Use Of High-resolution Magnetic Resonance Imaging Research Articles

The MRI assessment of SPECC (significant polyps and early colorectal cancer) lesions.

The development of high-resolution magnetic resonance imaging (MRI) has resulted in the ability to clearly depict the finer details of rectal wall anatomy. Careful specialist assessment of images obtained in patients with significant polyps and early rectal cancer lesions enables the identification of lesions that are confined to the bowel wall and amenable to organ preserving local excision. Currently, one-third of screen detected rectal cancers are limited to the bowel wall without nodal spread yet more than 90% undergo major excision surgery resulting in significant loss of bowel function, quality of life and at high economic cost. The SPECC initiative has highlighted the need for specialist training and accreditation of radiology specialists in precision assessment of significant polyps and early rectal cancer. The detailed assessment will enable provision of detailed roadmaps for surgeons and gastroenterologists to facilitate definitive excision of more lesions using minimally invasive endoscopic technique. Finally, the use of high resolution MRI in surveillance will enable the close monitoring of such patients where the preservation of the rectum has been achieved.

High-resolution magnetic resonance imaging of intracranial aneurysms treated by flow diversion

Abstract Object Flow diverter treatment of intracerebral aneurysms is highly successful and has low rates of morbidity and mortality. Among the primary concerns after endovascular treatment are failure to achieve aneurysm obliteration and recurrence, and close imaging follow-up is required. High-resolution magnetic resonance imaging (HRMRI) is being employed in evaluation of an increasingly wide variety of pathological conditions, but investigations into its use after flow diversion for aneurysm treatment have been limited. We present a brief overview of the literature on the use of HRMRI as a follow-up tool after aneurysm treatment using flow diversion, along with a case series describing three patients in whom we used HRMRI to assess aneurysm treatment response. Case descriptions Patient 1 presented with an ischemic stroke and was found to have an unruptured ophthalmic segment aneurysm. Patient 2 presented with subarachnoid hemorrhage from a ruptured vertebral artery pseudoaneurysm. Patient 3, on workup for possible metastatic melanoma, was found to have an unruptured posterior communicating aneurysm. All three were treated with flow diversion, and in all three cases HRMRI was used to evaluate aneurysm obliteration on outpatient follow-up. HRMRI offered excellent resolution of the parent vessel, aneurysm sac, and aneurysm wall, demonstrating decreased or loss of flow-related enhancement in the aneurysm lumen and development of aneurysm sac thrombosis. Conclusion HRMRI is a useful tool to evaluate aneurysm treatment by flow diversion and may represent an alternative to repeat digital subtraction angiography.

Spontaneous and Unruptured Chronic Intracranial Artery Dissection : High-resolution Magnetic Resonance Imaging Findings.

The aim of this article is to present high-resolution magnetic resonance imaging (HR-MRI) findings of chronic stage spontaneous and unruptured intracranial artery dissection (ICAD). From March 2012 to April 2016 a total of 29 patients (15 male and14 female, age range 37-68 years) with chronic stage spontaneous and unruptured ICAD (vertebral artery 27, posterior inferior cerebellar artery 1 and middle cerebral artery 1) were retrospectively enrolled. Patients underwent HR-MRI more than 2months (median interval 564 days, range 69-391 days) after symptom onset and were diagnosed at symptom onset or at the first imaging acquisition, which included luminal angiography and/or HR-MRI with clinical information. The HR-MRI findings were evaluated against those of luminal angiography on the basis of the lumen wall morphology, including thickening, contrast enhancement and residual dissection. The HR-MRI findings were classified into complete normalization (normal lumen and wall with or without mild enhancement, n= 6), complete normalization with minimal wall changes (focal wall thickening with enhancement but normal luminal angiography, n= 8), incomplete normalization (focal wall thickening with enhancement with dilatation and stenosis on luminal angiography, n= 4), dissecting aneurysm (fusiform aneurysm with residual dissection findings, n= 8) and occlusion (small outer arterial diameter with diffuse contrast enhancement, n= 3). The use of HR-MRI can demonstrate the distinguishing morphological features of chronic stage of spontaneous and unruptured ICAD as complete normalization, complete normalization with minimal wall changes, incomplete normalization, dissecting aneurysm and occlusion.

Evaluation of magnetic resonance imaging-negative drug-resistant epilepsy.

