MRgFUS ablation of a recurrent tenosynovial giant cell tumor in the foot using ExAblate 2100 system in combination with patient immobilization device

INTRODUCTION

Magnetic Resonance-guided Focused Ultrasound (MRgFUS) treatment for certain anatomy locations can be extremely challenging due to patient positioning and potential motion. This present study describes the treatment of a recurrent tenosynovial giant cell tumor of the plantar forefoot using the ExAblate 2100 system in combination with patient immobilization device.

METHODS

Prior to the treatment, several patient immobilization devices were investigated. Vacuum cushions were selected and tested for safety and compatibility with the treatment task and the MR environment.

RESULTS

During the treatment, one vacuum cushion immobilized the patient's right leg in knee flexion and allowed the bottom of the foot to be securely positioned on the treatment window. Another vacuum cushion supported the patient upper body extended outside the scanner bore. 19 sonications were successfully executed. The treatment was judged to be successful. No immediate complications were observed.

CONCLUSIONS

MRgFUS treatment of a recurrent tenosynovial giant cell tumor of the right plantar forefoot was successful with the use of patient immobilization vacuum cushions.

IMPLICATIONS FOR PRACTICE

The immobilization system could be utilized to aid future MRgFUS treatment of lesions in challenging anatomic locations. Various sizes of the vacuum cushions are available to potentially better accommodate other body parts and treatment configurations.

Aqueous Dispersion of Manganese-Zinc Ferrite Nanoparticles Protected by PEG as a T2 MRI Temperature Contrast Agent

Mixed manganese-zinc ferrite nanoparticles coated with PEG were studied for their potential usefulness in MRI thermometry as temperature-sensitive contrast agents. Particles in the form of an 8.5 nm core coated with a 3.5 nm layer of PEG were fabricated using a newly developed, one-step method. The composition of Mn0.48Zn0.46Fe2.06O4 was found to have a strong thermal dependence of magnetization in the temperature range between 5 and 50 °C. Nanoparticles suspended in an agar gel mimicking animal tissue and showing non-significant impact on cell viability in the biological test were studied with NMR and MRI over the same temperature range. For the concentration of 0.017 mg/mL of Fe, the spin-spin relaxation time T2 increased from 3.1 to 8.3 ms, while longitudinal relaxation time T1 shows a moderate decrease from 149.0 to 125.1 ms. A temperature map of the phantom exposed to the radial temperature gradient obtained by heating it with an 808 nm laser was calculated from T2 weighted spin-echo differential MR images. Analysis of temperature maps yields thermal/spatial resolution of 3.2 °C at the distance of 2.9 mm. The experimental relaxation rate R2 data of water protons were compared with those obtained from calculations using a theoretical model incorporating the motion averaging regime.

MRI-guided focused ultrasound ablation of painful lumbar facet joints: a retrospective assessment of safety and tolerability in human subjects

OBJECTIVE

To evaluate the safety and tolerability of MRI-guided focused ultrasound (MRgFUS) for the treatment of facet joint-mediated pain in human subjects for whom conventional treatment had failed. Secondarily, to evaluate effectiveness of the procedure.

METHODS

Consecutive patients who underwent MRgFUS at our institution were retrospectively identified. Chart review was performed to obtain relevant clinical and technical data. All patients had chronic low back pain and positive comparative medial branch blocks.

RESULTS

Twenty-six MRgFUS treatments in 20 patients were included. Mean sonication energy was 1436.6 Joules. The procedure was technically successful in all patients. Of the treated patients, 29.6% experienced short-term worsening of low back pain immediately after the procedure, all by 1-4 points on a 0-10 scale. One patient (3.8%) reported temporary worsening of preexisting radicular symptoms after the procedure. Of 21 treatments with clinical follow-up of at least 3 months available, 12 (57.1%) had >3 months' pain relief, 2 (10%) had <3 months' benefit, 6 (30%) reported no benefit, and 1 (5%) patient was lost to follow-up. In patients who reported at least some benefit with prior conventional radiofrequency ablation, 8/10 (80%) benefited from the MRgFUS procedure.

CONCLUSION

The present study demonstrates that MRgFUS ablation of the lumbar facet joints is a safe and tolerable procedure in human subjects and could provide another option for patients for whom radiofrequency ablation had failed. More than half of all patients received significant durable pain relief, which jumped to 80% for patients who had experienced at least some benefit from prior radiofrequency ablations.

Body Interventional MRI for Diagnostic and Interventional Radiologists: Current Practice and Future Prospects

Clinical use of MRI for guidance during interventional procedures emerged shortly after the introduction of clinical diagnostic MRI in the late 1980s. However, early applications of interventional MRI (iMRI) were limited owing to the lack of dedicated iMRI magnets, pulse sequences, and equipment. During the 3 decades that followed, technologic advancements in iMRI magnets that balance bore access and field strength, combined with the development of rapid MRI pulse sequences, surface coils, and commercially available MR-conditional devices, led to the rapid expansion of clinical iMRI applications, particularly in the field of body iMRI. iMRI offers several advantages, including superior soft-tissue resolution, ease of multiplanar imaging, lack of ionizing radiation, and capability to re-image the same section. Disadvantages include longer examination times, lack of MR-conditional equipment, less operator familiarity, and increased cost. Nonetheless, MRI guidance is particularly advantageous when the disease is best visualized with MRI and/or when superior soft-tissue contrast is needed for treatment monitoring. Safety in the iMRI environment is paramount and requires close collaboration among interventional radiologists, MR physicists, and all other iMRI team members. The implementation of risk-limiting measures for personnel and equipment in MR zones III and IV is key. Various commercially available MR-conditional needles, wires, and biopsy and ablation devices are now available throughout the world, depending on the local regulatory status. As such, there has been tremendous growth in the clinical applications of body iMRI, including localization of difficult lesions, biopsy, sclerotherapy, and cryoablation and thermal ablation of malignant and nonmalignant soft-tissue neoplasms. Online supplemental material is available for this article. ^©RSNA, 2021.

Uterine and Fibroid Imaging Analysis from the FIRSTT Study

Background: Women with uterine fibroids often seek uterine-preserving treatments, rather than hysterectomy. Imaging-defined endpoints following nonsurgical treatments for fibroids are limited. Materials and Methods: Fibroid Interventions: Reducing Symptoms Today and Tomorrow (FIRSTT), a randomized controlled trial of uterine artery embolization (UAE) versus magnetic resonance imaging-guided focused ultrasound surgery (MRgFUS), enrolled premenopausal women with symptomatic uterine fibroids. In this subanalysis, we report imaging results up to 36 months after UAE or MRgFUS. Magnetic resonance imaging (MRI) was performed at baseline for all women and during the 36 months after treatment if they did not meet other study endpoints. The main outcome of this subanalysis was fibroid volume reduction (defined both in terms of total fibroid load and volume of the largest fibroid), uterine volume reduction, and nonperfused volume. Results: During 2010-2014, 25 of the 37 women who were randomized and treated at Mayo Clinic had a 24-month follow-up MRI (11 UAE; 14 MRgFUS); among these women, 15 (7 UAE and 8 MRgFUS) had a 36-month follow-up MRI. Average age for the cohort was 44.1 (standard deviation, SD = 4.4) years. Nine patients had a second fibroid procedure by 36 months (seven in the MRgFUS arm and two in UAE arm). Median total fibroid load reduction was ∼50% in both treatment arms at both 24- and 36-month follow-up. Volume of the largest fibroid decreased more in the MRgFUS arm, whereas uterine volume decreased more in the UAE arm (neither reached statistical significance). At 24 months, median nonperfused volume was higher in the UAE arm (92%) than the MRgFUS arm (10%). Conclusions: Similar fibroid volume reduction was seen for the MRgFUS and UAE treatments in this comparative effectiveness study. Nonperfused volume 24 months after the procedure was higher in the UAE arm than in the MRgFUS arm. Clinical Trial Registration Number: NCT00995878, clinicaltrials.gov.

