at rest; (b) during excitation; (c) and t...Figure 4.12 Linearizing of the SD curve in terms of ΔB. The exponential form...Figure 4.13 Fitted exponential and hyperbolic SD curves to real data from to...Figure 4.14 Increasing the stimulus strength above the threshold to a supram...Figure 4.15 Waveform dependence: bi‐phasic or bipolar stimuli display lower ...Figure 4.16 Stimulation a very high frequencies (very short period stimuli):...Figure 4.17 A combined SD curve for ΔB using published PNS data for MRI (Tab...Figure 4.18 Population response for PNS from MRI gradients for three levels ...Figure 4.19 Gradient specification formulation of the SD curve showing areas...Figure 4.20 Combined for all gradients dB/dt from different sequences: BOLD ...Figure 4.21 Effective stimulus durations (ts,eff) defined in IEC‐60601‐2‐33 ...Figure 4.22 IEC limits for peripheral nerve and cardiac stimulation [34].Figure 4.23 Bio‐effects spectrum showing the principal sensory effects and f...5 Chapter 5Figure 5.1 Relative energies: 128 MHz RF photon 8.48×10−26J; 100 kVp d...Figure 5.2 Tissue conductivity (solid lines) and relative permittivity (dash...Figure 5.3 SAR hotspot formation due to electrical properties for idealised ...Figure 5.4 Human body models in a 1.5 T whole‐body RF coil (shaded region): ...Figure 5.5 Temperature increase versus time for various tissues exposed to a...Figure 5.6 Nett power absorption differences with age: the red bars indicate...Figure 5.7 Effect of ambient temperature on radiative cooling rates.Figure 5.8 Temperature regulation. TNZ is temperature neutral zone. Below LC...Figure 5.9 CEM43: (a) Cumulative equivalent minutes at 43 °C for damage to v...Figure 5.10 Skin anatomy.Figure 5.11 RF burns: (a) from inappropriate ECG electrodes.Figure 5.12 RF conduction paths. Crossing legs at ankle level increases the ...Figure 5.13 SAR derating for the First Level Controlled Mode for ambient tem...Figure 5.14 SAR reduction: flip angle and RF pulse type. Changing the RF pul...Figure 5.15 SAR reduction: the relative reduction in SAR (with respect to TR...Figure 5.16 Hyperechoes use a train of small flip angle pulses with variable...
6 Chapter 6Figure 6.1 Forces on gradient coils. (a) a Maxwell pair Gz coil; the ‘rearwa...Figure 6.2 SPL in pascals (linear scale) and dB (logarithmic scale) showing ...Figure 6.3 A, C and Z weightings.Figure 6.4 Equal loudness curves for different levels of noise (red lines), ...Figure 6.5 (a) 125 Hz trapezoidal waveform and (b) its frequency spectrum.Figure 6.6 Internal ear anatomy.Figure 6.7 Example of audiometric determination of threshold shifts showing ...Figure 6.8 Increase in hearing threshold for MRI factory workers who have un...Figure 6.9 Field dependence of SPL using gradient echo sequences.Figure 6.10 Sequence and field dependence of acoustic noise.Figure 6.11 Audio frequency spectra for various sequences. dB values are rel...Figure 6.12 Transfer function measurement with a trapezoid pulse.Figure 6.13 The influence of parameter changes on acoustic noise (a) FOV (b)...
7 Chapter 7Figure 7.1 Incidence of adverse events from first trimester MRI during pregn...Figure 7.2 Neonatal cochlear function after MRI exposures assessed by oto‐ac...Figure 7.3 Fetal SAR predictions: top row 64 MHz maternal (L), fetal (R); bo...
8 Chapter 8Figure 8.1 T1‐weighted brain pre‐ (L) and post (R) contrast showing enhancem...Figure 8.2 Structure of gadolinium‐based contrast agents (a) linear non‐ioni...Figure 8.3 Typical clearance for a patient with normal renal function and lo...Figure 8.4 Incidence of allergic reactions.Figure 8.5 Incidence of unconfounded cases of NSF.Figure 8.6 Skin thickening and ‘orange peel; appearance in a patient with NS...Figure 8.7 Gd retention in rats for (a) femur; (b) liver; (c) skin.
