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Objectives: To compare clinical success, procedure time, and complication rates between MRI-guided and CT-guided real-time biopsies of small focal liver lesions (FLL) < 20 mm. Methods: A comparison of a prospectively collected MRI-guided cohort (n = 30) to a retrospectively collected CT-guided cohort (n = 147) was performed, in which patients underwent real-time biopsies of small FLL < 20 mm in a freehand technique. In both groups, clinical and periprocedural data, including clinical success, procedure time, and complication rates (classified according to CIRSE guidelines), were analyzed. Wilcoxon rank sum test, Pearson's chi-squared test, and Fisher's exact test were used for statistical analysis. Additionally, propensity score matching (PSM) was performed using the following criteria for direct matching: age, gender, presence of liver cirrhosis, liver lobe, lesion diameter, and skin-to-target distance. Results: The median FLL diameter in the MRI-guided cohort was significantly smaller compared to CT guidance (p < 0.001; 11.0 mm vs. 16.3 mm), while the skin-to-target distance was significantly longer (p < 0.001; 90.0 mm vs. 74.0 mm). MRI-guided procedures revealed significantly higher clinical success compared to CT guidance (p = 0.021; 97% vs. 79%) as well as lower complication rates (p = 0.047; 0% vs. 13%). Total procedure time was significantly longer in the MRI-guided cohort (p < 0.001; 38 min vs. 28 min). After PSM (n = 24/n = 38), MRI-guided procedures still revealed significantly higher clinical success compared to CT guidance (p = 0.039; 96% vs. 74%). Conclusion: Despite the longer procedure time, freehand biopsy of small FLL < 20 mm under MR guidance can be considered superior to CT guidance because of its high clinical success and low complication rates. Clinical relevance statement: Biopsy of small liver lesions is challenging due to the size and conspicuity of the lesions on native images. MRI offers higher soft tissue contrast, which translates into a higher success of obtaining enough tissue material with MRI compared to CT-guided biopsies. Key Points: • Image-guided biopsy of small focal liver lesions (FLL) is challenging due to inadequate visualization, leading to sampling errors and false-negative biopsies. • MRI-guided real-time biopsy of FLL < 20 mm revealed significantly higher clinical success (p = 0.021; 97% vs. 79%) and lower complication rates (p = 0.047; 0% vs. 13%) compared to CT guidance. • Although the procedure time is longer, MRI-guided biopsy can be considered superior for small FLL < 20 mm. [ABSTRACT FROM AUTHOR]

Interventional therapy has been widely used in surgeries involving neurology, vasculature, and breasts.Image-guided, robot-assisted interventional therapy significantly enhances surgical precision and safety, emerging as a critical trend in modern interventional surgery. Among various interventional imaging methods, interventional magnetic resonance imaging (i-MRI) stands out due to its excellent soft tissue differentiation, diverse imaging contrasts, ability to yield quantitative data, and no ionizing radiation. However, the challenges facing MRI-guided therapy include the relatively low speed of imaging and the stringent compatibility demands of interventional devices. Advance in the rapid i-MRI techniques and MR-compatible equipment have propelled i-MRI to a pivotal role in clinical applications, encompassing neurological, cardiovascular, prostate, and breast interventions. This review initially provides an overview of the current i-MRI landscape. It then consolidates the application of i-MRI in multiple medical interventions, offering illustrative examples. The article further delves into the obstacles posed by i-MRI, specifically slow imaging speed and the delicate spatiotemporal resolution balance. Ultimately, it envisages the growth potential of i-MRI in multimodal imaging, real-time MRI, and i-MRI-guided interventional robotic surgery.

BackgroundInterventional magnetic resonance imaging (iMRI) allows deep brain stimulator lead placement under general anesthesia. While the accuracy of lead targeting has been described for iMRI systems utilizing 1.5-tesla magnets, a similar assessment of 3-tesla iMRI procedures has not been performed.ObjectiveTo compare targeting accuracy, the number of lead targeting attempts, and surgical duration between procedures performed on 1.5- and 3-tesla iMRI systems.MethodsRadial targeting error, the number of targeting attempts, and procedure duration were compared between surgeries performed on 1.5- and 3-tesla iMRI systems (SmartFrame and ClearPoint systems).ResultsDuring the first year of operation of each system, 26 consecutive leads were implanted using the 1.5-tesla system, and 23 consecutive leads were implanted using the 3-tesla system. There was no significant difference in radial error (Mann-Whitney test, p = 0.26), number of lead placements that required multiple targeting attempts (Fisher's exact test, p = 0.59), or bilateral procedure durations between surgeries performed with the two systems (p = 0.15).ConclusionsAccurate DBS lead targeting can be achieved with iMRI systems utilizing either 1.5- or 3-tesla magnets. The use of a 3-tesla magnet, however, offers improved visualization of the target structures and allows comparable accuracy and efficiency of placement at the selected targets.

