Reflux venous flow in dural sinus and internal jugular vein on 3D time-of-flight MR angiography

Introduction

Reflux venous signal on the brain and neck time-of-flight magnetic resonance angiography (TOF MRA) is thought to be related to a compressed left brachiocephalic vein. This study is aimed to assess the prevalence of venous reflux flow in internal jugular vein (IJV), sigmoid sinus/transverse sinus (SS/TS), and inferior petrosal sinus (IPS) on the brain and neck TOF MRA and its pattern.

Methods

From the radiology database, 3,475 patients (1,526 men, 1,949 women, age range 19–94, median age 62 years) with brain and neck standard 3D TOF MRA at 3 T and 1.5 T were identified. Rotational maximal intensity projection images of 3D TOF MRA were assessed for the presence of reflux flow in IJV, IPS, and SS/TS.

Results

Fifty-five patients (1.6 %) had reflux flow, all in the left side. It was more prevalent in females (n?=?43/1,949, 2.2 %) than in males (n?=?12/1,526, 0.8 %) (p?=?0.001). The mean age of patients with reflux flow (66 years old) was older than those (60 years old) without reflux flow (p?=?0.001). Three patients had arteriovenous shunt in the left arm for hemodialysis. Of the remaining 52 patients, reflux was seen on IJV in 35 patients (67.3 %). There were more patients with reflux flow seen on SS/TS (n?=?34) than on IPS (n?=?25).

Conclusion

Venous reflux flow on TOF MRA is infrequently observed, and reflux pattern is variable. Because it is exclusively located in the left side, the reflux signal on TOF MRA could be an alarm for an undesirable candidate for a contrast injection on the left side for contrast-enhanced imaging study.     

Non-contrast-enhanced 4D MR angiography with STAR spin labeling and variable flip angle sampling: a feasibility study for the assessment of Dural Arteriovenous Fistula

Introduction

This study aimed to evaluate the feasibility of non-contrast-enhanced 4D magnetic resonance angiography (NCE 4D MRA) with signal targeting with alternative radiofrequency (STAR) spin labeling and variable flip angle (VFA) sampling in the assessment of dural arteriovenous fistula (DAVF) in the transverse sinus.

Methods

Nine patients underwent NCE 4D MRA for the evaluation of DAVF in the transverse sinus at 3 T. One patient was examined twice, once before and once after the interventional treatment. All patients also underwent digital subtraction angiography (DSA) and/or contrast-enhanced magnetic resonance angiography (CEMRA). For the acquisition of NCE 4D MRA, a STAR spin tagging method was used, and a VFA sampling was applied in the data readout module instead of a constant flip angle. Two readers evaluated the NCE 4D MRA data for the diagnosis of DAVF and its type with consensus. The results were compared with those from DSA and/or CEMRA.

Results

All patients underwent NCE 4D MRA without any difficulty. Among seven patients with patent DAVFs, all cases showed an early visualization of the transverse sinus on NCE 4D MRA. Except for one case, the type of DAVF of NCE 4D MRA was agreed with that of reference standard study. Cortical venous reflux (CVR) was demonstrated in two cases out of three patients with CVR.

Conclusion

NCE 4D MRA with STAR tagging and VFA sampling is technically and clinically feasible and represents a promising technique for assessment of DAVF in the transverse sinus. Further technical developments should aim at improvements of spatial and temporal coverage.     

Follow-up of coiled intracranial aneurysms: comparison of 3D time-of-flight and contrast-enhanced magnetic resonance angiography at 3T in a large, prospective series

Objectives

To compare 3D-TOF magnetic resonance angiography (MRA) and contrast-enhanced MRA (CE-MRA) sequences at 3T in the follow-up of coiled aneurysms with digital subtracted angiography (DSA) as the gold standard.

Methods

DSA, 3D-TOF and CE-MRA were performed in a prospective series of 126 aneurysms in 96 patients (57 female, 39 male; age: 25–75 years, mean: 51.3?±?11.3 years). The quality of aneurysm occlusion was assessed independently and anonymously by a core laboratory.

Results

Using DSA (gold standard technique), total occlusion was depicted in 57 aneurysms (45.2%), neck remnant in 34 aneurysms (27.0%) and aneurysm remnant in 35 aneurysms (27.8%). Sensitivity, specificity, positive predictive value and negative predictive value were very similar with 3D-TOF and CE-MRA. Visibility of coils was much better with 3D-TOF (95.2%) than with CE-MRA (23.0%) (P?P?=?0.012).

