Catheterization and Cardiovascular Interventions 85:148 (2015)
Editorial Comment Fluoroscopy and CT Fusion Overlay—Greater Than the Sum of Their Parts Marvin H. Eng,1* MD, and Michael S. Kim,2 MD 1 Department of Medicine, Division of Cardiology, University of Texas Health Sciences Center, San Antonio, Texas 2 Department of Medicine, Division of Cardiology, University of Colorado Health Sciences Center, Aurora, Colorado
Key Points
Krishnaswamy et al.’s study implements fusion of patient computed tomography (CT) three dimensional (3D)- imaging dataset with fluoroscopy to create a superimposed phantom roadmap as an aid to structural interventions. The study is primarily a feasibility and methods manuscript describing how to perform noninvasive CT registration and fusion with the on-table X-ray images. Although innovative, the study does not add insight to how CT-fusion improves the safety or efficacy of structural interventions.
In this edition of CCI, Krishnaswamy et al. describe their initial experience of using multi-detector computed tomography (MDCT)/fluoroscopy coregistration and overlay to guide complex structural heart disease and coronary interventions. Their preliminary work represents a sterling example of both leveraging and incorporating the inherent benefits of MDCT datasets into the procedural arena to optimize clinical outcomes. Although the prospective cohort analysis aims to offer a description of technological feasibility, it offers the truly added benefit of providing a framework on which future technology aimed at enhancing safety and efficiency of complex invasive procedures can be developed. Although the pioneering work in MDCT/fluoroscopy fusion and overlay was originally performed in rare cases of exceptionally complex anatomy, Krishnaswamy et al.’s experience in image fusion technology has the potential to pave C 2014 Wiley Periodicals, Inc. V
the way toward use across a much broader spectrum of interventions [1]. With the advent and wide adoption of more complex structural heart disease interventions (e.g., Transcatheter aortic valve replacement (TAVR), percutaneous mitral valve repair, paravalvular leak closure, etc.), the careful analysis and understanding of various 3D imaging data sets (3D echocardiography, magnetic resonance imaging (MRI), MDCT) have become a near obligatory aspect of both preprocedural evaluation and intraprocedural guidance. For example, use of preprocedural MDCT is particularly valuable for optimally orienting fluoroscopic C-arm gantry angles [2]. Additional, creation of physical (i.e., rapid prototyping) from MDCT and MRI datasets provides unique prospective in planning structural interventions [3] and is becoming more commonplace technological application in the cardiovascular field. As a result of such advancements in 3D imaging applications, most structural heart interventionalists have been thrust into a realm whereby their clinical skillsets are not only blending with those of cardiothoracic surgeons but are also blurring into the world of radiology. As the authors point out, interventionalists are already become facile with MDCT based preprocedural planning of prosthesis sizing for TAVR, and the more widespread adoption of using MDCT in the procedural arena with the correlative necessity of “on-the-fly” imaging processing by the interventionalists represents a frontier that is very close to becoming reality. Nonetheless, while Krishnaswamy et al. demonstrate particular cases where MDCT/fluoroscopy fusion has helped, their work still falls short in proving the hypothesis that adjunctive imaging tools enhance procedural guidance. This shortcoming is by no means a reflection of their excellent work but more so of the fact that such a hypothesis has historically been very challenging to prove as the very nature of quantifying Conflict of interest: Nothing to report. *Correspondence to: Marvin H. Eng, MD, University of Texas Health Sciences Center, San Antonio, TX. E-mail: [email protected] Received 10 November 2014; Revision accepted 12 November 2014 DOI: 10.1002/ccd.25741 Published online 18 December 2014 in Wiley Online Library (wileyonlinelibrary.com)
Fluoroscopy and CT Fusion Overlay
assistance from imaging tools is difficult. Using the subjective value of improved confidence in device delivery and deployment oftentimes does not meet a high scientific bar. Thus, proving such a hypothesis requires the analysis of surrogate metrics such as, procedure time or radiation exposure, though ultimately cannot account for variables such as, operator learning curve or marked variability in anatomic pathology. A prior study examining procedure guidance using realtime 3D transesophageal echocardiography (RT 3DTEE) for mitral balloon valvuloplasty was associated with decreased radiation exposure shows promise for scientifically verifying the benefits of advanced image guidance, but prospective studies are lacking [4]. One limitation to the demonstrated fusion technology revolves around a minor, yet fundamental difference in body positioning on the CT bed versus the catheterization lab table. The CT bed is concave across the width of the body which serves to cradle the body while the patient is complete flat on the procedure table. Although these minor positioning changes can oftentimes be overcome by registering predictable anatomical structures or objects (e.g., bioprosthetic valve frames, trachea, and spine), dynamic changes in heart position during to respiratory motion is impossible to account and correct for in the MDCT fusion technology demonstrated here. Moreover, realtime movements of soft tissue cardiac structures such as chordae or valves will not appear on the fused overlay projection. Thus, what is presented on the fluoroscopy screen represents a rough outlined roadmap of the structures of interest rather than a precise, detailed navigation map. Many of these limitations can be overcome with coregistration of RT 3D-TEE with fluoroscopy to provide “live” intraprocedural imaging guidance [5]. Despite its inherent disadvantages (patient comfort, potential need for general anesthesia, suboptimal visualization of particular wires and catheters, etc.), RT 3D-TEE offers the advantage of enhanced soft tissue quantification and blood flow
