Improved diagnosis of vascular dissection by ultrasound B-flow: a comparison with color-coded Doppler and power Doppler sonography

Modified multi-Rayleigh model-based statistical analysis of ultrasound envelope for quantification of liver steatosis and fibrosis

PURPOSE

Quantitative diagnosis of the degree of fibrosis progression is currently a focus of attention for fatty liver in nonalcoholic steatohepatitis (NASH). However, previous studies have focused on either lipid droplets or fibrotic tissue, and few have reported the evaluation of both in patients whose livers contain adipose and fibrous features. Our aim was to evaluate fibrosis tissue and lipid droplets in the liver.

METHODS

We used an analytical method combining the multi-Rayleigh (MRA) model and a healthy liver structure filter (HLSF) as a technique for statistical analysis of the amplitude envelope to estimate fat and fibrotic volumes in clinical datasets with different degrees of fat and fibrosis progression.

RESULTS

Fat mass was estimated based on the non-MRA fraction corresponding to the signal characteristics of aggregated lipid droplets. Non-MRA fraction has a positive correlation with fat mass and is effective for detecting moderate and severe fatty livers. Progression of fibrosis was estimated using MRA parameters in combination with the HLSF. The proposed method was used to extract non-healthy areas with characteristics of fibrotic tissue. Fibrosis in early fatty liver suggested the possibility of evaluation. On the other hand, fat was identified as a factor that reduced the accuracy of estimating fibrosis progression in moderate and severe fatty livers.

CONCLUSION

The proposed method was used to simultaneously evaluate fat mass and fibrosis progression in early fatty liver, suggesting the possibility of quantitative evaluation for discriminating between lipid droplets and fibrous tissue in the early fatty liver.

Clinical Applications of B-Flow Ultrasound: A Scoping Review of the Literature

Coded excitation ultrasound investigations have the potential to augment the resolution, increase the efficiency, and expand the possibilities of noninvasive diagnostic imaging. B-Flow ultrasound, a type of digitally encoded imaging, was developed more than 20 years ago with the aim to optimize the visualization of blood flow. It has been investigated for a plethora of applications so far. A scoping review regarding its clinical applications was conducted based on a systematic literature research. B-Flow has been investigated in various anatomic locations and pathologies. However, previous research is limited by small sample sizes, the rare occurrence of elaborate study designs, the reliance on subjective reports and qualitative data, as well as several potential biases. While results are in general promising, it should therefore still be considered an emerging technology. Nevertheless, the limitations can be addressed in future research and the potential to expand its applications make B-Flow an interesting candidate for further investigations.

The Role of Ultrasonography in Patients Referring to the Emergency Department with Acute Abdominal Pain

CONTEXT

Acute abdominal pain is a common clinical problem in emergency and non-emergency cases accounting for 5 to 10% of all referrals to the emergency department. Studies have indicated that these widely differentiated diagnoses are common to these complaints. Considering the high prevalence of this complaint in the patients and the wide range of its differential diagnosis, this review study was designed and evaluated aiming at investigating the causes of acute abdominal pain with a focus on assessing the position of ultrasound as a diagnostic tool in the emergency department.

EVIDENCE ACQUISITION

This article was conducted as a narrative review of selected articles from 2005 through 2019. By comparing them, a comprehensive review of ultrasound role was conducted in patients with acute abdominal pain referring to the emergency department.

RESULTS

In this review study, we attempted to use the articles of the clinical approach, the required laboratory tests, the disadvantages and advantages of each imaging technique, the differential diagnosis for acute abdominal pain according to the location of the pain, and the position of ultrasound as a diagnostic aid tool. Eventually, the proposed protrusion will be considered in dealing with a patient with acute abdominal pain.

CONCLUSION

Regarding the wide range of causes providing multiple differential diagnosis, as well as the limited time of the health team in the emergency department for diagnostic and therapeutic measures, particularly in time-sensitive clinical conditions, ultrasound offered by emergency medicine specialists as a diagnostic aid is considered to improve the overall diagnosis and treatment of patients, thereby reducing complications.

