On the RF safety of titanium mesh head implants in 7 T MRI systems: an investigation

Mazin Mustafa; Nur Izzati Huda Zulkarnain; Alireza Sadeghi‐Tarakameh; Andrea Grant; David Darrow; Can Ozutemiz; Yigitcan Eryaman

doi:10.1002/mrm.30477

. 2025 Feb 25;94(1):414–423. doi: 10.1002/mrm.30477

On the RF safety of titanium mesh head implants in 7 T MRI systems: an investigation

Mazin Mustafa ^1,^✉, Nur Izzati Huda Zulkarnain ¹, Alireza Sadeghi‐Tarakameh ¹, Andrea Grant ¹, David Darrow ², Can Ozutemiz ³, Yigitcan Eryaman ¹

PMCID: PMC12021313 PMID: 40007209

Abstract

Purpose

Patients undergoing craniofacial surgery for skull reconstruction may have titanium mesh implants. The safety risks related to 7 T MRI with these patients are not well understood. This study investigates the RF heating of titanium mesh head implants at 7 T.

Methods

A simulation model for a 7 T birdcage head coil was developed and validated against $|B_{1}^{+}|$ , 1 g‐averaged specific absorption rate (SAR), and temperature measurements in the presence of a titanium mesh. Various mesh sizes and shapes at different angular positions were simulated to determine the worst‐case scenario in a spherical phantom in addition to the effect of rounding the mesh edges. Full‐wave electromagnetic and bioheat thermal simulations were conducted on anatomical human models.

Results

Preliminary results indicate an increase in the local SAR near the meshes depending on the shape, size, and location. The maximum absolute temperatures in the head were, on average, around 38.2°C after 15 min of RF power exposure, corresponding to 3.2 W/kg whole‐head SAR without a titanium mesh implant. The maximum absolute temperatures did not significantly change after introducing the titanium mesh implants, and the highest temperature was 38.4°C, observed near the cerebellum and the facial muscles. The maximum local increase in temperature was observed at the vicinity of the mesh as 2.8°C. Finally, it was shown that large mesh implants can negatively impact $|B_{1}^{+}|$ field.

Conclusions

Small rounded titanium mesh head implants can be generally safe for 7 T MRI scans under the standard guidelines. Avoiding sharp corners and edges may reduce the chances of RF safety risks.

Keywords: 7 T, head implants, MRI, RF safety, titanium mesh

1. INTRODUCTION

Titanium mesh implants are commonly used in craniofacial surgery procedures for skull reconstruction after injury or surgery. ¹ , ² , ³ , ⁴ Titanium is preferred for such implants due to its “bio compatibility, low infection rate, good mechanical strength, and low cost.” ³ Although it is considered a paramagnetic material, the electrical conductivity of titanium can raise safety concerns if high currents are induced on the mesh. ⁵ , ⁶ , ⁷ Common types of titanium (Ti) alloys for human implants are Ti‐6Al‐4V and Ti‐6Al‐7N. ⁸

The 7 T MRI provides many advantages for neuroimaging, including improved spatial resolution, increased SNR, and increased contrast‐to‐noise ratio. ⁹ , ¹⁰ , ¹¹ , ¹² Since the Food and Drug Administration (FDA) approved the first clinical 7 T MR system Magnetom Terra, Siemens Healthineers (Erlangen, Germany) in 2017, it has been frequently used for neuroimaging in research and clinical environments. The majority of brain scans are conducted using a 7 T single transmit (Tx)/32 receive (Rx) head coil. A few investigations considered standardized safety testing for various metallic implants, including titanium skull implants and aneurysm clips at 7 T. ¹³ , ¹⁴ , ¹⁵ These investigations indicated that titanium mesh implants for the skull may be acceptable for human subjects undergoing MRI examinations. On the other hand, several studies reported on local specific absorption rate (SAR) and temperature increases for various implants at 7 T, ¹⁶ , ¹⁷ including titanium meshes. However, a systematic study is still needed to investigate the effects of the mesh geometry, orientation, and location in the human head.

