4-Tesla MRI Scanner Traps Furniture With 1,700 Pounds of Pull

How dangerous are magnetic items near an MRI magnet? — practiCal fMRI

practiCal fMRI

Steep magnetic field gradients at the scanner bore cause attractive forces to surge past 1,700 pounds, pinning ferromagnetic objects beyond any manual restraint.

AI-assisted summary of How dangerous are magnetic items near an MRI magnet? — original source. Check the original for full context.

Source published:

Key ideas

  • Prior to decommissioning a 4 Tesla MRI scanner, researchers conducted live force measurements showing how ferromagnetic objects experience extreme mechanical attraction near the magnet bore. (0:12)
  • Initial pull measurements on test objects registered between 280 and 300 pounds of force, escalating rapidly to 500 pounds within inches of movement toward the magnet opening. (0:12)
  • As larger items such as an office chair were brought near the bore, measured attraction surged through 700 and 1,300 pounds, ultimately peaking around 1,700 pounds of force. (1:48)
  • The steep field gradients at the magnet face cause rapid acceleration and oscillation of loose magnetic objects, creating pinning forces that far exceed human physical resistance. (1:48)

Detailed notes

## Background Published on YouTube by practiCal fMRI on November 13, 2010, this video documents experiments conducted on a 4 Tesla (T) research MRI magnet scheduled for decommissioning. The video description explains the safety implications of ferromagnetic objects near an MRI scanner, noting how peak magnetic field gradients at either end of the bore cause objects to rapidly accelerate and oscillate.

## TL;DR The video demonstrates the hazardous forces exerted by a powerful 4 Tesla MRI scanner on ferromagnetic items brought near its bore. Using a force-measuring setup, the experimenters track how magnetic pull increases from around 280 to 300 pounds at the outer perimeter up to 500 pounds closer to the entrance. When testing larger items such as an office chair, the attractive forces rapidly climb past 700 and 1,300 pounds. Ultimately, the items become pinned against the scanner face under roughly 1,700 pounds of force, illustrating the extreme dangers of bringing magnetic objects into an active MRI environment.

## Atmosphere & style The presentation carries an informal, hands-on experimental vibe where casual curiosity meets jaw-dropping physical force. The speakers monitor the gauge in real time with an unvarnished, observational tone that gradually shifts into mild disbelief as the force numbers climb well past manual human resistance. Watching the demonstration feels raw and cautionary, effectively capturing the invisible, unrelenting power of high-field magnetic resonance equipment.

## Bulletin - [00:12](https://www.youtube.com/watch?v=6BBx8BwLhqg&t=12s) Prior to decommissioning a 4 Tesla MRI scanner, researchers conducted live force measurements showing how ferromagnetic objects experience extreme mechanical attraction near the magnet bore. - [00:12](https://www.youtube.com/watch?v=6BBx8BwLhqg&t=12s) Initial pull measurements on test objects registered between 280 and 300 pounds of force, escalating rapidly to 500 pounds within inches of movement toward the magnet opening. - [01:48](https://www.youtube.com/watch?v=6BBx8BwLhqg&t=108s) As larger items such as an office chair were brought near the bore, measured attraction surged through 700 and 1,300 pounds, ultimately peaking around 1,700 pounds of force. - [01:48](https://www.youtube.com/watch?v=6BBx8BwLhqg&t=108s) The steep field gradients at the magnet face cause rapid acceleration and oscillation of loose magnetic objects, creating pinning forces that far exceed human physical resistance.

## Key takeaways - [00:12](https://www.youtube.com/watch?v=6BBx8BwLhqg&t=12s) Testing was performed using a high-field 4 Tesla research MRI scanner scheduled for decommissioning. - [00:12](https://www.youtube.com/watch?v=6BBx8BwLhqg&t=12s) A load-measuring gauge tracked real-time physical pull exerted by the MRI's fringe field. - [00:12](https://www.youtube.com/watch?v=6BBx8BwLhqg&t=12s) Magnetic attraction registered at 280 to 300 pounds of force at the outer perimeter of the magnet face. - [00:12](https://www.youtube.com/watch?v=6BBx8BwLhqg&t=12s) Moving an object just inches closer along the magnetic gradient increased tension to 500 pounds. - [00:12](https://www.youtube.com/watch?v=6BBx8BwLhqg&t=12s) Peak magnetic field gradients occur near the magnet faces at either end of the bore. - [00:12](https://www.youtube.com/watch?v=6BBx8BwLhqg&t=12s) Unrestrained magnetic objects tend to oscillate along the scanner bore due to entry acceleration and progressively damped directional changes. - [01:48](https://www.youtube.com/watch?v=6BBx8BwLhqg&t=108s) Force measurements quickly passed 700 pounds when testing larger ferromagnetic equipment. - [01:48](https://www.youtube.com/watch?v=6BBx8BwLhqg&t=108s) Restraining tension jumped past 1,300 pounds as magnetic coupling intensified. - [01:48](https://www.youtube.com/watch?v=6BBx8BwLhqg&t=108s) Peak forces reached approximately 1,700 pounds, demonstrating attraction nearing a full ton of force. - [01:48](https://www.youtube.com/watch?v=6BBx8BwLhqg&t=108s) An office chair and adjoining materials became completely immobilized against the bore structure under the field's pull. - [01:48](https://www.youtube.com/watch?v=6BBx8BwLhqg&t=108s) The scale of attraction generated by a 4T scanner far exceeds any possibility of manual human intervention or resistance.

