirius-red-positive or immunopositive regions in corresponding areas [19]. Two investigators who were blinded to thetreatment assignments performed the morphological analyses.
2.5. Effect of t-PA infusion on whole blood
coagulation parameters
Whole blood hemostatic parameters before and 30 min
after t-PA administration (600,000 U/kg/h) were measured
using a rotation thromboelastometry (ROTEM) analyzer(Pentapharm GmbH, Munich, Germany). Blood samples
were collected from the central ear artery into 3.8% sodium
citrate (9:1, vol/vol), and 300-μl portions were transferred
into the ROTEM reaction chamber. Blood clotting was
initiated using rabbit brain thromboplastin (ex-TEM, Pentapharm GmbH) and 20 μl of 200 mM CaCl2, and then clot
formation was measured in duplicate using the standard
EXTEM evaluation parameters provided by the manufacturer.

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We determined the following parameters: clotting time (CT),namely, the duration between recalcification and the start ofclot formation; maximal clot firmness (MCF) (mm); and lysis
onset time (LOT), namely, time at 75% MCF. These parameters describe the following phases of the clotting process:initiation (CT), termination/final clot strength (MCF) andfibrinolysis (LOT) [18].
2.6. Statistical analysis
All data are presented as medians and ranges, interquartile
ranges or individual dots. Differences for individual groups
were tested using the Mann–Whitney U test, the Wilcoxon
signed rank test or the Kruskal–Wallis test with Dunn's
multiple comparison test (GraphPad Prizm 4.03, GraphPad
Software Inc., San Diego, CA, USA). The degree of agreement was evaluated according to the Bland and Altman
analysis (GraphPad).
3. Results
3.1. MRI of rabbit jugular vein
Figs. 1A and B show coronal and axial sequential MR
images, respectively, of venous thrombi in the right jugularvein at 4 h and at 1, 2 and 4 weeks after endothelial denudationand vessel ligation. The thrombi at 4 h appeared asheterogeneous high or low SI on T2WI or T1WI, respectively, whereas those at 1 and 2 weeks appeared as heterogeneous high SI on both. The thrombi at 4 weeks appeared ashomogeneous low SI on T2WI and T1WI. Figs. 1C to F show
the SI values and relaxation times on axial images of venous
thrombi at 4 h and at 1, 2 and 4 weeks. The T2WI SI timedependently decreased, while T1WI SI increased in thethrombi at 1 and 2 weeks (Figs. 1C and D). The T2 and T1
relaxation times time-dependently decreased (Figs. 1E and F).
3.2. Pathological findings of venous thrombi
Fig. 2 shows thrombus areas determined by MR images
or histological sections, and their Bland–Altman plot. The
sizes of venous thrombi time-dependently decreased on MR
images and in histological sections (Figs. 2A and B). The
thrombi in MRI were comparable in size to histologicalsections (Fig. 2C).
To investigate the contents and organizing processes ofthrombus, we histologically and immunohistologicallyexamined sections of thrombi stained with hematoxylin–
eosin, anti-GPIIb/IIIa, anti-fibrin, anti-muscle actin, antirabbit macrophage antibodies, Berlin blue and Sirius red.
Fig. 3 shows the histological characteristics of the venous
thrombi at 4 h and at 1, 2 and 4 weeks after the procedures.
Thrombi at 4 h were rich in erythrocytes, platelets and fibrin
without evidence of organization, indicating fresh thrombus.
Thrombi at 1 and 2 weeks showed smooth muscle cell(SMC) proliferation and macrophage infiltration, as wellas iron and collagen deposition at the thrombus–venous

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979}

Fig. 1. Representative T2W and T1W MR images, signal intensities and relaxation times of venous thrombi induced in rabbit right jugular vein by endothelial
denudation and vessel ligation. Sequential coronal MR images of venous thrombi (arrows) at 4 h and at 1, 2 and 4 weeks (A). Sequential axial MR images ofvenous thrombi (arrows) and reference adjacent muscle at the same times (B). Thrombi on T2WI or T1WI appeared as heterogeneous high or low SI,
respectively, at 4 h, as heterogeneous high SI at 1 and 2 weeks and as homogeneous low SI at 4 weeks. Thrombus signal intensity changes over time of T2WI (C)and T1WI (D); ⁎Pb.05, ⁎⁎Pb.01, ⁎⁎⁎Pb.001; n=18 for each (Kruskal–Wallis test with Dunn's multiple comparison test). Changes in T2 (E) and T1 (F)relaxation times of thrombi over time; ⁎Pb0.05, ⁎⁎Pb.01, ⁎⁎⁎Pb.001; n=18 for each (Kruskal–Wallis test with Dunn's multiple comparison test).

