Prospective evaluation of acute cerebral injury by DW-MRI following transcarotid artery revascularization using a double-layer micromesh stent.

BACKGROUND: Transcervical carotid artery revascularization (TCAR) has demonstrated a low overall stroke rate in carotid artery stenting (CAS). Furthermore, the use of a double-layer micromesh stent is expected to reduce embolization and plaque prolapse. The combination of TCAR and the double layer stent may lead to improved results compared to previously reported outcomes. The objective of this study is to present the findings of a prospective study including patients treated with the Roadsaver stent and TCAR. METHODS: Between January 2017 and May 2022, 85 patients were enrolled. Every patient underwent TCAR with the Roadsaver stent. As per our protocol, a neurological examination and an ultrasound were performed within 24 hours before and after the procedure, and again 30 days after. A diffusion-weighted magnetic resonance imaging (DW-MRI) was conducted 24 hours before the procedure and 48-72 hours after the procedure. The primary endpoint was the detection of new ischemic lesions on postoperative DW-MRI. The secondary endpoint was a composite of all strokes, death, and myocardial infarction within 30 days. RESULTS: Sixty-four patients (75.29%) were symptomatic, out of which 25 were treated within 14 days of the onset of the symptoms. Pre and postprocedural DW-MRI were performed in 83 patients. Postprocedural lesions were found in nine patients (10.84%). There were no strokes or death within 30 days, but two patients experienced a myocardial infarction. CONCLUSIONS: Our study suggests that the use of TCAR and the Roadsaver stent could be a safe alternative to carotid endarterectomy because it entails a low incidence of cerebral embolization, even in recently symptomatic and elderly patients.

Spinal cord infarction: aetiology, imaging findings, and prognostic factors in a series of 41 patients.

INTRODUCTION: Spinal cord infarction is a rare disease with a high rate of morbidity. Its diagnosis can be challenging and controversy remains regarding the best treatment. Few case series have been published. METHODS: We conducted a retrospective review of cases of spinal cord infarction attended in a tertiary hospital from 1999 to 2020. Aetiology and clinical, imaging, and prognostic features were assessed. RESULTS: Forty-one patients (58.5% men, mean [standard deviation] age 61 [17] years) were included in the study. Thirty-one patients (75.6%) presented vascular risk factors. Motor deficits were recorded in 39 (95.1%), pain in 20 (48.8%), sensory deficits in 33 (80.4%), and autonomic dysfunction in 24 (58.5%). MRI was performed in 37 (90.2%) patients. Diffusion-weighted images were available for 12 patients, with 10 showing diffusion restriction. The thoracic region was the most frequently affected (68.2%). Vascular imaging studies were performed in 33 patients (80.4%). The most frequent aetiologies were aortic dissection (6 cases), atherosclerosis demonstrated by vascular imaging (6 cases), fibrocartilaginous embolism (6 cases), surgery (5 cases), and hypotension (4 cases). Aetiology was undetermined in 12 patients (29.3%), although 9 of these presented vascular risk factors. At the end of the follow-up period (median, 24 months; interquartile range, 3-70), 12 patients (29.2%) were able to walk without assistance. Vascular risk factors and paraparesis were significantly associated with poorer prognosis (P < .05). DISCUSSION: Spinal cord infarction may present diverse aetiologies, with the cause remaining undetermined in many patients. Long-term functional prognosis is poor, and depends on baseline characteristics and clinical presentation. MRI, and especially diffusion-weighted sequences, is useful for early diagnosis.

Reversible Splenial Lesion Syndrome as a Challenging Casuistry.

