Nav: Home

'Aneurysm Number' may help surgeons make treatment decisions

March 26, 2019

WASHINGTON, D.C. March 26, 2019 -- Aneurysms form as abnormal bulges or balloonings over an artery, and, if ruptured, can lead to serious health complications or even death. Some aneurysms can exist for a long time without rupturing, and the surgery involved in treating aneurysms can be quite risky, so a parameter to help guide surgeons is needed.

Today, treatment decisions are made mainly by assessing the geometric parameters such as the size of an aneurysm, which is obtained from medical images. But the fluid mechanics are known to be an important factor in the initiation, growth and rupture of aneurysms. The factors determined by flow, such as the shear stress and its oscillations on the walls of an artery, require cumbersome flow measurements and numerical simulations. A simple parameter that depends on both flow and geometry, which can substitute flow factors (that require flow measurements and simulations) doesn't exist.

But now, as researchers from the University at Buffalo and Texas A&M University report in the journal Physics of Fluids, from AIP Publishing, they have developed a simple nondimensional parameter that depends on both geometry and flow waveform to classify the flow mode in both sidewall and bifurcation aneurysms.

"This simple parameter, called 'aneurysm number (An),' is the ratio of time scales of two competing phenomena in aneurysms: First is the transport time scale, which represents the transport of a fluid particle through the aneurysm expansion," said Iman Borazjani, an associate professor at Texas A&M. "Second is the vortex formation time scale, which represents the formation of a vortex due to the pulsatile flow into an expansion."

The transport phenomenon creates a stationary shear layer through the expansion region, he explained, whereas the vortex phenomenon likes to create a vortex ring. If the transport time scale is smaller (An<1), then a stationary shear layer is formed and the flow mode is called the cavity mode. Otherwise, a ring vortex is formed (An>1) and the flow mode is the vortex mode.

The group's work is a significant breakthrough because they were able to show that not only can their aneurysm number classify the flow mode in both simplified and anatomic geometries, but also that the oscillations of shear stress are higher in the flow in the vortex mode (An>1). "This means that our simple parameter might be a good substitute for the oscillatory shear parameter -- without the need for challenging flow measurements and simulations to calculate shear on the wall," Borazjani said.

When the researchers first submitted their simplified work, several reviewers questioned whether the results for simplified geometries are applicable to real anatomic ones. "They weren't convinced, so we had to show that our parameter works for anatomic geometries. Now, a pair of articles are being published together," Borazjani said, explaining why the group went on to write a second article about their work. They first developed and tested their parameter for simplified (idealized) geometries in part I of their article, and then applied it to anatomic ones in part II.

Oscillatory shear, which is related to the group's parameter, is thought to affect the endothelial cells and promote inflammation, growth of aneurysms, and even their rupture. For example, "a vortex flow mode is more likely to rupture because it has a higher oscillatory shear," Borazjani said. "Therefore, we think our simple parameter can help surgeons in making decisions to treat an aneurysm in the future."
-end-
The first part of the article, "A non-dimensional parameter for classification of the flow in intracranial aneurysms I: Simplified geometries," is authored by Hafez Asgharzadeh and Iman Borazjani. The second part, "A non-dimensional parameter for classification of the flow in intracranial aneurysms II: Patient-specific geometries," is authored by Hafez Asgharzadeh, Hossein Asadi, Hui Meng and Iman Borazjani. The pair of articles will appear in Physics of Fluids on March 26, 2019 (DOI: 10.1063/1.5033942; DOI: 10.1063/1.5081451). After that date, the articles can be accessed at http://aip.scitation.org/doi/full/10.1063/1.5033942 and http://aip.scitation.org/doi/full/10.1063/1.5081451.

ABOUT THE JOURNAL

Physics of Fluids is devoted to the publication of original theoretical, computational, and experimental contributions to the dynamics of gases, liquids, and complex or multiphase fluids. See http://pof.aip.org.

