MRI

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PET or MRI, that is the question – Part 2

Moss Zhao, PhD

In our previous blogs, we discussed ASL MRI to image abnormal blood vessels in Moyamoya patients. We looked at a study that compared MRI and PET images of normal and healthy people. In this blog, we will look at the application of ASL MRI on adult Moyamoya patients.

According to the latest study by Dr. Moss Zhao (AHA Postdoctoral Fellow, 2021), ASL MRI can detect impaired blood flow and circulation in Moyamoya patients without any radiation or contrast agents.

In this study, Dr. Zhao’s team enrolled nearly 30 adult Moyamoya patients without acute stroke or tissue infarcts in the brain. They scanned the brain of these patients using the advanced ASL MRI technique (multi-delay ASL) that were tested successfully on normal and healthy people before. Similar to the study designed in the previous blog, Dr. Zhao’s team collected both ASL and PET images from the Moyamoya patients at the same time before these patients underwent their bypass surgery. The results from this study were convincing that ASL can replace PET to characterize the pathophysiology of Moyamoya disease patients. The image in this blog shows the vessel occlusion and its impact on blood flow in a Moyamoya patient.

Another advantage of ASL is the elimination of contrast agents. In many MRI exams, patients need to receive a contrast agent (such as gadolinium) to enhance the image quality. However, the contrast agent can cause side effects and deposit in the brain. Although there is no evidence suggesting its impact on health, we should minimize the use of these contrast agents. In the same study, Dr. Zhao’s team also demonstrated that the advanced ASL can create images without contrast agents and that doctors favored the new ASL technique over the conventional contrast-based imaging method.

Taken together, ASL MRI will become more accessible to radiologists to diagnose Moyamoya disease without causing side effects to patients. The technique will allow safe, affordable, and fast for imaging to identify patients with a higher risk for stroke.

Image source: JCBFM

 

REFERENCE

https://doi.org/10.1177/0271678X221083471

 

“The views, opinions, and positions expressed within this blog are those of the author(s) alone and do not represent those of the American Heart Association. The accuracy, completeness, and validity of any statements made within this article are not guaranteed. We accept no liability for any errors, omissions, or representations. The copyright of this content belongs to the author and any liability with regards to infringement of intellectual property rights remains with them. The Early Career Voice blog is not intended to provide medical advice or treatment. Only your healthcare provider can provide that. The American Heart Association recommends that you consult your healthcare provider regarding your health matters. If you think you are having a heart attack, stroke, or another emergency, please call 911 immediately.”
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PET or MRI, that is the question – Part 1

Moss Zhao, PhD

In our previous blogs, we discussed that doctors can diagnose Moyamoya disease using medical imaging systems, such as positron emission tomography (PET) and magnetic resonance imaging (MRI). But which one is better?

According to some recent studies performed by Dr. Moss Zhao (AHA Postdoctoral Fellow, 2021) at Stanford University, MRI is better thanks to its accessibility, safety, and affordability.

For decades, PET has been the gold standard technique for diagnosing Moyamoya disease based on imaging the blood flow in the abnormal blood vessels in the brain. However, PET uses radioactive tracers to create the images, making it complex and expensive. Although the amount of radiation is less than a 5-hour flight, doctors have sought for alternative and less invasive techniques to replace PET, especially for children. In recent years, arterial spin labeling (ASL), an advanced MRI technique, has emerged to replace PET imaging to measure blood flow in the brain. Because ASL MRI is more accessible at most hospitals and the procedure is less complex than PET, ASL has gained popularity in many research and clinical institutions for Moyamoya patients.

At Stanford University, Dr. Moss Zhao demonstrated that ASL could replace the conventional PET imaging technique without exposing patients to radiation and causing side effects. The image quality and measurement accuracy of ASL are compatible with PET, implying that ASL can be used to characterize the abnormal blood flow and circulation in Moyamoya patients. Among the different implementations of ASL, Dr. Zhao developed an advanced technique dubbed ‘multi-delay ASL’ that gives the best image quality with the least amount of scanning time. For less than 5 minutes, multi-delay ASL can produce images that require more than 20 minutes for PET imaging. The image in this blog shows the images collected by ASL and PET at the same time from normal and healthy people. Using the latest ASL techniques, doctors can identify patients with a high risk for stroke based on their MRI scans for just under 5 minutes without using any radioactive substances. Dr. Zhao’s team is currently testing this technique on the pediatric population to enable this non-invasive imaging technology to be accessible to patients across the lifespan.

