Manual, semiautomated, and fully automated measurement of the aortic annulus for planning of transcatheter aortic valve replacement (TAVR/TAVI): analysis of interchangeability

The Role of Artificial Intelligence in Providing Real-Time Guidance During Interventional Cardiology Procedures: A Narrative Review

Integrating artificial intelligence (AI) in interventional cardiology revolutionizes procedural guidance, particularly in high-stakes environments such as angioplasty and stent placement. In this narrative review we explore the role of AI in providing real-time decision support, enhancing precision, and improving patient outcomes during these complex procedures. AI algorithms can identify critical anatomical features, predict complications, and optimize stent positioning with unprecedented accuracy by analyzing data from imaging modalities like intravascular ultrasound and optical coherence tomography. The findings of this narrative review, from which we have reviewed more than 150 studies across multiple databases, highlight the necessity of continued research and development to utilize AI to its full potential in enhancing the efficacy and safety of interventional procedures. In this review we highlight AI's current advancements, challenges, and potential in real-time interventional cardiology procedures, emphasizing its transformative impact on clinical practice and patient care.

Evolving capabilities of computed tomography imaging for transcatheter valvular heart interventions - new opportunities for precision medicine

The last decade has witnessed a substantial growth in percutaneous treatment options for heart valve disease. The development in these innovative therapies has been mirrored by advances in multi-detector computed tomography (MDCT). MDCT plays a central role in obtaining detailed pre-procedural anatomical information, helping to inform clinical decisions surrounding procedural planning, improve clinical outcomes and prevent potential complications. Improvements in MDCT image acquisition and processing techniques have led to increased application of advanced analytics in routine clinical care. Workflow implementation of patient-specific computational modeling, fluid dynamics, 3D printing, extended reality, extracellular volume mapping and artificial intelligence are shaping the landscape for delivering patient-specific care. This review will provide an insight of key innovations in the field of MDCT for planning transcatheter heart valve interventions.

Reliability of semi-automated spinal measurement software

PURPOSE

In the treatment of patients with adult spinal deformity, analysis of spinopelvic balance is essential in clinical assessment and surgical planning. There is currently no gold standard for measurement, whether done by hand or with digital software. New semi-automated software exists that purports to increase efficiency, but its reliability is unknown in the literature.

METHODS

Full spine X-rays were retrospectively reviewed from 25 adult patients seen between 2014 and 2017. Patients were included if they had > 5 cm of sagittal imbalance and radiographs of sufficient quality to perform balance measurements, without prior surgical spinal fusion and/or instrumentation. Spinopelvic parameters were measured in two radiographic programs: one with basic, non-spine-specific measurement tools (eUnity, Client Outlook, Waterloo, Canada); and a second with spine-specific semi-automated measurement tools (Sectra, Sectra AB, Linköping, Sweden). Balance parameters included SVA, PI, PT, and LL. Data were compared by examining inter-rater and inter-program reliability using interclass correlation coefficient (ICC).

RESULTS

The subjects' mean age was 67.9 ± 13.8 years old, and 32% were male. The inter-program reliability was strong, with ICC values greater than 0.91 for each parameter. Similarly, there was strong inter-observer reliability with ICC values greater than 0.88. These results persisted on delayed repeat measurement (p < 0.001 for all measurements).

CONCLUSION

There is excellent inter-observer and inter-program reliability between the basic PACS and semi-automated programs. These data demonstrate that the purported efficiency of semi-automated measurement programs does not come at the cost of measurement reliability.

Artificial Intelligence in Transcatheter Aortic Valve Replacement: Its Current Role and Ongoing Challenges

Transcatheter aortic valve replacement (TAVR) has emerged as a viable alternative to surgical aortic valve replacement, as accumulating clinical evidence has demonstrated its safety and efficacy. TAVR indications have expanded beyond high-risk or inoperable patients to include intermediate and low-risk patients with severe aortic stenosis. Artificial intelligence (AI) is revolutionizing the field of cardiology, aiding in the interpretation of medical imaging and developing risk models for at-risk individuals and those with cardiac disease. This article explores the growing role of AI in TAVR procedures and assesses its potential impact, with particular focus on its ability to improve patient selection, procedural planning, post-implantation monitoring and contribute to optimized patient outcomes. In addition, current challenges and future directions in AI implementation are highlighted.

