I beleive Imacon's have only been SCSI or Firewire. I've never heard of any that had a USB interface. SCSI-USB converters generally will not work, especially on a Mac.
If you have a Mac, the SCSI scanners will only work with systems up to Snow Leopard. They are *not* supported in Lion or any future versions. Best/easiest thing to do is to invest a couple of hundred dollars for an old Mac mini, iBook G4, or similar ancient machine (does not have to have an Intel processor), and dedicate that to your scanner.
If you use a desktop machine, a SCSI card may be a good option. Otherwise, you'll need the Ratoc FR1SX SCSI-Firewire adaptor. It's recently been discontinued by the manufacturer, so make sure you can either source one on eBay before you buy the scanner, or only buy a scanner that comes with the adaptor.
--John