Translational Science
Science Made Simple MRI-safe robots. Why are they not yet routinely used? Kaspar Althoefer Department of Informatics, Centre for Robotics Research, King's College London, London, UK
Magnetic resonance imaging has been mooted as the best thing in minimally invasive surgery since X-ray and ultrasonography. MRI, already widely used as a diagnostic tool, impresses with a host of advantages, such as high soft tissue contrast, high image resolution, three-dimensional representation of the patient’s anatomy, accurate tumour localisation and no emission of harmful ionising radiation. If MRI appears to be the ideal diagnostic tool, why is it that MRI-safe or MRI-compatible robots make ground only very slowly in the field of MRI-guided intervention?
Fig. 1 MRI-compatible multi-segment steering mechanism for cardiac ablation [2].
Introducing robots into the MRI environment is marred with a list of problems and associated design and engineering challenges which need to be overcome: • The types of materials that can be deployed within the MRI environment and, hence, are suitable candidates for MRI-compatible robots are heavily restricted. Most of today’s robots and their constituent components, such as wiring, electronics, motors and sensors, are usually composed of ferro-magnetic materials, the presence of which in or near an MRI scanner can lead to enormous distortions in the images and, in extreme cases, can cause the robot to overheat with severe problems for the patient. • The limited space within the bore of an MRI scanner renders it difficult for a clinician to access the patient during the scan in order to perform a procedure. The same is true for most state-of-the-art robot manipulators because, structurally, they are often modelled after the human arm, as is the case for robot manipulators in the automotive manufacturing environment and the da Vinci surgical robots produced by Intuitive Surgical. • Compared with X-ray, MRI is a slow imaging technique, rendering the real-time tracking of a robot within its environment difficult. Given the above engineering challenges, what is appealing about the use of MRI-guided robots? The main advantage of using robots during MRI-guided interventions is that the clinician, guided by the image feedback provided by the MRI scanner, can steer the robot (and the attached surgical tool) to the point of interest, allowing exact targeting in three © 2014 The Author BJU International © 2014 BJU International | doi:10.1111/bju.12706 Published by John Wiley & Sons Ltd. www.bjui.org
dimensions inside the patient. Current research is aimed at developing MRI-safe robots of suitable size and structure so that they can be placed in or next to the MRI scanner bore and carry out minimally invasive procedures on the patient, as is the case for example in the fields of urology [1] and cardiac catheterisation (Fig. 1 [2]).
MRI-Safe Robots Research focuses on creating robots entirely made of non-ferrous, dielectric materials. Solutions have been proffered to meet this engineering challenge but they are still in the experimental stage. Motors can be pneumatic, hydraulic or piezoelectric [3]; sensors can use fibre optics [4,5], and the mechanical structure can be made of plastic.
Closing the Loop The ultimate goal is to create a minimally invasive robot-based surgical system that provides the clinician with an accurate and clear real-time three-dimensional visualisation of the robot within its environment, i.e. the patient’s internal anatomy. A user-friendly and possibly ergonomic input device
BJU Int 2014; 113: 975–976 wileyonlinelibrary.com
Althoefer
enables the clinician to guide the robot to the intended target, overcoming the problems associated with current hand-held devices (such as catheters used during MRI-guided cardiac ablation). Using the MRI feedback allows the clinician to intuitively control and accurately track the robot’s location with respect to the patient’s anatomy. To use MRI-safe robots effectively in medical interventions requiring real-time display, image reconstruction times must be reduced; work is being conducted to this end [6].
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Conflict of Interest The author has received research support from the Wellcome Trust/EPSRC-funded Medical Engineering Centre of Research Excellence at King’s College London, and is named on patent WO2013017875 (A2) – CONTINUUM MANIPULATOR.
References 1
976
Srimathveeravalli G, Kim C, Petrisor D et al. MRI-safe robot for targeted transrectal prostate biopsy: animal experiments. BJU Int 2014; 113: 977– 85
© 2014 The Author BJU International © 2014 BJU International
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Ataollahi A, Karim R, Soleiman Fallah A et al. 3-DOF MR-compatible multi-segment cardiac catheter steering mechanism. IEEE Transactions on Biomedical Engineering 2013; PP: 1 Macura KJ, Stoianovici D. Advancements in magnetic resonance-guided robotic interventions in the prostate. Top Magn Reson Imaging 2008; 19: 297–304. doi: 10.1097/RMR.0b013e3181aa68b8 Polygerinos P, Puangmali P, Schaeffter T et al. Novel miniature MRI-compatible fiber-optic force sensor for cardiac catheterization procedures. 2010 IEEE International Conference on Robotics and Automation (ICRA), 2010/5/3, pp. 2598–603 Polygerinos P, Ataollahi A, Schaeffter T et al. MRI-compatible intensity-modulated force sensor for cardiac catheterization procedures. IEEE Transactions on Biomedical Engineering 2011; 58: 721–6 Sorensen TS; Atkinson D; Schaeffter T; Hansen MS. Real-time reconstruction of sensitivity encoded radial magnetic resonance imaging using a graphics processing unit. In: IEEE Transactions on Medical Imaging 5170053, 12.2009, 28 (12), pp. 1974–85
Correspondence: Kaspar Althoefer, Department of Informatics, Centre for Robotics Research, King’s College London, The Strand, London WC2R 2LS, UK. e-mail: [email protected]
Science Made Simple MRI-safe robots. Why are they not yet routinely used? Kaspar Althoefer Department of Informatics, Centre for Robotics Research, King's College London, London, UK
Magnetic resonance imaging has been mooted as the best thing in minimally invasive surgery since X-ray and ultrasonography. MRI, already widely used as a diagnostic tool, impresses with a host of advantages, such as high soft tissue contrast, high image resolution, three-dimensional representation of the patient’s anatomy, accurate tumour localisation and no emission of harmful ionising radiation. If MRI appears to be the ideal diagnostic tool, why is it that MRI-safe or MRI-compatible robots make ground only very slowly in the field of MRI-guided intervention?