149
assessment without the use of contrast making it an ideal imaging modality to guide complex structural heart interventions. Merging a RT 3D-TEE dataset with fluoroscopy may ultimately represent the best combination of imaging modalities to date with the added benefit of potentially further reducing radiation exposure, a boon to both patients and interventionalists. Of course, the imaging fusion tools mentioned are magnificent to have available and may very well represent the next frontier in image guidance, though the fundamental knowledge and technical skill of the interventionalist remain the most indispensible of tools. Not every procedural suite will have access to such advanced technologies as justification of the cost may ultimately represents the biggest of all hurdle against widespread adoption and utilization. Just as well, CT fusion overlay represents yet another iterative advancement in the application of advanced imaging technology aimed at achieving the goal of enhanced procedural safety and efficacy. REFERENCES 1. Garcia JA, Bhakta S, Kay J, Chan KC, Wink O, et al. On-line multi-slice computed tomography interactive overlay with conventional X-Ray: a new and advanced imaging fusion concept. Int J Cardiol 2009;133:e101–e105. 2. Theriault-Lauzier P, Andalib A, Martucci G, Mylotte D, Cecere R, et al. Flouroscopic anatomy of left-sided heart structures for transcatheter interventions insight from multislice computed tomography. JACC Cardiovasc Interv 2014;7:947–957. 3. Kim MS, Hansgen AR, Wink O, Quaife RA, Carroll JD. Rapid prototyping: A new tool in understanding and treating structural heart disease. Circulation 2008;117:2388–2394. 4. Eng MH, Salcedo EE, Kim M, Quaife RA, Carroll JD. Implementation of real-time three-dimensional transesophageal echocardiography for mitral balloon valvuloplasty. Catheter Cardiovasc Interv 2013;82:994–998. 5. Kim MS, Bracken J, Nijhof N, Salcedo EE, Quaife RA, et al. Integrated 3D Echo-X-Ray navigation to predict optimal angiographic deployment projections for TAVR. JACC Cardiovasc Imaging 2014;7:847–848.
Catheterization and Cardiovascular Interventions DOI 10.1002/ccd. Published on behalf of The Society for Cardiovascular Angiography and Interventions (SCAI).
Editorial Comment Fluoroscopy and CT Fusion Overlay—Greater Than the Sum of Their Parts Marvin H. Eng,1* MD, and Michael S. Kim,2 MD 1 Department of Medicine, Division of Cardiology, University of Texas Health Sciences Center, San Antonio, Texas 2 Department of Medicine, Division of Cardiology, University of Colorado Health Sciences Center, Aurora, Colorado
Key Points
Krishnaswamy et al.’s study implements fusion of patient computed tomography (CT) three dimensional (3D)- imaging dataset with fluoroscopy to create a superimposed phantom roadmap as an aid to structural interventions. The study is primarily a feasibility and methods manuscript describing how to perform noninvasive CT registration and fusion with the on-table X-ray images. Although innovative, the study does not add insight to how CT-fusion improves the safety or efficacy of structural interventions.
In this edition of CCI, Krishnaswamy et al. describe their initial experience of using multi-detector computed tomography (MDCT)/fluoroscopy coregistration and overlay to guide complex structural heart disease and coronary interventions. Their preliminary work represents a sterling example of both leveraging and incorporating the inherent benefits of MDCT datasets into the procedural arena to optimize clinical outcomes. Although the prospective cohort analysis aims to offer a description of technological feasibility, it offers the truly added benefit of providing a framework on which future technology aimed at enhancing safety and efficiency of complex invasive procedures can be developed. Although the pioneering work in MDCT/fluoroscopy fusion and overlay was originally performed in rare cases of exceptionally complex anatomy, Krishnaswamy et al.’s experience in image fusion technology has the potential to pave C 2014 Wiley Periodicals, Inc. V
the way toward use across a much broader spectrum of interventions [1]. With the advent and wide adoption of more complex structural heart disease interventions (e.g., Transcatheter aortic valve replacement (TAVR), percutaneous mitral valve repair, paravalvular leak closure, etc.), the careful analysis and understanding of various 3D imaging data sets (3D echocardiography, magnetic resonance imaging (MRI), MDCT) have become a near obligatory aspect of both preprocedural evaluation and intraprocedural guidance. For example, use of preprocedural MDCT is particularly valuable for optimally orienting fluoroscopic C-arm gantry angles [2]. Additional, creation of physical (i.e., rapid prototyping) from MDCT and MRI datasets provides unique prospective in planning structural interventions [3] and is becoming more commonplace technological application in the cardiovascular field. As a result of such advancements in 3D imaging applications, most structural heart