Advances in Intraoperative Imaging for Vascular Neurosurgery.

Cerebrovascular surgery has many intraoperative imaging modalities available. Modern technologies include intraoperative digital subtraction angiogram, indocyanine green (ICG) angiography, relative fluorescent measurement with ICG, and ultrasound. Each of these can be used effectively in the treatment of open aneurysm and arteriovenous malformation surgeries, in addition to arteriovenous fistula surgery, and cerebral bypass surgery.

Diagnostic Performance of Carotid Ring Sign on CT-Angiography in Internal Carotid True Occlusion.

BACKGROUND: To differentiate between pseudo occlusion (PO) and true occlusion (TO) of internal carotid artery (ICA) is important in thrombectomy treatment planning for patients with acute ischemic stroke. Although delayed contrast filling has been differentiated carotid PO from TO, its application has been limited by the implementations of multiphasic computed tomography angiography. In this study, we hypothesized that carotid ring sign, which is readily acquired from single-phasic CTA, can sufficiently differentiate carotid TO from PO. METHODS: One thousand four hundred and twenty patients with anterior circulation stroke receiving endovascular therapy were consecutively recruited through a hospital- and web-based registry. Two hundred patients with nonvisualization of the proximal ICA were included in the analysis after a retrospective screening. Diagnosis of PO or TO of the cervical segment of ICA was made based on digital subtraction angiography. Diagnostic performances of carotid ring sign on arterial-phasic CTA and delayed contrast filling on multiphasic computed tomography angiography were evaluated and compared. RESULTS: One-hundred twelve patients had ICA PO and 88 had TO. Carotid ring sign was more common in patients with TO (70.5% versus 6.3%; P<0.001), whereas delayed contrast filling was more common in PO (94.9% versus 7.7%; P<0.001). The sensitivity and specificity of carotid ring sign in diagnosing carotid TO were 0.70 and 0.94, respectively, whereas sensitivity and specificity of delayed contrast filling was 0.95 and 0.92 in judging carotid PO. CONCLUSIONS: Carotid ring sign is a potent imaging marker in diagnosing ICA TO. Carotid ring sign could be complementary to delayed contrast filling sign in differentiating TO from PO, in particular in centers with only single-phasic CTA.

[Presurgical Simulation for Brain Arteriovenous Malformation].

Surgical extirpation of brain arteriovenous malformations(AVMs)requires precise pre-surgical simulation. Utilizing image software, widely used with picture archiving and communication systems(PACS), surgeons can generate simulation images that precisely illustrate the proper feeders, passing arteries, and drainers. The crucial steps for creating informative simulation images include: (1)the free rotation of reconstructed 3D digital subtraction angiography(DSA)images; (2)removal of irrelevant arteries(the most important procedure); and(3)construction of stereo imagery of the "core images." This article presents a detailed description of these procedures.

Evaluating the diagnostic accuracy of 3D contrast-enhanced magnetic resonance angiography versus digital subtraction angiography in spinal dural arteriovenous fistulas.

OBJECTIVE: Spinal dural arteriovenous fistulas (SDAVFs) often go undiagnosed, leading to irreversible spinal cord dysfunction. Although digital subtraction angiography (DSA) is the gold standard for diagnosing SDAVF, DSA is invasive and operator dependent, with associated risks. MR angiography (MRA) is a promising alternative. This study aimed to evaluate the performance of MRA as an equal alternative to DSA in investigating, diagnosing, and localizing SDAVF. METHODS: Prospectively collected data from a single neurosurgeon at a large tertiary academic center were searched for SDAVFs. Eligibility criteria included any patient with a surgically proven SDAVF in whom preoperative DSA, MRA, or both had been obtained. The eligible patients formed a consecutive series, in which they were divided into DSA and MRA groups. DSA and MRA were the index tests that were compared to the surgical SDAVF outcome, which was the reference standard. Accurate diagnosis was considered to have occurred when the imaging report matched the operative diagnosis to the correct spinal level. Comparisons used a two-sample t-test for continuous variables and Fisher-Freeman-Halton's exact test for categorical variables, with p < 0.05 specifying significance. Univariate, bivariate, and multivariate analyses were conducted to investigate group associations with DSA and MRA accuracy. Positive predictive value, sensitivity, and accuracy were calculated. RESULTS: A total of 27 patients with a mean age of 63 years underwent surgery for SDAVF. There were 19 male (70.4%) and 8 female (29.6%) patients, and the mean duration of symptoms at the time of surgery was 14 months (range 2-48 months). Seventeen patients (63%) presented with bowel or bladder incontinence. Bivariate analysis of the DSA and MRA groups further revealed no significant relationships between the characteristics and accuracy of SDAVF diagnosis. MRA was found to be more sensitive and accurate (100% and 73.3%) than DSA (85.7% and 69.2%), with a subanalysis of the patients with both preoperative MRA and DSA showing that MRA had a greater positive predictive value (78.6 vs 72.7), sensitivity (100 vs 72.7), and accuracy (78.6 vs 57.1) than DSA. CONCLUSIONS: In surgically proven cases of SDAVFs, the authors determined that MRA was more accurate than DSA for SDAVF diagnosis and localization to the corresponding vertebral level. Incomplete catheterization at each vertebral level may result in the failure of DSA to detect SDAVF.

