Conventional Magnetic Resonance Imaging Sequences Research Articles

Machine learning-based quantitative texture analysis of conventional MRI combined with ADC maps for assessment of IDH1 mutation in high-grade gliomas.

To assess the performance of texture analysis of conventional magnetic resonance imaging (MRI) and apparent diffusion coefficient (ADC) maps in predicting IDH1 status in high-grade gliomas (HGG). A total of 142 patients with HGG were included in the study. IDH1 mutation was present in 48 of 142 HGG (33.8%). Patients were randomly divided into the training cohort (n = 96) and the validation cohort (n = 46). Texture features were extracted via regions of interest on axial T2WI FLAIR, post-contrast T1WI, and ADC maps covering the whole volume of the tumors. The training cohort was used to train the random forest classifier, and the diagnostic performance of the pre-trained model was tested on the validation cohort. The random forest model of conventional MRI sequences and ADC images achieved diagnostic accuracy of 82.2% and 80.4% in predicting IDH1 status in the validation cohorts, respectively. The combined model of T2WI FLAIR, post-contrast T1WI, and ADC images exhibited the highest diagnostic accuracy equating 86.94% in the validation cohort. Texture analysis of conventional MRI sequences enhanced by ML analysis can accurately predict the IDH1 status of HGG. Adding textural analysis of ADC maps to conventional MRI results in incremental diagnostic performance.

Evaluation of giant arachnoid granulations with high-resolution 3D-volumetric MR sequences at 3T

PurposeTo evaluate the contribution to the diagnosis of the giant arachnoid granulations (AGs) of three-dimensional (3D) high-resolution magnetic resonance (MR) imaging sequences such as T2-weighted sampling perfection with application optimized contrasts using different flip-angle evolution (SPACE) and post-contrast T1-weighted magnetization prepared rapid gradient echo (MPRAGE). Materials and MethodsPatients with 45 giant AGs were included in this retrospective study. All the patients were performed 3D T2-weighted SPACE and contrast enhanced MR venography sequences, as well as conventional cerebral MR imaging sequences. Post-contrast T1 weighted MPRAGE sequence were performed on 38/45 patients. All cerebral MR examinations were reviewed by the 2 neuroradiologists. Each GA was evaluated carefully to assess location and mean diameter. ResultsThe most common location for giant AGs was at both transverse sinuses. Fluid signal feature within the giant AGs was not isointense to CSF on SE T1 and FLAIR MR imaging in 32 of 45 giant AGs. There were cerebral herniation into AG in 10 (22.2 %) of 45 giant AGs. 33 (73.3 %) of 45 giant AGs had central vein finding into AG in contrast enhanced MR venography. Signal void phenomenon into AG in 3D T2-weighted SPACE MR sequence was identified in 28 (62.2 %) of 45 giant AGs. ConclusionsFluid within giant AGs had no completely CSF-like signal intensity on conventional and 3D high-resolution MR imaging sequences. Majority of CSF-incongruent fluid within giant AGs on conventional sequences is mostly due to intra-AG CSF flow.

Simultaneous non-contrast angiography and intraplaque haemorrhage (SNAP) imaging for cervical artery dissections

To evaluate the feasibility of high-resolution magnetic resonance imaging (MRI) with a simultaneous non-contrast angiography and intraplaque haemorrhage (SNAP) sequence in identifying cervical artery dissections (CeAD). Fifty-three patients with suspected CeAD underwent the SNAP sequence (including non-contrast magnetic resonance angiography [MRA] and heavy T1-weighting vessel wall images simultaneously in a single scan) and conventional MRI sequences (including three-dimensional [3D] time-of-flight MRA and T1-weighted black-blood imaging [T1W BB]) and cervical vascular ultrasound (CVUS). In diagnosis of CeAD, the diagnostic sensitivity and specificity of SNAP, and the diagnostic coherence between SNAP and conventional sequences and between SNAP and CVUS was analysed. At follow-up, the absolute signal (AS) and signal index (SI) of the intramural haematoma (IMH) between vessel wall images on SNAP and T1W-BB images were compared. The image quality of SNAP was analysed by comparing the signal-to-noise ratio (SNR) between vessel wall images from the SNAP and T1W-BB sequences. The SNAP sequence was found to provide good performance in the diagnosis of CeAD (sensitivity 72.2%, specificity 98.2%); good agreement was found between SNAP and conventional sequences (Cohen's κ=0.76, p<0.05); and excellent agreement was found between SNAP and CVUS (Cohen's κ=0.83, p<0.05). There was no significant difference between AS or SI of the IMH of the vessel wall images within the SNAP and T1W-BB sequences during the review. The SNAP sequence had higher SNR of the IMH compared to T1W-BB, T2W-BB, proton-density-weighted volume isotropic turbo-spin-echo acquisition imaging (PD-VISTA) sequences (p<0.05). The SNAP sequence holds the potential to be preferred choice for screening of patients with a high suspicion of CeAD and for the follow-up of IMH after treatment.

