As many of you may know, we have long been interested in determining left vs right. Our method integrated into align_epi_anat.py and afni_proc.py has been instrumental in finding important flipping issues in most of the open MRI databases, yet it can only determine the relative left-right agreement between a pair of datasets and not the absolute left-rightedness of each image.
Commonly used solutions require vitamin E capsules or saline bags placed to one side of the head. While a useful procedure, the problem remains that each site, researcher and technologist can choose a different side. We propose a clearer solution, i.e. the subject places the fingers on their left hand into an “L” shape and puts that next to their heads during structural scans. The attached image shows this simple procedure requiring no further equipment easily provides a solution for this vexing problem.
We are continuing work on this topic. We recognize other languages may not use the convenient “L” shape, so solutions are needed for “Izquierda”, “Sinistra”, “Gauche”, “剩下” and many others… Some of these alternatives are simple to implement, but others are likely to cause hand cramping. Please use caution.
This notice is part of our continuing AFDI.*