Application of Spinal Subtraction and Bone Background Fusion CTA in the Accurate Diagnosis and Evaluation of Spinal Vascular Malformations.

BACKGROUND AND PURPOSE: Accurate pretreatment diagnosis and assessment of spinal vascular malformations using spinal CTA are crucial for patient prognosis, but the postprocessing reconstruction may not be able to fully depict the lesions due to the complexity inherent in spinal anatomy. Our purpose was to explore the application value of the spinal subtraction and bone background fusion CTA (SSBBF-CTA) technique in precisely depicting and localizing spinal vascular malformation lesions. MATERIALS AND METHODS: In this retrospective study, patients (between November 2017 and November 2022) with symptoms similar to those of spinal vascular malformations were divided into diseased (group A) and nondiseased (group B) groups. All patients underwent spinal CTA using Siemens dual-source CT. Multiplanar reconstruction; routine bone subtraction, and SSBBF-CTA images were obtained using the snygo.via and ADW4.6 postprocessing reconstruction workstations. Multiple observers researched the following 3 aspects: 1) preliminary screening capability using original images with multiplanar reconstruction CTA, 2) the accuracy and stability of the SSBBF-CTA postprocessing technique, and 3) diagnostic evaluation of spinal vascular malformations using the 3 types of postprocessing images. Diagnostic performance was analyzed using receiver operating characteristic analysis, while reader or image differences were analyzed using the Wilcoxon signed-rank test or the Kruskal-Wallis rank sum test. RESULTS: Forty-nine patients (groups A and B: 22 and 27 patients; mean ages, 44.0 [SD, 14.3] years and 44.6 [SD,15.2] years; 13 and 16 men) were evaluated. Junior physicians showed lower diagnostic accuracy and sensitivity using multiplanar reconstruction CTA (85.7% and 77.3%) than senior physicians (93.9% and 90.9%, 98% and 95.5%). Short-term trained juniors achieved SSBBF-CTA image accuracy similar to that of experienced physicians (P > .05). In terms of the visualization and localization of spinal vascular malformation lesions (nidus/fistula, feeding artery, and drainage vein), both multiplanar reconstruction and SSBBF-CTA outperformed routine bone subtraction CTA (P = .000). Compared with multiplanar reconstruction, SSBBF-CTA allowed less experienced physicians to achieve superior diagnostic capabilities (comparable with those of experienced radiologists) more rapidly (P < .05). CONCLUSIONS: The SSBBF-CTA technique exhibited excellent reproducibility and enabled accurate pretreatment diagnosis and assessment of spinal vascular malformations with high diagnostic efficiency, particularly for junior radiologists.

Utility of marking and fusion image-guided technique with cone-beam CT in kidney ruptured haemorrhage without extravascular leakage in angiography: a pilot study.

