How strong is the laser used for positioning in an mri machine? is it dangerous for eyes?

Question

How strong is the laser used for positioning in an mri machine? is it dangerous for eyes?

Answer 1

Different MRI's have different classed lasers, however most are in the Class II below, which is within safe guidelines.  Usually, your MRI operator will give you goggles to protect the eye from even miniscule exposer.

The United States Center for Devices & Radiological Health (CDRH) enforces strict safety requirements for lasers.

The CDRH classifies lasers into several different categories depending on output power, wavelength and fan angle. Structured lighting products mainly fall into the following three categories, depending on radiation levels attained during regular laser use:

class II --"Caution"

Visible laser light less than 1.0 mW.

Considered eye-safe, normal exposure to this type of beam willnot cause permanent damage to the retina. When exposed to this level of laser light, the blinking reflex of the human eye is fast enough to avoid any damage. A class II safety rating is considered eye-safe, but can be hazardous if there is direct intentional long-term ocular exposure (> 0,25 seconds). Any class II-rated laser product can be installed on the shop floor with a minimum of concerns.



class IIIa --"Danger"

Visible laser light between 1.0 and 5.0 mW.

Considered eye-safe with caution if viewed for less than 0,25 seconds, but may present a greater hazard if viewed using collecting optics. Focusing of this light into the eye could cause eye damage. Some groups of class IIIa lasers have a DANGER label and are capable of exceeding permissible exposure levels for the eye in 0.25 sec and still pose a low risk of injury.

  class IIIb --"Danger"

Visible laser light between 5.0 and 500 mW.

Invisible laser light less than 500 mW.

Infrared (IR) lasers and high-power visible lasers.

Considered dangerous to your retina if exposed. This includes looking directly into a reflection from a specular (mirror-like) surface. Normally, class IIIb lasers will not produce a hazardous diffuse reflection. At higher levels of the class, these lasers can be skin hazards.

class IV --"Danger"

Visible and Invisible laser light more than 500 mW.

Laser or laser systems that produce a hazard not only from direct or specular reflections, but may also produce hazardous diffuse reflections. Such lasers may produce significant skin hazards as well as fire hazards.