Safety evaluation of large external fixation clamps and frames in a magnetic resonance environment

Luechinger, Roger; Boesiger, Peter; Disegi, John A.

doi:10.1002/jbm.b.30699

Cited by 28 publications

(20 citation statements)

References 63 publications

(88 reference statements)

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“…Conversely, an accurate representation of ||E ⃗ || in the space between the coil and the load is important when evaluating safety in patients with conductive medical devices that are partially implanted or in contact with the skin [7,23]. High temperature changes in gel were reported in presence of external devices that are in contact with the skin, such as electroencephalography leads [49][50][51], electrocardiography leads [52][53][54], catheters in interventional MRI [55,56], and orthopedics external fixators [37,57]. Data presented in this paper were normalized based on the ||B ⃗ || magnitude at the isocenter of the coil.…”

Section: Discussionmentioning

confidence: 99%

Assessing the Electromagnetic Fields Generated By a Radiofrequency MRI Body Coil at 64 MHz: Defeaturing Versus Accuracy

Lucano

Liberti

Mendoza

et al. 2016

IEEE Trans. Biomed. Eng.

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Goal-This study aims at a systematic assessment of five computational models of a birdcage coil for magnetic resonance imaging (MRI) with respect to accuracy and computational cost.Methods-The models were implemented using the same geometrical model and numerical algorithm, but different driving methods (i.e., coil "defeaturing"). The defeatured models were labeled as: specific (S2), generic (G32, G16), and hybrid (H16, H16 fr-forced ). The accuracy of the models was evaluated using the "Symmetric Mean Absolute Percentage Error" ("SMAPE"), by comparison with measurements in terms of frequency response, as well as electric (||E ⃗ ||) and magnetic (||B ⃗ ||) field magnitude. HHS Public Access Author Manuscript Author ManuscriptAuthor Manuscript Author ManuscriptResults-All the models computed the ||B ⃗ || within 35 % of the measurements, only the S2, G32, and H16 were able to accurately model the ||E ⃗ || inside the phantom with a maximum SMAPE of 16 %. Outside the phantom, only the S2 showed a SMAPE lower than 11 %. Conclusions-Resultsshowed that assessing the accuracy of ||B ⃗ || based only on comparison along the central longitudinal line of the coil can be misleading. Generic or hybrid coils -when properly modeling the currents along the rings/rungs -were sufficient to accurately reproduce the fields inside a phantom while a specific model was needed to accurately model ||E ⃗ || in the space between coil and phantom.Significance-Computational modeling of birdcage body coils is extensively used in the evaluation of RF-induced heating during MRI. Experimental validation of numerical models is needed to determine if a model is an accurate representation of a physical coil.

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Section: Discussionmentioning

confidence: 99%

Assessing the Electromagnetic Fields Generated By a Radiofrequency MRI Body Coil at 64 MHz: Defeaturing Versus Accuracy

Lucano

Liberti

Mendoza

et al. 2016

IEEE Trans. Biomed. Eng.

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“…The agar was made out of the same saline solution with additional 2% agar as a gelling agent. The similar setup has been used and described in detail in other contexts [20]. The agar phantom prevents convection next to the RFID.…”

Section: Methodsmentioning

confidence: 99%

“…This is a test method that covers the measurement of the magnetically induced displacement force produced by the static magnetic field on medical devices. The main magnetic field gradient of the MR scanner used at the measurement point was 45 ± 2 mT/cm (= 4500 mT/m) [20]. It is located 3 cm away from the laser cross for patient positioning.…”

Section: Methodsmentioning

confidence: 99%

Safety and reliability of Radio Frequency Identification Devices in Magnetic Resonance Imaging and Computed Tomography