The corpus callosum plays a vital role in brain function. In particular, in the trunk of the corpus callosum, in the course of various diseases, there may be temporary, reversible changes (reversible splenial lesion syndrome (RESLES)), as well as partially reversible and irreversible changes. This article discusses the differentiation of RESLES and other conditions with changes in the corpus callosum lobe, as well as the accompanying clinical symptoms. Moreover, a case report of a patient in whom the above changes appeared in the nuclear magnetic resonance (NMR) image is presented. A 20-year-old patient with the diagnosis of Ehlers-Danlos syndrome type VI was admitted to the psychiatric ward in an emergency because of psychomotor agitation, refusal to take food and fluids, delusional statements with a message, grandeur, and auditory hallucinations. In the performed magnetic resonance imaging (MRI) of the brain, the corpus callosum non-characteristic in T2-weighted images revealed a hyperintensive area, which was significantly hyperintensive in diffusion magnetic resonance (DWI) sequences and in apparent diffusion coefficient (ADC) sequences with reduced signal intensity and no signs of bleeding. The hypothesis of subacute ischemic stroke of the corpus callosum was presented. In the control MRI of the brain, changes in the corpus callosum completely regressed, thus excluding an ischemic etiology and favoring the diagnosis of RESLES. During hospitalization, the patient experienced significant fluctuations in mental status, with the dominant symptoms typical of the paranoid syndrome in the form of disturbances in the course and structure of thinking and perception, and a clear and stable improvement was obtained after the administration of long-acting intramuscular olanzapine. Taking into account the clinical and radiological picture, the age of the episode, the rapidity of the disease development, the persistence of its clinical symptoms after the withdrawal of radiological changes in the brain NMR image, as well as the significant improvement in the clinical condition after the introduction of antipsychotic drugs, the final diagnosis was made of schizophrenia.

Brain magnetic resonance imaging and histopathology findings in a dog with global brain ischaemia following cardiopulmonary arrest.

BACKGROUND: Global brain ischaemia following cardiopulmonary arrest is uncommonly reported in veterinary medicine yet neurologic injury after arrest is a known morbidity. CASE REPORT: An 18-week-old male entire Cavalier King Charles Spaniel-Poodle was referred following 3 days of neurologic abnormalities after cardiopulmonary arrest. After resuscitation, the animal had decerebrate rigidity, a stuporous mentation and intermittent episodes of vocalisation and apnoea. A brain magnetic resonance imaging (MRI) was undertaken 4 days after cardiopulmonary arrest, with standard sequences (T1-weighted, T2-weighted and fluid-attenuated inversion recovery) as well as diffusion-weighted imaging to better discern ischaemic injury and cytotoxic oedema for prognostic reasons. MRI findings were consistent with global brain ischaemia affecting the hippocampus, cerebellum and substantia nigra, the latter two not previously identified in canine cases of global brain ischaemia. The patient was euthanased on day eight post-cardiopulmonary arrest due to a lack of neurological improvement and developing sepsis as a complication. Ante-mortem identification of affected areas of the brain was confirmed on histological examination, with evidence of ischaemic injury seen in the cerebrum, hippocampus, cerebellum, basal nuclei and thalamus. CONCLUSION: This report describes ante-mortem MRI and postmortem findings in a dog with global brain ischaemia following cardiopulmonary arrest. A multimodal approach to neuroprognostication in patients recovering from cardiopulmonary arrest is recommended.

Plaque morphology effect on periprocedural asymptomatic cerebral embolism in carotid artery stenting using first-generation carotid stents: A diffusion-weighted magnetic resonance imaging study.

