Radiation Protection for Angiography Procedure.
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Fluoroscopic procedure produces the greatest patient radiation exposure rate in diagnostic radiology. Therefore the radiation protection in fluoroscopy is very important. Several feature and techniques in fluoroscopy are designed for protection to the patient during fluoroscopic procedure.
a) Protection to Patient
* A dead-man switch is a device (switch) constructed so that a circuit closing contact can only be maintained by continuous pressure on the switch by the operator. Therefore, when the machine is turned on by any means, whether by the push button at the control panel, or by the foot pedal, this switch must be held in for the machine to remain 'on'.
* The 'on-time' of the fluoroscopic tube must be controlled by a timing device, and must end ... alarm when the exposure exceeds 5 minutes. An audible signal must alert the user to the completion of the preset on time. This signal will remain on until the timing device is reset.
* The X-ray tube used for fluoroscopic must not produce X-rays unless a barrier is in position to intercept the entire cross-section of the useful beam. The fluoroscopic imaging assembly must be provided with shielding sufficient that the scatter radiation from the useful beam is minimized.
* Protective barriers of at least 0.25 mm lead equivalency must be used to attenuate scatter radiation above the tabletop. This shielding does not replace the lead garments worn by personnel. Scattered radiation under the table must be attenuated by at least 0.25 mm lead equivalency shielding.
* Additionally, most c-arm fluoroscopes have a warning beeper or light that activate when the beam is on, some have both. Never inactivate any warning devices, and keep one's foot off the foot pedal whenever possible.
* Methods of limiting radiation exposure include:
o making certain that the fluoroscopy unit is functioning properly through routine maintenance,
o limiting fluoroscopic exposure time,
o reducing fields of exposure through collimation,
o keeping the X-ray source under the table by avoiding cross-table lateral visualization when possible, and
o bringing the image intensifier down close to the patient
b) Protection to personnel
There are therefore three basic ways to minimize dose:
* Reduce time of exposure
* Use the inverse square law-doubling your distance away quarter your exposure
* Use shielding by barrier
These basics known as Cardinal Principle which is important to achieved ALARA.
Radiation dose is directly proportional to the time, those by doubling the radiation time the dose is doubled and by having the radiation time the doses halved. Many factors impact the 'on time' of a fluoroscopic procedure.
The exposure time is related to radiation exposure and exposure rate (exposure per unit time) as follows:
Exposure time = Exposure/Exposure rate
Exposure = Exposure rate x time
The algebraic expressions simply imply that if the exposure time is kept short, then the resulting dose to the individual is small.
Method of reducing exposure time include meticulous advanced planning of the procedure, judicious use of contrast enhancement, appropriate positioning of the patient, orientation of the fluoroscope unit prior to beginning the procedure.
The second radiation protection action relates to the distance between the source of radiation and the exposed individual. The exposure to the individual decreases inversely as the square of the distance. This is known as the inverse square law, which is stated mathematically as:
where I is the intensity of radiation and d is the distance between the radiation source and the exposed individual. For example, when the distance is doubled the exposure is reduced by a factor of four.
In mobile radiography, where there is no fixed protective control booth, the technologist should remain at least 2 m from the patient, the x-ray tube, and the primary beam during the exposure. In this respect, the ICRP (1982), as well as the NCRP (1989a), recommended that the length of the exposure cord on mobile radiographic units be at least 2 m long.
Another important consideration with respect to distance relates to the source-to-image receptor distance (SID). The appropriate SIDs for various examinations must always be maintained because an incorrect SID could mean a second exposure to the patient. Long SID results in less divergent beam and thus decreases the concentration of photons in the patients. Short SID results in the reverse action and increases the patient dose. Hence the longest possible SID should be employed in examinations. However, if a greater than standard SID is used then greater intensity of radiation would be required to produce the same film density. Therefore it is recommended that only standard SIDs should be used.
Shielding procedure the most utilitarian results in the reduction of staff dose as there are times when the procedure list simply must function in close proximity, even directly cines fluoroscopy. In these circumstances there simply is no substitute for the best modern flexible lead gloves, lead glasses, lightweight lead apron and lead lined thyroid shield available. Appropriate shielding is mandatory for the safe use of ionizing radiation for medical imaging. Other method of shielding includes beam collimation, protective drapes and panels.