Evolving computed tomography angiography for aortic valve replacement: Optimizing transcatheter and surgical therapies

Transcatheter aortic valve replacement (TAVR) has transformed the treatment of aortic stenosis and pre-procedure planning relies heavily on advanced imaging. Multidetector computed tomography angiography, the "TAVR CT," facilitates essential planning steps of measuring the aortic root for valve sizing and feasibility and assessment of potential access vessels, making it the guideline gold standard in preprocedural TAVR work up. This Impact of Advanced Imaging Techniques on Cardiac Surgery article will examine the development of TAVR CT, illustrate the current impact and utility, and highlight potential areas of future growth. Clinicians who keep informed of these changes and can become proficient with TAVR CT analyses will offer patients the most optimal results and fuel future therapeutic growth.

Preoperative TAVR Planning: How to Do It

Transcatheter aortic valve replacement (TAVR) is a well-established treatment option for patients with severe symptomatic aortic stenosis (AS) whose procedural efficacy and safety have been continuously improving. Appropriate preprocedural planning, including aortic valve annulus measurements, transcatheter heart valve choice, and possible procedural complication anticipation is mandatory to a successful procedure. The gold standard for preoperative planning is still to perform a multi-detector computed angiotomography (MDCT), which provides all the information required. Nonetheless, 3D echocardiography and magnet resonance imaging (MRI) are great alternatives for some patients. In this article, we provide an updated comprehensive review, focusing on preoperative TAVR planning and the standard steps required to do it properly.

Potential impact of dynamic automated CT aortic annular measurements on outcomes for transcatheter aortic valve replacement sizing

To determine the potential impact of automated computed tomography (CT) software used for aortic annular sizing for transcatheter aortic valve replacement (TAVR) on paravalvular leak (PVL) and major adverse cardiovascular events (MACE) as compared to standard CT manual measurement. In 60 TAVR patients (84 ± 7 years, 60% male), we evaluated the preprocedural CT scans. For the standard manual measurement, we measured the perimeter and area from a single cardiac phase deemed to be of maximum systolic opening. Valve type and size were determined by a multidisciplinary TAVR team per clinical routine. From the dynamic automated software, we determined the aortic annular perimeter and area as the maximum value from an entire cardiac cycle. Valve size was readjudicated by a blinded interventional cardiologist who was provided with valve type and automated values. Clinical endpoints were adjudicated for presence of at least mild PVL and MACE at 30 days. There were 16 (28%) patients with PVL and 4 (7%) with 30-day MACE. When reclassifying valve size using dynamic automated values, 12 (20%) patients were undersized and 3 (5%) patients were oversized. Undersized patients were more likely to have mild-to-moderate PVL at 30 days (27% vs 4%, p = 0.04) than those not undersized. Of the 5 (45%) undersized patients with at least mild PVL, all were balloon-expandable valves. Automated dynamic CT annular measurements have the potential to reclassify patients with PVL with larger TAVR valve size, particularly balloon-expandable valves.

A fully automated software platform for structural mitral valve analysis

OBJECTIVE

To evaluate a novel fully automated mitral valve analysis software platform for cardiac computer tomography angiography (CCTA)-based structural heart therapy procedure planning.

METHODS

The study included 52 patients (25 women; mean age, 66.9 ± 12.4 years) who had undergone CCTA prior to transcatheter mitral valve replacement (TMVR) or surgical mitral valve intervention (replacement or repair). Therapeutically relevant mitral valve annulus parameters (projected area, circumference, trigone-to-trigone (T-T) distance, anterior-posterior (AP) diameter, and anterolateral-posteromedial (AL-PM) diameter) were measured. Results of the fully automated mitral valve analysis software platform with and without manual adjustments were compared with the reference standard of a user-driven measurement program (3mensio, Pie Medical Imaging). Measurements were compared between the fully automated software, both with and without manual adjustment, and the user-driven program using intraclass correlation coefficients (ICC). A secondary analysis included the time to obtain all measurements.

