Open access peer-reviewed chapter

MRI RF-Induced Heating in Heterogeneous Human Body with Implantable Medical Device

Written By

Ran Guo, Jianfeng Zheng and Ji Chen

Submitted: June 7th, 2017 Reviewed: October 2nd, 2017 Published: December 20th, 2017

DOI: 10.5772/intechopen.71384

Chapter metrics overview

1,792 Chapter Downloads

View Full Metrics

Abstract

Magnetic resonance imaging (MRI) radio frequency (RF)-induced heating is one of the most important concerns of MRI safety for patients, especially with orthopaedic healthcare products. In this chapter, numerical modelling and simulations were conducted to study the RF-induced heating within a 1.5T and 3T magnetic resonance (MR) environment. Numerical simulations were firstly conducted to study the difference between the cases of implantable medical devices inside the phantom and the human body. Then, numerical modelling were conducted to describe the difference of electromagnetic behaviours between the homogeneous phantom and heterogeneous human tissues. The MRI RF-induced heating due to an implantable medical device behaves significantly different in homogeneous media and in heterogeneous human body. For typical orthopaedic medical devices, such as healthcare products applied to shoulder, humerus, hip, femur and tibia, the properties of the RF-induced heating are different in general phantom and in human body. The hot spot location, as well as worst case configuration were evaluated and it was found that they were determined by the incident field and electromagnetic properties of medium. With further scaling, the RF-induced heating in human body for the orthopedic devices can be assessed by phantom studies.

Keywords

  • MRI
  • RF-induced heating
  • orthopedic implant
  • phantom

1. Introduction

Many of the MR-related injuries and the few fatalities that have occurred were the apparent result of failure to follow safety guidelines or of the use of inappropriate information related to the safety aspects of biomedical implants and devices [1, 2, 3, 4, 5, 6, 7]. The preservation of a safe MR environment requires constant attention to the care of patients and individuals with metallic implants and devices, because the variety and complexity of these objects constantly changes [5, 6, 7]. Therefore, to guard against accidents in the MR environment, it is important to understand the risk associated with implantable medical devices which may cause potential problems.

The radiofrequency coils could send energy, in the form of electromagnetic radiation, into the human body. Since the energy is in the radio frequency range, the radiation is not ionizing. But it still can influence biological tissue. During MR procedures, the majority of the RF power transmitted for imaging or spectroscopy (especially for carbon decoupling) is transformed into heat within the patient’s tissue as a result of resistive losses, through convection, conduction, radiation or evaporation [8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18]. Thus, a potential concern in MRI is the heating of the body during image acquisition.

To evaluate the RF-induced heating, the specific absorption rate (SAR) is applied to determine how much electromagnetic energy is absorbed by the body. SAR is typically expressed in unites of watts per kilogram, or W/kg. So the SAR could be defined as:

SAR r = σ 2 ρ E 2 r E1

where E is the total electric field and σ and ρ are the conductivity and density of biological tissue, respectively. The temperature rise in human body or phantom could be calculated by the total SAR according to the bio heat equation. SAR depends on the pulse sequence and the size, geometry, and conductivity of the absorbing object. To ensure participant safety, SAR in MRI studies is limited to minimize temperature increases.

The first study of human thermal responses to RF radiation-induced heating during an MR procedure was conducted by Schaefer et al. [19]. Temperature changes and other physiological parameters were assessed in volunteer subjects exposed to relatively high, whole-body averaged SARs (approximately 4.0 W/kg). The data indicated that there were no excessive temperature elevations or other deleterious physiological consequences related to the exposure to RF radiation [19].

However, for patients with medical implants, MRI-related RF induced heating is potentially problematic. The evaluation of heating for an implant or device is particularly challenging because of the many factors that affect temperature increase in these items. Variables that impact heating include the following: the specific type of implant or device; the electrical characteristic of the implant or device; the RF wavelength of the MR system; the type of transmit RF coil that is used (i.e., transmit head versus transmit body RF coil); the amount of RF energy delivered (i.e., the specific absorption rate, SAR); the landmark position or body part undergoing MRI relative to the transmit RF coil; and the orientation or configuration of the implant or device relative to the source of transmit RF coil.