MRI and tractography techniques to localize the ventral intermediate nucleus and dentatorubrothalamic tract for deep brain stimulation and MR-guided focused ultrasound: a narrative review and update

The thalamic ventral intermediate nucleus (VIM) can be targeted for treatment of tremor by several procedures, including deep brain stimulation (DBS) and, more recently, MR-guided focused ultrasound (MRgFUS). To date, such targeting has relied predominantly on coordinate-based or atlas-based techniques rather than directly targeting the VIM based on imaging features. While general regional differences of features within the thalamus and some related white matter tracts can be distinguished with conventional imaging techniques, internal nuclei such as the VIM are not discretely visualized. Advanced imaging methods such as quantitative susceptibility mapping (QSM) and fast gray matter acquisition T1 inversion recovery (FGATIR) MRI and high-field MRI pulse sequences that improve the ability to image the VIM region are emerging but have not yet been shown to have reliability and accuracy to serve as the primary method of VIM targeting. Currently, the most promising imaging approach to directly identify the VIM region for clinical purposes is MR diffusion tractography.In this review and update, the capabilities and limitations of conventional and emerging advanced methods for evaluation of internal thalamic anatomy are briefly reviewed. The basic principles of tractography most relevant to VIM targeting are provided for familiarization. Next, the key literature to date addressing applications of DTI and tractography for DBS and MRgFUS is summarized, emphasizing use of direct targeting. This literature includes 1-tract (dentatorubrothalamic tract [DRT]), 2-tract (pyramidal and somatosensory), and 3-tract (DRT, pyramidal, and somatosensory) approaches to VIM region localization through tractography.The authors introduce a 3-tract technique used at their institution, illustrating the oblique curved course of the DRT within the inferior thalamus as well as the orientation and relationship of the white matter tracts in the axial plane. The utility of this 3-tract tractography approach to facilitate VIM localization is illustrated with case examples of variable VIM location, targeting superior to the anterior commissure-posterior commissure plane, and treatment in the setting of pathologic derangement of thalamic anatomy. Finally, concepts demonstrated with these case examples and from the prior literature are synthesized to highlight several potential advantages of tractography for VIM region targeting.

Symptom-specific differential motor network modulation by deep brain stimulation in Parkinson's disease

OBJECTIVE

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an established neurosurgical treatment for the motor symptoms of Parkinson's disease (PD). While often highly effective, DBS does not always yield optimal therapeutic outcomes, and stimulation-induced adverse effects, including paresthesia, muscle contractions, and nausea/lightheadedness, commonly occur and can limit the efficacy of stimulation. Currently, objective metrics do not exist for monitoring neural changes associated with stimulation-induced therapeutic and adverse effects.

METHODS

In the present study, the authors combined intraoperative functional MRI (fMRI) with STN DBS in 20 patients with PD to test the hypothesis that stimulation-induced blood oxygen level-dependent signals contained predictive information concerning the therapeutic and adverse effects of stimulation.

RESULTS

As expected, DBS resulted in blood oxygen level-dependent activation in myriad motor regions, including the primary motor cortex, caudate, putamen, thalamus, midbrain, and cerebellum. Across the patients, DBS-induced improvements in contralateral Unified Parkinson's Disease Rating Scale tremor subscores correlated with activation of thalamic, brainstem, and cerebellar regions. In addition, improvements in rigidity and bradykinesia subscores correlated with activation of the primary motor cortex. Finally, activation of specific sensorimotor-related subregions correlated with the presence of DBS-induced adverse effects, including paresthesia and nausea (cerebellar cortex, sensorimotor cortex) and unwanted muscle contractions (caudate and putamen).

CONCLUSIONS

These results suggest that DBS-induced activation patterns revealed by fMRI contain predictive information with respect to the therapeutic and adverse effects of DBS. The use of fMRI in combination with DBS therefore may hold translational potential to guide and improve clinical stimulator optimization in patients.

Novel Focal Therapeutic Hypothermia Device for Treatment of Acute Neurologic Injury: Large Animal Safety and Efficacy Trial

Objective Therapeutic hypothermia is a potentially powerful and controversial clinical tool for neuroprotection following acute neurologic pathology, particularly vascular injury. Indeed, therapeutic hypothermia remains a standard of care for postcardiac arrest ischemia and acute neonatal hypoxic-ischemic encephalopathy, improving both survival and outcomes. Although therapeutic hypothermia remains promising for cellular and systems-based neuronal protection in other neurologic injury states, the systemic side effects have limited clinical utility, confounded analysis of potential neurologic benefits, and precluded the completion of meaningful clinical trials.

Methods To address such limitations, we developed and tested a novel, minimally invasive, neurocritical care device that employs continuous circulation of cold saline through the pharyngeal region to deliver focal cerebrovascular cooling. We conducted a preclinical safety and efficacy trial in six adult porcine animals to assess the validity and functionality of the NeuroSave device, and assess cooling potential following middle cerebral artery occlusion (n = 2).

Results NeuroSave consistently lowered brain parenchymal temperature by a median of 9°C relative to core temperature within 60 minutes of initiation, including in ischemic cerebral parenchyma. The core body temperature experienced a maximal reduction of 2°C, or 5% of body temperature, with no associated adverse effects identified.

Conclusion The present study uses a large animal preclinical model to demonstrate the safety and efficacy of a novel, noninvasive device for the induction of robust and systemically safe hypothermia within the brain.

Experimental Investigation of Cryoneedle Heating during MR-Guided Cryoablation in Ex Vivo Tissue Samples at 1.5-Tesla

PURPOSE

To investigate cryoneedle heating risks during magnetic resonance (MR)-guided cryoablation and potential strategies to mitigate these risks.

MATERIALS AND METHODS

Ex vivo experiments were performed on a 1.5-Tesla (T) MR scanner using an MR conditional cryoablation system on porcine tissue phantoms. Cryoneedles were placed inside the tissue phantom either with or without an angiocatheter. Typical cryoneedle geometric configurations (including gas supply line) encountered in clinical procedures with low to high expected heating risks were investigated. Up to 4 fiber optic temperature sensors were attached to the cryoneedle/angiocatheter to measure the MR-induced cryoneedle heating at different locations during MR with different estimated specific absorption rates (SARs). The impact of cryoneedle heating on cryoablation treatment was studied by comparing temperature changes during 10-min freeze-thaw cycles with and without MR.

RESULTS

Rapid temperature increases of >100 °C in < 2 minutes were observed during MR with a SAR of 2.1 W/kg. The temperature changes during a typical freeze-thaw cycle were also affected by cryoneedle heating when MR was used to monitor the ice-ball evolution. The observed cryoneedle heating was affected by multiple factors; including cryoneedle geometric configurations, sequence SAR, whether an angiocatheter was used, and whether the cryoneedle was connected to the rest of the cryoablation system.

CONCLUSIONS

The ex vivo experiments demonstrated that MR could induce significant cryoneedle heating risks. Furthermore, MR-induced cryoneedle heating can affect temperatures in the ice-ball evolution during the freeze-thaw cycle. Several practical strategies to reduce the cryoneedle heating have been proposed.

Magnetic Resonance Imaging–Guided Focused Ultrasound Ablation of Lumbar Facet Joints of a Patient With a Magnetic Resonance Image Non-Conditional Pacemaker at 1.5T

Objective

Patient and Methods

Results

Conclusion

Zero TE MRI for Craniofacial Bone Imaging

Zero TE MR imaging is a novel technique that achieves a near-zero time interval between radiofrequency excitation and data acquisition, enabling visualization of short-T2 materials such as cortical bone. Zero TE offers a promising radiation-free alternative to CT with rapid, high-resolution, silent, and artifact-resistant imaging, as well as the potential for "pseudoCT" reconstructions. In this report, we will discuss our preliminary experience with zero TE, including technical principles and a clinical case series demonstrating emerging applications in neuroradiology.