B-Flow Sonography for Evaluation of Basal Cerebral Arteries in Newborns

The aim of the study was to evaluate the B‑flow sonography (BFS) to image the basal cerebral arteries in newborn infants. For this purpose 34 newborns, who underwent standardized ultrasound of the brain including BFS, color Doppler (CDS) and power Doppler (PDS) techniques were retrospectively assessed. Delineation of the anterior communicating (Acom), the posterior communicating (Pcom), the middle cerebral (M1 and M2 segments), the anterior cerebral (A1 and A2 segments), and the posterior cerebral artery (P1 and P2 segments) were visually scored. Vessel delineation was better with BFS compared with CDS and PDS for the M2 segment (p = 0.0006 and p = 0.0136) and P2 segment (p = 0.0021 and p = 0.0014). Superior detectability was also noted for the Pcom with BFS compared with PDS (p = 0.0062). For all other vessel segments no significant differences were found. In conclusion BFS is feasible to image the basal cerebral arteries in newborns with an equal or better vessel delineation compared with standard vascular ultrasound methods.

Diagnostic vascular ultrasonography with the help of color Doppler and contrast-enhanced ultrasonography

The use of ultrasonography and especially of contrast-enhanced ultrasonography (CEUS) in the diagnosis of vascular pathologies before and after interventions has significantly increased over the past years due to the broader availability of modern ultrasound systems with CEUS capabilities and more trained user experience in this imaging modality. For the preinterventional and postinterventional work-up of carotid diseases, duplex ultrasound as well as CEUS have been established as the standard-of-care examination procedures for diagnosis, evaluation, and follow-up. In addition to its use for carotid arterial diseases, ultrasonography has also become the primary modality for the screening of vascular pathologies. This review describes the most common pathologies found in ultrasonography of the carotid arteries, the abdominal aorta, and the femoral arteries.

The role of contrast-enhanced ultrasound in imaging carotid arterial diseases

The standard of care for the initial diagnosis of carotid artery bifurcation diseases is carotid duplex ultrasound. Carotid abnormalities or difficult examinations may represent a diagnostic challenge in patients with clinical symptoms as well as in the follow-up after carotid endarterectomy, carotid artery stenting or other interventions. A promising new method in the diagnosis and follow-up of pathologic carotid diseases is contrast-enhanced ultrasound (CEUS). In comparison with magnetic resonance imaging or computed tomography, the contrast agents used for CEUS remain within the vascular space and hence can be used to study vascular disease and could provide additional information on carotid arterial diseases. This review describes the current carotid duplex ultrasound examination and compares the pathologic findings with CEUS.

Clinical characteristics of symptomatic vertebral artery dissection: a systematic review

BACKGROUND

Vertebral artery dissection (VAD) is an important cause of stroke in the young. It can present nonspecifically and may be misdiagnosed with adverse consequences. We assessed the frequency of head/neck pain, other neurological symptoms, and cerebrovascular events in symptomatic VAD.

METHODS

We conducted a systematic review of observational studies, searching electronic databases (MEDLINE, EMBASE) for English-language manuscripts with >5 subjects with clinical or radiologic features of VAD. Two independent reviewers selected studies for inclusion; a third adjudicated differences. Studies were assessed for methodological quality, and clinical data were abstracted. Pooled proportions were calculated.

RESULTS

Of 3996 citations, we screened 511 manuscripts and selected 75 studies describing 1972 VAD patients. The most common symptoms were dizziness/vertigo (58%), headache (51%), and neck pain (46%). Stroke was common (63%), especially with extracranial dissections (66% vs. 32%, P<0.0001), whereas transient ischemic attack (14%) and subarachnoid hemorrhage (10%) were uncommon. Subarachnoid hemorrhage was seen only with intracranial dissections (57% vs. 0%, P=0.003). Fewer than half of the patients had obvious trauma, and only 7.9% had a known connective tissue disease. Outcome was good (modified Rankin scale 0 to 1) in 67% and poor (modified Rankin scale 5 to 6) in 10% of patients.

CONCLUSIONS

VAD is associated with nonspecific symptoms such as dizziness, vertigo, headache, or neck pain. Ischemic stroke is the most common reported cerebrovascular complication. VAD should be considered in the diagnostic assessment of patients presenting with dizziness or craniocervical pain, even in the absence of other risk factors. Future studies should compare clinical findings as predictors in well-defined, undifferentiated populations of clinical VAD suspects.

