MR imaging of portal vein thrombosis

MR imaging is emerging as a potential means of detecting portal venous thrombosis (PVT). Therefore, we attempted to establish specific criteria with which to diagnose PVT on conventional spin-echo images. In a retrospective review of 342 consecutive abdominal MR scans performed with a 0.5-T magnet, we identified nine patients with persistent signal in the portal vein and used the findings in these patients to establish criteria with which to diagnose PVT. We subsequently applied these criteria to 109 additional consecutive abdominal MR scans performed with the same magnet. Fifteen cases were found in which all images showed either (1) signal involving the entire width of the portal vein lumen, which approximated (with T1 weighting) and exceeded (with T2 weighting) the intensity of the hepatic parenchyma in images in which the hepatic veins showed a complete flow void or (2) complete nonvisualization of the portal vein and its major branches in images that showed a flow void in portal venous collaterals and hepatic veins. All patients had unequivocal findings of PVT on at least one other imaging study (CT or sonography) or at surgery. Although the sensitivity of these signs could not be calculated, their specificity was 100%. We conclude that in the presence of these signs, the diagnosis of PVT can be made with confidence.     

Deep vein thrombosis following calf strain: a case study

Deep vein thrombosis (DVT) has been the subject of considerable media attention after a number of deaths and scares in apparently low risk individuals following long haul flights. While many contributory factors have been put forward for the development of DVT, few cases have been reported following muscle strain. The recent publicity surrounding the calf strain sustained by Steve Waugh, the Australian cricket captain, during the Ashes series was initially unremarkable. The case was however, subsequently complicated by the development of DVT following his return (long haul) flight to Australia. Latest reports indicate that following anticoagulant treatment he has made a full recovery and returned to playing. This case could easily be dismissed as a ‘one off’ or an unusual set of circumstances. The following case report illustrates that DVT following calf strain is by no means unique. The ramifications of these cases may have serious implications for Physicians and manual therapists working in sports medicine.     

Portal vein thrombosis: imaging features and associated etiologies.

Thrombosis of the portal vein and its splanchnic tributaries is often unsuspected clinically and may be recognized only after imaging studies of the abdomen are performed for other reasons. Radiologists should be aware of the clinical situations that predispose a patient to portal or mesenteric vein thrombosis and should also be able to recognize the sequelae of chronic thrombosis. Different modalities can be used to image the patient with portal vein thrombosis; each has its strengths and drawbacks. This paper discusses the conditions that predispose to portal and mesenteric vein thrombosis, differentiating intrahepatic portal vein occlusion secondary to liver disease from extrahepatic portal vein occlusion associated with a normal liver. The imaging features of portal vein thrombosis, its associated causes and sequelae will be reviewed as demonstrated on computed tomography (CT), ultrasound, magnetic resonance imaging (MRI), angiography, and plain film.     

Colour Doppler flow imaging ultrasonography versus venography as screening method for asymptomatic postoperative deep venous thrombosis

Objective: To evaluate colour Doppler flow imaging ultrasonography (CDFI), compared with venography, as a screening method for postoperative deep venous thrombosis (DVT) in a clinical trial on thromboprophylaxis. Methods: Patients undergoing major abdominal or thoracic surgery were prospectively screened for DVT by CDFI. Patients were examined preoperatively, and on postoperative days 1, 3, 7, 14, 21, and 28. When the CDFI was positive venography was performed. Bilateral venography was performed on day 28 in all patients. The study group comprised 82 patients who underwent CDFI and venography on the same day: four because of suspected DVT (positive CDFI), and 78 on day 28 according to protocol. Results: DVT was detected by venography in seven patients, in three of whom CDFI was positive. CDFI was falsely positive in one case. There were two popliteal and five calf DVTs, of which CDFI detected one and two, respectively. The sensitivity of CDFI was 43%, the specificity 99%. The PVpos for CDFI was 75%, and the PVneg 96%. Conclusion: Due to low sensitivity, CDFI cannot stand alone as a screening method for asymptomatic postoperative DVT.     

Colour doppler flow imaging of the carotid arteries

Summary 53 patients with carotid artery atherosclerosis were examined by colour Doppler flow imaging. These results were compared with real time duplex sonography and continuous wave Doppler sonography. In 48 low degree stenoses (<50%) the B-mode showed 36 smooth and 12 ulcerated plaque surfaces. In 24 high degree stenoses (>50%) 10 plaques were smooth and 14 ulcerated. In the low degree stenoses, which exhibited smooth surfaces in B-mode examination, colour flow Doppler showed nine additional cases with turbulences in the area of the stenotic site. This indicates that plaque ulcerations in low degree stenoses are underestimated. In contrast, in nearly all cases with high degree stenoses marked turbulences could be demonstrated by colour Doppler flow imaging independent of the B-mode showing regular or ulcerated plaque surfaces. Additionally, the duplex ultrasound diagnosed a carotid artery occlusion in 11 cases, but the colour coded Doppler was able to assess a remaining blood flow in two out of these 11 cases. Our results suggest that the colour Doppler flow imaging as a noninvasive technique is an advantage in diagnosing plaque ulcerations and it is more precise in diagnosing carotid occlusions than duplex-sonography is.     