Shielding of occupational workers can be achieved by following methods:
* Personnel should remain in the radiation environment only when necessary (step behind the control booth, or leave the room when practical)
* The distance between the personnel and the patient should be maximized when practical as the intensity of radiation decreases as the square of distance (inverse square law).
* Shielding apparel should be used as and when necessary which comprise of lead aprons, eye glasses with side shields, hand gloves and thyroid shields.
Lead aprons are shielding apparel recommended for use by radiation workers. These are classified as a secondary barrier to the effects of ionizing radiation. These aprons protect an individual only from secondary (scattered) radiation, not the primary beam.
The thickness of lead in the protective apparel determines the protection it provides. It is known that 0.25 mm lead thickness attenuates 66% of the beam at 75kVp and 1mm attenuates 99% of the beam at same kVp.
It is recommended that for general purpose radiography the minimum thickness of lead equivalent in the protective apparel should be 0.5mm. It is recommended that women radiation workers should wear a customized lead apron that reaches below mid thigh level and wraps completely around the pelvis. This would eliminate an accidental exposure to a concept us.
Other protective apparel included eye glasses with side shields, thyroid shields and hand gloves. The minimum protective lead equivalents in hand gloves and thyroid shields should be 0.5mm.
Lead lined glass and thyroid shield likewise reduce 90% of the exposure to the eyes and thyroid respectively. Lead lined gloves reduce radiation exposure to the hands; however they are no substitute for strict observation of appropriate fluoroscopic hygiene. Gloves should be considered as an effective means of reducing scatter radiation only.
2. State five clinical indications for the patient undergo the angiography procedure.
3. Explain the patient care management before, during and after the procedure
Before a procedure:
* Patients undergoing an angiogram are advised to stop eating and drinking eight hours prior to the procedure.
* They must remove all jewelry before the procedure and change into a hospital gown.
* If the arterial puncture is to be made in the armpit or groin area, shaving may be required.
* A sedative may be administered to relax the patient for the procedure.
* An IV line will also be inserted into a vein in the patient's arm before the procedure begins in case medication or blood products are required during the angiogram.
* Be aware of and follow all Local Rules and protocols
* Prior to the angiography procedure, patients will be briefed on the details of the test, the benefits and risks, and the possible complications involved, and asked to sign an informed consent form.
* Ensure that all exposures are justified and there is informed consent
* Check patient identity
* Position patient comfortably flat, with arm above head where possible
* Ensure all members of staff in room are wearing suitable. For operations this should be lead glasses, thyroid collar and wrap-around lead apron
* Check all staff are wearing radiation monitors correctly
* Use all available lead shielding appropriately sited
* Position table before screening
* Keep tube current as low as possible and kVp as high as possible for cardiac studies, 60 – 90 kV is appropriate
* Keep x ray tube at maximum and image intensifier / receptor at minimum distance from patient
* Check all staff are as far away as possible in their role
* Use dose reduction programmers when possible
* Perform acquisitions on full inspiration where possible
* Collimate closely to area of interest
* Prolonged procedures: reduce dose to the irradiated skin eg. Change beam angulations
* Minimize fluoroscopy time, high dose rate time and no of acquisitions
* Remember software features, such as replay fluoro to minimize dose
* Don't over use geometric magnification
* Remove grid for small patients or when image intensifier / detector cannot be placed close to patient
* Check and record screening time and DAP at the end of the case and review against the DRL.
During the procedure:
* The radiologic technologist will position you on the exam table. A radiologist a physician who specializes in the diagnostic interpretation of medical images will administer a local anesthetic and then make a small nick in your skin so that a thin catheter can be inserted into an artery or vein. The catheter is a flexible, hollow tube about the size of a strand of spaghetti. It usually is inserted into an artery in your groin, although in some cases your arm or another site will be selected for the catheter.
* The radiologist will ease the catheter into the artery or vein and gently guide it to the area under investigation. The radiologist will be able to watch the movement of the catheter on a fluoroscope, which is an x-ray unit combined with a television monitor.
