Detection of residual brain arteriovenous malformations after radiosurgery: diagnostic accuracy of contrast-enhanced four-dimensional MR angiography at 3.0 T

Value of contrast-enhanced MR angiography for the follow-up of treated brain arteriovenous malformations: systematic review and meta-analysis

OBJECTIVE

To estimate the diagnostic value of contrast-enhanced MR angiography (CE-MRA) in identifying residual brain arteriovenous malformations (AVMs) after treatment.

METHODS

We retrieved appropriate references from the electronic databases of PubMed, Web of Science, Embase, and Cochrane Library, and then evaluated the methodology quality of included references using the QUADAS-2 tool. We calculated the pooled sensitivity and specificity by applying a bivariate mixed-effects model and detected the publication bias using Deeks' funnel plot. The values of I2 were used to test heterogeneity and meta-regression analyses were performed to search for the causes of heterogeneity.

RESULTS

We included 7 eligible studies containing 223 participants. Compared with a gold standard, the overall sensitivity and specificity of CE-MRA in detecting residual brain AVMs were 0.77 (95% CI 0.65-0.86) and 0.97 (95% CI 0.82-1.00), respectively. Based on the summary ROC curve, the AUC was 0.89 (95% CI 0.86-0.92). Heterogeneity could be observed in our study, especially for the specificity (I2 = 74.23%). Furthermore, there was no evidence of publication bias.

CONCLUSIONS

Our study provides evidence that CE-MRA has good diagnostic value and specificity for the follow-up of treated brain AVMs. Nevertheless, considering the small sample size, heterogeneity, and many factors that may affect the diagnostic accuracy, future large-sample, prospective studies are necessary to validate the results.

KEY POINTS

• The pooled sensitivity and specificity of contrast-enhanced MR angiography (CE-MRA) in detecting residual arteriovenous malformations (AVMs) were 0.77 (95% CI 0.65-0.86) and 0.97 (95% CI 0.82-1.00). • The four-dimensional CE-MRA showed less sensitivity than the three-dimensional CE-MRA for treated AVMs. • CE-MRA is helpful to identify residual AVMs and reduce excessive DSA during follow-up.

Intracranial arteriovenous malformations

The treatment of arteriovenous malformations (AVMs) has evolved over the last 10 years. It is now possible to see that obliteration continues for up to 10 years and that the final obliteration rate may be between 85% and 90%. Improved imaging has made the treatment more efficient and has reduced the complications. It is possible to treat larger AVMs in a single session than was previously thought possible without increases in the complication rates. In addition, treatments of larger lesions can be staged. The use of 3D rotating angiography produces remarkable images which can be imported into GammaPlan. On the other hand efforts are ongoing to avoid the need for digital subtraction angiography, which would make the treatment a lot more comfortable.

Are Dynamic Arterial Spin-Labeling MRA and Time-Resolved Contrast-Enhanced MRA Suited for Confirmation of Obliteration following Gamma Knife Radiosurgery of Brain Arteriovenous Malformations?

BACKGROUND AND PURPOSE

Intra-arterial DSA has been traditionally used for confirmation of cure following gamma knife radiosurgery for AVMs. Our aim was to evaluate whether 4D arterial spin-labeling MRA and contrast-enhanced time-resolved MRA in combination can be an alternative to DSA for confirmation of AVM obliteration following gamma knife radiosurgery.

MATERIALS AND METHODS

In this prospective study, 30 patients undergoing DSA for confirmation of obliteration following gamma knife radiosurgery for AVMs (criterion standard) also underwent MRA, including arterial spin-labeling MRA and contrast-enhanced time-resolved MRA. One dataset was technically unsatisfactory, and the case was excluded. The DSA and MRA datasets of 29 patients were independently and blindly evaluated by 2 observers regarding the presence/absence of residual AVMs.

RESULTS

The mean time between gamma knife radiosurgery and follow-up DSA/MRA was 53 months (95% CI, 42-64 months; range, 22-168 months). MRA total scanning time was 9 minutes and 17 seconds. Residual AVMs were detected on DSA in 9 subjects (obliteration rate = 69%). All residual AVMs were detected on at least 1 MRA sequence. Arterial spin-labeling MRA and contrast-enhanced time-resolved MRA showed excellent specificity and positive predictive values individually (100%). However, their sensitivity and negative predictive values were suboptimal due to 1 false-negative with arterial spin-labeling MRA and 2 with contrast-enhanced time-resolved MRA (sensitivity = 88% and 77%, negative predictive values = 95% and 90%, respectively). Both sensitivity and negative predictive values increased to 100% if a composite assessment of both MRA sequences was performed. Diagnostic accuracy (receiver operating characteristic) and agreement (κ) are maximized using arterial spin-labeling MRA and contrast-enhanced time-resolved MRA in combination (area under receiver operating characteristic curve = 1, P < .001; κ = 1, P < .001, respectively).

CONCLUSIONS

Combining arterial spin-labeling MRA with contrast-enhanced time-resolved MRA holds promise as an alternative to DSA for confirmation of obliteration following gamma knife radiosurgery for brain AVMs, having provided 100% sensitivity and specificity in the study. Their combined use also enables reliable characterization of residual lesions.

Magnetic Resonance Perfusion Changes of Arteriovenous Malformations Treated with Stereotactic Radiosurgery

BACKGROUND

The latency period from stereotactic radiosurgery (SRS) to obliteration of arteriovenous malformations (AVM) requires continuous imaging surveillance. Magnetic resonance (MR) perfusion is promising for noninvasive monitoring of AVMs after SRS. We studied longitudinal MR perfusion changes of brain AVMs treated with SRS.