Background: Magnetic resonance imaging (MRI) is used far less as an imaging-guided method for percutaneous biopsies than computed tomography (CT) and ultrasound (US), despite its imaging benefits, particularly in children. Purpose: To evaluate the feasibility, accuracy and safety of MRI-guided biopsies in paediatric patient population. Material and Methods: The retrospective study included 57 consecutive paediatric patients (<18 years old). A percutaneous core needle biopsy (PCNB) or trephine biopsy was performed in 53 cases, and an additional fine-needle aspiration biopsy (FNAB) in 26 cases. In 4 cases, a stand-alone FNAB was taken. Biopsies were performed with 0.23 T open and 1.5 T closed MRI scanners. Statistical methods used for confidence intervals and p -values were Wilson score method and chi-square test. Results: The overall diagnostic accuracy of histologic biopsy was 0.94, with sensitivity 0.82, specificity 1.00, positive predictive value (PPV) 1.00 and negative predictive value (NPV) 0.92. In histological bone biopsies, diagnostic accuracy was 0.96, with sensitivity 0.86, specificity 1.00, PPV 1.00 and NPV 0.94. The FNAB sample diagnosis was associated with the histological diagnosis in 79% of cases. There were no major primary complications and only a few late complications. After biopsy, 83% of the children were ambulatory in 6 h. Anti-inflammatory drugs and paracetamol provided satisfactory pain relief in 96% of the patients after biopsy. Most outpatients (71%) were discharged from hospital either on the same day or 1 day later. Conclusion: MRI is a technically feasible, accurate and safe guidance tool for performing percutaneous biopsies in children. [ABSTRACT FROM AUTHOR]

Transcranial magnetic resonance-guided focused ultrasound is a recently introduced incisionless treating option for essential tremor and tremor-dominant idiopathic Parkinson disease. There is preliminary evidence that it may result in a promising effective treatment option for other movement disorders too. Here, we report on two patients with multiple sclerosis with medication refractory debilitating essential tremor comorbidity who successfully underwent unilateral Vim tcMRgFUS thalamotomy for tremor control. Patients' clinical condition and expanded disability status scale scores showed no changes during the 1-year follow-up period with no evidence of multiple sclerosis activity or progression. [ABSTRACT FROM AUTHOR]

Purpose: Acceleration of a passive tracking sequence based on phase‐only cross‐correlation (POCC) using radial undersampling. Methods: The phase‐only cross‐correlation (POCC) algorithm allows passive tracking of interventional instruments in real‐time. In a POCC sequence, two cross‐sectional images of a needle guide with a positive MR contrast are continuously acquired from which the instrument trajectory is calculated. Conventional Cartesian imaging for tracking is very time consuming; here, a higher temporal resolution is achieved using a highly undersampled radial acquisition together with a modified POCC algorithm that incorporates the point‐spread‐function. Targeting and needle insertion is performed in two phantom experiments with 16 fiducial targets, each using 4 and 16 radial projections for passive tracking. Additionally, targeting of eight deep lying basivertebral veins in the lumbar spines is performed for in vivo proof‐of‐application with four radial projections for needle guide tracking. Results: The radially undersampled POCC sequence yielded in the phantom experiments a lateral targeting accuracy of 1.1 ± 0.4 mm and 1.0 ± 0.5 mm for 16 and 4 radial projections, respectively, without any statistically significant difference. In the in vivo application, a mean targeting duration of 62 ± 13 s was measured. Conclusion: Radial undersampling can drastically reduce the acquisition time for passive tracking in a POCC sequences for MR‐guided needle interventions without compromising the targeting accuracy. [ABSTRACT FROM AUTHOR]

