Magnetic Resonance Imaging Room Research Articles

Innovative Design and Experimental Research of the Patient Transfer Apparatus for MRI Room

Background: Patient Transfer Apparatus (PTA), which has been reported by various relevant papers and patents, is widely used in the hospital. However, there are few corresponding transfer apparatuses for research and development in the nuclear magnetic resonance imaging (MRI) room because of the influence of a high magnetic field environment. It is desired to require the apparatus for the patient and the medical staff to have weak magnetism, high matching, and easy operation, etc. Objective: The purpose of this study is to find out the working principle of PTA, to conduct parameter optimization and design and develop more effective PTA for the application of the MRI room. Methods: Firstly, based on the patient transfer process, a novel transfer model with the coordinated movement of the transfer belt and the moving panel is proposed, the corresponding clutch mechanism is conceived and the working principle of the whole mechanism movement is designed and analyzed in detail. Secondly, the force analysis of the clutch mechanism, lifting mechanism and patient transfer mechanism are performed, the mechanical structures are optimized, and the optimal sizes are obtained. Thirdly, the mechanical structure of the system is designed in detail, and the prototype is manufactured. Results: Finally, the performance evaluation of the system is conducted by means of the fuzzy evaluation method and clinical study. The results showed that the motion function of the apparatus is reasonable and it can work normally in the MRI room, the comfort of the PTA is also excellent. The research results also prove the accuracy of the working principle and the rationality of the structural design. Conclusion: The non-magnetic PTA is suitable for quickly transferring patients who are unable to move in the MRI room of a hospital by the manual method.

Optimized, Person-Centered Workflow Design for a High-Throughput Breast MRI Screening Facility-A Simulation Study.

This project aims to model an optimal scanning environment for breast magnetic resonance imaging (MRI) screening based on real-life data to identify to what extent the logistics of breast MRI can be optimized. A novel concept for a breast MRI screening facility was developed considering layout of the building, workflow steps, used resources, and MRI protocols. The envisioned screening facility is person centered and aims for an efficient workflow-oriented design. Real-life data, collected from existing breast MRI screening workflows, during 62 scans in 3 different hospitals, were imported into a 3D simulation software for designing and testing new concepts. The model provided several realistic, virtual, logistical pathways for MRI screening and their outcome measures: throughput, waiting times, and other relevant variables. The total average appointment time in the baseline scenario was 25:54 minutes, with 19:06 minutes of MRI room occupation. Simulated improvements consisted of optimizing processes and resources, facility layout, and scanning protocol. In the simulation, time spent in the MRI room was reduced by introducing an optimized facility layout, dockable tables, and adoption of an abbreviated MRI scanning protocol. The total average appointment time was reduced to 19:36 minutes, and in this scenario, the MRI room was occupied for 06:21 minutes. In the most promising scenario, screening of about 68 people per day (10 hours) on a single MRI scanner could be feasible, compared with 36 people per day in the baseline scenario. This study suggests that by optimizing workflow MRI for breast screening total appointment duration and MRI occupation can be reduced. A throughput of up to 6 people per hour may be achieved, compared with 3 people per hour in the current setup.

Child-centredness in paediatric magnetic resonance imaging: Information needs and experiences of children requiring magnetic resonance imaging and their parents.

Assessing patient experiences is essential to provide high quality health-care. The objectives of this study were to examine (1) child- and parent-reported information status before magnetic resonance imaging (MRI), (2) experiences during an MRI and (3) needs and suggestions for improvement. Children (≥8 years) and parents answered questionnaires (before and after planned MRI examination) covering mental condition, information status/needs, preparation for MRI, and potential stressors. Before MRI n = 132 accompanying parents and n = 91 children provided data (after MRI: n = 93 parents; n = 71 children). The mean age of the children undergoing MRI was 10.5 years (SD = 4.9). Children had on average seven previous MRIs before our survey (Range: 1-33). Twenty-three percent of the children were to be sedated during the examination. Parents and children reported low to medium levels of burden, high knowledge and high information status. For the children, most stressful factors during the MRI were boredom and noise. Main information resources were the radiologists or self-searches. Parents of children with their first MRI reported higher anxiety levels in their children and stated a worse information status (main information source: self-searches/internet). Parents reported needs regarding organization of the MRI (e.g., reduction of waiting times), age-appropriate information and communication during the MRI. Children wished to visit the MRI room prior the examination (44%) and to get more information (44%). Children suggested improvements such as better sound quality of films/music, more transparency about the procedure, being in contact with a parent and shorter examinations. Results suggest that preparation, information provision and care is perceived positively by families. Needs and suggestions for improvement were, for example, higher transparency of procedures, better communication and reduction of stress. Findings indicate that preparation in routine-care should follow an individualized child-focused approach, should focus on families without previous MRIs and should address children with high anxiety levels.

