An Investigation to Dissociate the Analgesic and Anesthetic Properties of Ketamine Using Functional Magnetic Resonance Imaging

Background: Anatomic sites within the brain, which activate in response to noxious stimuli, can be identified with the use of functional magnetic resonance imaging. The aim of this study was to determine whether the analgesic effects of ketamine could be imaged.

Methods: Ketamine was administered to eight healthy volunteers with use of a target-controlled infusion to three predicted plasma concentrations: 0 (saline), 50 (subanalgesic), and 200 ng/ml (analgesic, subanesthetic). Volunteers received noxious thermal stimuli and auditory stimuli and performed a motor task within a 3-T human brain imaging magnet. Activation of brain regions in response to noxious and auditory stimuli and during the motor task was compared with behavioral measures.

Results: The analgesic subanesthetic dose of ketamine significantly reduced the pain scores, and this matched a decrease in activity within brain regions that activate in response to noxious stimuli, in particular, the insular cortex and thalamus. A different pattern of activation was observed in response to an auditory task. In comparison, smaller behavioral and imaging changes were found for the motor paradigm. The lower dose of ketamine gave similar but smaller nonsignificant effects.     

Early Decay of Pain-related Cerebral Activation in Functional Magnetic Resonance Imaging: Comparison with Visual and Motor Tasks

Background: Although pain-related activation was localized in multiple brain areas by functional imaging, the temporal profile of its signal has been poorly understood. The authors characterized the temporal evolution of such activation in comparison to that by conventional visual and motor tasks using functional magnetic resonance imaging.

Methods: Five right-handed volunteers underwent whole brain echo-planar imaging on a 3 T magnetic resonance imaging scanner while they received pain stimulus on the right and left forearm and performed visually guided saccade and finger tapping tasks. Pain stimulus on the right and left forearm consisted of four cycles of 15-s stimulus at 47.2-49.0[degrees]C, interleaved with 30-s control at 32[degrees]C, delivered by a Peltier-type thermode, and visually guided saccade and finger tapping of three cycles of 30-s active and 30-s rest conditions. Voxel-wise t statistical maps were standardized and averaged across subjects. Blood oxygenation level-dependent signal time courses were analyzed at local maxima of representative activation clusters (t > 3.5).

Results: Pain stimulus on the right forearm activated the secondary somatosensory (S2), superior temporal, anterior cingulate, insular, prefrontal cortices, premotor area, and lenticular nucleus. Pain stimulus on the left forearm activated similar but fewer areas at less signal intensity. The S2 activation was dominant on the contralateral hemisphere. Pain-related activation was statistically weaker and showed less consistent signal time courses than visually guided saccade- and finger tapping-related activation. Pain-related signals decayed earlier before the end of stimulus, in contrast to well-sustained signal plateaus induced by visually guided saccade and finger tapping.     

Functional Magnetic Resonance Imaging in Prostate Cancer

Context

Magnetic resonance imaging (MRI) combined with magnetic resonance spectroscopy imaging (MRSI), dynamic contrast-enhanced MRI, and diffusion-weighted MRI emerged as promising tests in the diagnosis of prostate cancer, and they show encouraging results.

Objective

This review emphasizes different functional MRI techniques in the diagnosis of prostate cancer and includes information about their clinical value and usefulness.

Evidence acquisition

The authors searched the Medline, Embase, and Cochrane Library databases. There were no language restrictions. The last search was performed in October 2008.

Evidence synthesis

The combination of conventional MRI with functional MRI techniques is more reliable for differentiating benign and malignant prostate tissues than any other diagnostic procedure. At present, no guideline is available that outlines which technique is best in a specific clinical situation. It also remains uncertain whether improved spatial resolution and signal-to-noise ratio of 3-T MRI will improve diagnostic performance.

Conclusions

A limited number of small studies suggest that functional MRI may improve the diagnosis and staging of prostate cancer. This finding needs further confirmation in larger studies, and cost-effectiveness needs to be established.     

Dissociable Brain Activation Responses to 5-Hz Electrical Pain Stimulation: A High-field Functional Magnetic Resonance Imaging Study

Background: To elucidate neural correlates associated with processing of tonic aching pain, the authors used high-field (3-T) functional magnetic resonance imaging with a blocked parametric study design and characterized regional brain responses to electrical stimulation according to stimulus intensity-response functions.

Methods: Pain was induced in six male volunteers using a 5-Hz electrical stimulus applied to the right index finger. Scanning sequences involved different levels of stimulation corresponding to tingling sensation (P1), mild pain (P2), or high pain (P3). Common effects across subjects were sought using a conjunction analyses approach, as implemented in statistical parametric mapping (SPM-99).

Results: The contralateral posterior/mid insula and contralateral primary somatosensory cortex were most associated with encoding stimulus intensity because they showed a positive linear relation between blood oxygenation level-dependent signal responses and increasing stimulation intensity (P1 < P2 < P3). The contralateral secondary somatosensory cortex demonstrated a response function most consistent with a role in pain intensity encoding because it had no significant response during the innocuous condition (P1) but proportionally increased activity with increasingly painful stimulus intensities (0 < P2 < P3). Finally, a portion of the anterior cingulate cortex (area 24) and supplementary motor area 6 demonstrated a high pain-specific response (P3).     