Validity and reliability of measurements of aponeurosis dimensions from magnetic resonance images

Muscle performance is closely related to the structure and function of tendons and aponeuroses, the sheet-like, intramuscular parts of tendons. The architecture of aponeuroses has been difficult to study with magnetic resonance imaging (MRI) because these thin, collagen-rich connective tissues have very short transverse relaxation (T2) times and therefore provide a weak signal with conventional MRI sequences. Here, we validated measurements of aponeurosis dimensions from two MRI sequences commonly used in muscle-tendon research (mDixon and T1-weighted images), and an ultrashort echo time (UTE) sequence designed for imaging tissues with short T2 times. MRI-based measurements of aponeurosis width, length, and area of 20 sheep leg muscles were compared to direct measurements made with three-dimensional (3D) quantitative microdissection. The errors in measurement of aponeurosis width relative to the mean width were 1.8% for UTE, 3.7% for T1, and 18.8% for mDixon. For aponeurosis length, the errors were 7.6% for UTE, 1.9% for T1, and 21.0% for mDixon. Measurements from T1 and UTE scans were unbiased, but mDixon scans systematically underestimated widths, lengths, and areas of the aponeuroses. Using the same methods, we then found high inter-rater reliability (intraclass correlation coefficients >0.92 for all measures) of measurements of the dimensions of the central aponeurosis of the human tibialis anterior muscle from T1-weighted scans. We conclude that valid and reliable measurements of aponeurosis dimensions can be obtained from UTE and from T1-weighted scans. When the goal is to study the macroscopic architecture of aponeuroses, UTE does not hold an advantage over T1-weighted imaging.

The Predictive Value of Conventional Magnetic Resonance Imaging Sequences on Operative Findings and Histopathology of Intracranial Meningiomas: A Prospective Study.

Previous studies have tried to relate magnetic resonance (MR) characteristics of meningiomas with its intraoperative features and histopathology with varying results. This is a prospective study to assess the independent predictive value of conventional MR signals [T1, T2, and fluid attenuated inversion recovery (FLAIR)] in relation to consistency, vascularity, operative plane, Simpson excision, and histopathology of intracranial meningiomas in a multivariate model. Seventy patients underwent T1, T2, FLAIR, postcontrast sequences followed by excision of their meningiomas. Tumor signal intensity in various sequences was studied in relation to the above-mentioned variables. Multivariate analysis to find their independent association was performed. T1 images showed no correlation with any of the variables. FLAIR hypointensity and inhomogeneous enhancement had significant association with tumor hardness. FLAIR hypointense tumors were associated with low vascularity. FLAIR hypointensity, skull base location, and recurrence were significantly related to the subpial or mixed operative plane. The meningioma-brain interface on T2 sequence was significantly related to the operative plane. Only skull base location had significant impact on the extent of excision. T2 and FLAIR hypointensity had significant association with fibroblastic or psammomatous meningiomas. On multivariate analysis, FLAIR hypointensity and skull base location had a significant independent relationship with suboptimal operative plane, while skull base location had association with the extent of excision. Among MRI sequences, FLAIR hypointensity showed high specificity (94%) in predicting the suboptimal operative plane. FLAIR hypointensity of meningiomas appears to have a significant independent association with the suboptimal operative plane with high specificity.

Evaluating the Scope of Malignant Bone Tumor Using ADC Measurement on ADC Map.