Colour Doppler flow imaging of focal hepatic lesions

Fifty-four patients with focal liver lesions were evaluated with colour Doppler flow imaging (CDFI) and CT to assess whether CDFI could be used to differentiate various types of lesions based on the flow pattern in terms of peritumoral and intratumoral blood flow. Peritumoral flow was found to be of no significance in the differential diagnosis of various liver lesions. Intratumoral flow was graded into mild, moderate or marked depending on the relative number of blood vessels demonstrated within the lesion. Marked intratumoral flow on CDFI was seen in 12.5% of primary hepatic malignancies and in infantile haemangioendothelioma, while a moderate flow pattern was seen in 56.2% of primary hepatic malignancies and in 18.7% of metastases. Mild flow was seen in 33.3% of primary malignancies; 18.7% of metastases; and 16.7% of haemangiomas. No intratumoral flow was seen in 100% of inflammatory lesions; 83.3% of haemangiomas; 62.5% of metastases; and only one hepatocellular carcinoma (5.6%). It was therefore concluded that the presence or absence of flow on CDFI is not a reliable feature for differential diagnosis of focal liver lesions when it is used alone. The flow pattern as assessed on CDFI may point to the nature of the lesion and, when used along with other morphological imaging features, can assist in diagnosis or in narrowing the list of different diagnoses in a particular clinical situation.     

Diagnosis of portal vein thrombosis: value of color Doppler imaging.

This study was undertaken to determine the accuracy of color Doppler imaging in the diagnosis of portal vein thrombosis. Two hundred fifteen patients were studied with color Doppler imaging to determine patency of the main portal vein. Sonographic findings were confirmed in 75 patients, aged 19 to 66 years. Correlation with angiography was obtained in 13 patients, and surgical correlation was obtained in the remaining 62. Nine patients had portal vein thrombosis on the basis of these gold standards. Sonograms were classified as showing either patency or thrombosis, depending on the ability to show color flow within the main portal vein. Agreement between sonography and angiography or surgery was found in 69 patients (61 patent, eight thrombosed). One patient with a patent portal vein at sonography was found to have a thrombosed vessel at surgery, whereas five patients without portal venous flow at sonography had patent vessels at angiography (one patient) or surgery (four patients). Overall sensitivity and specificity for detection of portal vein thrombosis were 89% and 92%, with an accuracy of 92%, a false-negative rate of 0.11, a negative predictive value of 0.98, and a positive predictive value of 0.62. We postulate that the majority of errors in our study occurred in vessels that, although patent, had only sluggish flow, which could not be resolved because of technical limitations. We conclude that color Doppler imaging is a valuable screening procedure for the assessment of portal vein patency. If the sonogram shows a patent portal vein, no further studies are required. However, a lack of demonstrable flow does not always indicate thrombosis, and other imaging studies should be performed for confirmation.     

下肢深静脉血栓形成的分子影像学进展

深静脉血栓形成（DVT）是指血液在深静脉内非正常凝结,属于下肢静脉回流障碍性疾病,若不能及时诊断和处理,多数会演变为血栓形成后遗症,严重者可并发肺栓塞危及生命。医学影像学在诊断、评估DVT风险等方面具有十分重要的作用。在超声、CT等传统影像学技术的基础上,基于不同靶点和示踪剂的分子影像学技术已经在DVT诊断中得到了广泛的研究。笔者就DVT诊断相关靶点和示踪剂的研究进展予以综述。     

Colour flow imaging of the great intracranial arteries in infants

Summary Colour flow imaging was used for the visualisation of the great intracranial arteries in 100 healthy infants. All children were investigated by computersonography with a 5 MHz linear transducer. Simultaneous imaging of brain tissue, displayed in gray scale and flow, displayed in colour was possible. Flow towards the transducer was displayed in red, flow away from the transducer in blue. The following arteries could be shown in sagittal and coronal sections: anterior cerebral artery, both internal carotid arteries, the basilar artery, both vertebral arteries and the posterior cerebral arteries. The middle cerebral artery could only be shown in axial sections through the temporal bone. With the help of colour flow imaging the exact course of the great intracranial arteries can be shown. Precise placement of the sample volume as well as angle correction is possible when absolute flow velocities are measured by pulsed dopplersonography. Congenital vascular abnormalities can be visualised within the image.     