Objective: To present a retrospective analysis of patient- and sonication-related parameters of a group of patients treated with a transcranial magnetic resonance imaging (MRI)-guided focused ultrasound (tcMRgFUS) system integrated with a 1.5-T MRI unit.Methods: The data obtained from 59 patients, who underwent the tcMRgFUS procedure from January 2015 to April 2019, were retrospectively reviewed for this study. The following data, among others, were mainly collected: skull density ratio (SDR), skull area (SA), number of available transducer elements (Tx), and estimated focal power at target (FP). For each of the four different treatment stages, we calculated the number of sonication processes (Sn), user-defined sonication power (Sp), effective measured power (Smp), sonication duration (Sd), user-defined energy (E), effective measured energy (Em), maximum temperature (Tmax), and MR thermometry plane orientation. Furthermore, the time delay between each sonication (St) and the total treatment time (Tt) were recorded.Results: Fifty-two patients (40 males and 12 females; age 64.51 ± SD 11.90 years; range 26–86 years), who underwent unilateral Vim thalamotomy (left = 50, 96.15%; right = 2, 3.85%) for medication-refractory essential tremor (n = 39; 78%) or Parkinson tremor (n = 13; 22%) were considered. A total of 1,068 (95.10%) sonication processes were included in our final analysis (average Sn per treatment: 20.65 ± 6.18; range 13–41).The energy released onto the planned target was found to decrease with the SDR for all temperature ranges. A positive correlation was observed between the slope of Tmax vs. Em plot and the SDR (R2 = 0.765; p < 0.001). In addition, the Tmax was positively correlated with SDR (R2 = 0.398; p < 0.005). On the contrary, no significant correlation was found between SDR and SA or Tx. An analysis of the MR thermometry scanning plane indicated that, at our site, the axial and the coronal planes were used (on average) 10.4 (SD ± 3.8) and 7.7 (SD ± 3.0) times, respectively, whereas the sagittal plane was used only 2.5 (SD ± 3.0) times per treatment.Conclusion: Our results confirm the factors that significantly influence the course of a tcMRgFUS procedure even when a 1.5-T MRI scanner is used for procedure guidance. The experience we gained in this study indicates that the SDR remains one of the most significant technical parameters to be considered in a tcMRgFUS procedure. The possibility of prospectively setting the sonication energy according to the presented curves of energy delivery as a function of SDR for each treatment stage could provide a further understanding and a greater awareness of this emerging technology.

Purpose: Evaluation of technique effectiveness, patient safety and ablation parameters of MR-guided microwave ablation in hepatic malignancies using an MR-conditional high-power microwave ablation system. Materials and Methods: Institutional review board approval and informed patient consent were obtained. Patients who underwent MR-guided microwave ablation of hepatic malignancies in a 1.5T wide-bore scanner using a perfusion-cooled high-power microwave ablation system with a maximum generator power of 150 W were included. Ablation parameters comprising procedure durations, net ablation duration, applicator positions and ablation zone dimensions were recorded. Adverse events were classified according to the CIRSE classification system. Technique effectiveness was assessed after 1 month. Follow-up was conducted with contrast-enhanced MRI and ranged from 1 to 20 months (mean: 6.1 ± 5.4 months). Results: Twenty-one consecutive patients (age: 63.4 ± 10.5 years; 5 female) underwent 22 procedures for 28 tumours (9 hepatocellular carcinomas, 19 metastases) with a mean tumour diameter of 14.6 ± 5.4 mm (range: 6–24 mm). Technique effectiveness was achieved in all lesions. Tumours were treated using 1.7 ± 0.7 applicator positions (range: 1–3). Mean energy and ablation duration per tumour were 75.3 ± 35.4 kJ and 13.3 ± 6.2 min, respectively. Coagulation zone short- and long-axis diameters were 29.1 ± 6.4 mm and 39.9 ± 7.4 mm, respectively. Average procedure duration was 146.4 ± 26.2 min (range: 98–187 min). One minor complication was reported. Five patients developed new tumour manifestations in the untreated liver. Local tumour progression was not observed during initial follow-up. Conclusion: MR-guided high-power microwave ablation provides safe and effective treatment of hepatic malignancies with short ablation times and within acceptable procedure durations. [ABSTRACT FROM AUTHOR]

