What DICOM actually is
DICOM (Digital Imaging and Communications in Medicine) is a standard managed by NEMA. It specifies how medical images are stored on disk and how they are exchanged between machines — workstations, scanners, PACS servers, archives.
Every DICOM file has two parts: a header with metadata tags (patient demographics, study date, scanner model, acquisition parameters, slice position) and the pixel data itself. Tags are identified by a (group, element) pair like (0010, 0020) for Patient ID.
How a CBCT study is structured
A single CBCT acquisition typically exports hundreds of axial slices. Each slice is its own .dcm file, numbered in sequence. Together they make up one series. Several series together make a study. Folder layout is usually something like Patient / Study / Series / *.dcm.
Some scanners also export a DICOMDIR file — an index that lets viewers load the study without scanning every file. Others embed the study in a ZIP or produce proprietary containers (like PROJ files in NewTom) that need to be converted first.
Common export pitfalls
Anonymisation stripped the study UID — you can no longer match series to report. Always anonymise in a way that keeps series-level identifiers consistent.
Slice ordering is lost after zip compression on some systems. Viewers that rely on file name ordering instead of DICOM tags will show the volume in random order. Always use a viewer that reads tag (0020, 0032) Image Position Patient.
Burned-in annotations. Some scanners put text overlays on the images. Viewers cannot remove them — better to disable burn-in during export.
Transfer syntax. DICOM supports many pixel encodings. Some older viewers cannot decode JPEG 2000 lossless CBCT — the scan looks blank. Modern browser-based viewers handle most encodings natively.
Opening DICOM without installing anything
Desktop viewers still work fine, but they are OS-specific and require install. For quick review, sharing with a patient or second opinion between specialists, browser-based viewers are easier — drag the folder in, the viewer indexes the series and shows axial, coronal, sagittal and 3D reconstructions.
CBCTHub reads standard DICOM folders, compressed archives, DICOMDIR indexes, and the main proprietary containers (with conversion). Processing is local — the patient data never touches a server unless the user explicitly shares a link.