Health and safety control measures and MR quality control results in the MRI units of two public hospitals within the Mangaung metropolitan

This study aimed to identify risks and hazards in the magnetic resonance imaging (MRI) units, and assess the quality compliance of the scanners within two public hospitals in Mangaung. This is a follow-up study from a previously published study that measured static magnetic fields and radiofrequency magnetic fields in the MRI units included here. An observational checklist was used to identify risks and hazards which were later fed into a baseline risk assessment to classify and review existing control measures in the MRI units of hospitals A and B. The availability of MRI Health and Safety measures were benchmarked against the latest American College of Radiology (ACR) MRI safety requirements. The probability of risk occurrence and severity of hazards were assigned a score ranging from improbable (1) to very likely (5) and minimal (1) to irreversible effect (5). The weekly quality control test results obtained from both units were measured against the ACR quality control acceptable criteria. Similar risks were observed in both MRI units but the multiplication of probability and consequence in all risk categories resulted in a moderate risk-rating score of 12.3 for hospital A and 13.1 for hospital B. Lack of demarcation of four MRI safety zones, ferromagnetic detectors, 5-gauss line, and access control in both units scored above 15 and were classified as high risk. The defective air-cooling systems influenced the temperature of the scanner room, which affected the apparent diffusion coefficient (ADC) measurements performed from 1.5 T Siemens. On a 3.0 T Philips, a low contrast object detectability had 29 spokes for ACR T2, while the percent integral uniformity for image intensity uniformity was 78.2 %. High and moderate risks observed in both units could be reduced by the implementation of an effective health and safety programme. The ambient temperature within the scanner room should be maintained at 21 °C to attain well-performing ADC measurements and RF subsystems should be visually inspected and maintained regularly to obtain optimal image quality.

MRI safety wih abandoned or functional epicardial pacing leads

Funding Acknowledgements Type of funding sources: Public hospital(s). Main funding source(s): HUS Medical Imaging Center research grant Background The Heart and Rhythm Society’s consensus statement 2017 approves magnetic resonance imaging (MRI) with cardiac implantable electronic devices (CIED), but excludes patients with epicardial and abandoned leads. Potential safety hazards of an MRI with epicardial pacing leads include heating of the tip of the lead and induction of current in the pacing lead resulting in inappropriate cardiac stimulation. Only a few small studies of MRI safety with epicardial pacing leads have been published and adverse events have been rare. The clinical dilemma remains, whether performing an MRI on a patient with CIED and epicardial pacing leads is safe. We have performed MRIs on patients with CIED and epicardial pacing leads when benefits have been considered to outweigh the risks after careful case-by-case evaluation following our institutional MRI with CIED safety protocol. Purpose The aim of this study was to evaluate the safety of performing an MRI scan on patients with CIED and abandoned or functional epicardial pacing leads. Methods All the clinically indicated MRI examinations conducted on adult patients with CIED and functional or abandoned epicardial leads (n = 24) performed in our hospital between November 2011 and October 2019 were included in this observational retrospective study. The data were retrospectively collected from electronic medical records. Results Altogether 24 MRIs were performed to 16 patients with functional or abandoned epicardial pacing leads (Table). 93.8% (15/16) patients had congenital heart disease. Cardiac MRI was the most frequent examination (21/24, 91.7%). 66.7% of the MRI scans (16/24) were conducted on patients with functional epicardial pacing leads. In 5/24 (20.8%) MRIs, the patient was pacemaker-dependent. A clinically significant event occurred in one MRI scan. This was transient elevation of the pacing lead threshold in a patient with functional epicardial ventricular pacing lead, that was implanted 29 years prior to the MRI. In another patient with 30-year-old functional epicardial pacing leads, clinically significant irreversible elevation in atrial pacing lead impedance was detected 6 months after the MRI and unlikely related to previous MRI examination. None of the patients experienced sensations leading to cessation of the MRI scans. No clinically significant pacing lead parameter changes were detected after MRIs performed on patients with modern (implanted year 2000 or later) functional epicardial pacing leads or functional endocardial leads and abandoned epicardial leads. Conclusions MRI examinations in patients with CIED and modern functional epicardial pacing leads were performed without detectable adverse events. Performing an MRI with old functional epicardial pacing leads may involve more risks.

What Radiologist Should Know about MRI Translational Forces and Hazard: An Ex-Vivo Simulation of Retained Metallic Shrapnel

Background. In a country immersed in endless rounds of wars, retained metallic foreign bodies remain a significant dilemma in the daily practice of every Lebanese radiologist. When a shrapnel’s hazard is of concern, the decision between performing or refusing a justified MRI exam is not always straightforward. In this small trial, we aimed to better understand the shrapnel’s MRI safety by mimicking our daily practice. Methods. Five shrapnel with an incremental increase in their long axis were put in an animal flesh and then introduced into a 3 T magnetic field. The behavior of each shrapnel was concretely assessed by performing before and after magnetic field exposure CT acquisitions. Results. Translation along the z-axis ranged from 0.9 mm to 2.8 mm. Torque angle ranged between 2.8 and 54 degrees with an average of 15.62 degrees. Conclusions. Shrapnel’s movements in the magnetic field are not negligible during the acute phase of injury where there is no reinforcing fibroblastic reaction and invite us to reconsider the MRI safety of these metallic foreign bodies. Standard radiographs may be sufficient, but a targeted CT scan may be of better value for a confident decision for assessment of shrapnel position near viscera and major vessels.

Development, validation, and pilot MRI safety study of a high-resolution, open source, whole body pediatric numerical simulation model

Numerical body models of children are used for designing medical devices, including but not limited to optical imaging, ultrasound, CT, EEG/MEG, and MRI. These models are used in many clinical and neuroscience research applications, such as radiation safety dosimetric studies and source localization. Although several such adult models have been reported, there are few reports of full-body pediatric models, and those described have several limitations. Some, for example, are either morphed from older children or do not have detailed segmentations. Here, we introduce a 29-month-old male whole-body native numerical model, “MARTIN”, that includes 28 head and 86 body tissue compartments, segmented directly from the high spatial resolution MRI and CT images. An advanced auto-segmentation tool was used for the deep-brain structures, whereas 3D Slicer was used to segment the non-brain structures and to refine the segmentation for all of the tissue compartments. Our MARTIN model was developed and validated using three separate approaches, through an iterative process, as follows. First, the calculated volumes, weights, and dimensions of selected structures were adjusted and confirmed to be within 6% of the literature values for the 2-3-year-old age-range. Second, all structural segmentations were adjusted and confirmed by two experienced, sub-specialty certified neuro-radiologists, also through an interactive process. Third, an additional validation was performed with a Bloch simulator to create synthetic MR image from our MARTIN model and compare the image contrast of the resulting synthetic image with that of the original MRI data; this resulted in a “structural resemblance” index of 0.97. Finally, we used our model to perform pilot MRI safety simulations of an Active Implantable Medical Device (AIMD) using a commercially available software platform (Sim4Life), incorporating the latest International Standards Organization guidelines. This model will be made available on the Athinoula A. Martinos Center for Biomedical Imaging website.