Conclusions

In this large prospective series of patients with coiled aneurysms, at 3T 3D-TOF MRA was equivalent to CE-MRA for the evaluation of aneurysm occlusion, but coil visibility was superior at 3D-TOF. Thus the use of 3D-TOF at 3T is recommended for the follow-up of coiled intracranial aneurysms.

Key Points

? Different Magnetic Resonance (MR) imaging techniques are used to evaluate intracranial aneurysms. ? At 3T MR, 3D-TOF and CE-MRA appear equivalent for evaluating coiled aneurysms.. ? Coils are better visualised on 3D-TOF than on CE-MRA. ? Combined analysis of 3D-TOF and CE-MRA does not seem helpful. ? At 3T, 3D-TOF techniques are recommended for monitoring patients with coiled aneurysms.     

Triple-TWIST MRA: high spatial and temporal resolution MR angiography of the entire peripheral vascular system using a time-resolved 4D MRA technique

Objectives

Multi-station contrast-enhanced magnetic resonance angiography (MRA) is considered as the imaging investigation of first choice in patients suffering from peripheral arterial occlusive disease. In order to overcome venous overlay and to gain dynamic flow information as provided by digital subtraction angiography (DSA), we developed a triple injection protocol for high-resolution MRA of the entire peripheral vascular system, applying time-resolved (TR) four-dimensional (4D) MRA sequences.

Methods

Ten patients underwent three-station TR-MRA of the pelvis and lower extremities with DSA as reference standard. Both investigations were compared concerning stenosis on a segment-by-segment basis. Furthermore, 28 consecutive patients underwent the same MR-only imaging protocol. All images were evaluated concerning image quality (1 = non-diagnostic, 4 = excellent), venous overlay (from none up to substantial) and time to venous enhancement (very early/early/normal/late).

Results

Three-station TR-MRA proved feasible and was comparable with DSA in 282 vessel segments, with underestimation grade of stenosis in four segments and overestimation in four segments, respectively. In 32/38 patients no venous overlay was noted; in six patients there was mild venous overlay. Image quality was rated excellent or good in most cases.

Conclusions

TR-MRA provides morphological and functional information without any timing issues due to optimal arterial enhancement at high spatial resolution without venous overlay.

Key Points

? Contrast-enhanced MR angiography (MRA) has become widely accepted. ? Time-resolved (TR) MRA provides dynamic arterial flow information without venous overlay. ? TR-MRA and DSA show comparable results for assessment of stenosis. ? TR-MRA provides excellent-good image quality of the peripheral vascular system.     

Follow-up after embolization of ruptured intracranial aneurysms: A prospective comparison of two-dimensional digital subtraction angiography, three-dimensional digital subtraction angiography, and time-of-flight magnetic resonance angiography

Introduction

To prospectively compare of the diagnostic value of digital subtraction angiography (DSA) and time-of-flight magnetic resonance angiography (TOF-MRA) in the follow-up of intracranial aneurysms after endovascular treatment.

Methods

Seventy-two consecutive patients were examined 3?months after the embolization. The index tests included: two-dimensional DSA (2D-DSA), three-dimensional DSA (3D-DSA), and TOF-MRA. The reference test was a retrospective consensus between 2D-DSA images, 3D-DSA images, and source rotational DSA images. The evaluation included: detection of the residual flow, quantification of the flow, and validity of the decision regarding retreatment. Intraobserver agreement and interobserver agreement were determined.

Results

The sensitivity and specificity of residual flow detection ranged from 84.6?% (2D-DSA and TOF-MRA) to 92.3?% (3D-DSA) and from 91.3?% (TOF-MRA) to 97.8?% (3D-DSA), respectively. The accuracy of occlusion degree evaluation ranged from 0.78 (2D-DSA) to 0.92 (3D-DSA, Cohen??s kappa). The 2D-DSA method presented lower performance in the decision on retreatment than 3D-DSA (P?<?0.05, ROC analysis). The intraobserver agreement was very good for all techniques (???=?0.80?C0.97). The interobserver agreement was moderate for TOF-MRA and very good for 2D-DSA and 3D-DSA (???=?0.72?C0.94).