Background:It is very important for surgeons to know the accurate borders of malignant bone tumors before they can precisely resect the tumors. The objective of the study is to investigate the usefulness of apparent diffusion coefficient value for estimating the extent of malignant bone tumor.Methods:VX2 tumor fragments were implanted into the tibiae of 30 rabbits. After 4 weeks, magnetic resonance plain scans were performed and then tumor specimens were cut into sagittal sections and partitioned into histology slices for dot-to-dot comparisons with microscopic findings. The sizes of the tumors measured separately on specimen, conventional magnetic resonance imaging sequences, and diffusion-weighted imaging (by measuring apparent diffusion coefficient value on apparent diffusion coefficient mapping) were compared statistically with each other.Results:The mean tumor sizes measured on specimen and apparent diffusion coefficient mapping (by calculating apparent diffusion coefficient value) were 5.20 ± 0.89 cm and 5.31 ± 0.87 cm, respectively; there was no significant difference between the 2 (P > .05). The tumor sizes measured on T1WI, T2WI, T2WI with fat suppression were 4.82 ± 0.87 cm, 5.58 ± 0.87 cm, 5.63 ± 0.85 cm, respectively, and these values were significantly different from that measured on specimen (5.20 ± 0.89 cm, P < .05).Conclusion:The extent of the VX2 malignant bone tumor can be estimated accurately by measurement of apparent diffusion coefficient value.

MR Imaging of Chondrogenic Tumors: Update on Select Imaging Challenges

This review article discusses the updated World Health Classification of chondrogenic skeletal tumors and the role of conventional and advanced magnetic resonance (MR) imaging in the evaluation of chondrogenic skeletal lesions with emphasis on select diagnostic dilemmas. The majority of benign chondrogenic skeletal lesions have typical radiographic and MR features. Conventional MR imaging sequences can be helpful in the distinction of tumor-like lesions from chondrogenic tumors, and the evaluation of anatomic extent, particularly with regard to the detection of soft tissue masses associated with a chondrosarcoma (CS). Benign, atypical, and malignant chondrogenic lesions can have overlapping features on diffusion-weighted imaging (DWI) with apparent diffusion coefficient (ADC) mapping although dynamic contrast-enhanced (DCE) sequences can be helpful in the characterization of chondrogenic tumors as benign or malignant. Patients with multiple chondrogenic tumor conditions or syndromes are predisposed to developing CS and extra-skeletal malignancies, and as such, a small subset may benefit from imaging surveillance. The majority of chondrogenic skeletal lesions can be characterized confidently on imaging. In the small subset of intermediate and malignant chondrogenic lesions with overlapping imaging and pathological features, a multidisciplinary approach should be used.

MRI-Guided Interventions in Musculoskeletal System.

Image-guided interventions in the musculoskeletal system require accurate detection and characterization of lesions involving bone and soft tissues. Magnetic resonance imaging (MRI) has superior soft tissue contrast resolution particularly in bone and soft tissues where computed tomography and ultrasonography have significant limitations. In addition, the multiplanar imaging capabilities of MRI facilitate targeting lesions and tracking interventional devices. Although conventional diagnostic MRI sequences suffer from motion sensitivity and prolonged imaging time, recently developed fast imaging sequences allow for rapid acquisition of high-quality images, rendering MRI more suitable for image-guided interventions. Although computed tomography and ultrasonography still dominate the spectrum of image-guided interventions in the musculoskeletal system, many MRI-guided procedures have been developed and are well established in routine clinical work. In addition, new techniques and novel MRI-guided applications are being developed to address complex clinical problems in a minimally invasive fashion.

Clinical Application of 3D-CISS MRI Sequences for Diagnosis and Surgical Planning of Spinal Arachnoid Diverticula and Adhesions in Dogs.

