DICOM images stored by simple_storage use the DICOM Universal Identifier (UID) stored in the DICOM header to name the image files on the local disk. This long string of numbers and dots is designed to be unique among all DICOM images ever created. The convention used by manufacturers for UIDs varies - the following is my attempt to parse it out by observing the pattern over lots of images.

Philips ACS/NT 6.x naming convention:

                                     series  slice dynamic
                                         vv   v     v
1.3.46.670589.11.5406.9.955073100000002870301.3.1.1.1.0.44
^--------------^ ^----^ ^-----^^--------^  ^^   ^
   Philips MR   scanner patient  study    recon echo

Philips Interra 8.x naming convention:

                                     series  slice dynamic
                                         vv   v     v
1.3.46.670589.11.5406.9.955073100000002870301.3.1.1.1.0.0.2
^--------------^ ^----^ ^-----^^--------^ ^^   ^
   Philips MR   scanner patient study    recon echo

Philips Achieva naming convention:

                         study                count*
                          v--v                 v-v
1.3.46.670589.11.5702.5.0.4644.2011122013510204144
^--------------^ ^------^      ^--------------^
   Philips MR    scanner          date/time
* this number increments but bears no relation to the image or phase number.

GE Signa naming convention:

                    scanner                 count*
                   v--------v                v-v
1.2.840.113619.2.5.1762527352.1600.969534116.278
^----------------^            ^------------^
    Signa    MR               study/series**
* this number increments but bears no relation to the image or phase number. It increments through multiple series until reaching 999 then resets to 1 and the field to the left increments by 1.
** this number changes with exam but otherwise increments only when the image number goes over 999.
Because of this GE images can't be identified as to study, series or image from the DICOM filename (which is the UID).

Siemens Magnetom naming convention is:

   Siemens MR            series date         slice
v-----------------v       v------v            v-v
1.3.12.2.1107.5.2.6.21601.20001003125935000022329
                    ^---^         ^----^    ^^
           system serial number  ser time  series