Conclusion

Considering the invasiveness of DSA and the minor difference in the diagnostic performance between 3D-DSA and TOF-MRA, the latter method should be the first-line modality for follow-up after aneurysm embolization.     

MRI of intracranial vertebral artery dissection: evaluation of intramural haematoma using a black blood, variable-flip-angle 3D turbo spin-echo sequence

Introduction

We investigated the efficacy of three-dimensional black blood T1-weighted imaging (3D-BB-T1WI) using a variable refocusing flip angle turbo spin-echo sequence in the diagnosis of intracranial vertebral artery dissection (VAD).

Methods

Sixteen consecutive patients diagnosed with intracranial VAD underwent magnetic resonance imaging that included 3D time-of-flight-MRA, axial spin-echo T1-weighted images (SE-T1WI) and oblique coronal 3D-BB-T1WI sequences. The visualization, morphology and extent of intramural haematomas were assessed and compared among the sequences. Results obtained by digital subtraction angiography (DSA), 3D-angiography and/or 3D-CT angiography (CTA) were used as standards of reference.

Results

3D-BB-T1WI revealed intramural haematomas in all cases, whereas SE-T1WI and magnetic resonance angiography (MRA) failed to reveal a haematoma in one case and three cases, respectively. The mean visualization grading score for the intramural haematoma was the highest for 3D-BB-T1WI, and there was a statistically significant difference among the sequences (p?<?0.001). At least a portion of the intramural haematoma was distinguishable from the lumen on 3D-BB-T1WI, whereas the haematomas were entirely indistinguishable from intraluminal signals on MRA in two cases (12.5 %) and on SE-T1WI in one case (6.3 %). 3D-BB-T1WI revealed the characteristic crescent shape of the intramural haematoma in 14 cases (87.5 %), whereas SE-T1WI and MRA revealed a crescent shape in only 7 cases (43.8 %) and 8 cases (50 %), respectively. In a consensus reading, 3D-BB-T1WI was considered the most consistent sequence in representing the extent and morphology of the lesion in 14 cases (87.5 %), compared to DSA and CTA.

Conclusion

3D-BB-T1WI is a promising method to evaluate intramural haematoma in patients with suspected intracranial VAD.     

Value of CT angiography for the detection of intracranial vascular lesions in patients with acute severe headache

Objectives

To retrospectively investigate the prevalence and characteristics of intracranial vascular lesions in patients with acute severe headache with the use of CT angiography (CTA).

Methods

We systematically searched for neurologically intact patients with acute severe headache and normal unenhanced head CT. The study group consisted of 512 patients; 251 male; mean age 46.2?±?12.4 years. All patients underwent CTA between 1 day and 2 months after the headache attack. CTA images were interpreted by two experienced neuroradiologists for the presence of vascular lesions.

Results

Thirty-four (6.6 %) of the 512 patients had intracranial vascular lesions on CTA, including 33 aneurysms (2 patients had 2 aneurysms each), 2 moyamoya disease and 1 arterial dissection. No gender- or age-related differences were found. Aneurysms arose most commonly on the internal carotid artery (n?=?12), followed by the anterior communicating artery (n?=?7), and the middle cerebral artery (n?=?7). Maximal diameters ranged from 2.0 to 13.1 mm (mean, 3.9?±?2.6 mm).

Conclusions

CTA is a feasible tool for diagnosing intracranial vascular lesions in patients with acute severe headache. The prevalence of vascular lesions in our series was 6.6 %, which is higher than that predicted in the general population.

Key Points

? Unruptured cerebral aneurysms may be a cause of acute severe headache ? CTA assesses intracranial vascular lesions in patients with acute severe headache ? The prevalence of vascular lesions in our series of patients was 6.6 %     

Angiographic CT with intravenous contrast agent application for monitoring of intracranial flow diverting stents

Introduction

Intracranial flow diverting devices are increasingly used to treat cerebral aneurysms. A reliable, non-invasive follow-up modality would be desirable. Our aim was to compare intra-arterial digital subtraction angiography (ia DSA) to angiographic computed tomography with intravenous contrast agent application (iv ACT) in the visualisation of flow diverting devices and aneurysm lumina.