RESULTS

Fully automated measurements showed a good to excellent agreement (circumference, ICC = 0.70; projected area, ICC = 0.81; T-T distance, ICC = 0.64; AP, ICC = 0.62; and AL-PM diameter, ICC = 0.78) compared with the user-driven analysis. There was an excellent agreement between fully automated measurement with manual adjustments and user-driven analysis regarding circumference (ICC = 0.91), projected area (ICC = 0.93), T-T distance (ICC = 0.80), AP (ICC = 0.78), and AL-PM diameter (ICC = 0.79). The time required for mitral valve analysis was significantly lower using the fully automated software with manual adjustments compared with the standard assessment (134.4 ± 36.4 s vs. 304.3 ± 77.7 s) (p < 0.01).

CONCLUSION

The fully automated mitral valve analysis software, when combined with manual adjustments, demonstrated a strong correlation compared with the user-driven software while reducing the total time required for measurement.

KEY POINTS

• The novel software platform allows for a fully automated analysis of mitral valve structures. • An excellent agreement was found between the fully automated measurement with manual adjustments and the user-driven analysis. • The software showed quicker measurement time compared with the standard analysis of the mitral valve.

Validation of a Novel Software Tool for Automatic Aortic Annular Sizing in Three-Dimensional Transesophageal Echocardiographic Images

BACKGROUND

Accurate aortic annulus (AoA) sizing is crucial for transcatheter aortic valve implantation planning. Three-dimensional (3D) transesophageal echocardiography (TEE) is a viable alternative to the standard multidetector row computed tomography (MDCT) for such assessment, with few automatic software solutions available. The aim of this study was to present and evaluate a novel software tool for automatic AoA sizing by 3D TEE.

METHODS

One hundred one patients who underwent both preoperative MDCT and 3D TEE were retrospectively analyzed using the software. The automatic software measurements' accuracy was compared against values obtained using standard manual MDCT, as well as against those obtained using manual 3D TEE, and intraobserver, interobserver, and test-retest reproducibility was assessed. Because the software can be used as a fully automatic or as an interactive tool, both options were addressed and contrasted. The impact of these measures on the recommended prosthesis size was then evaluated to assess if the software's automated sizes were concordant with those obtained using an MDCT- or a TEE-based manual sizing strategy.

RESULTS

The software showed very good agreement with manual values obtained using MDCT and 3D TEE, with the interactive approach having slightly narrower limits of agreement. The latter also had excellent intra- and interobserver variability. Both fully automatic and interactive analyses showed excellent test-retest reproducibility, with the first having a faster analysis time. Finally, either approach led to good sizing agreement against the true implanted sizes (>77%) and against MDCT-based sizes (>88%).

CONCLUSIONS

Given the automated, reproducible, and fast nature of its analyses, the novel software tool presented here may potentially facilitate and thus increase the use of 3D TEE for preoperative transcatheter aortic valve implantation sizing.

Performance of Dynamic Automated CT Annular Measurements Compared to Standard Manual Measurements for Transcatheter Aortic Valve Replacement Sizing

Purpose

We sought to determine the performance of an automated computed tomography (CT) software that provides dynamic annular measurements of all available cardiac phases for transcatheter aortic valve replacement (TAVR) sizing as compared to the standard single manual measurement.

Materials and Methods

In 60 TAVR patients (84±7 years, 60% male) who underwent pre-procedural CT scans, we measured the aortic annular diameters, perimeter, and area using (1) the dynamic automated CT measurements and (2) standard single manual measurement from the cardiac phase of maximum systolic opening by visual estimate.

