Advanced MRI Technique Provides Unprecedented Detail for Heart Defect Repair

A new MRI technique has been developed that allows physicians to simultaneously visualize heart tissue and blood flow. This innovative method aims to aid in identifying heart defects and precisely planning their repair, according to research published in Radiology: Cardiothoracic Imaging.

Visualizing the Heart in 3D

Researchers at Children's Hospital of Philadelphia (CHOP) in Pennsylvania have pioneered 3D volume rendering methods for cardiac MRI. These advanced techniques display complex heart structures and blood movement through them, offering visual data comparable to ultrasound images but without common angle-related challenges.

Volume rendering is a sophisticated computer graphics technique that generates 3D images directly from MRI scan data. It operates by assigning colors and transparency to different tissue types based on their appearance in the MRI.

Dr. Matthew Jolley, a pediatric cardiac anesthesiologist and cardiologist at CHOP, stated that specific settings were developed to make heart muscle and valves visible while rendering blood and surrounding tissues transparent.

Pinpointing Defects with Precision

This technique is particularly useful for observing blood flow through complex structures, such as valve leaflets. It enables the identification of specific leakage points in valves or holes in heart structures, which was previously not achievable with MRI.

As a practical example, the visualization tools significantly assisted in guiding the surgical approach for a 4-year-old boy with a leaking and narrowed aortic valve. The technique clearly showed the valve leaflets and a central jet of leakage, providing crucial guidance.

MRI's Distinct Advantages

The team has also developed new ways to display blood flow on MRI, including lines indicating flow direction and color-coded displays, similar to Doppler ultrasound. While 3D ultrasound offers combined tissue and flow views, it has a smaller field of view, and flow measurement accuracy can be dependent on the angle of the ultrasound beam.

CT scans provide anatomical images but lack the ability to show blood flow and involve ionizing radiation.

MRI, conversely, provides high-quality flow images irrespective of angles and does not use radiation, which is particularly beneficial for children who may require multiple imaging sessions.

Efficiency, Complement, and Limitations

Volume rendering generates visualizations almost instantaneously. This is critical for 4D moving images, where traditional manual tracing methods would be far too time-consuming.

Dr. Jolley noted that these MRI visualization techniques are intended to complement, rather than replace, ultrasound.

Limitations of the approach include its dependence on the quality of the underlying MRI scan. Manual tracing can still correct for image imperfections and remains necessary for certain analyses, such as computer simulations of heart function. The MRI-based images were observed to be similar to 3D echocardiography with color Doppler, a method familiar to physicians for evaluating heart valves.

SlicerHeart for Global Access

This significant work has culminated in SlicerHeart, a suite of free cardiac image processing tools. Developed using the open-source program 3D Slicer, these invaluable tools are now available for research and treatment in cardiovascular medicine, especially for congenital heart disease, at SlicerHeart.org.