3D DCE-MRA in spinal vascular malformations


 Purpose: This study was carried out to investigate whether 3.0T dynamic enhanced 3 dimensional magnetic resonance angiography (3D DCE-MRA) could identify spinal cord vascular malformations efficiently.Material and Methods: 32 suspected cases of spinal vascular disease with MR imaging and clinical symptoms were detected using DCE-MRA. 28 patients were valued through DSA for 3-5 days, and surgical treatment was performed on 24 patients. Results: DCE-MRA was used to examine all the cases which recognized abnormal vascular lesions clearly, and 28 cases were consistent with DSA or surgical diagnosis. The arterial blood supply was evaluated accurately in 28 cases. The findings were correct in 26 cases.Conclusion: 3.0T DCE-MRA features high sensitivity and accuracy in detecting and characterizing SVMs, especially SDAVF.


Introduction
Spinal vascular malformations (SVMs) occur rarely in clinic, but myeloradiculopathy as their clinical manifestation is usually progressive which results in devastating outcomes when untreated. It can be the best way to observe them using magnetic resonance imaging [1,2],but routine MRI can't detected the location of feeding arteries and stulas. In the past, con rmed diagnosis was dependent on digital subtraction angiography (DSA) of spinal cord [3]. However, DSA is invasive, time-consuming and complicated with many complications. Spinal dynamic contrast enhanced MRA (DCE-MRA) is safe and can avoid many complications caused by DSA [4,5]. Spinal DCE-MRA at 3.0T provides higher spatial and temporal resolutions, which greatly helps to diagnostic SVMs [6-8]. As lesions of SVMs often occur in the long axis of spine, DCE-MRA at 3.0T offers a greater eld of view (FOV) than 1.5T MR for detecting and characterizing SVMs. In order to evaluate diagnostic e cacy of 3.0T DCE-MRA in SVMs, we have examined more patients using DCE-MRA with DSA or surgery comparing with previous research [7]. Gadodiamide (0.5mmol/ml) was injected through the cubital vein with a high-pressure syringe of 20ml at a speed of 3ml/s. Cycle time was recorded through test-bolus technique before detection, and then the 3D rf-fast gradient-echo volume was used at TE/TR,1.3ms/3.6ms. Turning Angle of 20°, matrix size = 448×384, FOV = 35cm, thickness = 0.6mm, bandwidth (BW) = 25Hz were taken as parameters to achieve the acquisition. The initial images were collected on the sagittal plane, while the contrast agent was injected during the scanning period. The scanning time is about 3 minutes.

Materials And Methods
The images were uploaded to ADW 4.6 workstation. Volume rendering (VR), curved reconstruction (CPR) and thin maximum strength projection (MIP) reconstruction techniques were applied.
2.2.2 DSA was performed according to the conventional method. MRA imaging demonstrated major feeding arteries.

2.2.3
The images were analyzed together by two neuroradiologists with 30 and 10 years of experience in neuroimaging. The results were compared with DSA or surgical results including the type of disease, the extent of the lesion, the blood supply, and the stula of vascular malformations.

Results
Conventional contrast-enhanced MRI was performed on all cases. Perimedullary curved vessels or vascular ball signals were observed by MRI on t2weighted images. Flexural or bulbar enhancement is demonstrated after enhancement. The results showed that the studies of the three neuroradiologists were consistent (Table 1). 18 cases of SDAVF were diagnosed according to DCE-MRA, among which, except 2 cases (DSA negative) and 3 cases (DCA-MRA negative), 16 cases were consistent with DSA or surgical diagnosis. 11 cases were PMAVF, among which 9 cases were consistent with DSA diagnosis, and 1 case was in accord with the operation. The three cases were AVM, and the DSA diagnosis results were the same. In 12 of the 235 patients, arteriovenous abnormalities were found in DCA-MRA, but no supply arteries or stulas were found.

Feeding Artery:
SDAVF corresponded with DCA-MRA and DSA in 16 of the 18 cases. The diagnosis of PMAVF was the same in 9 of the 11 cases. Three cases were diagnosed as bilateral vertebral artery by arteriography, DSA and DCA-MRA.

Fistula Location
Results showed DCA-MRA accurately predicted stula condition in 16 of 18 cases of SDAVF. Fistula was found in DCA-MRA 11 cases of PMAVF, but 4 cases were inconsistent with DSA.