A structural brain lesion in patients with drug-resistant epilepsy (DRE) greatly increases the likelihood of identification of the seizure focus and ultimately seizure-free outcome following resective epilepsy surgery. In contrast, surgical outcomes of true non-lesional DRE are less favorable. Therefore, discovery of an underlying lesion is paramount in the pre-surgical work-up of patients with DRE. Over the years, the surgical treatment of pharmacoresistant epilepsy has evolved from straightforward lesional cases to include cases with hippocampal sclerosis. With the advent of magnetic resonance imaging (MRI), most cases of mesial temporal sclerosis became more easily identifiable on pre-operative neuroimaging. With the widespread use of high-resolution MRI with epilepsy protocols over the last two decades, our ability to visualize subtle structural changes has been greatly enhanced. However, there are some cases of lesional epilepsy, which remain unidentified on these routine MRIs. In such “non-lesional” refractory epilepsies, further investigation with advanced neuroimaging techniques, including metabolic imaging, as well as electrophysiological studies may help to identify the previously non-visualized focal brain abnormalities. In this review, we outline the current status for evaluation of MRI-negative DRE.

The advantage of high-resolution MRI in evaluating basilar plaques: A comparison study with MRA

ObjectiveIntracranial atherosclerosis (ICAS) is a major cause of ischemic stroke; however it is rather neglected. Vessel wall visualization by high resolution magnetic resonance imaging (HRMRI) might provide more accurate information. MethodsA total of 219 consecutive patients with acute ischemic stroke underwent MRI, MRA and proton-density weighted HRMRI. Using HRMRI, the patients were divided into 3 groups with respect to basilar plaques: no plaque (n = 85), minimal plaque (n = 72) and apparent plaque (n = 62). Demographics and characteristics were compared between the groups, and the extents of stenoses calculated from MRA versus HRMRI data were also compared. Factors potentially associated with basilar plaque were validated by multivariate analysis. ResultsPatients with apparent plaque had higher frequencies of diabetes mellitus, lower high-density lipoprotein and higher hemoglobin A1c, erythrocyte sedimentation rate and homocysteine. Of the 62 cases of apparent plaque, severe stenosis (>50%) was observed in 10 (16%) by MRA and in 27 (43%) by HRMRI, which points to overestimation of plaques by HRMRI. In addition, no stenosis was evident on MRA in 13 patients with apparent plaque even though they had up to 72% stenosis on HRMRI. After adjusting for covariates, basilar artery apparent plaque was independently associated with old age, previous stroke, diabetes mellitus, low HDL and high levels of homocysteine. ConclusionsBasilar artery stenosis with plaque is more accurately detected using HRMRI than MRA. In addition, the associated risk factors differ somewhat. The use of HRMRI for evaluating ICAS deserves more attention.

Comparison of Anterior Cruciate Ligament Tunnel Position and Graft Obliquity With Transtibial and Anteromedial Portal Femoral Tunnel Reaming Techniques Using High-Resolution Magnetic Resonance Imaging

Using 3-dimensional high-resolution magnetic resonance imaging (MRI), we sought to compare femoral and tibial tunnel position and resultant graft obliquity with single-bundle anterior cruciate ligament (ACL) reconstruction using transtibial (TT) or anteromedial (AM) portal femoral tunnel reaming techniques. Thirty patients were prospectively enrolled after primary, autogenous bone-patellar tendon-bone ACL reconstruction by 2 groups of high-volume, fellowship-trained sports medicine surgeons. With the TT technique, an external starting point was used to maximize graft obliquity and femoral footprint capture. By use of high-resolution MRI and imaging analysis software, bilateral 3-dimensional knee models were created, mirrored, and superimposed. Differences between centroids for each femoral and tibial insertion, as well as corresponding ACL/graft obliquity, were evaluated with paired t tests and 2-sided Mann-Whitney nonparametric tests, with P < .05 defined as significant. No significant differences were observed between groups in position of reconstructed femoral footprints. However, on the tibial side, AM centroids averaged 0.8 ± 1.9 mm anterior to native ACL centroids, whereas the TT group centered 5.23 ± 2.4 mm posterior to native ACL centroids (P < .001). Sagittal obliquity was closely restored with the AM technique (mean, 52.2° v. 53.5° for native ACL) but was significantly more vertical (mean, 66.9°) (P = .0001) for the TT group. In this clinical series, AM portal femoral tunnel reaming more accurately restored native ACL anatomy than the TT technique. Although both techniques can capture the native femoral footprint with similar accuracy, the TT technique requires significantly greater posterior placement of the tibial tunnel, resulting in decreased sagittal graft obliquity. When a tibial tunnel is drilled without the need to accommodate subsequent femoral tunnel reaming, more accurate tibial tunnel position and resultant sagittal graft obliquity are achieved. Level III, retrospective comparative study.

