A sinogram in CT is the raw projection data collected during a scan, shown as a 2D plot of detector position versus projection angle. It represents X‑ray attenuation traces for each angle and is the input for image reconstruction (e.g., filtered back-projection). Sinograms help identify motion, artifacts, and missing data and are used for quality control and advanced reconstruction techniques.

A sinogram (sinography) is an imaging test that outlines a sinus tract or fistula by injecting contrast into an external opening and taking X-rays or CT images. It shows the tract’s course, length, connections to cavities or organs, presence of retained foreign bodies, and extent of infection. It helps diagnose chronic infections, osteomyelitis, post‑operative leaks and guides surgical or interventional planning.

Start by confirming patient details, side and projection. A sinogram shows a contrast-filled tract: track its origin, length, branching and any communication with cavities or deeper structures. Note nearby bone erosion, abscesses, air or foreign bodies and measure extent. Correlate findings with the clinical exam and symptoms. Always rely on the radiologist’s report for definitive interpretation and consider further imaging or ENT/surgical review if indicated.

A sinogram (fistulogram) is usually not painful; most people feel mild discomfort, pressure, or brief stinging when the catheter is placed and contrast is injected. Local anaesthetic can reduce pain, and the procedure is quick and well tolerated. Severe pain is uncommon; tell staff about allergies, infections, or increasing pain during the test so they can stop or adjust it.

Obtain informed consent, check allergies and pregnancy status, and explain risks. Clean and drape the skin; insert a small cannula or catheter into the external sinus opening using aseptic technique. Gently inject water‑soluble iodinated contrast under fluoroscopy or take serial radiographs; stop if resistance or pain. Optionally perform CT after injection. Remove catheter, dress the site, monitor for reaction or infection, and report findings.

The three main types of CT are: 1) Conventional (single‑slice) CT — acquires cross‑sectional images slice‑by‑slice for structural assessment. 2) Helical (spiral) CT — continuous rotation with table movement enabling faster, volumetric imaging and improved 3D reconstructions. 3) CT angiography (CTA) — uses intravenous contrast and timed imaging to visualize blood vessels and detect stenosis, aneurysms or emboli.