Patient/Patient's/Patients'

I am writing a job summary that has many references like the following:

I reviewed patient/patient's/patients' charts..... I maintained patient/patient's/patients' files

I analyzed patient/patient's/patients' ex-rays.........I reviewed patient/patient's/patients' histories

There was more than one patient's chart, file or ex-ray. I know that the proper way ordinarily would generally be "patients' charts" (plural possessive), but what I am wondering is if in the medical field the general method of usage is to drop the s' and make it patient charts, patient ex-rays, patient files, patient histories, etc. because that is generally the way I hear it said. Which is the best way to write this. The summary is really important to my future and it is important that this be accurate and properly stated? Are there any other phrases that might be done differently? Thanks for your help!