In this chapter, it shows the importance of evaluation the MRI-related RF induced heating issues for patient with implantable medical devices. Generally, the estimation and measurement is based on in-vitro numerical simulation and experiment. And assessment methods could be separated into active and passive medical implants, respectively, due to the configuration difference of these devices. With the help of the in-vitro evaluation methods, it provides a highly possible way to estimate the temperature increase for patient with implants or devices during MRI examination.

Advertisement

2. In-vivo and in-vitro

MRI may be contraindicated for a given patient primarily due to its potential risks associated with a metallic implant or device. Although many investigations have been performed using laboratory animals to determine thermoregulatory reactions to tissue heating associated with exposure to RF radiation, these experiments do not directly apply to the conditions that occur during MR procedures, nor can they be extrapolated to provide useful information for various reasons [20, 21]. For example, the pattern of RF absorption or the coupling of radiation to biological tissues is primarily dependent on the organism’s size, anatomical features, duration of exposure, sensitivity of the involved tissues (e.g., some tissues are more “thermal sensitive” than others), and a myriad of other variables [14, 21, 22]. Furthermore, there is no laboratory animal that sufficiently mimics or simulates the thermoregulatory responses of an organism with the dimensions and specific responses to that of a human subject. Therefore, experimental results obtained in laboratory animals cannot be simply “scaled” or extrapolated to predict thermoregulatory or other physiological changes in human subjects exposed to RF radiation-induced heating during MR procedures [14, 15, 22], and. In consideration of the above, in-vitro testing is performed to assess the various MRI issues for implants and devices in order to properly characterize the possible risks.

One of in-vitro methods is to use standard American Society for Testing and Materials (ASTM) phantom. ASTM F2182-11A depicts the guideline to measure the RF heating induced by implanted medical devices in a standard phantom filled with gelled-saline which mimic the muscles [23]. Studies have been conducted to evaluate the RF heating induced by orthopedic implants. Commonly a phantom or homogenous media is used to mimic the environments as the implants locate in human body in experiments and/or numerical simulations [24, 25, 26, 27, 28, 29, 30, 31, 32].

Although the RF-induced heating evaluating method using the phantom filled with gelled-saline is widely used, it is obvious that the RF environment of a human body and a phantom filled with gelled-saline are quite different. The power deposition due to an implant for a given incident RF field is a function of the physical properties of the implant and electrical properties of the surrounding medium. Compared with homogeneous gelled-saline in phantom, human body is an inhomogeneous circumstance which includes different tissues with various permittivity and conductivity in a wide range. Hence, it is necessary to study a feasible guide with in-vitro phantom to assess the RF-induced heating in heterogeneous human body.

2.1. Human body: heterogeneous medium

With the development of computational electromagnetics, anatomical computer models of the human body have been used for nearly four decades for dosimetric applications in electromagnetics (EM) [33] and in medical radiation physics [34]. The most prominent numerical methods used in computational dosimetry of electromagnetic fields are based on finite-difference formulations of the underlying differential equations. For the simulation of both RF fields and induced tissue heating, the finite-difference time-domain (FDTD) method in its formulations by Yee [35] and Patankar [36] is applied to rectilinear grids to optimally handle large voxel models. The reconstructed human model used in this Chapter is from the Virtual Family [37]. It is based on high resolution magnetic resonance images of healthy volunteers. Seventy seven different tissue types were distinguished during the segmentation. Currently, the models are being widely applied in several studies on electromagnetic exposure, device optimization and medical applications. Table 1 shows the characteristics of the anatomical model. Duke model is an anatomical model of adult male which is shown in Figures 1 and 2 . And Table 2 shows the segmented tissues and organs of the model, as well as the electromagnetic properties.

Name Age (years) Gender Height (m) Mass (kg) BMI (kg/m2)
Duke 34 Male 1.74 70 23.1

Table 1.

The characteristics of the anatomical Duke model.

Figure 1.

The segmented tissues and organs of anatomic body.

Figure 2.

The segmented tissues and organs of anatomic brain.