Abnormalities within the spinal arachnoid space are often treated surgically, but they can be challenging to detect with conventional magnetic resonance imaging (MRI) sequences. 3D-CISS sequences are considered superior in evaluating structures surrounded by cerebrospinal fluid (CSF) due to the high signal-to-noise ratio, high contrast-to-noise ratio and intrinsic insensitivity to motion with minimal signal loss due to CSF pulsations. Our objective was to describe findings and advantages in adding 3D-CISS sequences to routine MRI in patients affected by spinal arachnoid diverticula (SAD) or arachnoid adhesions. This article is a retrospective review of medical records of 19 dogs admitted at Fitzpatrick Referrals between 2013 and 2017 that were diagnosed with SAD and confirmed surgically. Inclusion criterions were the presence of clinical signs compatible with compressive myelopathy and an MRI diagnosis, which included the 3D-CISS sequence. Our database was searched for additional 19 dogs diagnosed with other spinal lesions other than SAD that had the same MR sequences. All MR images were anonymized and evaluated by two assessors. 3D-CISS sequence appears to improve confidence in diagnosing and surgical planning (Mann-Whitney U-test: p < 0.0005), delineating SAD from other changes associated with abnormal CSF hydrodynamics and providing more anatomical details than conventional MRI sequences. The clinical data in combination with imaging findings would limit over interpretation, when concurrent pathology within the arachnoid space is present.

Chapter 23 - Postmortem magnetic resonance imaging

This chapter provides a brief overview of studies that combine postmortem magnetic resonance imaging (MRI) and histopathology. We touch upon the logistics of setting up a protocol that limits unwanted postmortem delays and explain how combining postmortem MRI and histopathology can elucidate the histologic substrate of signal changes that appear on MRI. This is demonstrated by exemplary studies in multiple sclerosis, and includes various histopathologic techniques and a wide range of conventional and advanced MRI sequences at various field strengths. We cover topics such as how to visualize white-matter pathology and repair with conventional and advanced MRI sequences, describe the history of visualizing pathology of the gray matter (with newly developed MRI and immunohistopathology techniques), and how advanced methods have aided research in other neurologic diseases. We conclude with several suggestions for future development, such as bridging the gap between postmortem and in vivo research and the importance of collecting non-neurological control tissue.

Chapter 13 - Conventional MRI

Conventional magnetic resonance imaging (MRI) allows for a detailed noninvasive visualization/examination of posterior fossa structures and represents a fundamental step in the diagnostic workup of many cerebellar disorders. In the first part of this chapter methodologic issues, like the correct choice of hardware (magnets, coils), pro and cons of the different MRI sequences, and patient management during the examination are discussed. In the second part, the MRI anatomy of the cerebellum, as noted on the various conventional MRI sequences, as well as a detailed description of cerebellar maturational processes from birth to childhood and into adulthood, are reported. Volumetric studies on the cerebellar growth based on three-dimensional MRI sequences are also presented. Moreover, we briefly discuss two main topics regarding conventional MRI of the cerebellum that have generated some debate in recent years: the differentiation between cerebellar atrophy, hypoplasia, and pontocerebellar hypoplasia, and signal changes of dentate nuclei after repetitive gadolinium-based contrast injections. The advantages and benefits of advanced neuroimaging techniques, including 1H magnetic resonance spectroscopy, diffusion-weighted imaging, diffusion tensor imaging, and perfusion-weighted imaging are discussed in the last section of the chapter.

Pitfalls of diffusion-weighted imaging of the female pelvis.

Diffusion-weighted imaging (DWI) is widely used in protocols for magnetic resonance imaging (MRI) of the female pelvis. It provides functional and structural information about biological tissues, without the use of ionizing radiation or intravenous administration of contrast medium. High signal intensity on DWI with simultaneous low signal intensity on apparent diffusion coefficient maps is usually associated with malignancy. However, that pattern can also be seen in many benign lesions, a fact that should be recognized by radiologists. Correlating DWI findings with those of conventional (T1- and T2-weighted) MRI sequences and those of contrast-enhanced MRI sequences is mandatory in order to avoid potential pitfalls. The aim of this review article is the description of the most relevant physiological and benign pathological conditions of the female pelvis that can show restricted diffusion on DWI.

