The organoid suspension should be as homogeneous in size as possible to allow for even dispensing of organoids in to screening plates. As organoids are too large to be counted by an automated cell counter or a hemocytometer, dispense three 10 μL droplets of the organoid suspension on to a microscope slide and count the number of organoids in each 10 μL droplet. Multiply the average number of organoids per droplet by 100 to calculate the number of organoids per mL.
A suspension of 15,000--20,000 organoids per mL is required for drug screening as it can generate sufficient signal to measure drug response.
Please refer to the attached article for more information.
Chapter Drug Sensitivity Assays of Human Cancer Organoid Cultures
For drug screening purposes with the grown organoids I may suggest looking into automating the imaging/counting/sizing of these especially if you want to do this at any scale (ie. different drugs across different organoid types). While I don't know where you are at within MDACC you may want to see if anyone around you is working with a GelCount as there are several units around MDACC.