7T MR of intracranial pathology: Preliminary observations and comparisons to 3T and 1.5T.

PURPOSE: There have been an increasing number of studies involving ultra-high-field 7T of intracranial pathology, however, comprehensive clinical studies of neuropathology at 7T still remain limited. 7T has the advantage of a higher signal-to-noise ratio and a higher contrast-to-noise ratio, compared to current low field clinical MR scanners. We hypothesized 7T applied clinically, may improve detection and characterization of intracranial pathology. MATERIALS AND METHODS: We performed an IRB-approved 7T prospective study of patients with neurological disease who previously had lower field 3T and 1.5T. All patients underwent 7T scans, using comparable clinical imaging protocols, with the aim of qualitatively comparing neurological lesions at 7T with 3T or 1.5T. To qualitatively assess lesion conspicuity at 7T compared with low field, 80-paired images were viewed by 10 experienced neuroradiologists and scored on a 5-point scale. Inter-rater agreement was characterized using a raw percent agreement and mean weighted kappa. RESULTS: One-hundred and four patients with known neurological disease have been scanned to date. Fifty-five patients with epilepsy, 18 patients with mild traumatic brain injury, 11 patients with known or suspected multiple sclerosis, 9 patients with amyotrophic lateral sclerosis, 4 patients with intracranial neoplasm, 2 patients with orbital melanoma, 2 patients with cortical infarcts, 2 patients with cavernous malformations, and 1 patient with cerebral amyloid angiopathy. From qualitative observations, we found better resolution and improved detection of lesions at 7T compared to 3T. There was a 55% raw inter-rater agreement that lesions were more conspicuous on 7T than 3T/1.5T, compared with a 6% agreement that lesions were more conspicuous on 3T/1.5T than 7T. CONCLUSION: Our findings show that the primary clinical advantages of 7T magnets, which include higher signal-to-noise ratio, higher contrast-to-noise ratio, smaller voxels and stronger susceptibility contrast, may increase lesion conspicuity, detection and characterization compared to low field 1.5T and 3T. However, low field which detects a plethora of intracranial pathology remains the mainstay for diagnostic imaging until limitations at 7T are addressed and further evidence of utility provided.

Feasibility of Magnetic Resonance-Compatible Accelerometers to Monitor Tremor Fluctuations During Magnetic Resonance-Guided Focused Ultrasound Thalamotomy: Technical Note.

BACKGROUND: Magnetic resonance-guided focused ultrasound (MRgFUS) thalamotomy is used to treat essential tremor and tremor-dominant Parkinson disease. Feedback is collected throughout the procedure to verify the location of the target and completeness of response; however, variability in clinical judgments may underestimate or overestimate treatment response. OBJECTIVE: To objectively quantify joint motion after each sonication using accelerometers secured to the contralateral upper extremity in an effort to optimize MRgFUS treatment. METHODS: Before the procedure, 3 accelerometers were secured to the patient's arm, forearm, and index finger. Throughout the procedure, tremor motion was regularly recorded during postural and kinetic tremor testing and individual joint angle measures were modeled. The joint angle from each accelerometer was compared with baseline measurements to assess changes in angles. Subsequent adjustments to the target location and sonication energy were made at the discretion of the neurosurgeon and neuroradiologist. RESULTS: Intraoperative accelerometer measurements of hand tremor from 18 patients provided quantified data regarding joint angle reduction: 87.3%, 94.2%, and 86.7% for signature writing, spiral drawing, and line drawing tests, respectively. Target adjustment based on accelerometer monitoring of the angle at each joint added substantial value toward achieving optimal tremor reduction. CONCLUSION: Real-time accelerometer recordings collected during MRgFUS thalamotomy offered objective quantification of changes in joint angle after each sonication, and these findings were consistent with clinical judgments of tremor response. These results suggest that this technique could be used for fine adjustment of the location of sonication energy and number of sonications to consistently achieve optimal tremor reduction.

Clinical Intervention Using Focused Ultrasound (FUS) Stimulation of the Brain in Diverse Neurological Disorders.