* When the catheter reaches the area under study, the contrast agent will be injected through the catheter. By watching the fluoroscope screen, the radiologist will be able to see the outline of your blood vessels and identify any blockages or other irregularities.
* Angiography procedures can range in time from less than an hour to three hours or more. It is important that you relax and remain as still as possible during the examination. The radiologic technologist and radiologist will stay in the room with you throughout the procedure. If you experience any difficulty, let them know.
* Angiography also can be performed using magnetic resonance instead of x-rays to produce images of the blood vessels; this procedure is known as magnetic resonance angiography (MRA) or magnetic resonance venography (MRV).
After the procedure:
* Because life-threatening internal bleeding is a possible complication of an arterial puncture, an overnight stay in the hospital is sometimes recommended following an angiography procedure, particularly with cerebral and coronary angiograms.
* If the procedure is performed on an outpatient basis, the patient is typically kept under close observation for a period of at six to 12 hours before being released.
* If the arterial puncture was performed in the femoral artery, the patient will be instructed to keep his leg straight and relatively immobile during the observation period.
* The patient's blood pressure and vital signs will be monitored and the puncture site observed closely. Pain medication may be prescribed if the patient is experiencing discomfort from the puncture, and a cold pack is applied to the site to reduce swelling. It is normal for the puncture site to be sore and bruised for several weeks.
* The patient may also develop a hematoma, a hard mass created by the blood vessels broken during the procedure. Hematomas should be watched carefully, as they may indicate continued bleeding of the arterial puncture site.
* Angiography patients are also advised to enjoy two to three days of rest and relaxation after the procedure in order to avoid placing any undue stress on the arterial puncture. Patients who experience continued bleeding or abnormal swelling of the puncture site, sudden dizziness, or chest pains in the days following an angiography procedure should seek medical attention immediately.
* Patients undergoing a fluorescein angiography should not drive or expose their eyes to direct sunlight for 12 hours following the procedure.
4. Identify the type of contrast medium, the dose and delivering technique in angiography procedure.
* Reducing radiation doses to the patient also generally reduces doses to the medical personnel.
· Angiography procedure is using fluoroscopy imaging technique which is a real-time imaging technique.
5. List down the catheters and guide wires inclusive of size, shape and the 'hole' type that are used in angiography procedures.
The use of lead gloves during procedures is unusual as they are cumbersome and difficult to work in. The automatic brightness control will increase the exposure to go through two layers and one only protects the hand, so if they are going to be used a programme that sets the radiation factors rather than allowing adjustment may be appropriate. In practice, with careful collimation and attenuation to detail it should not necessary for the operator's hand to be in the primary beam and only close to it for short periods.
While doing catheterization, radiologist should do it behind the lead glass viewer which consists of lead equivalent glass of 0.25mm thickness. Geometric consideration is one of the important things in angiography because source of exposure to personnel is mainly from scattered radiation from the patient. So, it is important to minimize the amount of scattered radiation to personnel. This can be achieved by geometric consideration involving the x-ray tube, patient and image intensifier. The image intensifier should be as close as possible to patient to minimize the amount of scattered radiation hitting personnel.
Because in angiography room is sterile for all things, personnel such as radiologist, nurses, radiographer or student should wear shoes which are prepared only. Make sure that film badges always outside personnel body to measure the dose receive to the personnel.
The most important thing to remember is that all individuals should be fully trained and learned to be responsible for radiation safety. Involvement of a radiation expert is essential and is particularly useful in equipment specification, assessment and quality assurance, but also in the formulation of Local Rules.
Technique Reduces Physician Radiation Exposure During Angiography
Current technique requires that physicians performing radiation procedures wear lead gowns. The new technique involves use of a body length floor mounted lead plastic panel to protect to physicians as they monitor patients' angiograms and control exam table movement. An extension bar allows the physician to remain safely behind the shield and still retain table control for panning.
