China
Africa
Explore chapters and articles related to this topic
Basics of femoral and iliocaval imaging and stent evaluation
Published in Joseph A. Zygmunt, Venous Ultrasound, 2020
Jan M. Sloves, Jose I. Almeida
We contend that the abnormalities in color flow and pulsed wave Doppler techniques are useful but are also of limited value for the quantification of lesion severity. Our protocol suggests that a 50% reduction in vein caliber measured with calipers (CIV <8 mm, EIV <7 mm, or CFV <6 mm), with or without the presence of an abnormality in color flow or Doppler waveforms described herein, provides the interventionalist enough information to move directly to IVUS with venography without further testing [15,19,20]. Omitting the risks of radiation and contrast material associated with computed tomography venography and the risk of gadolinium deposition disease associated with magnetic resonance venography is a safer alternative for patients. DU using the techniques described herein needs to be correlated with IVUS imaging in a formal prospective study that also looks at clinical outcomes and quality of life measures. At present, IVUS remains the gold standard for determining iliocaval lesion severity.
Neurosurgery: Supratentorial tumors
Published in Hemanshu Prabhakar, Charu Mahajan, Indu Kapoor, Essentials of Geriatric Neuroanesthesia, 2019
Monica S. Tandon, Kashmiri Doley, Daljit Singh
These imaging modalities help to better define the relationship between the cerebral vasculature and the STT (22). They are especially useful for operative planning of meningioma surgeries. Magnetic resonance angiography (MRA) and angiography can visualize the relation of the tumor to the major blood vessels, their arterial feeders, and draining veins, displacement/encasement of these vessels by the tumor, occlusion of a sinus, collateralization in areas of sinus occlusion, and also determine whether there is a role for preoperative embolization. Magnetic resonance venography (MRV) primarily evaluates the venous system; it is very useful for determining which veins can be sacrificed and which major draining veins need to be left intact during the resection of the meningioma.
Venous thromboembolic disease in older adults
Published in Wilbert S. Aronow, Jerome L. Fleg, Michael W. Rich, Tresch and Aronow’s Cardiovascular Disease in the Elderly, 2019
Laurie G. Jacobs, Justin B. Kaplan, Ruchi Jain
Although a number of noninvasive and invasive imaging modalities can be used to diagnose DVT, proximal compression ultrasonography (CUS) is the modality of choice as it is highly accurate when performed by an experienced technician, reproducible, and less costly than others. The diagnosis of DVT is established by abnormal compressibility of the vein, which has a high sensitivity (97%) and specificity (98%) for proximal thromboses, but reduced sensitivity (73%) for distal clots (75). CUS does not detect thrombi in the iliac vein. In patients with a high pretest probability and a positive proximal CUS, treatment is recommended. In patients with a high pretest probability but a negative proximal CUS, additional testing is warranted. Repeat CUS in 1 week along with a highly sensitive D-dimer is one approach. Computed tomography (CT) or magnetic resonance imaging (MRI) may be obtained in order to image the pelvis. Magnetic resonance venography (MRV) is noninvasive but more expensive. Changes in the signal from the clot over time may allow estimation of the age of the thrombus.
An investigation of cerebral bridging veins rupture due to head trauma
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2023
Hamed Abdi, Kamran Hassani, Shahrokh Shojaei
The present study was a numerical study that used the finite element method to simulate subdural hematoma. For this purpose, the global- local method was utilized. Magnetic resonance imaging (MRI) was used for geometric modeling of the head and magnetic resonance venography (MRV) for cerebral veins. The images were taken of a young man with a healthy brain (36 years old) and another of an old man with an atrophied brain (82 years old). Figure 1 shows a cross-sectional view of the taken images. Then, initial geometric modeling was performed. Three groups of models were created to enable us to simulate subdural hematoma, evaluate the mechanism of injury in young and old people, and compare them. In the first group, global solid models were used to calculate the relative displacement between the brain and skull. The second group was the global FSI models that calculated the cerebrospinal fluid (CSF) pressure distributions due to the impact loads. The third group, local solid models, calculated the stress and strain of BVs.
Upper Limit of Retinal Nerve Fibre Layer Thickness in Patients with Pseudopapilloedema
Published in Neuro-Ophthalmology, 2022
Varsha Pramil, Mary Tam, Laurel N. Vuong, Thomas R. Hedges
Many patients, especially paediatric patients, with pseudopapilloedema have been commonly mistaken to have papilloedema.3 An initial mischaracterisation of pseudopapilloedema as true papilloedema can induce anxiety in patients and their parent. It can also lead to many unnecessary, invasive and expensive tests such as magnetic resonance imaging (MRI), magnetic resonance venography (MRV) and lumbar punctures (LP), sometimes with falsely elevated opening pressures.4 For example, in one study, 28 patients with pseudopapilloedema were mistaken to have had papilloedema over a 3-year period and underwent excessive testing/procedures and many consultations before being confirmed to have pseudopapilloedema.5 Therefore, an accurate and quick method to diagnose pseudopapilloedema is needed. Optical coherence tomography (OCT), a fast and non-invasive imaging technique used to obtain cross-sectional images of the retina and the optic nerve, may be useful in distinguishing between possible causes of optic nerve head swelling.6,7 Using OCT, previous investigators have shown increased swelling of the peripapillary retinal nerve fibre layer over time in patients with papilloedema, as opposed to pseudopapilloedema. Increased subretinal fluid near the optic nerve head has also been seen in patients with papilloedema.8–11 However, an upper limit of normal or ‘cut-off’ RNFL thickness has not been determined.
MRI detection of brain abnormality in sickle cell disease
Published in Expert Review of Hematology, 2021
Hanne Stotesbury, Jamie Michelle Kawadler, Dawn Elizabeth Saunders, Fenella Jane Kirkham
There is a broad spectrum of presentation with cerebrovascular accident (CVA) and other neurological complications in patients with sickle cell disease (SCD) [1–4]. Since the mid-1980s, magnetic resonance imaging (MRI) has been used to investigate brain pathology in SCD patients presenting with acute neurological symptoms and signs, in emergency and rehabilitation settings, and in observational cohort studies [1]. Techniques used clinically include T1-, T2-fluid attenuated inversion recovery (T2-FLAIR), T2*, susceptibility and diffusion weighted MRI, and time-of-flight angiography (MRA) and venography (MRV) (Table 1, Figure 1) The imaging has typically been interpreted qualitatively by neuroradiologists with variable degrees of specific training, using a number of different grading schemes and rating scales for MRI and MRA [5–13]. More recently, structural and hemodynamic quantitative approaches, including T1, diffusion, perfusion, quantitative susceptibility mapping (QSM), and functional MRI (Figure 1), in humans and in animal models of SCD interpreted by neuroscientists have allowed insight into potential mechanisms of neurological and neurocognitive compromise (Figure 1) [4,14–16]. The starting point for this review was a PubMed literature search of ‘magnetic’ or ‘MRI’ and ‘sickle’ over the past 5 years with screening for manuscripts related to the brain, finalized in June 2020 and supplemented with literature known to the coauthors.