YY/T 0987.5-2016 English PDF (YYT0987.5-2016)

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YY/T 0987.5-2016: Implants for surgery--Magnetic resonance compatibility--Part 5: Magnetically induced torque test method
YY/T 0987.5-2016
YY
PHARMACEUTICAL INDUSTRY STANDARD
OF THE PEOPLE’S REPUBLIC OF CHINA
ICS 11.040.40
C 35
Implants for Surgery - Magnetic Resonance
Compatibility - Part 5. Magnetically Induced
Torque Test Method
外科植入物 磁共振兼容性
ISSUED ON. MARCH 23, 2016
IMPLEMENTED ON. JANUARY 1, 2017
Issued by. China Food and Drug Administration
Table of Contents
Foreword ... 3 
1 Scope ... 5 
2 Normative References ... 5 
3 Terms and Definitions ... 6 
4 Overview of Test Method ... 8 
5 Significance and Application ... 9 
6 Instruments and Equipment ... 9 
7 Test Sample ... 11 
8 Procedures ... 11 
9 Calculation ... 12 
10 Report ... 12 
Appendix A (Informative) Fundamental Principle ... 14 
Bibliography ... 19 
Implants for Surgery - Magnetic Resonance
Compatibility - Part 5. Magnetically Induced
Torque Test Method
1 Scope
This Part of YY/T 0987 includes test method for magnetically induced torque generated
by medical devices as a result of static magnetic field in magnetic resonance
environment; a comparison of magnetically induced torque and medical devices’
gravity moment.
This Part does not involve other possible safety questions. These safety questions
include, but are not limited to, magnetically induced displacement force generated by
the spatial gradient of magnetic field, radio frequency heating and radio frequency
induced heating, noise, interaction among medical devices, functions of medical
devices and magnetic resonance system.
In this Part, torque refers to static magnetic torque generated by MRI static magnetic
field and implant’s magnetic moment. This Part does not include dynamic torque
generated by the rotation of medical device as a result of the interaction between the
static magnetic field and eddy current. Current in the wires might also generate torque.
The sensitivity of torque measurement device shall be more than 1/10 of gravity
moment; gravity moment equals the arithmetic product of the maximum linear size and
the weight of medical device.
This Part does not attempt to elaborate all the involved safety questions, even though
those safety questions are related with the usage. Determining appropriate safety and
health specifications and clarifying the applicability of management limit before
application is the responsibility on the users of this Standard.
2 Normative References
The following documents are indispensable to the application of this Standard. In terms
of references with a specified date, only versions with a specified date are applicable
to this Standard. The latest version (including all the modifications) of references
without a specified date is also applicable to this Standard.
YY/T 0987.1 Implants for Surgery - Magnetic Resonance Compatibility - Part 1.
Safety Marking
YY/T 0987.2 Implants for Surgery - Magnetic Resonance Compatibility - Part 2.
images and/or spectrograms, other physical parameters can also be obtained.
3.7 Magnetic Resonance (MR) Environment
Magnetic resonance environment refers to the space within 0.5 mT (5G) line in MR
system, including the whole three-dimensional space around MR scanner. When 0.5
mT line is included in Faraday cage, the whole space shall be deemed as magnetic
resonance (MR) environment.
3.8 Magnetic Resonance Equipment
MR Equipment
Magnetic resonance equipment refers to medical electrical equipment that is expected
to be applied to in vivo magnetic resonance examination. Magnetic resonance
equipment includes all hardware and software parts from main power to display
monitor. Magnetic resonance equipment is programmable electrical medical system
(PEMS).
3.9 Magnetic Resonance Examination
MR Examination
Magnetic resonance examination refers to the process of gathering patients’ data
through magnetic resonance.
3.10 Magnetic Resonance Imaging; MRI
Magnetic resonance imaging refers to the imaging technology, which utilizes static
time-varying magnetic field to generate resonance of atomic nucleus to obtain tissue
images.
3.11 Magnetic Resonance System
MR System
Magnetic resonance system refers to the combination of magnetic resonance
equipment, accessories (including display, control and energy supply devices) and
controlled entry zone (if provided).
3.12 Magnetically Induced Displacement Force
Magnetically induced displacement force refers to the force on magnetic object in
spatial gradient magnetic field. This force will lead to movement of magnetic object in
the gradient field.
3.13 Magnetically Induced Torque
Magnetically induced torque refers to the torque generated by magnetic object in
in the middle of the magnetic object of magnetic resonance equipment, where
magnetic field is even. The size of torque depends on the loading tray’s deflection
angle relative to an equilibrium position. By rotating the supporting torsional spring and
the frame of the loading tray, the deflection angle of implant can be measured. Thus,
the torque can be calculated. Compare the maximum torque with the severest gravity
moment of medical device; the severest gravity moment equals to the arithmetic
product of medical device’s maximum linear size and weight.