OBJECTIVE: To explore the feasibility of using marking and fusion image-guided technique with cone-beam CT (CBCT) in cases of kidney ruptured haemorrhage without extravascular leakage in digital subtraction angiography (DSA) images. METHODS: This is a retrospective case-control study that included 43 patients who underwent transcatheter arterial embolization for kidney ruptured haemorrhage and difficult haemostasis. The patients were divided into two groups: the CBCT group (cases without extravascular leakage observed in angiography) and the control group (cases with clearly identifiable target vessels in angiography). The baseline characteristics and clinical outcomes were collected and analysed. RESULTS: The results showed no statistically significant differences in the duration of the procedure and intraoperative blood transfusion between the control and CBCT groups (P > .05). The study clarified that the CBCT group had a significantly higher rate of improvement of gross haematuria compared to the control group (P < .05). The CBCT group showed a greater increase in haemoglobin and a lesser increase in creatinine. The clinical success rates were 87.5% in the control group and 90.9% in the CBCT group (P > .05). CONCLUSIONS: The marking and fusion image-guided technique is useful in cases of kidney ruptured haemorrhage without extravascular leakage of contrast agent. The technique is safe, feasible, and effective, and we believe it is superior to purely DSA-guidance. ADVANCES IN KNOWLEDGE: The use of the marking and fusion image-guided technique is recommended to overcome the challenge of undetectable target vessels during interventional procedures. This technique is considered as non-inferior to purely DSA-guided interventional procedures where the target vessels are clearly identifiable.

FMB: Dual-view fusion and registration of 2D DSA images and 3D MRA images for neurointerventional-based procedures.

OBJECTIVE: Alignment between preoperative images (high-resolution magnetic resonance imaging, magnetic resonance angiography) and intraoperative medical images (digital subtraction angiography) is currently required in neurointerventional surgery. Treating a lesion is usually guided by a 2D DSA silhouette image. DSA silhouette images increase procedure time and radiation exposure time due to the lack of anatomical information, but information from MRA images can be utilized to compensate for this in order to improve procedure efficiency. In this paper, we abstract this into the problem of relative pose and correspondence between a 3D point and its 2D projection. Multimodal images have a large amount of noise and anomalies that are difficult to resolve using conventional methods. According to our research, there are fewer multimodal fusion methods to perform the full procedure. APPROACH: Therefore, the paper introduces a registration pipeline for multimodal images with fused dual views is presented. Deep learning methods are introduced to accomplish feature extraction of multimodal images to automate the process. Besides, the paper proposes a registration method based on the Factor of Maximum Bounds (FMB). The key insights are to relax the constraints on the lower bound, enhance the constraints on the upper bounds, and mine more local consensus information in the point set using a second perspective to generate accurate pose estimation. MAIN RESULTS: Compared to existing 2D/3D point set registration methods, this method utilizes a different problem formulation, searches the rotation and translation space more efficiently, and improves registration speed. SIGNIFICANCE: Experiments with synthesized and real data show that the proposed method was achieved in accuracy, robustness, and time efficiency.

Synthetic interpolated DSA for radiation exposure reduction via gamma variate contrast flow modeling: a retrospective cohort study.

BACKGROUND: Digital subtraction angiography (DSA) yields high cumulative radiation dosages (RD) delivered to patients. We present a temporal interpolation of low frame rate angiograms as a method to reduce cumulative RDs. METHODS: Patients undergoing interventional evaluation and treatment of cerebrovascular vasospasm following subarachnoid hemorrhage were retrospectively identified. DSAs containing pre- and post-intervention runs capturing the full arterial, capillary, and venous phases with at least 16 frames each were selected. Frame rate reduction (FRR) of the original DSAs was performed to 50%, 66%, and 75% of the original frame rate. Missing frames were regenerated by sampling a gamma variate model (GVM) fit to the contrast response curves to the reduced data. A formal reader study was performed to assess the diagnostic accuracy of the "synthetic" studies (sDSA) compared to the original DSA. RESULTS: Thirty-eight studies met inclusion criteria (average RD 1,361.9 mGy). Seven were excluded for differing views, magnifications, or motion. GVMs fit to 50%, 66%, and 75% FRR studies demonstrated average voxel errors of 2.0 ± 2.5% (mean ± standard deviation), 6.5 ± 1.5%, and 27 ± 2%, respectively for anteroposterior projections, 2.0 ± 2.2%, 15.0 ± 3.1%, and 14.8 ± 13.0% for lateral projections, respectively. Reconstructions took 0.51 s/study. Reader studies demonstrated an average rating of 12.8 (95% CI 12.3-13.3) for 75% FRR, 12.7 (12.2-13.2) for 66% FRR and 12.0 (11.5-12.5) for 50% FRR using Subjective Image Grading Scale. Kendall's coefficient of concordance resulted in W = 0.506. CONCLUSION: FRR by 75% combined with GVM reconstruction does not compromise diagnostic quality for the assessment of cerebral vasculature. RELEVANCE STATEMENT: Using this novel algorithm, it is possible to reduce the frame rate of DSA by as much as 75%, with a proportional reduction in radiation exposure, without degrading imaging quality. KEY POINTS: • DSA delivers some of the highest doses of radiation to patients. • Frame rate reduction (FRR) was combined with bolus tracking to interpolate intermediate frames. • This technique provided a 75% FRR with preservation of diagnostic utility as graded by a formal reader study for cerebral angiography performed for the evaluation of cerebral vasospasm. • This approach can be applied to other types of angiography studies.