Fig. 1 MRI-compatible multi-segment steering mechanism for cardiac ablation [2].
Introducing robots into the MRI environment is marred with a list of problems and associated design and engineering challenges which need to be overcome: • The types of materials that can be deployed within the MRI environment and, hence, are suitable candidates for MRI-compatible robots are heavily restricted. Most of today’s robots and their constituent components, such as wiring, electronics, motors and sensors, are usually composed of ferro-magnetic materials, the presence of which in or near an MRI scanner can lead to enormous distortions in the images and, in extreme cases, can cause the robot to overheat with severe problems for the patient. • The limited space within the bore of an MRI scanner renders it difficult for a clinician to access the patient during the scan in order to perform a procedure. The same is true for most state-of-the-art robot manipulators because, structurally, they are often modelled after the human arm, as is the case for robot manipulators in the automotive manufacturing environment and the da Vinci surgical robots produced by Intuitive Surgical. • Compared with X-ray, MRI is a slow imaging technique, rendering the real-time tracking of a robot within its environment difficult. Given the above engineering challenges, what is appealing about the use of MRI-guided robots? The main advantage of using robots during MRI-guided interventions is that the clinician, guided by the image feedback provided by the MRI scanner, can steer the robot (and the attached surgical tool) to the point of interest, allowing exact targeting in three © 2014 The Author BJU International © 2014 BJU International | doi:10.1111/bju.12706 Published by John Wiley & Sons Ltd. www.bjui.org
dimensions inside the patient. Current research is aimed at developing MRI-safe robots of suitable size and structure so that they can be placed in or next to the MRI scanner bore and carry out minimally invasive procedures on the patient, as is the case for example in the fields of urology [1] and cardiac catheterisation (Fig. 1 [2]).
MRI-Safe Robots Research focuses on creating robots entirely made of non-ferrous, dielectric materials. Solutions have been proffered to meet this engineering challenge but they are still in the experimental stage. Motors can be pneumatic, hydraulic or piezoelectric [3]; sensors can use fibre optics [4,5], and the mechanical structure can be made of plastic.
Closing the Loop The ultimate goal is to create a minimally invasive robot-based surgical system that provides the clinician with an accurate and clear real-time three-dimensional visualisation of the robot within its environment, i.e. the patient’s internal anatomy. A user-friendly and possibly ergonomic input device
BJU Int 2014; 113: 975–976 wileyonlinelibrary.com
Althoefer
enables the clinician to guide the robot to the intended target, overcoming the problems associated with current hand-held devices (such as catheters used during MRI-guided cardiac ablation). Using the MRI feedback allows the clinician to intuitively control and accurately track the robot’s location with respect to the patient’s anatomy. To use MRI-safe robots effectively in medical interventions requiring real-time display, image reconstruction times must be reduced; work is being conducted to this end [6].
2
3
4
5
Conflict of Interest The author has received research support from the Wellcome Trust/EPSRC-funded Medical Engineering Centre of Research Excellence at King’s College London, and is named on patent WO2013017875 (A2) – CONTINUUM MANIPULATOR.
References 1
976
Srimathveeravalli G, Kim C, Petrisor D et al. MRI-safe robot for targeted transrectal prostate biopsy: animal experiments. BJU Int 2014; 113: 977– 85
© 2014 The Author BJU International © 2014 BJU International
6
Ataollahi A, Karim R, Soleiman Fallah A et al. 3-DOF MR-compatible multi-segment cardiac catheter steering mechanism. IEEE Transactions on Biomedical Engineering 2013; PP: 1 Macura KJ, Stoianovici D. Advancements in magnetic resonance-guided robotic interventions in the prostate. Top Magn Reson Imaging 2008; 19: 297–304. doi: 10.1097/RMR.0b013e3181aa68b8 Polygerinos P, Puangmali P, Schaeffter T et al. Novel miniature MRI-compatible fiber-optic force sensor for cardiac catheterization procedures. 2010 IEEE International Conference on Robotics and Automation (ICRA), 2010/5/3, pp. 2598–603 Polygerinos P, Ataollahi A, Schaeffter T et al. MRI-compatible intensity-modulated force sensor for cardiac catheterization procedures. IEEE Transactions on Biomedical Engineering 2011; 58: 721–6 Sorensen TS; Atkinson D; Schaeffter T; Hansen MS. Real-time reconstruction of sensitivity encoded radial magnetic resonance imaging using a graphics processing unit. In: IEEE Transactions on Medical Imaging 5170053, 12.2009, 28 (12), pp. 1974–85
Correspondence: Kaspar Althoefer, Department of Informatics, Centre for Robotics Research, King’s College London, The Strand, London WC2R 2LS, UK. e-mail: [email protected]