Improved MR-thermometry during hepatic microwave ablation by correcting for intermittent electromagnetic interference artifacts

MRI-guided microwave ablation (MWA) is a minimally invasive treatment for localized cancer. MR thermometry has been shown to be able to provide vital information for monitoring the procedure in real-time. However, MRI during active MWA can suffer from image quality degradation due to intermittent electromagnetic interference (EMI). A novel approach to correct for EMI-contaminated images is presented here to improve MR thermometry during clinical hepatic MWA. The method was applied to MR-thermometry images acquired during four MR-guided hepatic MWA treatments using a commercially available MRI-configured microwave generator system. During the treatments MR thermometry data acquisition was synchronized to respiratory cycle to minimize the impact of motion. EMI was detected and corrected using uncontaminated k-space data from nearby frames in k-space. Substantially improved temperature and thermal damage maps have been obtained and the treatment zone can be better visualized. Our ex vivo tissue sample study shows the correction introduced minimal errors to the temperature maps and thermal damage maps.

Magnetic Resonance-Guided Prostate Ablation

In 2019, the American Cancer Society (ACS) estimates that 174,650 new cases of prostate cancer will be diagnosed and 31,620 will die due to the prostate cancer in the United States. Prostate cancer is often managed with aggressive curative intent standard therapies including radiotherapy or surgery. Regardless of how expertly done, these standard therapies often bring significant risk and morbidity to the patient's quality of life with potential impact on sexual, urinary, and bowel functions. Additionally, improved screening programs, using prostatic-specific antigen and transrectal ultrasound-guided systematic biopsy, have identified increasing numbers of low-risk, low-grade "localized" prostate cancer. The potential, localized, and indolent nature of many prostate cancers presents a difficult decision of when to intervene, especially within the context of the possible comorbidities of aggressive standard treatments. Active surveillance has been increasingly instituted to balance cancer control versus treatment side effects; however, many patients are not comfortable with this option. Although active debate continues on the suitability of either focal or regional therapy for the low- or intermediate-risk prostate cancer patients, no large consensus has been achieved on the adequate management approach. Some of the largest unresolved issues are prostate cancer multifocality, limitations of current biopsy strategies, suboptimal staging by accepted imaging modalities, less than robust prediction models for indolent prostate cancers, and safety and efficiency of the established curative therapies following focal therapy for prostate cancer. In spite of these restrictions, focal therapy continues to confront the current paradigm of therapy for low- and even intermediate-risk disease. It has been proposed that early detection and proper characterization may play a role in preventing the development of metastatic disease. There is level-1 evidence supporting detection and subsequent aggressive treatment of intermediate- and high-risk prostate cancer. Therefore, accurate assessment of cancer risk (i.e., grade and stage) using imaging and targeted biopsy is critical. Advances in prostate imaging with MRI and PET are changing the workup for these patients, and advances in MR-guided biopsy and therapy are propelling prostate treatment solutions forward faster than ever.

Safety of Laser Interstitial Thermal Therapy in Patients With Pacemakers

BACKGROUND AND IMPORTANCE

Laser interstitial thermal therapy (LiTT) has increasingly been used as a treatment option for medically refractory epilepsy, tumors, and radiation necrosis. The use of LiTT requires intraoperative magnetic resonance (MR) thermography. This can become an issue in patients with other implanted therapeutic devices such as pacemakers and vagal nerve stimulators due to concerns regarding increases in the specific absorption rate (SAR). This is a technical case report demonstrating a successfully and safely performed LiTT in a 1.5-T magnetic resonance imaging (MRI) in a patient with a pacemaker for mesial temporal sclerosis.

CLINICAL PRESENTATION

An 83-yr-old gentleman who had an implanted cardiac pacemaker presented with medically intractable epilepsy and was confirmed to have mesial temporal sclerosis on imaging. Video electroencephalography demonstrated concordant ipsilateral seizures and semiology. He underwent LiTT for ablation of the mesial temporal lobe. This was performed with the below described protocol with a cardiology nurse monitoring the patient's cardiac condition and a physicist monitoring SAR, and MR imaging quality without any adverse events.

CONCLUSION

This study reports on a protocol of cardiac and MR SAR to safely perform MR-guided LiTT in the setting of traditional pacemakers in patients who are not pacemaker dependent.

FIRSTT study: randomized controlled trial of uterine artery embolization vs focused ultrasound surgery

BACKGROUND

Uterine leiomyomas (fibroid tumors) cause considerable symptoms in 30-50% of women and are the leading cause of hysterectomy in the United States. Women with uterine fibroid tumors often seek uterine-preserving treatments, but comparative effectiveness trials are lacking.

OBJECTIVE

The purpose of this study was to report treatment effectiveness and ovarian function after uterine artery embolization vs magnetic resonance imaging-guided focused ultrasound surgery from the Fibroid Interventions: Reducing Symptoms Today and Tomorrow study.

STUDY DESIGN

The Fibroid Interventions: Reducing Symptoms Today and Tomorrow study, which is a randomized controlled trial of uterine artery embolization vs magnetic resonance imaging-guided focused ultrasound surgery, enrolled premenopausal women with symptomatic uterine fibroid tumors; women who declined randomization were enrolled in a parallel observational cohort. A comprehensive cohort design was used for outcomes analysis. Our target enrollment was 220 women, of which we achieved 41% (n=91) in the randomized and parallel arms of the trial. Primary outcome was reintervention for uterine fibroid tumors within 36 months. Secondary outcomes were change in serum anti-Müllerian hormone levels and standardized measures of fibroid symptoms, quality of life, pain, and sexual function.

RESULTS

From 2010-2014, 83 women (mean age, 44.4 years) were treated in the comprehensive cohort design (43 for magnetic resonance imaging-guided focused ultrasound surgery [27 randomized]; 40 for uterine artery embolization [22 randomized]); baseline clinical and uterine characteristics were similar between treatment arms, except for higher fibroid load in the uterine artery embolization arm. The risk of reintervention was higher with magnetic resonance imaging-guided focused ultrasound surgery than uterine artery embolization (hazard ratio, 2.81; 95% confidence interval, 1.01-7.79). Uterine artery embolization showed a significantly greater absolute decrease in anti-Müllerian hormone levels at 24 months compared with magnetic resonance imaging-guided focused ultrasound surgery. Quality of life and pain scores improved in both arms but to a greater extent in the uterine artery embolization arm. Higher pretreatment anti-Müllerian hormone level and younger age at treatment increased the overall risk of reintervention.

CONCLUSION

Our study demonstrates a lower reintervention rate and greater improvement in symptoms after uterine artery embolization, although some of the effectiveness may come through impairment of ovarian reserve. Both pretreatment anti-Müllerian hormone level and age are associated with risk of reintervention.

CLINICAL TRIAL REGISTRATION NUMBER

NCT00995878, clinicaltrials.gov.

Laser ablation for mesial temporal epilepsy: a multi-site, single institutional series

OBJECTIVE

Although it is still early in its application, laser interstitial thermal therapy (LiTT) has increasingly been employed as a surgical option for patients with mesial temporal lobe epilepsy. This study aimed to describe mesial temporal lobe ablation volumes and seizure outcomes following LiTT across the Mayo Clinic's 3 epilepsy surgery centers.

METHODS

This was a multi-site, single-institution, retrospective review of seizure outcomes and ablation volumes following LiTT for medically intractable mesial temporal lobe epilepsy between October 2011 and October 2015. Pre-ablation and post-ablation follow-up volumes of the hippocampus were measured using FreeSurfer, and the volume of ablated tissue was also measured on intraoperative MRI using a supervised spline-based edge detection algorithm. To determine seizure outcomes, results were compared between those patients who were seizure free and those who continued to experience seizures.