Improving image quality consistency and diagnostic accuracy in lower extremity CT angiography using a split-bolus contrast injection protocol.

OBJECTIVES: To evaluate the clinical value of using a split-bolus contrast injection protocol in improving image quality consistency and diagnostic accuracy in lower extremity CT angiography (CTA). METHODS: Fifty (mean age, 66 ± 12 years) and 39 (mean age, 66 ± 11 years) patients underwent CTA in the lower extremity arteries using split-bolus and fixed-bolus injection schemes, respectively. The objective and subjective image quality of the 2 groups were compared and the diagnostic efficacy for the degree of vessel stenosis was compared using digital subtraction angiography as the gold standard. A P < .05 was considered statistically significant. RESULTS: In comparison with the fixed-bolus scheme, the split-bolus scheme greatly improved the consistency of image quality of the low extremities by significantly increasing the arterial enhancement (337.87 ± 64.67HU vs. 254.74 ± 71.58HU, P < .001), signal-to-noise ratio (22.58 ± 11.64 vs. 7.14 ± 1.98, P < .001), and contrast-to-noise ratio (37.21 ± 10.46 vs. 31.10 ± 15.40, P = .041) in the infrapopliteal segment. The subjective image quality was better (P < .001) and the diagnostic accuracy was higher in the split-bolus group than in the fixed-bolus group (96.00% vs. 91.67%, P < .05, for diagnosing >50% stenosis, and 97.00% vs. 89.10%, P < .05, for diagnosing occlusion) for the infrapopliteal segment arteries. CONCLUSIONS: Compared with the fixed-bolus injection scheme, the split-bolus injection scheme improves the image quality consistency and diagnostic accuracy especially for the infrapopliteal segment arteries in lower extremity CTA. ADVANCES IN KNOWLEDGE: (1) The split-bolus injection scheme of CTA of the lower extremity arteries improves the overall image quality, uniformity of contrast enhancement. (2) Compared with the fixed-bolus injection scheme, the split-bolus injection scheme especially improves the infrapopliteal segment arteries image quality and diagnostic efficacy.

Diagnostic feasibility of middle cerebral artery stenosis or occlusion evaluated by TCCS and CEUS: Repeatability, reproducibility, and diagnostic agreement with DSA.

AIM: This study aimed to evaluate the feasibility of transcranial color-coded sonography (TCCS) and contrast-enhanced ultrasound (CEUS) in assessing middle cerebral artery (MCA) stem stenosis or occlusion compared to digital subtraction angiography (DSA). METHODS: A total of 48 cases including 96 MCAs suspected stem stenosis or obstruction in the MCA were assessed by TCCS, CE-TCCS, and DSA. The diameters of the most severe stenosis (Ds), proximal normal artery (Dn), and diameter stenosis rate of MCA were measured using both the color doppler flow imaging (CDFI) modality of TCCS or CEUS and the CEUS imaging modality. The intraclass correlation coefficients (ICCs) and 95 % confidence intervals (CI) were evaluated, and a weighted Kappa value was used to evaluate the intra-observer agreement, inter-observer agreement, agreement between CDFI modality and DSA stenosis or occlusion, and agreement between CEUS imaging modality and DSA stenosis or occlusion. RESULTS: The ICC results indicated excellent repeatability and reproducibility (all ICCs > 0.75; weighted Kappa values >0.81). Compared with DSA, the weighted Kappa values and 95 % CIs of stenosis (the first measurement was taken by two observers) of CDFI modality and CEUS imaging modality were 0.175 (0.041, 0.308) and 0.779 (0.570, 0.988) for observers A and 0.181 (0.046, 0.316) and 0.779 (0.570, 0.988) for observers B respectively. CONCLUSION: This study indicates that inter- and intra-observer agreements were good for the direct method of measuring percentages of MCA stenosis by TCCS and CEUS. CEUS imaging modality is a new and reliable imaging modality approach to evaluate the MCAs stenosis and occlusion.