Results

The automated software was successful in providing annular measurements in 43/60 (72%) of cases, with the remainder requiring semi-automated contours. The maximum dynamic automated values were predominantly in systole (46/60[77%] for diameter, 44/60[73%] for perimeter, 48/60[80%] for area), and was a different phase from the standard manual phase in 46/60 (77%) cases. The maximum dynamic automated annular values were larger than the standard manual values measured (Δdiameter 0.35 mm, p=0.04; Δperimeter 1.71 mm, p<0.001; Δarea 15.6 mm², p<0.001). When comparing standard manual to the same phase by automated measurements, while there was no difference in annular mean diameter (p=0.80), perimeter and area were larger with the automated measurements (Δperimeter 0.95 mm, p=0.002; Δarea 10.8 mm², p=0.03). However, the maximum automated measurements were consistently larger than the same phase automated measurements (Δdiameter 0.13 mm, p<0.001; Δperimeter 0.42 mm, p<0.001; Δarea 4.4 mm², p<0.001).

Conclusions

Automated maximum dynamic CT annular measurements provide larger values than standard manual and same phase automated measurements.

Performance of Dynamic Automated CT Annular Measurements Compared to Standard Manual Measurements for Transcatheter Aortic Valve Replacement Sizing

PURPOSE

We sought to determine the performance of an automated computed tomography (CT) software that provides dynamic annular measurements of all available cardiac phases for transcatheter aortic valve replacement (TAVR) sizing as compared to the standard single manual measurement.

MATERIALS AND METHODS

In 60 TAVR patients (84±7 years, 60% male) who underwent pre-procedural CT scans, we measured the aortic annular diameters, perimeter, and area using (1) the dynamic automated CT measurements and (2) standard single manual measurement from the cardiac phase of maximum systolic opening by visual estimate.

RESULTS

The automated software was successful in providing annular measurements in 43/60 (72%) of cases, with the remainder requiring semi-automated contours. The maximum dynamic automated values were predominantly in systole (46/60[77%] for diameter, 44/60[73%] for perimeter, 48/60[80%] for area), and was a different phase from the standard manual phase in 46/60 (77%) cases. The maximum dynamic automated annular values were larger than the standard manual values measured (Δdiameter 0.35 mm, p=0.04; Δperimeter 1.71 mm, p<0.001; Δarea 15.6 mm², p<0.001). When comparing standard manual to the same phase by automated measurements, while there was no difference in annular mean diameter (p=0.80), perimeter and area were larger with the automated measurements (Δperimeter 0.95 mm, p=0.002; Δarea 10.8 mm², p=0.03). However, the maximum automated measurements were consistently larger than the same phase automated measurements (Δdiameter 0.13 mm, p<0.001; Δperimeter 0.42 mm, p<0.001; Δarea 4.4 mm², p<0.001).

CONCLUSIONS

Automated maximum dynamic CT annular measurements provide larger values than standard manual and same phase automated measurements.

[Evolution of transcatheter aortic valve implantation: from planning to robotic systems]

Since its introduction in 2002, transcatheter aortic valve implantation (TAVI) has evolved dramatically and is now standard of care for intermediate risk patients with aortic stenosis. The development of innovative transcatheter heart valves and refinement of technical skills have contributed to the decrease in complication rates associated with TAVI. Increased experience, smaller sheaths, rigorous pre-procedural planning and improved vascular closing techniques have resulted in markedly lower rates of vascular complications. The next step was the simplification of the procedure, which contributed to a further decrease in complications, reduced procedural time, and shorter hospital stay. Change-over from general anaesthesia to conscious sedation, refusal from predilatation, and use of the radial approach instead of the contralateral femoral approach are all instrumental in achieving optimal results. Prospects for development include visual assist systems and robotic systems that can potentially optimize the transcatheter aortic valve implantation process, improve safety and effectiveness of the procedure.

CT support of cardiac structural interventions

Due to its high temporal and isotropic spatial resolution, CT has become firmly established for pre-procedural imaging in the context of structural heart disease interventions. CT allows to very exactly measure dimensions of the target structure, CT can provide information regarding the access route and, as a very valuable addition, volumetric CT data sets can be used to identify fluoroscopic projection angulations to optimally visualize the target structure and place devices. This review provides an overview of current methods and applications of pre-interventional CT to support adult cardiac interventions including transcatheter aortic valve implantation, percutaneous mitral valve intervention, left atrial appendage occlusion and paravalvular leak closure.