Methods

Follow-up monitoring by iv ACT (n?=?36) and ia DSA (n?=?25) in 14 patients treated with flow diverting devices for intracranial aneurysms was evaluated retrospectively. Images were evaluated by two neuroradiologists in anonymous consensus reading regarding the device deployment, wall apposition, neck coverage of the aneurysm, opacification of the vessel and device lumen, as well as the degree of aneurysm occlusion.

Results

Corresponding ia DSA and iv ACT images were scored identically in all patients regarding the stent deployment, wall apposition and neck coverage, as well as the degree of aneurysm occlusion and patency status of the device and parent artery. Opacification of the parent vessel lumen and perfused parts of the aneurysm was considered slightly inferior for iv ACT in comparison with ia DSA (seven of 36 cases), without impact on diagnosis.

Conclusions

We demonstrated the feasibility and diagnostic value of iv ACT in follow-up imaging of intracranial flow diverting devices. Due to its high spatial resolution and non-invasive character, this novel technique might become a valuable imaging modality in these patients.     

Low tube voltage and low contrast material volume cerebral CT angiography

Objectives

To evaluate the image quality, radiation dose and diagnostic accuracy of low kVp and low contrast material volume cerebral CT angiography (CTA) in intracranial aneurysm detection.

Methods

One hundred twenty patients were randomly divided into three groups (n?=?40 for each): Group A, 70 ml iodinated contrast agent/120 kVp; group B, 30 ml/100 kVp; group C, 30 ml/80 kVp. The CT numbers, noise, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured in the internal carotid artery (ICA) and middle cerebral artery (MCA). Subjective image quality was evaluated. For patients undergoing DSA, diagnostic accuracy of CTA was calculated with DSA as reference standard and compared.

Results

CT numbers of ICA and MCA were higher in groups B and C than in group A (P?<?0.01). SNR and CNR in groups A and B were higher than in group C (both P?<?0.05). There was no difference in subjective image quality among the three groups (P?=?0.939). Diagnostic accuracy for aneurysm detection among these groups had no statistical difference (P?=?1.00). Compared with group A, the radiation dose of groups B and C was decreased by 45 % and 74 %.

Conclusion

Cerebral CTA at 100 or 80 kVp using 30 ml contrast agent can obtain diagnostic image quality with a low radiation dose while maintaining the same diagnostic accuracy for aneurysm detection.

Key Points

? Cerebral CTA is feasible using 100/80 kVp and 30 ml contrast agent. ? This approach obtains diagnostic image quality with 45–74 % radiation dose reduction. ? Diagnostic accuracy for intracranial aneurysm detection seems not to be compromised.     

The combination of baseline magnetic resonance perfusion-weighted imaging-derived tissue volume with severely prolonged arterial-tissue delay and diffusion-weighted imaging lesion volume is predictive of MCA-M1 recanalization in patients treated with endovascular thrombectomy

Introduction

Indices of collateral flow deficit derived from MR perfusion imaging that are predictive of MCA-M1 recanalization after intravenous thrombolysis have been recently reported. Our objective was to test the performance of such MRI-derived collateral flow indices for prediction of recanalization after endovascular thrombectomy.

Methods

Fifty-seven patients with MCA-M1 occlusion evaluated with multimodal MRI prior to thrombectomy were included. Bayesian processing allowed quantification of collateral perfusion indices like the volume of tissue with severely prolonged arterial-tissue delay (>6 s) (VolATD6). Baseline DWI lesion volume was also measured. Correlations with angiographic collateral flow grading and post-thrombectomy recanalization were assessed.

Results

VolATD6?<?27 ml or DWI lesion volume <15 ml provide the most accurate diagnosis of excellent collateral supply (p?<?0.0001). The combination of VolATD6?>?27 ml and DWI lesion volume >15 ml significantly discriminates recanalizers versus nonrecanalizers (whole cohort, p?=?0.032; MERCI cohort (n?=?50), p?=?0.024). When both criteria are positive, 76.2 % of the patients treated with the MERCI retriever do not fully recanalize (p?=?0.024). In multivariate analysis, the aforementioned combined criterion and the angiographic collateral grade are the only independent predictors of recanalization with the MERCI retriever (p?=?0.015 and 0.029, respectively).

Conclusion

Bayesian arterial-tissue delay maps and DWI maps provide a non-invasive assessment of the degree of collateral flow and a combined index that is predictive of MCA-M1 recanalization after endovascular thrombectomy. Further studies are needed to evaluate the accuracy of this index in patients treated with novel stent retriever devices.     

