China
Africa
Explore chapters and articles related to this topic
Cardiovascular 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
Intravascular ultrasound (IVUS) (Fig. 9.16d) is a technique for examining the inside of a blood vessel using a tiny ultrasound transducer that is passed through the lumen of a vessel, often as part of minimally-invasive heart surgery. This plays an important role before and during interventional procedures, in providing information on the type and extent of disease, enabling the clinician to select the most appropriate interventional procedure. Unlike OCT, which may also be performed during angiography, IVUS enables visualisation of the structures beyond the lumen and the visible wall of the vessel.
Hypertension and Correlation to Cerebrovascular Change: A Brief Overview
Published in Ayman El-Baz, Jasjit S. Suri, Cardiovascular Imaging and Image Analysis, 2018
Heba Kandil, Dawn Sosnin, Ali Mahmoud, Ahmed Shalaby, Ahmed Soliman, Adel Elmaghraby, Jasjit S. Suri, Guruprasad Giridharan, Ayman El-Baz
Doppler ultrasonography (handheld, Duplex, Color, and Power) uses high-frequency sound waves generated by a transducer to measure blood flow using the Doppler Effect and blood pressure [47]. The transducer is pressed externally against the patient's skin, with gel between the transducer head and the patient's skin to act as a coupler and eliminate air and to reduce static. This painless noninvasive procedure is generally performed in a hospital radiology department by a sonographer. Intravascular ultrasound is a noninvasive, clean, safe, and inexpensive modality that offers detailed imaging of cardiac arteries [48]. However, it is noisy and cannot image gas-filled and bony structures because they absorb ultrasound waves.
New intravascular imaging techniques (optical coherence tomography”OCT” and optical frequency domain imaging”OFDI”)
Published in Ever D. Grech, Practical Interventional Cardiology, 2017
The very short wave length of light leads to extremely high speed of light compared with ultrasound, which represents the fundamental difference between optical and ultrasound-based imaging. In tissues, the speed of light is nearly 3 × 108 m/s compared with 1500 m/s for ultrasound. The ideal resolution for intravascular ultrasound (IVUS), 100 μm, requires a time delay of 100 nanoseconds to detect sound echoes. This time delay, also called time resolution, is within the range of electronic detection of IVUS machines. On the other hand, the detection of light echoes requires much higher time resolution. A time resolution of ~30 femtoseconds (3 × 1015 seconds) is required for measurement of distances with a 10 μm resolution, the typical resolution for OCT imaging. Accordingly, direct measurement of time delays between optical echoes by usual electronic means is extremely difficult and measurement methods such as interferometry are required for OCT imaging. Interferometry depends on coherence, a physical property of light waves that makes them capable of generating interference when combined.4
‘Routine intravascular ultrasound evaluation and change in stenting strategy in primary percutaneous intervention (RIST PCI)’
Published in Acta Cardiologica, 2023
Sajan Narayanan, Stigi Joseph, Anwar Chennakkadan Varghese, Rajesh Govindan Nair, Abish Sudhakar
Primary percutaneous intervention (PPCI) improves outcomes and mortality in patients who present with ST elevation myocardial infarction (STEMI) [1]. Intravascular ultrasound (IVUS) provides anatomical information about vessel diameter, lesion severity and length which are poorly defined by angiography. IVUS is superior to coronary angiography for assessment of vessel size, calcium content and lesion severity [2,3]. In studies which compared IVUS with angiographic guidance for percutaneous interventions (PCI) in stable coronary artery disease (CAD), patients who underwent IVUS-guided PCI had higher stent diameters, longer stent lengths and more number of stents implanted when compared to those who underwent PCI under angiographic guidance [4,5]. Assessment of vessel diameter and lesion length is complicated during PPCI due to the presence of thrombus layering vessel wall, spasm due to sympathetic overdrive and limited spatial resolution of angiogram. Imaging guided PCI improved overall outcomes in patients who underwent PPCI in a large registry [6].
Characterisation of patients with and without cardiac magnetic resonance imaging abnormalities presenting with myocardial infarction with non-obstructive coronary arteries (MINOCA)
Published in Acta Cardiologica, 2021
Bhupendar Tayal, Phillip Freeman, Filip Ericsson, Kristian Hay Kragholm, Niels Holmark Andersen, Andreas Hagendorff, Jens Aaroe, Peter Sogaard, Tomas Zaremba
Coronary angiography is limited in its ability to identify non-flow limiting plaque rupture and more subtle epithelial disease without the use of intravascular imaging. Previous studies have attempted to understand the mechanism of MINOCA by applying different additional coronary imaging techniques. Performing cardiac computer tomography, it is shown that patients with normal angiograms and myocardial infarction confirmed by ischaemic changes on CMR have angiographically invisible plaques in the culprit vessels [18]. Another study applied intravascular ultrasound in a cohort of patients with MINOCA and found that a significant number of patients had coronary plaque ulceration [19]. More recently, a study of 38 patients with MINOCA showed that 7 (23%) patients have ischaemic LGE changes on CMR with five of them having plaque disruption or thrombus in the coronary arteries assessed by intra coronary optical coherence tomography providing direct evidence of underlying pathogenesis of the ischaemic changes in these patients, even though they did not have any significant coronary artery stenosis [7]. During routine clinical assessment the impracticality of performing intravascular ultrasound or optical coherence tomography on all epicardial vessel, it is likely to translate into limited use of this technique in patients with otherwise (angiographically) normal coronaries.
Impact of plaque burden and composition on coronary slow flow in ST-segment elevation myocardial infarction undergoing percutaneous coronary intervention: intravascular ultrasound and virtual histology analysis
Published in Acta Cardiologica, 2021
Sreenivas Reddy, Raghavendra Rao K, Jeet Ram Kashyap, Vikas Kadiyala, Hithesh Reddy, Samir Malhotra, Ramesh Daggubati, Suraj Kumar, Hariom Soni, Naindeep Kaur, Jaspreet Kaur, Vadivelu Ramalingam
The IVUS images of all the patients enrolled in the study were recorded and stored on a DVD-ROM. The offline analysis was performed by two independent observers who had no prior knowledge of the patient details or angiograms (VK and SK). A consensus was obtained if there was discordance in the analyses by repeated off line readings. Quantitative and qualitative IVUS analysis was performed in accordance with the American College of Cardiology Clinical Expert Consensus Document on Standards for Acquisition, Measurement and Reporting of Intravascular Ultrasound Studies [27]. All the IVUS and VH analysis were done using a validated and computerised INDEC’S Echo plaque 4.3.12J software (INDEC Medical Systems, Inc., Santa Clara, CA). The culprit lesion was the smallest lumen site whereas the proximal and distal reference segments were near normal looking image slices within 10 mm distal and proximal to the lesion without any significant side branch. A vascular segment length of 10 mm, with tight stenosis as mid-point, was considered for analysis. After automatic border detection for the lumen and media-adventitia interface by the software, manually correction and confirmation done to obtain the results calculated to be displayed automatically.