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

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.

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