Thrombus imaging in acute stroke: correlation of thrombus length on susceptibility-weighted imaging with endovascular reperfusion success

Objectives

Susceptibility-weighted imaging (SWI) enables visualization of thrombotic material in acute ischemic stroke. We aimed to validate the accuracy of thrombus depiction on SWI compared to time-of-flight MRA (TOF-MRA), first-pass gadolinium-enhanced MRA (GE-MRA) and digital subtraction angiography (DSA). Furthermore, we analysed the impact of thrombus length on reperfusion success with endovascular therapy.

Methods

Consecutive patients with acute ischemic stroke due to middle cerebral artery (MCA) occlusions undergoing endovascular recanalization were screened. Only patients with a pretreatment SWI were included. Thrombus visibility and location on SWI were compared to those on TOF-MRA, GE-MRA and DSA. The association between thrombus length on SWI and reperfusion success was studied.

Results

Eighty-four of the 88 patients included (95.5 %) showed an MCA thrombus on SWI. Strong correlations between thrombus location on SWI and that on TOF-MRA (Pearson’s correlation coefficient 0.918, P?<?0.001), GE-MRA (0.887, P?<?0.001) and DSA (0.841, P?<?0.001) were observed. Successful reperfusion was not significantly related to thrombus length on SWI (P?=?0.153; binary logistic regression).

Conclusions

In MCA occlusion thrombus location as seen on SWI correlates well with angiographic findings. In contrast to intravenous thrombolysis, thrombus length appears to have no impact on reperfusion success of endovascular therapy.

Key Points

? SWI helps in assessing location and length of thrombi in the MCA ? SWI, MRA and DSA are equivalent in detecting the MCA occlusion site ? SWI is superior in identifying the distal end of the thrombus ? Stent retrievers should be deployed over the distal thrombus end ? Thrombus length did not affect success of endovascular reperfusion guided by SWI     

Magnetic resonance 4D flow analysis of cerebrospinal fluid dynamics in Chiari I malformation with and without syringomyelia

Objective

To analyse cerebrospinal fluid (CSF) hydrodynamics in patients with Chiari type I malformation (CM) with and without syringomyelia using 4D magnetic resonance (MR) phase contrast (PC) flow imaging.

Methods

4D-PC CSF flow data were acquired in 20 patients with CM (12 patients with presyrinx/syrinx). Characteristic 4D-CSF flow patterns were identified. Quantitative CSF flow parameters were assessed at the craniocervical junction and the cervical spinal canal and compared with healthy volunteers and between patients with and without syringomyelia.

Results

Compared with healthy volunteers, 17 CM patients showed flow abnormalities at the craniocervical junction in the form of heterogeneous flow (n?=?3), anterolateral flow jets (n?=?14) and flow vortex formation (n?=?5), most prevalent in patients with syringomyelia. Peak flow velocities at the craniocervical junction were significantly increased in patients (?15.5?±?11.3 vs. ?4.7?±?0.7 ?cm/s in healthy volunteers, P?P?Conclusions 4D-PC flow imaging allowed comprehensive analysis of CSF flow in patients with Chiari I malformation. Alterations of CSF hydrodynamics were most pronounced in patients with syringomyelia.

Key Points

? Analysis of CSF flow is important in patients with Chiari I malformation ? 4D-PC MRI allows analysis of CSF in patients with Chiari I. ? Chiari I patients show characteristic qualitative and quantitative alterations of CSF flow. ? Alterations of CSF hydrodynamics are most pronounced in patients with associated syringomyelia.     

Susceptibility-weighted angiography for the detection of high-flow intracranial vascular lesions: preliminary study

Objectives

Susceptibility-weighted magnetic resonance imaging (MRI) sequences may demonstrate various signal intensities of draining veins in cases of high-flow vascular malformation (HFVM), including arteriovenous malformation (AVM) and dural arteriovenous fistula (dAVF). Our objective was to evaluate susceptibility-weighted angiography (SWAN) for the detection of HFVM.