wall interface, indicating organizing thrombus. Thrombi at
4 weeks were replaced by fibrous connective tissue with
SMCs, macrophages, collagen and small vessels. Iron was
localized in macrophages, indicating hemosiderin deposition. The thrombi contained minimal erythrocytes, platelets
and fibrin, indicating organized thrombus (Fig. 3A).
Replacing primary antibodies with nonimmune mouse IgG
did not elicit immunoreactivity (data not shown). Fig. 3Bshows areas in thrombi of eosin-positive erythrocytes andthose immunopositive and positive for Berlin blue and Sirius
red at 4 h and at 1, 2 and 4 weeks. Semiquantitative analysisof the thrombi showed time-dependent decreases in areas oferythrocytes, platelets and fibrin; time-dependent increases
in areas containing collagen and iron; and maximal amountsof SMC and macrophage infiltration at 2 weeks.
3.3. MRI of venous thrombi before and after
t-PA administration
We examined the thrombolytic effects of t-PA uponvenous thrombi at 4 h and at 1, 2 and 4 weeks using MRI.
Whole blood clotting kinetics assessed using ROTEM
showed obvious effects of t-PA. Both MCF and LOT sig-

nificantly decreased and shortened, respectively, indicating
increased thrombolytic activity in the blood at 30 min after
the administration of t-PA (Table 2). The administrationof t-PA significantly decreased axial areas and thrombus
volume at 4 h, but not at 1, 2 and 4 weeks (Figs. 4A, B and C).
4. Discussion
We showed here that MRI can reliably and noninvasively
detect venous thrombi in rabbit jugular veins, that sequentialchanges in SI on T2WI and T1WI reflect organizing processes in these thrombi and that those with high SI on T2WI
and low SI on T1WI respond to thrombolytic therapy.
Direct thrombus imaging using MR is a novel tool for
diagnosing DVT with higher sensitivity and specificity thancontrast venography [20,21], and MR could be superior toultrasonography and computed tomography for the determination of DVT chronicity [22]. The present findings showedthat MRI detected all thrombi created in rabbit jugularveins and that the thrombi in MR images were comparable insize to histological sections. In addition, the size of thrombi
decreased throughout the organizing process. These findings

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support the feasibility of diagnosing acute and chronic DVT
by directly visualizing thrombus on MR images.
The SI of rabbit vein thrombi time-dependently decreasedon T2WI, but increased on T1WI at 1 and 2 weeks after theprocedure. These findings are in conflict with those of a study
by Erdman et al. [14], who examined canine jugular veinsusing either T1- or T2-weighted spin echo sequences and a
0.35-T MR system. They found that the SI of the thrombi did
not change over 3 weeks. Here, we used the spoiled gradientrecalled echo sequence and a 1.5-T MR system, which could
be more sensitive to age-related changes in thrombi than the
instruments used in the Erdman study. On the other hand,similar time-dependent changes occur in T2WIs and T1WIs
of thrombi in swine or rabbit carotid arteries [23,24], but not
in fresh thrombi; the SI in T2WIs could be high because
fresh venous thrombi are rich in erythrocytes. Sequentialchanges could reflect the organizing processes of venous
thrombi, as shown by histological analysis.
The heterogeneous appearance of thrombi in T1WI and
T2WI might be due to their components, as well as to aging,
namely, the organizing process, which includes progressive
dehydration by fibrin gel, collagen production and hemosiderin depositions. The T1 and T2 relaxation times are
positively affected by tissue water content and negatively
affected by collagen and hemosiderin contents [25,26]. This
could explain why T2 and T1 relaxation times that arehigh in fresh thrombi time-dependently decrease. Others
have demonstrated that the proportion of oxy-, deoxy- andmethemoglobin generated by erythrocyte degradation affects
relaxation rates and MR images in vitro [27,28] and thatchanges in the proportion of hemoglobin contribute to agerelated changes in MR signals in hematoma [29]. Thesefindings suggest that methemoglobin formed in venous
thrombi could contribute to the time-dependent decrease in
T1 relaxation time. However, we found that T1 relaxation
time shortened at 2 and 4 weeks in venous thrombi. Since thethrombi were rich in hemosiderin deposition and contained
less erythrocytes, T1 relaxation time might be more influenced by hemosiderin than by methemoglobin. Changes
in T2 and T1 relaxation times in venous thrombi could
depend on a combination of sequential changes in the cellular and matrix components, the different oxygenation
states of hemoglobin and hemosiderin deposition.
The administration of t-PA significantly decreased
thrombus volume at 4 h, but not at 1, 2 and 4 weeks.
Although how MR signals of venous thrombi respond tothrombolytic therapy is not clearly defined, Francis andTotterman [30] showed that human DVTs with a homogeneous low SI on T1WI were most likely to respond, whereas
those with an intermediate or high intensity or a heterogeneous appearance do not. Our results suggest that venous
thrombi with high and low SI on T2WI and T1WI, respectively, are likely to respond to thrombolytic therapy. Thrombolysis likely occurs in patients with symptomatic DVT of≤4 days of duration and more often in partially than totally
occluded segments [30]. Other clinical studies have also

found that the effect of thrombolytic therapy closely correlates with thrombus age, as reflected by the duration ofclinical symptoms [8,31]. Our results support the notion that
MRI can predict and assess the effects of thrombolytic
therapy upon DVT.
The high accuracy of ultrasonography for diagnosis or
exclusion of DVT in the thighs of symptomatic patients has
been reported. However, the study can be difficult or limited
in patients with obesity, marked swelling, overlying casts
and pelvic DVT [6]. Several clinical studies were performedby using 2D TOF, phase-contrast (PC) or gadolinium-

