8.4 CT Informatics — PACS, DICOM, Networking & Downtime Procedures

Why CT Informatics Matters

The final Image Evaluation and Archiving sub-item on ARRT's outline is Informatics: information systems (HIS, RIS, EMR, EHR), hard/electronic copy, networking (PACS/MIMPS, DICOM, security and confidentiality, teleradiology), and downtime procedures. This is a small slice of the blueprint by scored-item count, but it maps directly to some of the most common real-world failure points in a CT department — mismatched patient identifiers, lost or misrouted studies, HIPAA exposure, and unplanned network outages — which is exactly why ARRT expects entry-level technologists to know this vocabulary cold.

Enterprise Information Systems

Several overlapping acronyms are frequently confused on the exam. The clearest way to keep them straight is by scope — facility-wide administration vs. department-level imaging workflow vs. clinical chart vs. cross-institution record:

The EMR vs. EHR distinction is a classic exam nuance: an EMR is essentially a digital replacement for a single facility's paper chart, while an EHR is explicitly designed for interoperability — the same patient record can, in principle, be accessed and updated by different organizations across a continuum of care.

Networking, Archiving, and Format Standards

• PACS (Picture Archiving and Communication System): the networked system that stores, retrieves, distributes, and displays digital images across a facility, having replaced film-based archives. ARRT's outline pairs PACS with related multi-institution or vendor-neutral image-management platforms that extend PACS-style storage and retrieval across broader networks.
• DICOM (Digital Imaging and Communications in Medicine): the international standard format and transmission protocol that defines how medical images and their associated data — patient name and ID, study date, acquisition parameters — are stored and exchanged so that equipment from different manufacturers can interoperate. Every CT image carries an embedded DICOM header with this metadata, which is why correct patient demographic entry at the console matters: an error there propagates into every downstream system.
• Hard/electronic copy: physical film printing (largely legacy today) versus burning a study onto a CD or other portable media for patient take-home, referring-provider transfer, or outside second-opinion review when direct PACS access is unavailable.
• Teleradiology: transmitting CT images to a radiologist at a remote location for interpretation, including after-hours or overnight third-party coverage arrangements. Every teleradiology transmission carries the same security and confidentiality obligations as an on-site read.
• Security and confidentiality: HIPAA-governed access controls, audit trails, and minimum-necessary data-sharing principles apply to every image transmitted, archived, printed, or copied — a CD burned for a patient, a teleradiology transmission, and a PACS query are all subject to the same rules.

Downtime Procedures

Downtime procedures are the documented backup workflow a department follows when PACS, RIS, or the broader hospital network becomes unexpectedly unavailable. ARRT tests this specifically because equipment and network outages are common, and patient imaging — especially trauma and emergent studies — cannot simply stop while IT resolves the issue. Key elements every technologist should be able to execute without hesitation:

1. Continue scanning using local console storage, since acquisition itself does not depend on PACS connectivity.
2. Manually log patient and exam identifiers (a paper downtime log or requisition) because automated order-matching through RIS is unavailable during the outage.
3. Once systems are restored, reconcile and transfer every locally stored study into PACS, verifying against the downtime log that no studies were lost, duplicated, or misfiled to the wrong patient.
4. Follow the facility's written, unit-specific downtime policy — every CT department is required to maintain one, and technologists are expected to know where to find it and how to execute it immediately, not learn it for the first time during an actual outage.

Exam Scenario

Mid-overnight shift, the hospital's PACS connection fails department-wide while a trauma CT of the head and cervical spine is in progress. The technologist completes the acquisition, stores the images locally on the scanner console, and manually documents the patient's name, medical record number, and exam performed on a paper downtime log per the department's written policy — rather than delaying emergent trauma imaging while waiting for the network to return. Once PACS connectivity is restored an hour later, the technologist pushes the locally stored study to PACS and cross-checks it against the downtime log to confirm every exam performed during the outage was correctly transferred and matched to the right patient before closing out the log.