Image source: NeuroImage

References:

https://doi.org/10.1016/j.neuroimage.2021.117955

 

“The views, opinions, and positions expressed within this blog are those of the author(s) alone and do not represent those of the American Heart Association. The accuracy, completeness, and validity of any statements made within this article are not guaranteed. We accept no liability for any errors, omissions, or representations. The copyright of this content belongs to the author and any liability with regards to infringement of intellectual property rights remains with them. The Early Career Voice blog is not intended to provide medical advice or treatment. Only your healthcare provider can provide that. The American Heart Association recommends that you consult your healthcare provider regarding your health matters. If you think you are having a heart attack, stroke, or another emergency, please call 911 immediately.”
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Innovations in 3-D and 4-D Technology in the Cath Lab

Lina Ya'qoub, MD

There have been tremendous advances in 3-dimensional (3-D) technologies in the past few years, not only in various medical and surgical fields but also in our daily lives outside of work; with more and more new features in cell phones, computer design programs, and movies!!  4-dimensional (4-D) imaging captures 3-D images over time. These technologies are particularly important in cardiology, especially in interventional cardiology. The heart is a very dynamic organ, and understanding the variation in the anatomy of vessels and geometry of cardiac structures is key to ensuring successful procedures, patient’s safety and good outcomes. More recently, newer innovations in both 3-D and 4-D technologies have been developed, so I decided to shed light on some of these innovations and how they can be potential game-changers in the cath lab.

  • 3-D Holograms

This technology was actually displayed at the Transcatheter Cardiovascular Therapeutics (TCT) 2019 meeting. It converts live transesophageal echo (TEE) imaging into real-time 3-D holographic video in the cath lab to aid structural heart procedures.  The 3-D hologram is projected on a special display screen, and the interventional cardiologist uses hand movements and a foot pedal/switch to change the image orientation without breaking the sterile field. It also allows the operator to see the tools they use in the cath lab, including catheters or devices, in real-time in a 3-D format. This technology does not even require the user to wear 3-D glasses! It was submitted for FDA regulatory review in September 2019.

  • HeartFlow Planner

This is a noninvasive, real-time virtual tool for coronary artery disease intervention. It allows interventional cardiologists to virtually map vessels on a 3-D coronary tree, with color codes indicating the fractional flow reserve-computed tomography (FFR-CT) values for each vessel as measured by a computational fluid dynamics algorithm. This seems to be a good tool for percutaneous coronary intervention (PCI) planning in vessels with significant disease; as it aims to provide us with a non-invasive way to determine whether a stenotic lesion if potentially flow limiting. However, it is important to note the CT-FFR has its own limitations, and some patients might still need invasive FFR for accurate assessment. This tool was approved by the FDA in September 2019.

Figure 1: 3-D CT-FFR coronary tree showing both flow limiting and non-flow limiting lesions [from reference 1].

  • 3-D Printing

3-D printing has been used in the surgical fields for more than a decade. It refers to making complex 3-D objects from computer-aided designs. This technology has been increasingly utilized in structural heart procedures in the past few years, where these 3-D models can be printed from a patient’s CT, magnetic resonance imaging (MRI), or 3-D ultrasound images (Figure 1). These 3-D printed structures not only help with procedural planning and device sizing but also allow operators to practice dry runs and perform pre-procedural navigation.

Figure 2: Image of a 3-D printed model which shows cardiac valves and major vessels with their geometric locations relative to each other (reference 3).

  • 4-D Imaging

4-D imaging adds an important component to 3-D imaging, which is the change of these 3-D images over time. 4-D flow images include the direction of blood flow, blood velocities and shear wall stress [2] (Figure 3). This is particularly important in coronary interventions, structural heart procedures and different congenital abnormalities where identification of blood flow in the 4-D view is useful, especially when the anatomy is complex. These changes in position over time help guide our procedures, not only to ensure successful outcomes but also to avoid potential complications. These 4-D images require large amounts of data, but they can be obtained from either cardiac MRI or computational fluid dynamics, which is a specialized area of mathematics and fluid mechanics in engineering [2]. 4-D imaging is still in its early phases, but it is another exciting advancement in our field.

Figure 3: Representation of an MRI-generated 4-D flow image showing blood flow through the aorta and major vessels (reference 4).

In conclusion, we have seen and continue to see tremendous advances in the innovations of 3-D and 4-D imaging with important implications in our work in the cath lab. With our continued collaboration with informational technology experts, engineers, and scientists, these innovations are potentially game-changers in different fields, including coronary interventions and structural heart procedures. I look forward to seeing how this technology continues to evolve in the coming decades!!