Inter- and intra-observer repeatability of aortic annulus measurements on screening CT for transcatheter aortic valve replacement (TAVR): Implications for appropriate device sizing

OBJECTIVES

To investigate intra- and inter-observer repeatability of aortic annulus CT measurements for transcatheter aortic valve replacement (TAVR) by readers with different levels of experience and evaluate the impact of different multi-reader paradigms to improve prosthesis sizing.

METHODS

82 TAVR screening CTAs were evaluated twice by three raters with six (R1 = radiologist), three (R2 = 3D-laboratory technician) or zero (R3 = medical student) years of experience. Results were translated into hypothetical TAVR size recommendations. Intra- and inter-observer repeatability between single readers and three different multi-reader paradigms ([A]: two readers, [B]: three readers, or [C]: two readers + an optional third reader) were evaluated.

RESULTS

Intra-observer variability did not differ significantly (range: 50.1-67.8mm2). However, we found significant differences in mean inter-observer variance (p = 0.001). Multi-reader paradigms led to significantly increased precision (lower variability) for scenarios [B] and [C] (p = 0.03, p < 0.05). Compared to single readers, all multi-reader strategies clearly lowered the rate of discrepant device size categorization between repeated measurements (22-26% to 5-10%).

CONCLUSIONS

Aortic annulus CT measurements for TAVR are highly reproducible. Multi-reader strategies provide higher precision than evaluations from single readers with different levels of experience and could effectively be implemented with two readers and an optional third reader (Paradigm C) in a clinical setting.

Aortic root evaluation prior to transcatheter aortic valve implantation-Correlation of manual and semi-automatic measurements

Background

Pre-procedural TAVI planning requires highly sophisticated and time-consuming manual measurements performed by experienced readers. Semi-automatic software may assist with partial automation of assessment of multiple parameters. The aim of this study was to evaluate differences between manual and semi-automatic measurements in terms of agreement and time.

Methods

One hundred and twenty TAVI candidates referred for the retrospectively ECG-gated CTA (2^nd and 3^rd generation dual source CT) were evaluated. Fully manual and semi-automatic measurements of fourteen aortic root parameters were assessed in the 20% phase of the R-R interval. Reading time was compared using paired samples t-test. Inter-software agreement was calculated using the Intraclass correlation coefficient (ICC) in a 2-way mixed effects model. Differences between manual and semi-automatic measurements were evaluated using Bland-Altman analysis.

Results

The time needed for evaluation using semi-automatic assessment (3 min 24 s ± 1 min 7 s) was significantly lower (p<0.001) compared to a fully manual approach (6 min 31 sec ± 1 min 1 sec). Excellent inter-software agreement was found (ICC = 0.93 ± 0.0; range:0.90–0.95).

The same prosthesis size from manual and semi-automatic measurements was selected in 92% of cases, when sizing was based on annular area. Prosthesis sizing based on annular short diameter and perimeter agreed in 99% and 96% cases, respectively.

Conclusion

Use of semi-automatic software in pre-TAVI evaluation results in comparable results in respect of measurements and selected valve prosthesis size, while necessary reading time is significantly lower.

Semi-automatic CT-angiography based evaluation of the aortic annulus in patients prior to TAVR: interchangeability with manual measurements