BACKGROUND: Silent cerebral embolism with carotid artery stenting (CAS) may contribute to dementia and cognitive decline. Moreover, clinically silent embolism is an important index of peri-procedural stroke risk. AIMS: The purpose of this study was to compare the periprocedural asymptomatic cerebral embolism rates of CAS procedures performed for noncalcified and calcified carotid artery plaques using diffusion-weighted magnetic resonance imaging (DW-MRI). METHODS: Five hundred and seventy clinically uncomplicated patients who underwent CAS at our center from December 2010 to June 2020 (mean [standard deviation, SD] age 69.3 [8.2 years]) were analyzed retrospectively. The patients were divided into 2 groups with noncalcified (268 patients) and calcified (302 patients) plague. Cerebral DW-MRI was performed for the patients before and after CAS and compared. The presence of periprocedural new ipsilateral diffusion limitations detected on cerebral DW-MRI was noted as a significant finding. Ipsilateral diffusion limitations of the non-calcified and calcified plaque groups detected on cerebral DW-MRI were compared. RESULTS: The presence of periprocedural asymptomatic ipsilateral DW-MRI lesions was higher in patients in the noncalcified plaque group (45 [16.8%]) than in patients in the calcified plaque group (31 [10.3%]; P = 0.02). CONCLUSION: This study demonstrated that the rate of ipsilateral asymptomatic cerebral embolism detected on cerebral DW-MRI was higher in the CAS procedures performed for noncalcified carotid artery plaques than in those performed for calcified plaques.

Predictive model for diagnosing central lesions in emergency department patients with isolated dizziness who undergo diffusion-weighted magnetic resonance imaging.

OBJECTIVES: Only 5% to 10% of patients who visit the emergency department (ED) with isolated dizziness without neurologic abnormalities may have central lesions; however, it is important to distinguish central lesions through brain imaging. This study was conducted to create a nomogram to provide an objective medical basis for selectively performing magnetic resonance imaging (MRI) among patients with isolated dizziness. METHODS: This retrospective observational study enrolled patients who visited the ED of a tertiary hospital with isolated dizziness and underwent diffusion-weighted MRI and subsequently consulted with the departments of neurology, neurosurgery, or otorhinolaryngology. Multivariable logistic regression analysis was performed to identify risk factors in patients diagnosed with central lesions to create a nomogram with the significant variables. RESULTS: Of the 1,078 patients who were screened, 119 were diagnosed with central lesions. Significant variables in the multivariable logistic regression analysis were albumin levels (odds ratio [OR] = 0.339, 95% confidence interval [CI] = 0.188 to 0.610, p = 0.0003), inorganic phosphate levels (OR = 0.891, 95% CI = 0.832 to 0.954, p = 0.0010), history of ischemic stroke (OR = 3.170, 95% CI = 1.807 to 5.560, p < 0.0001), presyncope (OR = 3.152, 95% CI = 1.184 to 8.389, p = 0.0216), and nystagmus (OR = 0.365, 95% CI = 0.237 to 0.561, p < 0.0001). The area under the receiver operating characteristic curve of the nomogram created with these variables was 0.7315 (95% CI = 0.6842 to 0.7788, p < 0.0001). CONCLUSIONS: Albumin, inorganic phosphate, previous stroke, presyncope, and nystagmus were associated with the predictive diagnosis of central lesions among patients admitted to the ED with isolated dizziness. The novel nomogram created using these variables can help in objectively determining the need for MRI in patients presenting with isolated dizziness to the ED.

Factors Affecting the Outcome of Symptomatic Carotid Stenosis Surgical Treatment in a Single Center Series.

BACKGROUND: The aim of this study is to evaluate the role of preoperative ischemic brain lesion (IBL) volume, assessed by Diffusion-weighted magnetic resonance brain imaging (DW-MRI) with RAPID® processing, and surgery timing in predicting post-operative neurological outcomes in symptomatic carotid stenosis (SCS) patients treated with carotid endarterectomy (CEA). MATERIALS AND METHODS: All patients with SCS who underwent CEA between January 2010 and June 2020 were considered. IBLs ipsilateral to the stenosis were identified in the preoperative magnetic resonance brain (MRI). The volume was quantified in mL and correlated with 30-day rates of stroke and stroke/death by χ2 and receiver operating characteristic (ROC) curve. RESULTS: One hundred thirty-four patients were surgically treated for SCS during the entire study period. CEA procedures were defined as emergent, urgent, or elective if performed within 48 hr, between 48 hr and 14 days, or after 14 days from symptoms onset, respectively. Cumulative new ipsilateral stroke rate was 4,5%, with a statistically higher neurological complications in emergent patients compared to urgent and elective patients (10,6%, 1,47% and 0% respectively, P 0,039). ROC curve analysis showed a volume of 10 mL was predictive of postoperative stroke with 100% sensitivity and 80% specificity. An IBL volume >10 mL was an independent risk factor for postoperative stroke. In fact, the perioperative neurological complication rate was significantly different in high-IBL volume patients (>10 mL) compared with low-IBL volume patients (<10 mL) (P 0,003) CONCLUSIONS: The present study suggests that the optimal timing for CEA is between 48 hr and 14 days. Furthermore, the present study suggests that the presence of the IBL, by itself, is not definitively related with an unsatisfactory neurological outcome. However, an IBL higher than 10 mL should be as a reliable threshold value adverse neurological result in SCS patients.

