https://www.labx.com/resources/progress-in-3-d-imaging-microscopy-and-brain-mapping/75
True 3-dimensional brain mapping achievements have remained elusive.
To reliably image subcellular elements of neurons, a pixel resolution of 10 nm is required. The most established EM method for this scale has been block-face imaging with either focused ion beam ablation or in situ microtome cutting. Aside from the fact that these techniques are challenged by edge distortions and irreversible destruction of the samples, the logistics of integrating the 20,000 mm2 images for 3-D rendering are mind blowing – 50 ns per pixel or 6 years per cubic millimeter.
Multi-beam SEM theoretically provides an answer this problem, although, until the advent of the Zeiss MultiSEM, instrument developments remained largely in the prototype stage. The MultiSEM is similar in overall principle to single-beam SEM – the sample is bombarded with a focused beam probe about 1 nm in size. The electron beam is scanned line by line over the sample, ultimately generating the SEM image.
The MultiSEM 505 accelerates the process through parallelization. The beam produces 61 electron beams which in turn produce secondary electrons reflected from the image and projected onto a multi-detector, one beam per channel. This parallel data capture and processing can cut the logistics time interval to 3 or 4 months instead of 6 years with single SEM. The Zeiss MultiSEM 506 expands this to 91 beams and a field of view 3.5 times larger, further accelerating the imaging process.
large-scale data acquisition is now met with the next challenge in 3-D brain mapping – the big data issue. Each scan results in 1 petabyte of data. Considering the mouse brain is roughly 10x10x5 cubic mm and 80 million neurons in size, the total data set would reach 1.5 exabytes. An exabyte is 1,000 petabytes, and a petabyte is 1,000,000 bytes. Realistically, there is not much to compare exabytes with, in fact it is estimated that 5 exabytes is equal to all of the words spoken by mankind, and more that the world's current data storage capabilities. Not big but immense data…
True 3-dimensional brain mapping achievements have remained elusive.
To reliably image subcellular elements of neurons, a pixel resolution of 10 nm is required. The most established EM method for this scale has been block-face imaging with either focused ion beam ablation or in situ microtome cutting. Aside from the fact that these techniques are challenged by edge distortions and irreversible destruction of the samples, the logistics of integrating the 20,000 mm2 images for 3-D rendering are mind blowing – 50 ns per pixel or 6 years per cubic millimeter.
Multi-beam SEM theoretically provides an answer this problem, although, until the advent of the Zeiss MultiSEM, instrument developments remained largely in the prototype stage. The MultiSEM is similar in overall principle to single-beam SEM – the sample is bombarded with a focused beam probe about 1 nm in size. The electron beam is scanned line by line over the sample, ultimately generating the SEM image.
The MultiSEM 505 accelerates the process through parallelization. The beam produces 61 electron beams which in turn produce secondary electrons reflected from the image and projected onto a multi-detector, one beam per channel. This parallel data capture and processing can cut the logistics time interval to 3 or 4 months instead of 6 years with single SEM. The Zeiss MultiSEM 506 expands this to 91 beams and a field of view 3.5 times larger, further accelerating the imaging process.
large-scale data acquisition is now met with the next challenge in 3-D brain mapping – the big data issue. Each scan results in 1 petabyte of data. Considering the mouse brain is roughly 10x10x5 cubic mm and 80 million neurons in size, the total data set would reach 1.5 exabytes. An exabyte is 1,000 petabytes, and a petabyte is 1,000,000 bytes. Realistically, there is not much to compare exabytes with, in fact it is estimated that 5 exabytes is equal to all of the words spoken by mankind, and more that the world's current data storage capabilities. Not big but immense data…
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