Full‐wave electromagnetic (EM) and thermal simulations are frequently performed to investigate the RF heating of passive implants at ultrahigh field MRI. ¹⁸ However, physical measurements and validation of simulation results are also critical for patient safety. Different workflows are used for this purpose, for example, a comparison of simulated and measured $|B_{1}^{+}|$ ‐efficiency maps is a commonly used method for validating the EM simulation models of ultrahigh fields–MRI coils. This effort requires measuring the $|B_{1}^{+}|$ distribution of the coil (usually in a phantom mimicking human head) using an MR scanner and making comparisons with simulations. ¹⁹ , ²⁰ Local SAR comparisons are also frequently performed for RF safety validation studies. Measuring SAR directly with an MR scanner is not possible; instead, temperature increase is measured using either MR thermometry ²¹ or fluoroscopic temperature probes ²² , ²³ , ²⁴ and then used to calculate the local SAR. One challenge of using MR thermometry for estimating local SAR for implant safety is the difficulty in measuring the MR signal around metallic objects. The severity of $T_{2}^{*}$ effects can prevent obtaining accurate phase information near the metal, which is critical for estimating the peak temperature. As an alternative, fluoroscopic probes can measure the temperature increase around implants accurately. The main limitation of this approach is the finite number of locations at which the measurement can be conducted. Because estimating the hottest spot on a complex‐shaped implant is not always easy, other alternative approaches should be considered.

In this work, the heating around titanium meshes implants used for skull repair at 7 T was investigated. SAR and temperature around mesh of different sizes, positions, and geometries were evaluated using EM and thermal simulations. Physical measurements validation studies were conducted, comparing $|B_{1}^{+}|$ , 1 g‐averaged SAR, and temperature to the simulation results.

2. METHODS

2.1. Head coil modeling

For this study, a computer simulation model was developed for a shielded 7 T two‐port high‐pass birdcage RF coil emulating a commercial 1Tx/32Rx head coil at 297.2 MHz following guidelines from the literature. ²⁵ , ²⁶ The RF coil height was 20 cm, and the diameter was 30 cm, with a dielectric holder between the RF coil and the shield as seen in Figure 1A–C. For the $|B_{1}^{+}|$ validations, the RF coil was tuned to resonate with a light bulb–shaped head phantom made of polyvinylpyrrolidone (PVP) and agar inside a plexiglass container also shown in Figure 1G. The phantom was 3D printed using the material WaterShed Stereolithography 11122. The relative dielectric constant and the electrical conductivity of the gel inside the phantom were measured as 50.5 and 0.56 S/m, respectively, using DAKS12 probe from SPEAG (Zurich, Switzerland). The coil was excited with a quadrature scheme using two RF ports that were matched to 50 ohm at the Larmor frequency to maximize the power delivery. For the titanium mesh, a Computer‐aided design (CAD) model based on Integra (Plainsboro, NJ) product was developed as illustrated in Figure 1E and Figure S1. The titanium mesh was measured 0.6 mm thick. It was implemented as a solid structure based on a 3D scanned model with titanium properties, electrical conductivity of 2.4 × 10⁶ S/m, mass density of 4500 kg/m³, thermal conductivity of 21 W/m‐K, and specific heat capacity of 552 J/kg‐K. ²⁷ , ²⁸ In order to evaluate the SAR and the temperature around the mesh, a cylindrical phantom was considered with a radius of 70 mm and height of 160 mm filled with PVP gel with dielectric constant of 54.59, electrical conductivity of 0.9 S/m, and mass density of 1200 kg/m³ as recommended by the calibration requirements of the electric field (E‐field)/dosimetric probe, whereas the thermal conductivity was 0.43 W/m‐K and specific heat capacity of 3824 J/kg‐K. The simulation models were implemented in ANSYS Electronics Desktop (Canonsburg, PA) and CST Studio Suite (Darmstadt, Germany).

The modeling of the head coil Tx, titanium mesh, phantoms, and anatomical human models. (A) A cylindrical phantom and a flat titanium mesh. (B) A cross‐sectional view of the phantom and mesh position inside the coil. (C) Head coil model and shield. (E) The 3D model of the titanium mesh. (F) The experimental setup for data acquisition. (G) The light bulb–shaped head phantom model. (D) and (H) are the human voxel models used for electromagnetic and thermal simulations with a titanium mesh head implant inside the RF coil for Duke: 34 years (male) and Ella: 26y (female), respectively. The red arrows points to the titanium mesh locations that are illustrated by the solid black line. Tx, transmit.