Robotic system for magnetic resonance imaging-guided high-intensity focus ultrasound application: Feasibility of breast fibroadenoma treatment.

This paper presents a high-intensity focus ultrasound (HIFU) robotic system for treating breast fibroadenoma under the guidance of magnetic resonance imaging (MRI). Based on the thermal and mechanical effects of ultrasound, the system aims to deliver ultrasound energy to a target precisely without damaging the normal tissue. The temperature elevation can be monitored in real time by MRI, and the treatment plan can be adjusted during the procedure. The requirements, design specifications, control system and registration of the robotic system are specified. The robotic system was designed with a 3 degrees of freedom manipulator with limit switches and encoders, a customised MRI-compatible breast coil, a water bladder with sets of breast-conforming brackets, and a probe capable of generating ultrasound. Twenty volunteers were recruited for this study, and their data were analysed to provide more precise data for the design. The accuracy of the robot was evaluated in free space using a coordinate measuring machine, phantom and ex vivo porcine tissue in MRI room. The study also verified the signal-to-noise ratio (SNR) of the MRI with the effect of the robotic system. The research findings revealed that the manipulator exhibited a translational precision of 0.10±0.14mm, a rotational fidelity around the X direction of 0.11±0.09°, and an oscillatory exactness around the Y direction of 0.10±0.08°. The investigation of positioning accuracy demonstrated that the robot's error in free space was 0.26±0.07mm. When subjected to MRI room with agar-silica phantom and ex vivo porcine tissue, the positioning accuracy amounted to 1.11±0.47mm and 1.57±0.52mm. In the presence of the robotic system, the SNR of the MRI experienced a 4.2% reduction, which had a negligible impact on image quality. The conducted experiments validate the efficacy of the proposed MRI-guided HIFU robotic system in executing agar-silica phantom and ex vivo porcine tissue investigations with adequate positioning accuracy. Consequently, this system exhibits certain feasibility for the treatment of breast fibroadenomas.

The Infection Control Measures Taken in MRI Examination During the COVID-19 Pandemic Prevention and Control Period

Objective: To optimize the magnetic resonance imaging (MRI) detection process in view of the COVID-19 pandemic, standardize and strengthen the infection control and management MRI rooms. Methods: According to the Technical Guide for COVID-19 Prevention and Control in Medical Institutions (3rd Edition), with reference to the current COVID-19 infection control plan, there are three aspects involved in the planning of MRI examination: MRI room management, medical staff management and protection, and patient management, especially the use of full plastic nose strip medical masks. Infection prevention measures are formulated, scientific prevention and control are made, and accurate policies are implemented. Results: MRI examination was carried out according to the infection control and management of MRI room plan during the epidemic, so as to ensure the safety of examination, the safety of patients and the safety of medical staff and no cross infection in hospital. Conclusion: The implementation of proper infection prevention measures during MRI examination in light of COVID-19 ensures that patients wear medical surgical masks with full plastic nose strips throughout the process to avoid cross-infection, ensure the safety of doctors and patients, and maintain the health of the population.

Medical Accidents Related to Ferromagnetic Objects Brought into the MRI Room: Analysis of the National Multicenter Database by Orthopedic Surgeons.