In the study, researchers recorded radiation exposure to various parts of a physician's body during 25 coronary angiography procedures and compared those results with radiation exposure during angiography on 25 patients using conventional radiation protection. A lead apron, thyroid shield, eyeglasses and facemask were used in both techniques, but a ceiling mounted shield was used in the conventional technique. The researchers placed radiation badges outside and inside the facemask; outside and inside the thyroid shield; on the right and left arm; outside and inside the lead apron; and on the right and left leg.
The new equipment resulted in a 90 percent reduction in radiation exposure to the physician's head, arms, and legs. Exposure of the thyroid and torso was minimal with both techniques.
"Enhanced physician radiation protection during coronary angiography is readily achievable with this new technique," said Martin Magram, M.D., of the University of Maryland Medical Center in Baltimore, Md. Dr. Magram presented the study results on May 3 at the American Roentgen Ray Society Annual Meeting in Vancouver, British Columbia.
Dr. Magram pointed out that by freeing physicians from the need to wear lead gowns, the new technique could preserve their ability to benefit patients.
"It may extend by years their ability to apply the skills they have developed over long careers of serving patients," noted Dr. Magram.
"New methods of radiation protection must parallel the development of new radiation techniques," added Dr. Magram. "The key is to limit medical workers' radiation exposure with effective and easy-to-use techniques, and the use of this extension bar and lead plastic shield may be such a technique."
Angiography is the x-ray study of the blood vessels. An angiogram uses a radiopaque substance, or dye, to make the blood vessels visible under x ray. Arteriography is a type of angiography that involves the study of the arteries.
Angiography is used to detect abnormalities or blockages in the blood vessels (called occlusions) throughout the circulatory system and in some organs. The procedure is commonly used to identify atherosclerosis; to diagnose heart disease; to evaluate kidney function and detect kidney cysts or tumors; to detect an aneurysm (an abnormal bulge of an artery that can rupture leading to hemorrhage), tumor, blood clot, or arteriovenous malformations (abnormals tangles of arteries and veins) in the brain; and to diagnose problems with the retina of the eye. It is also used to give surgeons an accurate "map" of the heart prior to open-heart surgery, or of the brain prior to neurosurgery.
Patients with kidney disease or injury may suffer further kidney damage from the contrast mediums used for angiography. Patients who have blood clotting problems, have a known allergy to contrast mediums, or are allergic to iodine, a component of some contrast mediums, may also not be suitable candidates for an angiography procedure. Because x rays carry risks of ionizing radiation exposure to the fetus, pregnant women are also advised to avoid this procedure.
Angiography is usually performed at a hospital by a trained radiologist and assisting technician or nurse. It takes place in an x-ray or fluoroscopy suite, and for most types of angiograms, the patient's vital signs will be monitored throughout the procedure.
Angiography requires the injection of a contrast dye that makes the blood vessels visible to x ray. The dye is injected through a procedure known as arterial puncture. The puncture is usually made in the groin area, armpit, inside elbow, or neck. The site is cleaned with an antiseptic agent and injected with a local anesthetic. First, a small incision is made in the skin to help the needle pass. A needle containing an inner wire called a stylet is inserted through the skin into the artery. When the radiologist has punctured the artery with the needle, the stylet is removed and replaced with another long wire called a guide wire. It is normal for blood to spout out of the needle before the guide wire is inserted.
The guide wire is fed through the outer needle into the artery and to the area that requires angiographic study. A fluoroscopic screen that displays a view of the patient's vascular system is used to pilot the wire to the correct location. Once it is in position, the needle is removed and a catheter is slid over the length of the guide wire until it to reaches the area of study. The guide wire is removed and the catheter is left in place in preparation for the injection of the contrast medium, or dye.
Depending on the type of angiography procedure being performed, the contrast medium is either injected by hand with a syringe or is mechanically injected with an automatic injector connected to the catheter. An automatic injector is used frequently because it is able to propel a large volume of dye very quickly to the angiogram site. The patient is warned that the injection will start, and instructed to remain very still. The injection causes some mild to moderate discomfort. Possible side effects or reactions include headache, dizziness, irregular heartbeat, nausea, warmth, burning sensation, and chest pain, but they usually last only momentarily. To view the area of study from different angles or perspectives, the patient may be asked to change positions several times, and subsequent dye injections may be administered. During any injection, the patient or the camera may move.