Pediatric spinal cord infarction following a minor trauma: a case report.

INTRODUCTION: Pediatric spinal cord infarction is a rare entity that presents a diagnostic challenge at the emergency department. Ischemic spinal cord infarction can occur in the setting of trauma, cardiovascular malformation, or postoperatively. We report a case of anterior spinal artery infarction following seemingly minor trauma in an otherwise healthy 14-year-old male. CASE PRESENTATION: A 14-year-old male presented with unprovoked sudden-onset stabbing back pain earlier that day. The patient then demonstrated bilateral lower extremities weakness while at the emergency department. After extensive diagnostic workup, the patient was diagnosed with anterior spinal artery territory infarction involving the thoracic spinal cord. Minor trauma to the thoracic spinal cord was detected on imaging and was believed to be the culprit of this event. DISCUSSION: Given the rarity of spinal cord ischemia, a high index of suspicion and extensive workup of patients presenting with clinical weakness are needed for accurate diagnosis and to avoid the eventual poor outcome. With so few reports in the literature regarding spinal cord ischemia in the pediatric population, accurate diagnosis is often delayed until after irreversible events have already taken place. Our case report of anterior spinal artery distribution thoracic cord infarct following a minor trauma was diagnosed by axial thin-slice DWI MRI with an otherwise negative workup.

Safety and Feasibility of Magnetic Resonance Imaging of the Brain at 1.5 Tesla in Patients with Temporary Transmyocardial Pacing Leads.

BACKGROUND: Temporary transmyocardial pacing leads (TTPLs) represent an absolute contraindication to magnetic resonance imaging (MRI). The purpose of this study was to evaluate the safety and feasibility of MRI at 1.5 Tesla (T) using a transmit/receive (T/R) head coil in patients with TTPL. METHODS: TTPLs (220 cm, Osypka TME, Dr. Osypka GmbH, Rheinfelden, Germany) were implanted in a phantom and exposed to conditions of a 1.5 T brain examination using a T/R head coil. Temperature changes at the lead tip were continuously recorded. A total of 28 patients with TTPL and an urgent indication for a brain MRI underwent MRI at 1.5 T with vital sign monitoring. A T/R head coil was used to minimize radiofrequency exposure of the TTPL. Before and immediately after the MRI scan, TTPL lead impedance, pacing capture threshold (PCT), signal slope, and sensing were measured. Serum troponin I was determined before and after MRI to detect thermal myocardial injury. RESULTS: In vitro, the maximum temperature increase from radiofrequency-induced heating of the TTPL tip was < 1°C. In vivo, no complications, such as heating sensations, dizziness, unexpected changes in heart rate or rhythm, or other unusual signs or symptoms were observed. No significant changes in the lead impedance, PCT, signal slope, or sensing were recorded. There were no increases of serum troponin I after the MRI examination. CONCLUSIONS: MRI of the brain may be performed safely at 1.5 T using a T/R head coil in case of an urgent clinical need in patients with TTPL and may be considered a feasible and safe procedure when appropriate precautionary measures are taken.