Magnetic resonance imaging (MRI) is widely used in orthopedics, but orthopedic surgeons, including spine surgeons, do not have detailed knowledge of MRI-related accidents. We, as orthopedic surgeons, investigated the details of medical accidents related to ferromagnetic objects brought into the MRI room using a national multicenter database. We conducted an exploratory analysis of accidents involving MRI ferromagnets based on the Japanese database of adverse medical occurrences. From a total of 104,659 accident reports over nine years, 172 involving the presence of ferromagnetic objects in the MRI room were extracted and analyzed. The accident reports frequently involved children and the elderly. Nurses filed the highest number of reports (44.8%) by occupation, which was more than twice as many as physicians (19.8%). The most common ferromagnetic devices brought into the MRI rooms were pacemakers (n = 22). There were also large magnetic objects such as oxygen cylinders (n = 12) and IV stands (n = 7). In the field of orthopedics, ankle weights (n = 4), pedometers (n = 3), and artificial limbs (n = 2) were brought in. "Failure to check" was the most common cause of accidents (69%). Actual harm to patients occurred in 9% of cases, with no fatalities. Manuals and checklists should be developed and continuous education provided to prevent accidents involving magnetic objects brought into the MR scanner room. As orthopedic surgeons, including spine surgeons, we should be cautious with emergency, geriatric, and pediatric patients because their information and medical history may not be accurate. We should not overlook equipment commonly found in orthopedic practice such as ankle weights and pedometers.

Mutual interferences between SIAT aPET insert and a 3 T uMR 790 MRI scanner

Objective. Dual-modality small animal PET/MR imaging provides temporally correlated information on two biochemical processes of a living object. An magnetic resonance imaging (MRI)-compatible small animal PET insert named Shenzhen Institutes of Advanced Technology (SIAT) aPET was developed by using dual-ended readout depth encoding detectors to simultaneously achieve a uniform high spatial resolution and high sensitivity at the SIAT. In this work, the mutual interferences between SIAT aPET and the 3 T uMR 790 MRI scanner of United Imaging was quantitatively evaluated. Approach. To minimize the mutual interferences, only the PET detectors and the readout electronics were placed inside the MRI scanner, the major signal processing electronic was placed in the corner of the MRI room and the auxiliary unit was placed in the MRI technical room. A dedicated mouse radio fRequency (RF) coil with a transmitter and receiver was developed for the PET insert. The effects of PET scanner on the B 0 and B 1 field of the MRI scanner and the quality of the MRI images were measured. The effects of MRI imaging on the performance of both the PET detectors and scanner were also measured. Main results. The electronic and mechanical components of the PET insert affected the homogeneity of the B 0 field. The PET insert had no effect on the homogeneity of B 1 produced by the dedicated mouse coil but slightly reduced the strength of B 1. The mean and standard deviation of the RF noise map were increased by 2.2% and 11.6%, respectively, while the PET insert was placed in the MRI scanner and powered on. Eddy current was produced while the PET insert was placed in the MRI scanner, and it was further increased while the PET insert was powered on. Despite the above-mentioned interferences from the PET insert, the MR images of a uniform cylindrical water phantom showed that the changes in the signal-to-noise ratio (SNR) and homogeneity as the PET insert was placed in the MRI scanner were acceptable regardless of whether the PET insert was powered off or powered on. The maximum reduction of SNR was less than 11%, and the maximum reduction of homogeneity was less than 2.5% while the PET insert was placed inside the MRI scanner and powered on for five commonly used MRI sequences. MRI using gradient echo (GRE), spin echo (SE) and fast spin echo (FSE) sequences had negligible effects on the flood histograms and energy resolution of the PET detectors, as well as the spatial resolution and sensitivity of the PET scanner. Significance. The mutual interference between the SIAT aPET and the 3 T uMR 790 MRI scanner are acceptable. Simultaneous PET/MRI imaging of small animals can be performed with the two scanners.

Design of a Patient-Specific Respiratory-Motion-Simulating Platform for In Vitro 4D Flow MRI.