Automated image registration of cerebral digital subtraction angiography.

PURPOSE: Our aim is to automatically align digital subtraction angiography (DSA) series, recorded before and after endovascular thrombectomy. Such alignment may enable quantification of procedural success. METHODS: Firstly, we examine the inherent limitations for image registration, caused by the projective characteristics of DSA imaging, in a representative set of image pairs from thrombectomy procedures. Secondly, we develop and assess various image registration methods (SIFT, ORB). We assess these methods using manually annotated point correspondences for thrombectomy image pairs. RESULTS: Linear transformations that account for scale differences are effective in aligning DSA sequences. Two anatomical landmarks can be reliably identified for registration using a U-net. Point-based registration using SIFT and ORB proves to be most effective for DSA registration and are applicable to recordings for all patient sub-types. Image-based techniques are less effective and did not refine the results of the best point-based registration method. CONCLUSION: We developed and assessed an automated image registration approach for cerebral DSA sequences, recorded before and after endovascular thrombectomy. Accurate results were obtained for approximately 85% of our image pairs.

Enhanced vessel wall magnetic resonance imaging in the follow-up of intracranial aneurysms treated with flow diversion.

OBJECTIVE: This study aimed to compare the efficacy of enhanced 3D T1-weighted black-blood fast-spin-echo vessel wall magnetic resonance imaging (eVW-MRI) and time-of-flight magnetic resonance angiography (TOF MRA) for follow-up evaluation of aneurysms treated with flow diversion (FD). METHODS: Our study enrolled 77 patients harboring 84 aneurysms treated with FD. Follow-up was by MRI (eVW-MRI and TOF MRA) and digital subtraction angiography (DSA). Two radiologists, blinded to DSA examination results, independently evaluated the images of aneurysm occlusion and parent artery patency using the Kamran-Byrne Scale. Interobserver diagnostic agreement and intermodality diagnostic agreement were acquired. Pretreatment and follow-up aneurysm wall enhancement (AWE) patterns were collected. RESULTS: Based on the Kamran-Byrne Scale, the intermodality agreement between eVW-MRI and DSA was better than TOF MRA versus DSA for aneurysm remnant detection (weighted ĸ = 0.891 v. 0.553) and parent artery patency (ĸ = 0.950 v. 0.221). Even with the coil artifact, the consistency of eVW-MRI with DSA for aneurysm remnant detection was better than that of TOF MRA (weighted ĸ = 0.891 v. 0.511). The artifact of adjunctive coils might be more likely to affect the accuracy in evaluating parent artery patency with TOF MRA than with eVW-MRI (ĸ = 0.077 v. 0.788). The follow-up AWE patterns were not significantly associated with pretreatment AWE patterns and aneurysm occlusion. CONCLUSIONS: The eVW-MRI outperforms TOF MRA as a reliable noninvasive and nonionizing radioactive imaging method for evaluating aneurysm remnants and parent artery patency after FD. The significance of enhancement patterns on eVW-MRI sequences needs more exploration. CLINICAL RELEVANCE STATEMENT: The application of enhanced vessel wall magnetic resonance imaging has proven to be a promising tool to depict aneurysm remnant and parent artery stenosis in order to tailor the antiplatelet therapy strategy in patients after flow diversion. KEY POINTS: • Enhanced vessel wall magnetic resonance imaging has an emerging role in depicting aneurysm remnant and parent artery patency after flow diversion. • With or without the artifact from adjunctive coils, enhanced vessel wall magnetic resonance imaging was better than TOF MRA in detecting aneurysm residual and parent artery stenosis by using DSA imaging as the standard. • Enhanced vessel wall magnetic resonance imaging holds potential to be used as an alternative to DSA for routine aneurysm follow-up after flow diversion.

Comparative Study of the Diagnostic Value of Zero-Echo-Time Magnetic Resonance Angiography With Time-of-Flight Magnetic Resonance Angiography for Intracranial Aneurysm.