Orbital infantile hemangioma and rhabdomyosarcoma in children: differentiation using diffusion-weighted magnetic resonance imaging

To evaluate differences in magnetic resonance imaging (MRI) appearance between infantile hemangiomas and rhabdomyosarcomas of the orbit in pediatric patients using diffusion-weighted imaging. A multicenter retrospective review of MRIs of pediatric patients with infantile hemangiomas and rhabdomyosarcomas of the orbit was performed. MRI examinations from a total of 21 patients with infantile hemangiomas and 12 patients with rhabdomyosarcomas of the orbit were independently reviewed by two subspecialty board-certified neuroradiologists masked to the diagnosis. A freehand region of interest was placed in the mass to obtain the mean apparent diffusion coefficient (ADC) value of the mass as well as within the medulla to obtain a ratio of the ADC mass to the medulla. A t test was used to compare mean ADC and ADC ratios between the two groups. Receiver operating characteristic analysis was performed to determine ADC value and ADC ratio thresholds for differentiation of infantile hemangioma and rhabdomyosarcoma. There was a statistically significant difference in the mean ADC value of infantile hemangiomas compared to rhabdomyosarcomas (1527×10-6mm2/s vs 782×10-6mm2/s; P=0.0001) and the ADC ratio of the lesion to the medulla (1.77 vs 0.92; P=0.0001). An ADC threshold of <1159×10-6mm2/sec and an ADC ratio of <1.38 differentiated rhabdomyosarcoma from infantile hemangioma (sensitivity 100% and 100%; specificity 100% and 100%) with area under the curve of 1.0 and 1.0, respectively. In conjunction with conventional MRI sequences, ADC values obtained from diffusion-weighted MRI are useful to differentiate orbital infantile hemangiomas from rhabdomyosarcomas in pediatric patients.

Magnetic resonance in traumatic brain injury: A comparative study of the different conventional magnetic resonance imaging sequences and their diagnostic value in diffuse axonal injury

ObjectiveTo compare the identification capability of traumatic axonal injury (TAI) by different sequences on conventional magnetic resonance (MR) studies in traumatic brain injury (TBI) patients. Material and methodsWe retrospectively analysed 264 TBI patients to whom a MR had been performed in the first 60 days after trauma. All clinical variables related to prognosis were registered, as well as the data from the initial computed tomography. The MR imaging protocol consisted of a 3-plane localiser sequence T1-weighted and T2-weighted fast spin-echo, FLAIR and gradient-echo images (GRET2*). TAI lesions were classified according to Gentry and Firsching classifications. We calculated weighted kappa coefficients and the area under the ROC curve for each MR sequence. A multivariable analysis was performed to correlate MR findings in each sequence with the final outcome of the patients. ResultsTAI lesions were adequately visualised on T2, FLAIR and GRET2* sequences in more than 80% of the studies. Subcortical TAI lesions were well on FLAIR and GRET2* sequences visualised haemorrhagic TAI lesions. We saw that these MR sequences had a high inter-rater agreement for TAI diagnosis (0.8). T2 sequence presented the highest value on ROC curve in Gentry (0.68, 95%CI: 0.61–0.76, p<0.001, Nagerlkerke-R2 0.26) and Firsching classifications (0.64, 95%CI 0.57–0.72, p<0.001, Nagerlkerke-R2 0.19), followed by FLAIR and GRET2* sequences. Both classifications determined by each of these sequences were associated with poor outcome after performing a multivariable analyses adjusted for prognostic factors (p<0.02). ConclusionsWe recommend to perform conventional MR study in subacute phase including T2, FLAIR and GRET2* sequences for visualise TAI lesions. These MR findings added prognostic information in TBI patients.

Histogram Analysis of T1-Weighted, T2-Weighted, and Postcontrast T1-Weighted Images in Primary CNS Lymphoma: Correlations with Histopathological Findings-a Preliminary Study.

Previously, some reports mentioned that magnetic resonance imaging (MRI) can predict histopathological features in primary CNS lymphoma (PCNSL). The reported data analyzed diffusion-weighted imaging findings. The aim of this study was to investigate possible associations between histopathological findings, such as tumor cellularity, nucleic areas and proliferation index Ki-67, and signal intensity on T1-weighted and T2-weighted images in PCNSL. For this study, 18 patients with PCNSL were retrospectively investigated by histogram analysis on precontrast and postcontrast T1-weighted and fluid-attenuated inversion recovery (FLAIR) images. For every patient, histopathology parameters, nucleic count, total nucleic area, and average nucleic area, as well as Ki-67 index, were estimated. Correlation analysis identified several statistically significant associations. Skewness derived from precontrast T1-weighted images correlated with Ki-67 index (p=-0.55, P=0.028). Furthermore, entropy derived from precontrast T1-weighted images correlated with average nucleic area (p=0.53, P=0.04). Several parameters from postcontrast T1-weighted images correlated with nucleic count: maximum signal intensity (p=0.59, P=0.017), P75 (p=0.56, P=0.02), and P90 (p=0.52, P=0.04) as well as SD (p=0.58, P=0.02). Maximum signal intensity derived from FLAIR sequence correlated with nucleic count (p=0.50, P=0.03). Histogram-derived parameters of conventional MRI sequences can reflect different histopathological features in PSNCL.

