Types of Ultrasound Probe: Linear, Convex, Phased Array and Endocavity

General product information only, not medical advice. Which probe a clinician uses for a given patient is a clinical decision.

Overview: what the types of ultrasound probe are

An ultrasound probe is also called a transducer, so “ultrasound probe types” and “ultrasound transducer types” are the same question. The probe is the handheld part of an ultrasound machine that sends sound into the body and receives the echoes. The main types differ in shape, in the range of sound frequencies (MHz) they work across, and in how deep they can image: higher frequency generally gives finer detail but shallower reach, and lower frequency reaches deeper with less detail.

In US regulation, 21 CFR 892.1570 defines a diagnostic ultrasonic transducer as a device made of a piezoelectric material that converts electrical signals into acoustic signals and acoustic signals into electrical signals, intended for use in diagnostic ultrasonic medical devices. It is a Class II device (FDA product code ITX, Radiology panel), per the openFDA device classification database, checked 2026-10-30. In its guidance on marketing clearance of diagnostic ultrasound systems and transducers, FDA lists the transducer type the manufacturer declares, with examples such as mechanical sector, rectangular phased array, curved linear array and annular phased array.

Types table

Frequency ranges below come from two separate sources and do not agree exactly. Treat any single range as approximate: the working range of a specific probe is whatever its manufacturer states.

Probe type	What it is and typical use	Range, Loyola Stritch teaching deck	Range, Advanced Ultrasound (vendor)	Limits
Linear	Flat array. Vascular, musculoskeletal, soft tissue and ocular imaging (Loyola).	5-16 MHz	5-15 MHz	Higher resolution but shallow: scan depth about 6 cm and a scan area limited to the probe size (Loyola); not well suited to deep abdominal imaging (vendor).
Curvilinear (convex)	Curved array with a larger footprint. Thorax, abdomen and pelvis (Loyola).	2-5 MHz	2-7 MHz	Deeper reach (scan depth about 30 cm, Loyola) with decreased resolution; lower detail than linear (vendor).
Phased array (sector)	Small footprint. Described as ideal for cardiac studies because it fits between ribs (Loyola).	1-5 MHz	2-5 MHz	Decreased resolution (Loyola); some loss of spatial resolution (vendor).
Endocavitary	Small probe for OB-gyn and oral cavity use (Loyola).	8-15 MHz	5-9 MHz	Shallow reach (scan depth about 13 cm, Loyola). Needs high-level disinfection and single-use covers (vendor); see the care section.
Microconvex	Small curved array, described for pediatric, neonatal and veterinary imaging.	Not listed	4-8 MHz	Frequency range given by the vendor; confirm the maker’s specification.
Continuous-wave Doppler (“pencil”)	Doppler probe that does not produce a grayscale image.	Not listed	Not listed	Needs an imaging probe to show anatomy (vendor).

Sources for the table: Loyola University Chicago Stritch School of Medicine point-of-care ultrasound lecture deck (educational; values as stated there) and the Advanced Ultrasound page on types of ultrasound probes (a vendor; values attributed to it). Both checked 2026-10-30; full links are in the Sources section.

Choosing by depth and anatomy

Which probes are described for shallow structures?

Linear probes. Both sources place them at the high-frequency end (about 5-16 MHz), which suits structures close to the skin such as vessels, muscle, tendon and the eye, at the cost of depth.

Which probes are described for deeper structures?

Curvilinear and phased array probes work at lower frequencies (about 1-7 MHz across the two sources) and reach deeper. The curvilinear probe has a larger footprint and is described for thorax, abdomen and pelvis; the phased array has a small footprint that fits between ribs, which is why the Loyola deck calls it ideal for cardiac studies.

What about small-footprint or internal imaging?

Endocavitary probes trade depth for resolution: the Loyola deck gives a higher-frequency range and about 13 cm scan depth. Because they are used inside the body, their reprocessing requirements differ, covered below.

For the machine the probe connects to, see ultrasound machine cost.

What to check on the label and in the maker’s instructions

• The stated frequency range. Because published ranges differ, the label and the manufacturer’s specification for that exact probe are the reference, not a generic chart.
• The declared transducer type. FDA’s guidance expects the transducer type (for example curved linear array or rectangular phased array) to be identified by the manufacturer.
• Cleaning and disinfection instructions. FDA’s guidance expects validated cleaning and disinfecting labeling for endocavity-use devices, along with information on appropriate transducer covers.
• Intended use. Use the probe only for the applications its manufacturer states. For background on how devices are defined, see what is a medical device.

Care, covers and reprocessing

FDA’s guidance (Appendix E) sorts probes by how they are used. Non-critical probes are cleaned and undergo low-level disinfection between patient uses. Semi-critical probes call for sterilization between uses whenever feasible, and high-level disinfection is the minimum acceptable. FDA recommends a sterile sheath for every semi-critical use, states that endoscopic, rectal and transvaginal probes should be used with a single-use sterile sheath, and adds that using a sheath does not change the type of processing required and that sheaths can fail during use in ways that may not be visible. For cover details, see the guide to the ultrasound probe cover.

FAQ

Do you need ultrasound gel with a Doppler?

Gel is placed between the probe and the skin to remove air so sound can pass effectively (Advanced Ultrasound). None of the sources cited on this page sets a rule specific to Doppler probes, so follow the instructions for the particular device. The probe cover guide has its own answer on gel, and the fetal Doppler guide covers that device.

Are an ultrasound probe and a transducer the same thing?

Yes. Probe is the everyday term; transducer is the regulatory and technical term, as in 21 CFR 892.1570.

Why do two sources give different MHz ranges for the same probe type?

Ranges are manufacturer- and model-specific, and teaching materials round them. The table shows both sources so the difference is visible.

Related supplies: browse the diagnostic, monitoring and imaging category at lac.us.

Sources

All sources below were checked on 2026-10-30.

• FDA, Marketing Clearance of Diagnostic Ultrasound Systems and Transducers, guidance issued 2023-02-21: https://www.fda.gov/media/71100/download
• 21 CFR 892.1570, Diagnostic ultrasonic transducer: https://www.law.cornell.edu/cfr/text/21/892.1570
• openFDA device classification, product code ITX: https://api.fda.gov/device/classification.json?search=product_code:ITX
• Loyola University Chicago Stritch School of Medicine, point-of-care ultrasound introduction lecture (PDF): https://www.meddean.luc.edu/lumen/meded/vc/point_of_care_ultrasound_vc/2022-2023%20Labs/SHBIntrotoUSLecture_PP.pdf
• Advanced Ultrasound (vendor), Types of ultrasound probes: https://advancedultrasound.com/types-of-ultrasound-probes/