Magnetic Resonance Imaging Guidance Research Articles

Focused ultrasound activates voltage-gated calcium channels through depolarizing TRPC1 sodium currents in kidney and skeletal muscle.

Pulsed focused ultrasound (pFUS) technology is being developed for clinical neuro/immune modulation and regenerative medicine. Biological signal transduction of pFUS forces can require mechanosensitive or voltage-gated plasma membrane ion channels. Previous studies suggested pFUS is capable of activating either channel type, but their mechanistic relationship remains ambiguous. We demonstrated pFUS bioeffects increased mesenchymal stem cell tropism (MSC) by altering molecular microenvironments through cyclooxygenase-2 (COX2)-dependent pathways. This study explored specific relationships between mechanosensitive and voltage-gated Ca2+ channels (VGCC) to initiate pFUS bioeffects that increase stem cell tropism.Methods: Murine kidneys and hamstring were given pFUS (1.15 or 1.125 MHz; 4MPa peak rarefactional pressure) under ultrasound or magnetic resonance imaging guidance. Cavitation and tissue displacement were measure by hydrophone and ultrasound radiofrequency data, respectively. Elastic modeling was performed from displacement measurements. COX2 expression and MSC tropism were evaluated in the presence of pharmacological ion channel inhibitors or in transient-receptor-potential-channel-1 (TRPC1)-deficient mice. Immunohistochemistry and co-immunoprecipitation examined physical channel relationships. Fluorescent ionophore imaging of cultured C2C12 muscle cells or TCMK1 kidney cells probed physiological interactions.Results: pFUS induced tissue deformations resulting in kPa-scale forces suggesting mechanical activation of pFUS-induced bioeffects. Inhibiting VGCC or TRPC1 in vivo blocked pFUS-induced COX2 upregulation and MSC tropism to kidneys and muscle. A TRPC1/VGCC complex was observed in plasma membranes. VGCC or TRPC1 suppression blocked pFUS-induced Ca2+ transients in TCMK1 and C2C12 cells. Additionally, Ca2+ transients were blocked by reducing transmembrane Na+ potentials and observed Na+ transients were diminished by genetic TRPC1 suppression.Conclusion: This study suggests that pFUS acoustic radiation forces mechanically activate a Na+-containing TRPC1 current upstream of VGCC rather than directly opening VGCC. The electrogenic function of TRPC1 provides potential mechanistic insight into other pFUS techniques for physiological modulation and optimization strategies for clinical implementation.

Navigated magnetic resonance imaging-guided celiac plexus neurolysis using an open magnetic resonance system for pancreatic cancer patients with upper abdominal pain.

The study aimed to evaluate the safety and efficacy of navigated magnetic resonance imaging (MRI)-guided celiac plexus neurolysis (CPN) using a 0.4 T open magnetic resonance system. A retrospective analysis was performed on 23 patients with unresectable pancreatic cancer who underwent MRI-guided CPN between January 2013 and October 2017. Clinical outcomes were evaluated by recording the complications, the opioid intake, and questionnaire before the intervention and at the time point of 1 day, 1 month, and 3 months postprocedure using a numerical visual analog scale (VAS). Navigated MRI guidance allowed the precise placement of needle in the targeted area and the visualization of the injected neurolysis agents for all cases. The VAS scores decreased from 8.8 ± 1.0 to 2.9 ± 0.9, 4.2 ± 1.7, and 4.7 ± 1.8 at 1 day, 1 month, and 3 months postprocedure (P < 0.05). This intervention reduced the dosage of opioid consumption 1 month after the procedure (52.3 ± 10.4 mg before the treatment vs. 28.2 ± 4.9 mg after the treatment; P < 0.001). Treatment-related side effects included hematoma in one patient, short episodes of diarrhea in three patients, and hypotension in four patients. With the assistance of the navigation system, MRI-guided CPN is a safe and effective treatment approach for managing the upper abdominal pain in patients with unresectable pancreatic cancer.

Evaluation of plan adaptation strategies for stereotactic radiotherapy of lymph node oligometastases using online magnetic resonance image guidance.

Background and purposeRecent studies have shown that the use of magnetic resonance (MR) guided online plan adaptation yields beneficial dosimetric values and reduces unplanned violations of the dose constraints for stereotactic body radiation therapy (SBRT) of lymph node oligometastases. The purpose of this R-IDEAL stage 0 study was to determine the optimal plan adaptation approach for MR-guided SBRT treatment of lymph node oligometastases.Materials and MethodsUsing pre-treatment computed tomography (CT) and repeated MR data from five patients with in total 17 pathological lymph nodes, six different methods of plan adaptation were performed on the daily MRI and contours. To determine the optimal plan adaptation approach for treatment of lymph node oligometastases, the adapted plans were evaluated using clinical dose criteria and the time required for performing the plan adaptation.ResultsThe average time needed for the different plan adaptation methods ranged between 11 and 119 s. More advanced adaptation methods resulted in more plans that met the clinical dose criteria [range, 0–16 out of 17 plans]. The results show a large difference between target coverage achieved by the different plan adaptation methods.ConclusionResults suggested that multiple plan adaptation methods, based on plan adaptation on the daily anatomy, were feasible for MR-guided SBRT treatment of lymph node oligometastases. The most advanced method, in which a full online replanning was performed by segment shape and weight optimization after fluence optimization, yielded the most favourable dosimetric values and could be performed within a time-frame acceptable (<5 min) for MR-guided treatment.

Magnetic Resonance-Guided Focused Ultrasound : Current Status and Future Perspectives in Thermal Ablation and Blood-Brain Barrier Opening.

Magnetic resonance-guided focused ultrasound (MRgFUS) is an emerging new technology with considerable potential to treat various neurological diseases. With refinement of ultrasound transducer technology and integration with magnetic resonance imaging guidance, transcranial sonication of precise cerebral targets has become a therapeutic option. Intensity is a key determinant of ultrasound effects. High-intensity focused ultrasound can produce targeted lesions via thermal ablation of tissue. MRgFUS-mediated stereotactic ablation is non-invasive, incision-free, and confers immediate therapeutic effects. Since the US Food and Drug Administration approval of MRgFUS in 2016 for unilateral thalamotomy in medication-refractory essential tremor, studies on novel indications such as Parkinson’s disease, psychiatric disease, and brain tumors are underway. MRgFUS is also used in the context of blood-brain barrier (BBB) opening at low intensities, in combination with intravenously-administered microbubbles. Preclinical studies show that MRgFUS-mediated BBB opening safely enhances the delivery of targeted chemotherapeutic agents to the brain and improves tumor control as well as survival. In addition, BBB opening has been shown to activate the innate immune system in animal models of Alzheimer’s disease. Amyloid plaque clearance and promotion of neurogenesis in these studies suggest that MRgFUS-mediated BBB opening may be a new paradigm for neurodegenerative disease treatment in the future. Here, we review the current status of preclinical and clinical trials of MRgFUS-mediated thermal ablation and BBB opening, described their mechanisms of action, and discuss future prospects.

High Speed Pneumatic Stepper Motor for MRI Applications.

Presented in this paper is an exploration into the efficacy of a plastic, four-cylinder piston pneumatic motor designed for driving medical instruments inside magnetic resonance imaging (MRI) systems. Because of the increasing use of MRI for diagnostic and interventional purposes and the benefits that could be realized by operating with real-time MR image guidance, there exists a significant need for MRI compliant surgical devices. Some type of actuation mechanism is necessary to drive such devices. The motor can be controlled to operate in a "step" type motion by using pneumatic valves to sequentially apply air pressure to push the piston surfaces, meaning the motor is metal-free and does not use electricity. The stepwise nature of this piston stepper motor is ideal for the accurate, controlled movements required for MRI-guided interventions. The motor was geared down by a gearbox to increase torque. Performance indices determined include output torque and achievable rotational velocity with respect to factors such as air pressure and load conditions. The stepper motor achieved speeds of approximately 2000rpm, and maximum output torques of approximately 19Nmm. The motor represents a high speed pneumatic stepper motor design capable of actuating devices in MR environments without affecting image quality.

Potential benefit of MRI-guided IMRT for flank irradiation in pediatric patients with Wilms’ tumor

Purpose/Objective: Flank irradiation for Wilms' tumor (WT) is currently performed at our institute using a cone-beam computed tomography-guided volumetric modulated arc (VMATCBCT) workflow. By adding real-time magnetic resonance imaging (MRI) guidance to the treatment, safety margins could be reduced. The study purpose was to quantify the potential reduction of the planning target volume (PTV) margin and its dosimetric impact when using an MRI-guided intensity modulated radiation therapy (IMRTMRI) workflow compared to the VMATCBCT workflow.Material/Methods: 4D-CT, MRI and CBCT scans acquired during preparation and treatment of 15 patients, were used to estimate both geometric, motion and patient set-up systematic (∑) and random (σ) errors for VMATCBCT and IMRTMRI workflows. The mean PTV (PTVmean) expansion was calculated using the van Herk formula. Treatment plans were generated using five margin scenarios (PTVmean ± 0, 1 and 2 mm). Furthermore, the IMRTMRI plans were optimized with a 1.5T transverse magnetic field turned-on to realistically model an MRI-guided treatment. Plans were evaluated using dose-volume statistics (p<.01, Wilcoxon).Results: Analysis of ∑ and σ errors resulted in a PTVmean of 5 mm for the VMATCBCT and 3 mm for the IMRTMRI workflows in each orthogonal direction. Target coverage was unaffected by the margin decrease with a mean V95%=100% for all margin scenarios. For the PTVmean, an average reduction of the mean dose to the organs at risk (OARs) was achieved with IMRTMRI compared to VMATCBCT: 3.4 ± 2.4% (p<.01) for the kidney, 3.4 ± 2.1% (p<.01) for the liver, 2.8 ± 3.0% (p<.01) for the spleen and 4.9 ± 3.8% (p<.01) for the pancreas, respectively.Conclusions: Imaging data in children with WT demonstrated that the PTV margin could be reduced isotropically down to 2 mm when using the IMRTMRI compared to the VMATCBCT workflow. The former results in a dose reduction to the OARs while maintaining target coverage.

Iron-gold (Fe2O3@Au) core-shell nano-theranostic for magnetically targeted photothermal therapy under magnetic resonance imaging guidance

Introduction: Photothermal therapy (PTT) is a nanotechnology-assisted cancer hyperthermia approach in which the interaction between laser light and plasmonic nanoparticles generates a localized heating for thermoablation of the tumor. Recent efforts in the area of PTT follow two important aims: (i) exploitation of targeting strategies for preferential accumulation of plasmonic nanoparticles within the tumor and (ii) enabling real-time guidance of PTT operation through employing multimodal imaging modalities. Materials and Methods: In the present study, we utilized a multifunctional theranostic nanoplatform constructed from a magnetic core and Au shell (Fe2O3@Au) in order to fulfill these aims. The Au shell exhibits surface plasmon resonance, a property that is exploited to realize PTT. The magnetic core enables Fe2O3@Au to be used as magnetic resonance imaging (MRI) contrast agent. Furthermore, the magnetic core can also be used to achieve a magnetic drug targeting strategy through which Fe2O3@Au would be concentrated in the tumor site by means of magnetic field. Balb/c mice bearing CT26 colorectal tumor model were intraperitoneally injected with Fe2O3@Au. Immediately after injection, a magnet (magnetic field strength of 0.4 Tesla) was placed on the tumor site for 6 hours in order to concentrate Fe2O3@Au, and thereafter the tumors were irradiated with the near infrared (NIR) laser source (808 nm; 2 W/cm2; 3 min). This experiment was conducted for three sessions. Results: MRI confirmed the accumulation of nanoparticles within the tumor due to T2 enhancement capability of Fe2O3@Au. The temperature of the tumors without magnetic targeting was increased by ~7°C after NIR irradiation, whereas the tumors in magnetic targeting group showed a temperature rise of ~12°C. Conclusion: The in vivo antitumor assessment revealed that intraperitoneal injection of Fe2O3@Au nanoparticles and their targeting via magnetic field toward the tumor followed by NIR irradiation remarkably inhibited tumor growth and induced extensive necrosis. Therefore, Fe2O3@Au can establish a targeted MRI-guided PTT strategy.

Abstract ID:364 MR-Image guidance – Clinical perspective

Purpose The ideal situation for radiotherapy would be a treatment under more or less static conditions in an ideal dosimetric situation with permanent control of the position of tumor, organs-at-risk (OAR) and patient surface. Methods This presentation will outline the current state of the art and explore, if/how/where in-room MR-guidance may go beyond current strategies and what requirements must be fulfilled on the way as layed out in a previous publication [1]. Results If there is a necessity for on line MR-guidance, there is a general necessity for broad use of advanced image guidance strategies, particularly as successful screening programs such as those for lung cancer and potentially even pancreatic cancer are established, as this potentially leads to more localized disease being treated. Several such strategies are now available but are underutilized, typically for lack of funding or perceived complexity. Online MR-image guidance has the ability to simultaneously image and target the cancer and is more intuitive when integrated into a single system and the high image quality of MRI-guidance may further facilitate the education of personnel and facilitate adaptive RT approaches. In addition, online MR-guidance systems may in the future better respond changing cancer physiology over the treatment, facilitate differential targeting of tumor, lymphatic tissue etc. and offer other added values not yet broadly established (e.g. targeting of atrial fibrillation) or completely identified. Conclusions There is no doubt that the use of advanced imaging on a broad scale is needed. It is a significant clinical problem that a large number of RT devices are still in clinical use without the capability for 3D-imaging and beam gating. As a next step, online MR-image guidance may offer a significant number of benefits over established approaches that may open new roads in radiotherapy.

Robotically assisted long bone biopsy under MRI: cadaver study results.

We have designed and constructed an MR-safe robot made entirely of nonmetallic components with pneumatic actuators and optical encoders. The robot was developed to enable bone biopsies to be performed under magnetic resonance imaging (MRI) guidance in pediatric patients. The purpose of this study was to show the feasibility of using the robot for biopsy of the femur and tibia in a cadaver leg. Our long-term goal is to eliminate radiation exposure during bone biopsy procedures and provide more timely and accurate diagnosis for children with bone cancers and bone infections. The MR-safe robot was mounted on the MRI table. A cadaver leg was procured from an anatomy supply house and placed on the MRI table. All required hospital precautions for infection control were taken. A total of 10 biopsy targets were sampled using MRI guidance: five from the femur and five from the tibia. A handheld, commercially available battery-powered bone drill was used to facilitate drilling through the cortex. After the study, the leg was scanned with CT to better visualize and document the bone biopsy sites. Both the MRI and CT images were used to analyze the results. All of the targets were successfully reached with an average targeting accuracy of 1.43mm. A workflow analysis showed the average time for the first biopsy was 41min including robot setup time and 22min for each additional biopsy including the time for the repeat MRI scan used to confirm accurate targeting. The robot was shown to be MRI transparent, as no image quality degradation due to the use of the robot was detected. The results showed the feasibility of using an MR-safe robotic system to assist the interventional radiologist in performing precision bone biopsy under MRI guidance. Future work will include developing an MR-safe drill, improving the mounting of the robot and fixation of the leg, and moving toward first in child clinical trials.

Applications of Focused Ultrasound in Cerebrovascular Diseases and Brain Tumors.

Oncology and cerebrovascular disease constitute two of the most common diseases afflicting the central nervous system. Standard of treatment of these pathologies is based on multidisciplinary approaches encompassing combination of interventional procedures such as open and endovascular surgeries, drugs (chemotherapies, anti-coagulants, anti-platelet therapies, thrombolytics), and radiation therapies. In this context, therapeutic ultrasound could represent a novel diagnostic/therapeutic in the armamentarium of the surgeon to treat these diseases. Ultrasound relies on mechanical energy to induce numerous physical and biological effects. The application of this technology in neurology has been limited due to the challenges with penetrating the skull, thus limiting a prompt translation as has been seen in treating pathologies in other organs, such as breast and abdomen. Thanks to pivotal adjuncts such as multiconvergent transducers, magnetic resonance imaging (MRI) guidance, MRI thermometry, implantable transducers, and acoustic windows, focused ultrasound (FUS) is ready for prime-time applications in oncology and cerebrovascular neurology. In this review, we analyze the evolution of FUS from the beginning in 1950s to current state-of-the-art. We provide an overall picture of actual and future applications of FUS in oncology and cerebrovascular neurology reporting for each application the principal existing evidences.

Sub-10 nm Cu5FeS4 cube for magnetic resonance imaging-guided photothermal therapy of cancer.

BackgroundFacile synthesis and small size theranostic agents have shown great potential for cancer diagnosis and treatment.PurposeA ternary compound (Cu5FeS4), Fe doped copper sulfide, with novel magnetic properties and strong near-infrared absorption was prepared for magnetic resonance imaging (MRI) imaging guided photothermal therapy of cancer.Patients and methodsFirstly, the capability of magnetic resonance imaging based on the novel magnetic properties and the photothermal performance due to the strong near-infrared absorption was investigated in vitro. Then, the magnetic resonance imaging guided photothermal therapy for 4T1 tumor-bearing mouse was carried out.ResultsThe Cu5FeS4 cube with good T1-weighted MRI, excellent photothermal performance and low cytotoxicity has been investigated. More importantly, the T1-weighted MRI for 4T1 tumor-bearing mouse will get the best contrast effect at tumor site after 8 h of intravenous injection of Cu5FeS4 cube. Under the guidance of the T1-weighted MRI, the PTT was carried out at 8 h after intravenous injection of Cu5FeS4 cube and only the group combined intravenous administration of Cu5FeS4 cube and laser irradiation nearly cured the tumor after 14 days.ConclusionOur study not only provides a new material for personalized treatment of tumors, but also further promotes potential applications of the cancer theranostic agents.

Stereotactic Systems for MRI-Guided Neurosurgeries: A State-of-the-Art Review

Recent technological developments in magnetic resonance imaging (MRI) and stereotactic techniques have significantly improved surgical outcomes. Despite the advantages offered by the conventional MRI-guided stereotactic neurosurgery, the robotic-assisted stereotactic approach has potential to further improve the safety and accuracy of neurosurgeries. This review aims to provide an update on the potential and continued growth of the MRI-guided stereotactic neurosurgical techniques by describing the state of the art in MR conditional stereotactic devices including manual and robotic-assisted. The paper also presents a detailed overview of MRI-guided stereotactic devices, MR conditional actuators and encoders used in MR conditional robotic-assisted stereotactic devices. The review concludes with several research challenges and future perspectives, including actuator and sensor technique, MR image guidance, and robot design issues.

Daily Adaptive Magnetic Resonance Image Guidance Protects the Duodenum from Dose Constraint Violations Associated with Interfraction Stomach Deformation in Stereotactic Body Radiation Therapy for Locally Advanced Pancreatic Cancer

Magnetic Resonance Image guided (MRI-g) radiation therapy provides better soft tissue visualization than cone beam computed tomography (CBCT) and allows for daily online adaptive radiotherapy (OART) in the treatment of locally advanced pancreatic cancer (LAPC). Using MRI-g stereotactic body radiation therapy (SBRT) to treat LAPC, we hypothesized that stomach distention would correlate with dose increases to organs-at-risk (OARs) when online adaptation was not utilized. Meanwhile, we hypothesized that OART would protect against dose constraint violations to OARs. We identified ten patients who received pancreas SBRT to a dose of 33-40 Gy in 5 fractions. The patients were instructed to avoid oral intake other than sips of water for at least 3 hours prior to treatment. Dose was prescribed to achieve 90% coverage of planning tumor volume at 100% isodose (PTV100). After each fraction’s setup MRI, the target position was aligned by 3-dimensional shifts, the normal anatomy was re-contoured, and the original radiotherapy plan was recalculated to make a non-adaptive plan. A re-optimized (adaptive) plan was then generated for each fraction and renormalized to 90% coverage of PTV100. Target and OAR doses between non-adaptive and adaptive plans were compared by paired t-test and McNemar tests to assess the dosimetric impact of daily adaptation. A linear random-coefficient model correlated changes in stomach volumes to changes in OAR objective doses. Sixty-eight percent of non-adaptive fractions met both point maxima and V33 dose constraints to the duodenum compared with 87% of adaptive fractions (p=0.0013). The original stomach volume (OSV) mean was 286 cc, with a range from 126cc-856cc. The mean interfraction change from the OSV was +147cc, with a range from -404cc to +1,271 cc. The mean percentage change from the OSV was 53%, with a range from -47% to 334%. For non-adaptive plans, interfraction increase in stomach volume correlated with higher duodenum V33 (p=0.021), duodenum maximum dose (p=0.105), stomach V33 (p=0.004), and stomach maximum dose (p=0.009). No correlation was observed between stomach volume and dose to visceral OARs for the adaptive plans. In SBRT for LAPC, interfraction variations in stomach volume occur despite precautions and correlate with increased dose to the duodenum in non-adaptive plans, leading to significant dose constraint violations. OART limits dose to the duodenum and contributes to safe SBRT dose escalation.Abstract SU_20_2197; Table 1Analysis of OAR constraint violations for non-adaptive (NA) and adaptive (A) plansBoth NA and A meet OAR constraints, n (%)Only NA meets constraints, n (%)Only A meets constraints, n (%)Neither NA nor A meets constraints, n (%)p-valueDuodenumDmax < 38 Gy28 (56)4 (8)15 (30)3 (6)0.019V33 < 1 cc32 (64)4 (8)12 (24)2 (4)0.077StomachDmax < 38 Gy40 (80)3 (6)4 (8)3 (6)1V33 < 1 cc37 (74)3 (6)5 (10)5 (10)0.727BowelDmax < 38 Gy44 (88)5 (10)1 (2)0 (0)0.219All OAR constraints met14 (28)9 (18)15 (30)12 (24)0.221 Open table in a new tab

Body-Mounted Robot for Image-Guided Percutaneous Interventions: Mechanical Design and Preliminary Accuracy Evaluation.

This paper presents a body-mounted, four degree-of-freedom (4-DOF) parallel mechanism robot for image-guided percutaneous interventions. The design of the robot is optimized to be light weight and compact such that it could be mounted to the patient body. It has a modular design that can be adopted for assisting various image-guided, needle-based percutaneous interventions such as arthrography, biopsy and brachytherapy seed placement. The robot mechanism and the control system are designed and manufactured with components compatible with imaging modalities including Magnetic Resonance Imaging (MRI) and Computed Tomography (CT). The current version of the robot presented in this paper is optimized for shoulder arthrography under MRI guidance; a Z-shaped fiducial frame is attached to the robot, providing accurate and repeatable robot registration with the MR scanner coordinate system. Here we present the mechanical design of the manipulator, robot kinematics, robot calibration procedure, and preliminary bench-top accuracy assessment. The bench-top accuracy evaluation of the robotic manipulator shows average translational error of 1.01 mm and 0.96 mm in X and Z axes, respectively, and average rotational error of 3.06 degrees and 2.07 degrees about the X and Z axes, respectively.

Adaptive Radiotherapy Enabled by MRI Guidance

Adaptive radiotherapy (ART) strategies systematically monitor variations in target and neighbouring structures to inform treatment-plan modification during radiotherapy. This is necessary because a single plan designed before treatment is insufficient to capture the actual dose delivered to the target and adjacent critical structures during the course of radiotherapy. Magnetic resonance imaging (MRI) provides superior soft-tissue image contrast over current standard X-ray-based technologies without additional radiation exposure. With integrated MRI and radiotherapy platforms permitting motion monitoring during treatment delivery, it is possible that adaption can be informed by real-time anatomical imaging. This allows greater treatment accuracy in terms of dose delivered to target with smaller, individualised treatment margins. The use of functional MRI sequences would permit ART to be informed by imaging biomarkers, so allowing both personalised geometric and biological adaption. In this review, we discuss ART solutions enabled by MRI guidance and its potential gains for our patients across tumour types.

MR Thermography-Guided Head and Neck Lesion Laser Ablation.

Interstitial laser ablation has been successfully used as a minimally invasive treatment option for tumors in many parts of the body, including the head and neck. In this article, we describe the use of MR imaging guidance and mapping sequences for accurate localization of the target lesion, percutaneous interstitial laser ablation methods, and the use of MR thermography for temperature monitoring during laser ablation, with a focus on applications in the head and neck region.

Simultaneously activating highly selective ratiometric MRI and synergistic therapy in response to intratumoral oxidability and acidity

Low selectivity is a major problem for cancer theranostics that has promoted the development of molecularly-responsive nanomaterials. Herein, we report a novel doxorubicin (DOX)-loaded degradable cobalt oxide nanoprism (Co3O4-DOX) for T1/T2 ratiometric magnetic resonance imaging (MRI)-monitored synergistic cancer therapy that simultaneously responds to intratumoral oxidability and acidity. Co3O4-DOX degraded under both H2O2-rich and acidic conditions, producing Co3+ and releasing DOX, not only resulted in an MRI contrast switch from T2 to T1, but also led to DOX luminescence recovery by weakening energy transfer. Thus, highly sensitive and selective H2O2 detection was achieved by these changes in MRI and luminescence signals. Importantly, Co3O4-DOX showed outstanding T1/T2 ratiometric MRI performance in vivo, significantly improving the contrast between tumor and normal tissues. Moreover, the produced Co3+ also resulted in intracellular radical generation for chemodynamic therapy, which had a synergistic effect with the photothermal and chemotherapy induced by Co3O4 and DOX, respectively. Under ratiometric MRI guidance, successful synergistic cancer therapy was performed on a tumor-bearing mice model. This work provides a new imaging application to improve selectivity that uses molecularly-responsive magnetic nanomaterials for ratiometric MRI tumor imaging and cancer theranostics.

Anaesthesia in the MRI suite

Anaesthesia in the magnetic resonance imaging (MRI) suite, or when performing surgery that requires MRI guidance, is becoming a more frequent and complex procedure for anaesthetists, as the study m...

Beyond transrectal ultrasound-guided prostate biopsies: available techniques and approaches.

Recent advances have led to the use of magnetic resonance imaging (MRI) alone or with fusion to transrectal ultrasound (TRUS) images for guiding biopsy of the prostate. Our group sought to develop consensus recommendations regarding MRI-guided prostate biopsy based on currently available literature and expert opinion. The published literature on the subject of MRI-guided prostate biopsy was reviewed using standard search terms and synthesized and analyzed by four different subgroups from among the authors. The literature was grouped into four categories-MRI-guided biopsy platforms, robotic MRI-TRUS fusion biopsy, template mapping biopsy and transrectal MRI-TRUS fusion biopsy. Consensus recommendations were developed using the Oxford Center for Evidence Based Medicine criteria. There is limited high level evidence available on the subject of MRI-guided prostate biopsy. MRI guidance with or without TRUS fusion can lead to fewer unnecessary biopsies, help identify high-risk (Gleason ≥ 3 + 4) cancers that might have been missed on standard TRUS biopsy and identify cancers in the anterior prostate. There is no apparent significant difference between MRI biopsy platforms. Template mapping biopsy is perhaps the most accurate method of assessing volume and grade of tumor but is accompanied by higher incidence of side effects compared to TRUS biopsy. Magnetic resonance imaging-guided biopsies are feasible and better than traditional ultrasound-guided biopsies for detecting high-risk prostate cancer and anterior lesions. Judicious use of MRI-guided biopsy could enhance diagnosis of clinically significant prostate cancer while limiting diagnosis of insignificant cancer.

Exact Placement of Spinal Cord Stem Cells with Magnetic Resonance Imaging Guidance: Seeing Is Believing

Exact Placement of Spinal Cord Stem Cells with Magnetic Resonance Imaging Guidance: Seeing Is Believing