SAFETY OR EFFICACY; CAN OR SHOULD WE HAVE BOTH? TABOO DEVICES IN THE MRI ENVIRONMENT

SUMMARYThis paper reports on recent progress made toward the development of a new magnetic resonance imaging (MRI)-compatible robot-assisted surgical system for closed-bore image-guided prostatic interventions: thermal ablation, radioactive seed implants (brachytherapy), and biopsy. Each type of intervention will be performed with a different image-guided, robot-based surgical tool mounted on the same MRI-guided robot through a modular trocar. The first stage of this development addresses only laser-based focal ablation. The robot mechanical structure, modular surgical trocar, control architecture, and current stage of performance evaluation in the MRI environment are presented. The robot actuators are ultrasonic motors. A methodology of using such motors in the MRI environment is presented. The robot prototype with surgical ablation tool is undergoing tests on phantoms in the MRI bore. The tests cover MRI compatibility, image visualization, robot accuracy, and thermal mapping. To date, (i) the images are artifact- and noise-free for certain scanning pulse sequences; (ii) the robot tip positioning error is less than 1.2 mm even at positions closer than 0.3 m from the MRI isocenter; (iii) penetration toward the target is image-monitored in near-real time; and (iv) thermal ablation and temperature mapping are achieved using a laser delivered on an optical fiber and MRI, respectively.

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Large-scale functional integration, rather than functional dissociation along dorsal and ventral streams, underlies visual perception and action

10.1101/609487 ◽

2019 ◽

Author(s):

Dipanjan Ray ◽

Nilambari Hajare ◽

Dipanjan Roy ◽

Arpan Banerjee

Keyword(s):

Visual Perception ◽

Large Scale ◽

Premotor Cortex ◽

Functional Integration ◽

Predictive Coding ◽

Dorsal Stream ◽

Brain Regions ◽

Neural Pathways ◽

Healthy Human ◽

Mri Environment

AbstractVisual dual stream theory posits that two distinct neural pathways of specific functional significance originate from primary visual areas and reach the inferior temporal (ventral) and posterior parietal areas (dorsal). However, there are several unresolved questions concerning the fundamental aspects of this theory. For example, is the functional dissociation between ventral and dorsal stream driven by features in input stimuli or is it driven by categorical differences between visuo-perceptual and visuo-motor functions? Is the dual stream rigid or flexible? What is the nature of the interactions between two streams? We addressed these questions using fMRI recordings on healthy human volunteers and employing stimuli and tasks that can tease out the divergence between visuo-perceptual and visuo-motor models of dual stream theory. fMRI scans were repeated after seven practice sessions that were conducted in a non-MRI environment to investigate the effects of neuroplasticity. Brain activation analysis supports an input-based functional dissociation and existence of context-dependent neuroplasticity in dual stream areas. Intriguingly, premotor cortex activation was observed in the position perception task and distributed deactivated regions were observed in all perception tasks thus, warranting a network level analysis. Dynamic causal modelling (DCM) analysis incorporating activated and deactivated brain areas during perception tasks indicates that the brain dynamics during visual perception and actions could be interpreted within the framework of predictive coding. Effectively, the network level findings point towards the existence of more intricate context-driven functional networks selective of “what” and “where” information rather than segregated streams of processing along ventral and dorsal brain regions.

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Kinematics analysis and trajectory planning for a breast intervention robot under MRI environment

2017 IEEE International Conference on Cyborg and Bionic Systems (CBS) ◽

10.1109/cbs.2017.8266106 ◽

2017 ◽

Cited By ~ 1

Author(s):

Yongde Zhang ◽

Mingyue Lu ◽

Haiyan Du

Keyword(s):

Trajectory Planning ◽

Kinematics Analysis ◽

Mri Environment

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Dynamic Forcing of End-Tidal Carbon Dioxide and Oxygen Applied to Functional Magnetic Resonance Imaging

Journal of Cerebral Blood Flow & Metabolism ◽

10.1038/sj.jcbfm.9600465 ◽

2007 ◽

Vol 27 (8) ◽

pp. 1521-1532 ◽

Cited By ~ 89

Author(s):

Richard G Wise ◽

Kyle TS Pattinson ◽

Daniel P Bulte ◽

Peter A Chiarelli ◽

Stephen D Mayhew ◽

...

Keyword(s):

Carbon Dioxide ◽

Blood Oxygenation ◽

Dynamic Responses ◽

Bold Signal ◽

Tidal Forcing ◽

Partial Pressures ◽

Oxygenation Level ◽

Mri Environment ◽

Dynamic Forcing ◽

End Tidal

Investigations into the blood oxygenation level-dependent (BOLD) functional MRI signal have used respiratory challenges with the aim of probing cerebrovascular physiology. Such challenges have altered the inspired partial pressures of either carbon dioxide or oxygen, typically to a fixed and constant level (fixed inspired challenge (FIC)). The resulting end-tidal gas partial pressures then depend on the subject's metabolism and ventilatory responses. In contrast, dynamic end-tidal forcing (DEF) rapidly and independently sets end-tidal oxygen and carbon dioxide to desired levels by altering the inspired gas partial pressures on a breath-by-breath basis using computer-controlled feedback. This study implements DEF in the MRI environment to map BOLD signal reactivity to CO2. We performed BOLD (T2*) contrast FMRI in four healthy male volunteers, while using DEF to provide a cyclic normocapnichypercapnic challenge, with each cycle lasting 4 mins (PetCO2 mean±s.d., from 40.9 ± 1.8 to 46.4 ± 1.6 mm Hg). This was compared with a traditional fixed-inspired (FiCO2 = 5%) hypercapnic challenge (PetCO2 mean±s.d., from 38.2 ± 2.1 to 45.6 ± 1.4 mm Hg). Dynamic end-tidal forcing achieved the desired target PetCO2 for each subject while maintaining PetCO2 constant. As a result of CO2-induced increases in ventilation, the FIC showed a greater cyclic fluctuation in PetCO2. These were associated with spatially widespread fluctuations in BOLD signal that were eliminated largely by the control of PetCO2 during DEF. The DEF system can provide flexible, convenient, and physiologically well-controlled respiratory challenges in the MRI environment for mapping dynamic responses of the cerebrovasculature.

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