Methods

Fifty-eight consecutive patients with a suspected intracranial vascular malformation were explored with SWAN and post-contrast MRI sequences at 3 T. The diagnosis of slow-flow vascular malformation (SFVM), including developmental venous anomaly (DVA) or brain capillary telangiectasia (BCT), was based on MRI. Patients with suspected HFVM underwent digital subtraction angiography (DSA). SWAN images were analysed by three blinded readers according to a three-point scale of the venous signal.

Results

Thirty-one patients presented 35 SFVM (26 DVA and 9 BCT) that systematically appeared hypointense on SWAN images. In patients with atypical MRI findings, DSA revealed one patient with an atypical DVA and 26 patients with HFVM (22 AVM and 4 dAVF). SWAN revealed at least one venous hyperintensity in all patients with HFVM. Agreement between readers was excellent.

Conclusions

SWAN appears reliable for characterising blood flow dynamics in brain veins. In clinical practice, SWAN can routinely rule out HFVM in patients with atypical brain veins.

Key Points

? Susceptibility-weighted angiography (SWAN) offers new perspectives for detecting intracranial vascular malformations. ? SWAN sequence provides non-invasive characterisation of blood flow dynamics. ? SWAN can differentiate between high and slow flowing venous blood. ? SWAN can routinely rule out high-flow vascular malformations.     

Fusion imaging using subtracted and unsubtracted rotational angiography for pretherapeutic evaluation of dural arteriovenous fistulas

Purpose

We describe the clinical utility of an imaging technique that combines 3D subtracted and unsubtracted rotational angiography for evaluation of the angioarchitecture of dural arteriovenous fistulas (DAVFs).

Methods

From May 2010 to June 2013, 21 consecutive patients with intracranial DAVFs (22 lesions) underwent 3D angiography for pretherapeutic evaluation. 3D fusion angiography (3DFA) images were semiautomatically obtained from a dataset of unsubtracted and subtracted rotational angiographs. Multiplanar reformatted images and partial MIP images from unsubtracted rotational angiography and fusion images were evaluated by two radiologists, with particular focus on visualization of feeding arteries, shunted pouches, and drainage veins of DAVFs by use of a 3-point scale. The referring neuroradiologists were asked whether the information provided by 3DFA was helpful for treatment decisions.

Results

For 21 of 22 lesions, all evaluated items were well depicted on the 3DFA. The visualization rating score for feeding arteries and shunted pouches on 3DFA were significantly higher than those of 3D digital angiography (p < 0.05). There were no statistically significant differences between visualization of drainage veins. The information provided by the fusion images was helpful for treatment decisions in all cases.

Conclusion

3DFA images are useful for evaluation of the angioarchitecture of intracranial DAVFs.     

Clinical outcomes after magnetic resonance angiography (MRA) versus computed tomographic angiography (CTA) for pulmonary embolism evaluation

Purpose

To compare patient outcomes following magnetic resonance angiography (MRA) versus computed tomographic angiography (CTA) ordered for suspected pulmonary embolism (PE).

Methods

In this IRB-approved, single-center, retrospective, case-control study, we reviewed the medical records of all patients evaluated for PE with MRA during a 5-year period along with age- and sex-matched controls evaluated with CTA. Only the first instance of PE evaluation during the study period was included. After application of our exclusion criteria to both study arms, the analysis included 1173 subjects. The primary endpoint was major adverse PE-related event (MAPE), which we defined as major bleeding, venous thromboembolism, or death during the 6 months following the index imaging test (MRA or CTA), obtained through medical record review. Logistic regression, chi-square test for independence, and Fisher’s exact test were used with a p?<?0.05 threshold.

Results

The overall 6-month MAPE rate following MRA (5.4%) was lower than following CTA (13.6%, p?<?0.01). Amongst outpatients, the MAPE rate was lower for MRA (3.7%) than for CTA (8.0%, p?=?0.01). Accounting for age, sex, referral source, BMI, and Wells’ score, patients were less likely to suffer MAPE than those who underwent CTA, with an odds ratio of 0.44 [0.24, 0.80]. Technical success rate did not differ significantly between MRA (92.6%) and CTA (90.5%) groups (p?=?0.41).

Conclusion

Within the inherent limitations of a retrospective case-controlled analysis, we observed that the rate of MAPE was lower (more favorable) for patients following pulmonary MRA for the primary evaluation of suspected PE than following CTA.

