Agreement between single plane and biplane derived angiographic fractional flow reserve in patients with intermediate coronary artery stenosis.

Fractional flow reserve (FFR) is often used to evaluate the physiological severity of intermediate coronary stenoses, but less-invasive assessment methods are desirable. We evaluated the feasibility of angiographic FFR (angioFFR) calculated from two projections acquired simultaneously by a biplane C-arm system and angioFFR calculated from two projections acquired independently by one plane of the same biplane C-arm system. AngioFFR was validated against FFR in terms of detection of hemodynamically relevant coronary artery stenoses. Twenty-two Patients who underwent angiography and FFR for coronary artery disease were included. We used a non-commercial prototype to calculate biplane angioFFR for 22 vessels (19 LAD, 1 LCx, 2 RCA) and single plane angioFFR for 17 of the same 22 vessels. FFR < 0.8 was measured in 8 vessels. The Pearson correlation coefficients with FFR were 0.55 for single plane angioFFR and 0.61 for biplane angioFFR and the diagnostic accuracies were 88% (95% CI 73-100%) for single plane angioFFR and 86% (95% CI 72-100%) for biplane angioFFR. Bland-Altman plots revealed that compared with FFR, the limits of agreement for single plane angioFFR were - 0.07 to 0.19 (mean difference 0.06, p = 0.002) and the limits of agreement for biplane FFR were - 0.09 to 0.15 (mean difference 0.03, p = 0.03). In conclusion, angioFFR calculated from single or biplane acquisitions by a biplane C-arm is feasible and may evolve to a tool for less invasive imaging-based assessment of myocardial ischemia.

Intraoperative cone-beam CT with metal artifact reduction for assessment of the electrode position and the intracranial structures during deep brain stimulation procedure.

BACKGROUND: In deep brain stimulation (DBS) for Parkinson's disease (PD), the clinical outcome largely depends on the appropriate position of the electrode implanted in the targeted structure. In intraoperative cone-beam computed tomography (CT) performed for the evaluation of the electrode position, the metal artifact induced by the implanted electrode can prevent the precise localization of the electrode. Metal artifact reduction (MAR) techniques have been recently developed that can dramatically improve the visualization of objects by reducing metal artifacts after performing cone-beam CT. Hence, in this case series, we attempted to clarify the usefulness and accuracy of intraoperative cone-beam CT with MAR (intraCBCTwM) by comparing with both intraoperative cone-beam CT without MAR (intraCBCTwoM) and conventional postoperative CT (post-CT) for the assessment of the implanted electrode position and the intracranial structures during DBS procedures. METHODS: Between November 2019 and December 2020, 10 patients with PD who underwent DBS at our institution were recruited, and the images of 9 patients (bilateral: n = 8, unilateral: n = 1) were analyzed. The artifact index (AI) in intraCBCTwM or intraCBCTwoM, and conventional post-CT were retrospectively assessed using the standard deviation of the region-of-interest around the implanted electrodes and background noise. Additionally, the Euclidean distances gap of electrode tip based on post-CT in each fusion image was compared between intraCBCTwM and intraCBCTwoM. RESULTS: The AI was significantly lower in intraCBCTwM than in intraCBCTwoM (P < 0.01). The mean Euclidean distance between the tip of the electrode in intraCBCTwM and in post-CT was significantly shorter compared to that in intraCBCTwoM (P < 0.05). CONCLUSIONS: The results reported here suggest that intraCBCTwM is a more useful and accurate method than intraCBCTwoM to assess the implanted electrode position and intracranial structures during DBS.

Diagnostic performance of intraoperative cone beam computed tomography compared with postoperative magnetic resonance imaging for detecting hemorrhagic transformation after endovascular treatment following large vessel occlusion.

OBJECTIVES: Early detection of hemorrhagic transformation (HT) in patients with large vessel occlusion (LVO) after endovascular treatment is important for postoperative patient management. We investigated the diagnostic performance of intraoperative cone beam computed tomography (CBCT) with reference standard magnetic resonance imaging (MRI) for detecting HT. MATERIALS AND METHODS: Consecutive patients with LVO treated by endovascular treatment who underwent intraoperative CBCT and postoperative MRI were included. Two observers evaluated all images for the presence of HT. Sensitivity and specificity for detecting HT were calculated with MRI as reference standard. The observers classified HT according to the European Cooperative Acute Stroke Study (ECASS). Inter-method and inter-rater agreement for the detection of HT and for the ECASS classification were assessed using kappa or weighted Brennan-Prediger (wBP) statistics. RESULTS: Images of 106 procedures (94 for anterior circulation) were analyzed. The sensitivity and specificity for detecting HT on CBCT were 0.77 and 0.83, respectively, for all procedures and 0.83 and 0.8, respectively, for anterior circulation. The inter-method agreement for HT detection (κ = 0.63 overall, κ = 0.69 anterior circulation) and ECASS classification (wBP = 0.67 overall, wBP = 0.77 anterior circulation) were substantial. The inter-rater agreement for HT detection (κ = 0.87 overall, κ = 0.85 anterior circulation) and for ECASS classification (wBP = 0.95 overall, wBP = 0.92 anterior circulation) were almost perfect. CONCLUSIONS: The diagnostic performance of CBCT for the detection of HT in stroke patients treated for LVO was acceptable with excellent inter-rater agreement. Intraoperative CBCT may be useful to trigger early interventions if HT is detected, although detailed classifications of HT may be difficult.

