Thursday, March 31, 2011

Sort Schedule Changes: The Who, What and Why.

Let's start at the beginning.  Back in the days of the FACStar Plus and water cooled gas lasers, we would begin accepting sort reservations at 10AM.  This allowed us to get in at 9AM, warm up the lasers for 30 minutes, get the fluidics going, and have everything running smoothly by 10AM.  We typically did 1 or (on a good day) 2 sorts, which lasted 2-4 hours going at a rate of about 5000 events per second.  Adding the MoFlo in 2001 allowed us greater throughput by allowing us to run at 10's of thousands of cells per second, but we still needed a good amount of time to get started in the morning so the I-90s could warm up and the fluidics could stabilize.

As word got out about sorting applications in general, the sorters became busier and busier; so much so, that we traded in the old FACStar Plus, and traded up to the FACSAria.  Around the same time, we retired our water cooled gas lasers, and outfitted the MoFlo with the solid state Lyt-200 from iCyt.  The ease of setup on the Aria, and the nearly instant-on of the solid state lasers made getting started in the morning much easier.  Slowly but surely, we allowed earlier and earlier sorts until we officially added the 9AM - 10AM slot on both sorters.  The increased capacity kept up with demand for a period of time, but soon even running both sorters 9AM - 5PM wasn't enough.  We also saw that the afternoon slots were filled weeks in advance, and the unfortunate few who had to book sorts last minute were stuck with the 9AM slot, usually forcing them to get started in the wee hours of the morning.  In an attempt to solve this problem, and position ourselves for an S-10 application for a 3rd sorter, we added a 5PM - 8PM "late night" sorting slot on Tuesdays and Thursdays, and had one of the operators work a 12PM - 8PM shift on those days.  These slots were gobbled up instantly, and soon became a favored slot amongst the users.  Still struggling with overall capacity, the cancer center stepped up and helped us purchase another sorter, the FACSAria II.  So, now we had 3 sorters available from 9AM - 5PM Monday thru Friday, and the FACSAria II available an additional 3 hours on Tuesday and Thursday evening.  This setup served us very well for a couple of years.  Along the way, we still saw that afternoons filled up very quickly, and the 9AM slot was still being used for last minute sorts, or GFP cell line sorts.

So, we decided to take a look at usage more closely, and query our user group about the possibility of opening more 5PM - 8PM slots.  Of course everyone thought the idea of more evening slots was great, but we needed some data to support this change.  The figure below shows the frequency in a year of a sorter being used at each hour of the day.  It is separated out for each sorter.  The blue line shows what percentage of available time the sorters (as a whole) are being used.  As expected, the afternoon slots are used 70% of the time, while the 9AM slot is reserved only 25% of the time.  Also, the 5PM - 7PM slots are used 60% of the time, even though the actual number of sorts taking place appears low.  The 25% number at 9AM is also a bit misleading.  This represents that hour being booked, but I can tell you, it is very rare for someone who books a sort from 9AM until 11AM to actually show up at 9AM, and the longer that reservation is, the later they show up.  So, the actual usage of the 9AM hour is probably much lower.  I'd estimate it at 10% or so.  So, instead of sitting around waiting for the 9AM sort to show up, we could utilize that time better by getting QC done on our army of bench-top analyzers, or allow for more stabilization time of the sorters to get even better results.  So, beginning in April, we will have new sorting hours as follows:  M - F 10AM -5PM, and additionally on one sorter, 5PM - 8PM M - Th (no one wants to sort until 8PM on Friday night!).  The number of available hours per week is still about the same.  Previously, we offered 121 hours of capacity each week, and now we're offering 117 hours. Our actual weekly usage is about 70% of that anyhow, so we feel the new hours are plenty for the current demand.  In addition to all this, we have been aggressively pursuing users who are frequent FACSAria users to get trained and run their own sorts.  We have half a dozen users who already do this on a regular basis and will be tapping a few more competent users in the near future.  We feel this, along with the increased evening hours, and the removal of the 9AM slot, will maximize the efficiency of our sorters and allow more convenient access for our users.