RESULTS

There were 23 patients who underwent mesial temporal LiTT within the study period. Fifteen patients (65%) had left-sided procedures. The median follow-up was 34 months (range 12-70 months). The mean ablation volume was 6888 mm3. Median hippocampal ablation was 65%, with a median amygdala ablation of 43%. At last follow-up, 11 (48%) of these patients were seizure free. There was no correlation between ablation volume and seizure freedom (p = 0.69). There was also no correlation between percent ablation of the amygdala (p = 0.28) or hippocampus (p = 0.82) and seizure outcomes. Twelve patients underwent formal testing with computational visual fields. Visual field changes were seen in 67% of patients who underwent testing. Comparing the 5 patients with clinically noticeable visual field deficits to the rest of the cohort showed no significant difference in ablation volume between those patients with visual field deficits and those without (p = 0.94). There were 11 patients with follow-up neuropsychological testing. Within this group, verbal learning retention was 76% in the patients with left-sided procedures and 89% in those with right-sided procedures.

CONCLUSIONS

In this study, there was no significant correlation between the ablation volume after LiTT and seizure outcomes. Visual field deficits were common in formally tested patients, much as in patients treated with open temporal lobectomy. Further studies are required to determine the role of amygdalohippocampal ablation.

Development of a robust MRI fiducial system for automated fusion of MR-US abdominal images

We present the development of a two‐component magnetic resonance (MR) fiducial system, that is, a fiducial marker device combined with an auto‐segmentation algorithm, designed to be paired with existing ultrasound probe tracking and image fusion technology to automatically fuse MR and ultrasound (US) images. The fiducial device consisted of four ~6.4 mL cylindrical wells filled with 1 g/L copper sulfate solution. The algorithm was designed to automatically segment the device in clinical abdominal MR images. The algorithm's detection rate and repeatability were investigated through a phantom study and in human volunteers. The detection rate was 100% in all phantom and human images. The center‐of‐mass of the fiducial device was robustly identified with maximum variations of 2.9 mm in position and 0.9° in angular orientation. In volunteer images, average differences between algorithm‐measured inter‐marker spacings and actual separation distances were 0.53 ± 0.36 mm. “Proof‐of‐concept” automatic MR‐US fusions were conducted with sets of images from both a phantom and volunteer using a commercial prototype system, which was built based on the above findings. Image fusion accuracy was measured to be within 5 mm for breath‐hold scanning. These results demonstrate the capability of this approach to automatically fuse US and MR images acquired across a wide range of clinical abdominal pulse sequences.

MR-Guided Prostate Interventions

Prostate cancer is the most commonly diagnosed noncutaneous cancer and second leading cause of death in men. Many patients with clinically organ-confined prostate cancer undergo definitive treatment of the whole gland, including radical prostatectomy, radiation therapy, and cryosurgery. Active surveillance is a growing alternative option for patients with documented low-volume and low-grade prostate cancer. However, many patients are wanting a less morbid focal treatment alternative. With recent advances in software and hardware of magnetic resonance imaging (MRI), multiparametric MRI of the prostate has been shown to improve the accuracy in detecting and characterizing clinically significant prostate cancer. Targeted biopsy is increasingly utilized to improve the yield of MR detected, clinically significant prostate cancer and to decrease in detection of indolent prostate cancer. MR-guided targeted biopsy techniques include cognitive MR fusion transrectal ultrasound (TRUS) biopsy, in-bore transrectal targeted biopsy using robotic transrectal device, and in-bore direct MR-guided transperineal biopsy with a software based transperineal grid template. In addition, advances in MR-compatible thermal ablation technology allow accurate focal or regional delivery of thermal ablative energy to the biopsy-proved, MRI-detected tumor. MR-guided ablative treatment options include cryoablation, laser ablation, and high-intensity focused ultrasound with real-time or near simultaneous monitoring of the ablation zone. We present a contemporary review of MR-guided techniques for prostatic interventions.

Uterine fibroids: correlations between MRI appearance and stiffness via magnetic resonance elastography

RATIONALE AND OBJECTIVES

Magnetic resonance elastography has proven to be a valuable tool in the diagnosis of liver fibrosis, breast and cervical cancer, but its application in uterine fibroids requires further characterization. The aim of the present study was to examine the relationship between uterine fibroid stiffness by MRE and MR imaging characteristics.

MATERIALS AND METHODS

An IRB-approved, HIPAA compliant review was performed of prospectively collected pelvic MRI and 2D-MRE data in patients with symptomatic uterine fibroids (N = 102). T1 and T2 weighted pelvic MRI with gadolinium enhancement were performed. In a small patient subset, fibroid stiffness was assessed by both 2D and 3D MRE. Fibroid stiffness by modality or imaging characteristics was analyzed using one-way analysis of variance followed by Student t test.

RESULTS

Four fibroid groups were identified based on T2 appearance: Isointense (N = 7), bright (N = 6), dark with minimal heterogeneity (N = 69), and dark with substantial heterogeneity (N = 20). Mean fibroid stiffness was 4.81 ± 2.12 kPa. Comparison of fibroid stiffness by T2 signal intensity showed that T2 bright fibroids were significantly less stiff than fibroids appearing T2 dark with minimal heterogeneity (mean stiffness difference = 2.38 kPa; p < 0.05) and T2 dark fibroids with substantial heterogeneity were significantly less stiff than T2 dark fibroids with minimal heterogeneity (mean difference = 1.25 kPa; p < 0.05). There was no significant association between fibroid stiffness and T1 signal characteristics or gadolinium enhancement. There was no significant difference in stiffness values obtained by either 2D vs. 3D MRE.

CONCLUSIONS

These data suggest differences in fibroid stiffness are associated with different T2 imaging characteristics with less stiff fibroids being T2 bright and more stiff fibroids being T2 dark. Further studies are needed to determine if fibroid stiffness by MRE may serve as an imaging biomarker to help predict MR-guided treatment response.

Global network modulation during thalamic stimulation for Tourette syndrome

Background and objectives

Deep brain stimulation (DBS) of the thalamus is a promising therapeutic alternative for treating medically refractory Tourette syndrome (TS). However, few human studies have examined its mechanism of action. Therefore, the networks that mediate the therapeutic effects of thalamic DBS remain poorly understood.

Methods

Five participants diagnosed with severe medically refractory TS underwent bilateral thalamic DBS stereotactic surgery. Intraoperative fMRI characterized the blood oxygen level-dependent (BOLD) response evoked by thalamic DBS and determined whether the therapeutic effectiveness of thalamic DBS, as assessed using the Modified Rush Video Rating Scale test, would correlate with evoked BOLD responses in motor and limbic cortical and subcortical regions.

Results

Our results reveal that thalamic stimulation in TS participants has wide-ranging effects that impact the frontostriatal, limbic, and motor networks. Thalamic stimulation induced suppression of motor and insula networks correlated with motor tic reduction, while suppression of frontal and parietal networks correlated with vocal tic reduction. These regions mapped closely to major regions of interest (ROI) identified in a nonhuman primate model of TS.

Conclusions

Overall, these findings suggest that a critical factor in TS treatment should involve modulation of both frontostriatal and motor networks, rather than be treated as a focal disorder of the brain. Using the novel combination of DBS-evoked tic reduction and fMRI in human subjects, we provide new insights into the basal ganglia-cerebellar-thalamo-cortical network-level mechanisms that influence the effects of thalamic DBS. Future translational research should identify whether these network changes are cause or effect of TS symptoms.