Four-dimensional (4D) flow magnetic resonance imaging (MRI) is a leading-edge imaging technique and has numerous medicinal applications. In vitro 4D flow MRI can offer some advantages over in vivo ones, especially in accurately controlling flow rate (gold standard), removing patient and user-specific variations, and minimizing animal testing. Here, a complete testing method and a respiratory-motion-simulating platform are proposed for in vitro validation of 4D flow MRI. A silicon phantom based on the hepatic arteries of a living pig is made. Under the free-breathing, a human volunteer's liver motion (inferior-superior direction) is tracked using a pencil-beam MRI navigator and is extracted and converted into velocity-distance pairs to program the respiratory-motion-simulating platform. With the magnitude displacement of about 1.3cm, the difference between the motions obtained from the volunteer and our platform is ≤ 1mm which is within the positioning error of the MRI navigator. The influence of the platform on the MRI signal-to-noise ratio can be eliminated even if the actuator is placed in the MRI room. The 4D flow measurement errors are respectively 0.4% (stationary phantom), 9.4% (gating window = 3mm), 27.3% (gating window = 4mm) and 33.1% (gating window = 7mm). The vessel resolutions decreased with the increase of the gating window. The low-cost simulation system, assembled from commercially available components, is easy to be duplicated.

Mobile Technology in Medicine: Development and Validation of an Adapted System Usability Scale (SUS) Questionnaire and Modified Technology Acceptance Model (TAM) to Evaluate User Experience and Acceptability of a Mobile Application in MRI Safety Screening.

Background Magnetic resonance imaging (MRI) safety screening is a crucial procedure for patient preparation before entering into MRI room. Many hospitals in Malaysia are still using the MRI safety checklist printed form. Besides, clinicians will not get a definite conclusion about whether the patient is contraindicated for MRI or not. Hence, we have created one mobile application named MagnetoSafe to overcome this issue. The application will provide an instant decision on whether the patient has no contraindication, relative contraindication, or absolute contraindicated for MRI. We need to check for acceptability and user experience for any newly created mobile application. Objective This study was designed to check the validity of the adapted Technology Acceptance Model (TAM) and System Usability Scale (SUS) Questionnaire. Method The validity and reliability of the questionnaire were investigated. Subsequently, 52 fully completed responses were collected. Results Face and content validity of the questionnaires are considered acceptable with only minor changes to Item 10 of SUS. The Cronbach's alpha for the SUS questionnaire (10 questions) is -0.49, which is not acceptable. The Cronbach's alpha for TAM questionnaire (3 domains; 14 questions) is acceptable, which is 0.910 for perceived usefulness, 0.843 for perceived ease of use, and 0.915 for intention to use. Conclusion Face validity of the adapted SUS and modified TAM questionnaires is acceptable with only minor changes to Item 10 in SUS. Content validity with experts is good. However, the reliability of the SUS questionnaire is not acceptable and therefore adapted SUS will not be used for assessing user experience. The reliability of the modified TAM questionnaire with the original three-factor structure is considered acceptable and can be used to evaluate the user's acceptability of MagnetoSafe.

Effect of Hot Water Bottles on Body Temperature during Magnetic Resonance Imaging in Dogs under General Anesthesia: A Retrospective Study.

Prevention of hypothermia induced by anesthesia and enhanced by low environmental temperatures is difficult in magnetic resonance imaging (MRI) examinations in dogs as forced warming devices, including magnetic materials, are not acceptable for use in the MRI room. A hot water bottle (HWB) can be carried into an MRI examination room and can contribute to the prevention or attenuation of hypothermia. Here, we retrospectively investigated the effects of HWB on body temperature during MRI examinations in dogs under general anesthesia (GA). From anesthesia records of the Veterinary Medical Teaching Hospital, Okayama University of Science, validated data of 100 dogs that underwent an MRI examination under GA were obtained and divided into the following two groups: one group received HWB, while the other did not. Decrease in rectal temperature 15 min after intubation was significantly smaller in the group using HWB than in the group without HWB. In conclusion, the use of hot water bottles might be one of the methods to attenuate hypothermia in the early period but should not be expected for complete prevention of hypothermia, and it was not recommendable necessarily for body temperature management during MRI examinations in dogs under general anesthesia.

