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Images in Radiology: Concepts of Image Acquisition and the Nature of Images
Published in Mitul Kumar Ahirwal, Narendra D. Londhe, Anil Kumar, Artificial Intelligence Applications for Health Care, 2022
This brings us to an MRI technique that gives us exclusive information about the blood vessel and is hence termed as MR angiography when evaluating an artery and MR venography when it shows the venous mapping [14,15]. As we know already that the MRI exploits the existing magnetic properties in the body and with the use of external RF pulse it excites the tissue and the relaxation properties of varying tissues, establishing the contrast between the adjacent structures. This concept holds true for stationary tissues. Although the same magnetic excitement does also happen for the blood vessel, because of the flow, the magnetized blood would have moved out of the slice of interest and hence they appear to be hypointense on all sequences. So it is termed as no signal or “signal void” as a normal finding for a blood vessel on conventional MRI sequences. MR angiogram is a technique that renders the blood vessels bright by a special technique of magnetic saturation of the background tissues [16].
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
Venography was for a long time the only useful method of assessing the deep veins of the leg, usually for suspected deep vein thrombosis (DVT), but the side-effect of causing DVT in some patients meant it had limited use and it has now been replaced by ultrasound, which produces more useful information without significant risk. Conventional venography may occasionally be used to assess the subclavian vein (for instance suspected thrombosis related to central lines) if ultrasound is technically unsuccessful.
Introduction to medical imaging
Published in David A Lisle, Imaging for Students, 2012
MRI of veins is known as magnetic resonance venography (MRV). MRV is most commonly used in neuroimaging to demonstrate the venous sinuses of the brain. For certain applications, the accuracy of MRA and MRV is increased by contrast enhancement with intravenous injection of Gd-DTPA.
Device profile of the Vici venous stent for chronic iliofemoral venous obstruction recanalization: overview of its safety and efficacy
Published in Expert Review of Medical Devices, 2020
Jack Kingdon, Adam M. Gwozdz, Rachael Morris, Stephen A. Black, Alberto Smith, Prakash Saha
Finally, it is important to recognize that there are a number of factors that affect patency that goes beyond the type of stent used. These can be broadly divided into patient factors (thrombophilia, compliance to medication); flow-related factors (the inflow to the stented area being important), and; technical factors related to the procedure. Perhaps more so than in the arterial system, venous stents need to be precisely placed from healthy vein to healthy vein and we routinely use intravascular ultrasound to complement contrast venography to demonstrate landing zones. In addition, vessel preparation with balloon dilatation to the diameter of the stent, is required before its placement. The stent is also post-dilatated to ensure adequate expansion. Deviation from these fundamental steps may result in inaccurate stent placement, which often leads to early loss of patency, regardless of which type of venous stent is used.
Troubleshooting the difficult left ventricular lead placement in cardiac resynchronization therapy: current status and future perspectives
Published in Expert Review of Medical Devices, 2022
Jens Brock Johansen, Jens Cosedis Nielsen, Jens Kristensen, Niels CF Sandgaard
The deep seated delivery tools provide a better overview of the CS anatomy including vein collaterals through direct venography and better possibility to subselect target veins. The snare technique further enhances lead delivery in difficult target vein access and lead placement to a stable position.