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| Film Changers | Catheters | Filters | ||
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All equipment and supplies mentioned are meant to be for information only. The actual uses may vary from institution to institution. Before you use any of these products you should check with your institution for their protocols and approved uses.
There is a variety of equipment necessary to study blood vessels. In this study guide we will only be mentioning a few types. Film Changers were one of the first types of filming equipment for cardiovascular and intervention imaging. Since then a variety of film changers have become available. More institutions are getting away from film changers and are now using digital imaging, which we will go into detail later.
| First we have one of the more popular film changers-the cut film changer. Cut film changers usually contain 14 by 14-inch (35 by 35-cm) sheets of film. The film is stored in magazines. Most of them hold 20 to 30 sheets of film. You have two magazines with this system. In one you load the film, and the other receives the exposed film. To load the film, take the magazine into the darkroom and load it with the maximum number of films that the magazine will hold. To the right you will see a diagram that shows how cut film changers work. |
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Film is advanced by a roller system to the intensifying screens. Cams push the compression plates down holding the intensifying screens in close contact. This will provide a good film screen contact limiting the amount of motion. After exposure, the film is advanced to the receiver magazine (cassette). Cut film changes can expose up to 6 films a second.
Next we have roll film changers. These films are in long sheets. You still get an exposure size of 14 by 14 inches (35 by 35cm), but each image is attached to the next. These films can either be viewed in one long sheet or cut. An advantage of keeping the film in one sheet is that films don't get out of order.
Roll film changers work similar to cut film changers, except the film goes from a film-feeding spool instead of a magazine. The cams and pinch rollers advance the film, rolling the exposed film up in the take-up spool. If you want to have fast exposure rate, use the roll film changer. It can expose up to 12 films a second. This is the highest exposure rate you can get with film changers.
Another type of film changer is the cassette changer, and there is a variety available. One type has long cassettes 14 inches by 51 inches. This type of changer would give one long image of the entire filming area. A more popular type is the 14-inch by 14-inch cassette changers.
With this system, the whole cassette is advanced and the cassettes are either vacuum-sealed or stacked. The cassettes are stacked in the bin, which contains a spring. As each exposure is made, the film is pushed into the receiver portion of the bin by the push arm causing the platform in the bin to rise up. This allows the next cassette to be in position for exposure. The cassette is pushed into the receiver bin by a push arm. This system is one of the slower found in angiography suites. The maximum exposure rate with the cassette changer is 4 films a second, due mostly to the weight of the cassettes.
Film changers can either be single plane or bi-plane filming. With the single plane film changer, you get an exposure in one view at a time (i.e. AP). Many angiography suites that still use film changers use this system. Bi-plane filming is more common in areas where a lot of cerebral work is done. Bi-plane gives the advantage of having two exposures at the same time with only one contrast injection (i.e. AP and lateral views). These exposures can be made either simultaneous or alternating. Bi-plane filming is more expensive because you need to have two generators. Only one generator is needed with the single plane system.
When using bi-plane changers, you need to have a grid mounted on each to cut down on scatter radiation. The grid is usually a 12:1 linear grid. There are also filters that can be used with film changers. Two of the most popular filters are keyhole and round. The keyhole lets you image the head and neck area. The round filter lets you image just the head. When filming, you can also use magnification to help visualize smaller areas. Increasing the source image distance can do this. That is the distance of the body part to the x-ray source. To figure out the amount of magnification there is a magnification formula.
Magnification= image size or SID (source image distance) over Object size or SOD (source object distance)
Film changers need a program to tell them how to work. The program used is called a programmer. It tells the film changer how many images to film and how many to take per second. An old type of programmer is a punch card system. The program knows what to do by reading a punch card. The card contains rows of information. Commands need to be set in each row, this is done by punching out a hole in the indicated row. See the diagram for an example of a punch card.
Many of the newer programmers have a digital panel to enter the information. Instead of punching out sections of a card, one would type in what one wanted the changer to do. For example, on your read-out you might see 2221111. This translates into two films per second for 3 seconds and one film per second for 4 seconds. If you see a dash in between any of the numbers that means you have a pause of one second (no films during that second). With both types of programmers, you can tell when to inject and when to move the table.