## Detailed walkthrough ### [00:12](https://www.youtube.com/watch?v=6BBx8BwLhqg&t=12s) Measuring Initial Magnetic Pull Near the Bore

The demonstration begins by tracking the immense mechanical forces exerted on ferromagnetic objects as they approach the opening of a 4 Tesla research MRI scanner scheduled for decommissioning. Positioned near the fringe field at the outer face of the scanner bore, a load-measuring setup monitors the pull on a test object. A speaker observes the initial tension building rapidly as the object approaches the scanner entrance, noting: “So the force we're reading on that guy right now just at that part of the magnet is close to 300 to 80.”

As the object moves closer and begins to interact more directly with the steep magnetic field gradient at the bore opening, the attractive force scales dramatically within just a few inches of movement. The force gauge climbs steadily through intermediate thresholds until the speaker verifies the severe physical resistance holding the item, announcing: “It is giving us a reading of five hundred-pound.”

- Measured magnetic attraction begins between 280 and 300 pounds of force at the outer perimeter of the magnet face. - The tension quickly escalates to 500 pounds as the object draws closer to the bore aperture.

[01:48](https://www.youtube.com/watch?v=6BBx8BwLhqg&t=108s) Escalating Attraction and Massive Restraining Forces

As testing continues with larger items—including an office chair caught by the scanner's powerful field—the measured force escalates well beyond what any individual or team could manually resist. The team monitors the readouts in real time as the numbers rapidly climb past fifty-five hundred, sixty, and into the seven hundreds, with one speaker confirming: “Seven hundred pounds and we have jumped 1300s.”

The magnetic pull continues surging well into four digits as items get pinned firmly against the magnet, with additional equipment trapped alongside them. Observing the gauge as an office chair remains immobilized against the bore structure, the speaker notes the staggering final threshold reached during the test, pointing out: “Stuff is still on top of the chair so we're just about 1700s which is far more than this yeah.”

- Force measurements spike progressively through 700 pounds, jump past 1,300 pounds, and peak around 1,700 pounds. - Ferromagnetic office furniture and attached items become entirely pinned against the scanner face under nearly a ton of magnetic force.

## Mentioned practiCal fMRI, practiCalfMRI.blogspot.com, MRI magnet quench: the movie

## Video description UPDATE: Questions about why we were doing what we were doing? Please see the FAQ under "MRI magnet quench: the movie." That video is also entertaining, btw.

Fun, games and safety implications with a 4 tesla (T) MRI magnet that was about to be decommissioned. Note how magnetic objects let loose tend to oscillate along the magnet bore. That's because the peak magnetic field gradients are at either end (near the magnet face), causing peak acceleration as the object enters, followed by progressively damped changes of direction. See practiCalfMRI.blogspot.com for more information.

[Source](https://www.youtube.com/watch?v=6BBx8BwLhqg)

中文简报

4特斯拉MRI扫描仪以1700磅拉力吸附家具 扫描仪孔径处陡峭的磁场梯度使引力激增至超过1700磅，将铁磁性物体牢牢吸附，人力根本无法挣脱。 该视频展示了一台强大的4特斯拉MRI扫描仪对靠近其孔径的铁磁性物品施加的危险力量。实验人员使用测力装置，记录了磁拉力如何从外周的约280至300磅，增加到靠近入口处的500磅。在测试办公椅等较大型物品时，引力迅速攀升并超过700磅和1300磅。最终，这些物品在大约1700磅的力量作用下被死死吸附在扫描仪表面，这说明了将磁性物体带入运行中的MRI环境所具有的极度危险性。 在报废一台4特斯拉MRI扫描仪之前，研究人员进行了实地测力，展示了铁磁性物体在磁体孔径附近受到的极强机械引力。 (0:12) 测试物体受到的初始拉力测量值在280至300磅之间，随着向磁体开口方向移动仅数英寸，拉力便迅速激增至500磅。 (0:12) 当办公椅等较大物品被移近孔径时，测量到的引力先后突破700磅和1300磅，最终在1700磅左右达到峰值。 (1:48) 磁体表面的陡峭磁场梯度导致未固定的磁性物体急速加速并剧烈摆动，产生的压迫吸附力远远超出了人类体能所能对抗的范畴。 (1:48)

