A DICOM viewer opens a study. A PACS receives, stores, indexes, displays and shares every study your machines produce. This comparison explains what each covers, what each costs you in effort, and the point at which a centre outgrows a viewer.
A DICOM viewer is for one person opening one study at a time: a doctor reading a CD a patient brought in, a radiologist checking a scan sent as a file, a student learning anatomy. It is free or cheap, installs on a laptop, and does that job well.
A PACS is for a centre that produces studies every day and has to find them again, get them read, attach reports and send them to referrers. If you own a modality, you will end up needing the archive, the worklist and the sharing. A viewer is one part of a PACS; it is not a substitute for it.
The viewer reads DICOM files from a folder, a CD or a USB stick and displays them with the tools a reader expects: slice scrolling, window and level, zoom, measurement, sometimes multi-planar views. It does not receive images from a machine over the network, it does not keep a database of patients and studies, and it does not know who the referring doctor is. When you close it, the study is wherever the file was. Several capable viewers are free for personal use, and many radiologists keep one installed for exactly that reason.
A PACS runs a DICOM server that your CT, MRI, X-ray or ultrasound machine sends to automatically at the end of each scan. It stores the study, indexes it by patient, date and modality, shows it in a viewer, holds the report against it and gets the result to the referrer. The viewer inside a PACS is opened from the patient list, not from a file. In a browser-based PACS such as AuraPACS nothing is installed; the radiologist opens the study from any laptop. The guide What is PACS covers the four jobs in more detail.
The confusion comes from the fact that the viewer is the only part a doctor sees. The archive, the worklist and the sharing run in the background, which is why a centre can run on a viewer for a year before the gaps show.
| Criterion | DICOM viewer alone | PACS |
|---|---|---|
| What it covers | Opening and reading a study from a file, CD or folder | Receiving from the machine, archiving, patient index, viewer, reporting, sharing |
| Deployment | Installed on one computer; some run in a browser from an uploaded file | A server at the centre, in the cloud, or a hybrid node plus a cloud layer |
| Cost model | Often free for personal use; paid versions licensed per computer | A licence you own, a subscription, or per-study charges; ask what you keep if you stop paying |
| Who runs it | The doctor who installed it | The centre; the vendor handles setup, the front desk and technicians use it daily |
| Finding an old study | Only if you know which folder or CD it is on | Search by name, ID, date or modality; prior studies appear next to today's |
| Getting the report to the referrer | Not part of the viewer; email or print separately | PDF attached to the study; secure link by WhatsApp or email |
| When it wins | One doctor, occasional studies, reading media patients bring in | Any centre that owns a modality and produces studies daily |
| When it loses | The moment you need last year's scan or have to send today's to three people | A single doctor with no machine, or a centre that only ever reads outside CDs |
There are honest cases where a viewer alone is the right choice. A consultant physician who receives CDs from outside centres and needs to look before referring on. A small clinic with no modality that reads outside reports. A teaching setting. In each of these, buying a PACS would be paying for an archive with nothing to archive.
There is also a middle position: a centre that has a modality but sends every study to an outside reporting service. It still needs an archive and a worklist locally, because the machine has to send somewhere and the front desk has to find the study when the patient returns. See the AuraPACS viewer page for what a browser viewer inside a PACS looks like, and PACS vs cloud storage if your current answer is a shared folder.
No. A viewer displays a study; it does not receive from the machine, index patients, hold reports or share studies. A viewer is one component of a PACS. A centre with its own modality will need the other components within months.
For reading a study someone has handed over on a CD or as files, yes; many are excellent. For daily reporting at a centre, the missing parts are the worklist, the patient history and the report workflow, not the image tools.
Yes. Every PACS has a viewer, opened from the patient list. In AuraPACS the viewer runs in the browser with slice scrolling and window and level, so nothing is installed on the reading laptop.
Even one machine produces studies every day. A small on-premise or hybrid PACS gives the clinic automatic receive, a searchable archive and a way to send the report to the referrer. See PACS for diagnostic centres.
Yes, and many centres do. The cost of waiting is the studies produced in between, which sit on CDs or a drive and have to be imported later if you want them searchable. Start the archive as early as you can.
No. DICOM is the standard your machines already speak. You buy software that uses it: a viewer, a PACS, or both. The guide What is DICOM explains the standard.
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