Contrast-enhanced ultrasound performed under urgent conditions. Indications, review of the technique, clinical examples and limitations

Contrast-enhanced ultrasound (CEUS) is an imaging technique with various indications, most of which refer to scheduled examinations. However, CEUS can also be performed under urgent conditions for the investigation of many different clinical questions. This article reviews basic physics of ultrasound contrast agents and examines the commonest urgent clinical applications of CEUS. These include, among others, abdominal solid organ trauma and infarcts, scrotal and penile pathology and blood vessel imaging. Patients can be examined with a very short time delay at their bedside, without exposure to ionising radiation or risk of anaphylactic reaction and renal failure, while contraindications are minimal. CEUS technique is described for various urgent indications and imaging examples from our department's experience are presented. Safety matters and limitations of CEUS are also mentioned. Teaching Points • Contrast-enhanced ultrasound (CEUS) can be performed urgently for various clinical applications. • Abdominal indications include solid organ trauma and infarcts. • CEUS in abdominal organ trauma correlates well with CT and can replace it for patient follow-up. • CEUS images testicular torsion, infection and infarction, as well as testicular and penile trauma. • Blood vessels can be assessed with CEUS for obstruction, aneurysm, thrombosis and dissection.

Transoral carotid ultrasonography using a micro convex probe with B-flow imaging for extracranial internal carotid artery dissection

We report on transoral carotid ultrasonography using a micro convex probe with B-flow imaging for determining spontaneous extracranial internal carotid artery dissection just below the petrous portion. A 49-year-old man suffered cortical and subcortical infarction in the region of the right middle cerebral artery. Magnetic resonance angiography on the third day of admission revealed spontaneous recanalization of the right internal carotid artery associated with an intimal flap-like structure at the petrous portion. Transoral carotid ultrasonography using a micro convex probe revealed right extracranial internal carotid artery dissection, showing an increased diameter of the right extracranial internal carotid artery with double lumen formation, stenosis of the true lumen, and a mobile intimal flap in B-flow imaging. Transoral carotid ultrasonography using a micro convex probe was helpful to attempt a self-expanding stent for recanalizing right extracranial internal carotid artery dissection. The patient recovered and was discharged ambulatory. The size of the micro convex probe was optimum for transoral carotid ultrasonography in our patient. Micro convex probe is more commonly used than the standard transoral carotid ultrasonography probe, which lacks versatility. We consider that transoral carotid ultrasonography using a micro convex probe could be routinely used for ultrasonographic evaluation of extracranial internal carotid artery dissection.

Imaging of carotid arterial diseases with contrast-enhanced ultrasound (CEUS)

Carotid duplex ultrasound is the standard of care for the initial diagnosis of carotid artery bifurcation diseases. But in difficult examinations, carotid abnormalities are commonly encountered and may represent a diagnostic challenge in patients with clinical symptoms as well as in the follow up after carotid endarterectomy or carotid artery stenting. Contrast enhanced ultrasound (CEUS) with low mechanical index (low MI) is a promising new method in the diagnosis and follow up of pathological carotid diseases. Unlike most contrast agents used for magnetic resonance imaging or computed tomography, the microbubbles used in CEUS with SonoVue(®) remain within the vascular space and hence can be used to study vascular disease. In addition to improving current carotid structural scans, CEUS has potential to improve or add extra information on carotid arterial diseases. This review describes the current carotid duplex ultrasound examination and compares the pathological findings with CEUS.

[Color duplex sonography of extracranial brain-supplying arteries]

Ultrasound examination of extracranial blood-supplying arteries allows the simultaneous acquisition of morphologic and hemodynamic information with high spatial and temporal resolution. For detection and quantification of stenoses in the carotid and vertebral arteries, an intrastenotic peak systolic velocity of more than 120 cm/s is the threshold value for a diameter reduction of >50%. In addition there are further direct and indirect stenosis parameters (intrastenotic and poststenotic circulation disturbance, increased pulsatility in the prestenotic common carotid artery, intracranial or extracranial collateral pathways) which together with diameter and area reduction in the B-scan, lead to a high reliability of color duplex sonography for stenoses of the internal carotid artery (ICA). Sonographic and patho-anatomic comparative studies have shown a high agreement (r >0.9) by using a battery of several ultrasound criteria. Following stenting of the ICA the blood flow velocity in the stent is generally increased so that a > or =70% in-stent restenosis is present in case of a peak systolic velocity of 300-450 cm/s. For the description of arteriosclerotic plaques in the B-scan, ultrasound terminology but not histological terms should be used to describe the internal, surface and motion structure of plaques as well as the sonic shadow formation.