5 Significance and Application
The test method in this Part is is one of the test methods of determining whether the
existence of medical devices would lead to patients’ injury in MR examination or MR
environment. Other safety questions that need to be described include, but are not
limited to, magnetically induced displacement force (refer to YY/T 0987.2) and radio
frequency induced heating (refer to YY/T 0987.4). In order to guarantee the safety of
medical devices in magnetic resonance environment, terms and markings stipulated
in YY/T 0987.1 shall be applied to the marking of medical devices.
If the maximum torque is less than the arithmetic product of medical device’s maximum
size and weight, then, magnetically induced torque is less than the severest gravity
moment generated by gravity. Under this circumstance, it can be deemed that the risk
of magnetically induced torque is not higher than risks of daily activities in the earth’s
gravity field. This is merely conservative estimation; it is possible that a larger torque
also would not bring any hazard to patients.
This test is insufficient to prove medical devices’ safety in magnetic resonance
environment.
The sensitivity of torque measurement device shall be more than 1/10 of gravity
moment; gravity moment equals the arithmetic product of the maximum linear size and
the weight of medical device.
In this Part, torque refers to static magnetic torque generated by MRI static magnetic
field and implant’s magnetic moment. This Part does not include dynamic torque
generated by the rotation of medical device as a result of the interaction between the
static magnetic field and eddy current. Current in the wires might also generate torque.
6 Instruments and Equipment
Test device is shown in Figure 1. The device is constituted of a solid structure, including
a loading tray supported by torsional spring. The device is completely made of non-
ferromagnetic materials. Test sample shall be pasted or bundled on the loading tray. A
protractor (division value. 1°) shall be fixated on a supporting structure. There is a
marking on the loading tray, through which, the included angle of the loading tray and
above test process.
In terms of conductors, try to place them in accordance with the physical configuration
in vivo. If it is feasible, conductors shall load the electric current during the application
in vivo.
9 Calculation
Torque . signifies the loading tray’s deflection angle relative to the
equilibrium position. The equilibrium position is the loading tray’s deflection angle
relative to the fixed pedestal in magnetic field-free area. signifies the torsional
spring’s elastic coefficient.
10 Report
In terms of each test sample, report shall include the following content.
a) Description of test product, including dimension figures or photos (with scale)
of medical devices;
b) Sketch maps or photos of three sample configurations in tests;
c) Medical devices’ product identification (such as batch, batch number, model
number, version number, serial number and date of production);
d) Materials (stipulated materials or others);
e) Quantity of test samples and dimensional specification of selected samples;
f) The mass of sample;
g) Dimension drawings or photos of medical devices (with scale);
h) Type of magnetic object; magnetic field strength B0 of static magnetic field;
i) Take the central point of magnetic object as the original point; use Cartesian
coordinates (x, y, z) of the gravity center of the medical device, which is
determined through right-hand screw rule; including a sketch map of magnetic
resonance system and coordinate axis;
j) Sketch map or photo of test device, including torsional spring’s elastic coefficient;
k) Draw sketch maps of torque (unit. Nm) angle; the angle is the deflection angle
of medical device’s principal axis relative to the direction of static magnetic field;
Appendix A
(Informative)
Fundamental Principle
A.1 Principle
The test method in this Part is mainly used to determine torque generated by medical
devices as a result of the action of magnetic field in magnetic resonance imaging
examination or magnetic resonance environment. It needs to be pointed out that this
Part merely provides the test method for magnetically induced torque, and by merely
relying on this test result, it is impossible to determine medical devices’ safety in
magnetic resonance environment. As described below, when medical devices’
magnetic moment is in an inconsistent direction with the static magnetic field, torque
would be generated. Meanwhile, static magnetic field would generate attraction
towards medical devices; such attraction drives ferromagnetic objects to move towards
the center of magnetic object. In terms of medical devices that are safe in MR
environment, magnetically induced displacement force and torque shall be less than
the displacement force and torque that the medical devices receive when they are not
in large magnetic field space. For example, the displacement force shall be less than
the weight of medical devices; the torque shall be less than the torque generated by
daily activities (might include fast acceleration of vehicles or roller coasters in
amusement park). Other possible safety questions include, but shall not be limited to,
radio frequency heating, radio frequency induced heating, noise, interaction among
medical devices, functions of medical devices and magnetic resonance system.
Although the most commonly seen environment is 1.5T MR system environment for
medical devices, 3T MR system has entered the market and has been increasingly
commonly applied to clinic. It is worth noticing that safe medical devices in 1.5T
scanning system are not necessarily safe in a system with higher or lower magnetic
field strength (for example, 3T or 1T system). Furthermore, open-ended and cylindrical
MR system might also have significant differences. For example, the static magnetic
field spatial gradient of an open-ended system is obviously higher.
After determining the safety of medical devices, apply the terms and markings provided
in YY/T 0987.1 to the marking. MR safe, MR conditional or MR unsafe. Please see the
terms and definitions in YY/T 0987.1 below.
MR safe---objects that do not generate already known hazards in all MR environments.
NOTE. MR safe objects include non-conductive and non-magnetic objects, for example,
plastic petri dish. Whether objects are MR safe can be determined in accordance
with scientific theories, not experimental data.
MR conditional---objects that do not generate already known hazards under specific