Now that you have taken all of these films, what do you do with them? Working in one view, you will have multiple films of the same area. The only difference in each is the amount of contrast. Since all of these films are cut films, they will all have bones and arteries. To subtract the bones out of the image you can do a first order subtraction. Take your first film to use as your mask image to the darkroom. Go to your film copier or subtraction unit. You should have special film called masking film. Make the mask, which will give you a "negative" or reversal of the first image. Next take the films that you want to subtract the bones from. Position the mask film over your selected film so that your bony anatomy is subtracted out. Tape the films together and make a copy using subtraction film. The image will come out without bones, but the contrast filled vessels will still be there. This gives you an excellent way of showing the vessels of interest.
One thing to remember with film changers is that you do have some delay in filming. There is phase-in time or interrogation time. This is the time between pushing the exposure switch to the actual exposure. We also have zero time. That is the time needed for the electronics to proceed after the exposure is made. Since film changers contain intensifying screens, they must be periodically cleaned to prevent static. When film moves through the changers, static electricity is formed and shows up on your film as an artifact.
To clean most of these film changers you need to remove the compression plate. This plate is usually held in place with screws. After removing the compression plate you will need to separate the two intensifying screens. Lay the top piece face up on a flat surface. Using a soft cloth or a piece of gauze, wipe both screens with screen cleaner. After the cleaner dries, spray the screens with a silicone spray. The spray makes the surface more slippery and causes less static. Once you have finished cleaning, put the film changer back together.
Cine works similar to a movie camera. The film is advanced from the supply roll to the aperture by a pull down arm. The aperture and shutter open and an exposure is made. The aperture closes and the film is picked up and advanced to the take up spool. The shutter controls speed, and aperture size is set with the dose. Cine is more commonly used in cardiac angiography. Since it works similar to a movie camera you can get up to 30 films or frames per second. This filming speed is necessary when imaging cardiac vessels because of heart motion. To reduce patient dose cine is usually pulsed.
Digital imaging is the most common type of imaging today. Many institutions are replacing old angiographic equipment with modern digital imaging equipment. Since digital imaging is computerized, you may hear a few new terms. A pixel is a picture element that is the dots that make up the screen. Pixel drop out is black spots in the image. If you take the pixels and group them together, you have the image matrix. The matrix with digital imaging is usually 512 by 512 or 1024 by 1024, representing the number of pixels in the image. With 1024 by 1024, you have better resolution (a clearer image), because you have more pixels in the same amount of space. Digital images contain various shades of gray. These shades of gray are the frequency or dynamic range, which is the total amount of contrast on the image (maximum light to dark).
A digital exposure works differently than getting an exposure with a film changer. The exposure is made using an x-ray tube just like with taking a film. But instead of going to a film, the radiation that exits in the patient is picked up by the image intensifier (II). The image intensifier changes the different intensities of radiation exiting the patient into different intensities of light. The light is picked up by the TV camera and amplified. It is then routed to a monitor containing a cathode ray tube. The cathode ray tube (CRT) is the device in the monitor or TV that makes it possible to make a visible image. During the amplification process the image can be converted in the digital to analog converter. This only happens if you have an analog monitor. Most newer monitors are digital and this step is bypassed. Digital monitors have a higher resolution than analog monitors. The image processor also reads the signal, and the image is either displayed and/or stored. Digital images can be stored many ways: optical disk, hard disk, or tape. Digital images can also be selectively hard copied to film.
| When visualizing blood vessels, you want to have a steady even flow of contrast. This can be achieved by using contrast injectors (electromechanical injectors). An injector consists of the syringe (to hold the contrast), a heating device (to reduce contrast viscosity), the motor drive (drives the plunger into the syringe), and a control panel (to tell the injector what to do). You would first fill your syringe with contrast, attach your injector tubing and then purge all the air out of the system. The air is purged by hitting the side of the syringe while going forward with the motor drive. After purging all the air, the other end of the injector tubing is connected to the catheter by two people. One person is sterile to hook up the catheter and the other person is non-sterile to go forward with the motor drive. After you have the tubing connected to your catheter, you would set up your PSI (pounds per square inch) on the control panel. This is the amount of pressure that the catheter can take. Then set up any injector delay (there is usually some, to permit a mask image) and set your rate and volume. Volume is how much contrast you want to inject, i.e. 20 for 20, which is 20 ccs of contrast a second for a total of 20 ccs. |
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Catheters come in all shapes and sizes. Some of the more popular shapes will be shown. Before we discuss catheter shape, we need to talk about what type of material catheters are made of. Most catheters are made of one of these three types of materials: Polyethylene/Polyurethane, Teflon, or Nylon/Vinyl.
