Histopathologic Techniques Grego
processing.... Drugs & Diseases > Clinical Procedures Eversion Carotid Endarterectomy Technique Updated: May 17, 2022 Author: Jovan N Markovic, MD; Chief Editor: Vincent Lopez Rowe, MD, FACS more...
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Indications Technical Considerations Outcomes Show All Periprocedural Care Patient Preparation
Monitoring & Follow-up Show All Technique Approach Considerations
Incision Exposure Determination of Safety of Cross-Clamping Removal of Plaque Anastomosis Closure Show All Media Gallery References Technique Approach Considerations Two techniques are commonly used for carotid endarterectomy (CEA): patch angioplasty and eversion CEA (eCEA). In the former, a longitudinal arteriotomy is made and then carried beyond the plaque both proximally and distally. This is typically followed by the use of a patch angioplasty closure; several randomized trials demonstrated that clinically relevant outcome measures favored patch closure over primary closure. [34, 35, 36, 37, 38]
Histopathologic Techniques Grego
Imaging plays a key role in the diagnosis of central nervous system (CNS) metastasis. Imaging is used to detect metastases in patients with known malignancies and new neurological signs or symptoms, as well as to screen for CNS involvement in patients with known cancer. Computed tomography (CT) and magnetic resonance imaging (MRI) are the key imaging modalities used in the diagnosis of brain metastases. In difficult cases, such as newly diagnosed solitary enhancing brain lesions in patients without known malignancy, advanced imaging techniques including proton magnetic resonance spectroscopy (MRS), contrast enhanced magnetic resonance perfusion (MRP), diffusion weighted imaging (DWI), and diffusion tensor imaging (DTI) may aid in arriving at the correct diagnosis. This image-rich review discusses the imaging evaluation of patients with suspected intracranial involvement and malignancy, describes typical imaging findings of parenchymal brain metastasis on CT and MRI, and provides clues to specific histological diagnoses such as the presence of hemorrhage. Additionally, the role of advanced imaging techniques is reviewed, specifically in the context of differentiating metastasis from high-grade glioma and other solitary enhancing brain lesions. Extra-axial CNS involvement by metastases, including pachymeningeal and leptomeningeal metastases is also briefly reviewed.
Although magnetic resonance imaging (MRI) is more sensitive than computed tomography (CT) for detection of brain metastases, CT remains a vital tool for initial work-up and perioperative management. Advanced MRI techniques such as magnetic resonance spectroscopy (MRS), magnetic resonance perfusion (MRP), diffusion weighted imaging (DWI), and diffusion tensor imaging (DTI) may also be utilized to help distinguish brain metastases from other pathologies, and also to monitor treatment response. Nuclear medicine studies including 18 fluorodeoxyglucose positron emission tomography (FDG-PET) and other molecular imaging may play a larger role in the future.
This review discusses imaging features common to brain metastases, with a focus on CT and MRI. The role of advanced MRI techniques in the diagnosis and management of brain metastases is discussed, as is the utility of these techniques for problem solving in patients with de novo brain masses.
MR perfusion may be performed using a variety of methods. Most commonly, perfusion imaging is acquired during administration of gadolinium-based contrast while repeatedly sampling signal from brain tissues of interest. This may be performed using T2-weighted or T2FNx01-weighted dynamic susceptibility contrast (DSC) or T1-weighted dynamic contrast-enhanced (DCE) technique. Technical differences between these techniques are beyond the scope of this review. Additionally, newer methods of evaluating brain perfusion using arterial spine labeling (ASL), which do not require contrast administration, are rapidly being developed. The studies described in this section predominantly utilize DSC perfusion techniques, unless otherwise noted.
A commonly reported perfusion parameter obtained from both DSC and DCE techniques is the relative cerebral blood volume (rCBV). This is calculated by comparing the cerebral blood volume in a region of interest drawn over the lesion of concern to the CBV of an identical region of interest placed over the normal-appearing white matter in the contralateral cerebral hemisphere. Additional parameters may be calculated from perfusion studies, including evaluation of time to peak contrast level, estimation of cerebral blood flow, and estimation of capillary permeability.
To summarize, many studies have attempted to differentiate enhancing parenchymal lesions, particularly metastasis and high-grade glioma, based on advanced MRI techniques. While several individual parameters have potential to differentiate the two entities, heterogeneity of the tumor components of high-grade gliomas, and differences in histologic subtype of metastases likely limits the utility of any particular measure. Rather, careful consideration of a combination of findings from MRS, MRP, DWI, and DTI is likely the best approach to accurately diagnose the nature of a solitary enhancing parenchymal mass.[ 53 ]
Advanced MRI techniques including proton spectroscopy, perfusion, DWI, and DTI have all been evaluated primarily in the context of distinguishing brain metastases from other entities such as high-grade primary glial neoplasms, CNS lymphoma, and abscess. To date, the best means of differentiating solitary metastasis from primary high-grade glioma involves evaluating the peritumeral edema of the two lesions, either by MRS, MRP, DWI, or DTI. Additionally, though any individual parameter may not accurately distinguish the two entities, careful evaluation of the imaging findings together may lead to the correct diagnosis.
6. Bendini M, Marton E, Feletti A, Rossi S, Curtolo S, Inches I. Primary and metastatic intraaxial brain tumors: prospective comparison of multivoxel 2D chemical-shift imaging (CSI) proton MR spectroscopy, perfusion MRI, and histopathological findings in a group of 159 patients. Acta Neurochir (Wien). 2011. 153: 403-12 076b4e4f54