Researchers working in MRI often compare one MRI technique against another, or an MRI technique against another method of measuring the same quantity. Comparing methods of measurement for agreement requires careful statistical analysis. It is easy to choose the wrong statistical test for this problem. Let’s briefly consider correlation, regression, and the t test for comparing methods, and learn why these techniques are not the most appropriate way of comparing methods for agreement. Then we’ll see why the bias plot does the job properly. Continue Reading »

In the course of developing ReviseMRI.com, I’ve read lots about how to make an interesting, interactive web site which is user (and browser) friendly. The biggest noise made about this concerns web standards.

If you’re designing websites, the following may provide some interesting reading. (If not…maybe skip this post.) Continue Reading »

In a past interview for research funding (a Fellowship award), I boldly stated

“Statistics makes the research-world go round.”

Whilst my eagerness to impress the interviewers is now embarrassingly obvious to me, I don’t think the statement is all that far from the truth. Here’s one case in point: it is well established that confidence intervals (CIs) communicate more useful information than P values in hypothesis testing. Continue Reading »

Artificial heart valves are usually safe for MRI, because any torque or attraction forces exerted by the external magnetic field are minimal compared to the force exerted by the beating heart. However, there is an interesting safety issue surrounding the induction of electric current in the artificial heart valve, which might theoretically compromise the function of some heart valves, in rare cases. The issue is the Lenz effect (aka eddy current damping).

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The unit of magnetic field is the Tesla, named after Nikola Tesla (visionary / genius / crazy / misunderstood et cetera). A company named after Tesla is Tesla Motors, who make the Tesla Roadster. Check this out:

• 100% electric
• 0-60 mph in 4 seconds
• Go 250 miles before re-charging (which takes 3.5 hrs)
• Top speed 130 mph
• Almost silent apart from wind / road noise

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