Detection of recurrent hepatocellular carcinoma after surgical resection: Non-contrast liver MR imaging with diffusion-weighted imaging versus gadoxetic acid-enhanced MR imaging.

OBJECTIVE:: To compare the diagnostic performance of non-contrast liver MRI to whole MRI using gadoxetic acid for detection of recurrent hepatocellular carcinoma (HCC) after hepatectomy. METHODS:: This retrospective study analyzed 483 patients who underwent surveillance with liver MRI after hepatectomy for HCC (median time interval, 7.7 months). Non-contrast MRI set (T1- and T2 weighted and diffusion-weighted images) and whole MRI set (gadoxetic acid-enhanced and non-contrast MRI) were analyzed independently by two observers. Receiver operating characteristic analysis was used (with the observers' individual observations and consensus) to detect recurrent HCC. The accuracy, sensitivity, and specificity were calculated. RESULTS:: A total of 113 patients had 197 recurrent HCCs on first follow-up MRI. Although non-contrast MRI had fairly high sensitivity for recurrent HCC, there were significant differences in sensitivity (94.7% vs 99.1%, p = 0.025) and accuracy (97.5% vs 99.2%, p = 0.021) between the two image sets (per-patients base analysis). However, in patients followed for ≥1 year after surgery, the diagnostic performance of non-contrast MRI and whole MRI were not significantly different (p > 0.05). CONCLUSION:: Non-contrast MRI may serve as an alternative follow-up method which can potentially replace whole MRI at least in selected patients followed up ≥1 year after surgery who have relatively lower risk of HCC recurrence. ADVANCES IN KNOWLEDGE:: There is no consensus regarding the ideal imaging modality or follow-up interval after resection of HCC. Non-contrast MRI had comparable performance to that of gadoxetic acid-enhanced MRI in the detection of HCC recurrence during surveillance ≥1 year after surgery.

Diffusion MRI monitoring of specific structures in the irradiated rat brain.

PURPOSE: The analysis of biological and mesoscopic structures properties by diffusion MRI (dMRI) in brain after radiation therapy remains challenging. In our study, we described the consequences associated with an unwanted dose to healthy tissue, assessing radiation-induced brain alterations of living rats with dMRI compared to histopathology and behavioral assays. METHODS: The right primary motor cortex M1 of the rat brain was targeted by stereotactic radiosurgery with a mean radiation dose of 41 Gy. Multidirectional single b-value dMRI data of the whole brain were acquired with a 7T small-animal scanner before irradiation until 110 days post-irradiation. Diffusion tensor imaging metrics, such as fractional anisotropy (FA), mean diffusivity (MD), axial (AD), and radial diffusivity (RD) were compared to brain alterations detected by immunohistochemistry and motor performances measured by a behavioral test. RESULTS: Between days 90 and 110, radiation necrosis was observed into the white matter spreading into M1 . Results showed a reduction of FA in the corpus callosum and in the striatum, which was driven by an increase in RD from 90 to 110 days post-irradiation, whereas only RD increased in M1 . Values of RD and AD increased in the irradiated hippocampus, while FA remained constant. Moreover, an increased MD, AD and RD was observed in the hippocampus that was probably related to inflammation as well as reactive astrogliosis after 110 days post-irradiation. Finally, rats did not exhibit locomotor deficits. CONCLUSIONS: dMRI metrics can assess brain damage; the sensitivity of dMRI metrics depends on the brain region.

Neoadjuvant volumetric modulated arc therapy in rectal cancer and the correlation of pathological response with diffusion-weighted MRI and apoptotic markers.