Evaluations of UltraiQ software for objective ultrasound image quality assessment using images from a commercial scanner

We evaluated a commercially available software package that uses B-mode images to semi-automatically measure quantitative metrics of ultrasound image quality, such as contrast response, depth of penetration (DOP), and spatial resolution (lateral, axial, and elevational). Since measurement of elevational resolution is not a part of the software package, we achieved it by acquiring phantom images with transducers tilted at 45 degrees relative to the phantom. Each measurement was assessed in terms of measurement stability, sensitivity, repeatability, and semi-automated measurement success rate. All assessments were performed on a GE Logiq E9 ultrasound system with linear (9L or 11L), curved (C1-5), and sector (S1-5) transducers, using a CIRS model 040GSE phantom. In stability tests, the measurements of contrast, DOP, and spatial resolution remained within a ±10% variation threshold in 90%, 100%, and 69% of cases, respectively. In sensitivity tests, contrast, DOP, and spatial resolution measurements followed the expected behavior in 100%, 100%, and 72% of cases, respectively. In repeatability testing, intra- and inter-individual coefficients of variations were equal to or less than 3.2%, 1.3%, and 4.4% for contrast, DOP, and spatial resolution (lateral and axial), respectively. The coefficients of variation corresponding to the elevational resolution test were all within 9.5%. Overall, in our assessment, the evaluated package performed well for objective and quantitative assessment of the above-mentioned image qualities under well-controlled acquisition conditions. We are finding it to be useful for various clinical ultrasound applications including performance comparison between scanners from different vendors.

Evaluation of feasibility of 1.5 Tesla prostate MRI using body coil RF transmit in a patient with an implanted vagus nerve stimulator

PURPOSE

To assess risks of RF-heating of a vagus nerve stimulator (VNS) during 1.5 T prostate MRI using body coil transmit and to compare these risks with those associated with MRI head exams using a transmit/receive head coil.

METHODS

Spatial distributions of radio-frequency (RF) B1 fields generated by transmit/receive (T/R) body and head coils were empirically assessed along the long axis of a 1.5 T MRI scanner bore. Measurements were obtained along the center axis of the scanner and laterally offset by 15 cm (body coil) and 7 cm (head coil). RF-field measurements were supplemented with direct measurements of RF-heating of 15 cm long copper wires affixed to and submerged in the "neck" region of the gelled saline-filled (sodium chloride and polyacrylic acid) "head-and-torso" phantom. Temperature elevations at the lead tips were measured using fiber-optic thermometers with the phantom positioned at systematically increased distances from the scanner isocenter.

RESULTS

B1 field measurements demonstrated greater than 10 dB reduction in RF power at distances beyond 28 cm and 24 cm from isocenter for body and head coil, respectively. Moreover, RF power from body coil transmit at distances greater than 32 cm from isocenter was found to be lower than from the RF power from head coil transmit measured at locations adjacent to the coil array at its opening. Correspondingly, maximum temperature elevations at the tips of the copper wires decreased with increasing distance from isocenter - from 7.4°C at 0 cm to no appreciable heating at locations beyond 40 cm.

CONCLUSIONS

For the particular scanner model evaluated in this study, positioning an implanted VNS farther than 32 cm from isocenter (configuration achievable for prostate exams) can reduce risks of RF-heating resulting from the body coil transmit to those associated with using a T/R head coil.

Intramuscular fat infiltration evaluated by magnetic resonance imaging predicts the extensibility of the supraspinatus muscle

INTRODUCTION

Rotator cuff (RC) tears result in muscle atrophy and fat infiltration within the RC muscles. An estimation of muscle quality and deformation, or extensibility, is useful in selecting the most appropriate surgical procedure. We determined if noninvasive quantitative assessment of intramuscular fat using MRI could be used to predict extensibility of the supraspinatus muscle.

METHODS

Seventeen cadaveric shoulders were imaged to assess intramuscular fat infiltration. Extensibility and histological evaluations were then performed.

RESULTS

Quantitative fat infiltration positively correlated with histological findings and presented a positive correlation with muscle extensibility (r = 0.69; P = 0.002). Extensibility was not significantly different between shoulders graded with a higher fat content versus those with low fat when implementing qualitative methods.

DISCUSSION

A noninvasive prediction of whole-muscle extensibility may directly guide pre-operative planning to determine if the torn edge could efficiently cover the original footprint while aiding in postoperative evaluation of RC repair. Muscle Nerve 57: 129-135, 2018.

Periprocedural outcomes comparing fibroid embolization and focused ultrasound: a randomized controlled trial and comprehensive cohort analysis

BACKGROUND

Uterine fibroids are a common problem for reproductive-aged women, yet little comparative effectiveness research is available to guide treatment choice. Uterine artery embolization and magnetic resonance imaging-guided focused ultrasound surgery are minimally invasive therapies approved by the US Food and Drug Administration for treating symptomatic uterine fibroids. The Fibroid Interventions: Reducing Symptoms Today and Tomorrow study is the first randomized controlled trial to compare these 2 fibroid treatments.

OBJECTIVE

The objective of the study was to summarize treatment parameters and compare recovery trajectory and adverse events in the first 6 weeks after treatment.

STUDY DESIGN

Premenopausal women with symptomatic uterine fibroids seen at 3 US academic medical centers were enrolled in the randomized controlled trial (n = 57). Women meeting identical criteria who declined randomization but agreed to study participation were enrolled in a nonrandomized parallel cohort (n = 34). The 2 treatment groups were analyzed by using a comprehensive cohort design. All women undergoing focused ultrasound and uterine artery embolization received the same postprocedure prescriptions, instructions, and symptom diaries for comparison of recovery in the first 6 weeks. Return to work and normal activities, medication use, symptoms, and adverse events were captured with postprocedure diaries. Data were analyzed using the Wilcoxon rank sum test or χ² test. Multivariable regression was used to adjust for baseline pain levels and fibroid load when comparing opioid medication, adverse events, and recovery time between treatment groups because these factors varied at baseline between groups and could affect outcomes. Adverse events were also collected.

RESULTS

Of 83 women in the comprehensive cohort design who underwent treatment, 75 completed postprocedure diaries. Focused ultrasound surgery was a longer procedure than embolization (mean [SD], 405 [146] vs 139 [44] min; P <.001). Of women undergoing focused ultrasound (n = 43), 23 (53%) underwent 2 treatment days. Immediate self-rated postprocedure pain was higher after uterine artery embolization than focused ultrasound (median [interquartile range], 5 [1-7] vs 1 [1-4]; P = .002). Compared with those having focused ultrasound (n = 39), women undergoing embolization (n = 36) were more likely to use outpatient opioid (75% vs 21%; P < .001) and nonsteroidal antiinflammatory medications (97% vs 67%; P < .001) and to have a longer median (interquartile range) recovery time (days off work, 8 [6-14] vs 4 [2-7]; P < .001; days until return to normal, 15 [10-29] vs 10 [10-15]; P = .02). There were no significant differences in the incidence or severity of adverse events between treatment arms; 86% of adverse events (42 of 49) required only observation or nominal treatment, and no events caused permanent sequelae or death. After adjustment for baseline pain and uterine fibroid load, uterine artery embolization was still significantly associated with higher opioid use and longer time to return to work and normal activities (P < .001 for each). Results were similar when restricted to the randomized controlled trial.

CONCLUSION

Women undergoing uterine artery embolization have longer recovery times and use more prescription medications, but women undergoing focused ultrasound have longer treatment times. These findings were independent of baseline pain levels and fibroid load.

The Impact of Mirth-Inducing Ventral Striatal Deep Brain Stimulation on Functional and Effective Connectivity

Deep brain stimulation (DBS) of the ventral capsule/ventral striatum (VC/VS) is an investigational therapy for treatment-resistant obsessive-compulsive disorder. The ability of VC/VS DBS to evoke spontaneous mirth in patients, often accompanied by smiling and laughter, is clinically well documented. However, the neural correlates of DBS-evoked mirth remain poorly characterized. Patients undergoing VC/VS DBS surgery underwent intraoperative evaluation in which mirth-inducing and non-mirth-inducing stimulation localizations were identified. Using dynamic causal modeling (DCM) for fMRI, the effect of mirth-inducing DBS on functional and effective connectivity among established nodes in limbic cortico-striato-thalamo-cortical (CSTC) circuitry was investigated. Both mirth-inducing and non-mirth-inducing VC/VS DBS consistently resulted (conjunction, global null, family-wise error-corrected P < 0.05) in activation of amygdala, ventral striatum, and mediodorsal thalamus. However, only mirth-inducing DBS resulted in functional inhibition of anterior cingulate cortex. Dynamic causal modeling revealed that mirth-inducing DBS enhanced effective connectivity from anterior cingulate to ventral striatum, while attenuating connectivity from thalamus to ventral striatum relative to non-mirth-inducing stimulation. These results suggest that DBS-evoked mood elevation is accompanied by distinct patterns of limbic thalamocortical connectivity. Using the novel combination of DBS-evoked mood alteration and functional MRI in human subjects, we provide new insights into the network-level mechanisms that influence affect.

