Linear, curvilinear or phased array?

Choosing the right probe is half of a good scan. The choice is a trade between detail and depth.

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The three probes

Linear (≈5–15 MHz): flat face, rectangular image, fine detail but shallow — vessels, nerves, pleura, needles.
Curvilinear (≈2–5 MHz): curved face, wide fan, sees deep — abdomen, pelvis, FAST, lung bases.
Phased array (≈1–5 MHz): tiny footprint that steers its beam between ribs — the heart.

The probe marker

Every probe has a marker on one side, matching a dot on the screen. In emergency and radiology convention the screen dot is on the left: marker to the patient’s head in long axis, to the patient’s right in transverse. Cardiology traditionally flips this.

Real scans

Normal compressible vein: internal jugular (clip). A normal internal jugular vein is completely flattened by light probe pressure, while the artery stays round. This is how a vein without clot behaves. Gillman L, Blaivas M, Lord J, Al-Kadi A, Kirkpatrick A · CC BY 2.0 · source

Normal RUQ (Morison's pouch) view — Liver and right kidney touch with no black stripe between them: a negative (normal) RUQ FAST window. — **Normal RUQ (Morison's pouch) view.** Liver and right kidney touch with no black stripe between them: a negative (normal) RUQ FAST window. Drahreg01 · CC BY-SA 3.0 · source

Normal parasternal short axis (papillary level) (clip). Normal left ventricle cut across as a ring at the level of the papillary muscles. Has a small EchoPedia credit line. CardioNetworks: Vdbilt · CC BY-SA 3.0 · source

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FAQ

Why does high frequency give better detail?

Shorter wavelength and pulse length improve resolution, but higher frequencies attenuate faster, so they don’t reach as deep.

Related guides

Knobology: the four knobs that matterHow to set ultrasound gain, depth, focus and frequency — with a live simulator so you can turn the knobs and see what happens.
Ultrasound artifacts, explainedAcoustic shadowing, posterior enhancement, reverberation (A-lines), B-lines, mirror image and edge artifacts — why they happen and how they help diagnosis.
The FAST exam, explained by actually doing itHow to perform a FAST exam: RUQ, LUQ, pelvic and subxiphoid views, what a positive scan looks like, common pitfalls — with a live ultrasound simulator you can try.

Educational content for learners; follow local protocols and supervision. Simulated images are generated by Sonoduck’s physics model; real images are credited individually.