Direct admission of stroke in MRI room reduces in-hospital delays and improves recovery

PurposeEfficacy of intravenous thrombolysis (IVT) and mechanical thrombectomy (MT) is strongly time dependent in acute stroke management. We investigated the impact of a direct magnetic resonance imaging (MRI) room admission protocol in order to reduce in-hospital delays. MethodsWe implemented a protocol of direct MRI room admission, bypassing the Emergency Department. We compared in-hospital delays, clinical and functional outcomes using National Institute of Health Stroke Scale (NIHSS) and modified Rankin Scale (mRS) scores, between patients hospitalized via this protocol and those admitted via the standard workflow and treated by IVT and/or MT. The primary endpoint was the proportion of patients with door-to-needle time (DTN) ≤ 60minutes. ResultsAmong 308 consecutive patients included, 62 underwent direct MRI room admission. The proportion of patients with DTN ≤ 60minutes was higher in the intervention group compared to the control group (82.5% vs. 17.8%, P<0.001), and median DTN was lower (45min vs. 75min, P<0.001). Despite a functional benefit at discharge on dichotomized mRS (mRS [0-2, as independence]: 66.1% vs. 51.2%, P=0.003), the difference was no longer statistically significant at six months (68.4% vs. 57.4%, P=0.10). ConclusionDirect MRI room admission of stroke alerts is associated with an important reduction of treatment times and improves functional outcomes.

Evaluation of the Efficacy of Propofol-Magnesium Sulfate Combination for Sedation in Paediatric Magnetic Resonance Imaging of Brain.- a Randomized Controlled Trial

Background and Aims: The key to successful sedation for pediatric magnetic resonance imaging (MRI) is to keep the child completely immobile while ensuring rapid recovery. We compared the efficacy of propofol-midazolam and propofol-magnesium sulfate sedation for MRI of the brain in the paediatric population. Methods: Total 60 paediatric patients, aged 1 to 8 years awaiting for MRI brain were randomly allocated into two groups. Group I patients received midazolam 0.05mg/kg and Group II patients received magnesium sulfate 30 mg/kg infusion in the preinduction room. In the MRI room all patients were sedated with 1-2 mg/kg bolus and 100 ug/kg/min infusion of propofol. The two groups were compared for sedation characteristics like discharge time, total number of additional propofol boluses, agitation scores, haemodynamic parameters and adverse events. Fisher exact test was used for all quantitative data. Results: Induction time, scan quality, requirement of additional propofol boluses and awakening time were comparable for the groups (P&gt;0.05). There was no statistically significant incidence of airway instrumentation between both groups (p=0.14)). Heart rate remained on lower normal side, 20 minutes after induction in Group II (P&lt;0.00). Incidence of emergence agitation was significantly lower in Group II (P&lt;0.01). The discharge time was shorter in Group II (41.03 ± 8.39 min versus 32.83 ± 5.97 min; P&lt;0.001). Conclusion: Propofol-magnesium sulfate sedation is a better alternative to propofol-midazolam combination for paediatric brain MRI, as it provides a shorter discharge time and a lower incidence of emergence agitation.

Study on the radiofrequency transparency of electrically floating and ground PET inserts in a 3T clinical MRI system.

The positron emission tomography (PET) insert for a magnetic resonance imaging (MRI) system that implements the radiofrequency (RF) built-in body coil of the MRI system as a transmitter is designed to be RF-transparent, as the coil resides outside the RF-shielded PET ring. This approach reduces the design complexities (e.g., large PET ring diameter) related to implementing a transmit coil inside the PET ring. However, achieving the required field transmission into the imaging region of interest (ROI) becomes challenging because of the RF shield of the PET insert. In this study, a modularly RF-shielded PET insert is used to investigate the RF transparency considering two electrical configurations of the RF shield, namely the electrical floating and ground configurations. The purpose is to find the differences, advantages and disadvantages of these two configurations. Eight copper-shielded PET detector modules (intermodular gap: 3mm) were oriented cylindrically with an inner diameter of 234mm. Each PET module included four-layer Lutetium-yttrium oxyorthosilicate scintillation crystal blocks and front-end readout electronics. RF-shielded twisted-pair cables were used to connect the front-end electronics with the power sources and PET data acquisition systems located outside the MRI room. In the ground configuration, both the detector and cable shields were connected to the RF ground of the MRI system. In the floating configuration, only the RF shields of the PET modules were isolated from the RF ground. Experiments were conducted using two cylindrical homogeneous phantoms in a 3T clinical MRI system, in which the built-in body RF coil (a cylindrical volume coil of diameter 700mm and length 540mm) was implemented as a transceiver. For both PET configurations, the RF and MR imaging performances were lower than those for the MRI-only case, and the MRI system provided specific absorption ratio (SAR) values that were almost double. The RF homogeneity and field strength, and the signal-to-noise ratio (SNR) of the MR images were mostly higher for the floating PET configuration than they were for the ground PET configuration. However, for a shorter axial field-of-view (FOV) of 125mm, both configurations offered almost the same performance with high RF homogeneities (e.g., 76±10%). Moreover, for both PET configurations, 56±6% larger RF pulse amplitudes were required for MR imaging purposes. The increased power is mostly absorbed in the conductive shields in the form of shielding RF eddy currents; as a result, the SAR values only in the phantoms were estimated to be close to the MRI-only values. The floating PET configuration showed higher RF transparency under all experimental setups. For a relatively short axial FOV of 125mm, the ground configuration also performed well which indicated that an RF-penetrable PET insert with the conventional design (e.g., the ground configuration) might also become possible. However, some design modifications (e.g., a wider intermodular gap and using the RF receiver coil inside the PET insert) should improve the RF performance to the level of the MRI-only case.