Less Is More: Efficacy of Rapid 3D-T2 SPACE in ED Patients with Acute Atypical Low Back Pain

Emergency department (ED) patients with acute low back pain (LBP) may present with ambiguous clinical findings that pose diagnostic challenges to exclude cauda equina syndrome (CES). As a proof of concept, we aimed to determine the efficacy of a rapid lumbar spine (LS) magnetic resonance imaging (MRI) screening protocol consisting of a single 3D-T2 SPACE FS (3D-T2 Sampling Perfection with Application optimized Contrasts using different flip angle Evolution fat saturated) sequence relative to conventional LS MRI to exclude emergently treatable pathologies in this complex patient population. LS MRI protocol including a sagittal 3D-T2 SPACE FS pulse sequence was added to the routine for ED patients presenting with acute atypical LBP over a 12-month period. Imaging findings were categorically scored on the 3D-T2 SPACE FS sequence and separately on the reference standard conventional LS MRI sequences. Patients' symptoms were obtained from review of the electronic medical record. Descriptive test statistics were performed. Of the 206 ED patients who obtained MRI for acute atypical LBP, 118 (43.3 ± 13.5 years of age; 61 female) were included. Specific pathologies detected on reference standard conventional MRI included disc herniation (n = 30), acute fracture (n = 3), synovial cyst (n = 3), epidural hematoma (n = 2), cerebrospinal fluid leak (n = 1), and leptomeningeal metastases (n = 1), and on multiple occasions these pathologies resulted in nerve root impingement (n = 36), severe spinal canal stenosis (n = 13), cord/conus compression (n = 2), and cord signal abnormality (n = 2). The 3D-T2 SPACE FS sequence was an effective screen for fracture (sensitivity [sens] = 100%, specificity [spec] = 100%), cord signal abnormality (sens = 100%, spec = 99%), and severe spinal canal stenosis (sens = 100%, spec = 96%), and identified cord compression not seen on reference standard. Motion artifact was not seen on the 3D-T2 SPACE FS but noted on 8.5% of conventional LS MRI. The 3D-T2 SPACE FS sequence MRI is a rapid, effective screen for emergently actionable pathologies that might be a cause of CES in ED patients presenting with acute atypical LBP. As this abbreviated, highly sensitive sequence requires a fraction of the acquisition time of conventional LS MRI, it has the potential of contributing to increased efficiencies in the radiology department and improved ED throughput.

Diffusion-weighted magnetic resonance imaging in cystic renal masses

We aimed to introduce the diagnostic value of diffusion-weighted (DWI) magnetic resonance imaging (MRI) for distinguishing benign and malignant renal cystic masses. Abdominal DWI-MRIs of patients with Bosniak categories 2F, 3, and 4 cystic renal masses were evaluated retrospectively. Cystic masses were assigned as benign or malignant according to histopathological or followup MRI findings and compared with apparent diffusion coefficient (ADC) values. There were 30 patients (18 males and 12 females, mean age was 59.23 ± 12.08 years [range 38-83 years]) with cystic renal masses (eight Bosniak category 2F, 12 Bosniak category 3, 10 Bosniak category 4). Among them, 14 cysts were diagnosed as benign and 16 as malignant by followup imaging or histopathological findings. For the malignant lesions, the mean ADC values were lower than for benign lesions (p=0.001). An ADC value of ≤2.28 ×10-6 mm2/s or less had a sensitivity of 75% and a specificity of 92.86% for detecting malignancy. ADC can improve the diagnostic performance of MRI in the evaluation of complex renal cysts when used together with conventional MRI sequences.