[Current developments in vascular ultrasound]

Ultrasound plays a central role in the diagnostic imaging of venous and arterial vessels, especially for the assessment or exclusion of arteriosclerotic vessel obstructions as well as venous or arterial thrombosis. Due to its excellent patient acceptance and its broad availability, ultrasound is considered the standard method of choice for vascular imaging. New techniques and methods have greatly enhanced its diagnostic accuracy, the most notable of which are the B-flow technique, a variant of Doppler signal read-out for reduction of artifacts in duplex sonography, as well as other techniques, such as tissue harmonic imaging, the cross-beam technique and the speckle-reduction technique, which employ different echo processing methods for contrast improvement and enhanced delineation of body structures adjacent to the vessels. The introduction of contrast enhanced ultrasound represents an important advancement and has brought a substantial improvement in sensitivity. This article describes and discusses these new techniques and methods of vascular ultrasound diagnostics with respect to their diagnostic value.

[Ultrasound imaging of the abdominal aorta]

Abnormalities of the abdominal aorta and the visceral vessels can represent a diagnostic challenge in patients with both acute and chronic clinical symptoms. In addition to the primary conventional examination using color-coded duplex ultrasound, contrast-enhanced ultrasound (CEUS) with low mechanical index (low MI) may contribute to achieving a precise diagnosis. CEUS is a new and promising method in the diagnosis and follow-up of aortic and visceral artery lesions. Color-coded duplex ultrasound and CEUS with SonoVue(R) allow a rapid and non-invasive diagnosis especially in critically ill patients as these methods can readily be applied at the bedside. In this article the contribution of color-coded duplex ultrasound and CEUS as compared to multi-slice computed tomography angiography (MS-CTA) in various pathologies of the abdominal aorta and the visceral arteries will be addressed.

The RUSH exam: Rapid Ultrasound in SHock in the evaluation of the critically lll

The RUSH exam (Rapid Ultrasound in SHock examination), presented in this article, represents a comprehensive algorithm for the integration of bedside ultrasound into the care of the patient in shock. By focusing on a stepwise evaluation of the shock patient defined here as "Pump, Tank, and Pipes," clinicians will gain crucial anatomic and physiologic data to better care for these patients.

Treatment of secondary stent-graft collapse after endovascular stent-grafting for iliac artery pseudoaneurysms

We report the case of a patient who developed an asymptomatic pseudoaneurysm in the left external iliac artery after transplant nephrectomy. The pseudoaneurysm most probably arose as a suture aneurysm from the external iliac artery after removal of the graft renal artery. Obviously we can not exclude the possibility it was a true aneurysm, although this seems much less likely. The pseudoaneurysm was detected during a routine CT scan and was treated interventionally with a stent-graft. One month later the asymptomatic patient underwent a vascular ultrasound examination including color Doppler, power Doppler, and B-flow as a routine control. An endoleak with collapse of the stent-graft was diagnosed. There was no evidence of stent infection. At a reintervention, the pseudoaneurysm was successfully treated using two uncovered Palmaz stents at the proximal and distal edge of the stent graft. Peri- and post-interventional ultrasound and CT angiography confirmed the exclusion of the aneurysm without an endoleak.

[Ultrasound diagnosis of vascular complications following transfemoral puncture]

Percutaneous catheter interventions are performed increasingly often for the purposes of both diagnosis and therapy. The incidence of local complications reported after transfemoral catheterization in the literature is 0.1-9%. Such complications should be detected as early and reliably as possible, and sonography is a good means of finding them during follow-up, not least because it is suitable for use in examinations at the bedside. The clinical value of sonography compared with other examination techniques is made clear with reference to specimen cases.

Blunt cervical spine trauma as a cause of spinal cord injury and delayed cortical blindness

STUDY DESIGN

Case report.

OBJECTIVE

To present and discuss the case of a patient who sustained a significant flexion compression injury of the cervical spine with resulting tetraplegia and development of cortical blindness.

SETTING

National Spinal Injuries Unit and Institute of Neurological Sciences, Southern General Hospital, Glasgow, Scotland, UK.

METHODS

Clinical and radiological follow-up of the patient.

RESULTS

Cortical blindness resulted from vertebral artery dissection associated with blunt cervical spine trauma. The patient is registered blind and is ventilator dependent.

CONCLUSION

The potential complications of blunt vertebral artery injury remain poorly recognised. Screening is routinely not performed. Advances in noninvasive radiological techniques may result in recognition of asymptomatic disease and the potential for therapeutic intervention.