Rupture Risk of Small Unruptured Intracranial Aneurysms in Japanese Adults.

Background and Purpose- Therapeutic decision making for small unruptured intracranial aneurysms (<10 mm) is difficult. We aimed to develop a rupture risk model for small intracranial aneurysms in Japanese adults, including clinical, morphological, and hemodynamic parameters. Methods- We analyzed 338 small unruptured aneurysms; 35 ruptured during the observation period, and 303 remained stable. Clinical, morphological, and hemodynamic parameters were considered. Computational fluid dynamics was used to calculate hemodynamic parameters based on computed tomography images of all aneurysms in their unruptured state. Differences between the ruptured and unruptured groups were tested by the Mann-Whitney U or Fisher exact tests. Multivariate logistic regression was applied to obtain a rupture risk model. Its predictive ability was investigated by receiver operating characteristic analysis. Results- The risk model revealed that rupture may be more likely to in younger patients (odds ratio [OR], 0.92 for each age increase of 1 year [95% CI, 0.88-0.96] P<0.001) with multiple aneurysms (OR, 2.58 [95% CI, 1.07-6.19] P=0.03), located at a bifurcation (OR, 5.45 [95% CI, 1.87-15.85] P=0.002), with a bleb (OR, 4.09 [95% CI, 1.42-11.79] P=0.009), larger length (OR, 1.91 for each increase of 1 mm [95% CI, 1.42-2.57] P<0.001), and lower pressure loss coefficient (OR, 0.33 for each decrease of 1 unit [95% CI, 0.14-0.77] P=0.01). The sensitivity, specificity, and area under the curve were 0.800, 0.752, and 0.826 (95% CI, 0.739-0.914) respectively. Conclusions- Younger age, presence of multiple aneurysms, location at a bifurcation, presence of a bleb, larger length, and lower pressure loss coefficient were identified as risk factors for rupture of small intracranial aneurysms. The risk model should be validated in further studies.

4D Digital Subtraction Angiography for the Temporal Flow Visualization of Intracranial Aneurysms and Vascular Malformations.

PURPOSE: To assess the benefit and radiation dose of four-dimensional (4D) digital subtraction angiography (DSA) - a time resolved three-dimensional (3D) DSA application - to evaluate the flow and architecture of aneurysms and vascular malformations. METHODS: All patients with cerebrovascular disease were considered who underwent 4D-DSA at our institution between January 2015 and February 2016. For the aneurysm patients, we evaluated the image quality in terms of the visualization of contrast flow in the aneurysm on a 3-point scale (excellent, fair and poor). Interrater agreement between two raters was estimated using Cohen's Kappa statistics. For the shunt disease patients, the additional information obtained from the 4D-DSA was described for each disease. The median radiation dose and volume of contrast medium required for the acquisitions were estimated. RESULTS: A total of 173 patients underwent 4D-DSA; 126 intracranial aneurysms, 10 arteriovenous malformations (AVM), 15 dural arteriovenous fistula (dAVF) and 22 other diseases. For aneurysm patients, excellent and fair visualization of the intra-aneurysmal flow was observed in 27.7%, 72.3%, and excellent (κ = 0.9) agreement between the raters was found. For AVM and dAVF patients, 4D-DSA clarified the complex vasculature by viewing the discrete time phase of contrast filling. Median radiation dose for intracranial lesions was 79.6 mGy for 6s 4D-DSA, and 175 mGy for 12s 4D-DSA. The median amount of contrast medium used was 18.0 ml for 6s 4D-DSA and 21.0 ml for 12s 4D-DSA. CONCLUSIONS: 4D-DSA provided additional information regarding intra-aneurysmal flow and contributed to detect different component of nidus or shunt points.

Modified calcium subtraction in dual-energy CT angiography of the lower extremity runoff: impact on diagnostic accuracy for stenosis detection.