PURPOSE: In this prospective observational study, we aimed to report the applicability and tolerability of neoadjuvant volumetric modulated arc therapy with simultaneous integrated boost (SIB-VMAT) and concurrent chemotherapy in patients with locally advanced rectal cancer (LARC), and to evaluate the correlation of pathological response with apparent diffusion coefficient (ADC) measurements on diffusion-weighted magnetic resonance imaging (DW-MRI) and apoptotic markers. METHODS: The study enrolled 30 patients with T3 to T4 and/or N+ rectal cancer who preoperatively received SIB-VMAT and concurrent chemotherapy. Before and after the neoadjuvant treatment, apoptotic markers including the nucleosomes and cell-free DNA fragments in the serum samples were examined; DNA integrity was assessed by amplifying the ACTB gene; and the ADC measurements on the DW-MRI were analyzed. RESULTS: No patients had acute or chronic grade III-IV toxicity. Pathologic complete response (pCR) was achieved in 8 patients (27%), while in 10 patients (33%) near-complete pathological response was obtained. Posttreatment ADC was significantly higher in patients with pCR compared with the others (1.28 vs. 1.10, p = 0.017). ROC curve analysis showed that posttreatment ADC values had a sensitivity of 75% and a specificity of 77.3% for distinguishing the patients with pCR from other responders. On the other hand, posttreatment DNA integrity values were revealed lower than the pretreatment values (p = 0.36). Also, the results revealed an insignificant increase in the posttreatment serum level of nucleosomes (p = 0.72). CONCLUSIONS: Neoadjuvant SIB-VMAT with concurrent chemotherapy was proved to be a feasible treatment regimen in LARC with tolerable side effects, and improved local control rate and pCR rate.

Director Field Analysis (DFA): Exploring Local White Matter Geometric Structure in Diffusion MRI.

In Diffusion Tensor Imaging (DTI) or High Angular Resolution Diffusion Imaging (HARDI), a tensor field or a spherical function field (e.g., an orientation distribution function field), can be estimated from measured diffusion weighted images. In this paper, inspired by the microscopic theoretical treatment of phases in liquid crystals, we introduce a novel mathematical framework, called Director Field Analysis (DFA), to study local geometric structural information of white matter based on the reconstructed tensor field or spherical function field: (1) We propose a set of mathematical tools to process general director data, which consists of dyadic tensors that have orientations but no direction. (2) We propose Orientational Order (OO) and Orientational Dispersion (OD) indices to describe the degree of alignment and dispersion of a spherical function in a single voxel or in a region, respectively; (3) We also show how to construct a local orthogonal coordinate frame in each voxel exhibiting anisotropic diffusion; (4) Finally, we define three indices to describe three types of orientational distortion (splay, bend, and twist) in a local spatial neighborhood, and a total distortion index to describe distortions of all three types. To our knowledge, this is the first work to quantitatively describe orientational distortion (splay, bend, and twist) in general spherical function fields from DTI or HARDI data. The proposed DFA and its related mathematical tools can be used to process not only diffusion MRI data but also general director field data, and the proposed scalar indices are useful for detecting local geometric changes of white matter for voxel-based or tract-based analysis in both DTI and HARDI acquisitions. The related codes and a tutorial for DFA will be released in DMRITool.

In-bore transrectal MRI-guided prostate biopsies: Are there risk factors for complications?

PURPOSE: To systematically analyze risk factors for complications of in-bore transrectal MRI-guided prostate biopsies (MRGB). MATERIALS AND METHODS: 90 patients, who were scheduled for MRGB were included for this study. Exclusion criteria were coagulation disorders, therapy with anticoagulant drugs, and acute infections of the urinary and the lower gastrointestinal tract. Directly after, one week and one year after the biopsy, we assessed biopsy related complications (e.g. hemorrhages or signs of prostatitis). Differences between patients with and without complications were analyzed regarding possible risk factors: age, prostate volume, number of taken samples, biopsy duration, biopsy of more than one lesion, diabetes, arterial hypertension, hemorrhoids, benign prostate hyperplasia, carcinoma or prostatitis (according to histopathological analysis), and lesion localization. Complications were classified according to the Clavien-Dindo classification. RESULTS: We observed 15 grade I complications in 90 biopsies (16.7%) with slight hematuria in 9 cases (10%), minor vasovagal reactions in 4 cases (4.4%), and urinary retention and positioning-related facial dysesthesia in 1 case each (1.1%). One patient showed acute prostatitis requiring antibiotics as the only grade II complication (1.1%). There were no adverse events that occurred later than one week. Complications grade III or higher such as pelvic abscesses, urosepsis or severe hemorrhages were not seen. There were no significant associations between the assessed risk factors and biopsy-related complications. CONCLUSION: In-bore transrectal MRI-guided prostate biopsies can be considered safe procedures in the diagnosis of prostate cancer with very low complication rates. There seem to be no risk factors for complications.

