Paper accepted, Am J Neuroradiol

I never know what is the embargo policy for specific journals, but since the printer has delayed the processing of our paper (accepted almost three months ago), I think it's fair that we share the good/bad news about a study led by BSL postdoc Kristian Valen-Sendstad, entitled: "Mind the gap: Impact of CFD solution strategy on prediction of intracranial aneurysm hemodynamics and rupture status indicators".  Here's the abstract, paper (hopefully) coming soon:

Background and Purpose: Computational fluid dynamics (CFD) has become a popular tool for studying intracranial aneurysm hemodynamics, demonstrating success for retrospectively discriminating rupture status; however, recent highly-refined simulations suggest potential deficiencies in solution strategies normally employed in the aneurysm CFD literature. The purpose of the present study was to determine the impact of this gap.
Materials and Methods: Pulsatile flow in 12 realistic MCA aneurysms was simulated using both high resolution (HR) and normal resolution (NR) strategies. Velocity fields were compared at selected instants via domain-averaged error. Wall shear stress (WSS) fields and various reduced hemodynamic indices were also compared: cycle-averaged mean and maximum WSS; oscillatory shear index (OSI); low shear area (LSA); viscous dissipation ratio (VDR); kinetic energy ratio (KER).
Results: Instantaneous differences in flow and WSS patterns were appreciable, especially for bifurcation aneurysms. Linear regressions revealed strong correlations (R2>0.9) between HR and NR solutions for all indices but KER (R2=0.25) and OSI (R2=0.23); however, for most indices the slopes were significantly less than one, reflecting a pronounced underestimation by the NR simulations. Some HR simulations were highly unstable with fluctuating WSS, reflected by the poor OSI correlation.
Conclusion: Typical CFD solution strategies may ultimately be adequate for augmenting rupture risk assessment based on certain highly-reduced indices; however, they cannot be relied upon for predicting the magnitude and character of the complex biomechanical stimuli to which the aneurysm wall may be exposed. This impact of CFD solution strategy is likely greater than that for other modelling assumptions or uncertainties.

NYT rakes our prime minister, er, over the coals

Your correspondent is back after a long absence. Apologies for the copyright violation, but this New York Times editorial is too "good" not to share, although I'm sure it will be dismissed as commie pinko propaganda.  Dark Age Ahead, my friends. Or, to put it more colloquially, "money talks, bullshit walks".

Silencing Scientists

By Verlyn Klinkenborg

Published: September 21, 2013

Over the last few years, the government of Canada — led by Stephen Harper — has made it harder and harder for publicly financed scientists to communicate with the public and with other scientists.

It began badly enough in 2008 when scientists working for Environment Canada, the federal agency, were told to refer all queries to departmental communications officers. Now the government is doing all it can to monitor and restrict the flow of scientific information, especially concerning research into climate change, fisheries and anything to do with the Alberta tar sands — source of the diluted bitumen that would flow through the controversial Keystone XL pipeline. Journalists find themselves unable to reach government scientists; the scientists themselves have organized public protests.

There was trouble of this kind here in the George W. Bush years, when scientists were asked to toe the party line on climate policy and endangered species. But nothing came close to what is being done in Canada.

Science is the gathering of hypotheses and the endless testing of them. It involves checking and double-checking, self-criticism and a willingness to overturn even fundamental assumptions if they prove to be wrong. But none of this can happen without open communication among scientists. This is more than an attack on academic freedom. It is an attempt to guarantee public ignorance.

It is also designed to make sure that nothing gets in the way of the northern resource rush — the feverish effort to mine the earth and the ocean with little regard for environmental consequences. The Harper policy seems designed to make sure that the tar sands project proceeds quietly, with no surprises, no bad news, no alarms from government scientists. To all the other kinds of pollution the tar sands will yield, we must now add another: the degradation of vital streams of research and information.

So long, Flanders!

We are sorry to see Jonathan Mynard leave the BSL to return down under to complete his postdoctoral research back home.  However, as a parting memento, he has left us with this startlingly accurate rendering of his friends at the BSL.  So long, Jonathan, it's been, er, ehhhhx-cellent, having you here!

SBC2012 CFD Challenge published in J Biomech Eng

It was a lot of work, but worth it. The results of the ASME 2012 Summer Bioengineering Conference's CFD Challenge are finally out in a special issue of J Biomech Eng. Thanks to everyone who participated so enthusiastically!  Future challenges are in the works (although not necessarily tied to SBC).

Payam Bijari, freshly PhD'd

Congratulations to BSL's Payam Bijari, who this morning successfully defended his PhD thesis, on "Investigation of Arterial Geometry as a Local Risk Factor for Carotid Atherosclerosis", before an eminent line-up of examiners including UofT's Richard Cobbold, John Sled and Myron Cybulsky; and George Tech's Don Giddens, who wisely declined our offer of a free mid-winter trip to Toronto!

Ignatius J. Reilly, Gene Hunter?!?

Recently Dolores and I received a link to Viruses on Time, a blog post about virology-themed covers of Time magazine, sent to us via a mailing list we joined as part of an ESF Conference on Truth and Trust in Images, which we attended and presented at last fall. While the virus nerds were probably pondering the ethics and aesthetics of the portrayals, I was struck by the March 9, 1981 cover featuring Genetech's Herbert Boyer.  My soft-and-squishy-but-bonily-encased pattern recognition engine leapt immediately into action, and reported (and I paraphrase): "Holy Crap, that's Ignatius J. Reilly".

For those who don't know, Reilly is the protagonist of one of my favourite novels,  A Confederacy of Dunces, introduced to me by my 12th grade English teacher, who could clearly spot a misfit when she met one. Maybe it's a coincidence, but Confederacy won the Pulitzer Prize in 1981 (posthumously, another interesting, but sad, story), the same year as that Time cover.

Maybe the cover artists were one in the same (unlikely).  Or maybe the Time's cover artist was a fan of the book (possible).  Or maybe it was just "in the air".  I'd like to think it was the latter, since it faintly echoes our (and many others', of course) belief that scientific visualizations are, extricably, a product of the broader culture in which they are created.

Velocity profile skewing and Doppler ultrasound

Congratulations to BSL postdoc Jonathan Mynard, who has two papers coming out about the practical impact of velocity profile skewing in "straight vessels" (see our previous work here and here).  The first paper, in press with published by Ultrasound in Medicine & Biology, shows that it may not always be reasonable to infer flow rate waveform shape from maximum Doppler velocity traces, particular using a Poiseuille assumption. The second paper, accepted published by Atherosclerosis, highlights the substantial errors that can arise when trying to infer wall shear stresses from Doppler velocities under the common assumption of fully-developed flow.