OBJECTIVES: To investigate the diagnostic accuracy of a modified three-material decomposition calcium subtraction (CS) algorithm for the detection of arterial stenosis in dual-energy CT angiography (DE-CTA) of the lower extremity runoff compared to standard image reconstruction, using digital subtraction angiography (DSA) as the reference standard. METHODS: Eighty-eight patients (53 males; mean age, 65.9 ± 11 years) with suspected peripheral arterial disease (PAD) who had undergone a DE-CTA examination of the lower extremity runoff between May 2014 and May 2015 were included in this IRB-approved, HIPAA-compliant retrospective study. Standard linearly blended and CS images were reconstructed and vascular contrast-to-noise ratios (CNR) were calculated. Two independent observers assessed subjective image quality using a 5-point Likert scale. Diagnostic accuracy for ≥ 50% stenosis detection was analyzed in a subgroup of 45 patients who had undergone additional DSA. Diagnostic accuracy parameters were estimated with a random-effects logistic regression analysis and compared using generalized estimating equations. RESULTS: CS datasets showed higher CNR (15.3 ± 7.3) compared to standard reconstructions (13.5 ± 6.5, p < 0.001). Both reconstructions showed comparable qualitative image quality scores (CS, 4.64; standard, 4.57; p = 0.220). Diagnostic accuracy (sensitivity, specificity, positive and negative predictive values) for CS reconstructions was 96.5% (97.5%, 95.6%, 90.9%, 98.1) and 93.1% (98.8%, 90.4%, 82.3%, 99.1%) for standard images. CONCLUSIONS: A modified three-material decomposition CS algorithm provides increased vascular CNR, equivalent qualitative image quality, and greater diagnostic accuracy for the detection of significant arterial stenosis of the lower extremity runoff on DE-CTA compared with standard image reconstruction. KEY POINTS: • Calcified plaques may lead to overestimation of stenosis severity and false positive results, requiring additional invasive digital subtraction angiography (DSA). • A modified three-material decomposition algorithm for calcium subtraction provides greater diagnostic accuracy for the detection of significant arterial stenosis of the lower extremity runoff compared with standard image reconstruction. • The application of this algorithm in patients with heavily calcified vessels may be helpful to potentially reduce inconclusive CT angiography examinations and the need for subsequent invasive DSA.

Diagnostic accuracy of low and high tube voltage coronary CT angiography using an X-ray tube potential-tailored contrast medium injection protocol.

OBJECTIVES: To compare the diagnostic accuracy between low-kilovolt peak (kVp) (≤ 100) and high-kVp (> 100) third-generation dual-source coronary CT angiography (CCTA) using a kVp-tailored contrast media injection protocol. METHODS: One hundred twenty patients (mean age = 62.6 years, BMI = 29.0 kg/m2) who underwent catheter angiography and CCTA with automated kVp selection were separated into two cohorts (each n = 60, mean kVp = 84 and 117). Contrast media dose was tailored to the kVp level: 70 = 40 ml, 80 = 50 ml, 90 = 60 ml, 100 = 70 ml, 110 = 80 ml, and 120 = 90 ml. Contrast-to-noise ratio (CNR) was measured. Two observers evaluated image quality and the presence of significant coronary stenosis (> 50% luminal narrowing). RESULTS: Diagnostic accuracy (sensitivity/specificity) with ≤ 100 vs. > 100 kVp CCTA was comparable: per patient = 93.9/92.6% vs. 90.9/92.6%, per vessel = 91.5/97.8% vs. 94.0/96.8%, and per segment = 90.0/96.7% vs. 90.7/95.2% (all P > 0.64). CNR was similar (P > 0.18) in the low-kVp vs. high-kVp group (12.0 vs. 11.1), as ws subjective image quality (P = 0.38). Contrast media requirements were reduced by 38.1% in the low- vs. high-kVp cohort (53.6 vs. 86.6 ml, P < 0.001) and radiation dose by 59.6% (4.3 vs. 10.6 mSv, P < 0.001). CONCLUSIONS: Automated tube voltage selection with a tailored contrast media injection protocol allows CCTA to be performed at ≤ 100 kVp with substantial dose reductions and equivalent diagnostic accuracy for coronary stenosis detection compared to acquisitions at > 100 kVp. KEY POINTS: • Low-kVp coronary CT angiography (CCTA) enables reduced contrast and radiation dose. • Diagnostic accuracy is comparable between ≤ 100 and > 100 kVp CCTA. • Image quality is similar for low- and high-kVp CCTA. • Low-kVp image acquisition is facilitated by automated tube voltage selection. • Tailoring contrast injection protocols to the automatically selected kVp-level is feasible.

Hemodynamic and morphological differences in cerebral aneurysms between before and after rupture.