     

Diagnostic accuracy of colour Doppler ultrasonography, CT angiography and blood-pool-enhanced MR angiography in assessing carotid stenosis: a comparative study with DSA in 170 patients

Purpose

This study was undertaken to prospectively evaluate the diagnostic performance of colour Doppler ultrasonography (CDUS), first-pass (FP) and steady-state (SS) contrast-enhanced magnetic resonance angiography (MRA) and computed tomography angiography (CTA) of the carotid arteries using digital subtraction angiography (DSA) as the reference standard.

Materials and methods

A total of 170 patients with previous cerebrovascular events and suspected carotid artery stenoses underwent CDUS, blood-pool MRA, CTA and DSA. Accuracy, sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated for CDUS, FP MRA, SS MRA and CTA. The McNemar and Wilcoxon tests and receiver operating characteristic (ROC) curve analysis were used to determine significant differences (p<0.05) between the diagnostic performances of the four modalities, and the degree of stenosis was compared using linear regression.

Results

A total of 336 carotid bifurcations were studied. The area under the curve (AUC) for degree of stenosis was: CDUS 0.85±0.02, FP MRA 0.982±0.005, SS MRA 0.994±0.002 and CTA 0.997±0.001. AUC analysis showed no statistically significant difference between CTA and MRA (p=0.0174) and a statistically significant difference between CDUS and the other techniques (p<0.001). Plaque morphology analysis showed no significant difference between CTA and SS MRA; a significant difference was seen between CTA and SS MRA versus FP MRA (p=0.04) and CDUS (p=0.038). Plaque ulceration analysis showed a statistically significant difference between MRA and CTA (0.04< p<0.046) versus CDUS (p=0.019).

Conclusions

CTA is the most accurate technique for evaluating carotid stenoses, with a slightly better performance than MRA (97% vs. 95% for SS MRA and 92% for FP MRA) and a greater accuracy than CDUS (97% vs. 76%). Blood-pool contrast-enhanced SS sequences offer improved evaluation of degree of stenosis and plaque morphology with accuracy substantially identical to CTA.     

Contrast-enhanced time-resolved 4D MRA of congenital heart and vessel anomalies: image quality and diagnostic value compared with 3D MRA

Objectives

To evaluate time-resolved interleaved stochastic trajectories (TWIST) contrast-enhanced 4D magnetic resonance angiography (MRA) and compare it with 3D FLASH MRA in patients with congenital heart and vessel anomalies.

Methods

Twenty-six patients with congenital heart and vessel anomalies underwent contrast-enhanced MRA with both 3D FLASH and 4D TWIST MRA. Images were subjectively evaluated regarding total image quality, artefacts, diagnostic value and added diagnostic value of 4D dynamic imaging. Quantitative comparison included signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and vessel sharpness measurements.

Results

Three-dimensional FLASH MRA was judged to be significantly better in terms of image quality (4.0?±?0.6 vs 3.4?±?0.6, P?<?0.05) and artefacts (3.8?±?0.4 vs 3.3?±?0.5, P?<?0.05); no difference in diagnostic value was found (4.2?±?0.4 vs 4.0?±?0.4); important additional functional information was found in 21/26 patients. SNR and CNR were higher in the pulmonary trunk in 4D TWIST, but slightly higher in the systemic arteries in 3D FLASH. No difference in vessel sharpness delineation was found.

Conclusions

Although image quality was inferior compared with 3D FLASH MRA, 4D TWIST MRA yields robust images and added diagnostic value through dynamic acquisition was found. Thus, 4D TWIST MRA is an attractive alternative to 3D FLASH MRA.

Key Points

? New magnetic resonance angiography (MRA) techniques are increasingly introduced for congenital cardiovascular problems. ? Time-resolved angiography with interleaved stochastic trajectories (TWIST) is an example. ? Four-dimensional TWIST MRA provided inferior image quality compared to 3D FLASH MRA but without significant difference in vessel sharpness. ? Four-dimensional TWIST MRA gave added diagnostic value.     

Time-resolved assessment of collateral flow using 4D CT angiography in large-vessel occlusion stroke

Objectives

In acute stroke patients with large vessel occlusion, collateral blood flow affects tissue fate and patient outcome. The visibility of collaterals on computed tomography angiography (CTA) strongly depends on the acquisition phase, but the optimal time point for collateral imaging is unknown.

