4. specialty/IR procedures

describe the set up for bi-plane fluoro

two c arms set up at 90 degrees from each other

in bi plane fluoro, they don’t fire at the same time. explain what happens instead + why

to avoid scatter, the tubes alternate exposing every 3 ms

what is digital subtraction angiography

manipulation of digital images to remove other structures so we’re able to see contrast-enhanced vessels

what does DSA do to contrast resolution

increases it

what does DSA do to spatial resolution

decreases it

describe the DSA process

scout image is taken, contrast-enhanced images are then taken, then we use post-processing to overlap both images and remove the structures that the rad doesn’t want to see

what units are used for the length of access devices

cm or mm

what units are used for outer diameters of access devices

french

one french size = ___ mm

0.33

a needle’s outer diameter is referred to as a ___

gauge

small gauge = bigger or smaller outer diameter

bigger

needles used for radiography procedures are referred to as ____ needles

cannulated

describe the structure of a cannulated needle

contain a solid core inner stylet + tube-like outer trocar

describe how a cannulated needle works after it’s inserted into something like a vessel

inner (solid) stylet is removed, the outer (tube-like) trocar is left in place = leaves a tunnel into the vessel and allows the insertion of other things like guidewires

list the two types of needle tips

blunt, beveled

role of blunt tip needles

draw up meds from vials

role of beveled tip needles

insertion into pt skin

smaller needle gauge = ___ outer diameter (larger or smaller)

larger

smaller needle gauge = thinner or thicker needle

thicker

outer diameter of a needle determines the size. why do we care about the value for the inner diameter

helps determine which size guidewire to use

criteria for a good guidewire

be stuff enough to carry a catheter into a vessel, be flexible enough to pass along the curves of a vessel, have a soft tip to avoid perforation, have a straight/curved/J shaped tip to allow the user to steer the wire into a vessel

how long are guidewires

100-150cm

guidewires need to be how much longer than the catheter used

10-20cm

why do we want the guidewire to be longer than the catheter

so it doesn’t get lost within the catheter during insertion into the pt

diameter of common guidewires

0.023-0.038 inches

what is the most common guidewire diameter

0.035 inches

the most common guidewire diameter is 0.035 inches. what size needle is this compatible with

18g

most guidewires of made of what materials

stainless steel, or nitinol with a teflon or heparin coating

role of dilators

enlarge a puncture site for easier access to a vessel by a catheter

how many dilators are used on one puncture site

2-3

disadvantages of dilators

the vessel must be dilated one french size larger than the catheter to facilitate vessel opening, there’s a increased risk of post-procedural hematoma

how are catheters used with guidewires

catheter is threaded over the guidewire

what are catheters made out of

polyethylene, polyurethane, teflon

what units is the outer diameter of a catheter measured in

french sizes

how do we calculate the outer diameter of a catheter in mm instead of french sizes

divide the french size by 3

catheters have an end hole but also side holes. what is the role of the side holes

increase the rate of injection + minimize the possibility of the catheter unwinding in a vessel, reduces the risk of injury when high-flow contrast is injected

when are sideholes on catheters contraindicated +why

for embolization procedures; there is an increased risk of thrombus formation around the catheter holes and we don’t want that

T or F: smaller catheter size = slower injection rate

true

when do we use introducer sheaths

when there may be multiple catheter exchanges through the access site

how are introducer sheaths used in regards to other equipment like guidewires

threaded over guidewires

once an introducer sheath is in place, how do we use it

other supplies like guidewires and catheters can enter the pt through the sheath’s hub

role of the sidearm extension port of a sheath

used to infuse meds, monitor BP, or inject contrast media

in regards to sheaths, do we focus on the inner or outer diameter for the measurement

inner

the inner diameter of sheaths is in what units

french

a 6Fr sheath will accommodate what size catheter (or less)

6Fr

describe the seldinger technique for percutaneous access

beveled cannulated needle is inserted into the skin and through both walls of an artery, then withdrawn until blood is seen so we know we’re in the vessel. inner cannula is removed so only the outer tube is in place = holding the vessel open. guidewire goes through the needle and into the artery. needle removed. catheter threaded over the guidewire and advanced into the vessel, then guidewire removed

what is the modified seldinger technique

the same procedure, but the needle only pierces the anterior wall of an artery, not both = reduced risk of vessel trauma and bleeding

what is the trochar technique used for

used for non-vascular procedures; placing tubes or drains into large/superficial/easily accessed fluid collections (ie infected sinuses, distended kidneys, ascites in the abdomen, pleural effusion)

describe the steps of the trochar technique for percutaneous access

a stiff/sharp trochar needle is housed within a catheter and used to puncture the skin + underlying tissue. under US guidance, the rad directs the system to the desired location

what are aspirations done for

for pathologies that are fluid in nature

what is a joint aspiration

removal of fluid from a joint + sent to lab to diagnose

what is ST aspiration

fluid collection of a cyst or abscess; therapeutic and diagnostic in nature

what are drainages done for

anything that is fluid filled; cysts, collections of exudate, abscesses

what is a percutaneous nephrostomy

interventional procedure to decompress a blocked renal collecting system; drain is inserted into the affected renal pelvis and kidney to alleviate hydronephrosis (distension with urine)

what are biopsies for

when there is a suspicious growth or neoplasm and we want a sample

what is a fine needle aspiration

type of biopsy; thin needle is inserted and then repeatedly moved back and forth to collect a sample of cells

what is a core needle biopsy

cylindrical column of tissue is removed; tissue integrity is maintained

what are stent insertions for

to expand/keep vessels open; placed across narrowed segments to improve flow

role of ureteral stents

used when the ureter is narrowed, which would block urine flow from kidney to bladder

describe ureteric stents shape

double-J

how does a ureteric stent work

the curled ends prevent stent migration. the stent resides in the renal pelvis and bladder to allow urinary flow

shape of esophageal stent

can be covered (malignant circumstances) or uncovered (temporary)

how does an esophageal stent work

self expanding once the outer sheath is removed. adheres to esophageal walls

complications of stents

perforation, migration