Color Doppler, power Doppler and B-flow ultrasound in the assessment of ICA stenosis: Comparison with 64-MD-CT angiography

The purpose of this study is to investigate the diagnostic potential of color-coded Doppler sonography (CCDS), power-Doppler (PD) and B-flow ultrasound in assessing the degree of extracranial internal carotid artery (ICA) stenosis in comparison to CT-angiography (MD-CTA). Thirty-two consecutive patients referred for CTA with 41 ICA-stenoses were included in this prospective study. MD-CTA was performed using a 64 row scanner with a CTDIvol of 13.1 mGy/cm. In CTA, CCDS, PD and B-flow, the degree of stenosis was evaluated by the minimal intrastenotic diameter in comparison to the poststenotic diameter. Two radiologists performed a quantitative evaluation of the stenoses in consensus blinded to the results of ultrasound. These were correlated to CTA, CCDS, PD and B-flow, intraoperative findings and clinical follow-up. Grading of the stenoses in B-flow ultrasound outperformed the other techniques in terms of accuracy with a correlation coefficient to CTA of 0.88, while PD and CCDS measurements yield coefficients of 0.74 and 0.70. Bland-Altman analysis additionally shows a very little bias of the three US methods between 0.5 and 3.2 %. There is excellent correlation (coefficient 0.88, CI 0.77-0.93) with 64-MD-CTA and B-flow ultrasound in terms of accuracy for intrastenotic and poststenotic diameter. Duplex sonography is useful for screening purposes.

Practical noninvasive neurovascular imaging of the neck arteries in patients with stroke, transient ischemic attack, and suspected arterial disease that may lead to ischemia, infarction, or flow abnormalities

Stroke is the third leading cause of death in the United States, killing nearly 157,000 people a year with an estimated society cost of dollar 58 billion in 2006. A large percentage of ischemic strokes is secondary to extracranial carotid and vertebral arterial disease. While digital subtraction angiography has traditionally been used for the initial evaluation of the degree of stenosis, noninvasive imaging has moved to the forefront in the extracranial arterial evaluation. The importance of understanding the imaging techniques, findings, interpretation, artifacts, and pitfalls is essential to appropriate patient management.

Diagnostics and characterisation of preocclusive stenoses and occlusions of the internal carotid artery with B-flow

The purpose was to evaluate whether B-flow can improve the ultrasonographic diagnosis of preocclusive stenosis and occlusion of the internal carotid artery (ICA) compared with colour-coded Doppler and power Doppler. Ninety patients with occlusions or preocclusive stenoses of the ICA suspected by Doppler sonography were examined with B-flow in comparison with colour-coded Doppler sonography (CCDS), power Doppler (PD) and intra-arterial digital subtraction angiography (DSA). Intrastenotic flow detection and lengths of stenoses were the main criteria. Ulcerated plaques found by surgery in 42/90 patients were compared by ultrasonography (US). Diagnosis of ICA occlusion with CCDS, PD and B-flow was correct in all 42 cases. A preocclusive ICA stenosis in DSA was detected correctly in all 48/48 cases (100%) for B-flow, in 44/48 (92%) for PD and in 39/48 (81%) for CCDS. Surgical findings showed in 17/42 cases ulcerated plaques; 15/17 (89%) of these cases were detected with B-flow, 12/17 (71%) with PD, 10/17 (59%) with CCDS, and 8/17 (47%) with DSA. With B-flow the extent of stenosis was appraised more precisely than with PD and CCDS (P<0.0001). In conclusion, B-flow is a reliable method for preocclusive stenosis of the ICA with less intrastenotic flow artefacts. B-flow facilitates the characterization of plaque morphologies.

[Cervical arteries dissection: diagnostic Color Doppler US criteria at the acute phase]

PURPOSE

To estimate the value of duplex color-coded ultrasonography in the initial diagnosis of acute cervical artery dissection.

MATERIAL AND METHOD

Retrospective study of 31 patients, mean age 45, sex ratio=1, referred for clinical suspicion of cervical artery dissection, confirmed by MRI. 46 dissected arteries were imaged. Ten patients presented multiple dissections. The evaluated sonographic diagnostic criteria were the direct signs of intra-mural hematoma: localized increased diameter of the artery, narrowed lumen, hypo and/or isoechoic intra-mural hematoma, intimal flap. The associated criteria studied were: the location of intra-mural hematoma and in case of an occlusion, the dissection of an other artery.

