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Central nervous system
Published in A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha, Clark’s Procedures in Diagnostic Imaging: A System-Based Approach, 2020
A Stewart Whitley, Jan Dodgeon, Angela Meadows, Jane Cullingworth, Ken Holmes, Marcus Jackson, Graham Hoadley, Randeep Kumar Kulshrestha
Cerebral angiography may be performed using CT, MRI or direct catheter angiography. Cerebral angiography demonstrates the cerebral blood vessels by opacifying them with a suitable contrast agent. Intra-arterial angiography is normally carried out following selective placement of an angiographic catheter in either a carotid or vertebral artery, following catheterisation of a femoral artery using the Seldinger method. A contrast injector may be employed that enables a bolus of contrast to be injected in a controlled and repeatable fashion. However, hand injection is commonly used, as sufficient pressure can be applied to overcome the patient’s blood pressure and it may be quicker than repeatedly connecting the injector pump. Close co-operation with the radiologist is necessary to obtain optimal timing between injection and the first exposure. The acquisition of one or more mask images allows for image optimisation in the case of movement artefact.
Development of a new nanocrystalline alloy for X-ray shielding
Published in Radiation Effects and Defects in Solids, 2018
J. H. Cho, H. K. Lee, M. S. Kim, J. D. Rhim, Y. J. Park
Fluoroscopy uses very low tube voltages (<10 mA) that are similar to those used in simple radiography (80–100 kV); however, a patient cannot avoid being exposed in the long term by scattered rays (28). Therefore, patients receiving fluoroscopy wear a lead apron to decrease their overall exposure. However, the apron causes many difficulties during testing because it is cumbersome. Studies have been done on radiation exposure during fluoroscopy. During transfemoral cerebral angiography, the average effective dose was 22.6 mSv. It was not possible to measure the effective dose during GDC coil embolization; however, it is assumed that the effective dose would be substantially higher because the average entrance dose is about 2264 mGy (29). It was previously reported that about 95% of scattered rays can be blocked by wearing an apron with a lead equivalent 0.25 mmPb. This study does not deal with the shielding of scattered X-rays; however, it is believed that about 95% of scattered rays can be blocked by wearing the shielding fiber. The thickness of the new shielding fiber is similar to the thickness of lead-based garments; however, the new fabric is much lighter and, thus, more comfortable to wear.
Power and limit of MRI to investigate blood and cerebro spinal fluid dynamics in the cranio spinal system
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2019
CSF and blood flows circulate in the cranio spinal compartments. The main “motor” of these flows is the heart but respiratory modulate the amplitude of the flows. We can see an MRI cerebral angiography used to select (red line) the level of quantitative velocity acquisition (EPI PCMRI). EPI PC shows arterial flows in white intensities and venous flows in black intensities. Our home-made post processing software shows an example of an internal carotid artery flow change during cardiac cycle and breathing (Figure 1).
Computer-assisted surgery in medical and dental applications
Published in Expert Review of Medical Devices, 2021
Yen-Wei Chen, Brian W. Hanak, Tzu-Chian Yang, Taylor A. Wilson, Jenovie M. Hsia, Hollie E. Walsh, Huai-Che Shih, Kanako J. Nagatomo
Alongside the development of stereotaxy, advancements in neuroimaging have been critical to the development of image-guide navigation. Wilhem Roentgen’s 1895 discovery of x-rays is considered the advent of neuroimaging, as neurosurgeons promptly began investigating how to use skull x-rays as a tool to identify structures within the skull [10]. In 1918, Walter Dandy first described ventriculography, or the air ventriculogram, which used injection of air into the ventricles to allow visualization of lesions/masses near the ventricles on skull x-rays [11]. In 1927, cerebral angiography was utilized by Egas Moniz to allow direct visualization of intracranial vascular lesions as well as indirect localization of other lesions by evaluating the displacement of vessel anatomy from normal anatomy. In the late 1980s, advances in computed tomography (CT) and magnetic resonance imaging (MRI) image acquisition finally allowed for direct visualization of brain/spine parenchyma, enabling the detection of small central nervous system lesions, even if they did not cause significant displacement to the ventricular or vascular systems. Combining these new high-resolution cross-sectional neuroimaging modalities with rapidly evolving computer technology fueled the development of early neuronavigation systems, which, given historical context, have been referred to as ‘frameless’ stereotactic systems. Aside from the obvious benefit of allowing each surgery to be personalized to the patient’s unique anatomy as defined by the patient’s preoperative imaging studies, frameless stereotactic neuronavigation systems offered neurosurgeons greater operative approach flexibility by removing the mechanical limitations created by fixing a rigid frame to the patient’s head [12]. Given these advantages, neuronavigation systems were rapidly adopted by major US academic medical centers through the 1990s and became ubiquitous at tertiary hospitals with neurosurgical coverage by the early 2000s.