Various surgical techniques and pharmaceutical treatments have been developed to improve the current technologies of treating brain diseases. Focused ultrasound (FUS) is a new brain stimulation modality that can exert a therapeutic effect on diseased brain cells, with this effect ranging from permanent ablation of the pathological neural circuit to transient excitatory/inhibitory modulation of the neural activity depending on the acoustic energy of choice. With the development of intraoperative imaging technology, FUS has become a clinically available noninvasive neurosurgical option with visual feedback. Over the past 10 years, FUS has shown enormous potential. It can deliver acoustic energy through the physical barrier of the brain and eliminate abnormal brain cells to treat patients with Parkinson's disease and essential tremor. In addition, FUS can help introduce potentially beneficial therapeutics at the exact brain region where they need to be, bypassing the brain's function barrier, which can be applied for a wide range of central nervous system disorders. In this review, we introduce the current FDA-approved clinical applications of FUS, ranging from thermal ablation to blood barrier opening, as well as the emerging applications of FUS in the context of pain control, epilepsy, and neuromodulation. We also discuss the expansion of future applications and challenges. Broadening FUS technologies requires a deep understanding of the effect of ultrasound when targeting various brain structures in diverse disease conditions in the context of skull interface, anatomical structure inside the brain, and pathology.

Angiomyolipoma with minimal fat on MDCT: can counts of negative-attenuation pixels aid diagnosis?

OBJECTIVE: The purpose of this study was to determine whether counts of pixels with subzero attenuation on CT scans can aid in the diagnosis of renal angiomyolipoma with minimal fat. MATERIALS AND METHODS: Of 33 angiomyolipomas identified among 719 renal masses resected from 702 patients over 4 years, 15 masses in 15 patients were prospectively diagnosed on the basis of the presence of fat at MDCT. The 18 patients with minimal-fat angiomyolipoma and a matched (age, sex, tumor size) cohort of patients with renal cell carcinoma were included in this study. Three radiologists independently counted the number of pixels with attenuation less than -10, -20, and -30 HU. Receiver operating characteristic analysis of the number of pixels at each cutoff was used to calculate sensitivity, specificity, and positive predictive value with the following criteria: 1, more than 10 pixels less than -20 HU; 2, more than 20 pixels less than -20 HU; 3, more than 5 pixels less than -30 HU. RESULTS: Using criterion 1, reader A identified six angiomyolipomas; reader B, five; and reader C, two. The combined sensitivity was 24%; specificity, 98%; and positive predictive value, 69%. Using criterion 2, reader A identified three angiomyolipomas; reader B, four; and reader C, two. The combined sensitivity was 17%; specificity, 100%; and positive predictive value, 100%. Using criterion 3, reader A identified four angiomyolipomas; reader B, four; and reader C, two. The combined sensitivity was 18%; specificity, 100%; and positive predictive value, 100%. CONCLUSION: CT findings of more than 20 pixels with attenuation less than -20 HU and more than 5 pixels with attenuation less than -30 HU have a positive predictive value of 100% in detection of angiomyolipoma, but most angiomyolipomas with minimal fat cannot be reliably identified on the basis of an absolute pixel count.

Diagnostic imaging: radiation dose and patients' concerns.

Exposure to ionizing radiation during diagnostic radiologic procedures carries small but real risks, and children, young adults, and pregnant women are especially vulnerable. Exposure of patients to diagnostic energy levels of ionizing radiation should be kept to the minimum necessary to provide useful clinical information and allay patients' concerns about radiation-related risks.

Blue light generates reactive oxygen species (ROS) differentially in tumor vs. normal epithelial cells.

OBJECTIVES: Blue light of high intensity is commonly used in dentistry to activate polymerization of resin restorative materials. Other than its effects on the retina, the biological effects of blue light (380-500nm wavelengths) are poorly studied. Limited evidence suggests that blue light acts by forming intracellular reactive oxygen species (ROS) that then affect critical cell functions. If the biological effects of blue light are redox-mediated, antioxidants might be used to mitigate unwanted side effects of blue light during clinical use, or blue light might be used therapeutically to modulate redox-sensitive cell signaling responses. METHODS: Intracellular ROS were estimated using HFLUOR-DA (dihydrofluorescein diacetate), a vital fluorescein-based, redox-sensitive dye. ROS were measured in normal (NHEK) and oral squamous carcinoma (OSC2) epithelial cells, shown previously to respond differentially to blue light irradiation. Two-hour cumulative levels of ROS and approximate ROS lifetimes were measured after irradiation doses of 5-30 J/cm(2). The blue light-induced generation of ROS was further tested by the ability of the antioxidants N-acetylcysteine (NAC) and vitamin E to mitigate intracellular ROS levels. RESULTS: Dose-dependent ROS levels were generated in both NHEK and OSC2 cells, but cumulative levels were higher and persisted longer in the OSC2 cells. Both vitamin E and NAC significantly reduced blue-light-induced levels of ROS, but were more effective in the OSC2 cells. SIGNIFICANCE: The induction of intracellular ROS by blue light implies that redox effects may mediate cellular responses to blue light. This result suggests the opportunity to mitigate any effects of direct or coincident exposure during dental treatment via antioxidants, and the opportunity to exploit differences in redox processing among cells for possible treatment of epithelial cancer or wound healing.