To compare a semi-automatic software tool for the measurement of aortic annulus dimensions with manual measurements by expert readers and to analyze whether and to what extent interchangeability exists between semi-automatic and manual measurements. We retrospectively included 374 consecutive patients with high-grade aortic stenosis who had undergone CT-angiography of the heart prior to trans-catheter aortic valve replacement (TAVR). In independent analyses, two expert readers manually measured aortic annulus dimensions (long axis, short axis, circumference, area) as well as the distance of the coronary ostia from the annulus plane. A third independent reader performed annulus evaluation using a software tool for semi-automatic detection and measurement of the annulus plane. Intraclass correlation coefficients (ICC) and Bland-Altman analysis was used to compare both manual measurements as well as manual and semi-automatic measurements of annulus parameters. Using the respective measurements we simulated size selection for a Sapien XT transcatheter heart valve (THV). Interchangeability of methods was addressed by calculation of the estimated individual equivalence index γ. There was excellent agreement between both expert observers in manual measurements of the annulus with ICC's in the range 0.89-0.94 for all anatomic parameters. Similar high agreements were observed between semi-automatic and manual measurements, with ICC's in the range of 0.89-0.95. THV size recommendation based on manual versus semiautomatic measurements agreed in 80.7% of cases while agreement between both expert readers concerning THV size recommendation was 80.6%. Semi-automatic measurements of anatomic parameters of the aortic root show high agreement and interchangeability with manual measurements in CT-angiography prior to TAVR.

Multi-slice CT (MSCT) imaging in pretrans-catheter aortic valve implantation (TAVI) screening. How to perform and how to interpret

Aortic valve stenosis (AS) is the most common valvular heart disease among elderly. Trans-catheter aortic valve implantation (TAVI) has become an established and effective alternative therapeutical procedure for inoperable and high-risk patients with symptomatic AS. The procedural success is greatly dependent on a thorough pre-TAVI imaging screening. This requires a comprehensive and multi-modality approach, in which multi-slice computed tomography (MSCT) is the cornerstone in the selection of eligible patients, in choosing the appropriate prosthesis and size, and in mapping the safest access route for the intervention. From our experience of more than 400 TAVI procedures and many more MSCTs for screening purposes, we provide clinical and technical details on the use of MSCT pre-TAVI and brief review of the knowledge so far.

Virtual medicine: Utilization of the advanced cardiac imaging patient avatar for procedural planning and facilitation

Advances in imaging technology have led to a paradigm shift from planning of cardiovascular procedures and surgeries requiring the actual patient in a "brick and mortar" hospital to utilization of the digitalized patient in the virtual hospital. Cardiovascular computed tomographic angiography (CCTA) and cardiovascular magnetic resonance (CMR) digitalized 3-D patient representation of individual patient anatomy and physiology serves as an avatar allowing for virtual delineation of the most optimal approaches to cardiovascular procedures and surgeries prior to actual hospitalization. Pre-hospitalization reconstruction and analysis of anatomy and pathophysiology previously only accessible during the actual procedure could potentially limit the intrinsic risks related to time in the operating room, cardiac procedural laboratory and overall hospital environment. Although applications are specific to areas of cardiovascular specialty focus, there are unifying themes related to the utilization of technologies. The virtual patient avatar computer can also be used for procedural planning, computational modeling of anatomy, simulation of predicted therapeutic result, printing of 3-D models, and augmentation of real time procedural performance. Examples of the above techniques are at various stages of development for application to the spectrum of cardiovascular disease processes, including percutaneous, surgical and hybrid minimally invasive interventions. A multidisciplinary approach within medicine and engineering is necessary for creation of robust algorithms for maximal utilization of the virtual patient avatar in the digital medical center. Utilization of the virtual advanced cardiac imaging patient avatar will play an important role in the virtual health care system. Although there has been a rapid proliferation of early data, advanced imaging applications require further assessment and validation of accuracy, reproducibility, standardization, safety, efficacy, quality, cost effectiveness, and overall value to medical care.

Quantification of aortic annulus in computed tomography angiography: Validation of a fully automatic methodology

BACKGROUND

Automatic accurate measuring of the aortic annulus and determination of the optimal angulation of X-ray projection are important for the trans-catheter aortic valve replacement (TAVR) procedure. The objective of this study was to present a novel fully automatic methodology for the quantification of the aortic annulus in computed tomography angiography (CTA) images.

