Patient Care and Safety
Identification and consent
Two independent identifiers - name plus date of birth or medical record number - must be confirmed before every examination; room or bed number is never an identifier. Informed consent is a process with three elements: patient capacity, disclosure of risks, benefits, and alternatives, and voluntariness. The sonographer typically verifies that consent exists rather than obtaining it, and never coerces.
Bioeffects and output
Diagnostic ultrasound has two main mechanisms: heating, indexed by the thermal index (TI), and inertial cavitation, indexed by the mechanical index (MI). The output display standard shows both. FDA-recommended limits are TI ≤ 1.0 and MI ≤ 1.9 for general imaging; ophthalmic imaging is capped at MI ≤ 0.23. ALARA means using the lowest output and shortest dwell time that still produce a diagnostic study. Reduce acoustic output first; receiver gain changes display brightness only and does not change patient exposure.
Occupational and procedural safety
Occupational dose is controlled by time, distance, and shielding. Intensity falls with the square of distance, so doubling your distance from the source quarters the exposure. Standard precautions apply to all patients; sterile technique applies to invasive procedures. Good ergonomics - neutral wrist, relaxed shoulder, bed at proper height - prevents the repetitive-strain injuries common in sonography.
Trap: questions swap TI and MI, or claim that increasing receiver gain raises exposure.
Rule of thumb: if the image is too dark, raise receiver gain, not output; if TI exceeds 1.0 or MI exceeds 1.9, reduce output and shorten the exam.