Discussion
The diagnosis of SVMs was made on the basis of an enlarged and tortuous perimedullary vein together with abnormal arteriovenous communication in the spinal canal [7,9,10]. For the former, we can use conventional T2 MR imaging for detection, while for the latter, we need angiography (MRA, CTA or DSA) to diagnose. In order to facilitate clinical diagnosis and treatment for SVMs, lesion type was based on the locations of the stulas such as spinal dural arteriovenous stulas (SDAVF) (Fig. 1), spinal cord perimedullary arteriovenous stula (PMAVF) (Fig. 2) and spinal cord arteriovenous malformations (SCAVM). AVF of spinal cord is the most common spinal vascular malformation [11]. In this study, it accounted for 94.1%. SDAVF commonly involve the thoracolumbar spine, and shunt lesions located along a nerve root sleeve within a neural foramen and venous congestion of the spinal cord[12] [13] .The shunt of PMAVF is located in the epidural space and drains into epidural veins [14]. Microsurgery and transarterial embolization are the mainstays of treatment for SVMs, but the associated success rates depend upon the disease type and blood ow status [15]. Stereotactic radiosurgery and fractionated radiotherapy may have the relative safety and effectiveness which can bring signi cant promise for rare and complex lesions, but the optimal treatment parameters are required [16]. So it is very important to nd feeding arteries and stulas accurately.
DSA is the diagnostic gold standard for SVMs. It can accurately dynastic observe stula, feeding arteries and draining vein, but it is invasive, high radiation doses, large volumes of iodinated contrast material, complex high technical requirement, and may occur paraplegia and other serious DSA examination demands high technology. In case 2 and 15, DCA-MRA showed feeding artery and stula clearly, while DSA was negative. The reason may be that the pressure of the blood supply artery and the drainage vein resist each other, so that the iodine contrast agent cannot reach the drainage vein of the stula [22]. Although DSA is the gold standard, but sometime the results were not entirely reliable. Due to iodine contrast agent allergy(Case 12),some patients only underwent DCA-MRA to nd the feeding arteries and stulas before surgery. The diagnosis of DCA-MRA was proved to be correct after operation and follow-up. Case 16 DCA-MRA mistake to predict the localize of stula. The possible reason maybe the dilated feeding artery has bigger turning angle on the level of T12, leading to the discontinuous DCA-MRA appearance.
It is often di cult to locate the stula of PMAVF, in our research 4 cases did not inconsistent with DSA. Based on the characteristics of angioarchitecture, PMAVF is the direct communication between root pulp artery and perimedullary vein, the diameter is relatively smaller. For example, the feeding artery of case 1can be clearly determined, but the stula needs to be carefully searched. According to the analysis of multiple cases and the comparison of surgical results, gadolinium contrast agent concentration is generally considered to be the location of the stula (Fig. 2). The reason may be the pressure difference between the supplying artery and the draining vein on both sides of the stula. In case 6 Fig. 1 ,DCA-MRA results was consistent with DSA and surgery, the patient's clinical symptoms was not completely alleviated after surgery. DCA-MRA found abnormal vascular still exist after 3 months of surgery, but the blood supply artery was not found. The feeding artery from T10 may be the Adamkiewicz (AKA)in case 11. We seem to found the level of the stula about case 20 (Fig. 3) and 21, but did not nd the feeding artery by DCA-MRA and DSA also was negative. This case may classi ed it as PMAVF. with the guidance of convention T2 and the support of test bolus technology, the imaging success rate of DCA-MRA is very high, which can resolve the evaluation of SVMs,identifying the location of the feeding artery to guide DSA and assist in treatment planning. The MRA technique used in the study is three-phase MRA technique and 43 seconds for one phase but it can provide more temporal information for better image post-processing.

Conclusion
DCA-MRA at 3.0T is highly sensitive and accurate for the detection and characterization of SVMs, especially for SDAVF. They are reliable, rapid and operability, and may take place of DSA in iodine contrast agent allergy cases.

Declarations
Ethics approval: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.

Consent to participate:
Informed consent was obtained from all individual participants included in the study.

Consent for publication:
Authors are responsible for correctness of the statements provided in the manuscript.