Reading summary

Testing on a decommissioned 4 Tesla research MRI scanner demonstrates that magnetic pull escalates rapidly from several hundred pounds near the fringe field to approximately 1,700 pounds at the bore aperture, making physical restraint impossible. Rapid Force Escalation at the Bore Perimeter (0:12) Using a load-measuring setup on a 4 Tesla scanner scheduled for decommissioning, demonstrators recorded substantial mechanical forces acting on ferromagnetic test objects well before entering the bore. At the outer perimeter of the magnet face along the fringe field, initial attraction registered between 280 and 300 pounds of force. Moving the object only inches closer into the steep magnetic field gradient caused the attractive force to climb sharply. Within this short distance, the measured tension reached a verified threshold of 500 pounds, illustrating how quickly resistance builds near the opening. Four-Digit Restraining Forces on Trapped Equipment (1:48) When testing progressed to larger ferromagnetic items, including an office chair, the exerted force surged past manual human control. Real-time readouts documented the pull rising steadily through 700 pounds before jumping past 1,300 pounds as the field gripped the furniture. The attraction peaked around 1,700 pounds as the office chair and additional equipment became completely pinned against the scanner face. This nearly ton-level force immobilized the objects, demonstrating the severe entrapment hazards posed by strong magnetic fields. The measurements demonstrate that once ferromagnetic items interact with high-field magnetic gradients, the resulting forces rapidly reach thousands of pounds, rendering manual recovery impossible and causing severe impact and pinning against the magnet.

精炼阅读摘要

practiCal fMRI在一台即将退役的4 Tesla科研级核磁共振扫描仪上进行的受力测试表明，铁磁性物体在靠近扫描仪孔径时会承受极端且剧烈攀升的机械吸引力，其拉力可从初始的数百磅迅速飙升至近1700磅。 孔径边缘的梯度磁场与初始受力 (0:12) 在针对4 Tesla核磁共振扫描仪孔径边缘场的测量中，实验人员记录到铁磁性测试物体在靠近扫描孔入口外围时，初始磁力读数便已达到280至300磅。这种强大的边缘引力对接近的物体形成了明显的机械拉扯。 当测试物体在孔径边缘仅仅移动数英寸、更直接地切入陡峭的磁场梯度时，吸引力呈现出急剧非线性的放大趋势。测力装置读数随之迅速跨越中间阈值并攀升至500磅，验证了在进入扫描孔前的短距离内便已形成极强的物理阻力。 大型设备吸附与不可抗拒的极端引力 (1:48) 随着测试对象扩大为包含办公椅在内的大型铁磁性物品，磁场的吸力进一步攀升至完全超出人力抵抗能力的量级。测试读数在短时间内相继突破500磅中段与600磅，随后确认超过700磅，并直接跃升至1300磅以上。 最终，在办公椅及上方附加设备被死死固定在扫描孔结构表面时，测量仪器的读数达到了约1700磅的峰值。这一接近一吨的磁吸力表明，一旦大型铁磁性物体进入强磁场核心区域，其产生的机械约束将彻底无法通过人工手段进行剥离。 该实测展示了强磁场环境下铁磁性物体的受力规模，证实了距离扫描仪孔径仅数英寸的磁场梯度即可产生高达1700磅的致命物理束缚力，构成了人力无法干预的严重安全隐患。

Original transcript

[0:12] Oh like [0:19] so the force we're reading on that [0:21] guy right now just at that part of the [0:23] magnet is close to 300 to 80 [0:37] no good now and it's going to attach [0:42] itself to 42nd - stop typing it is now [0:53] it is giving us a reading of five [0:56] hundred-pound [1:02] [Music] [1:13] you [1:48] fifty-five sixty seven hundred yeah [1:59] seven hundred pounds and we have jumped [2:04] 1300s yeah stuff is still on top of the [2:11] chair so we're just about 1700s which is [2:23] far more than this yeah