Throughout the dye injection procedure, x-ray pictures and/or fluoroscopic pictures (or moving x rays) will be taken. Because of the high pressure of arterial blood flow, the dye will dissipate through the patient's system quickly, so pictures must be taken in rapid succession. An automatic film changer is used because the manual changing of x-ray plates can eat up valuable time.
Once the x rays are complete, the catheter is slowly and carefully removed from the patient. Pressure is applied to the site with a sandbag or other weight for 10-20 minutes in order for clotting to take place and the arterial puncture to reseal itself. A pressure bandage is then applied.
Most angiograms follow the general procedures outlined above, but vary slightly depending on the area of the vascular system being studied. A variety of common angiography procedures are outlined below:
Cerebral angiography is used to detect aneurysms, blood clots, and other vascular irregularities in the brain. The catheter is inserted into the femoral or carotid artery and the injected contrast medium travels through the blood vessels on the brain. Patients frequently experience headache, warmth, or a burning sensation in the head or neck during the injection portion of the procedure. A cerebral angiogram takes two to four hours to complete.
Coronary angiography is administered by a cardiologist with training in radiology or, occasionally, by a radiologist. The arterial puncture is typically given in the femoral artery, and the cardiologist uses a guide wire and catheter to perform a contrast injection and x-ray series on the coronary arteries. The catheter may also be placed in the left ventricle to examine the mitral and aortic valves of the heart. If the cardiologist requires a view of the right ventricle of the heart or of the tricuspid or pulmonic valves, the catheter will be inserted through a large vein and guided into the right ventricle. The catheter also serves the purpose of monitoring blood pressures in these different locations inside the heart. The angiogram procedure takes several hours, depending on the complexity of the procedure.
Pulmonary, or lung, angiography is performed to evaluate blood circulation to the lungs. It is also considered the most accurate diagnostic test for detecting a pulmonary embolism. The procedure differs from cerebral and coronary angiograms in that the guide wire and catheter are inserted into a vein instead of an artery, and are guided up through the chambers of the heart and into the pulmonary artery. Throughout the procedure, the patient's vital signs are monitored to ensure that the catheter doesn't cause arrhythmias, or irregular heartbeats. The contrast medium is then injected into the pulmonary artery where it circulates through the lung capillaries. The test typically takes up to 90 minutes.
Patients with chronic renal disease or injury can suffer further damage to their kidneys from the contrast medium used in a kidney angiogram, yet they often require the test to evaluate kidney function. These patients should be well-hydrated with a intravenous saline drip before the procedure, and may benefit from available medications (e.g., dopamine) that help to protect the kidney from further injury due to contrast agents. During a kidney angiogram, the guide wire and catheter are inserted into the femoral artery in the groin area and advanced through the abdominal aorta, the main artery in the abdomen, and into the renal arteries. The procedure will take approximately one hour.
Fluorescein angiography is used to diagnose retinal problems and circulatory disorders. It is typically conducted as an outpatient procedure. The patient's pupils are dilated with eye drops and he rests his chin and forehead against a bracing apparatus to keep it still. Sodium fluorescein dye is then injected with a syringe into a vein in the patient's arm. The dye will travel through the patient's body and into the blood vessels of the eye. The procedure does not require x rays. Instead, a rapid series of close-up photographs of the patient's eyes are taken, one set immediately after the dye is injected, and a second set approximately 20 minutes later once the dye has moved through the patient's vascular system. The entire procedure takes up to one hour.
Celiac and mesenteric angiography
Celiac and mesenteric angiography involves x-ray exploration of the celiac and mesenteric arteries, arterial branches of the abdominal aorta that supply blood to the abdomen and digestive system. The test is commonly used to detect aneurysm, thrombosis, and signs of ischemia in the celiac and mesenteric arteries, and to locate the source of gastrointestinal bleeding. It is also used in the diagnosis of a number of conditions, including portal hypertension, and cirrhosis. The procedure can take up to three hours, depending on the number of blood vessels studied.
A splenoportograph is a variation of an angiogram that involves the injection of contrast medium directly into the spleen to view the splenic and portal veins. It is used to diagnose blockages in the splenic vein and portal vein thrombosis and to assess the strength and location of the vascular system prior to liver transplantation.
