PACS & DICOM Viewer Simulator

Modality

Slice

Instance 1 / 60

Window / Level

Window Center (WC) 40

Window Width (WW) 400

View

Zoom 100%

DICOM metadata

Patient ID

–

Modality

Study Instance UID

–

Series Instance UID

–

SOP Instance UID

–

Rows × Cols

256 × 256

Pixel spacing

0.70\0.70 mm

Slice location

0.0 mm

Measurement

–

How it works

A DICOM image stores raw pixel values, not pre-rendered brightness. For CT those values are Hounsfield Units (HU): −1000 is air, roughly 0 is water, and dense bone runs above +700. A PACS viewer maps that huge numeric range onto the 256 shades a screen can show using window center (level) and window width — everything below the window turns black, everything above turns white, and the band in between is stretched linearly:

display = clamp((HU − (WC − WW/2)) / WW, 0, 1) × 255

Narrow window (soft tissue, WW≈400) — small HU differences between organs become visible shades of grey.
Wide window (lung, WW≈1500) — a huge HU range is compressed to show alveolar air alongside vessels.
Bone window — the level shifts high so only dense cortical bone is bright, soft tissue collapses to near-black.
Slice scrolling mimics moving through a CT/MRI/ultrasound stack — each 2D image is one Instance inside a Series inside a Study, the three UIDs DICOM uses to keep exams organised.
PACS network — the modality (scanner) sends the finished study to the PACS server over a DICOM association (C-STORE); a radiology workstation later queries and retrieves it (C-FIND / C-MOVE) for reading.

Real-world relevance: every hospital radiology department runs on exactly this loop — acquisition, window/level rendering, and network storage/retrieval under the DICOM standard — regardless of vendor.

Scroll = change slice · Drag = pan · Measure tool = click two points

PACS network — DICOM study transfer