OBJECTIVE: Intracranial aneurysm (IAN) is a class of cerebrovascular diseases with a serious threat to patients, and an accurate diagnosis of IAN is very important for both selection of the appropriate therapy and prediction of the prognosis. This study aimed to evaluate the diagnostic values of zero-echo-time magnetic resonance angiography (ZTE-MRA) and time-of-flight magnetic resonance angiography (TOF-MRA) in patients with IAN. METHODS: Digital subtraction angiography, ZTE-MRA, and TOF-MRA were performed in 18 patients diagnosed with IAN. The images of ZTE-MRA and TOF-MRA were compared for image quality, qualitative diagnosis, detailed diagnosis, number of thrombi, and residual aneurysm lumen, with digital subtraction angiography as the reference. RESULTS: Zero-echo-time MRA and TOF-MRA did not show a significant difference in image quality or detailed information (including aneurysm size, growth direction, and angle with the aneurysm-carrying vessel) ( P > 0.05). However, ZTE-MRA showed advantages over TOF-MRA in terms of qualitative diagnosis (sensitivity and specificity), intra-aneurismal thrombus detection, and residual aneurysm lumen detection after embolization ( P < 0.05). CONCLUSIONS: Compared with TOF-MRA, ZTE-MRA showed greater diagnostic value for IAN patients in terms of qualitative diagnosis, as well as the detection of intra-aneurysm thrombi and residual aneurysm lumen after embolization.

Estimating Pulsatile Flow Velocity using Four-Dimensional Digital Subtraction Angiography.

Digital subtraction angiography (DSA) is a X-ray based imaging modality for interventional procedures, and remains criterion standard for diagnosing vascular diseases. The imaging protocol of DSA involves administration of a foreign contrast medium into the blood vessel that opacifies the vasculature during the imaging. Using two-dimensional (2D) DSA with high temporal resolution, it was recently demonstrated that the pulsatile velocity can be estimated by evaluating the temporal and spatial variations of the contrast medium distributions in the blood vessel. In this paper, we evaluate the feasibility to estimate the pulsatile flow velocity using the four-dimensional (4D) DSA. To overcome the noise and artefacts of 4D-DSA data, a empirical mode decomposition plus autocorrelation based method is proposed to estimate the pulsatile velocities, and the pulsatile velocities estimated using 2D-DSA are used as reference for comparison.Clinical Relevance-4D-DSA encompasses both structural and temporal information; it theoretically reduces the need of multiple scans, hence reducing the radiation doses. The estimated pulsatile flow velocities open up a new parameter for hemodynamic studies and potential for real-time diagnostic and therapeutic monitoring during interventional procedures.

Dynamic evaluation of unruptured intracranial aneurysms by 4D-CT angiography: comparison with digital subtraction angiography (DSA) and surgical findings.

BACKGROUND: This study was to prospectively investigate the feasibility of four-dimensional computed tomography angiography (4D-CTA) with electrocardiogram-gated (ECG) reconstruction for preoperative evaluation of morphological parameters, and compared with digital subtraction angiography (DSA). We also aimed to detect pulsation in unruptured intracranial aneurysms (UIAs) by using 4D-CTA, as a potential predicting factor of growth or rupture. MATERIALS: 64 patients with 64 UIAs underwent ECG-gated dynamic 4D-CTA imaging before treatment, of which 46 patients additionally underwent DSA. Original scanning data were reconstructed to produce 20 data sets of cardiac cycles with 5%-time intervals. The extent of agreement on UIAs morphological features assessed with 4D-CTA and DSA was estimated using the k coefficient of the Kappa test. The radiation doses were also calculated and compared between 4D-CTA and DSA. In the aneurysmal surgically treated in our institution, we were able to compare the surgical findings of the aneurysm wall with 4D-CTA images. We performed long-term follow-up on untreated patients. RESULTS: The morphological characteristics detected by 4D-CTA and DSA were consistent in aneurysm location (k = 1.0), shape (k = 0.76), maximum diameter (k = 0.94), aneurysm neck (k = 0.79) and proximity to parent and branch vessels (k = 0.85). 4D-CTA required lower radiation doses (0.32 ± 0.11 mSv) than DSA (0.84 ± 0.37 mSv, P < 0.001). Pulsation was detected in 26 of the 64 unruptured aneurysms, and all underwent neurosurgical clipping or interventional embolization. In aneurysms surgically treated in our hospital, we observed a significant correlation between 4D-CTA findings and surgical evaluation of the aneurysmal wall, in particular the irregular pulsations detected on 4D-CTA have demonstrated to correspond to dark-reddish thinner wall at surgery. CONCLUSIONS: In this proof-of-concept study, 4D-CTA provided real-time, non-invasive preoperative assessments of UIAs comparable to DSA. Moreover, optimal correlation between the irregular pulsation detected by 4D-CTA and the surgical findings support a possible role of this technique to identify aneurysms with a higher risk of rupture.

