MoFlo vs. Cytofluorograf?

Doug Ferguson fergusn at
Tue Aug 11 21:41:50 EST 1998

Moflo vs. Cytofluorograph ???

I really don't want to engage in a conflict about who has the "best"
cytometer, but I am compelled here to bring some facts to the table as
to head off misunderstanding.

The MoFlo flow cytometer is really about function first. Brian's comment
about MoFlo is correct. It is a modular flow cytometry system that does
support and encourage constant improvement. That is, in fact, it's
strongest point. However, in it's current state, it is still an
extremely high performance flow cytometer. The Cytofluorograf was a
great flow cytometer for it's time, particularly as a high-sensitivity
sorter, but due to it's integrated architecture, it did not lend itself
to continuous upgrade-ability and therefore fell behind. To compare
MoFlo with the Cytofluorograf is an apple/orange comparison in two
respects. First, the Cytofluorograf was not modular and therefore wasn't
very amenable to substantial upgrade. But I want to make the additional
point that the Cytofluorograf incorporated processing electronics that
are two decades behind MoFlo (as it is in it's present state).

A few thoughts in particular:

Bandwidth: The entire analog front end of MoFlo has a bandwidth in the
megahertz, the bandwidth of the Cytofluorograf was in the tens of
kilohertz. This is a critical measure of the cytometers' ability to
process cells quickly AND accurately. If an extremely bright event
occurred in the Cytofluorograf it would take hundreds of microseconds
for the electronics to recover enough to measure a dim event accurately.
MoFlo can experience a full scale bright event (at the top of the fourth
decade) and still be able to measure an event at it's fluorescence
threshold in a little more than one microsecond.

Processing Time:
The Cytofluorograf was able to process an event in about 50
microseconds. MoFlo is able to process an event in about 5 microseconds.
This remains true independently for each of the three lasers. All gating
and sorting processing is performed real time. There are no information
flow bottlenecks where bursts of events can plug up processing queue's.

The Cytofluorograf ran at a fixed droplet rate of 32,000 drops per
second. At this droplet formation rate, the sort window for the
instrument could be set to 10 droplets to be sure to "catch" the event.
MoFlo has timing resolution such that it knows exactly where each event
is in a given drop. Meanwhile it is still able to perform friend or foe,
contamination or non-contamination, preferred-position-in-a-drop,
determinations for each event up to 16 events in each drop in a eight
direction sort at 120,000 drops per second, perform the sort and keep an
accurate cell count for each sort direction.

I normally don't respond to these comments, but this one required one.
MoFlo may not be the prettiest cytometer (I am sure that it is to some),
but behind the panels is some very well thought out engineering. And
behind the instrument is an architecture that allows it to be
continuously improved. To say that MoFlo may be doomed to end up
antiquated just doesn't make sense.

Doug Ferguson

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