Steffen¹,

Luechinger

Wildermuth

et al. 2010

Patient Saf Surg

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BackgroundRadio Frequency Identification (RFID) devices are becoming more and more essential for patient safety in hospitals. The purpose of this study was to determine patient safety, data reliability and signal loss wearing on skin RFID devices during magnetic resonance imaging (MRI) and computed tomography (CT) scanning.MethodsSixty RFID tags of the type I-Code SLI, 13.56 MHz, ISO 18000-3.1 were tested: Thirty type 1, an RFID tag with a 76 × 45 mm aluminum-etched antenna and 30 type 2, a tag with a 31 × 14 mm copper-etched antenna. The signal loss, material movement and heat tests were performed in a 1.5 T and a 3 T MR system. For data integrity, the tags were tested additionally during CT scanning. Standardized function tests were performed with all transponders before and after all imaging studies.ResultsThere was no memory loss or data alteration in the RFID tags after MRI and CT scanning. Concerning heating (a maximum of 3.6°C) and device movement (below 1 N/kg) no relevant influence was found. Concerning signal loss (artifacts 2 - 4 mm), interpretability of MR images was impaired when superficial structures such as skin, subcutaneous tissues or tendons were assessed.ConclusionsPatients wearing RFID wristbands are safe in 1.5 T and 3 T MR scanners using normal operation mode for RF-field. The findings are specific to the RFID tags that underwent testing.

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“…IUDs were measured in a body shaped reservoir filled with 30 liters of distilled water, 300 g of polyacrylamide (PAA) and 39.6 g of NaCl, as recently described [14, 15, 16]. The conductivity of the gel was measured as 4.7±0.4 mS/cm.…”

Section: Methodsmentioning

confidence: 99%

Safety of intrauterine devices in MRI

et al. 2018

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ObjectivesThe paucity of safety information on intrauterine devices (IUD) for magnetic resonance imaging (MRI) examinations is clinically relevant. The aim of this study is to evaluate the MRI safety of clinically used IUDs composed of copper/gold and stainless steel at 1.5T and 3.0T.Materials and methodsWe assessed and compared the displacement force, torque effects, presence of imaging artifacts and heating of IUDs composed of copper/gold (western IUDs) and stainless steel (China) on 1.5 and 3.0T MRI systems.ResultsGold/Copper IUDs can show small deflection angles of 7° ± 7° in the worst-case field gradient of 40T/m (equivalent to magnetic force of 0.5 mN), while the stainless steel IUD experienced significant magnetic force and deflection (Force > 7.5 N; deflection angle 90° ± 1°). Manual rotation and suspension method show no torque effects on gold/copper IUDs but high torque effects were observed by manual rotation on the stainless steel IUD. Heating measurements showed a temperature increase (rescaled to a wbSAR of 4 W/kg) of 1.4°C at 1.5T / 3.4°C at 3.0 T (stainless steel IUD), 3.2°C at 1.5 T / 3.8°C at 3 T (copper/gold IUD), 3.3°C at 1.5 T / 4.8°C at 3 T (copper 1), 3.8°C at 1.5 T / 4.8°C at 3 T (copper 2). The visible imaging artifacts of the copper and gold IUDs at 3 T MRI reach a diameter of 4 mm ± 1 mm, while the stainless steel IUD resulted in artifacts measuring 200mm ± 10 mm when using gradient echo pulse sequences.ConclusionsStandard IUDs (copper/gold) can be considered as conditional for MR safety at 1.5 T and 3.0 T, demonstrating at wbSAR up to 4W/kg and a magnetic field gradient of up to 40T/m with minimal imaging artifacts. The stainless steel IUD, however, induces unacceptable artifacts and is potentially harmful to patients during MRI due to high magnetic dislocation forces and torque (MR unsafe).

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Safety evaluation of large external fixation clamps and frames in a magnetic resonance environment

Cited by 28 publications

References 63 publications

Assessing the Electromagnetic Fields Generated By a Radiofrequency MRI Body Coil at 64 MHz: Defeaturing Versus Accuracy

Assessing the Electromagnetic Fields Generated By a Radiofrequency MRI Body Coil at 64 MHz: Defeaturing Versus Accuracy

Safety and reliability of Radio Frequency Identification Devices in Magnetic Resonance Imaging and Computed Tomography

Safety of intrauterine devices in MRI

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