IEC 60601-2-33:2002/AMD1:2005

INTERNATIONAL IEC
STANDARD 60601-2-33
AMENDMENT 1
2005-08
Amendment 1
Medical electrical equipment –
Part 2-33:
Particular requirements for the safety
of magnetic resonance equipment
for medical diagnosis
 IEC 2005 Droits de reproduction réservés  Copyright - all rights reserved
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– 2 – 60601-2-33 Amend. 1  IEC:2005(E)

FOREWORD
This amendment has been prepared by subcommittee 62B: Diagnostic imaging equipment, of

IEC technical committee 62: Electrical equipment in medical practice.

The text of this amendment is based on the following documents:

FDIS Report on voting
62B/573/FDIS 62B/586/RVD
Full information on the voting for the approval of this amendment can be found in the report
on voting indicated in the above table.
The committee has decided that the contents of this amendment and the base publication will
remain unchanged until the maintenance result date indicated on the IEC web site under
"http://webstore.iec.ch" in the data related to the specific publication. At this date, the
publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
___________
Page 13
6.8.2 INSTRUCTIONS FOR USE
Replace, on page 18, the existing item pp) by the following:
pp) Recommended training
INSTRUCTIONS FOR USE shall recommend that training is needed for physicians and the
OPERATOR to operate the MR EQUIPMENT safely and effectively. This training shall include
emergency procedures, including those for the issues described in this subclause under
− cc) Emergency medical procedures
− ee) CONTROLLED ACCESS AREA
− mm) EMERGENCY FIELD SHUT DOWN UNIT
− nn) Fire precautions
− ss) Emergency actions in the event of a QUENCH.
Add, on page 18, the following new item ss):
* ss) Emergency actions in case of a QUENCH
The INSTRUCTIONS FOR USE shall include instructions on how to identify a QUENCH and how
to act in the event of a QUENCH, especially when the venting system of the
superconducting magnet system fails.

60601-2-33 Amend. 1  IEC:2005(E) – 3 –

Page 19
6.8.3 Technical description
Replace, on page 20, the existing item cc) by the following:

* cc) Safety provisions in the event of a quench

For MR EQUIPMENT equipped with superconducting magnets, the ACCOMPANYING

DOCUMENTS shall
– state the requirements for a venting system for the superconducting magnet which

connects the cryostat of the magnet to the outside atmosphere and which is designed

to withstand a QUENCH and to protect nearby persons in the event of a QUENCH;
– provide guidelines for the construction (dimensions, position, assembly and material to
be applied) of the venting system for the superconducting magnet inside and outside
the examination room;
– recommend a preventive maintenance program, which states that regular checks of the
adequateness of the function of the venting system for the superconducting magnet
are to be made;
– state requirements for the design of the examination room to increase safety of the
patient and other persons inside and outside the examination room in the event of
failure of the venting system during a quench. The suggested design shall address the
issues of reducing pressure build-up, temperature decrease and oxygen depletion
during a quench. A number of acceptable solutions for such provisions, demonstrated
to be effective by simulation or test, shall be listed, so that even when the venting
system of the superconducting magnet fails to work adequately, the chance of a
hazard for the PATIENT or other persons inside as well as outside the examination
room, as caused by PRESSURE build-up, temperatures decrease or oxygen depletion
during the QUENCH, is reduced considerably;
– state the need for the USER to establish an emergency plan for a quench, including a
situation in which the venting system for the superconducting magnet fails to function
adequately;
– state the need for possible extra control measures for the PATIENT ventilation system in
order not to expose the PATIENT to additional helium transported to the PATIENT via the
PATIENT ventilation system. The PATIENT ventilation system should have its inlet
opening in a safe place (such as at a low level in the examination room or directly
connected to the air-conditioning of the examination room), or be connected to a
QUENCH detector, so that the PATIENT ventilation system can be automatically controlled
when a QUENCH occurs and will not transport helium to the PATIENT inside the scanner.
NOTE 1 The venting system for the superconducting magnet is considered to be the cryogenic vent pipe and all
the extra components necessary to safely accommodate a QUENCH.
NOTE 2 Examination room configurations demonstrated by simulation or test that are acceptable include:

− configurations in which the RF door opens outwards or is a sliding RF door;
− configurations in which the RF door opens inwards, if these include extra precautions to prevent PRESSURE
build up. This can be realized by one of the following
• an extra examination room ventilator system, which can be switched on (possibly automatically via an
oxygen monitor in the ceiling of the examination room to detect the escape of helium gas) in the
event of a QUENCH; or
• an opening in the wall or ceiling of the examination room, venting towards an open area; or
• a possibility of opening the observation window in the examination room outward or by sliding; or
• a second independent venting system for the superconducting magnet that remains operational in
case the regular venting system for the superconducting magnet is obstructed; or
• equivalent methods demonstrated to be effective by simulation or test.

– 4 – 60601-2-33 Amend. 1  IEC:2005(E)

Page 45
Annex BB – Guidance and rationale for particular subclauses

Add, on page 57, a rationale for subclause item 6.8.2 ss) as follows:

Concerning 6.8.2 ss)
In addition to the information given in Clause 6.8.2 cc) on emergency medical procedures and

clause 6.8.2 ff) on liquid and gaseous cryogens, this item provides information pertinent to

emergencies present in the event that magnet helium gas escapes from the magnet into the
examination room or other adjacent rooms during a QUENCH. This situation may be present
when the venting system of the superconducting magnet fails either in part or fully during a
magnet QUENCH. In this case, hazards may be present for the personnel involved. The
information provided here will be useful for the OPERATOR in establishing an emergency plan
adapted to local requirements.
While a QUENCH as such is a rare event, the additional failure of a venting system of the
magnet is even more unlikely. Although thousands of MR SYSTEMS are in operation, there
have been only a few reports to date regarding accidents or near accidents involving personal
injuries in relationship to a QUENCH. Nevertheless, the MANUFACTURERS are required to point
out the potential hazard of the combined event and to provide information pertinent to this
type of emergency. Note that the information covers the highly unlikely, yet possibly serious
event of a malfunctioning venting system at the time of a quench of the superconducting
magnet.
What is a QUENCH?
During a QUENCH, the magnet loses its super-conductivity. The magnetic field ramps down in a
matter of seconds – typically lasting approximately 20 seconds. The magnet begins to warm
up. Liquid helium boils off at a rate of 500 to 1 500 l within a few minutes and expands
quickly. The exact boil-off rate amount depends on the fill level as well as the field strength of
the magnet. A 3 T magnet may have a higher boil-off rate than a 1,5 T magnet. One litre of
liquid helium translates into approximately 700 l of gaseous helium. During maximum
conditions this means approximately 1 000 m³ of gas. A manual QUENCH may be initiated by
activating the Emergency field shut down unit. Another source for quenching is when the
helium fill level decreases to a point where the magnet begins to warm up. In rare instances,
a spontaneous QUENCH may be observed that cannot be explained by the presence of obvious
causes.
Hissing or whistling noises caused by the quickly escaping stream of cold helium gas may

accompany a QUENCH. Plumes of white fog sink to the floor mainly from the upper part of the
magnet from the vicinity of the QUENCH line due to condensation of both water vapour and air.
The stream of helium gas diminishes in a matter of minutes. Air near the non-insulated
components of the magnet and the QUENCH line condenses into liquid air and drips to the
floor.
Risks associated with a failing venting system
The purpose of the venting system of the superconducting magnet is to securely exhaust
gaseous helium to the outside. The main element of this system is a conduit that is designed
to transport the escaping helium gas to a safe open area. The possibility of a QUENCH should
be taken into careful consideration during the design of both the magnet and the venting
system of the superconducting magnet. As a result, a QUENCH should be completely harmless
to personnel. Also, neither the magnet nor the MR installations as such should be subject to
damage during a QUENCH.
60601-2-33 Amend. 1  IEC:2005(E) – 5 –

An emergency situation will arise if a quench venting system fails. Helium is lighter than air,

and is non-poisonous and non-flammable. However, since it displaces oxygen, the risk of

suffocation exists. Cryogenic helium escaping into the ambient air leads to white clouds

caused by condensation. These clouds will adversely affect visibility.