Objectives: To assess the intraoperative neuroimaging findings in patients treated with transcranial MR-guided focused ultrasound (tcMRgFUS) thalamotomy using 1.5T equipment in comparison with the 48-h follow-up. Methods: Fifty prospectively enrolled patients undergoing unilateral tcMRgFUS thalamotomy for either medication-refractory essential tremor (n = 39) or Parkinson tremor (n = 11) were included. Two radiologists evaluated the presence and size of concentric lesional zones (zone I, zone II, and zone III) on 2D T2-weighted sequences acquired intraoperatively after the last high-energy sonication and at 48 h. Sonication parameters including number of sonications, delivered energy, and treatment temperatures were also recorded. Differences in lesion pattern and size were assessed using the McNemar test and paired t test, respectively. Results: Zones I, II, and III were visualized in 34 (68%), 50 (100%), and 44 (88%) patients, and 31 (62%), 50 (100%), and 45 (90%) patients after the last high-energy sonication for R1 and R2, respectively. All three concentric zones were visualized intraoperatively in 56–58% of cases. Zone I was significantly more commonly visualized at 48 h (p < 0.001). Diameter of zones I and II and the thickness of zone III significantly increased at 48 h (p < 0.001). Diameters of zones I and II measured intraoperatively demonstrated significant correlation with thermal map temperatures (p ≤ 0.001). Maximum temperature significantly correlated with zone III thickness at 48 h. A threshold of 60.5° had a sensitivity of 56.5–66.7% and a specificity of 70.5–75.5% for thickness > 6 mm at 48 h. Conclusions: Intraoperative imaging may accurately detect typical lesional findings, before completing the treatment. These imaging characteristics significantly correlate with sonication parameters and 48-h follow-up. Key Points: • Intraoperative T2-weighted images allow the visualization of the zone I (coagulation necrosis) in most of the treated patients, while zone II (cytotoxic edema) is always detected. • Lesion size depicted with intraoperative transcranial MRgFUS imaging correlates well with procedure parameters. • Intraoperative transcranial MRgFUS imaging may have a significant added value for treating physicians. [ABSTRACT FROM AUTHOR]

Aims: 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.Materials and Methods: 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).Results: 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.Conclusions: 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. [ABSTRACT FROM AUTHOR]

Objectives: Invasive treatment of tumors adjacent to large hepatic vessels is a continuous clinical challenge. The primary aim of this study was to examine the feasibility of ablating liver tissue adjacent to large hepatic and portal veins with magnetic resonance imaging-guided high-intensity focused ultrasound (MRgHIFU). The secondary aim was to compare sonication data for ablations performed adjacent to hepatic veins (HV) versus portal veins (PV).Materials and Methods: MRgHIFU ablations were performed in six male land swine under general anesthesia. Ablation cells of either 4 or 8 mm diameter were planned in clusters (two/animal) adjacent either to HV (n = 6) or to PV (n = 6), with diameter ≥ 5 mm. Ablations were made using 200 W and 1.2 MHz. Post-procedure evaluation was made on contrast-enhanced MRI (T1w CE-MRI), histopathology, and ablation data from the HIFU system.Results: A total of 153 ablations in 81 cells and 12 clusters were performed. There were visible lesions with non-perfused volumes in all animals on T1w CE-MRI images. Histopathology showed hemorrhage and necrosis in all 12 clusters, with a median shortest distance to vessel wall of 0.4 mm (range 0-2.7 mm). Edema and endothelial swelling were observed without vessel wall rupture. In 8-mm ablations (n = 125), heat sink was detected more often for HV (43%) than for PV (19%; p = 0.04).Conclusions: Ablations yielding coagulative necrosis of liver tissue can be performed adjacent to large hepatic vessels while keeping the vessel walls intact. This indicates that perivascular tumor ablation in the liver is feasible using MRgHIFU.Key Points: • High-intensity focused ultrasound ablation is a non-invasive treatment modality that can be used for treatment of liver tumors. • This study shows that ablations of liver tissue can be performed adjacent to large hepatic vessels in an experimental setting. • Liver tumors close to large vessels can potentially be treated using this modality. [ABSTRACT FROM AUTHOR]

Atlantoaxial rotatory subluxation or fixation (AARF) is a rare condition, usually occurring in pediatric patients. It mimics benign torticollis but may result in permanent disability or death. The condition requires prompt diagnosis by thorough examination to avoid any treatment delays. Spiral computed tomography (CT) with three-dimensional reconstruction CT is recommended for identifying incongruence between C1 and C2 vertebrae, and magnetic resonance imaging (MRI) may be performed to exclude ligamentous injuries. In addition to static imaging, dynamic CT involves the reduction between C1 and C2 being confirmed using CT with the head turned maximally to the left and right. The present report (level of evidence, III) provides a method for treating AARF that has similar advantages as dynamic CT but avoids ionizing radiation by replacing CT with interventional MRI. The new method comprised simultaneous axial traction and manual closed reduction, performed under general anesthesia, and the use of interventional MRI to ensure that reduction was achieved and held. The head is turned maximally to the right and left during the manual reduction. A rigid cervical collar was used following reduction. Dynamic CT was not required but prior diagnostic static CT was performed in preparation. No further CT was required. There appears to be no previous studies on interventional MRI in AARF care. Being superior in its diagnostic soft-tissue visualization performance and lacking ionizing radiation, interventional MRI is a potential option for investigating and treating acute AARF in non-syndromic patients with no trauma history. [ABSTRACT FROM AUTHOR]