2.2. Experimental data acquisition

A system capable of measuring the local SAR on a finite number of sample points along a predetermined 3D trajectory inside a phantom was built. The system was based on the design introduced and utilized in earlier work, with minor modifications on the electronic subsystem. ²⁹ , ³⁰ It comprised a commercial SAR probe in addition to the electromechanical setup, which is capable of moving the probe in three dimensions inside a Faraday cage. Similar to the earlier work, the setup has three stepper motors enabling data acquisition in three orthogonal axes with a working volume of 500 mm × 500 mm × 700 mm. To measure SAR, a high‐precision, isotropic E‐field/dosimetric probe EX3DV4 SPEAG (Zurich, Switzerland) was used. In principle, this system can be used to measure SAR around any implant excited with an arbitrary RF coil. ³¹ Given that this system is located in a controlled safety lab, precise power monitoring can be performed, enabling accurate validation studies to be conducted in line with the objectives of this paper. Two physical measurement validation studies were conducted. The first one was targeted toward validating the simulation model of the coil. For this purpose, $|B_{1}^{+}|$ ‐efficiency maps were acquired μT/√W using the actual flip angle imaging (AFI) technique ³² in the phantom shown in Figure 1G. The simulated $|B_{1}^{+}|$ ‐efficiency maps (without the implant) were compared to physical measurement maps.

The second validation study involved local SAR and temperature measurements in the RF safety lab. The transmitter of the 7 T 1Tx/32Rx head coil was used to generate RF excitation inside the Faraday cage. The coil was loaded with a cylindrical phantom filled with a gel as mentioned in the previous section. A titanium mesh (size 56.5 mm × 56.5 mm) was placed flat at the bottom of the phantom as seen in Figure 1A,B. Using the previously described 3D measurement setup and the probe setup shown in Figure 1F, point‐wise SAR was measured with a spatial sampling rate of 2 mm in x–y plane, whereas the z‐axis resolution was 4.17 mm at three axial planes above the implant surface. SAR was then averaged within a 10 mm × 10 mm × 8.34 mm volume, yielding approximately 1 g of PVP. The total incident RF power was about 24 W at 297.2 MHz. For the temperature measurement, four fiber optic temperature probes were placed 1 mm above the titanium mesh as shown in Figure S2. The probes positions were chosen in order to maximize the variety of temperature increases measured in the vicinity of the mesh. An RF power of 22.5 W was applied for 10 min (starting from steady‐state temperature) and then the temperatures were recorded. The rationale behind these experiments was to validate the thermal simulation at different locations. Therefore, the probe positions were chosen where a range of temperature increases was expected.

2.3. Titanium mesh modeling

Titanium mesh implants are usually thin metallic structures with high electrical conductivity and decent mechanical flexibility in order to fit skull curvature. The typical thickness for these meshes are less than 1 mm. For these reasons, it is valid to implement titanium meshes as surface boundary conditions representing an ideal perfect electric conductor for EM simulations. This choice can reduce the modeling complexity, but for better accuracy a solid model of the titanium mesh with titanium physical properties was considered for the validation scenarios and the simulations inside anatomical human models. This choice also provides better results for the thermal simulations avoiding perfect thermal conductor or thin film representations. The mesh was based on a cell shape that repeats itself in both lateral directions. To test different mesh sizes, the titanium mesh cell models were fixed at a size of 1 cm × 1 cm for convenience. Initially, various mesh shapes were studied based on commercially available products, in addition to the extreme case of treating the titanium mesh implant as a solid sheet of metal as shown in Figure S3. Furthermore, the angular position of the mesh in a spherical phantom was investigated as shown in Figure 2A. The objective from these tests was to determine the worst‐case scenario in the phantom. First, the location with the maximum 1 g‐average SAR was identified for a mesh with 6 × 6 cells size. Then the maximum 1 g‐average SAR at the vicinity of meshes (between size 3 × 3 and 8 × 8 cells) were investigated at that location.

(A) A titanium mesh on a spherical phantom. The radius of the phantom is 100 mm and the total mass of the spherical phantom is about 5 kg. The titanium mesh was treated as a PEC boundary condition for simplicity. (B) Peak 1 g‐averaged SAR values on spherical phantom versus azimuth and elevation angles. Results show abrupt changes because the high SAR values are sensitive to the titanium mesh resonance with the head coil transmitter. (C) Results for 1 g‐average pSAR in W/kg of various square mesh sizes on the spherical head phantom at 45° angle. PEC, perfect electric conductor; pSAR, peak specific absorption rate; SAR, specific absorption rate.