Characteristics of catheter material:
Polyethylene/Polyurethane has a low to medium coefficient of friction, medium to low torque, excellent memory and is easily reformed. This material is frequently used to make catheters that are used for selective and superselective work. Teflon has the lowest coefficient of friction of all the different materials, high torque, excellent memory, and it is not easily reformed due to the fact that it can withstand high temperatures. For this reason this material is used to make sheaths and dilators. There are some catheters made from Teflon. These are mostly straight catheters. Nylon/Vinyl has a low coefficient of friction, medium to high torque, excellent memory, and is not easily reformed. Many catheters are made of nylon because the material has some kink resistance. You will find this material used in catheters that you want to inject at high flow rates.
Catheter flow rates are dependent on many things. These are the viscosity of your contrast, temperature of the contrast, the size and length of your injector tubing, and whether or not you have endholes or sideholes on your catheter. Contrast that is less viscose is easier to inject. Warming the contrast will lower the viscosity. If you have a long wide injector tubing, you will have a lower flow rate. Smaller and shorter tubing gives you a higher flow rate. By having more sideholes on your catheter, you will increase the amount of contrast being delivered. With endhole catheters the contrast is going to come out in a stream, and you need to have a lower flow rate to prevent damage to the vessel.
Besides coming in different types of shapes and materials, catheters also come in many sizes. Catheters are measured in French (FR) size. One French (FR) is equal to .33 mm. An easier way to remember how to figure French size is 3FR is equal to 1mm. The more common size is 4 or 5FR, but at times larger or smaller sizes are used. Since catheters come in many shapes, one of the easier ways to remember them is by seeing them. See catheter diagrams for catheter shapes and the most common use.
For pulmonary angiograms it is helpful to use the Van Aman. The 90-degree angle helps pass through the tricuspid valve. With difficult vessels the Kumpe catheter gives you more directional control of the guidewire. With the cardiac catheters, the Sones catheter is used when you have to go in the brachial artery. The Judkins and Amplatz catheters are used for selective catheterization of the coronary arteries with a femoral approach.
A guidewire is a metal wire that you use to insert the catheter into the blood vessel. Just like catheters, there are many types of guidewires. A solid guidewire is just a solid wire, usually stainless steel. A wrapped guidewire has a solid stainless steel core wrapped with more stainless steel around it. Wires may also be fixed or movable core. With movable core, the inner core of the wire moves. To move the inner core you have a handle, called the mandril.
Guidewires can also be coated or non-coated. The coating can be heparin or Teflon, which makes the wire slippery and prevents blood from clotting on the wire. Just like with catheters, guidewires have torque. Torque is the ability of the wire to twist and turn with the catheter. You generally want to use a wire that has good torque control. Moveable core wires generally have good torque, which can be changed by extending the mandril. We don't find many different shaped guidewires. Most of the guidewires used are straight tipped with different amounts of floppiness at the tip. You can also take a straight wire and put an angle on it. There are guidewires that already have a curve on them. The J tipped wire is one example and used mainly to get into the artery.
The tip on the J tipped wire is measured by radius. Straight wires are measured by the length of the tip. For example, a 3mm J has a 3mm-radius tip. Another example is a superstiff with 10cm flexible tip, which is a very stiff wire with 10cm of floppy at the end. Wires also come in many lengths and diameters. The length and diameter of your wire is chosen by which catheter you use. The wire needs to fit through the center of the catheter. If you are using a 5FR catheter, most of them will take a .035 or .038 wire (the measurements are in inches).
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To access the artery
you would use the Seldinger technique. First, feel for a strong pulse and
numb the area. Make a small incision about 2mm wide, 1 to 2 cm below where
you feel the pulse. Relocate the pulse and direct your needle. Bevel up into
the artery, puncturing both walls. Remove the stylet and pull back on the
needle until you get blood return. Insert your wire, pull the needle out of
the artery and wipe the blood from the wire. You can then put the catheter in
over the wire.