Background: Intraoperative magnetic resonance imaging (ioMRI) has led to significant advancements in neurosurgery with improved accuracy, assessment of the extent of resection, less invasive surgical alternatives, and real-time confirmation of targeting as well delivery of therapies. The costs associated with developing ioMRI units in the surgical suite have been obstacles to the expansion of their use. More recently, the development of hybrid interventional MRI (iMRI) units has become a viable alternative. The process of designing, developing, and implementing operations for these units requires the careful integration of environmental, technical, and safety elements of both surgical and MR practices. There is a paucity of published literature providing guidance for institutions looking to develop a hybrid iMRI unit, especially with a limited footprint in the radiology department. Methods: The experience of designing, developing, and implementing an iMRI in a preexisting space for neurosurgical procedures at a single institution in light of available options and the literature is described. Results: The development of the unit was accomplished through the engagement of a multidisciplinary team of stakeholders who utilized existing guidelines and recommendations and their own professional experience to address issues including physical layout, equipment selection, operations planning, infection control, and oversight/review, among others. Conclusion: Successful creation of an iMRI program requires multidisciplinary collaboration in integrating surgical and MR practice. The authors' aim is that the experience described in this article will serve as an example for facilities or neurosurgical departments looking to navigate the same process. [ABSTRACT FROM AUTHOR]

Objective: The objective of this paper is to introduce an acousto-optic optical fiber sensor for tracking catheter position during interventional magnetic resonance imaging (MRI) to overcome RF induced heating of active markers. Methods: The sensor uses a miniature coil coupled to a piezoelectric transducer, which is in turn mechanically connected to an optical fiber. The piezoelectric transducer converts the RF signal to acoustic waves in the optical fiber over a region including a fiber Bragg grating (FBG). The elastic waves in the fiber modulates the FBG geometry and hence the reflected light in the optical fiber. Since the coil is much smaller than the RF wavelength and the signal is transmitted on the dielectric optical fiber, the sensor effectively reduces RF induced heating risk. Proof of concept prototypes of the sensor are implemented using commercially available piezoelectric transducers and optical fibers with FBGs. The prototypes are characterized in a 1.5 T MRI system in comparison with an active tracking marker. Results: Acousto-optical sensor shows linear response with flip angle and it can be used to detect signals from multiple coils for potential orientation detection. It has been successfully used to detect the position of a tacking coil in phantom in an imaging experiment. Conclusion: Acousto-optical sensing is demonstrated for tracking catheters during interventional MRI. Real-time operation of the sensor requires sensitivity improvements like using a narrow band FBG. Significance: Acousto-optics provides a compact solution to sense RF signals in MRI with dielectric transmission lines. [ABSTRACT FROM AUTHOR]

Magnetic resonance-guided focused ultrasound is one of the emerging non-invasive technologies offering both image guidance and thermal monitoring. In recent years transcranial application of this technology is starting to impact heavily the neuroscience field. We present here the imaging protocol and the technological methods successfully used with a transcranial magnetic resonance-guided focused ultrasound system certified for clinical treatments of functional neurological disorders, integrated for the first time with a 1.5T magnetic resonance scanner. Compared to the body radiofrequency coil (the one commonly used with transcranial magnetic resonance-guided focused ultrasound system integrated with 3T magnetic resonance scanners), the use of a dedicated two channel coil enabled a signal-to-noise ratio gain up to five times higher. [ABSTRACT FROM AUTHOR]

Purpose: To quantitatively assess 12-month prostate volume (PV) reduction based on T2-weighted MRI and immediate post-treatment contrast-enhanced MRI non-perfused volume (NPV), and to compare measurements with predictions of acute and delayed ablation volumes based on MR-thermometry (MR-t), in a central radiology review of the Phase I clinical trial of MRI-guided transurethral ultrasound ablation (TULSA) in patients with localized prostate cancer.Materials and Methods: Treatment day MRI and 12-month follow-up MRI and biopsy were available for central radiology review in 29 of 30 patients from the published institutional review board-approved, prospective, multi-centre, single-arm Phase I clinical trial of TULSA. Viable PV at 12 months was measured as the remaining PV on T2-weighted MRI, less 12-month NPV, scaled by the fraction of fibrosis in 12-month biopsy cores. Reduction of viable PV was compared to predictions based on the fraction of the prostate covered by the MR-t derived acute thermal ablation volume (ATAV, 55°C isotherm), delayed thermal ablation volume (DTAV, 240 cumulative equivalent minutes at 43°C thermal dose isocontour) and treatment-day NPV. We also report linear and volumetric comparisons between metrics.Results: After TULSA, the median 12-month reduction in viable PV was 88%. DTAV predicted a reduction of 90%. Treatment day NPV predicted only 53% volume reduction, and underestimated ATAV and DTAV by 36% and 51%.Conclusion: Quantitative volumetry of the TULSA phase I MR and biopsy data identifies DTAV (240 CEM43 thermal dose boundary) as a useful predictor of viable prostate tissue reduction at 12 months. Immediate post-treatment NPV underestimates tissue ablation.Key Points: • MRI-guided transurethral ultrasound ablation (TULSA) achieved an 88% reduction of viable prostate tissue volume at 12 months, in excellent agreement with expectation from thermal dose calculations. • Non-perfused volume on immediate post-treatment contrast-enhanced MRI represents only 64% of the acute thermal ablation volume (ATAV), and reports only 60% (53% instead of 88% achieved) of the reduction in viable prostate tissue volume at 12 months. • MR-thermometry-based predictions of 12-month prostate volume reduction based on 240 cumulative equivalent minute thermal dose volume are in excellent agreement with reduction in viable prostate tissue volume measured on pre- and 12-month post-treatment T2w-MRI. [ABSTRACT FROM AUTHOR]