2.4. Anatomical human models

After determining the worst‐case scenario from a spherical phantom, the mesh design was chosen for further investigations on two adult anatomical human models, viz. Duke and Ella, with frequency‐dependent electrical properties and thermal tissue properties obtained from the IT'IS Foundation (Zurich, Switzerland), ³³ including the Pennes bioheat equation metabolic and perfusion rates. ³⁴ , ³⁵ Those models are shown in Figure 1D,H inside the head coil Tx model with a titanium mesh implant. For each human model, a full‐wave EM simulation was performed, without a titanium mesh, in order to find the RF power that corresponds to a whole‐head SAR of 3.2 W/kg (Institute of Electrical and Electronics Engineers C95.3 standard) in the head according to the International Electrotechnical Commission 60601‐2‐33–recommended limits for normal operating mode. ³⁶ The RF power levels were found to be about 36.2 and 34.9 W for the Duke and Ella models, respectively.

The thermal simulations started from the steady‐state thermal solutions for each model obtained from the linear bioheat model with perfusion and implementing a heat‐transfer coefficient h = 6 W/m²‐K on the skin. ³⁷ , ³⁸ The initial temperature distributions were obtained by allowing the models to reach their steady‐state temperatures via Pennes bioheat equation mechanisms without RF power instead of assuming a constant initial temperature everywhere, for example, 37°C. This approach ensures that the initial temperatures in the thermal simulations follow a realistic human temperature distribution. ³⁷ , ³⁸ Moreover, to evaluate SAR accurately, a large portion of the torso was also included in the human simulation models. ³⁹ The EM thermal‐ coupled simulations were repeated for several sizes of titanium meshes introduced to the human models on the back of the head based on the worst‐case investigation on the spherical phantom. The titanium meshes were placed on the skull, under the scalp as in Figure 1 and Figure S4. Also, a relatively large mesh was considered as shown in Figure S5 in order to investigate the impact of titanium mesh on $|B_{1}^{+}|$ distribution in the brain. Additionally, the effect of trimming the titanium mesh and gradient coil heating in a phantom was also considered.

3. RESULTS

3.1. Simulation model validations

The first validation result was the $|B_{1}^{+}|$ ‐efficiency map at a central axial cut inside the light bulb head phantom from Figure 3A,B. The $|B_{1}^{+}|$ ‐efficiency map shows a quantitative agreement (normalized RMS error 5.05%). The comparison between the simulated and the physical measurement results for the 1 g‐average SAR also shows a good quantitative agreement with a reasonable numerical error (normalized RMS error 10.3%) as illustrated in Figure 3E,F. Additionally, the temperature measurements at four different positions close to the titanium mesh also show good agreement. The temperature versus time results inside the cylindrical phantom are illustrated in Figure 3C,D,G,H. Moreover, the results from angular sweep of a titanium mesh on the spherical phantom are shown in Figure 2B. The 1 g‐averaged peak specific absorption rate (pSAR) results for the different mesh sizes on the spherical phantom are summarized in Figure 2C.

The $|B_{1}^{+}|$ field comparison on an axial cut between (A) simulations and (B) measurements using AFI pulse sequence. The validation for the 1 g‐averaged SAR results measured at 6.2 mm above the titanium mesh in an axial cut of 72 mm × 72 mm. (E) 1 g‐average SAR simulation results. (F) 1 g‐average SAR measurement results. The NRMSE between the simulation and measurement results were 5.05% and 10.3% for $|B_{1}^{+}|$ and 1 g‐average SAR, respectively. A comparison of the change in temperature $(∆ T)$ versus time between the simulations and measurements near the titanium mesh inside the cylindrical phantom at (C) position 1, (D) position 2, (G) position 3, and (H) position 4. These positions are illustrated in Figure S2. NRMSE, normalized RMS error.