Tissue or organ Electric conductivity (S/m) Relative permittivity Density (kg/m3)
1.5 T/64 MHz 3 T/128 MHz 1.5 T/64 MHz 3 T/128 MHz
Adrenal gland 0.778305 0.804166 73.9472 66.7839 1027.5
Air internal 0 0 1 1 1.2
Artery 1.20667 1.24863 86.4441 73.159 1049.75
Bladder 0.287352 0.298014 24.5943 21.8607 1035
Blood vessel 1.20667 1.24863 86.4441 73.159 1049.75
Bone 0.0595255 0.0673524 16.6812 14.7171 1908
Brain gray matter 0.510868 0.58673 97.4294 73.5204 1044.5
Brain white matter 0.291504 0.342151 67.8358 52.5338 1041
Bronchi 0.528415 0.559346 58.8896 50.5714 1101.5
Bronchi lumen 0 0 1 1 1.2
Cartilage 0.452103 0.488375 62.9145 52.9242 1099.5
Cerebellum 0.719003 0.829397 116.35 79.7377 1045
Cerebrospinal fluid 2.06597 2.14301 97.3124 84.0406 1007
Commissure anterior 0.291504 0.342151 67.8358 52.5338 1041
Commissure posterior 0.291504 0.342151 67.8358 52.5338 1041
Connective tissue 0.474331 0.498727 59.4892 51.8568 1525
Cornea 1.00058 1.05874 87.3779 71.4566 1050.5
Diaphragm 0.688213 0.719235 72.2347 63.4948 1090.4
Ear cartilage 0.452103 0.488375 62.9145 52.9242 1099.5
Ear skin 0.43575 0.522704 92.1679 65.437 1109
Epididymis 0.884871 0.926404 84.5272 72.1279 1082
Esophagus 0.877842 0.912807 85.8204 74.895 1040
Esophagus lumen 0 0 1 1 1.2
Eye lens 0.28588 0.312684 50.3392 42.7911 1075.5
Eye sclera 0.882673 0.917665 75.2998 64.9991 1032
Eye vitreous humor 1.50315 1.50536 69.1264 69.0619 1004.5
Fat 0.0661558 0.0697299 13.6436 12.3711 911
Gall bladder 1.48179 1.5764 105.443 88.8995 928
Heart lumen 1.20667 1.24863 86.4441 73.159 1049.75
Heart muscle 0.678423 0.766108 106.514 84.2573 1080.8
Hippocampus 0.510868 0.58673 97.4294 73.5204 1044.5
Hypophysis 0.778305 0.804166 73.9472 66.7839 1053
Hypothalamus 0.778305 0.804166 73.9472 66.7839 1053
Intervertebral disc 0.452103 0.488375 62.9145 52.9242 1099.5
Kidney cortex 0.741316 0.852313 118.556 89.6168 1049
Kidney medulla 0.741316 0.852313 118.556 89.6168 1044
Large intestine 0.638152 0.705214 94.6639 76.5722 1088
Large intestine lumen 0.688213 0.719235 72.2347 63.4948 1045.2
Larynx 0.452103 0.488375 62.9145 52.9242 1099.5
Liver 0.447984 0.510897 80.5595 64.2507 1078.75
Lung 0.288977 0.315616 37.1022 29.4677 394
Mandible 0.0595255 0.0673524 16.6812 14.7171 1908
Marrow 0.154335 0.162021 16.4355 13.5377 1028.5
Medulla oblongata 0.719003 0.829397 116.35 79.7377 1045.5
Meniscus 0.452103 0.488375 62.9145 52.9242 1099.5
Midbrain 0.719003 0.829397 116.35 79.7377 1045.5
Mucosa 0.488039 0.544202 76.7233 61.5852 1102
Muscle 0.688213 0.719235 72.2347 63.4948 1090.4
Nerve 0.312174 0.353802 55.0621 44.0653 1075
Pancreas 0.778305 0.804166 73.9472 66.7839 1086.5
Patella 0.0595255 0.0673524 16.6812 14.7171 1908
Penis 0.429311 0.478934 68.6368 55.9888 1101.5
Pharynx 0 0 1 1 1.2
Pineal body 0.778305 0.804166 73.9472 66.7839 1053
Pons 0.719003 0.829397 116.35 79.7377 1045.5
Prostate 0.884871 0.926404 84.5272 72.1279 1045
SAT 0.0661558 0.0697299 13.6436 12.3711 911
Skin 0.43575 0.522704 92.1679 65.437 1109
Skull 0.0595255 0.0673524 16.6812 14.7171 1908
Small intestine 1.59145 1.69285 118.363 87.9725 1030
Small intestine lumen 0.688213 0.719235 72.2347 63.4948 1045.2
Spinal cord 0.312174 0.353802 55.0621 44.0653 1075
Spleen 0.743914 0.835186 110.559 82.8917 1089
Stomach 0.877842 0.912807 85.8204 74.895 1088
Stomach lumen 0.688213 0.719235 72.2347 63.4948 1045.2
Teeth 0.0595255 0.0673524 16.6812 14.7171 2180
Tendon ligament 0.474331 0.498727 59.4892 51.8568 1142
Testis 0.884871 0.926404 84.5272 72.1279 1082
Thalamus 0.510868 0.58673 97.4294 73.5204 1044.5
Thymus 0.778305 0.804166 73.9472 66.7839 1023
Thyroid gland 0.778305 0.804166 73.9472 66.7839 1050
Tongue 0.652145 0.687137 75.2998 64.9991 1090.4
Trachea 0.528415 0.559346 58.8896 50.5714 1080
Trachea lumen 0 0 1 1 1.2
Ureter Urethra 0.429311 0.478934 68.6368 55.9888 1101.5
Vein 1.20667 1.24863 86.4441 73.159 1049.75
Vertebrae 0.0595255 0.0673524 16.6812 14.7171 1908