Breast magnetic resonance imaging performance: safety, techniques, and updates on diffusion-weighted imaging and magnetic resonance spectroscopy.

Dynamic contrast-enhanced breast magnetic resonance imaging (MRI) is a well-established, highly sensitive technique for the detection and evaluation of breast cancer. Optimal performance of breast MRI continues to evolve. This article addresses breast MRI applications, covers emerging breast MRI safety concerns; outlines the technical aspects of breast MRI, including equipment and protocols at 3 T and 1.5 T; and describes current promising areas of research including diffusion-weighted imaging and magnetic resonance spectroscopy.

Incidence and risk factors for diffusion-weighted imaging (+) lesions after intracranial stenting and its relationship with symptomatic ischemic complications.

BACKGROUND AND PURPOSE: Little is known about high-signal lesions in magnetic resonance diffusion-weighted imaging (DWI [+]) after stenting for intracranial atherosclerotic stenosis. This study aimed to evaluate the incidence, distribution, risk factors, and clinical implications of DWI (+) after intracranial stenting. METHODS: A total of 123 patients (male:female=88:35, mean age, 64.1 years) with symptomatic intracranial atherosclerotic stenosis (mean stenosis, 76.1±7.7%) underwent both stenting and poststenting DWI. The incidence, distribution (embolic-alone versus stenosis-associated perforator/mixed), and risk factors of DWI (+) and its relationship with symptomatic ischemic complications (SIC, including stroke or transient ischemic attack) were retrospectively evaluated. RESULTS: Forty-three patients (35.0%) had DWI (+). Middle cerebral artery, smaller distal parent artery, and treatment-related dissection were independent risk factors for DWI (+) (P<0.05). SIC occurred in 4 patients (3.3%), all of whom had DWI (+). Of the patients with DWI (+), neither the number nor the volume of DWI (+) differed significantly between SIC and asymptomatic patients: median number/patient, 3.5 (range, 2-11) versus 2.0 (range, 1-11) and median volume/patient, 329.8 mm(3) (range, 76-883.5 mm(3)) versus 119.5 mm(3) (range, 32.5-873.0 mm(3)). However, SIC occurred more frequently in the stenosis-associated perforator/mixed type (3/11, 27.3%) than in the embolic-alone type (1/32, 3.1%; P<0.05). CONCLUSIONS: The incidence of DWI (+) after intracranial stenting for intracranial atherosclerotic stenosis was 35.0%. Middle cerebral artery, smaller distal parent artery, and treatment-related dissection were independent risk factors for DWI (+). SIC occurred more frequently in the stenosis-associated perforator/mixed type than in the embolic-alone type.

The fundamentals of fetal MR imaging: Part 1.

Congenital malformations detected in any fetal system using ultrasound may be further evaluated with magnetic resonance imaging (MRI) to improve counseling, to plan deliveries appropriately, and sometimes to enable fetal interventions. In this first half of a 2-part review, the history and safety factors regarding fetal MRI, as well as the practical aspects of image acquisition, are discussed. In addition, as central nervous system anomalies are most commonly and best evaluated using fetal MRI, challenging central nervous system anomalies, such as fetal ventriculomegaly, posterior anomalies, and neural tube defects, detected using prenatal ultrasound are also reviewed with a focus on the fundamental implications of these diagnoses.