3.2. Human models with implants

The initial temperature distributions and the final absolute temperatures with RF power for 15 min from steady‐state (without a mesh) are shown on central sagittal cuts in Figure S6 for reference. The change in the temperature $(∆ T)$ over time for two scenarios (with and without the mesh) is shown in Figure 4A,B,E,F. Furthermore, the final absolute temperature distributions for the same scenarios and the same RF power exposure after 15 min are shown in Figure 4C,D,G,H. The maximum final absolute temperatures for human models were 38.4° and 38.2°C, whereas the maximum temperatures without a mesh were 38.3° and 38.2°C for Duke and Ella human models, respectively. The maximum local increase in temperature was observed at the vicinity of the mesh as 2.8°C. In Figure 5, the $|B_{1}^{+}|$ ‐efficiency maps are illustrated before and after a large titanium mesh implant on Duke's model.

The change in temperature $(∆ T)$ distributions due to RF power exposure for 15 min in Duke and Ella before and after introducing a 7 × 7 cells titanium mesh. (A) and (E) are the results without a titanium mesh. (B) and (F) are the results with the titanium mesh. Final absolute temperature distributions after 15 min of RF exposure with and without a 7 × 7 cells titanium mesh for Duke and Ella. (C) and (G) are the results without a titanium mesh. (D) and (H) are the results with the titanium mesh. Arrows point to the mesh locations. For all subfigures, Duke and Ella results are on top and bottom rows, respectively. Note that the maximum absolute temperatures are at the CSF and facial muscles, and they did not change.

The $|B_{1}^{+}|$ ‐efficiency maps for Duke with a large titanium mesh covering the right side of the head. (A) Without titanium mesh. (B) With titanium mesh.

4. DISCUSSION

The simulation results indicate little to no effect on the final absolute maximum temperatures before and after introducing the titanium mesh implants. The increase in SAR and temperature depends on the shape, size, and location of the implant. On the other hand, the maximum absolute temperatures in the head after 15 min of RF exposure were located far away from the mesh, closer to the medulla and jaws. Although the simulation results in the human models indicate an increased power absorption near the mesh edges, the mesh was placed under the scalp where the initial temperatures are slightly lower than the center of the brain. Hence, the maximum temperatures in the head after 15 min of RF power were not considerably different from the case without a mesh. Therefore, maximum absolute temperatures in the human models before and after titanium mesh were found to be very similar (all below 38.4°C). The head average SAR level was based on the normal operating mode head SAR limit (3.2 W/kg) as stated in the IEC 60601‐2‐33:2022. The exposure duration of 15 min was based on the FDA‐2019‐D‐2837 document. ⁴⁰

Due to the difficulty of an accurate noninvasive in vivo evaluation of temperature during MRI scans, ⁴¹ numerical simulations were conducted with anatomical human models in addition to phantoms. In these human model simulations, various mesh sizes at approximate location corresponding to the worst‐case scenario in phantom were simulated. ⁵¹ Justifying that worst‐case heating in a phantom approximates the true worst‐case heating in human subjects is challenging. And it would require further investigation using additional implant placement configurations and human models. A complete statistical analysis needs to be conducted to predict the true “worst‐case heating” condition. Such an effort would be crucial for identifying the intersubject variability of the issue, which should be explored in future studies.

The loading effects due to titanium meshes were minimal for the phantom studies and the sizes considered for worst‐case calculations. However, as the mesh size increases the loading effect is expected to increase. Therefore, it is important to consider this effect when conducting SAR and temperature simulations with relatively large meshes that cover significant portion of the skull. Another important result to discuss here is the effect of the titanium mesh on the $|B_{1}^{+}|$ ‐efficiency maps. When compared to the no‐mesh scenario, it was clear from the results that large titanium meshes can reduce the $|B_{1}^{+}|$ field strength significantly, especially at the superior regions of the brain. The metallic structure of the mesh blocks EM fields from penetrating the head tissues and as a result the $|B_{1}^{+}|$ field is drastically reduced. These cases in which large portions of the skull are covered with a titanium mesh are common in cranioplasty. ⁴² , ⁴³ These scenarios might prevent a high‐quality scan from being performed on the patient because it would be challenging to acquire MR signal from a large portion of the brain.

