Ch 23 Interventional Radiology and endoscopy Flashcards
Define interventional radiology
Define interventional endoscopy
Interventional radiology - use of contempory imaging modalities to gain access to different structures throughout the body or to deliver therapeutic materials
Interventional endoscopy uses endoscopes +/- fluoro to facilitate access to different structures, most commonly through natural orifices
What should OR tables be made of to facilitate fluoroscopy?
Carbon fibre or plexiglas
What form of fluoroscopy is recommended for vascular procedures?
Digital subtration angiography
Takes an initial non-contrast image and then subtracts this from all further images during a run
What type of scopes are recommended for urinary tract endoscopy in female and male dogs?
Female - 30degree rigid scope ranging from 1.9-6.5mm
Male - flexible endoscope 2.5-2.8mm diameter.
Can also be used to gain ureteral access
Using a rigid scope has been describe into male dogs via percutaneous perineal access
When gaining vascular access, why is a cut down preferred for arterial vessels?
Permits ligation (standard) or repair (rarely) to prevent post-op haemorrhage
What are the two techniques for gaining vascular access?
Modified Seldinger technique - uses a simple needle (no stylet) with single wall puncture
Seldinger technique - An arterial needle with stylet is used, double wall puncture, stylet removed and needle is withdrawn until bevel is within lumen and blood flows
In both cases the guidewire is then placed and the needle removed
What is the typical needle and guide wire sizes used for vascular access in larger vessels?
18/19g needle and 0.038-0.035 inch guide wire
What are the benefits of introduced sheaths?
Allow safe, controlled, confluent dilation of the entry vessel, protection from luminal damage and haemorrhage
Convenient side ports for flushing or administering contrast
Check flow diaphragm to prevent back-bleeding
What is unique about the sizing of sheaths?
Named for their internal diameter (a 7Fr sheath will fit over a 7Fr dilator)
Name the following selective catheters
A - marker pigtail catheter (radiopaque markers, multiple fenestrations for rapid contrast injection)
B - Rim (reverse-curve) catheter (For accessing vessels at very acute angles)
C - Cobra-type catheter (gentle bend facilitating access into first-order arterial branches off the aorta or vena cava)
What are the two forms of balloon catheters used for interventional procedures?
Low-pressure occlusion balloons (temporary occlusion, redirect embolisation materials, flow-directed to facilitate access)
High-pressure balloon angioplasty catheters - filled with dilute contrast under pressure to dilate and efface strictures or stenoses
What are the three categories of stents?
Metallic vs non-metallic
Self-expanding vs balloon explandable
Covered vs uncovered
Name the following stents
A - stainless steel mesh SEMS
B - Nitinol mesh SEMS
C - Nitinol laser-cut SEMS
D - Silicon-covered nitinol mesh stent graft
E - Polyester covered mesh stent graft
F - BEMS compressed on percutaneous transluminla angioplasty balloon
G - BEMS after dilation
SEMS = self-explanding mesh stent, BEMS = balloon-expandable mesh stent
What are the various properties of mesh va woven/braided vs laser cut metallic stents
Mesh - Typically reconstrainable, have a variable degree of foreshortening
Woven - Not reconstrainable, minor foreshortening (rarely used, no significant advantage over mesh)
Laser cut - Shape memory nitinol (on reaching body temp, changes properties and resumes original diameter and length). Typically non-reconstrainable, minimal foreshortening. Most commonly used in urethra or vasculature but may have excessive rates of fracture within the trachea
What are the disadvantages of covered stents?
What are their main uses in vet med?
Disadvantages
- increased cost
- increased material
- increased migration rates
- larger delivery systems
- can cause occlusion of adjacent structures
Uses
- Recurrent strictures or malignancies that have grown through an uncovered stent