Digital Radiography (Fixed Room)
Dedicated fixed X-ray rooms for general radiography — chest, abdomen, extremities, spine. Wall-mounted + table-mounted detectors + ceiling- or floor-mounted X-ray tubes. Successor to computed radiography (CR, phosphor-plate cassettes) and analog screen-film.
The most-ordered imaging exam worldwide — chest X-ray volume dwarfs every other imaging modality combined. DR room throughput matters economically.
Physics
- X-ray tube generates beam at 40–150 kVp, typically 50–400 mA·s depending on anatomy.
- Beam passes through patient (differential absorption).
- Flat-panel detector converts remnant photons to digital signal:
- Direct conversion (a-Se): X-rays → electrical signal via selenium layer
- Indirect conversion (CsI): X-rays → light (cesium iodide scintillator) → electrical signal (amorphous silicon photodiode array)
- Image processed + displayed on workstation, sent to PACS.
CR vs DR
- CR (legacy) — phosphor plate cassettes loaded into readers. Plates must be physically carried between shots. Workflow slow, image quality adequate.
- DR (current) — flat-panel detector captures directly. Image available in ~seconds. Workflow fast.
- Wireless DR — portable detectors move between room and mobile units. Fleet-wide detector interoperability is a real operational benefit.
Key specs
- Detector type — CsI (indirect, typically higher DQE) vs a-Se (direct)
- Detector size — 14×17 in (35×43 cm) standard, 17×17 in square, smaller for extremity
- Wireless vs tethered — wireless preferred in modern rooms
- Tube mount — ceiling-suspended (most flexible) vs floor-mounted
- Generator — 50–80 kW typical
- Auto-positioning — tube-tracking sensors reduce setup time
- Dose reduction software — vendor-specific
Clinical applications
- Chest X-ray (most common imaging exam)
- Abdominal X-ray (obstruction, free air)
- Extremity (fractures, alignment, joints)
- Spine (scoliosis, disc-height assessment)
- Pelvis
- Pediatric
- Trauma supplementation (mobile DR often replaces for emergent cases)
Systems
- Siemens Ysio Max
- GE Optima XR656
- Philips DigitalDiagnost C90
- Fujifilm FDR Smart X
- Canon Medical Ultimax-i (fluoro + DR hybrid)
- Carestream DRX-Evolution
Service reality
- Panel battery aging — wireless DR panels lose runtime over 3–4 years
- Scintillator aging — CsI efficiency drops; measured in DQE loss over years
- Tube anode — end-of-life via bearing noise
- Ceiling-tube cable tracks — long-term wear
- Generator — HV tank oil issues rare but serious
Regulatory
- State radiation registration + annual physicist survey
- ACR diagnostic radiology accreditation for reimbursement on advanced exams
- MQSA analog for mammography only — general DR has less-stringent federal oversight