Additionally, the effect of trimming the edges of the titanium mesh reduced the 1 g‐average pSAR dramatically as shown in Figure S7. This result can be used as a general guideline for surgeons who are performing implantation. Moreover, it was also confirmed that the gradient coils did not cause any significant heating, as discussed in the Supporting Information (Figure S8). Unlike RF heating in which E‐fields inside the tissue are mainly responsible for heating, the surface currents flowing on the implant heat the implant itself. Therefore, heating due to gradient fields is expected to be minimal as demonstrated in the literature as well. ⁴⁴ , ⁴⁵ , ⁴⁶ , ⁴⁷ , ⁴⁸ , ⁴⁹

5. CONCLUSIONS

Our findings show that the local SAR and temperature may increase at the vicinity of titanium mesh implants during 7 T MRI head scans. It was concluded that patients with titanium mesh implants comparable to those analyzed in this work can be scanned safely at 7 T using a similar 1Tx32Rx head coil. It was also observed that the corners and sharp edges of the mesh created the highest charge density and therefore high local SAR values. Thus, it is recommended to avoid such edges and corners for titanium mesh craniofacial surgeries in order to eliminate RF heating risks. Different mesh types, that is, pattern designs, did not have any significant impact on either the 1 g‐average pSAR or the maximum temperatures according to our simulations results. However, the geometry (size and shape) and the location of the metallic implant were the most important factors determining the RF heating. Finally, the reduced $|B_{1}^{+}|$ fields caused by large titanium meshes was reported. Further investigation may be needed to tackle this challenge, perhaps utilizing parallel transmission coils as previously utilized for deep brain stimulation electrodes. ⁵⁰

FUNDING INFORMATION

This work was partially supported by National Institutes of Health (NIH), grants NIBIB P41 EB027061 and NINDS R01 NS115180.

Supporting information

Figure S1. The 4 × 4 cells titanium mesh CAD models obtained as (a) 3D scanning STL mesh model. (b) 3D volumetric CAD model. (c) 2D flat surface CAD model.

Figure S2. Positions of the temperature probes 1 mm above the titanium mesh. P1 is the control position.

Figure S3. A comparison for different types of titanium mesh implants size 4 cm × 4 cm. (a) The mesh implants on the light‐bulb head phantom. (b) The titanium mesh designs. (c) The 1 g–average SAR distribution corresponding to 1 W total input power (top view). (d) The temperature distribution after 15 min of 17.68 W RF power starting from 20°C ambient temperature (top view). The maximum variation was 2% from the average in both the EM and thermal simulation results among the four different scenarios.

Figure S4. Placement of titanium mesh model on skull inside the scalp tissue in the anatomical human simulation models. The mesh was curved to better fit the curvature of the skull.

Figure S5. Duke model with a large titanium mesh implant covering the right side of the head.

Figure S6. Temperature distributions on a central sagittal cut for Duke (top row) and Ella (bottom row) without a titanium mesh implant. The left column is the initial steady–state temperatures and the right column is the absolute (final) temperature after 15 min RF power exposure.

Figure S7. A simple comparison for the resulting 1 g–average SAR when the mesh shape is (a) square patch, vs. (b) circular patch with rounded edges, using the same power level. The rounded edges resulted in a much lower 1 g‐average pSAR values as expected.

Figure S8. An illustration of the experiment setup with a titanium mesh inside the PVP phantom with 3 fiber optic temperature sensors installed at (1) edge of the mesh, (2) center of the mesh, and (3) an arbitrary position for control. The container was completely filled with the PVP phantom when running the experiment.

MRM-94-414-s001.docx^{(5.5MB, docx)}

Mustafa M, Zulkarnain NIH, Sadeghi‐Tarakameh A, et al. On the RF safety of titanium mesh head implants in 7 T MRI systems: an investigation. Magn Reson Med. 2025;94:414‐423. doi: 10.1002/mrm.30477