The impulse noise of TMS inside a 3 T and 9.4 T MRI

Abstract The operation of a transcranial magnetic stimulation (TMS) coil produces high-intensity impulse sounds. In TMS, a magnetic field is generated by a short-duration pulse in the range of thousands of amperes in the coil. When placed in a strong magnetic field, such as inside an magnetic resonance imaging (MRI) bore, the interaction of the magnetic field and the current in the TMS coil can cause strong forces on the coil casing. The strengths of these forces depend on the coil orientation in the main magnetic field (B0). Part of the energy in this process is dissipated in the form of acoustic noise. To conduct concurrent TMS and functional MRI (fMRI) safely, the sound pressure levels (SPLs) generated by the TMS coil must be quantitatively characterized. Measuring the SPLs of fast and loud impulse sounds accurately in the presence of static and gradient magnetic fields is challenging. In this study, we present a method for such measurements and report the SPLs of two commercial MRI-compatible TMS systems inside a 3T MRI scanner and of a prototype multi-channel TMS (mTMS) system inside a 9.4T small-animal MRI scanner. The mTMS coil allows for changing the direction of the electric field (E-field) without physically moving the TMS coil. We measured the acoustic noise generated by the TMS coils with different E-field orientations relative to the B0 field at different stimulation intensities and locations. The measurements were compared to the sound level measured outside the MRI room. SPLs and spectrum of the click sounds changed depending on coil and induced E-field orientation compared to the B0 field. SPLs exceeding the safety limit of 140 dB(C) was measured with all the devices. Our study provide is an important step towards the safety operation of concurrent TMS-fMRI respecting the auditory limits of small animals and humans. Keywords: TMS, mTMS, fMRI, acoustic noise

Effect of an Insulation Device in Preventing Hypothermia during Magnetic Resonance Imaging Examinations for Dogs and Cats under General Anesthesia.

Simple SummaryMagnetic resonance imaging examinations require general anesthesia, and it is difficult to prevent a decrease in body temperature because a machine for warming the body cannot be placed in the magnetic resonance imaging room, which must have a low room temperature. In this study, we created a heat insulating device that does not affect magnetic resonance imaging and examined the effectiveness of this device for dogs and cats undergoing magnetic resonance imaging examinations. In the dogs and cats wearing bubble wrap and down cloth blanket, the decrease in body temperature was minimal. The heat insulating device developed in this study protected the animals from the cold air and prevented heat loss from the body surface, minimizing a decrease in body temperature. The results obtained in this study suggest that dogs and cats requiring magnetic resonance imaging can be protected from hypothermia due to general anesthesia without the need for special machinery.Dogs and cats under general anesthesia may develop hypothermia. When performing a magnetic resonance imaging (MRI) examination, it is not possible to place a magnetic material in the MRI room, and MRI equipment requires a low room temperature. This study investigated the effectiveness of a heat insulating device that prevented hypothermia during MRI examinations in dogs and cats. The animals that underwent MRI examinations under general anesthesia were divided into control groups (no covering) and heat insulating groups (wearing bubble wrap and down cloth blankets), and their body temperatures were measured before and after the MRI examinations. The changes in body temperatures were as follows: control dogs (n = 17), median of −1.0 (from −2.5 to 0.3) °C; heat insulated dogs (n = 7), −0.3 (from −0.8 to 0.2) °C; control cats (n = 14), −1.85 (from −2.7 to −0.6) °C; and heat insulated cats (n = 12), −0.8 (from −1.5 to −0.1) °C. These results revealed that the bubble wrap and down cloth blanket significantly prevented hypothermia and heat loss from the body surface during MRI examinations of dogs and cats.