Magnetic resonance imaging–guided laser interstitial thermal therapy for previously treated hypothalamic hamartomas

OBJECTIVE

Hypothalamic hamartomas (HHs) are associated with gelastic seizures and the development of medically refractory epilepsy. Magnetic resonance imaging–guided laser interstitial thermal therapy (MRg-LITT) is a minimally invasive ablative treatment that may have applicability for these deep-seated lesions. Here, the authors describe 3 patients with refractory HHs who they treated with MRg-LITT.

METHODS

An institutional review board–approved prospective database of patients undergoing Visualase MRg-LITT was retrospectively reviewed. Demographic and historical medical data, including seizure and medication histories, previous surgeries, procedural details, and surgical complications, along with radiological interpretation of the HHs, were recorded. The primary outcome was seizure freedom, and secondary outcomes included medication reduction, seizure frequency, operative morbidity, and clinical outcome at the latest follow-up.

RESULTS

All 3 patients in the multi-institutional database had developed gelastic seizures related to HH at the ages of 7, 7, and 9 years. They presented for further treatment at 25, 28, and 48 years of age, after previous treatments with stereotactic radiosurgery in all cases and partial hamartoma resection in one case. One ablation was complicated by a small tract hemorrhage, which was stable on postoperative imaging. One patient developed hyponatremia and experienced weight gain, which were respectively managed with fluid restriction and counseling. At the most recent follow-up at a mean of 21 months (range 1–32 months), one patient was seizure free while another had meaningful seizure reduction. Medication was reduced in one case.

CONCLUSIONS

Adults with gelastic seizures despite previous treatments can undergo MRg-LITT with reasonable safety and efficacy. This novel therapy may provide a minimally invasive alternative for primary and recurrent HH as the technique is refined.

MRI-guided Wire Localization Surgical Biopsy in an Adolescent Patient with a Difficult to Diagnose Case of Lymphoma

A 17-year-old previously healthy female presented with a progressive soft tissue infiltrative process involving the neck and thorax. Extensive diagnostic evaluation including multiple imaging, laboratory, and biopsy studies was nondiagnostic. Due to an urgent need to establish a diagnosis and several previous nondiagnostic biopsies, she was referred to interventional radiology for MRI-guided wire localization immediately prior to open surgical biopsy. Under general anesthesia, wires were placed in the areas of increased T2 signal within the bilateral splenius capitis muscles using intermittent MRI-guidance followed by immediate surgical biopsy down to the wires. Pathology confirmed the diagnosis of diffuse large B-cell lymphoma.

Fibroid interventions: reducing symptoms today and tomorrow: extending generalizability by using a comprehensive cohort design with a randomized controlled trial

BACKGROUND

Uterine fibroids are an important source of morbidity for reproductive-aged women. Despite an increasing number of alternatives, hysterectomies account for about 75% of all fibroid interventional treatments. Evidence is lacking to help women and their health care providers decide among alternatives to hysterectomy. Fibroid Interventions: Reducing Symptoms Today and Tomorrow (NCT00995878, clinicaltrials.gov) is a randomized controlled trial to compare the safety, efficacy, and economics of 2 minimally invasive alternatives to hysterectomy: uterine artery embolization and magnetic resonance imaging-guided focused ultrasound surgery. Although randomized trials provide the highest level of evidence, they have been difficult to conduct in the United States for interventional fibroid treatments. Thus, contemporaneously recruiting women declining randomization may have value as an alternative strategy for comparative effectiveness research.

OBJECTIVE

We sought to compare baseline characteristics of randomized participants with nonrandomized participants meeting the same enrollment criteria and to determine whether combining the 2 cohorts in a comprehensive cohort design would be useful for analysis.

STUDY DESIGN

Premenopausal women with symptomatic uterine fibroids seeking interventional therapy at 3 US academic medical centers were randomized (1:1) in 2 strata based on calculated uterine volume (<700 and ≥700 cc(3)) to undergo embolization or focused ultrasound surgery. Women who met the same inclusion criteria but declined randomization were offered enrollment in a parallel cohort. Both cohorts were followed up for a maximum of 36 months after treatment. The measures addressed in this report were baseline demographics, symptoms, fibroid and uterine characteristics, and scores on validated quality-of-life measures.

RESULTS

Of 723 women screened, 57 were randomized and 49 underwent treatment (27 with focused ultrasound and 22 with embolization). Seven of the 8 women randomized but not treated were assigned to embolization. Of 34 women in the parallel cohort, 16 elected focused ultrasound and 18 elected embolization. Compared with nonrandomized participants, randomized participants had higher mean body mass index (28.7 vs 25.3 kg/m(2); P = .01) and were more likely to be gravid (77% vs 47%; P = .003) and smokers (42% vs 12%; P = .003). Age, race, uterine volume, number of fibroids, and baseline validated measures of general and disease-specific quality of life, pain, depression, and sexual function did not differ between the groups. When we performed a comprehensive cohort analysis and analyzed by treatment arm, the only baseline difference observed was a higher median McGill Pain Score among women undergoing focused ultrasound (10.5 vs 6; P = .03); a similar but nonsignificant trend was seen in visual analog scale scores for pain (median, 39.0 vs 24.0; P = .06).

CONCLUSION

Using a comprehensive cohort analysis of study data could result in additional power and greater generalizability if results are adjusted for baseline differences.

MRI-Guided Prostate Biopsy of Native and Recurrent Prostate Cancer

Prostate cancer is the most commonly diagnosed noncutaneous cancer and second-leading cause of death in men. Many patients with clinically organ-confined prostate cancer undergo definitive, curative treatment of the whole gland with either radical prostatectomy or radiation therapy. However, many men are reluctant to take the definitive step due to potential morbidity associated with either therapy. A growing interest in active surveillance or focal therapy has emerged as realistic alternatives for many patients. With each of these management strategies, it is critical to accurately quantify and stage the cancer with improved biopsy targeting and more precise imaging with magnetic resonance imaging (MRI). Furthermore, having dependable prostate imaging allows for targeted biopsies to improve the yield of clinically significant prostate cancer and decrease detection of indolent prostate cancer. MRI-guided targeted biopsy techniques include cognitive MRI/transrectal ultrasound fusion biopsy, in-bore transrectal targeted biopsy using a calibrated guidance device, and in-bore direct MR-guided transperineal biopsy with a software-based transperineal grid template. Herein we present a contemporary review of MRI-guided targeted biopsy techniques for new and recurrent cancerous foci of the prostate.

Motor and Nonmotor Circuitry Activation Induced by Subthalamic Nucleus Deep Brain Stimulation in Patients With Parkinson Disease: Intraoperative Functional Magnetic Resonance Imaging for Deep Brain Stimulation

OBJECTIVE

To test the hypothesis suggested by previous studies that subthalamic nucleus (STN) deep brain stimulation (DBS) in patients with Parkinson disease would affect the activity of motor and nonmotor networks, we applied intraoperative functional magnetic resonance imaging (fMRI) to patients receiving DBS.

PATIENTS AND METHODS

Ten patients receiving STN DBS for Parkinson disease underwent intraoperative 1.5-T fMRI during high-frequency stimulation delivered via an external pulse generator. The study was conducted between January 1, 2013, and September 30, 2014.