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36. Commission IE, others . Medical electrical equipment‐part 2–33: particular requirements for the basic safety and essential performance of magnetic resonance equipment for medical diagnosis. IEC 60601‐2‐33 Ed 40 2022.
37. van Lier ALHMW, Kotte ANTJ, Raaymakers BW, Lagendijk JJW, Berg CAT. Radiofrequency heating induced by 7T head MRI: thermal assessment using discrete vasculature or pennes' bioheat equation. J Magn Reson Imaging. 2012;35:795‐803. [DOI] [PubMed] [Google Scholar]
38. Fiedler TM, Ladd ME, Bitz AK. SAR simulations & safety. Neuroimage. 2018;168:33‐58. [DOI] [PubMed] [Google Scholar]
39. Kozlov M, Turner R. A comparison of Ansoft HFSS and CST microwave studio simulation software for multi‐channel coil design and SAR estimation at 7T MRI. Piers Online. 2010;6:395‐399. [Google Scholar]
40. Testing and Labeling Medical Devices for Safety in the Magnetic Resonance (MR) Environment: Guidance for Industry and Food and Drug Administration Staff. FDA‐2019‐D‐2837. Rockville, MD: Food and Drug Administration 2023.
41. Le Ster C, Mauconduit F, Mirkes C, et al. RF heating measurement using MR thermometry and field monitoring: methodological considerations and first in vivo results. Magn Reson Med. 2021;85:1282‐1293. [DOI] [PubMed] [Google Scholar]
42. Cabraja M, Klein M, Lehmann TN. Long‐term results following titanium cranioplasty of large skull defects. Neurosurg Focus. 2009;26:E10. [DOI] [PubMed] [Google Scholar]
43. Liang W, Xiaofeng Y, Weiguo L, et al. Cranioplasty of large cranial defect at an early stage after decompressive craniectomy performed for severe head trauma. J Craniofac Surg. 2007;18:526‐532. [DOI] [PubMed] [Google Scholar]
44. Panych LP, Madore B. The physics of MRI safety. J Magn Reson Imaging. 2018;47:28‐43. [DOI] [PubMed] [Google Scholar]
45. Fagan AJ, Bitz AK, Björkman‐Burtscher IM, et al. 7T MR safety. J Magn Reson Imaging. 2021;53:333‐346. [DOI] [PMC free article] [PubMed] [Google Scholar]
46. Stroud J, Stupic K, Walsh T, Celinski Z, Hankiewicz JH. Local heating of metallic objects from switching magnetic gradients in MRI. In: Proceedings SPIE 10954, Medical Imaging 2019: Imaging Informatics for Healthcare, Research, and Applications. Vol 10954. SPIE; 2019:150‐161. [Google Scholar]
47. Arduino A, Bottauscio O, Brühl R, Chiampi M, Zilberti L. In silico evaluation of the thermal stress induced by MRI switched gradient fields in patients with metallic hip implant. Phys Med Biol. 2019;64:245006. [DOI] [PubMed] [Google Scholar]
48. Wooldridge J, Arduino A, Zilberti L, et al. Gradient coil and radiofrequency induced heating of orthopaedic implants in MRI: influencing factors. Phys Med Biol. 2021;66:245024. [DOI] [PubMed] [Google Scholar]
49. Graf H, Steidle G, Schick F. Heating of metallic implants and instruments induced by gradient switching in a 1.5‐tesla whole‐body unit. J Magn Reson Imaging. 2007;26:1328‐1333. [DOI] [PubMed] [Google Scholar]
50. Sadeghi‐Tarakameh A, DelaBarre L, Zulkarnain NIH, Harel N, Eryaman Y. Implant‐friendly MRI of deep brain stimulation electrodes at 7 T. Magn Reson Med. 2023;90:2627‐2642. [DOI] [PMC free article] [PubMed] [Google Scholar]
51. Winter L, Oberacker E, Özerdem C, et al. On the RF heating of coronary stents at 7.0 Tesla MRI. Magn Reson Med. 2015;74:999‐1010. [DOI] [PubMed] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

Figure S1. The 4 × 4 cells titanium mesh CAD models obtained as (a) 3D scanning STL mesh model. (b) 3D volumetric CAD model. (c) 2D flat surface CAD model.

Figure S2. Positions of the temperature probes 1 mm above the titanium mesh. P1 is the control position.

Figure S4. Placement of titanium mesh model on skull inside the scalp tissue in the anatomical human simulation models. The mesh was curved to better fit the curvature of the skull.

Figure S5. Duke model with a large titanium mesh implant covering the right side of the head.

MRM-94-414-s001.docx^{(5.5MB, docx)}

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[mrm30477-bib-0050] 50. Sadeghi‐Tarakameh A, DelaBarre L, Zulkarnain NIH, Harel N, Eryaman Y. Implant‐friendly MRI of deep brain stimulation electrodes at 7 T. Magn Reson Med. 2023;90:2627‐2642. [DOI] [PMC free article] [PubMed] [Google Scholar]

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PERMALINK

On the RF safety of titanium mesh head implants in 7 T MRI systems: an investigation

Mazin Mustafa

Nur Izzati Huda Zulkarnain

Alireza Sadeghi‐Tarakameh

Andrea Grant

David Darrow

Can Ozutemiz

Yigitcan Eryaman