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Table 2 Data for calculation of the power density P V of an active implant referring to Eq. 1 for an MRI sequence with an SAR of 4 W/kg (manufacturer declaration)

From: Finite volume analysis of temperature effects induced by active MRI implants: 2. Defects on active MRI implants causing hot spots

permeability of vacuum

μ0

[V s/(A m)]

12.6E-7

magnitude of magnetic excitation field

B1

[μT]

25

repetition time of MRI sequence

TR

[s]

2.23

duration of one excitation

Ï„

[ms]

0.80

number of identical excitations during TR

N

 

246

duty cycle cdc N Ï„/TR

cdc

 

0.09

pulse waveform modulation factor cpwm

cpwm

 

0.45

Larmor frequency = resonance frequency of LC circuit

ν0

[MHz]

63.8

ω0 = 2π ν0

ω0

rad/s

4.0 108

power loss density PV = P/(Q Vind) (Eq. 1)

PV

[mW/(cm3Q)]

4.0