RESULTS

We analyzed separately the arterial segments visualized in B-mode ultrasound (supra-bulbar internal carotid artery, vertebral artery from V0 to V3) and the arterial segments evaluated only by pulsed Doppler (intrapetrosal carotid artery, V3-V4 of the vertebral artery). With the above criteria, on arterial segments visualized in B-mode ultrasound, the diagnosis of dissection was done in 83% of cases during the initial examination but in only 30% of the arterial segments non visualized on ultrasonography.

CONCLUSION

The direct signs of intra-mural hematoma on internal carotid and vertebral segments imaged by B-mode ultrasonography have a good sensitivity. Because results were compared to MRI, the specificity could not be assessed. In case of occlusion of an artery, multiple dissections are a strong argument for the diagnosis.

B-flow imaging in low cervical internal carotid artery dissection

OBJECTIVE

Generally, the vascular ultrasonographic examination is the first method in evaluation of internal carotid artery (ICA) dissection. B-flow imaging (BFI), conversely, is a newer method of vascular ultrasonography. The objective of this study was to assess the accuracy and efficacy of BFI for the diagnosis of low cervical ICA dissection.

METHODS

Seventeen consecutive patients with 18 angiographically confirmed low cervical ICA dissections and 16 nondissected ICAs were studied with BFI and color Doppler ultrasonography (CDU). The results were compared with those of digital subtraction angiography.

RESULTS

The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of BFI in diagnosis of low ICA dissection were 94%, 94%, 94%, 94%, and 95%, respectively. Corresponding results for CDU were 83%, 94%, 94%, 83%, and 88%. B-flow imaging more precisely showed the intimal flap and the visualization of flow within the true and false lumens. In dissected carotid arteries, 6 intimal flaps were diagnosed with CDU, and 15 intimal flaps were diagnosed with BFI. The agreement between the observers in determining low cervical ICA dissection by BFI was found to be excellent (kappa = 0.80 for intramural hematoma; kappa = 0.93 for intimal flap).

CONCLUSIONS

B-flow imaging seems to be a new reliable vascular ultrasonographic technique for evaluation of low cervical ICA dissection.

Three-dimensional and four-dimensional fetal echocardiography: a new frontier

PURPOSE OF REVIEW

One of the difficulties of conventional two-dimensional cardiac imaging is the inability to examine fetal cardiac anatomy from multiple angle planes. Three-dimensional and four-dimensional ultrasound allows the fetal examiner to more accurately accomplish this task. Currently, multiple disciplines may be involved in the examination of the fetal heart (pediatric cardiologists, obstetricians, maternal-fetal medicine specialists, and radiologists). The three-dimensional and four-dimensional imaging equipment used by these specialty physicians varies greatly. The purpose of this communication is to review techniques using three-dimensional and four-dimensional imaging that the pediatric cardiologist may not be exposed to in the clinical environment, however, in consulting with colleagues needs to have an understanding of these imaging modalities.

RECENT FINDINGS

The reconstruction of cardiac structures using this technology allows the examiner to view cardiac anatomy in a manner that was limited by previous two-dimensional imaging. Volume datasets are obtained in the three-dimensional static mode (no cardiac motion) or using four-dimensional - the three-dimensional heart is observed contracting during one or multiple cardiac cycles. Therefore, the fourth dimension is time. Using either three-dimensional or four-dimensional technology datasets are acquired, followed by image reconstruction. The image reconstruction enables the examiner to evaluate a two-dimensional image using multiple views, evaluate intracardiac anatomy at different depth planes, and recreate casts of blood flow of the chambers and great vessels.

SUMMARY

This new technology has enhanced the ability of the examiner to identify normal and complex fetal heart anatomy during the early second to the late third trimesters of pregnancy.

Imaging the vertebral artery

Although conventional intraarterial digital subtraction angiography remains the gold standard method for imaging the vertebral artery, noninvasive modalities such as ultrasound, multislice computed tomographic angiography and magnetic resonance angiography are constantly improving and are playing an increasingly important role in diagnosing vertebral artery pathology in clinical practice. This paper reviews the current state of vertebral artery imaging from an evidence-based perspective. Normal anatomy, normal variants and a number of pathological entities such as vertebral atherosclerosis, arterial dissection, arteriovenous fistula, subclavian steal syndrome and vertebrobasilar dolichoectasia are discussed.