Table 2.

The electromagnetic properties of the segmented tissues and organs.

2.2. ASTM phantom: in-vitro measurement

The standard F2182 describe a test method for measurement of RF induced heating on or near passive implants and its surrounding during MRI procedure. A design of phantom container is introduced in the standard with its dimension shown in Figure 3 . The material of phantom container are electrical insulators and non-magnetic and non-metallic. The phantom container is filled with a gelled-saline which has a relative permittivity εr = 80.4 and conductivity of σ = 0.47 S/m. In order to have a great conductivity and viscosity, a suitable gelled saline should be made with 1.32 g/L NaCl and 10 g/L polyacrylic acid (PAA) in water. Numerical simulations indicate that the maximum electric field inside the ASTM phantom is at mid-axial plane about 2 cm away from the vertical phantom side wall. To maximize the heating, and thereby maximizing the signal-to-noise ratio, we placed the implants at this location.

Figure 3.

The structure and dimension of standard ASTM phantom.

A generic RF transmit body coil is developed and shown in Figure 4 . The upper plots represent a 1.5 T RF coil and the lower two plots represent a 3 T RF coil. A physical coil is usually difficult to model and it takes much longer simulation time to reach the steady state of the simulation. It has been shown that using a non-physical coil could significantly reduce the simulation time while providing the same result as that from a physical coil. Thus, rather than modeling the exact physical coil, the non-physical coils were modeled in this study. The two coils have the same dimensions, and both have 8 rungs. The diameter of the RF coil is 63 cm, and the height of the RF coil is 65 cm. The eight parallel lines or the rungs are one dimensional line current excitation. The end rings on top and bottom of the RF coils are tuning capacitors which are also modelled as one dimensional line segments.

Figure 4.

The generic coil model of 1.5-T RF coil (top) and 3-T RF coil (bottom) in SEMCAD X.

The capacitance value is determined from several broadband simulations so that the second highest resonant frequency was adjusted to 64 MHz for 1.5-T and 128 MHz for 3-T systems. The detailed steps are: set an initial capacitance value for all capacitors on end rings and add a broadband pulse signal on one single rung. The other seven rungs are modeled as zero ohm resistors. After the simulation is finished, the power spectrum is extracted. If the second highest resonant frequency is not at appropriate resonant frequencies, the capacitance needs to be adjusted. From this study, the capacitance for the end ring tuning capacitor values is 7.2 pF for 1.5-T RF coil and 1.3 pF for 3-T RF coil.

Advertisement

3. Passive implantable medical device

Any device intended to be totally or partially introduced into the human body through surgical intervention and intended to remain in place after the procedure for at a long-term duration is considered as an implantable device. Passive devices in terms of their form of operation can be classified as device used for transportation and storage of pharmaceutical liquid, device for alteration of blood, body fluids, medical dressing, surgical instruments; reusable surgical instruments, disposable aseptic device, implantable device, device for contraception and birth control, device for sterilization and cleaning, patient care device, in vitro diagnostic reagent, as well as other passive contacting device or passive supplementary device.