Magnetic resonance imaging as a novel method of characterization of cutaneous photoaging in a murine model

Environmental ultraviolet (UV) exposure exacts a significant toll annually in terms of overall morbidity and undesirable esthetic effects of skin aging. In order to establish the molecular and pathologic basis of this process, the murine model of ultraviolet B (UVB)-induced aging has long been used with reproducibility and success. Although morphometric and histological endpoints have been useful tools to describe this model historically, they fail to allow for the real time monitoring of the aging process, and do not fully account for effects of the in vivo environment on cutaneous strata with aging. The objective of the present study was to evaluate the ability of high-resolution magnetic resonance imaging (MRI) to characterize the murine model of photoaging throughout the aging process. Six-week-old male nu/nu mice were exposed to narrow-band UVB at 30 min intervals five times weekly for 10 weeks, resulting in a characteristic photoaged morphometric result. MRI scans were performed using a 7 tesla (7 T) small animal imaging platform at pre-exposure baseline at 4 and 10 weeks. Histological analysis of full-thickness biopsies taken in 10 week photoaged mice was correlated with MRI findings, and was compared against control animals receiving no ultraviolet radiation. MRI studies revealed a statistically significant prominent evolution of epidermal hyperplasia at 4 weeks versus baseline and at 10 weeks compared to 4 week values (0.172 +/- 0.017 mm versus undetectable, P < or = 0.05; 0.258 +/- 0.007 versus 0.172 +/- 0.017 mm, P < or = 0.05, respectively). A parallel trend of dermal hyperplasia which approached statistical significance was likewise noted at 10 weeks compared to baseline values (0.420 +/- 0.073 versus 0.295 +/- 0.078 mm, P = 0.06). Histology confirmed the progressive epidermal hyperplastic change characterized by MRI findings. This study validates the novel use of high-resolution MRI for study of the murine photoaging model and establishes its potential to describe progressive cutaneous pathology in such an experimental setting.

High Resolution Magnetic Resonance Imaging of Excised Atherosclerotic Carotid Tissue: The Effects of Specimen Temperature on Image Contrast

Previous Magnetic Resonance (MR) studies of carotid endarterectomy (CEA) specimens have been directed at interpreting image contrast to determine plaque composition and stability. Such studies may give misleading results since it is believed that the acquired MR data is affected by the conditions used to store the excised tissue. This has been investigated in a high-resolution imaging study of the changes in contrast occurring with a change in specimen temperature. MR images were acquired from 20 CEA specimens. The initial MR examination was made within four hours of excision in tissue maintained and imaged at body temperature. Specimens were subsequently cooled and then re-examined at different times. The MR data was interpreted by comparison with histology obtained from equivalent sections. With the exception of signals arising from blood, changes in MR image contrast occurring in the 24-hour period after the CEA were relatively slight. Plaque lipid T2-weighted image intensity was initially relatively hyperintense in some samples and decreased with time on cooling reflecting a decrease in the lipid transverse (T2) relaxation time. High-resolution imaging allowed a detailed description of plaque calcification and showed that clot retraction was probably responsible for the marked change in the distribution of signals assigned to intraluminal blood. The use of high-resolution MR imaging to examine freshly excised specimens at body temperature showed previously unreported image features. This is important in the design of in vivo MR studies directed at assessing plaque stability by identifying the composition of the atheromatous tissue.

Biomarkers of atherosclerosis and the potential of MRI for the diagnosis of vulnerable plaque

Atherosclerosis is a chronic inflammatory vascular disease. As it is an inflammation process, many cellular and molecular events are involved at each step of the progression of atherosclerosis from an early fatty streak lesion to a highly dangerous rupture-prone plaque. Magnetic resonance imaging (MRI) is a well-established diagnostic tool for many kinds of chronic inflammation in various systems and organs, and recent improvements in spatial resolution and contrast strategies make it a promising technique for the characterization of inflammatory vessel walls. The first part of this review will briefly introduce the main cellular and molecular processes involved in atherosclerotic lesions; the second part will focus on the use of high-resolution MRI and present-generation contrast agents for plaque characterization; and the third part will present some recent and ongoing cellular and molecular MRI studies of atherosclerosis.