Assessment of the kidneys: magnetic resonance angiography, perfusion and diffusion.

Renal magnetic resonance (MR) imaging has undergone major improvements in the past several years. This review focuses on the technical basics and clinical applications of MR angiography (MRA) with the goal of enabling readers to acquire high-resolution, high quality renal artery MRA. The current role of contrast agents and their safe use in patients with renal impairment is discussed. In addition, an overview of promising techniques on the horizon for renal MR is provided. The clinical value and specific applications of renal MR are critically discussed.

Diffusion tensor tractography: corticospinal tract fiber reduction is associated with temporary hemiparesis in benign extracerebral lesions.

OBJECTIVE: Benign extracerebral lesions such as meningiomas may cause hemiparesis by compression and deviation without infiltrating the white matter. We used magnetic resonance diffusion tensor imaging and diffusion tensor tractography to investigate the effects of benign extracerebral lesions on the corticospinal tract (CST). METHODS: Thirteen patients with extracerebral lesions (11 benign meningiomas and 2 benign cysts) underwent magnetic resonance diffusion tensor imaging and diffusion tensor tractography of the CST using fiber assignment by continuous tractography. The CST was reconstructed and assessed by comparing the ipsilateral and unaffected contralateral fibers. The tumor volume, relative fractional anisotropy, fiber deviation, relative fiber number, and relative fiber per voxel were compared between patients without and with temporary presurgical hemiparesis. RESULTS: Seven patients without hemiparesis and five patients with temporary hemiparesis were analyzed; one patient had permanent weakness and was excluded from analysis. There was no significant difference in the tumor volume, relative fractional anisotropy, presence of cerebral edema, or CST deviation between groups. In patients with temporary hemiparesis, the median relative fiber number (mean, 0.35 +/- 0.32) and relative fiber per voxel (mean, 0.49 +/- 0.14) were significantly reduced compared with patients without hemiparesis (0.92 +/- 0.55, P = 0.04; and 0.96 +/- 0.28, P < 0.01, respectively). CONCLUSION: In patients with benign extracerebral lesions, reduction in fiber number and fiber per voxel, but not fiber deviation, correlated with temporary hemiparesis. Clinical recovery was possible even if the CST fibers detected by diffusion tensor tractography were reduced by benign extracerebral lesions.

How affected is oxygen metabolism in DWI lesions?: A combined acute stroke PET-MR study.

OBJECTIVE: To use back-to-back diffusion-weighted imaging (DWI) and PET to obtain quantitative measures of the cerebral metabolic rate of oxygen (CMRO(2)) within DWI lesions, and to assess the perfusion-metabolism coupling status by measuring the cerebral blood flow and the oxygen extraction fraction within DWI lesions. METHODS: Six prospectively recruited acute carotid-territory stroke patients completed the imaging protocol, which was commenced 7 to 21 hours from onset and combined DWI derived from state-of-the-art diffusion tensor imaging sequencing using a 3-T magnet and fully quantitative (15)O-PET. The PET variables were obtained in individual DWI lesions in each patient. RESULTS: Across patients, the CMRO(2) was reduced in the DWI lesion relative to mirror (mean reduction 39.5%; p = 0.028). Examining individual DWI lesions, however, revealed considerable variability in the extent of this CMRO(2) reduction. The flow-metabolism coupling pattern underlying the DWI lesion was also variable, including ongoing ischemia, mild oligemia, and partial or complete reperfusion. DISCUSSION: Diffusion-weighted imaging (DWI) lesions generally reflect substantial disruption of energy metabolism. However, the degree of metabolic disruption is variable, indicating DWI lesions may not always represent irreversibly damaged tissue. Finally, because DWI lesions can persist despite reperfusion, assessment of perfusion is necessary for interpretation of DWI changes in acute stroke.