In this chapter, three typical categories of orthopedic implantable devices, bone plate system, hip prostheses and tibia intramedullary nails, are selected for MRI related RF induced heating study which are shown in Figures 5 7 . The configuration of each implantable device is shown in figure. For bone fragment compression plate, it is designed to offer multiple compression and reconstruction plating options for the treatment of bone fractures. The application of hip prostheses is related to hip revision and arthroplasty. As for intramedullary nails, they are characterized by the anatomic shape, which is intended to replicate the natural anatomic shape of the bones. They have been designed to help restore the shape of the bone and treat the fractured bones.

Figure 5.

The bone plant system of AxSOS system from Stryker®.

Figure 6.

The hip prostheses of Excia® T from Aesculap®.

Figure 7.

The tibia intramedullary nails of PROTect™ from Depuy Synthes.

Advertisement

4. Numerically evaluate RF-induced heating

4.1. FDTD method

In this numerical investigation, we use the finite difference time domain (FDTD) based SEMCAD X 14.8 (SPEAG) simulation platform. Graphics processing unit (GPU) hardware acceleration was achieved using the SPEAG CUDA library with Tesla C2075 graphic card which is can handle up to 90 million cells. To assure convergence of the numerical simulations, the simulation time was set to 20 periods for each simulation. Additionally, the convergence was checked after the simulations were finished. The material of orthopedic devices is set to perfect electric conductor (PEC), and all the numerical results are normalized to a whole body average SAR of 2 W/kg. The SAR distribution is studied for each case.

4.2. Bone plate system

To ensure a comprehensive comparison, the 1g local average peak SAR value at device is extracted for each configuration of femur and humerus system. Tables 3 and 4 show the value for femur and humerus system. For each numerical result, whole-body average SAR is normalized to 2 W/kg. Since the interaction between RF induced field and implant is dependent on the physical structure of device, the heating effect variations related to the length of plate and screw are studied separately. For femur system, the plate length varies from 100 to 300 mm, and the screw length changes from 10 to 32 mm. For humerus system, the screw dimension is the same as femur system. But the plate length varies only from 100 to 250 mm due to the limit of bone structure. The plate length is studied at first for minimum and maximum screw length. Then the screw length is investigated under the worst case of plate length study which has the highest 1g average peak SAR value for in-vivo simulation. Figures 8 13 show the results which are corresponding to femur and humerus plate system. The solid and dash curve and indicate the in-vivo and in-vitro results, respectively.

Plate length (mm) Screw length (mm) 1.5 T/64 MHz 3 T/128 MHz
In-vivo SAR1g (W/kg) In-vitro SAR1g (W/kg) In-vivo SAR1g (W/kg) In-vitro SAR1g (W/kg)
100 10 64.20 125.97 79.75 80.90
150 10 94.82 178.62 74.52 64.01
175 10 107.00 190.44 68.50 50.20
200 10 116.65 188.87 63.37 44.69
225 10 117.00 185.04 63.10 37.72
250 10 123.00 169.75 61.23 37.27
275 10 117.00 149.81 53.80 35.33
300 10 105.00 134.91 42.37 38.53
100 32 85.02 100.22 88.26 71.90
150 32 108.17 135.90 55.48 47.74
200 32 104.91 140.27 51.56 41.59
250 32 111.73 123.17 48.94 37.09
300 32 79.94 128.93 27.77 40.70
250(1.5 T) 100(3 T) 15 120.00 150.91 79.30 72.19
250(1.5 T) 100(3 T) 20 121.00 135.71 76.20 68.00
250(1.5 T) 100(3 T) 25 123.00 132.15 64.2 66.52

Table 3.

Peak 1g averaged SAR of femur system for in-vivo and in-vitro cases.

Plate length (mm) Screw length (mm) 1.5 T/64 MHz 3 T/128 MHz
In-vivo SAR1g (W/kg) In-vitro SAR1g (W/kg) In-vivo SAR1g (W/kg) In-vitro SAR1g (W/kg)
100 10 38.02 135.61 65.47 90.51
150 10 63.74 192.14 94.68 59.90
200 10 69.47 204.57 81.84 45.54
250 10 104.57 193.61 86.73 41.50
100 32 30.70 92.17 63.46 64.6
150 32 54.10 124.76 85.39 53.70
200 32 55.90 161.97 75.19 43.39
250 32 109.00 156.38 108.92 42.51
250 15 95.53 161.64 77.82 35.33
250 20 91.02 163.55 72.91 38.94
250 25 88.27 164.54 68.40 41.32

Table 4.

