Intraoperative and interventional MRI: recommendations for a safe environment.

In this paper we report on current experience and review magnetic resonance safety protocols and literature in order to define practices surrounding MRI-guided interventional and surgical procedures. Direct experience, the American College of Radiology White paper on MR Safety, and various other sources are summarized. Additional recommendations for interventional and surgical MRI-guided procedures cover suite location/layout, accessibility, safety policy, personnel training, and MRI compatibility issues. Further information is freely available for sites to establish practices to minimize risk and ensure safety. Interventional and intraoperative MRI is emerging from its infancy, with twelve years since the advent of the field and well over 10,000 cases collectively performed. Thus, users of interventional and intraoperative MRI should adapt guidelines utilizing universal standards and terminology and establish a site-specific policy. With policy enforcement and proper training, the interventional and intraoperative MR imaging suite can be a safe and effective environment.     

Safety Planning for Intraoperative Magnetic Resonance Imaging

An intraoperative magnetic resonance imaging (MRI) suite (ie, a type of hybrid OR) is a high-risk zone that requires well-defined safety procedures to avoid adverse events related to magnetic forces. At one facility, the opening of an MRI suite necessitated the creation of a safety plan to establish guidelines, procedures, education, and nursing care specific to the use of MRI technology in the operative environment. Formation of a steering committee enabled a multidisciplinary approach to planning and implementation. The addition of two new perioperative nursing roles (ie, MRI control room monitor, MRI safety nurse) addressed staffing challenges related to strictly enforcing MRI safety procedures and delineating duties different from those of the RN circulator. Benefits of a safe approach to an MRI-integrated operative setting included the elimination of an entire surgical experience for patients who underwent additional resection of the tumor during their initial surgical procedure instead of postoperatively or during a subsequent return to the OR.     

MR imaging in assessing cardiovascular interventions and myocardial injury

Performing an MR‐guided endovascular intervention requires (1) real‐time tracking and guidance of catheters/guide wires to the target, (2) high‐resolution images of the target and its surroundings in order to define the extent of the target, (3) performing a therapeutic procedure (delivery of stent or injection of gene or cells) and (4) evaluating the outcome of the therapeutic procedure. The combination of X‐ray and MR imaging (XMR) in a single suite was designed for new interventional procedures. MR contrast media can be used to delineate myocardial infarcts and microvascular obstruction, thereby defining the target for local delivery of therapeutic agents under MR‐guidance. Iron particles, or gadolinium‐ or dysprosium‐chelates are mixed with the soluble injectates or stem cells in order to track intramyocardial delivery and distribution. Preliminary results show that genes encoded for vascular endothelial and fibroblast growth factor and cells are effective in promoting angiogenesis, arteriogenesis, perfusion and LV function. Angiogenic growth factors, genes and cells administered under MR‐guided minimally invasive catheter‐based procedures will open up new avenues in treating end‐stage ischemic heart disease. The optimum dose of the therapeutic agents, delivery devices and real‐time imaging techniques to guide the delivery are currently the subject of ongoing research. The aim of this review is to (1) provide an updated review of experiences using MR imaging to guide transcatheter therapy, (2) address the potential of cardiovascular magnetic resonance (MR) imaging and MR contrast media in assessing myocardial injury at a molecular level and labeling cells and (3) illustrate the applicability of the non‐invasive MR imaging in the field of angiogenic therapies through recent clinical and experimental publications. Copyright © 2007 John Wiley & Sons, Ltd.     

Setting up MR compatibility of a commercial stereo-localization system for low-field open MR interventional procedures

Introduction

? Surgical and interventional procedures increasingly rely on spatial measurement systems. One of the most popular is NDI’s Polaris Vicra®. Unfortunately, this system cannot be used for magnetic resonance imaging (MRI) procedures because of the image artifacts that it produces.

Materials and methods

? Here, a simple method for hardware electrical shielding is presented which makes the Polaris Vicra® MR-compatible for a low-field open-magnet MR scanner. The shielding is achieved by placing the cable linking the sensor to the USB converter inside a copper braid tube.

Results

? Tests performed with a variety of MR sequences show the absence of image artifacts, image distortion or grey-level uniformity degradation. In the same way, 3D localization accuracy of the spatial measurement system is not modified by the MR environment. A rough safety check shows that the system does not pose hazards with normal condition of use.

Conclusion

? This minor adaptation makes the system suitable for various applications in low field MR environments, such as intraoperative and interventional MRI.     

Prerequisites for magnetic resonance image-guided interventions and endoscopic surgery

Summary

Our purpose was to evaluate technological prerequisites and predural principles that enable easy, precise and reproducible magnetic resonance imaging control of interventional procedures, such as biopsy and aspiration of neoplasm or local interstitial drug instillation in adequate time and with the required safety. New MR compatible needles, trocars/cannulae, endoscopes and ancillary equipment were developed or evaluated in collaboration with industry. Sequences, study protocols and the strategies of performing the procedure within the environment of an interventional MRI suite were conceptualized and tested. In 80 patients interventions such as aspiration biopsy, peridural corticoid injection at spinal nerve roots and intratumoural ethanol instillation were performed successfully.     

Building a Magnetic Resonance Imaging Safety Culture from the Ground Up

Magnetic resonance imaging (MRI) uses a strong magnetic field to generate diagnostic images. This magnetic field has the potential to cause serious and even fatal injuries to patients undergoing scans and to personnel in the area. Ensuring awareness of MRI hazards and safety procedures through a formalized education and training program is integral in creating an MRI safety culture that protects patients and staff from harm. The aim of our project was to develop an accessible and interprofessional electronic e-module learning series to instill an MRI safety culture throughout the entire hospital. This is the first such program in Canada. A simplified e-search was conducted using key search terms “mri: safety, education, safety training.” Very few articles were found that fulfilled our needs in helping us build an MRI safety program. In concert with an e-search we reached out to similar institutions and, through informal discussions, we confirmed the lack of a formalized, transferable safety program within Canada. This led to the creation of an interprofessional working team at our institution composed of key stakeholders: educators, clinical and technical experts from radiation therapy, medical imaging, the research institute, medical radiation physics, nursing, and radiation oncology. This team collaborated on the development of three education modules tailored for specific audiences based on classification as Non-MR Personnel, Level 1 MR Personnel, or Level 2 MR Personnel as defined by the American College of Radiology guidelines. All modules were 10 to 20 minutes in length with interactive engagement activities throughout as well as a final summative evaluation to test for comprehension. Knowledge of the existence of the MRI unit is only one facet of creating an MRI safety culture. By increasing the awareness of the hazards of MRI to all personnel throughout the hospital, the risk of harm to patients and staff may be decreased.     

MRI-powered biomedical devices

Magnetic resonance imaging (MRI) is beneficial for imaging-guided procedures because it provides higher resolution images and better soft tissue contrast than computed tomography (CT), ultrasound, and X-ray. MRI can be used to streamline diagnostics and treatment because it does not require patients to be repositioned between scans of different areas of the body. It is even possible to use MRI to visualize, power, and control medical devices inside the human body to access remote locations and perform minimally invasive procedures. Therefore, MR conditional medical devices have the potential to improve a wide variety of medical procedures; this potential is explored in terms of practical considerations pertaining to clinical applications and the MRI environment. Recent advancements in this field are introduced with a review of clinically relevant research in the areas of interventional tools, endovascular microbots, and closed-loop controlled MRI robots. Challenges related to technology and clinical feasibility are discussed, including MRI based propulsion and control, navigation of medical devices through the human body, clinical adoptability, and regulatory issues. The development of MRI-powered medical devices is an emerging field, but the potential clinical impact of these devices is promising.     

Capturing intraoperative deformations: research experience at Brigham and Women's Hospital

During neurosurgical procedures the objective of the neurosurgeon is to achieve the resection of as much diseased tissue as possible while achieving the preservation of healthy brain tissue. The restricted capacity of the conventional operating room to enable the surgeon to visualize critical healthy brain structures and tumor margin has lead, over the past decade, to the development of sophisticated intraoperative imaging techniques to enhance visualization. However, both rigid motion due to patient placement and nonrigid deformations occurring as a consequence of the surgical intervention disrupt the correspondence between preoperative data used to plan surgery and the intraoperative configuration of the patient's brain. Similar challenges are faced in other interventional therapies, such as in cryoablation of the liver, or biopsy of the prostate. We have developed algorithms to model the motion of key anatomical structures and system implementations that enable us to estimate the deformation of the critical anatomy from sequences of volumetric images and to prepare updated fused visualizations of preoperative and intraoperative images at a rate compatible with surgical decision making. This paper reviews the experience at Brigham and Women's Hospital through the process of developing and applying novel algorithms for capturing intraoperative deformations in support of image guided therapy.     

Intraoperative MR imaging

Intraoperative MR imaging has become a safe and effective technology that has revolutionized the way neurosurgery is performed. Benefits include the ability to update data sets for navigational systems, to monitor tumor resections, to adjust the approach to intracranial lesions, and to guide functional and drug or cell delivery procedures. Use of this technique can help avoid inadvertent injury of important anatomic and vascular structures. In addition, complications such as ischemia or hemorrhage can be detected early. Intraoperative MR imaging is particularly useful for ensuring that brain biopsies yield diagnostic tissue and for assessing the completeness of tumor resection. As is true for any new technology, the benefits of intraoperative MR imaging must be examined carefully to guarantee appropriate use. Many neurosurgical procedures do not require real-time image guidance and can be performed safely using current surgical techniques, including microsurgical methods and frameless and frame-based stereotaxy. Other tumor resections, tumor biopsies, and surgical and interventional procedures distinctly benefit from the sophisticated information provided by intraoperative imaging techniques. In surgery for low-grade gliomas, intraoperative MR imaging has found general acceptance, whereas its usefulness to monitor the resection of high-grade gliomas remains controversial. The economic issues related to intraoperative MR imaging cannot be overlooked. The acquisition of an intraoperative MR imaging system is associated with considerable expense, and its performance increases the cost of equipment and the operating time. Despite these additional expenses, intraoperative MR imaging can lead to a potential overall cost reduction in the treatment of certain patients if long-term cure can be achieved, repeat resection can be avoided, or procedure-associated morbidity can be reduced. Although intraoperative MR imaging techniques hold tremendous potential, the definition of their appropriate role in the delivery of successful and cost-effective medical care awaits further study.     

磁共振导航微创技术在脑肿瘤的诊治现状与进展

磁共振导航技术用于脑肿瘤的诊断与治疗具有以下优势：①为整个手术过程提供精准的定位,清晰显示脑肿瘤和毗邻组织的解剖学关系;术中MR提供实时更新的图像可以最大限度地减少对瘤周正常脑组织和功能的破坏。②MRI对肿瘤边界的显示比肉眼观察准确,有利于提高脑肿瘤的总切除率。③术中MRI有助于发现诸如出血等发并症,并及进处理。④功能性MRI和动态增强MRI还能够进一步提高手术的安全性和有效性。本文对磁共振导航技术在脑肿瘤微创诊疗中的应用进行回顾分析。     

Integrating Image-Guidance into the Cardiac Operating Room

In a specially-designed suite integrating advanced angiography equipment (Advantix, GE, Milwaukee) and standard operating room (OR) facilities, 562 interventions were performed in the course of 3 years. Of these, 83 were cardiac operations, 62 radiologic-guided cardiac interventions and 93 cardiac angiographies. The introduction of angiography into the OR allowed hybrid procedures, combining surgical and interventional coronary revascularisation. Animal studies were performed in the same suite, developing minimally-invasive procedures, as well as robotic surgery. Future cardiac suites will probably contain equipment for short-bore fast-pulse sequence MRI and robots.     

Aerosols and gaseous contrast agents for magnetic resonance imaging of the lung

Magnetic resonance imaging of lungs and the investigation of pulmonary pathologies with this technique are limited by low proton spin density, degraded magnetic homogeneity and motion. Inhaled contrast agents (gases or aerosols) can improve the diagnostic value of MRI for lung. Paramagnetic contrast agents such as gadolinium chelates aerosol or dioxygen gas increase the relaxivity of proton in lung parenchyma and can be used to assess the ventilated fraction of the bronchoalveolar space. Similarly, inhalation of non proton‐MRI nuclei such as perfluorinated gas or hyperpolarized gases (³He or ¹²⁹Xe) can provide functional ventilation image. In this review paper, the principles, the practical implementation, the limitations and possible safety issues of these different techniques are summarized. The main pre‐clinical and clinical applications of these approaches based on oral contrast agents are reviewed and illustrated with cutting‐edge lung MRI studies. Copyright © 2008 John Wiley & Sons, Ltd.     

单次激发磁共振水成像技术对脊柱侧弯的应用价值

目的探讨单次激发磁共振水成像(single shot MR hydrography,ssh MRH)技术在脊柱侧弯患者全脊柱MRI检查中的应用价值.方法使用Philips Achieva 1.5T双梯度超导磁共振成像系统和全神经系统组合线圈,对200例脊柱侧弯患者行单次激发磁共振水成像,得到全脊髓像,再根据全脊髓像(定位图)设定T1WI和T2WI的扫描方案,分析研究得到的全脊髓像、T1WI、T2WI图像.结果采用ssh MRH技术得到的全脊髓定位图中脊髓显示清楚,拼接良好,能够完整显示全脊髓的弯曲形态,对周边含水组织器官情况显示良好.200例病例中,全脊髓定位图直接显示脊髓空洞20例、脊髓栓系及脊髓纵裂10例、脊髓占位3例、根鞘囊肿13例,胸水10例,女性附件囊肿8例,骶管囊肿8例,蛛网膜囊肿3例,肾积水3例,胸腔囊性占位1例.结论 ssh MRH对侧弯患者的全脊柱MRI具有重要价值,可常规用于侧弯脊柱的MRI定位中.     

Intraoperative magnetic resonance imaging

Intraoperative magnetic resonance imaging (MRI) allows neurosurgeons to perform surgery interactively using magnetic resonance (MR) guidance. Low-field and high-field strength MRI has been developed and implemented for multiple neurosurgical procedures, including brain biopsies, craniotomies for resection of mass lesions, cyst drainages, laminectomies, thermal ablations, functional neurosurgery, and a variety of miscellaneous cases. Both technologies have the advantage over frameless neuronavigational systems of being able to perform near real-time imaging, which allows the surgeon to compensate for intraoperative brain shift. Intraoperative functional techniques such as MR spectroscopy, functional MRI, MR angiography and venography, and diffusion-weighted imaging, which have become routine at some high-field MR units, can significantly influence surgical decision making. The potential complications associated with intraoperative MR-guided neurosurgery are similar in incidence to those seen in the conventional neurosurgical operating room. However, the immediate recognition of such intraoperative complications with MRI should lead to improved outcomes and decreased medical costs. Untoward events associated with performing surgery in an MR environment are uncommon. Intraoperative MR-guided neurosurgery represents a natural progression from framed and frameless stereotactic techniques. Intraoperative MRI is still in its infancy, and the full capabilities of this technology have yet to be determined or implemented.     

Magnetic resonance safety

Magnetic resonance imaging (MRI) has a superior soft-tissue contrast compared to other radiological imaging modalities and its physiological and functional applications have led to a significant increase in MRI scans worldwide. A comprehensive MRI safety training to protect patients and other healthcare workers from potential bio-effects and risks of the magnetic fields in an MRI suite is therefore essential. The knowledge of the purpose of safety zones in an MRI suite as well as MRI appropriateness criteria is important for all healthcare professionals who will work in the MRI environment or refer patients for MRI scans. The purpose of this article is to give an overview of current magnetic resonance safety guidelines and discuss the safety risks of magnetic fields in an MRI suite including forces and torque of ferromagnetic objects, tissue heating, peripheral nerve stimulation, and hearing damages. MRI safety and compatibility of implanted devices, MRI scans during pregnancy, and the potential risks of MRI contrast agents will also be discussed, and a comprehensive MRI safety training to avoid fatal accidents in an MRI suite will be presented.     

A Comparison of MRI Radiographers' Knowledge in Saudi Arabia and the Republic of Ireland in Relation to Image Quality Management,for Abdomen and Pelvic MRI Examinations

PurposeThe purpose of this article was to qualitatively compare current MRI radiographers’ knowledge from Saudi Arabia and the Republic of Ireland in relation to MR image quality for abdominal and pelvic MRI examinations.Methods and materialsSemistructured interviews were designed to investigate the professional role of radiographers towards image quality management, personal development in MRI, and training in relation to image quality improvement. Public, private, military, and academic hospitals in the Western region of the Kingdom of Saudi Arabia participated, as did a range of public and private Irish centres. Clinical specialist radiographers (CSRs)/supervisors, and MR radiographers working in MR completed the interviews. These were recorded, coded, and transcribed.ResultsSixty-one MR radiographers and CSRs/supervisors within 11 MRI departments in the Kingdom of Saudi Arabia and 11 MRI departments in the Republic of Ireland participated in this study. Three themes resulted by using a qualitative data analysis program called NVivo: (1) health care professional and the cultural attitudes with regards to the scope of professional roles, (2) factors affecting image quality, and (3) departmental policy. Participants' knowledge of image quality varied and challenges to achieving optimal quality levels were noted. Differences in clinical practice between countries were identified, as was the impact of clinical experience and levels of education.ConclusionDifferences in attitude and clinical practice between Saudi and Irish radiographers and CSRs/supervisors working in MRI departments were identified. There is a need for further training and subsequent assessment of professional skills, including developing postgraduate opportunities, particularly for Saudi radiographers, to support radiographers in the routine management of MR image quality.     

MRI contrast variation of thermosensitive magnetoliposomes triggered by focused ultrasound: a tool for image‐guided local drug delivery

Improved drug delivery control during chemotherapy has the potential to increase the therapeutic index. MRI contrast agent such as iron oxide nanoparticles can be co‐encapsulated with drugs in nanocarrier liposomes allowing their tracking and/or visualization by MRI. Furthermore, the combination of a thermosensitive liposomal formulation with an external source of heat such as high intensity focused ultrasound guided by MR temperature mapping allows the controlled local release of the content of the liposome. MRI‐guided high‐intensity focused ultrasound (HIFU), in combination represents a noninvasive technique to generate local hyperthermia for drug release. In this study we used ultrasmall superparamagnetic iron oxide nanoparticles (USPIO) encapsulated in thermosensitive liposomes to obtain thermosensitive magnetoliposomes (TSM). The transverse and longitudinal relaxivities of this MRI contrast agent were measured upon TSM membrane phase transition in vitro using a water bath or HIFU. The results showed significant differences for MRI signal enhancement and relaxivities before and after heating, which were absent for nonthermosensitive liposomes and free nanoparticles used as controls. Thus, incorporation of USPIO as MRI contrast agents into thermosensitive liposomes should, besides TSM tumor accumulation monitoring, allow the visualization of TSM membrane phase transition upon temperature elevation. In conclusion, HIFU under MR image guidance in combination with USPIO‐loaded thermosensitive liposomes as drug delivery system has the potential for a better control of drug delivery and to increase the drug therapeutic index. Copyright © 2012 John Wiley & Sons, Ltd.     

Neurosurgical uses for intraprocedural magnetic resonance imaging

Neurosurgical procedures demand precision, and efforts to create accurate neurosurgical navigation have been central to the profession through its history. Magnetic resonance image (MRI)-guided navigation offers the possibility of real-time, image-based stereotactic information for the neurosurgeon, which makes possible a number of diagnostic and therapeutic procedures. This article will review both current options for intraoperative MRI operative suite arrangements and the current therapeutic/diagnostic uses of intraoperative MRI.     

MR-compatible laparoscope with a distally mounted CCD for MR image-guided surgery

Objects We have developed a new MR-compatible laparoscope that incorporates a distally mounted charge-coupled device (CCD). The MR-compatibility and feasibility of laparoscopy using the new laparoscope were evaluated during MR image-guided laparoscopic radiofrequency ablation therapy (RFA). Materials and methods MR compatibility of the laparoscope was investigated in terms of MR image artifact caused by electromagnetic interference (EMI) and susceptibility. MR images were obtained using spin echo and gradient echo pulse sequences with a 0.3 T open MRI unit. We performed an in vivo experiment with MR image-guided laparoscopic RFA on three pigs; near real-time MR images and 3-D navigation were possible using intraoperative MR images. Agarose gel was injected into the pigs’ livers as puncture targets; the diameter of each target was approximately 20 mm. Results Artifacts resulting from EMI were not found in phantom experiments. MR image-guided laparoscopic RFA was successfully performed in all procedures. Both the laparoscopic vision and near real-time MR images were clear. No artifact was detected on the MR images and the surgeon was able to confirm the true position of the probe and target during treatment using the near real-time MR images. Conclusion Laparoscopic surgery is feasible under intraoperative MR image-guidance using a newly developed MR-compatible laparoscope with a distally mounted CCD.