METHODS

CTA datasets of 26 patients were analyzed retrospectively with the proposed methodology, which consists of a knowledge-based segmentation of the aortic root and detection of the orientation and size of the aortic annulus. The accuracy of the methodology was determined by comparing the automatically derived results with the reference standard obtained by semi-automatic delineation of the aortic root and manual definition of the annulus plane.

RESULTS

The difference between the automatic annulus diameter and the reference standard by observer 1 was 0.2±1.0mm, with an inter-observer variability of 1.2±0.6mm. The Pearson correlation coefficient for the diameter was good (0.92 for observer 1). For the first time, a fully automatic tool to assess the optimal projection curves was presented and validated. The mean difference between the optimal projection curves calculated based on the automatically defined annulus plane and the reference standard was 6.4° in the cranial/caudal (CRA/CAU) direction. The mean computation time was short with around 60s per dataset.

CONCLUSION

The new fully automatic and fast methodology described in this manuscript not only provided precise measurements about the aortic annulus size with results comparable to experienced observers, but also predicted optimal X-ray projection curves from CTA images.

Computer-aided evaluation of low-dose and low-contrast agent third-generation dual-source CT angiography prior to transcatheter aortic valve implantation (TAVI)

PURPOSE

To evaluate the performance of computer-aided evaluation software for a comprehensive workup of patients prior to transcatheter aortic valve implantation (TAVI) using low-contrast agent and low radiation dose third-generation dual-source CT angiography.

METHODS

We evaluated 30 consecutive patients scheduled for TAVI. All patients underwent ECG-triggered high-pitch dual-source CT angiography of the aortic root and aorta with a standardized contrast agent volume (30 ml Imeron350, flow rate 4 ml/s) and low-dose (100 kv/350 mAs) protocol. An expert (10 years of experience) manually evaluated aortic root and iliac access dimensions (distance between coronary ostia and aortic annulus, minimal/maximal diameters and area-derived diameter of the aortic annulus) and best CT-predicted fluoroscopic projection angle as the reference standard. Utilizing computer-aided software (syngo.via), the same pre-TAVI workup was performed and compared to the reference standard.

RESULTS

Mean CTDI[Formula: see text] was 3.46 mGy and mean DLP 217.6 ± 12.1 mGy cm, corresponding to a mean effective dose of 3.7 ± 0.2 mSv. Computer-aided evaluation was successful in all but one patient. Compared to the reference standard, Bland-Altman analysis indicated very good agreement for the distances between aortic annulus and coronary ostia (RCA: mean difference 0.8 mm; 95 % CI 0.4-1.2 mm; LM: mean difference 0.9 mm; 95 % CI 0.5-1.3 mm); however, we demonstrated a systematic overestimation of annulus- derived diameter using the software (mean difference 44.4 mm[Formula: see text]; 95 % CI 30.4-58.3 mm[Formula: see text]). Based on respective annulus dimensions, the recommended prosthesis size (Edwards SAPIEN 3) matched in 26 out of the 29 patients (90 %). CT-derived fluoroscopic projection angles showed an excellent agreement for both methods. Out of 58 iliac arteries, 15 (25 %) arteries could not be segmented by the software. Preprocessing time of the software was 71 ± 11 s (range 51-96 s), and reading time with the software was 118 ± 31 s (range 68-201 s).

CONCLUSION

In the workup of pre-TAVI CT angiography, computer-aided evaluation of low-contrast, low-dose examinations is feasible with good agreement and quick reading time. However, a systematic overestimation of the aortic annulus area is observed.

Relationship of mitral valve annulus plane and circumflex-right coronary artery plane: Implications for Transcatheter Mitral Valve Implantation

AIM

Transcatheter mitral valve implantation (TMVI) is a novel technology for patients with severe mitral valve disease but at high surgical risk. Imaging guidance during the procedure is critical for successful device deployment. Identification of the mitral annular plane (MAP) with fluoroscopy during the procedure is limited by lack of clearly defined landmarks. We hypothesized that a plane defined by left circumflex-right coronary arteries (LCX-RCA) would have a consistent relationship to MAP.