The tuber cinereum as a circumventricular organ: an anatomical study using magnetic resonance imaging

The tuber cinereum (TC) comprises the hypothalamic gray matter that forms the anterior portion of the third ventricle floor. However, since it has been rarely documented in previous neuroimaging investigations, the aim of the current study was to explore the morphology of the TC using magnetic resonance imaging (MRI). Ninety-two patients were enrolled in this study. Following initial examination with conventional MRI sequences, a contrast study using intravenous gadolinium injection was performed in thin-sliced sections. The TC, which was commonly defined as a linear, enhancing structure on the midsagittal section, was identified in all 92 cases. In 83% of cases, the third ventricle floor had a gentle inflection at the junctional site between the median eminence and TC. The angle formed between the line parallel to the TC and the horizontal line showed considerable variability, which ranged from 0.5° to 56°. Furthermore, a non-enhancing segment of variable length was identified in the posterior-most TC. In 11% of cases, the midline TC was enhanced over the whole length. Since the most part of the midline TC was enhanced with intravenous gadolinium injection, it may function as a circumventricular organ. The TC should be evaluated with contrast sagittal MRI prior to performing surgery with management of the anterior third ventricle floor.

Puncturing Plaques

Purpose: To test and validate magnetic resonance imaging (MRI) sequences for peripheral artery lesion characterization and relate the MRI characteristics to the amount of force required for a guidewire to puncture peripheral chronic total occlusions (CTOs) as a surrogate for immediate failure of endovascular therapy. Methods: Diseased superficial femoral, popliteal, and tibial artery segments containing 55 atherosclerotic lesions were excised from the amputated limbs of 7 patients with critical limb ischemia. The lesions were imaged at high resolution (75 μm3 voxels) with T2-weighted (T2W) and ultrashort echo time (UTE) sequences on a 7-T MR scanner. The MR images (n=15) were validated with micro–computed tomography and histology. CTOs (n=40) were classified by their MR signal characteristics as “soft” (signals indicating fat, thrombus, microchannels, or loose fibrous tissue), “hard” (collagen and/or speckled calcium signals), or “calcified” (calcified nodule signals). A 2-kg load cell advanced the back end of a 0.035-inch stiff guidewire at a fixed displacement rate (0.05 mm/s) through the CTOs, and the forces required to cross each lesion were measured. Results: T2W images showed fat as hyperintense and hardened tissue as hypointense. Calcium and thrombus appeared as a signal void in conventional MRI sequences but were easily identified in UTE images (thrombus was hyperintense and calcium hypointense). MRI accurately differentiated “hard,” “soft,” and “calcified” CTOs based on associated guidewire puncture force. The guidewire could not enter “calcified” CTOs (n=6) at all. “Hard” CTOs (n=9) required a significantly higher (p<0.001) puncture force of 1.71±0.51 N vs 0.43±0.36 N for “soft” CTOs (n=25). Conclusion: MRI characteristics of PAD lesions correlate with guidewire puncture forces, an important aspect of crossability. Future work will determine if clinical MR scanners can be used to predict success in peripheral vascular interventions.

The mastoid emissary vein: an anatomic study with magnetic resonance imaging.

The mastoid emissary vein (MEV) is a small venous channel connecting the intracranial and extracranial venous systems. Most current knowledge about the MEV has been obtained through cadaver studies. This study aimed to explore the MEV in vivo, using magnetic resonance imaging (MRI). Ninety-six patients were enrolled in this study. The initial examinations used the conventional MRI sequences; contrast examinations were performed using thin-sliced sections. The MEVs were identified bilaterally in 59.3% of the 96 patients and unilaterally in 29.2%. The original site, size, and intraosseous course of the MEVs were highly variable. On coronal images, the MEVs originated from a variable height on the posterior wall of the sigmoid sinus, most frequently from the lower third of the wall. Intraosseous MEV courses were classified as straight, curved, or tortuous, with the straight type occurring most frequently. The MEVs were dominant on the right side in 51.8% of cases and on the left side in 24.7% of cases. Two patients had two MEVs on the same side. Furthermore, on eight sides (5.6%), the diploic venous channel was found to communicate with the MEV. The MEV is a structure with diverse morphologies and right-sided dominancy. MEVs should be evaluated before performing surgical and endovascular procedures around the suboccipital region.