References:

  • Fornell, Dave “Overview of the top news and new technologies at the 2019 Transcatheter Cardiovascular Therapeutics meeting”, November 2019,

https://www.dicardiology.com/article/6-hot-topics-interventional-cardiology-tct-2019

https://www.itnonline.com/content/arterys-showcases-fda-cleared-4d-flow-mri-software-rsna-2016

“The views, opinions and positions expressed within this blog are those of the author(s) alone and do not represent those of the American Heart Association. The accuracy, completeness and validity of any statements made within this article are not guaranteed. We accept no liability for any errors, omissions or representations. The copyright of this content belongs to the author and any liability with regards to infringement of intellectual property rights remains with them. The Early Career Voice blog is not intended to provide medical advice or treatment. Only your healthcare provider can provide that. The American Heart Association recommends that you consult your healthcare provider regarding your personal health matters. If you think you are having a heart attack, stroke or another emergency, please call 911 immediately.”
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The Significant Areas of Interest in the Field of Cardiac Imaging in 2018

Renee Bullock-Palmer, MD

There were several exciting developments in 2018 with regards to cardiac imaging. The role of the cardiac imager is becoming increasingly relevant in today’s cardiology practice environment and bridges across several subspecialties in Cardiology, such as electrophysiology with the use of transesophageal echocardiography (TEE) in the placement of left atrial appendage closure devices. These devices include Watchman and interventional cardiology with structural and valvular heart disease and echocardiographic guidance with transaortic valve replacement (TAVR), percutaneous mitral valve repair with MitralClip, as well as atrial septal and ventricular septal closure devices. The field of cardiac imaging has matured over the years and not only includes echocardiography and nuclear cardiology, but also includes advanced imaging with cardiac magnetic resonance imaging (cMRI) and cardiac computed tomography. In addition, there has been the rise of the interventional echocardiographer specializing in the use of echocardiography in guiding percutaneous and surgical treatment of structural heart disease. In fact, there has been recognition of cardiac imaging by several professional societies such as the American College of Cardiology with publication of the state-of-the-art paper, The Future of Cardiac Imaging Report of a Think Tank Convened by the American College of Cardiology1. There have also been several disease states that have been positively influenced by the development of new diagnostic technology in cardiac imaging, such as cardiac amyloidosis. Cardiac imaging has also positively influenced preventive cardiology with release of the latest American Heart Association (AHA)/ American College of Cardiology (ACC) 2018 Cholesterol Management Guidelines2. The following areas were, in my opinion, considered topics of great interest in 2018 in the field of cardiac imaging.

 

Nuclear Imaging

Cardiac Amyloidosis. For several years, cardiac amyloidosis, particularly transthyretin type (ATTR type), was thought to be a diagnosis that was very difficult to make with endomyocardial biopsy being the only method to confirm the diagnosis. However, nuclear cardiac imaging has changed the landscape of this disease with the novel application of old technology with the use of technetium 99m pyrophosphate (Tc-99m PYP) in the diagnosis of ATTR type cardiac amyloidosis3. The sensitivity and specificity of this technique in diagnosing this disease state is >95%, and oftentimes avoids the need for endomyocardial biopsy to make this diagnosis4. The development of this technique in diagnosing the disease has increased the recognition of this disease in many patients with diastolic heart failure, and even in patients with severe aortic valve stenosis undergoing TAVR. This has also led to greater research and development of new treatments for this disease, such as tafamidis, patisiran and inotersen. The development of these medications will hopefully improve the overall prognosis for patients with this disease.

 

Echocardiography

The Rise of the Interventional Echocardiographer in Structural Cardiac Imaging. There has been increasingly relevant areas of interest in structural heart disease, such as percutaneous mitral valve repair with MitralClip, especially with the release of the study findings from the COAPT trial5.  In addition, transaortic valve replacement (TAVR) has become increasingly available for many patients with severe aortic valve stenosis, and many institutions have began offering this therapy to many of their patients. Additionally, left atrial appendage occlusive devices such as the Watchman device are being increasingly used in patients with atrial fibrillation who are at high risk for hemorrhagic complications with anticoagulation, despite having indications for thromboembolic prophylaxis. With these new developments, there has been the rise of the interventional echocardiographer, who serves a vital role with the use of echocardiography in guiding the placement of these devices in the treatment of structural heart disease. Many fellows are now seeking additional training in this field to meet this demand, as this area has invited a growing interest in the cardiology field and has attracted many trainees.

 

Cardiac Computed Tomography

The revisiting of Coronary Calcium Score as a Powerful Tool in Preventive Cardiology. The release of the latest AHA/ACC Cholesterol Management Guidelines has been an area of great interest in the field. The latest guidelines have included the use of coronary calcium scoring with cardiac CT as a tool to further risk stratify patients to guide the use of pharmacologic therapy for patients with hyperlipidemia2. This has led to  the resurgence of Cardiac CT for coronary calcium scoring as a valuable tool for cardiologists in the field of preventive cardiology.