METHODS AND RESULTS

We studied 25 patients with gated cardiac computed tomography. We identified the MAP and the LCX-RCA plane in mid systole and diastole. The distance between the two planes in prespecified four points (anterior, posterior, medial, and lateral) in the apical 2 and 3-chamber views. Alignment of the planes was described by cranial/caudal angulation for both planes in RAO 30° and LAO 90° (lateral) angulation. Mean age was 81 ± 9 years, 56% of patients had ≥2+ mitral regurgitation. In mid systole, the distances between the LCX-RCA plane and the MAP in the four points were < 5 mm in 92% of patients. In mid diastole, distances were < 5 mm in 100% of patients. In mid systole, the correlation between the caudal/cranial orientations of the 2 planes was 0.85 and 0.80 in the LAO 90° and RAO 30°, respectively (P = <0.001). In mid diastole, this was 0.92 and 0.92 in the LAO 90° and RAO 30°, respectively (P = <0.001).

CONCLUSION

LCX-RCA plane has a close and consistent relationship to the MAP and can be useful to guide TMVI. Accurate imaging of mitral valve annular plane during TMVI procedure is challenging. MAP guided by fluoroscopy might be crucial to guide successful prosthesis deployment. A plane defined by the left circumflex- right coronary arteries in the atrioventricular grove has a consistent relationship with MAP; this can be used aided by pre-procedural MDCT to guide TMVI procedure. © 2016 Wiley Periodicals, Inc.

Comparison of Manual and Automated Preprocedural Segmentation Tools to Predict the Annulus Plane Angulation and C-Arm Positioning for Transcatheter Aortic Valve Replacement

Background

Preprocedural manual multi-slice-CT-segmentation tools (MSCT-ST) define the gold standard for planning transcatheter aortic valve replacement (TAVR). They are able to predict the perpendicular line of the aortic annulus (PPL) and to indicate the corresponding C-arm angulation (CAA). Fully automated planning-tools and their clinical relevance have not been systematically evaluated in a real world setting so far.

Methods and Results

The study population consists of an all-comers cohort of 160 consecutive TAVR patients with a drop out of 35 patients for technical and anatomical reasons. 125 TAVR patients underwent preprocedural analysis by manual (M-MSCT) and fully automated MSCT-ST (A-MSCT). Method-comparison was performed for 105 patients (Cohort A). In Cohort A, CAA was defined for each patient, and accordance within 10° between M-MSCT and A-MSCT was considered adequate for concept-proof (95% in LAO/RAO; 94% in CRAN/CAUD). Intraprocedural CAA was defined by repetitive angiograms without utilizing the preprocedural measurements. In Cohort B, intraprocedural CAA was established with the use of A-MSCT (20 patients). Using preprocedural A-MSCT to indicate the corresponding CAA, the levels of contrast medium (ml) and radiation exposure (cine runs) were reduced in Cohort B compared to Cohort A significantly (23.3±10.3 vs. 35.3 ±21.1 ml, p = 0.02; 1.6±0.7 vs. 2.4±1.4 cine runs; p = 0.02) and trends towards more safety in valve-positioning could be demonstrated.

Conclusions

A-MSCT-analysis provides precise preprocedural information on CAA for optimal visualization of the aortic annulus compared to the M-MSCT gold standard. Intraprocedural application of this information during TAVR significantly reduces the levels of contrast and radiation exposure.

Trial Registration

ClinicalTrials.gov NCT01805739

Metrology Standards for Quantitative Imaging Biomarkers

Although investigators in the imaging community have been active in developing and evaluating quantitative imaging biomarkers (QIBs), the development and implementation of QIBs have been hampered by the inconsistent or incorrect use of terminology or methods for technical performance and statistical concepts. Technical performance is an assessment of how a test performs in reference objects or subjects under controlled conditions. In this article, some of the relevant statistical concepts are reviewed, methods that can be used for evaluating and comparing QIBs are described, and some of the technical performance issues related to imaging biomarkers are discussed. More consistent and correct use of terminology and study design principles will improve clinical research, advance regulatory science, and foster better care for patients who undergo imaging studies.