Experimental and Modeling Analyses of Human Motion Across the Static Magnetic Field of an MRI Scanner.

It is established that human movements in the vicinity of a permanent static magnetic field, such as those in magnetic resonance imaging (MRI) scanners induce electric fields in the human body; this raises potential severe risks of health to radiographers and cleaners exposed routinely to these fields in MRI rooms. The relevant directives and parameters, however, are based on theoretical models, and accurate studies on the simulation of the effects based on human movement data obtained in real conditions are still lacking. Two radiographers and one cleaner, familiar with MRI room activities and these directives, were gait analyzed during the execution of routine job motor tasks at different velocities. Full body motion was recorded in a gait laboratory arranged to reproduce the workspace of a room with an MRI full-body scanner. Body segments were tracked with clusters of at least three markers, from which position and velocity of the centroids were calculated. These were used as input in an established computer physical model able to map the stray field in an MRI room. The spatial peak values of the calculated electric field induced by motion of the head and of the entire body during these tasks, for both the health and sensory effects, were found smaller than the thresholds recommended by the European directives, for both 1.5 T and 3.0 T MRI. These tasks therefore seem to guarantee the safety of MRI room operators according to current professional good practice for exposure risks. Physical modeling and experimental measures of human motion can also support occupational medicine.

A Robotic Platform to Navigate MRI-guided Focused Ultrasound System

Focused ultrasound (FUS) technology attracts increasing interests accrediting to its non-invasive and painless treatment of tumors. Magnetic resonance imaging (MRI) guidance has been introduced to monitor this procedure, thus allowing the ultrasound foci to be precisely controlled. However, manual positioning of the FUS transducers is challenging, especially for the intra-operative (intra-op) adjustment in the MRI room. Currently, there are very few devices capable to provide robotic transducer positioning for the treatment of abdominopelvic organ diseases under MRI. The high intensity focused ultrasound (HIFU) spot would have to be “steered” to ablate large (>Ø 3.5 cm) or multiple tumors (e.g., in liver). To this end, we proposed a hydraulic-driven tele-operated robot platform that enables 5-DoF manipulation of the FUS transducer. Even operated close to the MRI iso-center, the robot can guarantee zero electromagnetic (EM) artifact to the MR image. Our proof-of-concept robot prototype can offer a large workspace (100 mm × 100 mm × 35 mm) for FUS foci steering. Accurate manipulation (0.2 mm in translation, 0.4° in rotation) of the FUS transducer holder is achieved using rolling diaphragm-sealed hydraulic actuators. The robot control responsiveness (from 0.1 to 4 Hz) is also evaluated to show the potential to compensate for the spot tracking error induced by respiratory motion. We also demonstrate the use of wireless radiofrequency (RF) markers to continuously register the robot task space in the MRI coordinates.

The Cinderellas of the scanner: Magnetic resonance imaging 'pre-scan' and 'post-scan' times: Their determinants and impact on patient throughput.