The peak 1g average SAR value of humerus system for in-vivo and in-vitro cases.

Figure 8.

The femur bone plate length study of 10 mm screw for 1.5 T (left) and 3 T (right).

Figure 9.

The femur bone plate length study of 32 mm screw for 1.5 T (left) and 3 T (right).

Figure 10.

The femur screw length study for 1.5 T (left) and 3 T (right).

Figure 11.

The humerus bone plate length study of 10 mm screw for 1.5 T (left) and 3 T (right).

Figure 12.

The humerus bone plate length study of 32 mm screw for 1.5 T (left) and 3 T (right).

Figure 13.

The humerus screw length study for 1.5 T (left) and 3 T (right).

4.3. Hip prostheses

For hip prostheses, the 1g average local peak SAR value at device is also extracted for each configuration. Table 5 shows the value for hip system of various dimensions. The height of hip prostheses stem ranges from 100 to 170 mm. For in-vivo simulation, the stem is inserted into the bone marrow. And for the trochanter region, the hip prostheses is touching with soft tissue and muscle. Figure 14 represents the results of hip prostheses. The solid and dash curve and indicate the in-vivo and in-vitro results, respectively.

Stem height (mm) 1.5 T/64 MHz 3 T/128 MHz
In-vivo SAR1g (W/kg) In-vitro SAR1g (W/kg) In-vivo SAR1g (W/kg) In-vitro SAR1g (W/kg)
100 83.2764 270.843 43.4746 55.4143
110 81.5782 260.502 35.8247 56.3111
120 77.8568 248.116 24.4627 57.0498
130 74.9259 247.635 21.9093 60.352
140 64.5142 237.51 16.3059 61.7026
150 62.8772 205.328 13.1482 63.2055
160 59.6273 221.781 11.5599 63.9114
170 55.0469 213.602 11.1877 63.8915

Table 5.

Peak 1g average SAR of hip prostheses system for in-vivo and in-vitro cases.

Figure 14.

The hip prostheses stem length study for 1.5 T (left) and 3 T (right).

4.4. Tibia intramedullary nails

The 1g average local peak SAR value at device is also extracted for each configuration of tibia intramedullary nails. The length of stem ranges from 255 to 360 mm. The entire nail is penetrated into the bone marrow. The four screws are inserted perpendicularly through the nail and bone. Table 6 shows the value for nail system of various dimensions. Figure 15 represents the results of tibia intramedullary nails. The solid and dash curve and indicate the in-vivo and in-vitro results, respectively.

Nail length (mm) 1.5 T/64 MHz 3 T/128 MHz
In-vivo SAR1g (W/kg) In-vitro SAR1g (W/kg) In-vivo SAR1g (W/kg) In-vitro SAR1g (W/kg)
255 77.6968 136.331 93.5532 55.4068
270 77.6346 129.249 93.2341 53.6038
285 78.9892 122.28 89.1767 49.8946
300 82.6751 115.745 91.5648 46.8385
315 81.7577 109.28 92.7346 44.0529
330 74.7444 103.319 88.9989 41.6544
345 66.6095 97.3232 90.7795 39.3275
360 67.3469 91.8168 90.1809 37.1875

Table 6.

Peak 1g average SAR of tibia nails system for in-vivo and in-vitro cases.

Figure 15.

The nail length study for 1.5 T (left) and 3 T (right).

Advertisement

5. Summary

From the comparison between in-vitro and in-vivo simulations, the RF-induced heating are different because of the variance of incident electric field and surrounding medium. For incident field study, the antenna resonance effect would mainly lead to a heating issue for both in-vitro and in-vivo situation. Although the wavelength of human muscle and gelled-saline nearly equals to each other, due to the variance of incident RF field, the device dimension causing the resonance would be different. Hence, the trend of peak 1g average SAR value along with plate length is unlike from in-vitro to in-vivo circumstance. Additionally, when the screw is inserted across the human bone into the muscle, a huge amount of power would dissipated to the human tissue through the screw tip so that induce a large peak SAR value.