METHODS

Consecutive patients treated for brain AVMs using SRS who had MR perfusion imaging studies performed before and at least once after SRS were studied. We estimated ipsilateral/contralateral brain hemisphere ratios of MR perfusion indexes, including regional cerebral blood flow (rCBF) and relative cerebral blood volume (rCBV), in the AVM nidus, perinidal region, and remote anterior and posterior brain regions.

RESULTS

Eleven patients (6 women; median age, 21 years) underwent SRS (median prescription dose, 18 Gy; range, 12-20 Gy) for brain AVMs (median Spetzler-Martin grade 2 and median volume 4.6 mL). Before the SRS, rCBV and rCBF ratios were significantly higher in the AVM nidus compared with other investigated brain regions (P < 0.001). Median time from SRS to the first and last post-SRS MR perfusion studies was 8 and 35 months, respectively. There was a statically significant decrease of rCBV (P = 0.043) and rCBF (P = 0.036) ratios in the AVM nidus, but not other brain regions, during post-SRS follow-up.

CONCLUSIONS

There is a gradual decrease of rCBV and rCBF in the AVM nidus after SRS. MR perfusion imaging is promising for monitoring of hemodynamic changes of AVMs after SRS. Larger studies investigating clinical value of MR perfusion imaging for AVMs after SRS are warranted.

Susceptibility-Weighted Angiography for the Follow-Up of Brain Arteriovenous Malformations Treated with Stereotactic Radiosurgery

The criterion standard for assessing brain AVM obliteration postradiosurgery is DSA. To explore the value of susceptibility-weighted angiography, we followed 26 patients with brain AVMs treated by radiosurgery using susceptibility-weighted angiography and DSA. Studies were evaluated by 2 independent readers for residual nidi. Susceptibility-weighted angiography demonstrated good intermodality (κ = 0.71) and interobserver (κ = 0.64) agreement, and good sensitivity (85.7%) and specificity (85.7%). Susceptibility-weighted angiography is a useful radiation- and contrast material-free technique to follow-up brain AVM obliteration postradiosurgery.

Conventional digital subtractional vs non-invasive MR angiography in the assessment of brain arteriovenous malformation

OBJECTIVES

Digital subtractional angiography (DSA) is the standard method for diagnosis, assessment and management of arteriovenous malformation in the brain. Conventional DSA (cDSA) is an invasive imaging modality that is often indicated before interventional treatments (embolization, open surgery, gamma knife). Here, we aimed to compare this technique with a non-invasive MR angiography (MRI DSA) for brain arteriovenous malformation (bAVM).

PATIENTS AND METHODS

Fourteen patients with ruptured brain AVM underwent embolization treatment pre-operation. Imaging was performed for all patients using MRI (1.5 T). After injecting contrast Gadolinium, dynamic MRI was performed with 40 phases, each phase of a duration of 1.2 s and having 70 images. The MRI results were independently assessed by experienced radiologist blinded to the cDSA.

RESULTS

The AVM nidus was depicted in all patients using cDSA and MRI DSA; there was an excellent correlation between these techniques in terms of the maximum diameter and Spetzler Martin grading. Of the fourteen patients, the drainage vein was depicted in 13 by both cDSA and MRI DSA showing excellent correlation between the techniques used.

CONCLUSION

MRI DSA is a non-invasive imaging modality that can give the images in dynamic view. It can be considered as an adjunctive method with cDSA to plan the strategy treatment for bAVM.

Value of 4D MR angiography at 3T compared with DSA for the follow-up of treated brain arteriovenous malformation

BACKGROUND AND PURPOSE

Four-dimensional, contrast-enhanced MRA is a useful technique for the diagnosis and classification of brain AVM. The purpose of this study was to evaluate its usefulness in the follow-up of treated brain AVM.

MATERIALS AND METHODS

Patients with treated brain AVM (embolization, radiosurgery, and/or surgery) were investigated with both DSA (the "gold standard") and 4D MRA. Four-dimensional MRA was performed at 3T using a 4D sequence, combining contrast-enhanced timing-robust angiography, keyhole, and sensitivity encoding techniques. Examinations were evaluated by 2 independent readers and disagreements were resolved by a third reader. Interobserver and intermodality agreement with respect to residual nidus, residual venous drainage, and brain AVM patency were determined.

RESULTS

Between May 2008 and February 2013, 37 patients with a median age of 45 years (interquartile range = 26-55) were prospectively included. Examinations were acquired 36 months (IQR = 10-45.5) after the last treatment. Interobserver agreement for brain AVM patency was very good for both 4D MRA (κ 0.82, 95% CI .67-.98) and DSA (κ 0.84, 95% CI .69-.98). After consensus reading, intermodality agreement for the evaluation of brain AVM patency was good (κ 0.73, 95% CI .55-.90). Diagnostic accuracy of 4D MRA for residual brain AVM compared with DSA, reached a sensitivity of 73.7%, specificity 100%, positive predictive value 100%, and negative predictive value 78.3%. Agreements by technique of treatment are also detailed.

CONCLUSIONS

Four-dimensional MRA is a useful radiation-free technique for the follow-up of patients with treated brain AVM, especially patients treated by radiosurgery. However, given its actual limitations it is not sufficient to assert the cure; DSA remains mandatory for this purpose.