American Institute of Physics

Related Aneurysm Articles:

Temple researchers track new path to therapeutic prevention of abdominal aortic aneurysm
New research by scientists at the Lewis Katz School of Medicine at Temple University suggests that abdominal aortic aneurysm (AAA) can be prevented therapeutically.
Researchers find no benefit for treatment used to avoid surgery for abdominal aortic aneurysm
A new landmark study by researchers at the University of Maryland School of Medicine (UMSOM) found that patients with a vascular condition, called abdominal aortic aneurysm, received no benefits from taking a common antibiotic drug to reduce inflammation.
Genetic scoring can identify more men at risk for aortic aneurysm
A genetic risk score from a blood test identified more men age 50 and older who are at higher risk of an aortic aneurysm and could benefit from ultrasound screening.
New findings boost understanding of arterial aneurysm
Abdominal arterial (or aortic) aneurysm in older men is associated with levels of certain subtypes of white blood cells, a study from the University of Gothenburg, Sweden, shows.
Presence of blood clot associated with rapid aortic aneurysm growth
The presence of a blood clot on the wall of the aorta in people with abdominal aortic aneurysms is associated with more rapid, potentially dangerous growth in the aneurysm, according to a major new study.
Advances in the detection of the postoperative progress of abdominal aortic aneurysm
A study published in Frontiers in Bioengineering and Biotechnology by a team of researchers from BCN MedTech with the VICOMTech Foundation in San Sebastian, the BioDonostia Health Research Institute and Donostia University Hospital, offers a promising methodology for post-operative CTA time-series registration and subsequent aneurysm biomechanical strain analysis, which correlates with the patient's long-term prognosis.
Can aspirin decrease the rate of intracranial aneurysm growth?
Researchers investigated whether aspirin can aid in the prevention of intracranial aneurysm rupture by hindering aneurysm growth.
Researchers uncover new cause of abdominal aortic aneurysm
Researchers have discovered that a family of lipids (fats) contribute to the development of a serious aortic disease, by driving clotting in the blood vessel wall.
'Aneurysm Number' may help surgeons make treatment decisions
Aneurysms form as abnormal bulges over an artery, and, if ruptured, can lead to serious health complications or even death.
New personal health management tool predicts risk for abdominal aortic aneurysm from DNA
Detecting inherited risk factors for diseases tied to more than a single gene has proved challenging.
More Aneurysm News and Aneurysm Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Meditations on Loneliness
Original broadcast date: April 24, 2020. We're a social species now living in isolation. But loneliness was a problem well before this era of social distancing. This hour, TED speakers explore how we can live and make peace with loneliness. Guests on the show include author and illustrator Jonny Sun, psychologist Susan Pinker, architect Grace Kim, and writer Suleika Jaouad.
Now Playing: Science for the People

#565 The Great Wide Indoors
We're all spending a bit more time indoors this summer than we probably figured. But did you ever stop to think about why the places we live and work as designed the way they are? And how they could be designed better? We're talking with Emily Anthes about her new book "The Great Indoors: The Surprising Science of how Buildings Shape our Behavior, Health and Happiness".
Now Playing: Radiolab

The Third. A TED Talk.
Jad gives a TED talk about his life as a journalist and how Radiolab has evolved over the years. Here's how TED described it:How do you end a story? Host of Radiolab Jad Abumrad tells how his search for an answer led him home to the mountains of Tennessee, where he met an unexpected teacher: Dolly Parton.Jad Nicholas Abumrad is a Lebanese-American radio host, composer and producer. He is the founder of the syndicated public radio program Radiolab, which is broadcast on over 600 radio stations nationwide and is downloaded more than 120 million times a year as a podcast. He also created More Perfect, a podcast that tells the stories behind the Supreme Court's most famous decisions. And most recently, Dolly Parton's America, a nine-episode podcast exploring the life and times of the iconic country music star. Abumrad has received three Peabody Awards and was named a MacArthur Fellow in 2011.