Some of the types of needles available are single wall, double wall, Chiba, micropuncture, and Colapinto. A single wall needle is also called thin wall. It does not have a stylet. When puncturing with this needle, pull back until you get blood return. The double wall needle is the most commonly used. Both the single wall and double wall needles are usually 18 gauge. Needles are measured in gauges (g), the higher the number the smaller the inner diameter of the needle. |
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1. Locate Pulse, numb skin, and make a small skin nick. 2. Position needle 45 degree angle, bevel up, 1 to 2 cm below where you feel the pulse. 3. Puncture both walls of the artery. |
4. Remove inner stylet. 5. Pull needle back until you get blood return. |
6. Insert wire, making sure that it moves easily in the blood vessel. |
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| Chiba needles are used for biopsies and non-vascular access (i.e. percutaneous nephrostomy). These needles may also have a scored tip to make them more visible with ultrasound. When you have patients with high bleeding times, you can use a Micropuncture needle. These needles are generally 21g and found in a kit with a .018 guidewire and a dilator. Colapinto needles are used to perform Transjugular Intrahepatic Portal Systemic Shunts. |  |
| Courtesy of Cook Inc. |
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| Courtesy of Boston Scientific Vascular |
| For percutaneous drainage (nephrostomy, biliary or abscesses), there are drainage catheters. The drainage catheters are available in a pigtail catheter. However, it is much shorter than an arterial pigtail catheter and it locks in place. This is one of the more commonly used catheters for percutaneous drainage. The locking pigtail makes this catheter ideal because the locking device holds it in place. Sometimes the area that you are putting the drainage catheter into is too small for a pigtail to form so there are other shapes available. Straight and J shaped drainage catheters are examples that you can use in place of the pigtail. Since the catheters don. t lock, they need to be fastened in place. They are usually fastened by suturing the catheter to the skin. |
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| Courtesy of Boston Scientific Vascular |
| With nephrostomy tube placement, there are times that you want to leave the catheter in the bladder. Catheters that are made to be left in the bladder are nephroureteral or double J stent. The nephroureteral stent is used when you want to maintain access to the kidney. The catheter exits the skin and there is a pigtail loop in the kidney to lock it in place. The nephroureteral stent also has another pigtail loop in the bladder. Double J stents are used when you want to keep everything internal. One end loops in the kidney and the other in the bladder. |
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Since we can put catheters and wires into the patient, we also need to know how to retrieve things out of them. Baskets and snares are used for retrieval. Often, when performing a percutaneous nephrostomy, the patient has a stone. We can sometimes retrieve this stone using a stone basket. The stone gets trapped in the basket. Once the stone is trapped, pull the stone and basket out. Snares are used to grab things. This would be done by either grabbing it with forceps or looping around it with a snare. |
| Courtesy of Boston Scientific Vascular |
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| Courtesy of Boston Scientific Vascular |
| Sometimes patients have things that can't be retrieved, like blood clots. In that case we may need to implant a device to stop the clots from entering the heart. We can implant a filter. There are several different kinds of filters, and each institution will use different types. Some may have a large variety and others may only use one or two different kinds. A couple of the more popular filters are Greenfield and Bird. s Nest. Greenfield Filters are on a 12Fr Introducer and are made of Titanium. Bird's Nest Filters are used in large Vena Cava's and are made of stainless steel. | |
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| Courtesy of Cook Inc. | Courtesy of B. Braun |
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| Courtesy of Boston Scientific Vascular |
| Since we can look at blood vessels, we also need to be able to fix them. One device that is used to fix blood vessels is a balloon catheter. The balloon is inserted into the blood vessel similar to a regular catheter and positioned at the stenotic site. Once in position, the balloon is inflated and the plaque cracks, expanding the walls of the blood vessel in the area of angioplasty. Balloon catheters are measured in atmospheres (ATM). They can have either high or low pressure. Low-pressure balloons are usually the larger balloons, i.e. 20mm. High pressure balloons would be balloons made of stronger material to withstand the higher pressure. They would usually be used for very tight lesions. There are many different types of balloons made by various manufacturers. Most balloons work fine for a regular balloon angioplasty, but sometimes you need one made from a stronger material. The stronger material is usually necessary if you are going to put in a stent because the ends of the stent can puncture the balloon. |