Most angiography procedures are typically paid for by major medical insurance. Patients should check with their individual insurance plans to determine their coverage.
Because angiography involves puncturing an artery, internal bleeding or hemorrhage are possible complications of the test. As with any invasive procedure, infection of the puncture site or bloodstream is also a risk, but this is rare.
A stroke or heart attack may be triggered by an angiogram if blood clots or plaque on the inside of the arterial wall are dislodged by the catheter and form a blockage in the blood vessels or artery. The heart may also become irritated by the movement of the catheter through its chambers during pulmonary and coronary angiography procedures, and arrhythmias may develop.
Patients who develop an allergic reaction to the contrast medium used in angiography may experience a variety of symptoms, including swelling, difficulty breathing, heart failure, or a sudden drop in blood pressure. If the patient is aware of the allergy before the test is administered, certain medications can be administered at that time to counteract the reaction.
Angiography involves minor exposure to radiation through the x rays and fluoroscopic guidance used in the procedure. Unless the patient is pregnant, or multiple radiological or fluoroscopic studies are required, the small dose of radiation incurred during a single procedure poses little risk. However, multiple studies requiring fluoroscopic exposure that are conducted in a short time period have been known to cause skin necrosis in some individuals. This risk can be minimized by careful monitoring and documentation of cumulative radiation doses administered to these patients.
The results of an angiogram or arteriogram depend on the artery or organ system being examined. Generally, test results should display a normal and unimpeded flow of blood through the vascular system. Fluorescein angiography should result in no leakage of fluorescein dye through the retinal blood vessels.
Abnormal results of an angiography may display a restricted blood vessel or arterial blood flow (ischemia) or an irregular placement or location of blood vessels. The results of an angiography vary widely by the type of procedure performed, and should be interpreted and explained to the patient by a trained radiologist.
A chronic condition characterized by thickening and hardening of the arteries and the build-up of plaque on the arterial walls. Arteriosclerosis can slow or impair blood circulation.
An artery located in the neck.
A long, thin, flexible tube used in angiography to inject contrast material into the arteries.
A condition characterized by the destruction of healthy liver tissue. A cirrhotic liver is scarred and cannot break down the proteins in the bloodstream. Cirrhosis is associated with portal hypertension.
A blood clot, air bubble, or clot of foreign material that travels and blocks the flow of blood in an artery. When blood supply to a tissue or organ is blocked by an embolism, infarction, or death of the tissue the artery feeds, occurs. Without immediate and appropriate treatment, an embolism can be fatal.
An artery located in the groin area that is the most frequently accessed site for arterial puncture in angiography.
An orange dye used to illuminate the blood vessels of the retina in fluorescein angiography.
A fluorescent screen which displays "moving x-rays" of the body. Fluoroscopy allows the radiologist to visualize the guide wire and catheter he is moving through the patient's artery.
A wire that is inserted into an artery to guides a catheter to a certain location in the body.
A lack of normal blood supply to a organ or body part because of blockages or constriction of the blood vessels.
Cellular or tissue death; skin necrosis may be caused by multiple, consecutive doses of radiation from fluoroscopic or x-ray procedures.
Fatty material that is deposited on the inside of the arterial wall.
A condition caused by cirrhosis of the liver. It is characterized by impaired or reversed blood flow from the portal vein to the liver, an enlarged spleen, and dilated veins in the esophagus and stomach.
Portal vein thrombosis
The development of a blood clot in the vein that brings blood into the liver. Untreated portal vein thrombosis causes portal hypertension.
For Your Information
* Baum, Stanley, and Michael J. Pentecost, eds. Abrams' Angiography. 4th ed. Philadelphia: Lippincott-Raven, 1996.
Source: Gale Encyclopedia of Medicine, Published December, 2002 by the Gale Group
The Essay Author is Paula Anne Ford-Martin.
Most conventional x-ray angiography procedures are similar.
- Patient preparation involves removing clothing and jewelry and wearing a patient gown. In all cases, angiography requires that intravenous contrast is administered. For interventional or therapeutic angiography, a small incision is made in the groin or arm so that a catheter can be inserted during the study.
