rTMS, iTBS, and Accelerated TMS

rTMS, iTBS, and accelerated TMS are three terms that describe how magnetic pulses are delivered during a TMS session — not different brands, devices, or diagnoses. rTMS refers to a steady, repeating pulse pattern delivered over a longer session; iTBS refers to a patterned, theta-burst delivery that compresses a comparable session into a few minutes; and accelerated TMS refers to scheduling multiple sessions in a single day over a compressed number of days, an approach generally made possible by the short session time of iTBS. This article defines each term clearly and shows how they relate to one another, without making claims about comparative effectiveness.

What does rTMS mean?

rTMS stands for repetitive transcranial magnetic stimulation. It describes the original and longest-established way of delivering TMS: magnetic pulses are applied in a steady, repeating pattern — commonly described in terms of a pulse frequency, such as 10 Hz — over a single session that typically runs in the range of about 19 to 37.5 minutes, depending on the specific parameters used. A standard course of rTMS is usually delivered once per day, five days a week, over a period of roughly six weeks. "rTMS" is sometimes used loosely to refer to TMS in general, but more precisely it refers to this specific steady-pulse delivery pattern, as distinct from theta-burst delivery.

What does iTBS mean?

iTBS stands for intermittent theta-burst stimulation. It describes a patterned way of delivering pulses in short rhythmic bursts, modeled after naturally occurring theta-wave activity in the brain, rather than the steady single-pulse-per-cycle pattern used in standard rTMS. This patterned delivery allows a session to be completed in roughly three minutes, compared to the much longer session time associated with standard rTMS. iTBS can be delivered on the same once-daily schedule as standard rTMS, or its short session length can be used to schedule multiple sessions per day — which is the basis for accelerated TMS protocols, described below.

What does accelerated TMS mean?

Accelerated TMS describes a scheduling approach, not a stimulation pattern in its own right: it means delivering multiple TMS sessions per day, spaced by set intervals, over a compressed number of days rather than one session per day over several weeks. Because a single iTBS session takes only a few minutes, a clinic can fit several sessions into one day, allowing a full course that would otherwise take roughly six weeks to be completed in a much shorter span of days. Accelerated protocols are almost always built around iTBS specifically, because standard rTMS's longer per-session time makes multiple daily sessions far less practical to schedule. In short, iTBS is what makes accelerated scheduling possible, and accelerated TMS is one way iTBS's short session time can be used.

How are these three terms related?

rTMS and iTBS both describe methods of pulse delivery, and accelerated TMS describes a scheduling structure that can be layered on top of iTBS. It can help to think of it as two independent questions: how are the pulses patterned (steady rTMS versus theta-burst iTBS), and how is the course scheduled (once daily over several weeks versus multiple sessions per day over a compressed number of days). A course can be standard rTMS delivered once daily, standard iTBS delivered once daily, or iTBS delivered on an accelerated multi-session-per-day schedule. Accelerated rTMS scheduling is not typically how the term is used in practice, since rTMS's longer session length makes multiple-times-per-day scheduling impractical for most clinics.

How do the three compare at a glance?

rTMS

iTBS

Accelerated TMS

What it describes

A pulse delivery pattern

A pulse delivery pattern

A scheduling structure

Typical session length

~19–37.5 minutes

~3 minutes

Built from multiple short (iTBS) sessions per day

Typical schedule

Once daily, ~5 days/week

Once daily, or used in accelerated scheduling

Multiple sessions per day, compressed into days rather than weeks

Typical course length

~6 weeks

Similar to rTMS if once-daily; much shorter if accelerated

Days, rather than weeks

Are these terms tied to a specific brand or device?

No. rTMS, iTBS, and accelerated TMS describe how a treatment is delivered, and multiple TMS devices from different manufacturers are cleared to deliver one or more of these protocols. A specific device's cleared indications determine which of these delivery methods it can be used for; see FDA Cleared TMS Devices Compared for a comparison of devices for how to verify a specific device's cleared indications. Ampa One, for example, supports both standard-length protocols and an accelerated ONE-D protocol built around iTBS, discussed further in business-05-accelerated-tms-as-a-differentiator.md.

Frequently Asked Questions

Is iTBS a type of accelerated TMS? Not exactly. iTBS is a pulse delivery pattern; accelerated TMS is a scheduling approach that uses iTBS's short session length to fit multiple sessions into a single day. iTBS can be delivered on a standard once-daily schedule without being "accelerated."

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Is accelerated TMS a specific FDA-cleared protocol, or a general term? "Accelerated TMS" is a general descriptive term for multi-session-per-day scheduling. Specific accelerated protocols receive their own regulatory clearance for specific indications, which should be verified for any given device; see regulatory-04-how-accelerated-tms-protocols-earn-clearance.md.

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Why can't standard rTMS easily be delivered on an accelerated schedule? Standard rTMS sessions run up to about 37.5 minutes each, so fitting several sessions into a single day with adequate spacing between them is far less practical than with iTBS's roughly three-minute sessions.

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Does a shorter iTBS session mean less stimulation is delivered? iTBS is designed to deliver a comparable overall stimulation dose to standard rTMS through its patterned, compressed delivery, rather than simply reducing the amount of stimulation. See clinical-05-itbs-vs-standard-rtms.md for a fuller comparison of the two delivery patterns.

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How long does a full accelerated TMS course typically take? Accelerated courses are generally designed to compress a course that would otherwise span roughly six weeks into a period of days, though the exact schedule depends on the specific protocol and clinic.

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Where can I read more about how these delivery methods compare or how devices are cleared to offer them? See clinical-05-itbs-vs-standard-rtms.md for a direct comparison of rTMS and iTBS, business-05-accelerated-tms-as-a-differentiator.md for how accelerated scheduling is used by practices, and fda-cleared-tms-devices-compared.md for how different devices are cleared for these protocols.

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This glossary article is for general educational purposes only, describes terminology rather than clinical guidance, and does not constitute medical advice.

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