interventionalists have been thrust into a realm whereby their clinical skillsets are not only blending with those of cardiothoracic surgeons but are also blurring into the world of radiology. As the authors point out, interventionalists are already become facile with MDCT based preprocedural planning of prosthesis sizing for TAVR, and the more widespread adoption of using MDCT in the procedural arena with the correlative necessity of “on-the-fly” imaging processing by the interventionalists represents a frontier that is very close to becoming reality. Nonetheless, while Krishnaswamy et al. demonstrate particular cases where MDCT/fluoroscopy fusion has helped, their work still falls short in proving the hypothesis that adjunctive imaging tools enhance procedural guidance. This shortcoming is by no means a reflection of their excellent work but more so of the fact that such a hypothesis has historically been very challenging to prove as the very nature of quantifying Conflict of interest: Nothing to report. *Correspondence to: Marvin H. Eng, MD, University of Texas Health Sciences Center, San Antonio, TX. E-mail: [email protected] Received 10 November 2014; Revision accepted 12 November 2014 DOI: 10.1002/ccd.25741 Published online 18 December 2014 in Wiley Online Library (wileyonlinelibrary.com)
Fluoroscopy and CT Fusion Overlay
assistance from imaging tools is difficult. Using the subjective value of improved confidence in device delivery and deployment oftentimes does not meet a high scientific bar. Thus, proving such a hypothesis requires the analysis of surrogate metrics such as, procedure time or radiation exposure, though ultimately cannot account for variables such as, operator learning curve or marked variability in anatomic pathology. A prior study examining procedure guidance using realtime 3D transesophageal echocardiography (RT 3DTEE) for mitral balloon valvuloplasty was associated with decreased radiation exposure shows promise for scientifically verifying the benefits of advanced image guidance, but prospective studies are lacking [4]. One limitation to the demonstrated fusion technology revolves around a minor, yet fundamental difference in body positioning on the CT bed versus the catheterization lab table. The CT bed is concave across the width of the body which serves to cradle the body while the patient is complete flat on the procedure table. Although these minor positioning changes can oftentimes be overcome by registering predictable anatomical structures or objects (e.g., bioprosthetic valve frames, trachea, and spine), dynamic changes in heart position during to respiratory motion is impossible to account and correct for in the MDCT fusion technology demonstrated here. Moreover, realtime movements of soft tissue cardiac structures such as chordae or valves will not appear on the fused overlay projection. Thus, what is presented on the fluoroscopy screen represents a rough outlined roadmap of the structures of interest rather than a precise, detailed navigation map. Many of these limitations can be overcome with coregistration of RT 3D-TEE with fluoroscopy to provide “live” intraprocedural imaging guidance [5]. Despite its inherent disadvantages (patient comfort, potential need for general anesthesia, suboptimal visualization of particular wires and catheters, etc.), RT 3D-TEE offers the advantage of enhanced soft tissue quantification and blood flow
149
assessment without the use of contrast making it an ideal imaging modality to guide complex structural heart interventions. Merging a RT 3D-TEE dataset with fluoroscopy may ultimately represent the best combination of imaging modalities to date with the added benefit of potentially further reducing radiation exposure, a boon to both patients and interventionalists. Of course, the imaging fusion tools mentioned are magnificent to have available and may very well represent the next frontier in image guidance, though the fundamental knowledge and technical skill of the interventionalist remain the most indispensible of tools. Not every procedural suite will have access to such advanced technologies as justification of the cost may ultimately represents the biggest of all hurdle against widespread adoption and utilization. Just as well, CT fusion overlay represents yet another iterative advancement in the application of advanced imaging technology aimed at achieving the goal of enhanced procedural safety and efficacy. REFERENCES 1. Garcia JA, Bhakta S, Kay J, Chan KC, Wink O, et al. On-line multi-slice computed tomography interactive overlay with conventional X-Ray: a new and advanced imaging fusion concept. Int J Cardiol 2009;133:e101–e105. 2. Theriault-Lauzier P, Andalib A, Martucci G, Mylotte D, Cecere R, et al. Flouroscopic anatomy of left-sided heart structures for transcatheter interventions insight from multislice computed tomography. JACC Cardiovasc Interv 2014;7:947–957. 3. Kim MS, Hansgen AR, Wink O, Quaife RA, Carroll JD. Rapid prototyping: A new tool in understanding and treating structural heart disease. Circulation 2008;117:2388–2394. 4. Eng MH, Salcedo EE, Kim M, Quaife RA, Carroll JD. Implementation of real-time three-dimensional transesophageal echocardiography for mitral balloon valvuloplasty. Catheter Cardiovasc Interv 2013;82:994–998. 5. Kim MS, Bracken J, Nijhof N, Salcedo EE, Quaife RA, et al. Integrated 3D Echo-X-Ray navigation to predict optimal angiographic deployment projections for TAVR. JACC Cardiovasc Imaging 2014;7:847–848.
Catheterization and Cardiovascular Interventions DOI 10.1002/ccd. Published on behalf of The Society for Cardiovascular Angiography and Interventions (SCAI).
