After an imaging unit is rigged, set, and powered up, it cannot legally or clinically be used on patients until a defined sequence of acceptance tests, physicist surveys, and regulatory filings is complete. This Article covers that gate — the work that turns a physically installed machine into an approved, registered, billable clinical asset, and the schedule and contractual logic an owner must manage to keep go-live from slipping.

This is the legal-and-quality bridge between physical installation and clinical use. It assumes the room shielding was designed (covered in the shielding and physicist Article), the equipment was delivered and ramped up (covered in the rigging Article), and the operational safety programs are being stood up in parallel (covered in the MRI-safety and radiation/contrast/infection Articles). Here the focus is verification, documentation, and authorization.

The activation gate sits between installation and first patient

Imaging differs from most construction trades in that "installed and energized" is not "ready to use." A CT or MRI that powers on and produces images may still be days or weeks away from clinical authorization. Three independent workstreams must close, in a partly sequential order, before the first patient is scanned:

1. Acceptance testing — proving the equipment performs to the purchase specification and the manufacturer's published performance criteria.
2. Physics survey / equipment performance evaluation — an independent qualified expert verifying radiation output, shielding adequacy, image quality, and dose, and signing the report that regulators and accreditors require.
3. Regulatory registration and authorization — registering the X-ray-producing machine with the state, securing or amending radioactive-material licenses (for nuclear medicine/PET), and clearing the accreditation and payer enrollment needed to bill.

These overlap but have hard dependencies: the physicist generally cannot complete a survey on a machine that has not passed acceptance and calibration; the state registration must exist before clinical use; accreditation bodies require the physics report and a clinical-image submission that itself requires patient or phantom scanning under an authorized program. Treating these as one "commissioning" lump is the most common scheduling error — they involve different parties (vendor, independent physicist, state agency, accreditor, payer) on different clocks.

Acceptance testing proves the machine meets the contract

Acceptance testing is the formal, witnessed verification that the delivered equipment performs to the contracted specification. It protects the owner financially: it is the basis for the punch list, for triggering final payment milestones, and for starting the warranty clock. It is normally performed by the manufacturer's field engineer, witnessed by the owner's representative — increasingly the owner's qualified medical physicist, who has standing to challenge results the vendor would otherwise self-certify.

Typical acceptance-test scope by modality includes:

• CT — CT number (Hounsfield) accuracy and uniformity, slice thickness, spatial and low-contrast resolution, noise, table indexing/positioning accuracy, laser-light alignment, CTDIvol/dose indicators against console display, and reconstruction-algorithm behavior. AAPM acceptance and quality-control protocols are the customary technical reference.
• MRI — signal-to-noise ratio, image uniformity, geometric accuracy/distortion, slice position and thickness, ghosting, gradient performance, B0 homogeneity (shim), and coil checks for every coil delivered. The ACR MRI phantom is the customary acceptance and ongoing-QC tool.
• Radiographic / fluoroscopic / interventional — kVp accuracy and reproducibility, half-value layer (beam quality/filtration), timer accuracy, mA linearity, AEC performance, fluoroscopic dose rates and last-image-hold, collimation/light-field congruence, and image-receptor/detector performance.
• Mammography — a dedicated, heavily prescribed regime under MQSA (see registration discussion below); acceptance testing is performed by a qualified physicist before any clinical use and the unit cannot operate without an MQSA certificate.
• Nuclear medicine / PET / PET-CT — gamma-camera uniformity, spatial resolution and linearity, sensitivity, energy resolution, and (for PET) calibration, normalization, and CT-to-PET co-registration accuracy, using NEMA-defined performance methods.

Acceptance testing should be written into the equipment purchase agreement with explicit, measurable criteria, the right to independent witness, and remedies for failure. Without contractual teeth, a "failed" acceptance test becomes a negotiation rather than a rejection, and the owner loses leverage exactly when a multimillion-dollar asset is underperforming.

The medical physicist's survey is the independent verification of record

Distinct from vendor acceptance, the qualified medical physicist performs an independent survey (also called an equipment performance evaluation, and for radiation-producing devices a radiation protection survey). This is the report regulators and accreditors actually rely on, and it is signed by a named, credentialed individual who carries professional accountability for it. The physicist's role here is the activation-phase continuation of the same expert who designed the shielding; whether the same individual or firm performs both is a procurement choice, but the survey must be independent of the equipment vendor.

The survey typically covers two things at once: