Magnetic Resonance-guided Focused Ultrasound Surgery Research Articles

Transducer module apodization to reduce bone heating during focused ultrasound uterine fibroid ablation with phased arrays: A numerical study.

During magnetic resonance-guided focused ultrasound (MRgFUS) surgery for uterine fibroids, ablation of fibrous tissues in proximity to the hips and spine is challenging due to heating within the bone that can cause patients to experience pain and potentially damage nerves. This far-field bone heating limits the volume of fibroid tissue that is treatable viaMRgFUS. To investigate transducer module apodization for improving the ratio of focal-to-bone heating ( ) when targeting fibroid tissue close to the hips and spine, to enable MRgFUS treatments closer to thebone. Acoustic and thermal simulations were performed using 3D magnetic resonance imaging (MRI)-derived anatomies of ten patients who underwent MRgFUS ablation for uterine fibroids using a low-frequency ( ) 6144-element flat fully-populated modular phased array system (Arrayus Technologies Inc., Burlington, Canada) at our institution as part of a larger clinical trial (NCT03323905). Transducer modules ( per module) whose beams intersected with no-pass zones delineated within the field were identified, their output power levels were reduced by varying blocking percentage levels, and the resulting temperature field distributions were evaluated across multiple sonications near the hip and spine bones in each patient. Acoustic and thermal simulations took approximately ( ) and ( ) to run for a single near-spine (near-hip) target,respectively. For all simulated sonications, transducer module blocking improved compared to the no blocking case. In just over half of sonications, full module blocking maximized (increase of 82% 38% in 50% of hip targets and 49% 30% in 62% of spine targets vs. no blocking; mean±SD), at the cost of more diffuse focusing (focal heating volumes increased by 13%±13% for hip targets and 39%±27% for spine targets) and thus requiring elevated total (hip: 6%±17%, spine: 37%±17%) and peak module-wise (hip: 65%±36%, spine: 101%±56%) acoustic power levels to achieve equivalent focal heating as the no blocking control case. In the remaining sonications, partial module blocking provided further improvements in both (increased by 29%±25% in the hip and 15%±12% in the spine) and focal heating volume (decrease of 20%±10% in the hip and 34%±17% in the spine) relative to the full blocking case. The optimal blocking percentage value was dependent on the specific patient geometry and target location of interest. Although not all individual target locations saw the benefit, element-wise phase aberration corrections improved the average compared to the no correction case (increase of 52%±47% in the hip, 35%±24% in the spine) and impacted the optimal blocking percentage value. Transducer module blocking enabled ablative treatments to be carried out closer to both hip and spine without overheating or damaging the bone (no blocking: / , full blocking: / , optimal partial blocking: / for hip/spine). The proposed transducer apodization scheme shows promise for improving MRgFUS treatments of uterine fibroids, and may ultimately increase the effective treatment envelope of MRgFUS surgery in the body by enabling tissue ablation closer to bonystructures.

Predicting tremor improvement after MRgFUS thalamotomy in essential tremor from preoperative spontaneous brain activity: A machine learning approach

Magnetic resonance-guided focused ultrasound surgery (MRgFUS) thalamotomy is an emerging technique for medication-refractory essential tremor (ET), but with variable outcomes. This study used pattern regression analysis to identify brain signatures predictive of tremor improvements. Fifty-four ET patients (mean age = 63.06 years, standard deviation (SD) = 10.55 years, 38 males) underwent unilateral MRgFUS thalamotomy and were scanned for resting-state functional magnetic resonance imaging (rs-fMRI). Seventy-four healthy controls (mean age = 58.09 years, SD = 10.30 years, 38 males) were recruited for comparison. Tremor responses at 12 months posttreatment were evaluated by the Clinical Rating Scale for Tremor. The fractional amplitude of low-frequency fluctuations (fALFF) was calculated from rs-fMRI data. Two-sample t-test was used to generate a disease-specific mask, within which Multivariate Kernel Ridge Regression analyses were conducted. Predicted and actual clinical scores were compared using Pearson’s correlation coefficient (r) and normalized mean squared error (Norm. MSE). Permutation test and leave-one-out strategy were applied for results validation. KRR identified fALFF patterns that significantly predicted the hand tremor improvement (r = 0.23, P = 0.025; Norm. MSE = 0.05, P = 0.026) and the postural tremor improvement (r = 0.28, P = 0.025; Norm. MSE = 0.06, P = 0.023), but not action tremor improvement. Lobule VI of right cerebellum (Cerebelum_6_R), right superior occipital gyrus (Occipital_Sup_R) and lobule X of vermis (Vermis_10) contributed most for hand tremor prediction (normalized weights (NW): 2.77%, 2.40%, 2.34%) while Vermis_10, left supplementary motor area (Supp_Motor_Area_L) and right hippocampus (Hippocampus_R) for postural tremor prediction (NW: 2.69%, 2.12%, 2.05%). The low contributing NW of the individual brain regions suggested that the fALFF pattern as a whole is an overall predicting feature. Preoperative fALFF pattern predicts tremor benefits induced by MRgFUS thalamotomy. ClinicalTrials.gov number: NCT04570046.

Early re-emerging tremor after MRgFUS thalamotomy: case-control analysis of procedural and imaging features.

This study aimed to identify possible prognostic factors determining early tremor relapse after Magnetic Resonance guided Focused Ultrasound Surgery (MRgFUS) thalamotomy in patients with essential tremor (ET) and Parkinson's disease (PD). Nine patients (six ET and three PD) who underwent Vim MRgFUS thalamotomy in a single institution and developed early re-emergent tremor were analyzed. A control group of patients matched pairwise for sex, pathology, age, disease duration, and skull density ratio (SDR) was selected to compare the technical-procedural data and MR imaging evidence. MR imaging findings compared between groups included lesion shape and volume in multiparametric sequences, as well as Fractiona Anisotropy (FA) and Apparent Diffusion Coefficient (ADC) values derived from Diffusion Tensor Imaging Diffusion Weighted Imaging (DTI) and Diffusion Weighted Imaging (DWI) sequences. We did not find statistically significant differences in gender and age between the two groups. Technical and procedural parameters were also similar in both treatment groups. In MRI analysis, we found lesions of similar size but with greater caudal extension in the control group with stable outcomes compared to patients with tremor relapse. In our analysis of early recurrences after thalamotomy with focused ultrasound, there were neither technical and procedural differences nor prognostic factors related to lesion size or ablation temperatures. Greater caudal extension of the lesion in patients without recurrence might suggest the importance of spatial consolidation during treatment.

Protective effect of remote ischemic preconditioning on blood pressure control in magnetic resonance-guided focused ultrasound operations

Backrgound. Magnetic resonance-guided focused ultrasound (MR-FUS) is a new non-invasive technology for the surgical treatment of extrapyramidal movement disorders for such pathologies as essential tremor, Parkinson’s disease, etc. In these cases, the brain is injured and a zone of ischemia is formed. Arterial hypertension (AH) is one of the most common pathologies, which is often accompanied by neurological diseases. Objective. To investigate the effect of the remote ischemic preconditioning (RIPC) on blood pressure (BP) during MR-FUS surgery. Design – blinded, randomized, controlled, 2-group study with sham preconditioning. Materials and Methods. Patients were randomized into the RIPC group (cuff systolic BP (SBP) >50 mmHg, n=42) and the group with sham RIPC (cuff diastolic BP (DBP), n=39) before surgery in regime 3 cycles each 5 min with 5 min rest between cycles. Results. While there was a decrease in SBP and DBP before and after the operation in the RIPC group, there was an increase (p<0.001) in the sham RIPC group. Using the Difference-in-Difference equation for SBP, SBP was 8.9 (5.9–11.9) mm Hg higher in the sham RIPC group than in the RIPC group (p<0.01). Conclusion. As a result, MR-FUS operations showed a significant decrease in BP during RIPC compared to the imitation, which confirms the angioprotective effect of preconditioning.

Uterine Leiomyomas and Infertility: A Comparison of National and International Guidelines.

Uterine leiomyomas are the most common benign tumors of the female genital track, causing various symptoms and problems, including a possible impact on fertility.The relationship between fibroids and infertility has long been a debate among gynecologists. Management of fibroids in women with otherwise unexplained infertility worldwide lacks standardized, evidence-based guidelines. Therefore, a review of guidelines from the Royal Australian and New Zealand College of Obstetricians and Gynecologists, the American College of Obstetricians and Gynecologists, the Society of Obstetricians and Gynecologists of Canada, the Collège National des Gynécologues et Obstétriciens Français, and the American Society of Reproductive Medicine was conducted. There is agreement among all guidelines that the effect of fibroids on fertility is related to their position in the uterus and the alteration of the endometrial cavity. However, whether surgical intervention (laparotomy, laparoscopy, or hysteroscopy) is required varies among committees. More specifically, for submucous myomas, all guidelines agree that surgical intervention is needed. On the other hand, regarding intramural myomas, there is no consensus on what the approach may be. Novel treatments such as uterine artery embolization (UAE) and magnetic resonance-guided focused ultrasound surgery (MRgFUS) should only be used in clinical trial settings. Nevertheless, all guidelines agree that medical management of fibroids further delays efforts to conceive and has no role as a stand-alone treatment of fibroids; though, the use of GnRH analogues preoperatively can be useful to improve anemia and/or reduce fibroid volume. There is a need for updated international protocols to be introduced, in order to help clinicians dealing with fibroids and infertility to better suggest the optimal treatment.

PH-Responsive doxorubicin-loaded magnetosomes for magnetic resonance-guided focused ultrasound real-time monitoring and ablation of breast cancer.

MR-guided focused ultrasound surgery (MRgFUS) is driving a new direction in non-invasive thermal ablation therapy with spatial specificity and real-time temperature monitoring. Although widely used in clinical practice, it remains challenging to completely ablate the tumor margin due to fear of damaging the surrounding tissues, thus leading to low efficacy and a series of complications. Herein, we have developed novel pH-responsive drug-loading magnetosomes (STPSD nanoplatform) for increasing the T2-contrast and improved the ablation efficiency with a clinical MRgFUS system. Specifically, this STPSD nanoplatform is functionalized by pH-responsive peptides (STP-TPE), encapsulating superparamagnetic iron oxide (SPIO) and doxorubicin (DOX), which can cause drug release and SPIO deposition at the tumor site triggered by acidity and MRgFUS. Under MRgFUS treatment, the increased vascular permeability caused by hyperthermia can improve the uptake of SPIO and DOX by tumor cells, so as to enhance ultrasound energy absorption and further enhance the efficacy of chemotherapy to completely ablate tumor margins. Moreover, we demonstrated that a series of MR sequences including T2-weighted imaging (T2WI), contrast-enhanced T1WI imaging (T1WI C+), maximum intensity projection (MIP), volume rendering (VR) and ADC mapping can be further utilized to monitor the MRgFUS ablation effect in rat models. Overall, this smart nanoplatform has the capacity to be a powerful tool to promote the therapeutic MRgFUS effect and minimize the side effects to surrounding tissues.

Cytoreductive Surgical Treatment of Pleural Mesothelioma in a Porcine Model Using Magnetic-Resonance-Guided Focused Ultrasound Surgery (MRgFUS) and Radiofrequency Ablation (RFA)

A combination of surgery and chemotherapy is the most effective treatment available for Malignant Pleural Mesothelioma (MPM). However, both cause significant collateral damage and cannot eliminate residual microscopic disease. This investigation aimed to compare and determine the feasibility of utilizing Radiofrequency Ablation (RFA) and Magnetic-Resonance-guided Focused Ultrasound Surgery (MRgFUS) as alternative treatments for MPM. A large animal tumor model was developed in 13 Yorkshire female pigs using the MSTO211H cell line. Two pigs were initially used to determine the cyclosporine dose required for immunosuppression and tumor development. Subsequently, 11 other pigs underwent tumor development. Of these 11, 2 died during cell inoculation. Small tumor masses and adhesions were present in the other 9, indicating mesothelioma development. Five pigs then received RFA treatment, and 4 pigs received MRgFUS treatment. Tumor model development and effect of the two treatments were examined using MRI and by necropsy. RFA and MRgFUS both successfully ablated approximately the same sized area in the same treatment time. This study demonstrates that RFA and MRgFUS are feasible for tumor debulking, and while MRgFUS requires more pretreatment planning compared to RFA, MRgFUS is a completely noninvasive procedure.

Essential Tremor That is Difficult to Improve with Standard Medical Treatment-Suppression: Surgical Treatment of Tremor

Drug-refractory essential tremors, especially those in the upper extremities, may benefit from surgical treatment. Currently, three main treatment methods are available: deep brain stimulation (DBS), radiofrequency coagulation (RF), and magnetic resonance -guided focused ultrasound surgery (MRgFUS). DBS is a device-based therapy, and its effects are reversible, whereas RF and FUS create irreversible coagulation lesions. DBS and RF require the direct puncturing of the target, whereas FUS focuses ultrasound from extracranial sources. The primary target is the ventralis intermedius of the thalamus (Vim); however, the posterior subthalamic area (PSA) is also reportedly an effective target site. In this article, we will summarize the features of the three treatments for essential tremors, and discuss the treatment strategies and methods for each symptom.

Comparison of computer simulations and clinical treatment results of magnetic resonance-guided focused ultrasound surgery (MRgFUS) of uterine fibroids.

PurposeMagnetic resonance‐guided focused ultrasound surgery (MRgFUS) can be used to noninvasively treat symptomatic uterine fibroids by heating with focused ultrasound sonications while monitoring the temperature with magnetic resonance (MR) thermometry. While prior studies have compared focused ultrasound simulations to clinical results, studies involving uterine fibroids remain scarce. In our study, we perform such a comparison to assess the suitability of simulations for treatment planning.MethodsSonications (N = 67) were simulated retrospectively using acoustic and thermal models based on the Rayleigh integral and Pennes bioheat equation followed by MR‐thermometry simulation in seven patients who underwent MRgFUS treatment for uterine fibroids. The spatial accuracy of simulated focus location was assessed by evaluating displacements of the centers of mass of the thermal dose distributions between simulated and treatment MR thermometry slices. Temperature–time curves and sizes of 240 equivalent minutes at 43°C (240EM43) volumes between treatment and simulation were compared.ResultsThe simulated focus location showed errors of 2.7 ± 4.1, −0.7 ± 2.0, and 1.3 ± 1.2 mm (mean ± SD) in the anterior–posterior, foot–head, and right–left directions for a fibroid absorption coefficient of 4.9 Np m–1 MHz–1 and perfusion parameter of 1.89 kg m–3 s–1. Linear regression of 240EM43 volumes of 67 sonications of patient treatments and simulations utilizing these parameters yielded a slope of 1.04 and a correlation coefficient of 0.54. The temperature rise ratio of simulation to treatment near the end of sonication was 0.47 ± 0.22, 1.28 ± 0.60, and 1.49 ± 0.71 for 66 sonications simulated utilizing fibroid absorption coefficient of 1.2, 4.9, and 8.6 Np m–1 MHz–1, respectively, and the aforementioned perfusion value. The impact of perfusion on peak temperature rise is minimal between 1.89 and 10 kg m–3 s–1, but became more substantial when utilizing a value of 100 kg m–3 s–1.ConclusionsThe results of this study suggest that perfusion, while in some cases having a substantial impact on thermal dose volumes, has less impact than ultrasound absorption for predicting peak temperature elevation at least when using perfusion parameter values up to 10 kg m–3 s–1 for this particular array geometry, frequencies, and tissue target which is good for clinicians to be aware of. The results suggest that simulations show promise in treatment planning, particularly in terms of spatial accuracy. However, in order to use simulations to predict temperature rise due to a sonication, knowledge of the patient‐specific tissue parameters, in particular the absorption coefficient is important. Currently, spatially varying patient‐specific tissue parameter values are not available during treatment, so simulations can only be used for planning purposes to estimate sonication performance on average.

A Few-Shot Learning Approach Assists in the Prognosis Prediction of Magnetic Resonance-Guided Focused Ultrasound for the Local Control of Bone Metastatic Lesions.

Simple SummaryWe report a local control prediction model for patients undergoing MRgFUS ablation, and provide promising guidance for clinicians to identify a suitable treatment strategy for bone metastatic lesions. We propose a few-shot learning approach to establish the quick prediction of clinical and radiographic responses. On the basis of demographic data, pre-/post-treatment immune-related cytokine change, and MRI imaging, the most suitable parameters were selected to assess potential treatment outcomes during the acute inflammatory stages within 24 h. Traditional logistic regression and few-shot learning models were compared to identify the best model on an independent test. The best predictive few-shot learning model (accuracy of 85.2%, sensitivity of 88.6%, and AUC of 0.95) was achieved by combining the clinical features with the levels of significant cytokines IL-6, IL-13, IP-10, and eotaxin.Magnetic resonance-guided focused ultrasound surgery (MRgFUS) constitutes a noninvasive treatment strategy to ablate deep-seated bone metastases. However, limited evidence suggests that, although cytokines are influenced by thermal necrosis, there is still no cytokine threshold for clinical responses. A prediction model to approximate the postablation immune status on the basis of circulating cytokine activation is thus needed. IL-6 and IP-10, which are proinflammatory cytokines, decreased significantly during the acute phase. Wound-healing cytokines such as VEGF and PDGF increased after ablation, but the increase was not statistically significant. In this phase, IL-6, IL-13, IP-10, and eotaxin expression levels diminished the ongoing inflammatory progression in the treated sites. These cytokine changes also correlated with the response rate of primary tumor control after acute periods. The few-shot learning algorithm was applied to test the correlation between cytokine levels and local control (p = 0.036). The best-fitted model included IL-6, IL-13, IP-10, and eotaxin as cytokine parameters from the few-shot selection, and had an accuracy of 85.2%, sensitivity of 88.6%, and AUC of 0.95. The acceptable usage of this model may help predict the acute-phase prognosis of a patient with painful bone metastasis who underwent local MRgFUS. The application of machine learning in bone metastasis is equivalent or better than the current logistic regression.

Characterization of a Low-Profile, Flexible, and Acoustically Transparent Receive-Only MRI Coil Array for High Sensitivity MR-Guided Focused Ultrasound.

Magnetic resonance guided focused ultrasound (MRgFUS) is a non-invasive therapeutic modality for neurodegenerative diseases that employs real-time imaging and thermometry monitoring of targeted regions. MRI is used in guidance of ultrasound treatment; however, the MR image quality in current clinical applications is poor when using the vendor built-in body coil. We present an 8-channel, ultra-thin, flexible, and acoustically transparent receive-only head coil design (FUS-Flex) to improve the signal-to-noise ratio (SNR) and thus the quality of MR images during MRgFUS procedures. Acoustic simulations/experiments exhibit transparency of the FUS-Flex coil as high as 97% at 650 kHz. Electromagnetic simulations show a SNR increase of 13× over the body coil. In vivo results show an increase of the SNR over the body coil by a factor of 7.3 with 2× acceleration (equivalent to 11× without acceleration) in the brain of a healthy volunteer, which agrees well with simulation. These preliminary results show that the use of a FUS-Flex coil in MRgFUS surgery can increase MR image quality, which could yield improved focal precision, real-time intraprocedural anatomical imaging, and real-time 3D thermometry mapping.

A “user-friendly” phantom to conduct Quality Controls on MRgFUS device

Magnetic Resonance guided Focused Ultrasound Surgery (MRgFUS) is a hybrid technique which uses Magnetic Resonance (MR) to obtain morphological information of the examined anatomical district and Focused Ultrasound Surgery (FUS) to ablate the body region under investigation by using MR as guidance. To ensure patients’ safety is necessary to establish periodic Quality Controls (QCs) providing a complete evaluation of system status. QCs cannot be done directly on patients, for this reason, dedicated phantoms are used to guarantee the maintenance of quality over equipment lifetime. Several phantoms are available on the market, which are distributed by manufacturers and specific to the medical equipment, resulting in closed systems. In this study, we idealized, developed and created a prototype of a completely “;user-friendly”; phantom, to conduct QCs on FUS devices. It consists of an empty cylinder of polymethylmetacrylate (PMMA), that can be filled with different fluids and various inserts, available for the Medical Physicists, to perform test measurements on different parameters (size of FUS spot, precision of FUS spot, linearity of FUS power, linearity of electric power, evaluation of target temperature). The obtained results demonstrated that the novel phantom represents a useful and adaptable device that could be used during FUS QCs evaluations.

Weakening or Structural Strengthening? An Evaluation of Bone Density after MRgFUS Ablation for Treatment of Benign Bone Lesions.

Previous studies suggest that interventional ablative procedures on bone lesions may weaken the bone, especially when performed through the needle approach. Our purpose was to evaluate, through Computed Tomography (CT), the effects of Magnetic Resonance guided Focused Ultrasound Surgery (MRgFUS) ablation on painful osteoid osteomas and osteoblastomas in terms of bone density and morphological changes. We retrospectively evaluated patients treated at our institution with MRgFUS for superficial, painful osteoid osteoma or osteoblastoma during the last 9 years. Inclusion criteria were procedural and clinical success, as well as the availability of pre- and postprocedural CT examinations. Imaging features assessed were perilesional/nidus density changes and the occurrence of pathological fractures during the follow-up period. Our study population included 31 osteoid osteomas and 5 intra-articular osteoblastomas in 36 treated patients. We found an increased bone density of the lesions when pre and post-treatment CT- values were compared: these differences were statistically significant, and this finding is consistent with significant bone densification at the post-treatment imaging follow-up. No pathological fractures were observed after ablation during the follow-up. MRgFUS can be considered to be the treatment of choice for benign superficial bone lesions, thanks to its minimal invasiveness, excellent effectiveness, and safety. Pathological fractures, reported in literature as a rare event using needle ablation, never occurred in our MRgFUS treatment series.

Needleless Ablation of Osteoid Osteoma and Osteoblastoma: The Emergent Role of MRgFUS.

Osteoblastoma (OB) and osteoid osteoma (OO) are benign bone-forming tumors, with nearly identical basic microscopic features. The main difference is dimension (OO has usually a nidus measuring <2 cm in diameter). In addition, OB is biologically more active than OO, with a tendency to grow in size. Historically, treatments have included surgical resection and analgesics, although invasiveness and poor tolerance have led to the current standard of care moving toward interventional radiology, where radiofrequency ablation (RFA) represents the most diffuse technique. Magnetic resonance-guided focused ultrasound surgery (MRgFUS) has recently emerged as another innovative alternative treatment, providing tumor ablation through a needleless and ionizing radiation-free modality. In addition, this technique has the ability to guarantee a very precise and controlled increase in temperature, delivering small amounts of energy that can accurately destroy only the lesion, avoiding healthy surrounding tissues. The present review focuses on MRgFUS as the less invasive, safe, effective, and durable treatment option for the management of osteoid osteoma and osteoblastoma, including a description of technical details, indications and outcomes.

Effect of MRgFUS treatment on cortical activity in Parkinson's disease: a fNIRS study

n this paper, a new combined approach, based on Magnetic Resonance-guided Focused Ultrasound Surgery (MRgFUS) technique and functional Near Infrared Spectroscopy (fNIRS), was applied for treatment and monitoring of patients affected by bilateral Parkinson’s disease (PD). On one side, MRgFUS enables non-invasive thalamotomy by combining FUS for tissue ablation and MR for targeting and monitoring. On the other side, fNIRS allows to monitor, non-invasively and without strict motion restriction even in a daily life environment, cortical neural activity related dynamics of both oxygenated and deoxygenated haemoglobin (HbO and HbR, respectively). In particular, the changes of cortical activation pattern in PD patients, with respect to age matched healthy control subjects, were analysed, while performing left and right hand finger tapping (LFT and RFT, respectively), before MRgFUS treatment, and at two different time intervals after the treatment. By comparison with the pre-treatment session, significant activations were predominantly observed one week after the treatment, with patterns recalling those of control group, and partially lost one month later, likely because of the neurodegenerative nature of PD. In addition, activations were more marked for LFT task, being the treatment performed on the right hemisphere. These results appear promising in view of the application of fNIRS for neurorehabilitation, especially in those clinical settings where traditional neuroimaging techniques cannot be applied.