Imaging Prostate Cancer: An Update on Positron Emission Tomography and Magnetic Resonance Imaging

Prostate cancer is a common cancer in men and continues to be a major health problem. Imaging plays an essential role in the clinical management of patients. An important goal for prostate cancer imaging is more accurate disease characterization through the synthesis of anatomic, functional, and molecular imaging information. Developments in imaging technologies, specifically magnetic resonance imaging (MRI) and positron emission tomography (PET)/computed tomography (CT), have improved the detection rate of prostate cancer. MRI has improved lesion detection and local staging. Furthermore, MRI allows functional assessment with techniques such as diffusion-weighted MRI, MR spectroscopy, and dynamic contrast-enhanced MRI. The most common PET radiotracer, ¹⁸F-fluorodeoxyglucose, is not very useful in prostate cancer. However, in recent years other PET tracers have improved the accuracy of PET/CT imaging of prostate cancer. Among these, choline (labeled with ¹⁸F or ¹¹C), ¹¹C-acetate, and ¹⁸F-fluoride have demonstrated promising results, and other new radiopharmaceuticals are currently under evaluation in preclinical and clinical studies.     

Motor Mapping with Functional Magnetic Resonance Imaging: Comparison with Electrical Cortical Stimulation

The aim of the present study was to evaluate motor area mapping using functional magnetic resonance imaging (fMRI) compared with electrical cortical stimulation (ECS). Motor mapping with fMRI and ECS were retrospectively compared in seven patients with refractory epilepsy in which the primary motor (M1) areas were identified by fMRI and ECS mapping between 2012 and 2019. A right finger tapping task was used for fMRI motor mapping. Blood oxygen level-dependent activation was detected in the left precentral gyrus (PreCG)/postcentral gyrus (PostCG) along the “hand knob” of the central sulcus in all seven patients. Bilateral supplementary motor areas (SMAs) were also activated (n = 6), and the cerebellar hemisphere showed activation on the right side (n = 3) and bilateral side (n = 4). Furthermore, the premotor area (PM) and posterior parietal cortex (PPC) were also activated on the left side (n = 1) and bilateral sides (n = 2). The M1 and sensory area (S1) detected by ECS included fMRI-activated PreCG/PostCG areas with broader extent. This study showed that fMRI motor mapping was locationally well correlated to the activation of M1/S1 by ECS, but the spatial extent was not concordant. In addition, the involvement of SMA, PM/PPC, and the cerebellum in simple voluntary movement was also suggested. Combination analysis of fMRI and ECS motor mapping contributes to precise localization of M1/S1.     

术前功能磁共振在脑功能区肿瘤切除中的应用

目的探讨术前功能磁共振（fMRI）在功能区肿瘤切除中的临床应用价值。方法10例肿瘤邻近脑运动功能区患者，平均51．3岁，7例肢体无力，2例抽搐，1例口角偏斜，术前Karnofsky评分平均82分。常规行头颅核磁增强扫描，证实肿瘤位于功能区，再行fMRI检查。依据fMRI中活化区与肿瘤的位置关系决定全切或者次全切除肿瘤，术中避免活化区的损伤。术后观察肢体肌力恢复情况、进行术后Karnofsky评分并复查核磁了解术后肿瘤切除情况，与术前进行对比。结果10例fMRI活化区显示清晰，8例活化区被肿瘤挤压移位，拉伸变形。肿瘤边缘与活化区的最近距离0～26mm，平均13．6mm。本组肿瘤全切7例，次全切除3例。术后肌力好转7例，2例抽搐患者术后未再出现抽搐；1例口角歪斜患者术后面神经功能分级减轻。术后1个月Karnofsky评分平均93分。术后1周复查MRI显示：肿瘤消失7例，余3例肿瘤缩小95％～99％。结论fMRI对邻近脑运动功能区肿瘤患者的术前评价有重要临床意义，对手术切除脑功能区周围肿瘤并保留运动功能有重要的指导作用。     

股骨头坏死的系列MRI表现

目的观察系列MRI上股骨头坏死的坏死信号和坏死面积比例变化。方法自1997年至2005年5月,根据股骨头坏死的诊断标准,对10例(20髋)具有两次及以上MRI成像的股骨头坏死进行研究,两次MRI成像平均相差18.1个月,观察其坏死信号和坏死面积比例变化。结果两次MRI检查时,均有180个层面,共有38个层面出现信号改变。在无外科干预及软骨下骨折出现的11髋102个层面中,5个层面发生信号改变;在行髓芯减压治疗的6髋和出现软骨下骨折的3髋78个层面中,33个层面发生信号改变,P=0.000,具有显著统计学差异。第一次MRI检查时的平均坏死面积比例为(52.62±17.90)%;第二次MRI检查时的平均坏死面积比例为(52.24±19.39)%,P=0.687,两者无显著性差异。结论股骨头坏死的坏死面积比例不随病程的延长及临床分期的进展而改变。如无外科干预或软骨下骨折出现,股骨头坏死的信号强度也无明显变化。     

Magnetic Resonance Imaging of Shoulder Arthroplasty

Background

Magnetic resonance (MR) imaging evaluation of the painful failed shoulder arthroplasty is a useful imaging modality due to advancements in metal artifact reduction techniques, which allow assessment of the integrity of the supporting soft-tissue envelope and the implant.

Questions/Purposes

The focus of this pictorial review is to illustrate the benefits of MR imaging, whether used alone or as an adjunct to other imaging modalities, in aiding the clinician in the complex decision making process.

Methods

A PubMed (MEDLINE) search focusing on the complications and imaging assessment of shoulder arthroplasty was performed. Articles were selected for review based on their pertinence to the aforementioned topics.

Results

We discuss the ability of MR imaging to identify why a patient’s arthroplasty may have failed. Specific causes including component loosening and implant failure, rotator cuff and deltoid integrity, infection, subtle fractures, and nerve pathology are reviewed, with illustrative sample images.

Conclusion

MRI is a valuable tool in the assessment for pathology in the shoulder following arthroplasty.

Electronic supplementary material

The online version of this article (doi:10.1007/s11420-014-9399-3) contains supplementary material, which is available to authorized users.