Objective: To accelerate a passive tracking sequence based on phase-only cross correlation (POCC) using simultaneous slice excitation.Methods: For magnetic resonance (MR)-guided biopsy procedures, passive markers have been proposed that can be automatically localized online using a POCC-based tracking sequence. To accelerate the sequence, a phase-offset multiplanar (POMP) excitation technique was implemented to acquire tracking images. In a phantom experiment, the POMP-POCC sequence was tested and compared with the sequential non-accelerated version in terms of duration and accuracy. Further, technical feasibility of the POMP-POCC sequence was tested in a patient undergoing a prostate biopsy.Results: The temporal resolution of the POMP-POCC tracking sequence is accelerated by 33% compared with the sequential approach. In phantom experiments, the POMP-POCC and sequential sequences yielded the same targeting accuracy of 1.6 ± 0.7 mm. Technical proof of concept of the new sequence could be demonstrated in a successful in vivo prostate biopsy.Conclusion: POMP-POCC tracking can substantially reduce the duration of localization of passive markers in MR-guided needle interventions without compromising targeting accuracy. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate the feasibility and safety of focal therapy for low-intermediate risk prostate cancer (PCa) with magnetic resonance-guided high frequency focused ultrasound (MRgFUS) METHODS: This IRB-approved phase 1 prospective study enrolled eight patients with prostate specific antigen (PSA) ≤ 10 ng/ml, ≤ cT2a and Gleason score ≤ 7 (4 + 3) disease following informed consent. Under MRI guidance, focused high frequency ultrasound energy was delivered to ablate the target tissue. Treatment-related adverse events were recorded. Oncologic outcomes were evaluated with multiparametric MRI, PSA and TRUS biopsy at 6 months following treatment.Results: Ten target lesions [six Gleason 6 lesions, two Gleason 7 (3 + 4) and two Gleason 7 (4 + 3)] were treated in eight men (prostate volume range, 25-50 cc; mean MRI time, 248 min per patient; mean sonication duration, 65 min). Mean target volume was 2.7 cc and mean post-treatment non-perfused volume was 4.3 cc. Quality of life parameters were similar between baseline and 6 months in 6/8 patients. All treated regions were negative on MRI; 4/8 patients and 6/10 target lesions (60%) were clear of disease on biopsy. One patient with 2-mm Gleason 8 disease in one of five cores from treatment site (4 + 3 disease at baseline) subsequently underwent prostatectomy with negative surgical margins. Three patients with low volume (5-15%) Gleason 6 residual disease were offered active surveillance. Mean PSA decreased from 5.06 at baseline to 3.4 ng/ml at 6 months.Conclusion: MRgFUS is a feasible and safe method of noninvasively ablating low-intermediate risk PCa with acceptable short-term oncologic outcomes.Key Points: • Focal therapy selectively ablates locally confined, clinically significant index lesion with a margin while sparing rest of gland and adjacent vital structures. • Magnetic resonance-guided focused high frequency ultrasound surgery (MRgFUS) combines MRI with HIFU. • MRgFUS provides ability to monitor treatments in real time and allows a targeted approach for focal ablation. • MRgFUS is a feasible, safe method of noninvasively ablating low-intermediate risk PCa. • MRgFUS provides acceptable oncologic outcomes at 6 months. [ABSTRACT FROM AUTHOR]

