PROPELLER-EPI for high-resolution DTI

PROPELLER-EPI with parallel imaging using a circularly symmetric phased-array RF coil at 3.0 T: application to high-resolution diffusion tensor imaging

A technique integrating multishot periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) and parallel imaging is presented for diffusion echo-planar imaging (EPI) at high spatial resolution. The method combines the advantages of parallel imaging to achieve accelerated sampling along the phase-encoding direction, and PROPELLER acquisition to further decrease the echo train length (ETL) in EPI. With an eight-element circularly symmetric RF coil, a parallel acceleration factor of 4 was applied such that, when combined with PROPELLER acquisition, a reduction of geometric distortions by a factor substantially greater than 4 was achieved. The resulting phantom and human brain images acquired with a 256 x 256 matrix and an ETL of only 16 were visually identical in shape to those acquired using the fast spin-echo (FSE) technique, even without field-map corrections. It is concluded that parallel PROPELLER-EPI is an effective technique that can substantially reduce susceptibility-induced geometric distortions at high field strength.

Chuang TC et al. Magn Reson Med. 2006 Dec;56(6):1352-8. PMID: 17051531

Discussion below the fold…. Continue reading “PROPELLER-EPI for high-resolution DTI”

reviewing Peer Review

Ars Technica has a nice summary of a recent paper in PLoS that attempted to assess the quality of the peer review process. From the Ars summary:

To examine what makes a good reviewer, they took advantage of the journal Annals of Emergency Medicine, which has maintained a detailed database of reviewers and post-review ratings (on a five-point scale) of their work, performed by the editors of the journal. The researchers contacted the reviewers and surveyed them about various factors that might contribute to skill in the process. A diverse set of 306 reviewers who had performed a total of nearly 3,000 reviews were used as the data set.


In news that may be disturbing for journal editors everywhere, very few factors leapt out as having a consistent and significant correlation with the quality of a review, although some factors did have strong correlations in individual tests. The only positive factors linked to quality of reviews were age (younger reviewers were better) and working at an academic hospital. Ironically, service on an Institutional Review Board, which evaluates and approves experiments on humans, consistently correlated with lower-quality peer reviews. Even these factors, however, were only slightly better than random at predicting review quality.

Ultimately the peer review process is always going to have a subjective component to it, since the processes of intuition and patterning that are fundamental to scientific insight and understanding are not really very deterministic. But there’s another possible reason why the study failed to find strong correlates of review quality; the very assessment of quality itself is equally subjective. I personally believe that the peer review system is like democracy – far from ideal but better than anything else out there. The best way to ensure general quality is to ensure that a maximum number of scientists in a given field participate in the process. Perhaps one way to achieve this would be to extend reviewer privileges to graduate students who have passed oral qualifiers?

Journal article citation: Callaham ML, Tercier J (2007) The Relationship of Previous Training and Experience of Journal Peer Reviewers to Subsequent Review Quality. PLoS Med 4(1): e40 doi:10.1371/journal.pmed.0040040

Related article: Kotchen TA, Lindquist T, Miller Sostek A, Hoffmann R, Malik K, Stanfield B. Outcomes of National Institutes of Health peer review of clinical grant applications. J Investig Med. 2006 Jan;54(1):13-9. PMID: 16409886


Here’s a great resource for sharing powerpoint slides online: SlideShare. Many of us have useful presentations that we’ve created for various academic or professional purposes; if you upload a presentation to that service please tag it “@refscan” so we can create an automatic table of contents for presentations here. I’ll update this post and upload a simple one later this weekend here as a demo.

FDA Advisory on Gadolinium contrast agents

The FDA has an updated Public Health Advisory on the safety of gadolinium-based MRI contrast agents. In a nutshell, patients with any sort of renal disease or otherwise compromised kidney function are at high risk of developing Nephrogenic Systemic Fibrosis (NSF) or Nephrogenic Fibrosing Dermopathy (NFD) if they receive gadolinium contrast agents for MRI imaging. There seems to be no risk for patients without compromised kidney function.

Continue reading “FDA Advisory on Gadolinium contrast agents”

the Just Science challenge

What if anti-Science didn’t exist? In other words, what if public outreach by scientists didn’t have to allocate a significant fraction of resources to combating pseudo-science and conspiracy theories? That’s the world that the Just Science Challenge wants to create, if only for a week, starting February 5th (monday). During that week, the challenge to science bloggers is thus:

Bloggers who self-identify as scientists and science writers should post on:

1. Published, peer-reviewed research and their own research.
2. Their expert opinion on actual scientific debates – think review articles.
3. Descriptions of natural phenomena (e.g., why slugs dissolve when you put salt on them, or what causes sun flares; scientific knowledge that has reached the level of fact)

We at Reference Scan will be participating in the Just Science Challenge. In fact if you registered as a user here at RefScan you might find that I’ve already upgraded your account to be able to post to the front page, because I can use the help!

There’s already an extensive list of participating science blogs. Magnetic Resonance Imaging is a field that is uniquely abused by anti-science and one that I think needs to be represented in the online scientific community. So let’s plant our flag and meet the challenge. Should be fun!