Equipment and Imaging Informatics
Acquisition hardware
Computed radiography uses a photostimulable phosphor plate. Direct digital radiography uses indirect conversion (caesium iodide scintillator with an amorphous silicon photodiode array) or direct conversion (amorphous selenium photoconductor). Thin-film transistor arrays read out the charge. Key detector metrics are fill factor, detective quantum efficiency (DQE), modulation transfer function (MTF), pixel pitch and bit depth.
Informatics
DICOM governs image objects and network services such as store, query/retrieve, print and modality worklist. HL7 governs clinical messaging such as orders and reports. The RIS manages scheduling and reporting, the HIS holds the master patient record, and PACS stores and distributes images. Integration profiles from IHE define consistent workflows. The modality worklist pulls demographics from the RIS to prevent transcription errors. Images must reach PACS before the patient leaves the department, and rejected images should be flagged rather than deleted.
Dose and exposure indices
The exposure index and deviation index relate receptor exposure to a validated target. They describe exposure at the detector, not patient dose. Dose-area product, CTDIvol and dose-length product are the actual dose metrics.
Traps
Confusing exposure index with dose. Using lossy compression for primary diagnosis where lossless is required. Having no PACS downtime procedure. Believing DICOM schedules appointments.
Rule of thumb
Each deviation index unit of 1.0 corresponds to roughly a 26% change in receptor exposure; a deviation index of +3 means about twice the target exposure, and −3 about half.