下肢深静脉血栓形成的影像诊断研究进展

下肢深静脉血栓形成(deep vein thrombosis,DVT)是指血液在下肢深静脉内异常凝结。深静脉血栓形成可发生于下肢、肝脏、盆腔等部位的静脉,发生于下肢及盆腔静脉的约占90%,尤以下肢多见。DVT是较为常见的周围血管疾病,在发达国家的发病率约为0·1%[1]。在我国其发病率虽尚无确切     

Isolated calf vein thrombosis: comparison of MR venography and conventional venography after initial sonography in symptomatic patients.

RATIONALE AND OBJECTIVES: The authors performed this study to compare magnetic resonance (MR) venography and conventional venography in the diagnosis of deep venous thrombosis (DVT) in the calf after sonography. MATERIALS AND METHODS: Sonography was performed in 595 patients who were suspected of having lower-extremity DVT. Patients with positive above-knee duplex sonograms, allergy to iodinated contrast material, renal insufficiency, or cardiac pacemakers and patients who were obese were excluded. The remaining 73 patients were asked to undergo MR venography and conventional venography. All studies were to be performed within 48 hours of the clinical diagnosis and according to standard clinical practice. Images were interpreted by radiologists who were blinded to the results of other modalities. Two separate analyses were performed: one in which conventional venography was used as the standard of reference, and one in which the presence of at least two positive studies for thrombus was considered diagnostic. RESULTS: Although 36 patients agreed to participate in the study, only 14 underwent MR venography and conventional venography within 48 hours of the clinical diagnosis. With use of any two positive studies for confirmation, acute DVT was diagnosed in three patients. Conventional venography depicted two of the three cases, whereas sonography and MR venography each depicted all three. The findings were concordant in only five of the 14 patients. CONCLUSION: Moderate discrepancy among modalities was demonstrated. This suggests radiologists should undertake comparisons among these three modalities for the detection of calf DVT. In patients with a high clinical suspicion, a second modality may be useful if the initial study is negative.     

Calcified external iliac vein thrombosis.

Linear calcification in the soft tissues of the pelvis in the region of the external iliac vein should suggest the possibility of calcified external iliac vein thrombosis, particularly in patients with a suspicious clinical history or physical findings. Extremity and pelvic venography corroborate the plain film findings.     

Monitoring of therapy for deep vein thrombosis using magnetic resonance imaging

Magnetic resonance imaging using limited-flip-angle, gradient refocused pulse sequences has been used to monitor the course of anticoagulant or fibrinolytic therapy for deep vein thrombosis in two patients. The findings demonstrate the capacity of this technique to delineate the extent of thrombosis and characterize changes in size in response to treatment. Advantages of this approach include high anatomic resolution, speed of examination and non-invasiveness, properties that make it well-suited to following the progress of therapy with potentially significant implications for improving treatment.     

Cortical vein thrombosis: the diagnostic value of different imaging modalities

Introduction  

Cortical vein thrombosis (CVT) is a rare disorder, and its diagnosis is challenging. The aim of our study was to evaluate the value of different imaging modalities for the detection of CVT.     

Ultrasonographic demonstration of portal vein thrombosis.

For screening patients suspected of having portal vein thrombosis, the ultrasound examination is simple to perform, noninvasive, and can be accomplished rapidly. Three patients were studied in whom ultrasound examination revealed portal vein thrombosis that was subsequently confirmed by angiography or surgery. Ultrasonic findings in a series of 100 randomly selected patients are summarized.     

Colour Doppler imaging of arteriovenous malformation of the vein of Galen in a newborn

Summary We report a neonate with congestive heart failure due to a huge arteriovenous malformation of the vein of Galen. Two dimensional ultrasound showed a large cystic structure behind the 3rd ventricle and the quadrigeminal plate. The cyst compressed the posterior part of the 3rd ventricle and the aqueduct and caused an obstructive hydrocephalus. The diagnosis was established by colour Doppler imaging (CDI). With the help of CDI, flow within the aneurysm could be shown as well as feeding arteries originating from the posterior and middle cerebral arteries. The straight sinus and the torcular Herophili were markedly dilated.     

The specificity of renal vein thrombosis.

Clinical and roentgenographic features of renal vein thrombosis are discussed. The authors' experience with 17 cases is presented. The roentgenologist with a high degree of suspicion can, by correlation of clinical and urographic findings, make the specific diagnosis of renal vein thrombosis in a high percentage of cases.