Based on the comparison result, conservatively, the in-vitro method, such as ASTM phantom, could be used to assess RF-induced heating. However, to accurately assess the RF-induced heating in heterogeneous human body with implantable medical device, due to the limit of homogeneous ASTM phantom, it still needs some improvement to handle several particular cases, especially, when the implantable device is penetrating through various human tissues and organs.

Advertisement

Disclaimer

The mention of commercial products, their sources, or their use in connection with material reported herein is not to be construed as either an actual or implied endorsement of such products by the Department of Health and Human Services.

References

  1. 1. Schenck JF. Health effects and safety of static magnetic fields. In: Shellock FG, editor. Magnetic Resonance Procedures: Health Effects and Safety. Boca Raton, FL: CRC; 2001. p. 1-30
  2. 2. Zaremba LA. FDA guidance for magnetic resonance system safety and patient exposures: Current status and future considerations. In: Shellock FG, editor. Magnetic Resonance Procedures: Health Effects and Safety. Boca Raton, FL: CRC; 2001. p. 183-196
  3. 3. U.S. Food and Drug Administration, Center for Devices and Radiological Health. MDR Data Files. Available at: www.fda.gov/CDRH/mdrfile.html. [Accessed: April 1, 2003]
  4. 4. U.S. Food and Drug Administration, Center for Devices and Radiological Health. Manufacturer and User Facility Device Experience Database (MAUDE): File Formats for FOI Releasable Data. Available at: www.fda.gov/cdrh/maude.html
  5. 5. Shellock FG. Reference Manual for Magnetic Resonance Safety, Implants, and Devices: 2004 Edition. Los Angeles, CA: Biomedical Research Publishing; 2004
  6. 6. Shellock FG. Pocket Guide to MR Procedures and Metallic Objects: Update 2001. Philadelphia, PA: Lippincott Williams &Wilkins; 2001
  7. 7. Shellock FG. Magnetic Resonance Procedure: Health Effects and Safety. Boca Raton, FL: CRC; 2001
  8. 8. Edelman RR, Shellock FG, Ahladis J, Practical MRI. For the technologist and imaging specialist. In: Edelman RR, Hesselink J, editors. Clinical Magnetic Resonance. Philadelphia: WB Saunders; 1990. p. 80-115
  9. 9. Persson BRR, Stahlberg F. Health and Safety of Clinical NMR Examinations. Boca Raton, FL: CRC Press; 1989. p. 59-79
  10. 10. Shellock FG, Kanal E. Magnetic Resonance: Bio Effects, Safety, and Patient Management. 2nd ed. New York: Lippincott-Raven; 1996. p. 25-48
  11. 11. Shellock FG. Biological effects and safety aspects of magnetic resonance imaging. Magnetic Resonance Quarterly. 1989;5:243-261
  12. 12. Kanal E, Shellock FG, Talagala L. Safety considerations in MR imaging. Radiology. 1990;176:593-606
  13. 13. Morvan D, Leroy-Willig A, Jehenson P, Cuenod CA, Syrota A. Temperature changes induced in human muscle by radiofrequency H-1 coupling: Measurement with an MR imaging diffusion technique. Radiology. 1992;185:871-874
  14. 14. Shellock FG. MRI Bioeffects and safety. In: Atlas S, editor. Magnetic Resonance Imaging of the Brain and Spine. New York: Raven Press; 1990
  15. 15. Shellock FG. Thermal responses in human subjects exposed to magnetic resonance imaging. Annals of the New York Academy of Sciences. 1992:260-272
  16. 16. Bottomley PA, Redington RW, Edelstein WA, et al. Estimating radiofrequency power deposition in body NMR imaging. Magnetic Resonance in Medicine. 1985;2:336-349
  17. 17. Bottomley PA, Edelstein WA. Power deposition in whole body NMR imaging. Medical Physics. 1981;8:510-512
  18. 18. Shellock FG. Magnetic resonance imaging: bioeffects, safety, and patient management [J]. Reviews of Magnetic Resonance in Medicine. 1992;4:21-63
