Why Does an MRI Take So Long? What Really Happens Inside the Machine (2026 Guide)

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Introduction

Your doctor has prescribed an MRI scan. You have looked up the price, found a center, and booked your appointment. But there is still one question sitting at the back of your mind that nobody has properly answered.

Why does an MRI take so long? And what actually happens once you are inside that machine?

This is one of the most common questions patients ask before their first MRI scan in Pune — usually right before the appointment, when the nervousness sets in. An X-ray takes seconds. A CT scan takes a few minutes. But an MRI? You are told to expect 20 minutes, sometimes 40, lying still inside a tube-shaped machine that makes loud, strange noises.

It sounds intimidating if nobody explains it properly. So let us explain it properly.

This guide breaks down exactly why MRI scans take the time they do, what happens at every stage inside the machine, and why none of it is something to be afraid of.

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Why Does an MRI Take Longer Than an X-Ray or CT Scan?

To understand why an MRI scan takes time, it helps to understand how it actually works — and it is genuinely interesting, not just technical jargon.

An X-ray and a CT scan both use radiation to capture an image almost instantly, similar to how a camera takes a photograph. The image is captured in a fraction of a second.

An MRI works completely differently. It uses a strong magnetic field and radio waves to align and then read signals from water molecules in your body’s tissues. The machine has to send out these radio wave pulses and then “listen” for the signal that comes back, repeating this process many times in slightly different ways to build up a detailed picture, layer by layer.

This is why an MRI scan takes longer — it is not capturing one instant image like a camera. It is building a highly detailed 3D map of your tissue, one data slice at a time. The trade-off is worth it: MRI shows soft tissue detail — muscles, ligaments, brain tissue, spinal nerves — far more clearly than an X-ray or CT scan ever could.

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How Long Does an MRI Scan Actually Take?

The exact MRI scan time depends on the body part being examined and how many sequences the radiologist needs to capture. Here is a realistic breakdown:

Type of MRI Scan	Approximate Time
Brain MRI	15 – 20 minutes
Spine MRI (per region)	20 – 25 minutes
Knee or Joint MRI	20 – 25 minutes
Shoulder MRI	20 – 30 minutes
Abdominal MRI	25 – 35 minutes
MRI with Contrast	Add 10 – 15 minutes
Whole Body MRI	45 – 60 minutes

If your scan involves contrast dye, additional time is needed for the IV injection and the contrast sequences themselves. Your total time at the centre — including paperwork, preparation, and the actual scan — usually works out to about 45 minutes to an hour for a routine MRI scan in Pune.

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What Happens Step by Step Inside the MRI Machine

Here is the part most patients actually want to know — what really happens once you are lying on that table.

Step 1: Getting Positioned

Once you are ready, the radiographer helps you lie down on a padded table. Depending on the body part being scanned, a coil is placed around or near that area — a head coil for a brain MRI, a knee coil for a knee MRI, and so on. These coils help capture a clearer signal from that specific part of your body.

You will be given earplugs or headphones at this stage, and sometimes a small panic button you can press if you need the radiographer’s attention during the scan.

Step 2: The Table Slides Into the Scanner

The table then slowly moves into the MRI machine. Contrary to what many people imagine, the scanner is open at both ends — it is a tube, not a sealed box. For most scans, only the body part being examined needs to go inside; you are often not fully enclosed.

Step 3: The Scanning Begins

This is where the actual time adds up. The machine runs through a series of “sequences” — each one is essentially a different set of magnetic pulses designed to capture a particular type of detail. A typical brain MRI might involve five or six different sequences, each lasting two to five minutes.

During each sequence, you will hear loud tapping, knocking, buzzing, or humming sounds. This is completely normal — it is the sound of the machine’s magnetic coils switching on and off rapidly. Some patients describe it as similar to a washing machine or construction noise. It can be startling the first time, but it is harmless.

Between sequences, there are often short pauses of silence. Do not assume the scan is over during these gaps — more sequences may follow.

Step 4: Staying Still Is the Real Job

The only thing required of you during an MRI scan is to remain still. Movement — even small movements like swallowing hard or shifting your shoulder — can blur the images for that sequence, sometimes requiring it to be repeated.

This is also why the scan takes the time it does. A repeated sequence due to movement adds extra minutes. Patients who manage to relax and breathe normally tend to have shorter, smoother scans than those who tense up.

Step 5: Coming Out

Once all the required sequences are completed, the table slides back out. The radiographer removes the coil, and you can sit up. There is no recovery time needed for a standard MRI — you can get up and leave immediately.

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Why Do MRI Machines Make So Much Noise?

This question comes up almost as often as the one about scan time. The noise is not a malfunction — it is a normal and expected part of how an MRI machine works.

Inside the machine, there are gradient coils that rapidly switch electrical currents on and off to create small variations in the magnetic field. This rapid switching causes the coils to vibrate against their mountings, producing the tapping, knocking, and buzzing sounds you hear.

Different sequences produce different sounds — some are rhythmic and tapping, others are more like a continuous buzz or hum. The loudness varies depending on the type of scan and the specific MRI machine being used.

At our partner MRI centres in Pune, earplugs or noise-cancelling headphones are provided before every scan to make this part of the experience far more comfortable.

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Does an MRI Scan Hurt?

No. An MRI scan itself is completely painless. There is no radiation, no cutting, and no physical sensation from the magnetic field or radio waves.

The only mildly uncomfortable parts for some patients are:

Lying still in one position for an extended period, which can occasionally cause minor stiffness, especially for patients with existing back or neck pain.

The IV injection for a contrast MRI — a brief pinch, similar to a routine blood test.

Some patients feel a sensation of warmth in the area being scanned during certain sequences. This is normal and not a cause for concern.

If you experience any genuine discomfort during the scan, you can communicate with the radiographer at any point through the intercom or panic button, and the scan will be paused immediately.

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What If I Cannot Stay Still for That Long?

Staying still for 20 to 40 minutes is a genuine concern for some patients — particularly those with chronic pain, restless leg issues, or young children needing a scan. Here is what can help:

Use the restroom before the scan begins so you are not dealing with that discomfort during the procedure.

Get into a comfortable position before the scan starts and mention any pain points to the radiographer — they can often adjust positioning with extra cushioning.

Practice slow, steady breathing throughout. Closing your eyes and mentally focusing on something calming can make the time pass faster than expected.

For patients with severe anxiety or genuine difficulty remaining still, mild sedation can be arranged on the advising doctor’s recommendation. Mention this when booking your MRI scan in Pune so the centre can prepare accordingly.

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Why Some MRI Scans Take Longer Than Others

Not every MRI scan takes the same amount of time, and there are clear reasons for the difference:

More sequences needed A brain MRI looking for multiple types of abnormalities may require more sequences than a straightforward knee MRI, adding to the total scan time.

Contrast injection If your doctor has prescribed a contrast MRI, additional time is needed for the IV line placement and the post-contrast imaging sequences.

Multiple body regions If your prescription covers more than one area — for example, both cervical and lumbar spine — the total time naturally increases since each region requires its own complete set of sequences.

Patient movement As mentioned earlier, any movement during a sequence may require it to be repeated, which adds time to the overall scan.

Machine type A 3 Tesla MRI can sometimes complete certain sequences faster than a 1.5 Tesla MRI due to its stronger signal, though this varies depending on the specific scan being performed.

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