BackgroundIncreasing demand for magnetic resonance imaging (MRI) has contributed to extended patient waiting times worldwide. This is particularly true in resource-limited environments, prompting this institutional workflow analysis.ObjectiveTo determine the ‘pre-’ and ‘post-scan’ times for normal-hour MRI studies conducted at a tertiary-level, public-sector South African hospital and to assess any association with demographic details, patient characteristics, anatomical site and scan parameters. A secondary objective was determination of the average daily MR ‘down’ time.MethodsA prospective descriptive study stratifying MRI workflow into ‘pre-scan’, ‘scan’, ‘post-scan’ and ‘down’ times. During ‘pre-‘ and ‘post-scan’ times patients occupied the scanner whilst staff performed tasks indirectly contributing to image acquisition. During ‘down’ time no patient occupied the MRI room. ‘Pre-’ and ‘post-scan’ times were compared with demographic details, patient characteristics, anatomical site and study parameters, utilising correlation analysis or analysis of variance (ANOVA).ResultsA total of 223 patients (n = 223) underwent 286 investigations in the 23-day review period. Seventy per cent of routine working time was utilised in image acquisition. The ‘pre-’ and ‘post-scan’ times together accounted for 19% and ‘down’ time for 11% of working time. Prolonged ‘pre-’ and ‘post-scan’ times were independently associated with age less than 12 years, anaesthesia, sedation and immobility (p < 0.01 in all cases). The longest median combined ‘pre-’ and ‘post-scan’ time by anatomical site (cholangiopancreatography, 21:46 min) was more than six times the shortest (pituitary fossa, 3:11 min).ConclusionA critical analysis of magnetic resonance ‘pre-’ and ‘post-scan’ times can provide valuable insights into opportunities for enhanced service efficiency.

Coronavirus disease 2019: MRI examination procedures and infection prevention and protection.

BackgroundThough chest computed tomography (CT) and digital radiography (DR) is important in the diagnosis and treatment of COVID-19, for patients with COVID-19 who may need magnetic resonance imaging (MRI) due to other complications, we proposed the MRI procedures for patients and medical staff to reduce the risk of infection between them.MethodsCombining two cases in our hospital and other literature, a solution about the procedure and necessary preventive and protective measures for MRI examination of COVID-19 patients is proposed for peer reference with the help of experts from our hospital infection-control department. The solution that meets the hospital infection-control regulations covers five aspects including the layout requirements for the MRI room in the radiology department, preparation before admission, preparation of medical staff, preparation of patients, and terminal disinfection after MRI examination. Radiology personnel should strictly abide by the regulations on infection prevention and control. MRI technicians who have been in close contact with COVID-19 patients should receive strict medical observation for two weeks. Each step should be performed carefully to minimize the risk of hospital infection.ResultsA solution that includes five aspects was formulated to prevent the potential contamination during the MRI scan for COVID-19 patients. These five aspects are layout requirements in the MRI room, preparation before admission, preparation of medical staff, preparation of patients, and terminal disinfection after an examination. MRI technicians who have been in close contact with COVID-19 patients should receive strict medical observation for two weeks.ConclusionsTo prevent and control the potential hospital infection during the MRI examination for COVID-19 patients, a solution including five aspects was initially proposed.

Characterizing Vocal Tract Dimensions in the Vocal Modes Using Magnetic Resonance Imaging

The aim was to study vocal tract dimensions in four vocal modes - Neutral, Curbing, Overdrive and Edge - from Complete Vocal Technique (CVT) by means of magnetic resonance imaging (MRI). Furthermore, the purpose was to test the feasibility of MRI to assess CVT vocal modes. Four nonclassical singers (two females, two males) trained in CVT were imaged with an MRI scanner while singing sustained vowels at same pitch (Bb4 for females, F4 for males) in all vocal modes. Audio signals were simultaneously recorded through a pipe for quality assurance purposes. Auditory evaluation was performed by three CVT teachers in the scanner control room via headphones, and by one CVT teacher inside the MRI room. Previously developed measurement models modified by the authors were used to measure vocal tract dimensions from sagittal MRI projections. Repeatability test was performed for all measurements. In all subjects, vocal tract dimensions displayed differences between the vocal modes. Edge stood out from other vocal modes by showing most laryngeal narrowing accompanied by shortest vocal tract and highest vertical laryngeal position. For Neutral, least mouth opening and shortest distance between tongue and palate were found. Curbing differed consistently from Edge and somewhat from Overdrive showing higher measured values for vocal fold length. Differences regarding vocal fold length were also detected between Neutral and Edge. As expected, differences in vocal tract dimensions were found between samples sung with different vowels. Vocal tract adjustments play a key role in the production of the vocal modes. The model used to measure vocal tract dimensions succeeded in finding significant differences between the vocal modes, also detecting differences between different vowel productions. The method used to characterize vocal tract dimensions seem promising and would be worthwhile to apply to a larger material.