Utility of Cardiac CT in the assessment of Women with suspected Cardiovascular Disease.  There has also been the increasing recognition of Cardiac CT as a useful diagnostic tool for women suspected of having cardiovascular disease (CVD)6. Hopefully, this will result in the increased appropriate use of Cardiac CT in the management of CVD in women.

 

Cardiac MRI

The complementary role of Cardiac MRI with echocardiography and assessment of valvular and structural heart disease. Cardiac MRI has become an established imaging modality in the assessment of valvular heart disease. This has been embraced by the American Society of Echocardiography’s latest Valvular Guidelines, which includes cardiac MRI as playing a complementary role in the assessment of the severity and etiology of valvular heart disease7. The use of Cardiac MRI is also useful in the assessment of other disease states, such hypertrophic cardiomyopathy and risk assessment for sudden death8.

The rise of Cardiac MRI compatible devices. There has also been the development of Cardiac MRI compatible devices which now allows many patients with these devices to be able to have cardiac MRIs performed safely. Cardiac MRI is therefore a viable diagnostic tool for these patients.

The first administration of certification board exam in cardiovascular magnetic resonance imaging (CBCMR).  With the maturation of Cardiac MRI as a viable imaging modality, 2019 will see the inaugural administration of the first certification exam in cardiovascular magnetic resonance imaging (CBCMR), which will occur between May 7 – June 7, 2019, and the 2019 application window will open on January 15, 2019. ​​

 

Conclusion:

With the dawn of a new year in 2019, it is clear that the future of cardiac imaging is very bright. I am looking forward to many more promising developments in this field and hope that this field will continue to attract many more talented cardiologists in this area of cardiology.

 

References:

  1. Douglas PS, Cerqueira MD, Berman DS, Chinnaiyan K, Cohen MS, Lundbye JB, et al. The Future of Cardiac Imaging Report of a Think Tank Convened by the American College of Cardiology. J Am Coll Cardiol Img 2016;9:1211–23.
  2. Grundy SM, Stone NJ, Bailey AL, Beam LT, Birtcher KK, et al. 2018AHA/ACC/AACVPR/AAPA/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA Guideline on the Management of Blood Cholesterol. JACC Nov 2018, 25709; DOI: 10.1016/j.jacc.2018.11.003.
  3. Dorbala S, Bokhari S, Miller E, Bullock-Palmer RP, Soman P, Thompson R. ASNC Practice Points: 99mTechnetium-Pyrophosphate Imaging for Transthyretin Cardiac Amyloidosis (American Society of Nuclear Cardiology website). 2018. Available at: https://www.asnc.org/Files/Practice%20Resources/Practice%20Points/ASNC%20Practice%20Point-99mTechnetiumPyrophosphateImaging2016.pdf.
  4. Gillmore JD, Maurer MS, Falk RH, Merlini G, Damy T, Dispenzieri A, et al. Nonbiopsy Diagnosis of Cardiac Transthyretin Amyloidosis. Circulation. 2016 Jun 14;133(24):2404-12. Doi: 10.1161/CIRCULATIONAHA.116.021612. Epub 2016 Apr 22.
  5. Stone GW, Lindenfeld J, Abraham WT, Kar S, Lim DS, Mishell JM,et al. COAPT Investigators.Transcatheter Mitral-Valve Repair in Patients with Heart Failure. N Engl J Med. 2018 Dec 13;379(24):2307-2318. doi: 10.1056/NEJMoa1806640. Epub 2018 Sep 23.
  6. Truong QA, Rinehart S, Abbara S, Achenbach S, Berman DS, Bullock-Palmer R,et al. SCCT Women’s Committee.Coronary computed tomographic imaging in women: An expert consensus statement from the Society of Cardiovascular Computed Tomography. J Cardiovasc Comput Tomogr. 2018 Nov – Dec;12(6):451-466. doi: 10.1016/j.jcct.2018.10.019. Epub 2018 Oct 23.
  7. Zoghbi WA, Adams D, Bonow RO, Enriquez-Sarano M, Foster E, Grayburn PA, et al. Recommendations for Noninvasive Evaluation of Native Valvular Regurgitation A Report from the American Society of Echocardiography Developed in Collaboration with the Society for Cardiovascular Magnetic Resonance. J Am Soc Echocardiogr. 2017 Apr;30(4):303-371. doi: 10.1016/j.echo.2017.01.007. Epub 2017 Mar 14.
  8. Weng Z, Yao J, Chan RH, He J, Yang X, Zhou Y, He Y.Prognostic Value of LGE-CMR in HCM: A Meta-Analysis. JACC Cardiovasc Imaging. 2016 Dec;9(12):1392-1402. doi: 10.1016/j.jcmg.2016.02.031. Epub 2016 Jul 20. Review.