RESULTS

We observed blood oxygen level-dependent (BOLD) signal changes (false discovery rate <0.001) in the motor circuitry (including the primary motor, premotor, and supplementary motor cortices; thalamus; pedunculopontine nucleus; and cerebellum) and in the limbic circuitry (including the cingulate and insular cortices). Activation of the motor network was observed also after applying a Bonferroni correction (P<.001) to the data set, suggesting that across patients, BOLD changes in the motor circuitry are more consistent compared with those occurring in the nonmotor network.

CONCLUSION

These findings support the modulatory role of STN DBS on the activity of motor and nonmotor networks and suggest complex mechanisms as the basis of the efficacy of this treatment modality. Furthermore, these results suggest that across patients, BOLD changes in the motor circuitry are more consistent than those in the nonmotor network. With further studies combining the use of real-time intraoperative fMRI with clinical outcomes in patients treated with DBS, functional imaging techniques have the potential not only to elucidate the mechanisms of DBS functioning but also to guide and assist in the surgical treatment of patients affected by movement and neuropsychiatric disorders.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01809613.

Use of a radio frequency shield during 1.5 and 3.0 Tesla magnetic resonance imaging: experimental evaluation

Radiofrequency (RF) shields have been recently developed for the purpose of shielding portions of the patient’s body during magnetic resonance imaging (MRI) examinations. We present an experimental evaluation of a commercially available RF shield in the MRI environment. All tests were performed on 1.5 T and 3.0 T clinical MRI scanners. The tests were repeated with and without the RF shield present in the bore, for comparison. Effects of the shield, placed within the scanner bore, on the RF fields generated by the scanner were measured directly using tuned pick-up coils. Attenuation, by as much as 35 dB, of RF field power was found inside the RF shield. These results were supported by temperature measurements of metallic leads placed inside the shield, in which no measurable RF heating was found. In addition, there was a small, simultaneous detectable increase (∼1 dB) of RF power just outside the edges of the shield. For these particular scanners, the autocalibrated RF power levels were reduced for scan locations prescribed just outside the edges of the shield, which corresponded with estimations based on the pick-up coil measurements. Additionally, no significant heating during MRI scanning was observed on the shield surface. The impact of the RF shield on the RF fields inside the magnet bore is likely to be dependent on the particular model of the RF shield or the MRI scanner. These results suggest that the RF shield could be a valuable tool for clinical MRI practices.

Incidence of additional treatments in women treated with MR-guided focused US for symptomatic uterine fibroids: review of 138 patients with an average follow-up of 2.8 years

PURPOSE

To assess long-term outcomes of magnetic resonance (MR)-guided focused ultrasound (US) treatments of uterine fibroids.

MATERIALS AND METHODS

A retrospective follow-up of 138 patients treated at a single institution between March 2005 and November 2011 was conducted. The patients were not part of a clinical study and were followed through retrospective review of their medical records and telephone interviews to assess additional treatments for fibroid-related symptoms. Survival methods, including Cox proportional hazards models, were used to assess the association between incidence of additional treatments and patient data obtained during screening before treatment.

RESULTS

The average length of follow-up was 2.8 years (range, 1-7.2 y). The cumulative incidence of additional treatments at 36 months and 48 months after MR-guided focused US was 19% and 23%, respectively. Women who did not need additional treatment were older than women who did (46.3 y ± 5.6 vs 43.0 y ± 5.8; P = .006; hazard ratio, 0.855; 95% confidence interval, 0.789-0.925). Additionally, women with heterogeneous or bright fibroids on T2-weighted MR imaging were more likely to require additional treatment compared with women with homogeneously dark fibroids (hazard ratio, 5.185 or 5.937, respectively; 95% confidence interval, 1.845-14.569 or 1.401-25.166, respectively). Physician predictions of treatment success, recorded during the screening process, had significant predictive value (P = .018).

CONCLUSIONS

The long-term rates of additional interventions after MR-guided focused US of symptomatic uterine fibroids were found to be comparable with other uterine-sparing procedures, such as uterine artery embolization or myomectomy. Older patient age and homogeneously dark fibroids were associated with fewer additional treatments. Physician assessment of treatment success was found to be a valuable tool in patient screening.

Clinical predictors of successful magnetic resonance-guided focused ultrasound (MRgFUS) for uterine leiomyoma

Background

Magnetic resonance-guided focused ultrasound (MRgFUS) is a relatively new minimally invasive treatment, approved by the US Food and Drug Administration in 2004 for treatments of symptomatic uterine leiomyomas (fibroids). The purpose of this work is to present retrospective cohort analysis of women that underwent commercial MRgFUS treatment between 2005 and 2009 at a single center, to identify baseline patient characteristics that predict successful MRgFUS fibroid treatment. Identifying these clinical predictors of MRgFUS would be helpful to clinicians choosing the optimal patient for this treatment modality.

Methods

One hundred thirty women with symptomatic uterine leiomyomas who underwent MRgFUS were followed up with a mean length of follow up of 17.4 ± 10.3 months. The main outcome measure of the follow-up was to identify patients who required additional fibroid treatment due to continued fibroid symptoms. Additionally, patient medical history and radiological findings obtained prior to MRgFUS were reviewed, and statistical analysis was performed to identify factors associated with reduced risk of having additional fibroid treatment.

Results

Twenty-nine patients (22.3%) underwent additional fibroid treatment due to continued or recurrent fibroid symptoms during the follow up. Cumulative incidence of additional fibroid treatment was 9.7%, 29.3%, and 44.7% at 1, 2, and 3 years following MRgFUS, respectively. In multivariable Cox proportional hazard regression analyses, older age (hazard ratio (HR) 0.54 per 5-year increase in age, 95% confidence interval 0.39 to 0.76, p < 0.001), greater number of fibroids (HR 0.19 for more than three vs. one fibroid, 95% CI 0.05 to 0.67, p = 0.033), and greater fibroid volume (HR 0.70 per doubling in volume, 95% CI 0.51 to 0.96, p = 0.025) were significantly associated with less risk of having additional fibroid treatment.

Conclusions

Older age at treatment and having multiple fibroids with larger volume are associated with a lower risk of additional intervention following MRgFUS treatment for uterine fibroids.

Magnetic resonance imaging-guided cryoablation of recurrent prostate cancer after radical prostatectomy: initial single institution experience

OBJECTIVE

To establish the feasibility of magnetic resonance imaging (MRI)-guided cryoablation in patients with previous radical prostatectomy and MRI visualized biopsy-proven local recurrence of prostate adenocarcinoma.

MATERIALS AND METHODS

Eighteen postprostatectomy patients (mean 67, 57-78 years) were treated with MRI-guided cryoablation for recurrent prostate carcinoma. Patients were found to have a hyperenhancing nodule using multiparametric MRI with endorectal coil followed by a positive transrectal ultrasound-guided biopsy. Of 18 postsurgical patients, 6 had additional salvage external beam radiation with subsequent recurrence. Under general anesthesia and MRI guidance (wide-bore 1.5T MRI), 2-5 cryotherapy probes were placed in or around the recurrence by transperineal approach and cryoablation performed. The patients were stratified into 2 groups: the initial 9 consecutive patients had cryoprobes placed 1 cm apart with 2 freeze-thaw cycles (group 1), and the subsequent 9 patients had cryoprobes placed 0.5 cm apart with 3 freeze-thaw cycles (group 2).

RESULTS

In group I, the average preprocedure prostate-specific antigen (PSA) was 1.21 ± 1.12 ng/mL, and 1-3 months postprocedure PSA was 0.14 ± 0.11 ng/mL (P <.01). Sixty-seven percent of patients had PSA ≤0.2 ng/mL at 1-3 months follow-up, but only 25% at 4-6 months. No change in impotence or incontinence occurred. In group II, average preprocedure PSA was 2.24 ± 2.71 ng/mL, and 1-3 month postprocedure PSA was 0.08 ± 0.10 ng/mL (P <.05). Eighty-nine percent of patients had PSA ≤0.2 ng/mL at 1-3 months follow-up and at 4-6 months. Complications in group 2 included worsening incontinence in 3 patients.