In deep brain stimulation (DBS) of the subthalamic nucleus (STN) for Parkinson's disease (PD), there is debate concerning the use of neuroimaging alone to confirm correct anatomic placement of the DBS lead into the STN, versus the use of microelectrode recording (MER) to confirm functional placement. We performed a retrospective study of a contemporaneous cohort of 45 consecutive patients who underwent either interventional- MRI (iMRI) or MER-guided DBS lead implantation. We compared radial lead error, motor and sensory side effect, and clinical benefit programming thresholds, and pre- and post-operative unified PD rating scale scores, and levodopa equivalent dosages. MERguided surgery was associated with greater radial error compared to the intended target. In general, side effect thresholds during initial programming were slightly lower in the MER group, but clinical benefit thresholds were similar. No significant difference in the reduction of clinical symptoms or medication dosage was observed. In summary, iMRI lead implantation occurred with greater anatomic accuracy, in locations demonstrated to be the appropriate functional region of the STN, based on the observation of similar programming side effect and benefit thresholds obtained with MER. The production of equivalent clinical outcomes suggests that surgeon and patient preference can be used to guide the decision of whether to recommend iMRI or MER-guided DBS lead implantation to appropriate patients with PD. [ABSTRACT FROM AUTHOR]

At present, imaging techniques such as fluoroscopy used for treatment of congenital heart diseases are not applicable for pediatric patients because of late cancer risk of ionizing radiation. Magnetic Resonance Imaging (MRI) presents an effective alternative to other x ray based imaging modalities with its superior soft tissue imaging feature, real-time functional measurement advantages and non-ionized imaging nature. In this study, a semi active guiding catheter was designed, that comprises low profile, MRI-compatible RF-resonant markers and is especially applicable in interventional procedures for pediatric patients with congenital heart diseases. In contrast to traditional fabrication techniques, components of the RFresonant marker were manufactured using a novel approach. Visualization of the RFresonant marker, that is integrated over biocompatible 5 Fr (1.67 mm) guiding catheter shaft, was shown under 1.5 T MRI. RF heating tests of the guiding catheter that contains the RF-resonant marker was realized according to ASTM F2182 - 11a standards. 0.25 0C heating was observed even under the worst conditions. Moreoever, in order to optimize the design and manufacturing of the RF-resonant markers, a finite element analysis simulation program (Comsol) was used. Presented method makes possible to manufacture interventional catheters, tools and devices that are safe and compatible with MRI. [ABSTRACT FROM AUTHOR]

There is no real need to discuss the potential advantages - mainly the excellent soft tissue contrast, nonionizing radiation, flow, and molecular information - of magnetic resonance imaging (MRI) as an intraoperative diagnosis and therapy system particularly for neurological applications and oncological therapies. Difficult patient access in conventional horizontal-field superconductive magnets, very high investment and operational expenses, and the need for special nonferromagnetic therapy tools have however prevented the widespread use of MRI as imaging and guidance tool for therapy purposes. The interventional use of MRI systems follows for the last 20+ years the strategy to use standard diagnostic systems and add more or less complicated and expensive components (eg, MRI-compatible robotic systems, specially shielded in-room monitors, dedicated tools and devices made from low-susceptibility materials, etc) to overcome the difficulties in the therapy process. We are proposing to rethink that approach using an in-room portable ultrasound (US) system that can be safely operated till 1 m away from the opening of a 3T imaging system. The live US images can be tracked using an optical inside-out approach adding a camera to the US probe in combination with optical reference markers to allow direct fusion with the MRI images inside the MRI suite. This leads to a comfortable US-guided intervention and excellent patient access directly on the MRI patient bed. This was combined with an entirely mechanical MRI-compatible 7 degrees of freedom holding arm concept, which shows that this test environment is a different way to create a costefficient and effective setup that combines the advantages of MRI and US by largely avoiding the drawbacks of current interventional MRI concepts. [ABSTRACT FROM AUTHOR]

Purpose To improve the precision of proton resonance frequency-shift magnetic resonance thermometry near ablation probes by recovering near-probe image signals that are typically lost due to magnetic susceptibility-induced field distortions. Methods A dual-echo gradient-recalled echo sequence was implemented, in which the first echo was under- or over-refocused in the slice dimension to recover image signal and temperature precision near a probe, and the second echo was fully refocused to obtain image signal everywhere else in the slice. A penalized maximum likelihood algorithm was implemented to estimate a single temperature map from both echoes. Agar phantom and ex vivo experiments with and without microwave heating at 3 T evaluated how much temperature precision was improved near a microwave ablator compared to a conventional single-echo scan as a function of slice and needle orientation in the magnet. Results The number of near-probe voxels with temperature standard deviation [ABSTRACT FROM AUTHOR]