Percutaneous management of bone metastases: State of the art

Interventional radiology is playing an increasingly important role in the local treatment of bone metastases; this treatment is usually done with palliative intent, although in selected patients it can be done with curative intent. Two main groups of techniques are available.The first group, centered on bone consolidation, includes osteoplasty/vertebroplasty, in which polymethyl methacrylate (PMMA) is injected to reinforce the bone and relieve pain, and percutaneous osteosynthesis, in which fractures with nondisplaced or minimally bone fragments are fixed in place with screws. The second group centers on tumor ablation. tumor ablation refers to the destruction of tumor tissue by the instillation of alcohol or by other means. Thermoablation is the preferred technique in musculoskeletal tumors because it allows for greater control of ablation. Thermoablation can be done with radiofrequency, in which the application of a high frequency (450 Hz–600 Hz) alternating wave to the tumor-bone interface achieves high temperatures, resulting in coagulative necrosis. Another thermoablation technique uses microwaves, applying electromagnetic waves in an approximate range of 900 MHz–2450 MHz through an antenna that is placed directly in the core of the tumor, stimulating the movement of molecules to generate heat and thus resulting in coagulative necrosis. Cryoablation destroys tumor tissue by applying extreme cold. A more recent, noninvasive technique, magnetic resonance-guided focused ultrasound surgery (MRgFUS), focuses an ultrasound beam from a transducer placed on the patient's skin on the target lesion, where the waves’ mechanical energy is converted into thermal energy (65 °C–85 °C). Treatment should be planned by a multidisciplinary team. Treatment can be done with curative or palliative intent. Once the patient is selected, a preprocedural workup should be done to determine the most appropriate technique based on a series of factors. During the procedure, protective measures must be taken and the patient must be closely monitored. After the procedure, patients must be followed up.

Magnetic Resonance-Guided Focused Ultrasound Surgery for Obsessive-Compulsive Disorders: Potential for use as a Novel Ablative Surgical Technique.

Surgical treatment for psychiatric disorders, such as obsessive-compulsive disorder (OCD) and depression, using ablative techniques, such as cingulotomy and capsulotomy, have historically been controversial for a number of scientific, social, and ethical reasons. Recently, with the elucidation of anatomical and neurochemical substrates of brain function in healthy controls and patients with such disorders using various functional neuroimaging techniques, these criticisms are becoming less valid. Furthermore, by using new techniques, such as deep brain stimulation (DBS), and identifying more precise targets, beneficial effects and the lack of serious complications have been demonstrated in patients with psychiatric disorders. However, DBS also has many disadvantages. Currently, magnetic resonance-guided focused ultrasound surgery (MRgFUS) is used as a minimal-invasive surgical method for generating precisely placed focal thermal lesions in the brain. Here, we review surgical techniques and their potential complications, along with anterior limb of the internal capsule (ALIC) capsulotomy by radiofrequency lesioning and gamma knife radiosurgery, for the treatment of OCD and depression. We also discuss the limitations and technical issues related to ALIC capsulotomy with MRgFUS for medically refractory OCD and depression. Through this review we hope MRgFUS could be considered as a new treatment choice for refractory OCD.

