http://confocal-microscopy-list.275.s1.nabble.com/Deep-tissue-imaging-with-spinning-disc-comparison-with-other-confocal-techniques-tp7561610p7566050.html
Mark beat me to it in suggesting differences in pinhole size, which is probably the bulk of the explanation. I think that there is also another factor contributing, namely that defoccused spinning disk illumination looks rather like widefield illumination, so you might expect more signal (but not more contrast) at depth with a spinning disk system even if the pinholes were equivalent.
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>The improved penetration of SDC compared to confocal is almost certainly the wider pinhole of the SDC compared to confocal IMHO. As a shameless self citation, I think that the penetration depth issue and effect of pinhoie etc. are quite well illustrated in our paper:
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>Soeller C, Cannell MB. Two-photon microscopy: Imaging in scattering samples and three-dimensionally resolved flash photolysis. Microsc. Res. Tech. 1999;47(3):182–95.
>
>
>Note the effect of opening the pinhole fully in our Fig. 4 and the relative performance loss due to closing the pinhole with depth (highly non-linear with essentially no signal beyond 50 um in this sample). In this strongly scattering sample (cheese), 1% signal was obtained at 45 um with a pinhole, opening the pinhole increased the signal ~10x and using non-descanned detection increased the signal ~3x more. The method used 2P excitation in all cases so that we could examine the detector side performance -so the differences would be even greater for 1P where scattering also decreases excitation intensity at the focal spot ...
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>Cheers Mark
>
>
>On 18/05/2012, at 8:10 AM, Sebastian Rhode wrote:
>
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>> Hi Jan,
>>
>> since our company manufactures both kind of systems, spinning disc confocal
>> and 2-Photon systems, just my opinion on this paper.
>>
>> What I have seen so far during our tests, shows a clear advantage of 2PM if
>> depth penetration is your primary(!) goal. If it comes to speed, spinning
>> disc confocal (SDC) systems have a clear advantage. And in terms of cell
>> viability, 2PM and SDC are better than a conventional LSM microscope.
>>
>> What puzzles me a bit, is the comparison between the penetration depth of
>> the SDC and LSM. There are several points (some of them already mentioned by
>> George here), which makes it difficult for me to really compare the results.
>>
>> But nevertheless the findings are quite interesting, even if there are open
>> questions to answer. But I would be really interested in the explanation
>> about the observed results.
>>
>> Dr. Sebastian Rhode
>> Project Manager Research & Development
>>
>> TILL Photonics GmbH
>> an FEI Company