China
Africa
Explore chapters and articles related to this topic
Automated Diagnosis and Prediction in Cardiovascular Diseases Using Tomographic Imaging
Published in Ayman El-Baz, Jasjit S. Suri, Big Data in Multimodal Medical Imaging, 2019
Lisa Duff, Charalampos Tsoumpas
Echocardiography or echocardiograms are ultrasounds of the heart and can either be taken from outside the body or by passing the probe through the oesophagus. The ultrasound image is produced in real time and can give information about the structure and performance of the heart, e.g. how well it pumps blood [7, 25]. The transthoracic echocardiogram (TTEs) is the most commonly used version of this imaging technique and is taken from outside the body by placing the probe against the patient’s chest. Other types of echocardiogram include taking 3D imaging of the heart, Doppler ultrasound (used to visualise blood flow) and stress tests (for example during exercise) [25]. Sometimes contrast agents are used which enhance image quality and help assess perfusion [26]. Echocardiography is used in the diagnosis of cardiac failure, identification of congenital heart disease and detecting pulmonary arterial hypertension among other applications (Figure 4.7) [7].
Biomedical Imaging Magnetic Resonance Imaging
Published in Lawrence S. Chan, William C. Tang, Engineering-Medicine, 2019
Perfusion is a process that brings nutritive blood supply to the tissue through the arterial system and drains the metabolic byproducts into the veins. Perfusion measurement using MRI can be divided into two categories, those employing exogenous agents as a tracer, and those using water protons in the arterial blood as an endogenous label. Among exogenous agents for perfusion MRI, gadolinium chelates are most frequently used. To perform perfusion measurements, a bolus of gadolinium contrast agent is intravenously administered, followed by the rapid acquisition of a series of snap-shot images with either T2*-weighting or T1-weighting. The former is known as dynamic susceptibility contrast (DSC) imaging, while the latter dynamic contrast-enhanced (DCE) imaging. In DSC, the time-series images are processed to extract perfusion-related parameters, such as cerebral blood volume, mean transient time, and time to peak. In DCE, the images are analyzed with a pharmacokinetic model to yield a number of parameters relating to permeability, surface area, transfer constants, etc. (Jahng et al. 2014).
Advances in Magnetic Resonance Imaging for Radiation Oncology
Published in Siyong Kim, John Wong, Advanced and Emerging Technologies in Radiation Oncology Physics, 2018
Perfusion-weighted imaging provides information associated with blood supply to a tissue of interest and permeability of blood in the capillaries. The brain has been the most interesting organ analyzed in many perfusion studies because of its high demand for blood. Target parameters include cerebral blood volume (CBV), cerebral blood flow, and mean transit time. Dynamic susceptibility contrast (DSC) MRI has historically been the MRI protocol of choice for cerebral perfusion imaging because of its advantages with regard to contrast-to-noise and temporal resolution. DSC is typically acquired by a fast imaging protocol with a sampling frequency of 1 or 2 s during the first bolus passage of an intravenously administered gadolinium-chelated contrast agent. The voxelwise T2- or T2*-weighted temporal profiles are subsequently analyzed. Despite a long history of development and clinical use, DSC faces several challenges in the scenario of quantification for longitudinal studies or comparative studies across institutions, such as partial volume effect, determination of arterial input function, and compensation of extravasation (Knutsson et al., 2010; Willats and Calamante, 2013).
Brain oxygenation during multiple sets of isometric and dynamic resistance exercise of equivalent workloads: Association with systemic haemodynamics
Published in Journal of Sports Sciences, 2022
Andreas Zafeiridis, Anastasios Kounoupis, Stavros Papadopoulos, Aggelos Koutlas, Afroditi K Boutou, Ilias Smilios, Konstantina Dipla
This is the first study to compare brain oxygenation responses between isometric and dynamic-RE of similar exercise characteristics. We hypothesized that changes in cerebral oxygenation and blood volume (tHb) would be higher during the dynamic-RE protocol than in isometric-RE of similar exercise characteristics, as previous studies showed higher CO and muscle activity during dynamic than isometric RE (Lewis et al., 1985; Vedsted et al., 2006). In contrast, we observed that the pattern of change in prefrontal NIRS parameters was consistently similar between the protocols, despite their marked differences in systemic haemodynamics (Figure 3). The fact that the type of contraction did not differentially affect the oxygenation and blood volume responses during isometric and dynamic-RE of similar exercise characteristics is a unique observation indirectly inferring to relatively similar changes in (i) brain response to maintain a predetermined force and (ii) cerebral haemodynamic response (oxygenation, perfusion). The comparable increases in O2Hb and tHb also imply that cerebral hyper-perfusion does not differ between the two RE-protocols. The lack of difference in cerebral oxygenation between the isometric and dynamic-RE in our study may be attributed to well-matched exercise characteristics. Thus, the type of contraction per se during RE does not appear as a contributing factor to cerebral oxygenation and blood volume responses when the exercise characteristics are well matched. Up to date, the one study that compared cerebral oxygenation between isometric- and dynamic-RE (Matsuura et al., 2011) used a single exercise set and did not match the protocols for either intensity, duration or workload; factors that may affect cerebral oxygenation/blood flow (Bhambhani et al., 2014; Korotkov et al., 2005).
Review of pulmonary emboli and techniques for their mechanical removal to inform device design
Published in Journal of Medical Engineering & Technology, 2020
Jessica Brand, Roger McGowan, Amit Nimunkar
A third, less common PE detection technique is ventilation-perfusion scanning. During the ventilation scan, patients inhale radioisotopes that provide visualisation of airflow into the lungs. During the perfusion scan, patients are injected with radioisotopes that provide visualisation of blood flow through the arteries [11]. Though effective, it cannot be performed on critically ill patients or patients with cardiopulmonary disease. Further, it typically requires follow-up x-ray imaging [1,11].
Validation of a non-invasive imaging photoplethysmography device to assess plantar skin perfusion, a comparison with laser speckle contrast analysis
Published in Journal of Medical Engineering & Technology, 2021
David Allan, Nachiappan Chockalingam, Roozbeh Naemi
Whilst LASCA and iPPG can be said to be measuring two separate measurements namely the red blood cell velocity (LASCA) and red blood cell volume (iPPG) they can both be said to be measuring perfusion. Perfusion is defined as the rate at which blood is supplied to the soft tissues of the body.