OBJECTIVE: Although it has been proposed that aneurysm morphology is different after rupture, detailed research of the morphological changes using 3D imaging acquired before and after rupture has not been conducted because of the difficulty of data collection. Similarly, hemodynamic changes due to morphological alterations after rupture have not been analyzed. The aim of this study was to investigate the changes in morphology and hemodynamics observed after aneurysm rupture. METHODS: For 21 cerebral aneurysms (21 patients) that ruptured during observation, 3D geometry of the aneurysms and parent arteries were reconstructed based on the angiographic images before and after their rupture. In addition, using the reconstructed geometry, blood flow was simulated by computational fluid dynamics (CFD) analysis. Morphological and hemodynamic parameters were calculated both before and after rupture, and their changes from before to after were compared. RESULTS: In the morphological parameters, statistically significantly higher values were observed after rupture in height (before: 5.5 ± 2.1 mm, after: 6.1 ± 2.0 mm; p < 0.0001), aspect ratio (p = 0.002), aneurysm volume (p = 0.04), and undulation index (p = 0.005). In terms of hemodynamic changes, the mean normalized wall shear stress (NWSS) decreased significantly (before: 5.4 × 10-1 ± 2.9 × 10-1, after: 4.4 × 10-1 ± 2.8 × 10-1; p < 0.001) as well as the other NWSS parameters, including maximum and minimum NWSS, which were associated with stagnant flow due to the morphological changes after rupture. CONCLUSIONS: Aneurysm morphology was found to change after rupture into an elongated and irregular geometry, accompanied by an increase in aneurysm volume. These morphological changes were also associated with statistically significant hemodynamic alterations that produced low wall sheer stress by stagnant flow. The authors' results also provide the opportunity to explore and develop a risk evaluation method for aneurysm rupture based on prerupture morphology and hemodynamics by further exploration in this direction.

Three-dimensional fusion imaging to assess apposition of low-profile visualized intraluminal support stent for intracranial aneurysm coiling.

Objective: To investigate on three-dimensional (3D) fusion images the apposition of low-profile visualized intraluminal support (LVIS) stents in intracranial aneurysms after treatment and assess inter-rater reliability. Materials and methods: Records of all patients with unruptured intracranial aneurysms who were treated with the LVIS stent were retrospectively accessed and included in this study. Two neurosurgeons evaluated the presence of malapposition between the vessel walls and the stent trunk (crescent sign) and the vessel wall and the stent edges (edge malappostion) on 3D fusion images. These images were high-resolution cone-beam computed tomography images of the LVIS stent fused with 3D-digital subtraction angiography images of the vessels. Associations between malapposition and aneurysm location were assessed by Fisher's exact test, and inter-rater agreement was estimated using Cohen's kappa statistic. Results: Forty consecutive patients were included. In all patients, 3D fusion imaging successfully visualized the tantalum helical strands and the closed-cell structure of the nitinol material of the low-profile visualized intraluminal support. A crescent sign was observed in 27.5 % and edge malapposition in 47.5 % of the patients. Malapposition was not significantly associated with location (p = 0.23 crescent sign, p = 0.07 edge malapposition). Almost perfect (κ = 0.88) and substantial (κ = 0.76) agreements between the two raters were found for the detection of crescent signs and edge appositions, respectively. Conclusions: 3D fusion imaging provided clear visualization of the LVIS stent and parent arteries, and could detect malapposition with excellent inter-rater reliability. This technique may provide valuable guidance for surgeons in determining postoperative management.

Experimental study using phantom models of cerebral aneurysms and 4D-DSA to measure blood flow on 3D-color-coded images.

BACKGROUND: The current 3D-iFlow application can only measure the arrival time of contrast media through intensity values. If the flow rate could be estimated by 3D-iFlow, patient-specific hemodynamics could be determined within the scope of normal diagnostic management, eliminating the need for additional resources for blood flow rate estimation. OBJECTIVE: The aim of this study is to develop and validate a method for measuring the flow rate by data obtained from 3D-iFlow images - a prototype application in Four-dimensional digital subtraction angiography (4D-DSA). METHODS: Using phantom model and experimental circuit with circulating glycerin solution, an equation for the relationship between contrast media intensity and flow rate was developed. Applying the equation to the aneurysm phantom models, the derived flow rate was evaluated. RESULTS: The average errors between the derived flow rate and setting flow rate became larger when the glycerin flow and the X-rays from the X-ray tube of the angiography system were parallel to each other or when the measurement point included overlaps with other contrast enhanced areas. CONCLUSION: Although the error increases dependent on the imaging direction and overlap of contrast enhanced area, the developed equation can estimate the flow rate using the image intensity value measured on 3D-iFlow based on 4D-DSA.