Introduction: Physiology-guided deep brain stimulation (DBS) surgery requires patients to be awake during a portion of the procedure, which may be poorly tolerated. Interventional MRI-guided (iMRI) DBS surgery was developed to use real-time image guidance, obviating the need for patients to be awake during lead placement.Methods: All English-speaking adults with PD who underwent iMRI DBS between 2010 and 2014 at our Center were invited to participate. Subjects completed a structured interview that explored perioperative preferences and experiences. We compared these responses to patients who underwent the physiology-guided method, matched for age and gender.Results: Eighty-nine people with PD completed the study. Of those, 40 underwent iMRI, 44 underwent physiology-guided implantation, and five underwent both methods. There were no significant differences in baseline characteristics between groups. The primary reason for choosing iMRI DBS was a preference to be asleep during implantation due to: 1) a history of claustrophobia; 2) concerns about the potential for discomfort during the awake physiology-guided procedure in those with an underlying pain syndrome or severe off-medication symptoms; or 3) non-specific fear about being awake during neurosurgery.Conclusion: Participants were satisfied with both DBS surgery methods. However, identification of the factors associated with a preference for iMRI DBS may allow for optimization of patient experience and satisfaction when choices of surgical methods for DBS implantation are available. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate the feasibility of performing comprehensive Cardiac Magnetic resonance (CMR) guided electrophysiological (EP) interventions in a porcine model encompassing left atrial access.Methods: After introduction of two femoral sheaths 14 swine (41 ± 3.6 kg) were transferred to a 1.5 T MR scanner. A three-dimensional whole-heart sequence was acquired followed by segmentation and the visualization of all heart chambers using an image-guidance platform. Two MR conditional catheters were inserted. The interventional protocol consisted of intubation of the coronary sinus, activation mapping, transseptal left atrial access (n = 4), generation of ablation lesions and eventually ablation of the atrioventricular (AV) node. For visualization of the catheter tip active tracking was used. Catheter positions were confirmed by passive real-time imaging.Results: Total procedure time was 169 ± 51 minutes. The protocol could be completed in 12 swine. Two swine died from AV-ablation induced ventricular fibrillation. Catheters could be visualized and navigated under active tracking almost exclusively. The position of the catheter tips as visualized by active tracking could reliably be confirmed with passive catheter imaging.Conclusions: Comprehensive CMR-guided EP interventions including left atrial access are feasible in swine using active catheter tracking.Key Points: • Comprehensive CMR-guided electrophysiological interventions including LA access were conducted in swine. • Active catheter-tracking allows efficient catheter navigation also in a transseptal approach. • More MR-conditional tools are needed to facilitate left atrial interventions in humans. [ABSTRACT FROM AUTHOR]

Background/objectives The acute and long-term effects of interventional edge-to-edge repair on the mitral valve (MV) geometry are unclear. We sought to assess MV-annular geometry and the association of changes in MV-diameters with functional response one year after MitraClip implantation. Methods Consecutive patients ( n = 84; age 81.2 ± 8.3 years, logistic EuroSCORE 21.7 ± 17.9%) with symptomatic moderate-to-severe mitral regurgitation (MR) underwent MitraClip-procedure. MV-annular geometry was assessed with 3D TOE before, immediately and one year after clip implantation. Results 96.7% of secondary mitral regurgitation (SMR) patients presented with moderate-to-severe MR, 3.3% with severe SMR, respectively. 66.7% of primary MR (PMR) patients had moderate-to-severe MR, and 33.3% severe PMR respectively. When analyzing immediate effects of MitraClipC on mitral geometry, only patients with SMR ( n = 60, 71.4%) experienced significant reductions of the diastolic MV anterior-posterior diameters (AP: 3.9 ± 0.5 cm, 3.5 ± 0.7 cm; p < 0.001), and annulus-areas (2D: 12.9 ± 3.8 cm2, 12.6 ± 3.7 cm2; p < 0.001; 3D: 13.4 ± 3.8, 13.1 ± 3.2 cm2; p < 0.001). All measures on MV annular geometry were not significantly altered in patients with PMR ( p > 0.05). After one year of follow-up, MV annular parameters remained significantly reduced in SMR patients ( p < 0.05) and remained unchanged in subjects with PMR ( p > 0.05). Only SMR patients experienced significant increase in 6 min walking distances ( p = 0.004), decrease in pulmonary pressures ( p = 0.007) and functional NYHA-class ( p < 0.001); in patients with PMR only NYHA class improved after one year ( p < 0.001). Conclusion Edge-to-edge repair with the MitraClip-system impacts on MV-geometry in patients with SMR with stable results after 12 months. Reduction of MV-annular dimensions was associated with higher rates of persisting MR reduction and better functional status in patients with SMR. [ABSTRACT FROM AUTHOR]