Fig. 2. Thrombus size in MR images and histological sections, and theirBland-Altman plot. Thrombus area in MR images (n=9 each) at 4 h and at 1,
2 and 4 weeks (A); ⁎Pb.05, ⁎⁎Pb.01, ⁎⁎⁎Pb.001 (Kruskal–Wallis test with
Dunn's multiple comparison test). Thrombus area in histological sections(n=9 each) at 4 h and at 1, 2 and 4 weeks (B); ⁎Pb.05, ⁎⁎Pb.01, ⁎⁎⁎Pb.001(Kruskal–Wallis test with Dunn's multiple comparison test). The thrombi in
MR images were comparable in size to histological sections (Bland–Altman
plot analysis, bias, 0.18 mm2; S.D., 1.29 mm2) (C). Bland–Altman limits(mean of the differences±2 S.Ds. of the differences) are shown.

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Fig. 3. Immunohistochemical microphotographs and immunopositive areas of venous thrombi at 4 h and at 1, 2 and 4 weeks after endothelial denudation andvessel ligation. Representative immunohistochemical microphotographs of fixed jugular veins containing thrombi that were stained with HE, anti-GPIIb/IIIa,
anti-fibrin, anti-muscle actin, anti-rabbit macrophage antibodies, Berlin blue and Sirius red (A). Fresh venous thrombi at 4 h are rich in erythrocytes, platelets
and fibrin without organization. Venous thrombi organizing at 1 and 2 weeks showed SMC proliferation, macrophage infiltration and iron and collagendeposition at thrombus–venous wall interface (*). Organized thrombi at 4 weeks are replaced by fibrous connective tissue with SMCs, iron-laden macrophages,
collagen and small vessels. Changes in ratios of erythrocyte, platelet, fibrin, SMC, macrophage, Fe3+ and collagen areas in thrombi over time (B); ⁎Pb.05,⁎⁎Pb.01, ⁎⁎⁎Pb.001; n=9 each (Kruskal–Wallis test with Dunn's multiple comparison test).

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Fig. 3. (continued ).

Table 2Whole blood hemostatic parameters before and after t-PA administration
Parameter

CT (s)MCF (mm)
LOT (s)

Before t-PA

30 min after t-PA

Median (range) n=6Median (range) n=662 (55–73)
63 (59–68)
15,200 (9141–16,260)

56 (51–76)
43 (24–57)
331 (148–787)

Data analyzed using Wilcoxon signed rank test.

P

.31
.03
.03

enhanced MR angiography [32,33]. However, TOF and PC
techniques are time consuming and are adversely affected by
the slow, phasic flow that is typical for the peripheral venous
system. The 3D FASE method combines the half-Fourier
technique and 3D fast spin echo sequence. This method
allows reduction of the imaging time with high spatial resolution. The 3D imaging has the inherent signal-to-noise ratio
advantages, high resolution and isotropic voxels [34].
Therefore, the 3D FASE volumetric isotropic imaging data

Y. Kuroiwa et al. / Magnetic Resonance Imaging 29 (2011) 975–984
Fig. 4. Representative MR images and thrombus volume before and after t-PA administration. Representative axial MR images of venous thrombi before and 30 min after t-PA administration at 4 h and at 1, 2 and 4
weeks (A). Changes in axial area of thrombus before and 30 min after t-PA administration at 4 h and at 1, 2 and 4 weeks (B); ⁎Pb.001; n=18 per group (Wilcoxon signed rank test). Changes in thrombus volume
before and 30 min after t-PA administration at 4 h and at 1, 2 and 4 weeks (C); ⁎Pb.05; n=6 per group (Wilcoxon signed rank test).

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can be reformatted to generate high-quality, high-spatialresolution images in any plane. Using the method, thepresent study detected sequential signal change of the venous
thrombus over time and reduction of the thrombus size after
t-PA administration. The 3D FASE might be a promisingtechnique for DVT imaging.
5. Conclusion
Magnetic resonance imaging can reliably and noninvasively detect venous thrombosis, define thrombus age andpredict as well as assess the thrombolytic response in rabbit
veins. These results suggest that MRI shows promise as adiagnostic tool and as a means of predicting the effect ofthrombolytic therapy on DVT.
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