Instrumentation and Accessories

CHAPTER 4


Instrumentation and Accessories



CHAPTER OBJECTIVES


After completing this chapter, the reader will be able to perform the following:


image Identify the need for radiographic catheters


image Identify how catheters are sized using the Charrière gauge scale


image List the reasons for various shaped catheters


image Describe the guide wire used to move and place the catheter in the correct location


image Describe the use of needles during advanced procedures


image Identify the accessory items that might be found in the interventional suite


image Define the use of prepackaged and sterilized procedure trays


Catheters used during diagnostic radiography act as pipelines for transporting the contrast agent from an external source to a location within the body. In special procedures, the instillation of contrast material by catheters allows the radiologist to selectively demonstrate specific anatomic areas. The most common use of catheterization is during vascular and cardiac interventional radiography (angiography), although catheters can also be used in many other nonvascular special radiographic procedures.



CATHETERS


Catheterization offers some definite benefits in radiography. When selective angiographic procedures are performed, the amount of contrast agent delivered to the patient is reduced. In these cases, a smaller amount of contrast agent delivered to a specific area through a catheter will maintain the proper concentration for good radiographic visualization. Direct injection into a remote vessel with the bolus traveling through the circulatory system to a specific location requires that a large amount of contrast material be injected to offset the dilution that occurs. If less contrast medium is used, the procedure is easier for the patient to tolerate; fewer subjective and objective symptoms are produced, and the patient is more relaxed and cooperative during the procedure. Other advantages of catheterization include the possibility of biopsy and the ability to measure pressures within the lumen of vessels or directly from the chambers of the heart.


Catheters are simply tubes of varying lengths and inside diameters with holes in each end that allow the contrast agent to flow through. Originally, catheters were adaptations of ureteral catheters that were constructed of rubber, but this soon gave way to the various thermoplastic catheters manufactured today. Catheters are manufactured out of Teflon, polypropylene, polyurethane, and polyethylene. Each of these materials possesses different characteristics that make them suitable for different procedures (Box 4-1). One major advance in catheter manufacturing was the development of the radiopaque polyethylene catheter, which allowed the radiologist to follow the path of the catheter through the body to its destination. Radiopaque catheters usually have different characteristics than the nonopaque varieties.



BOX 4-1   Advantages of Various Catheter Materials





































Teflon Polyurethane Polyethylene
Good memory—retains shape High tissue compatibility High tissue compatibility
  Increased lumen diameters Contains no additives Soft and flexible
High material strength Increased flow rate  
Stiffer than other materials Low thrombogenicity Better torque than polyurethane
Larger inner diameters Ease of insertion and placement  
Higher potential to kink Gas sterilized only  
  Low incidence of tissue trauma  


A wide variety of catheters and catheter systems are available for use during special procedure radiography. These range from the simple straight catheter with one end hole to complex catheter systems designed to perform more than one function. A discussion of every type of catheter and catheter system is beyond the scope of this textbook. However, the companies that manufacture catheters and accessories will provide catalogs illustrating their product lines. In most cases, the catalogs include data sheets that usually illustrate and reference each product and provide a short description of each catheter or accessory. These companies are also represented on the Internet and provide online catalogs with descriptions of their product lines. They also provide easy-to-use search engines to aid in finding a particular product.


All catheters manufactured today are disposable; that is, they are designed to be used once and then discarded. Some accessory items are still manufactured as “reusable.” These items are designed to be cleaned, repackaged, and sterilized after the procedure. These must be inspected carefully during the cleaning process for any visible flaws. If any are noted, the item should be discarded.


The choice of the catheter or catheter system is made by the physician performing the procedure and is usually designated in the advanced procedure or catheterization laboratory procedure protocols. An understanding of the various standard catheters that are available is necessary. The interventional radiographer often is responsible for the ordering and maintenance of materials including the catheters used in the various procedures.


In some research institutions catheters are custom made by the physician to meet the specifics of the procedure being studied. Catheter tubing is available from certain manufacturers and can be custom formed. Appendix 1 illustrates the method of specialized catheter formation from standard catheter tubing.



Size


Catheter sizes are expressed in inches or millimeters or by French number.


The gauge scale known as the French scale was developed by Charrière, a French instrument maker (1803-1876). On Charrière’s gauge scale, 1 Charrière (or 1 French [1F]1) is equal to a diameter of ⅓ mm, with each consecutive Charrière differing from the previous one by ⅓ mm. Table 4-1 lists the millimeter conversions for French numbers from 1 to 30.



If the diameter is expressed in inches, it is necessary to know that 1 in = 25.4 mm. To convert from inches to millimeters, simply multiply the number of inches by 25.4. For example, if the catheter diameter is 0.056 in, the conversion to millimeters is accomplished by multiplying 0.056 by 25.4 to give 1.42 mm as the catheter diameter.


Figure 4-1 illustrates a gauge scale that was used which listed size specifications for cardiovascular catheters, facilitating the conversion from inches to millimeters or to French size. The gauge scale also shows the relative sizes of various catheters from 3 French to 34 French. Table 4-2 lists the size specifications for a selection of both standard and thin-walled cardiovascular catheters.



TABLE 4-2


Size Specifications for Cardiovascular Catheters


































































































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Feb 27, 2016 | Posted by in GENERAL RADIOLOGY | Comments Off on Instrumentation and Accessories

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Standard Wall Thin Wall
  Inside Diameter Outside Diameter Needle Equivalent   Inside Diameter Outside Diameter Needle Equivalent
French Size in mm in mm ID OD French Size in mm in mm ID OD
3 0.014 0.36 0.039 1.00 23+ 20+              
4 0.018 0.46 0.052 1.33 22+ 18+ 4 0.023 0.58 0.052 1.33 20 18+
5 0.026 0.66 0.065 1.67 19 16 5 0.034 0.86 0.065 1.67 19+ 16
6 0.036 0.91 0.078 2.00 18+ 15+ 6 0.046 1.17 0.078 2.00 17+ 15+
7 0.046 1.17 0.091 2.33