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A metallic stent is used to help blood vessels stay open when they fail balloon angioplasty. There are basically two types on the market, self-expanding and balloon expanding. The self-expanding stents come on some type of an introducer. To release the stent, you pull back on the introducer. Some examples of self-expanding stents are Wallstent, Symphony, and Memotherm. Each year there are more stents released on the market. All brands of stents might not be mentioned. The ones that are mentioned have been on the market for at least a couple of years. |  |
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| Courtesy of Boston Scientific Vascular | Courtesy of IntraTherauptics | ||
| Balloon expanding stents must be deployed on a balloon. They can be purchased already on a balloon catheter, or you can put them on a balloon catheter of your choice. Crimping the stent down on the balloon in between the marker beads does this. Some balloon expanding stents are the Palmaz and the Z Stent. |  |
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| Courtesy of Boston Scientific Vascular | Courtesy of Cook Inc. |
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Since veins are also blood vessels, we need to know how to access them. In Interventional Radiology, we are asked to place several types of vascular access devices. One of the most frequently requested is the peripherally inserted catheter (PIC). This is basically a fancy IV and is placed under fluoro guidance. A vein in the upper arm is accessed, the catheter is placed into the vein on a wire, and the tip is left in or near the RA. |
| Courtesy of Cook Inc. |
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If you do cardiac work in your lab, you might
be placing Swan Ganz catheters. This is a flow directed catheter with a
balloon on the tip. The Swan Ganz is used to measure pressures, draw blood
samples, and to measure cardiac output. The opening at the end of the
catheter (distal lumen) is placed in the pulmonary artery. This lumen is used
to measure PA diastolic and systolic pressures. The second lumen is the end
with the balloon. The balloon allows the catheter to be wedged in a branch of
the pulmonary artery. When the catheter is wedged, the distal lumen records
pulmonary capillary wedge pressure. The third lumen (proximal lumen) sits in
the right atrium and is used to measure right atrial pressure.
For long-term access, you might be asked to place a porta catheter. These are implanted under the patient. s skin, either in the upper arm or chest. A porta catheter would be placed for a patient receiving chemotherapy or some other type of infusion that requires accessing the port about once a month. The port is placed in a pocket under the patient's skin. The port is attached to a catheter in the patient's vein and the catheter ends at the RA (right atrium). A Hickman catheter is another type of long-term catheter. A Hickman can be placed in the subclavian or jugular vein. These are usually placed in patients receiving bone marrow transplants, chemotherapy, or needing renal dialysis access. This type of catheter would be used when frequent access is needed. |
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| Courtesy of Cook Inc. | |
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Embolization material would be used if you want to block off flow to a blood vessel or tumor. There are many types of materials out for this purpose: coils, PVA, glue, and gelfoam. Coils are small wires with polyester fibers on them. Coils come in many shapes and sizes, and they can be straight or curled. Ivalon, or PVA, are particles of Polyvinyl Alcohol Foam that would be mixed with a little contrast and injected into the blood vessel. The foam expands due to contact with the blood and would then slow blood flow. Glue can also be used to block blood flow, but care must be taken not to glue the tip of the catheter into the artery. A temporary Embolization material is gelfoam. Gelfoam is usually cut into small pieces and mixed with contrast. It is then injected into the artery and the foam expands. |  |
| Courtesy of Boston Scientific Vascular | ||
| Courtesy of Cook Inc. |
If you are working in a lab that does cardiac cath, you may need to implant pacemakers and defibrillators. Pacemakers are placed to correct problems with heart rhythms that are too slow. An incision is made in the patient's chest and the pacemaker lead is placed in the Subclavian vein. One wire is placed in the right atrium (RA) and one in the right ventricle. The pacemaker is placed under the patient's skin in a small pocket.
Defibrillators are placed when a patient has rhythms that are too fast, i.e. ventricular fibrillation. The defibrillator is placed similar to the pacemaker. A lead wire is placed in the patient's right ventricle and another lead in the Superior Vena Cava with a subcutaneous patch. Another option is a lead in the right ventricle, coronary sinus and Superior Vena Cava. The device that provides the current is placed in a pocket under the patient's skin in the abdomen. You may hear this device referred to as an implantable cardioverter defibrillator (ICD).
The pacemakers and defibrillators are programmed to "kick in" when they sense that the heart rhythm is out of the boundaries. With the pacemaker, if the heart rate gets too slow it begins pacing the heart. With the defibrillator, when the patient goes into ventricular fibrillation a sequence of shocks is delivered. There will usually be from one to four shocks. It takes about 20 seconds for the device to charge after sensing a lethal rhythm. The fist shock is 25 joules (J). If this is not effective, then up to three more shocks (increasing each time up to a total of 30 J) may be given. It will then wait approximately 35 seconds with a non-fibrillating rhythm before delivering any more shocks.
©Copyright 2000 Leona Benson