Plaque Imaging and Characterization Using Magnetic Resonance Imaging: Towards Molecular Assessment

Identification of high-risk atherosclerotic lesions prone to rupture and thrombosis may greatly decrease the morbidity and mortality associated with atherosclerosis. High-resolution magnetic resonance imaging (MRI) has recently emerged as one of the most promising techniques for the non-invasive study of atherothrombotic disease, as it can characterize plaque composition and monitor its progression. The development of MRI contrast agents that specifically target components of the atherosclerotic plaque may enable non-invasive detection of high-risk lesions. This review discusses the use of high-resolution MRI for plaque detection and characterization and the potentials of "Molecular Imaging" using a variety of molecules present in atherosclerotic plaques that may serve as targets for specific contrast agents to allow the identification of high-risk atherosclerotic lesions in-vivo. Ultimately, such agents may enable treatment of "high-risk" patients prior to lesion progression and occurrence of complications.

Automated detection of prostatic adenocarcinoma from high-resolution ex vivo MRI

Prostatic adenocarcinoma is the most commonly occurring cancer among men in the United States, second only to skin cancer. Currently, the only definitive method to ascertain the presence of prostatic cancer is by trans-rectal ultrasound (TRUS) directed biopsy. Owing to the poor image quality of ultrasound, the accuracy of TRUS is only 20%-25%. High-resolution magnetic resonance imaging (MRI) has been shown to have a higher accuracy of prostate cancer detection compared to ultrasound. Consequently, several researchers have been exploring the use of high resolution MRI in performing prostate biopsies. Visual detection of prostate cancer, however, continues to be difficult owing to its apparent lack of shape, and the fact that several malignant and benign structures have overlapping intensity and texture characteristics. In this paper, we present a fully automated computer-aided detection (CAD) system for detecting prostatic adenocarcinoma from 4 Tesla ex vivo magnetic resonance (MR) imagery of the prostate. After the acquired MR images have been corrected for background inhomogeneity and nonstandardness, novel three-dimensional (3-D) texture features are extracted from the 3-D MRI scene. A Bayesian classifier then assigns each image voxel a "likelihood" of malignancy for each feature independently. The "likelihood" images generated in this fashion are then combined using an optimally weighted feature combination scheme. Quantitative evaluation was performed by comparing the CAD results with the manually ascertained ground truth for the tumor on the MRI. The tumor labels on the MR slices were determined manually by an expert by visually registering the MR slices with the corresponding regions on the histology slices. We evaluated our CAD system on a total of 33 two-dimensional (2-D) MR slices from five different 3-D MR prostate studies. Five slices from two different glands were used for training. Our feature combination scheme was found to outperform the individual texture features, and also other popularly used feature combination methods, including AdaBoost, ensemble averaging, and majority voting. Further, in several instances our CAD system performed better than the experts in terms of accuracy, the expert segmentations being determined solely from visual inspection of the MRI data. In addition, the intrasystem variability (changes in CAD accuracy with changes in values of system parameters) was significantly lower than the corresponding intraobserver and interobserver variability. CAD performance was found to be very similar for different training sets. Future work will focus on extending the methodology to guide high-resolution MRI-assisted in vivo prostate biopsies.

Protocol for volumetric segmentation of medial temporal structures using high‐resolution 3‐D magnetic resonance imaging

Quantitative analysis of brain structures in normal subjects and in different neurological conditions can be carried out in vivo through magnetic resonance imaging (MRI) volumetric studies. The use of high-resolution MRI combined with image post-processing that allows simultaneous multiplanar view may facilitate volumetric segmentation of temporal lobe structures. We define a protocol for volumetric studies of medial temporal lobe structures using high-resolution MR images and we studied 30 healthy subjects (19 women; mean age, 33 years; age range, 21-55 years). Images underwent field non-homogeneity correction and linear stereotaxic transformation into a standard space. Structures of interest comprised temporopolar, entorhinal, perirhinal, parahippocampal cortices, hippocampus, and the amygdala. Segmentation was carried out with multiplanar assessment. There was no statistically significant left/right-sided asymmetry concerning any structure analyzed. Neither gender nor age influenced the volumes obtained. The coefficient of repeatability showed no significant difference of intra- and interobserver measurements. Imaging post-processing and simultaneous multiplanar view of high-resolution MRI facilitates volumetric assessment of the medial portion of the temporal lobe with strict adherence to anatomic landmarks. This protocol shows no significant inter- and intraobserver variations and thus is reliable for longitudinal studies.