4D-DSA for Assessment of the Angioarchitecture and Grading of Cranial Dural AVF.

BACKGROUND AND PURPOSE: Time-resolved 3D rotational angiography (4D-DSA) has been used to demonstrate details of the angioarchitecture of AVM, whereas it has rarely been used to describe features of dural AVF. In this exploratory study, we analyzed dural AVFs with a novel 4D software prototype, developed and provided by Siemens, to determine whether identification of the location of the fistulous point, grading, and treatment planning were feasible. MATERIALS AND METHODS: 4D-DSA volumes were calculated from existing 3D rotational angiography data sets of patients with dural AVFs. The 4D-DSA volumes were displayed in a virtual DSA mode and MPR or MIP in 3 orthogonal planes and compared with 2D-DSA by 2 experienced neuroradiologists. Fusions with unenhanced CT or MR images were used to improve visualization of adjacent anatomic structures. RESULTS: Comparison with 2D-DSA showed that evaluation of the fistulous point and grading according to the classification of Borden, Cognard, or Barrow was feasible in 26 of 27 cases. In 8 of 27 cases, 4D-DSA was considered advantageous for determining the fistulous point and the course of the draining vein in the dural AVF with cortical venous drainage, especially in the frontoethmoidal and frontoparietal regions. In 6 cases, the display of angioarchitecture was considered inferior to that of 2D-DSA due to motion artifacts, suboptimal selection of the injected vessel, and lack of temporal resolution. CONCLUSIONS: Detailed analysis of dural AVFs according to the standardized display of 4D-DSA volumes was feasible and helpful in understanding the angioarchitecture in selected cases. Further improvement and validation of the 4D software should solidify the complementary role of 4D-DSA to conventional 2D-DSA series.

Quantifying Change in Perfusion after Genicular Artery Embolization with Parametric Analysis of Intraprocedural Digital Subtraction Angiograms.

PURPOSE: To quantify perfusion changes during genicular artery embolization (GAE) with the qualitatively described "pruning" technique using parametric analysis. MATERIALS AND METHODS: A total of 12 patients underwent unilateral GAE with a total of 36 vessels embolized. Among 34 of the 36 vessels embolized, regions of interest (ROIs) were placed on parent vessels (PVs) and hyperemic target vessels (TVs) before and after GAE. For each ROI, peak intensity (PI), time to arrival (TTA), and area under the curve (AUC) were computed and compared between PV and TV. Volume of embolic administered was correlated with adverse events. RESULTS: No change was seen in PI, TTA, and AUC in the PV after GAE. Reduction in AUC (1,495.7 ± 521.5 vs 1,667.4 ± 574.0; P << .01) and PI (195.1 ± 43.8 vs 224.3 ± 49.2; P << .01) with increase in TTA (3.42 s ± 1.70 vs 1.92 s ± 1.45; P << .01) within the TV were observed after GAE. Median follow-up time was 89 days (range, 21-254 days). Reduction in clinical symptoms was also noted based on the Western-Ontario and McMaster Universities Arthritis Index total and pain scale at 1 month (total, 42.9% ± 23.0; pain, 54.4% ± 9.8; P << .01) and 3 months (total, 42.5% ± 14.9; pain, 57.8% ± 10.6; P << .01). Eight total mild adverse events (minor/self-limiting) were noted per Society of Interventional Radiology guidelines. A larger volume of embolic was observed in knees with skin changes (3.4 mL ± 0.4 vs 1.7 mL ± 0.4; P << .001). Furthermore, all skin changes were seen with embolic volumes >3.0 mL. CONCLUSIONS: Quantification of intraprocedural perfusion changes with GAE demonstrated reduced flow to the TV with maintained flow in the PV and acceptable clinical outcomes. A potential relationship between embolic volume and nontarget embolization was also highlighted.

Drawing time-density curve with Fiji/ImageJ: An alternative approach for parametric coding of cerebral digital subtraction angiography.