9 Chapter 9Figure 9.1 Signage on the MRI examination room prohibiting entry for persons...Figure 9.2 Magnitude of magnetic susceptibility for implant materials. Note ...Figure 9.3 Ratio of the maximum magnetic translational force to gravitationa...Figure 9.4 Ratio of the magnetic translational force to gravitational force ...Figure 9.5 Typical and maximum values of dB/dt arising in MRI from movement ...Figure 9.6 Estimated theoretical heating of metal spheres of radius 1 cm emb...Figure 9.7 Equilibrium maximum temperature of 1 cm radius metal spheres expo...Figure 9.8 Maximum theoretical temperatures from a simplistic model of the h...Figure 9.9 Estimated RF heating of objects made from various metals in the A...Figure 9.10 Computation of local SAR from bilateral Co‐Cr‐Mo hip implants at...Figure 9.11 ASTM 2052 deflection test [10]. The device is centred at the tes...Figure 9.12 Calculated deflection angles for spheres composed of different i...Figure 9.13 The deflection angles for spheres of various materials of equal ...Figure 9.14 The ‘suspension test’ from ASTM‐F2213 for magnetic torque [18]. ...Figure 9.15 ASTM RF heating phantom as specified in ASTM F218 [19]. The ‘hea...Figure 9.16 Examples of aneurysm clips (top, Codman Slim‐Line Aneurysm Clip,...Figure 9.17 Power loss (equivalent to SAR) around external fixation device p...Figure 9.18 Maximum temperature increase around the external fixation device...Figure 9.19 X‐ray of patient with spinal rods.Figure 9.20 The magnetic susceptibility of the object distorts the B0 field ...Figure 9.21 (a) Titanium and Co‐Cr‐Mo hip implants and corresponding gradien...Figure 9.22 MR artefacts from bilateral MR conditional Co‐Cr‐Mo hip implants...Figure 9.23 Artefact from a ferromagnetic object in the eye.Figure 9.24 Key MRI safety‐related properties for metals used in implants. A...
10 Chapter 10Figure 10.1 AIMD interactions in the MR scanner.Figure 10.2 Reed switches: (a) reed contacts; (b) directional behaviour in BFigure 10.3 Capped, uncapped, and terminated PM leads and tip heating.Figure 10.4 Pacemaker lead tip heating (charts) and peak local SAR (labels) ...Figure 10.5 Cardiac devices: (a) Pacemaker components; (b) dual lead pacemak...Figure 10.6 Lead placement: (a) dual chamber pacemaker; (b) ICD.Figure 10.7 Sensing and under‐sensing of the ECG waveform.Figure 10.8 Over‐sensing in demand mode during MRI due to the reed switch be...Figure 10.9 Strength‐duration curve for pacing.Figure 10.10 Lead maturation: (a) change in capture (pacing) threshold over ...Figure 10.11 Patient pacemaker and abandoned lead.Figure 10.12 Neurostimulators: (a) Deep brain stimulator system; (b) DBS and...Figure 10.13 Lead/electrode configurations for DBS stimulators.Figure 10.14 Cochlear implant external placement.
11 Chapter 11Figure 11.1 Examples of typical locations of maximum spatial gradient dB/dz ...Figure 11.2 Concentric cylindrical representation of the spatial gradient dB...Figure 11.3 (a) Maximum spatial gradients occurring within concentric cylind...Figure 11.4 (a) Side view of dB/dz spatial gradient contour map as depicted ...Figure 11.5 (a) Side view of dB/dz spatial gradient contour map as depicted ...Figure 11.6 B0 contour map for a Siemens Skyra 3 T scanner: side view only....Figure 11.7 B.dB/dz product contour map for a Siemens Skyra 3 T scanner: sid...Figure 11.8 Geometry of an external fixation device. B1 is into the page, in...
12 Chapter 12Figure 12.1 ACR Zoning system for a small MR suite.Figure 12.2 Controlled Access Area and MR Environment as for UK guidance [8]...Figure 12.3 Fringe field contours for a 1.5T MRI installation: (a) top view;...Figure 12.4 Confirming the fringe field: (a) Handheld 3‐axis magnetometer TM...Figure 12.5 Quench pipe outlet.Figure 12.6 Signage: (a) suitable for the magnet room door/ entrance to Zone...Figure 12.7 Ferromagnetic detection systems: (a) Ferroguard Assure mounted b...Figure 12.8 MRI suite design process.Figure 12.9 MRI‐Linac: (a) MRI‐linac gantry surrounding the MRI scanner duri...
13 Chapter 13Figure 13.1 ICNIRP Basic Restrictions for movement within the static magneti...Figure 13.2 Basic Restrictions 0.1 Hz to 100 kHz: ICNIRP [7], IEEE [9], ARPA...Figure 13.3 Reference Levels 0.1 Hz to 100 kHz: ICNIRP [7], IEEE [9], and AR...Figure 13.4 Peak occupational B field exposures. Data from [23,24]. The abso...Figure 13.5 Peak B and dB/dt exposures by occupation. Data from [25].Figure 13.6 Time‐weighted average (over a shift) B‐field exposure by occupat...Figure 13.7 Occupational field exposures (peak values) versus frequency rela...
14 Chapter 14Figure 14.1 The inter‐relationship between roles in a MR safety framework.Figure 14.2 Example patient questionnaire. Advisory document only.Figure 14.3 Detection of cardiac implants by a Metrasens ferromagnetic detec...Figure 14.4 An incident involving a ferromagnetic object, but without injury...
15 Appendix 1Figure A1.1 Magnetization of a ferromagnetic object in an external B0.
16 Appendix 2Figure A2.1 Coordinate systems showing the positional vector r and its compo...Figure A2.2 Integration