Manejo percutáneo de las metástasis óseas

Interventional radiology is playing an increasingly important role in the local treatment of bone metastases; this treatment is usually done with palliative intent, although in selected patients it can be done with curative intent. Two main groups of techniques are available.The first group, centered on bone consolidation, includes osteoplasty / vertebroplasty, in which polymethyl methacrylate (PMMA) is injected to reinforce the bone and relieve pain, and percutaneous osteosynthesis, in which fractures with nondisplaced or minimally bone fragments are fixed in place with screws. The second group centers on tumor ablation. Tumor ablation refers to the destruction of tumor tissue by the instillation of alcohol or by other means. Thermoablation is the preferred technique in musculoskeletal tumors because it allows for greater control of ablation. Thermoablation can be done with radiofrequency, in which the application of a high frequency (450 Hz–600Hz) alternating wave to the tumor-bone interface achieves high temperatures, resulting in coagulative necrosis. Another thermoablation technique uses microwaves, applying electromagnetic waves in an approximate range of 900MHz to 2450MHz through an antenna that is placed directly in the core of the tumor, stimulating the movement of molecules to generate heat and thus resulting in coagulative necrosis. Cryoablation destroys tumor tissue by applying extreme cold. A more recent, noninvasive technique, magnetic resonance-guided focused ultrasound surgery (MRgFUS), focuses an ultrasound beam from a transducer placed on the patient's skin on the target lesion, where the waves’ mechanical energy is converted into thermal energy (65°C–85°C). Treatment should be planned by a multidisciplinary team. Treatment can be done with curative or palliative intent. Once the patient is selected, a preprocedural workup should be done to determine the most appropriate technique based on a series of factors. During the procedure, protective measures must be taken and the patient must be closely monitored. After the procedure, patients must be followed up.

Magnetic resonance-guided focused Ultrasound surgery for treatment of osteoid osteoma: How do we do it?

Magnetic Resonance-guided Focused Ultrasound Surgery (MRgFUS) is an increasingly popular non-invasive technique for treatment of severe pain produced by soft tissue, solid or bone tumours. MRgFUS used targeted thermal ablation technique to control moderate to severe pain.&#x0D; Osteoid osteoma is a small benign, highly vascular tumour, composed of osteoid and woven bone, most commonly affect the appendicular skeleton. Bony spine involvement can produce painful scoliosis, while intra-articular joint involvement can cause irreversible joint damage. Clinical presentation is local bone pain which typically worsen at night and with increased activity.&#x0D; Conventional standard treatment of osteoid osteoma is analgesic or surgical intervention. Under conservative medical treatment, the patient needs to be on long term analgesic, e.g. salicylates, where well-known reported complications include renal tubular acidosis and gastric ulcer. The standard surgical treatment is curettage. However, this carry the risk of bleeding, infection and tissue damage. Minimally invasive radiofrequency ablation (RFA) or cryoablation which are the current treatment of choice also carry the risk of tumour rupture and bleeding. We present a case of severe bone pain from benign bone tumor (osteoid osteoma), successfully treated with noninvasive Magnetic MRgFUS.

A Computational Study on Temperature Variations in MRgFUS Treatments Using PRF Thermometry Techniques and Optical Probes.

Structural and metabolic imaging are fundamental for diagnosis, treatment and follow-up in oncology. Beyond the well-established diagnostic imaging applications, ultrasounds are currently emerging in the clinical practice as a noninvasive technology for therapy. Indeed, the sound waves can be used to increase the temperature inside the target solid tumors, leading to apoptosis or necrosis of neoplastic tissues. The Magnetic resonance-guided focused ultrasound surgery (MRgFUS) technology represents a valid application of this ultrasound property, mainly used in oncology and neurology. In this paper; patient safety during MRgFUS treatments was investigated by a series of experiments in a tissue-mimicking phantom and performing ex vivo skin samples, to promptly identify unwanted temperature rises. The acquired MR images, used to evaluate the temperature in the treated areas, were analyzed to compare classical proton resonance frequency (PRF) shift techniques and referenceless thermometry methods to accurately assess the temperature variations. We exploited radial basis function (RBF) neural networks for referenceless thermometry and compared the results against interferometric optical fiber measurements. The experimental measurements were obtained using a set of interferometric optical fibers aimed at quantifying temperature variations directly in the sonication areas. The temperature increases during the treatment were not accurately detected by MRI-based referenceless thermometry methods, and more sensitive measurement systems, such as optical fibers, would be required. In-depth studies about these aspects are needed to monitor temperature and improve safety during MRgFUS treatments.