Persons may be rendered unconscious by the amount of helium entering their respiratory

system. Depending on the helium concentration present in the air, a few breaths may suffice

to result in unconsciousness.
In addition, escaping helium is extremely cold, possibly causing hypothermia and frostbite.

The latter results in injuries resembling burns (cryogenic burns) after the skin is exposed to

normal temperature levels. Skin contact with cold parts or liquid air may also lead to frostbite.
A variety of failures of the venting system of the superconducting magnet are conceivable. For
instance, the following may occur.
− Small leaks: smaller amounts of helium gas are exhausted to the outside via the heating
and air conditioning system and replaced by fresh air. This is not a critical situation as
long as the heating and air conditioning system functions as required.
These leakages are the result of constructional errors that need to be corrected.
− The venting system of the superconducting magnet fails in part: only part of the helium
gas is exhausted to the outside via the integrated venting system. Larger amounts of
helium are present in the examination room. The heating and air conditioning system
cannot remove the helium due to its volume. Large clouds form, which adversely effects
visibility. Additionally, the PRESSURE in the room increases. Depending on the size of the
leakage, hazardous conditions may be present for the personnel involved.
− Total failure: the venting system of the superconducting magnet fails completely, e.g.
through blockage or breaks in the line. The entire amount of gas is exhausted into the
examination room. If the requirements and recommendations previously mentioned are
not followed, there is an increased potential for loss of life in the case of a complete
cryogen vent failure.
− Up to 1 000 m of gas are blown into the room, which frequently has a volume of less than
100 m .
Add, on page 58, a rationale for subclause item 6.8.3 cc) as follows:
Concerning 6.8.3 cc)
Examination room configuration
A number of examination room features are suggested in the standard. For the examination

room features a clear distinction is made between the helium venting system for the
superconducting magnet needed in case of a QUENCH and the PATIENT ventilation system
needed for daily air refreshment for the PATIENTS. The examination room features try to
maximise the time available to remove a PATIENT from the system in the event of a QUENCH
associated with a failing venting system of the superconducting magnet. These features will
help increase the time available to remove a patient to an average time of a few minutes. In
general the operation of the PATIENT ventilation system should be monitored carefully. Some
PATIENT ventilation systems bring fresh conditioned air from the top of the examination room
to the PATIENT. In the event of a QUENCH associated with a failing venting system of the
superconducting magnet, this is very unfavourable for the PATIENT, and the operation of the
PATIENT ventilation system should be stopped, preferably automatically via the detection of the
QUENCH by a sensor. Also, an automated warning to the OPERATOR can be considered in all
situations.The fitting of an oxygen monitor, wired to audible and visual alarms, in the ceiling of
the examination room to give an early warning of the escape of helium gas is recommended.
When remodelling of the examination room is performed, the integrity of the RF-shielding has
to be tested again.
– 6 – 60601-2-33 Amend. 1  IEC:2005(E)

Door of the examination room opens inwards – constructional safety measures

The most unfavourable situation for the examination room is when the door of the examination

room opens inwards. In this situation, slight overpressure due to helium gas leakage may

make opening of the door extremely difficult. Depending on the ventilation system for the

room, overpressure may be present for a considerable length of time. Installation of a
provision in the examination room to allow air breathing for persons present in the

examination room during the QUENCH in this situation may help to increase the time available

to allow for pressure equalization in the room.

To address this situation the f
...