Methods

We analysed collaterals in a time-resolved fashion using four-dimensional (4D) CTA in 82 endovascularly treated stroke patients, aiming to determine which acquisition phase best depicts collaterals and predicts outcome. Early, peak and late phases as well as temporally fused maximum intensity projections (tMIP) were graded using a semiquantitative regional leptomeningeal collateral score, compared with conventional single-phase CTA and correlated with functional outcome.

Results

The total extent of collateral flow was best visualised on tMIP. Collateral scores were significantly lower on early and peak phase as well as on single-phase CTA. Collateral grade was associated with favourable functional outcome and the strength of this relationship increased from earlier to later phases, with collaterals on tMIP showing the strongest correlation with outcome.

Conclusions

Temporally fused tMIP images provide the best depiction of collateral flow. Our findings suggest that the total extent of collateral flow, rather than the velocity of collateral filling, best predicts clinical outcome.

Key Points

? Collateral flow visibility on CTA strongly depends on the acquisition phase ? tMIP offers the best visualisation of the extent of collaterals ? Outcome prediction may be better with tMIP than with earlier phases ? Total extent of collaterals seems more important than their filling speed ? If triggered too early, CTA may underestimate collateral flow     

Angiographic and artefact-free computed tomography imaging of experimental aneurysms embolised with hydrogel filaments

Objectives

We compared experimental rabbit carotid bifurcation aneurysms embolised with platinum coils or hydrogel filaments by using digital subtraction angiography (DSA) and computed tomography angiography (CTA).

Methods

Embolisation was performed using platinum coils (n?=?2), hydrogel filaments loaded with iodine (n?=?3) and hydrogel filaments loaded with barium sulphate (n?=?3). In one case, a stent was deployed in the parent vessel to determine the effect of hydrogel filaments on stent visualisation. DSA evaluations occurred immediately post-treatment. CTA evaluations occurred at 0–13 weeks post-treatment. The DSA and CTA images were evaluated for the lack of artefacts and the visibilities of the embolic mass, individual coils and residual flow in the aneurysm sac and neck.

Results

The DSA results were largely concordant among the three groups. The embolic masses were readily evident with some individual coils being distinguished. In the aneurysms embolised with hydrogel filaments, visualisation of the individual coils, residual flow and stent with minor or no artefacts was possible using CTA. On the other hand, the beam hardening artefacts precluded analysis of aneurysms embolised with platinum coils.

Conclusion

CTA-compatible embolic devices could have wide applications in diverse locations throughout the vasculature, particularly in combination with stents or stent grafts.     

Subtractionless first-pass single contrast medium dose peripheral MR angiography using two-point Dixon fat suppression

Objective

To investigate the feasibility of subtractionless first-pass single contrast medium dose (0.1 mmol/kg) peripheral magnetic resonance angiography (MRA) at 1.5 T using two-point Dixon fat suppression and compare it with conventional subtraction MRA in terms of image quality.

Methods

Twenty-eight patients (13 male, 15 female; mean age ± standard deviation, 66?±?16 years) with known or suspected peripheral arterial disease underwent subtractionless and subtraction first-pass MRA at 1.5 T using two-point Dixon fat suppression. Results were compared with regard to vessel-to-background contrast. A phantom study was performed to assess the signal-to-noise ratio (SNR) of both MRA techniques. Two experienced observers scored subjective image quality. Agreement regarding subjective image quality was expressed in quadratic weighted κ values.

Results

Vessel-to-background contrast improved in all anatomical locations with the subtractionless method versus the subtraction method (all P?<?0.001). Subjective image quality was uniformly higher with the subtractionless method (all P?<?0.03, except for the aorto-iliac arteries for observer 1, P?=?0.052). SNR was 15 % higher with the subtractionless method (31.9 vs 27.6).

Conclusion

This study demonstrates the feasibility of subtractionless first-pass single contrast medium dose lower extremity MRA. Moreover, both objective and subjective image quality are better than with subtraction MRA.

Key Points

? MRA is increasingly used for vascular applications. ? Dixon imaging offers an alternative to image subtraction for fat suppression. ? Subtractionless first-pass peripheral MRA is possible using two-point Dixon fat suppression. ? Subtractionless peripheral MRA is possible at 1.5 T a single contrast medium dose. ? Subtractionless first-pass peripheral MRA provides good image quality with few non-diagnostic studies.