  19. 19. Schaefer DJ, Barber BJ, Gordon CJ, et al. Thermal effects of magnetic resonance imaging. In: Book of Abstracts, Society for Magnetic Resonance in Medicine. Vol. 2. Berkeley, CA: Society for Magnetic Resonance in Medicine. 1985. p. 925
  20. 20. Gordon CJ. Thermal physiology. In: Biological Effects of Radiofrequency Radiation. Washington, DC: EPA-600/8-83-026A; 1984 P 4-1-4-28
  21. 21. Gordon CJ. Effect of radiofrequency radiation exposure on thermoregulation. ISI Atlas of Science, Animal and Plant Sciences. 1988;1:245-250
  22. 22. Gordon CJ. Normalizing the thermal effects of radiofrequency radiation: Body mass versus total body surface area. Bioelectromagnetics. 1987;8:111-118
  23. 23. ASTM International. Standard Test Method for Measurement of radio frequency induced heating near passive implants during magnetic resonance imaging ASTM Standard F2182-11. ASTM International: West Conshohocken, PA; 2011 www.astm.org
  24. 24. Powell J, Papadaki A, Hand J, Hart A, McRobbie D. Numerical simulation of SAR induced around Co-Cr-Mo hip prostheses in situ expose to RF fields associated with 1.5 and 3 T MR body coils. Magnetic Resonance in Medicine. 2012;68:960-968
  25. 25. Liu Y, Chen J, Shellock FG, et al. Computational and experimental studies of an orthopedic implant: MRI-related heating at 1.5-T/64-MHz and 3-T/128-MHz. Journal of Magnetic Resonance Imaging. 2013;37(2):491-497
  26. 26. Liu Y, Shen J, Kainz W, et al. Numerical investigations of MRI RF field induced heating for external fixation devices. Biomedical Engineering Online. 2013;12(1):12
  27. 27. Guo R, Zheng J, Chen J, et al. RF-induced heating comparison between in-vivo and in-phantom for 1.5 T MRI. Electromagnetic compatibility (EMC), 2016 IEEE International Symposium on IEEE, 2016: 121-125
  28. 28. Mohsin SA, Sheikh NM, Abbas W. MRI induced heating of artificial bone implants. Journal of Electromagnetic Waves and Applications. 2009;23:799-808
  29. 29. Li D, Zheng J, Liu Y, et al. An efficient approach to estimate MRI RF field induced in vivo heating for small medical implants. IEEE Transactions on Electromagnetic Compatibility. 2015;57(4):643-650
  30. 30. Zheng J, Li D, Chen J, et al. Numerical study of SAR for multi-component orthopaedic hip replacement system during MRI. Electromagnetic Compatibility (EMC), 2016 IEEE International Symposium on IEEE, 2016: 116-120
  31. 31. Zeng Q, Wang Q, Zheng J, et al. MRI induced heating for fully implanted, partially implanted and minimally implanted medical electrode leads. Electromagnetics in Advanced Applications (ICEAA), 2015 International Conference on IEEE, 2015: 1590-1591
  32. 32. Zeng Q, Zheng J, Chen J. MRI Induced heating for fully implanted, partially implanted and minimum implanted medical electrode leads. Applied Computational Electromagnetics (ACES), 2015 31st International Review of Progress in IEEE, 2015:1-2
  33. 33. Hand JW. Modelling the interaction of electromagnetic fields (10 MHz–10 GHz) with the human body: Methods and applications. Physics in Medicine and Biology. 2008;53(16):R243
  34. 34. Andreo P. Monte Carlo techniques in medical radiation physics. Physics in Medicine and Biology. 1991;36(7):861
  35. 35. Yee K. Numerical solution of initial boundary value problems involving Maxwell’s equations in isotropic media. IEEE Transactions on Antennas and Propagation. 1966;14(3):302-307
  36. 36. Patankar SV. Numerical Heat Transfer and Fluid Flow. New York: Hemisphere; 1980. p. 25-73
  37. 37. Christ A, Kainz W, Hahn EG, et al. The virtual family—Development of surface-based anatomical models of two adults and two children for dosimetric simulations. Physics in Medicine and Biology. 2009;55(2):N23

Written By

Ran Guo, Jianfeng Zheng and Ji Chen

Submitted: June 7th, 2017 Reviewed: October 2nd, 2017 Published: December 20th, 2017