CONCLUSION

MRI-guided salvage cryoablation of postradical prostatectomy prostate cancer recurrence is safe and feasible. Both techniques produce early PSA decrease with more lasting PSA results in the more aggressive group II methodology.

3.0T MR-guided laser ablation of a prostate cancer recurrence in the postsurgical prostate bed

Biochemical recurrence of prostate cancer after definitive therapy with radical prostatectomy occurs in 25%-30% of cases. The first known case of magnetic resonance (MR) imaging-guided ablation using laser interstitial thermal therapy (LITT) for locally recurrent prostate cancer after radical prostatectomy is presented. Using 3.0T MR guidance, two laser applicators were placed via a transperineal approach. Laser ablation was performed using MR thermometry to determine the ablation endpoint and lesion coverage. Dynamic contrast-enhanced MR imaging after the procedure showed no definitive abnormal enhancement. The patient had no change in continence or potency after the procedure.

Four-year experience with a clinical ultrasound quality control program

Ultrasound (US) quality control (QC) program data over a 4-year period from more than 45 scanners and more than 265 transducers were reviewed to optimize the program in terms of efficiency and effectiveness. Our program included evaluations of mechanical integrity, image uniformity, distance measurement accuracy and maximum depth of penetration (DOP). We computed failure rates and fraction of failures detected by each test. A total of 187 equipment problems were identified. Average annual scanner component and transducer failure rates were 10.5% and 13.9%, respectively. The mechanical integrity and uniformity evaluations detected 25.1% and 66.3% of all failures, respectively. Those evaluations plus defects detected by sonographers accounted for 98.4% of all detected failures. DOP and distance measurement accuracy were not effective at detecting equipment failures. For routine US QC, we recommend quarterly mechanical integrity and uniformity assessments of all transducers. A scanner with five transducers could be tested in an estimated 30 min or less.

Magnetic resonance-guided focused ultrasound surgery for leiomyoma-associated infertility

OBJECTIVE

To describe magnetic resonance-guided focused ultrasound surgery (FUS) as a treatment for a case of leiomyoma-associated infertility.

DESIGN

Case report from a randomized clinical trial.

SETTING

Academic medical center.

PATIENT(S)

A 37-year-old woman with known leiomyomas and a history of 18 months of home-inseminations from a known donor.

INTERVENTION(S)

Magnetic resonance-guided FUS treatment of uterine fibroids, where the dominant fibroid distorted the uterine cavity.

MAIN OUTCOME MEASURE(S)

Pregnancy.

RESULT(S)

A viable intrauterine pregnancy, with a full-term vaginal delivery, was conceived after a single clomiphene citrate and intrauterine insemination cycle.

CONCLUSION(S)

The role of FUS for enhancement of fertility in women with nonhysteroscopically resectable uterine fibroids distorting the uterine cavity should be investigated further.

Magnetic resonance-guided focused ultrasound of uterine leiomyomas: review of a 12-month outcome of 130 clinical patients

PURPOSE

To assess 12-month outcomes and safety of clinical magnetic resonance (MR)-guided focused ultrasound (US) treatments of uterine leiomyomas.

MATERIALS AND METHODS

Between March 2005 and December 2009, 150 women with symptomatic uterine leiomyomas were clinically treated with MR-guided focused US at a single institution; 130 patients completed treatment and agreed to have their data used for research purposes. Patients were followed through retrospective review of medical records and phone interviews conducted at 3-, 6-, and 12-month intervals after treatment to assess additional procedures and symptom relief. Outcome measures and treatment complications were analyzed for possible correlations with the appearance of the tumors on T2-weighted imaging.

RESULTS

The cumulative incidence of additional tumor-related treatments 12 months after MR-guided focused US was 7.4% by the Kaplan-Meier method. At 3-, 6-, and 12-month follow-up, 86% (90 of 105), 93% (92 of 99), and 88% (78 of 89) of patients reported relief of symptoms, respectively. No statistically significant correlation between tumor appearance on T2-weighted imaging and 12-month outcome was found. Treatment-related complications were observed in 17 patients (13.1%): 16 patients had minor complications and one had a major complication (deep vein thrombosis). All complications were resolved within the 12-month follow-up period.

CONCLUSIONS

MR-guided focused US is a noninvasive treatment option that can be used to effectively and safely treat uterine leiomyomas and delivers significant and lasting symptom relief for at least 12 months. The incidence of additional treatment during this time period is comparable with those in previous reports of uterine artery embolization.

Calorimetric calibration of head coil SAR estimates displayed on a clinical MR scanner

Calorimetric measurements were performed to determine the average specific absorption rates (SAR) resulting from MRI head examinations. The data were compared with average head coil SAR estimates displayed by the MR scanner in order to refine the imaging protocols used in imaging patients with implanted deep brain stimulators (DBS). The experiments were performed using transmit-receive (TR) head coil on clinical 1.5 T General Electric MR scanners running 11.0 M4 revision software. The average applied SAR was derived from temperature increases measured inside a head phantom, due to deposition of RF energy during MRI scanning with a spin echo imaging sequence. The measurements were repeated for varied levels of RF transmit gain (TG) and analyzed with a range of entered patient weights. The measurements demonstrate that the ratio of the actual average head SAR to the scanner-displayed value (coil correction factor) decreases for decreasing TG or for increasing patient weight and may vary between 0.3 and 2.1. An additional retrospective patient study, however, shows that not all combinations of TG and patient weight are encountered clinically and, instead, TG generally increases with the patient weight. As a result, a much narrower range of coil correction factors (e.g., typically 0.5-1.0) will be encountered in practice. The calorimetric method described in this work could aid the physicians and technologists in refinement of the model-dependent SAR estimates displayed by the MR scanner, and in selection of imaging parameters for MR head examinations within allowable SAR safety levels.

Preliminary assessment of one-dimensional MR elastography for use in monitoring focused ultrasound therapy

The purpose of this work is to assess a fast technique that measures tissue stiffness and temperature during focused ultrasound thermal therapy (FUS). A one-dimensional (1D) MR elastography (MRE) pulse sequence was evaluated for the purpose of obtaining rapid measurements of thermally induced changes in tissue stiffness and temperature for monitoring FUS treatments. The accuracy of the 1D measurement was studied by comparing tissue displacements measured by 1D MRE with those measured by the well-established 2D MRE pulse sequence. The reproducibility of the 1D MRE measurement was assessed, in gel phantoms and ex vivo porcine tissue, for varied FUS intensity levels (31.5-199.9 W cm(-2)) and over a range of displacements at the focus (0.1-1 microm). Temperature elevations in agarose gel phantoms were measured using 1D MRE and calibrated using fiberoptic-thermometer-based measurements. The 1D MRE displacement measurements are highly correlated with those obtained with the 2D technique (R(2) = 0.88-0.93), indicating that 1D MRE can successfully measure tissue displacement. Ten repeated trials at each FUS power level yielded a minimum detectable displacement change of 0.2 microm in phantoms and 0.4 microm in tissue (at 95% confidence level). The 1D MRE temperature measurements correlated well with temperature changes measured simultaneously with fiberoptic thermometers (R(2) = 0.97). The 1D MRE technique is capable of detecting tissue displacements as low as 0.4 microm, which is an order of magnitude smaller than 5 microm displacements expected during FUS therapy (Le et al 2005 AIP Conf. Proc.: Ther. Ultrasound 829 186-90). Additionally, 1D MRE was shown to provide adequate measurements of temperature elevations in tissue. These findings indicate that 1D MRE may be an effective tool for monitoring FUS treatments.