BACKGROUND: Quantitative spatiotemporal analysis of digital subtraction angiography could support clinical decision making for the management of cerebral vascular disease. However, there is a lack of free and user-friendly applications. The objective of our study is to devise a free and simple solution for parametric coding of digital subtraction angiography. NEW METHOD: By driving the time-density curves in the region of interest, the digital subtraction angiography images were color-coded and quantitatively analyzed using fully open-source and free software (Fiji/ImageJ). The similarity factor (f2) was used to compare the resolution profiles between time-density curves generated with commercial software on the Siemens workstation (syngo iFlow, Siemens Healthcare, Berlin, Germany) and our method. RESULTS AND COMPARISON WITH EXISTING METHOD: Sixteen patients diagnosed with acute ischemic stroke resulting from acute occlusion of the distal internal carotid artery or the first segment of the middle cerebral artery were selected for analysis. Angiography images were successfully processed with syngo iFlow and Fiji/ImageJ. The images processed with Fiji/ImageJ provided excellent anatomic and hemodynamic details. In all patients, the similarity factor (f2) values of the time-density curves derived from the same region of interest were 99.90 (range 99.85-99.95). CONCLUSIONS: The ImageJ/Fiji software provides a user-friendly and free alternative for parametric coding of digital subtraction angiography.

Analysis of Magnetic Resonance Imaging Perfusion Parameters for the Identification of Spinal Metastatic Tumors with Rich Blood Supply.

PURPOSE: To determine the reliability of dynamic magnetic resonance imaging (MRI) perfusion parameters for the evaluation of blood supply to spinal metastatic tumors. METHODS: A total of 36 patients with spinal metastasis who underwent dynamic contrast-enhanced magnetic resonance spinal perfusion imaging at Tianjin Hospital from December 2018 to December 2020 were reviewed. Subsequently, the patients underwent corresponding preoperative examination using digital subtraction angiography of the spine at the hospital and were divided into 2 groups accordingly. Differences in dynamic MRI perfusion parameters between the 2 groups were analyzed. RESULTS: There were statistically significant differences between the 2 groups in the quantitative dynamic contrast-enhanced MRI perfusion parameters vascular permeability and plasma volume, as well as semi-quantitative peak enhancement and blood flow ratio parameters. CONCLUSIONS: Dynamic MRI perfusion may distinguish spinal metastatic lesions with rich blood supply from those with poor blood supply and may help clinicians identify patients that can benefit from invasive spinal angiography and preoperative embolization. This technique may also provide guidance on decision taking for surgery basing on dynamic MRI perfusion parameters.

Added Value of Cone-Beam CT to Identify Arterial Supply during Genicular Artery Embolization for Knee Osteoarthritis.

PURPOSE: To evaluate if the addition of cone-beam computed tomography (CT) to digital subtraction angiography (DSA) improves the identification of the genicular arteries during genicular artery embolization (GAE) for knee pain secondary to osteoarthritis (OA). MATERIALS AND METHODS: This single-center study retrospectively analyzed 222 patients who underwent GAE for painful knee OA between May 2018 and April 2022. Intraprocedural cone-beam CT and DSA images were reviewed independently by 2 sets of interventional radiologists. DSA was performed for all patients. Technically adequate cone-beam CT was available for 205 patients (92.3%). The presence of the genicular arteries identified by cone-beam CT and DSA was compared using Φ coefficients. Embolization targets identified by both cone-beam CT and DSA were evaluated against those identified by DSA alone. RESULTS: Genicular arteries with the highest concordance between cone-beam CT and DSA were the inferior lateral (196 vs 198; Φ = 0.3530; P < .0001), superior lateral (197 vs 200; Φ = 0.3060; P < .0001), and superior medial genicular (186 vs 161; Φ = 0.2836; P < .0001) arteries. Cone-beam CT demonstrated higher rates of detection of the inferior medial (195 vs 178; Φ = 0.04573; P = .5150) and median genicular arteries (200 vs 192; Φ = 0.04573; P = .5150). Meanwhile, genicular arteries less frequently identified by cone-beam CT were the descending genicular (197 vs 200; Φ = -0.03186; P = .6502), superior patellar (175 vs 184; Φ = 0.1332; P = .0569), and recurrent anterior tibial (156 vs 186; Φ = 0.01809; P = .7969) arteries. Cone-beam CT in combination with DSA identified 13.4% (372 vs 328) more targets compared to DSA alone. CONCLUSIONS: Based on the results of the current study, cone-beam CT serves as a valuable adjunct for visualizing the genicular arteries during GAE, and together with DSA, it identifies more potential embolization targets.