- The patient is positioned on the examination table by the technologist so that the anatomy of interest (e.g. leg artery) is in the proper field of view between the x-ray tube and image intensifier.
- The technologist and radiologist remain at table-side during the procedure to operate the angiography system and work with the catheters, contrast injectors and related devices. Typically the patient simply needs to relax and stay calm during angiography. Some angiography procedures can take up to two hours while other procedures take less than an hour.
- Once the procedure is finished, the patient will be given a period of time to recover. During this period, the patient's case is reviewed on film or monitor.
- Depending on the type of angiographic procedure and the patient's medical condition, an inpatient recovery may be required or the patient may be released after a short time. In some cases, more images may need to be taken.
A few days before your angiography examination, a number of blood tests will be performed, and you will be asked about the medications you take, whether prescription or over-the-counter. You also will be asked if you have any allergies. It is important to list all allergies to food and medicine, as well as hay fever or asthma. Existing allergies may indicate a possible reaction to the contrast agent that will be used during the examination. If you are a woman of childbearing age, you also will be asked if there is any possibility that you are pregnant, because a fetus is sensitive to radiation. Before you leave, you will receive detailed instructions about how to prepare for your procedure. Follow these instructions carefully.
When you arrive for your angiogram, a radiologic technologist will explain the procedure to you and answer any questions you might have. A radiologic technologist is a skilled medical professional who has received specialized education in the areas of radiation protection, patient care, radiation exposure, radiographic positioning and radiographic procedures.
Before the exam begins, you will be asked to remove all clothing and jewelry and to put on a hospital gown.
During the Examination
Therapeutic Uses of Angiography
In addition to imaging the blood vessels, angiography can be used to help repair them. During a procedure known as balloon angioplasty, angiography is used to guide a balloon through the catheter to a blocked or narrowed area of an artery. The balloon is inflated, compressing plaque against the walls of the artery and widening it. Then the balloon is deflated and the catheter is removed. In cases where the artery cannot be stretched by balloon angioplasty, a surgical stent can be inserted into the vessel to help keep it open. Stents are small, cylindrical supports made of metal.
After the angiography examination is complete, you will be moved to a room where you can rest and recover. Depending upon your overall health and medical condition, you may be released after just a few hours or you may be admitted to the hospital for observation and recovery.
Before you go home, you will be given instructions explaining how to care for the site where the catheter was inserted. Your physician also may recommend that you restrict your activities at home or rest in bed, possibly with your head elevated. Follow the physician's instructions carefully.
Any contrast agent that remains in your system will be excreted by your kidneys. You may be advised to drink lots of water to help flush the contrast from your system. The amount of contrast is very small, and it has no odor or color. You will not notice any discoloration of your urine. In addition, the radiation that you are exposed to during this examination, like the radiation produced during any other x-ray procedure, passes through you immediately.
Your angiograms will be reviewed by the radiologist or a cardiologist, and your personal physician will receive a report of the findings. Your physician then will advise you of the results and discuss what further procedures, if any, are needed.
A. The Catheter
The in-vivo bypass catheterization method comprising the present invention requires that a guiding or introducer catheter be employed as an essential part of the apparatus and manipulations. This controlling or guiding flexible catheter has at least one tubular wall of fixed axial length; has at least one proximal end for entry, has at least one distal end for egress; and has at least one internal lumen of a volume sufficient to allow for on-demand controlled passage therethrough of a prepared obturator carrying a deformable thermoelastic cuff and a bypass conduit.
Catheters, particularly surgical catheters, are conventionally known and used; and a wide range and variety of guiding or introducer catheters are available which are extremely diverse in shape, design, and specific features. All of the essential requirements of a guiding flexible catheter exist as conventional knowledge and information in the relevant technical field; and all of the information regarding catheter design and provided in summary form hereinafter is publicly known, widely disseminated, and published in a variety of authoritative texts. The reader is therefore presumed to be both familiar with and have an in-depth knowledge and understanding of the conventional diagnostic and therapeutic uses of catheters and cathertization techniques. Merely representative of the diversity of publications publicly available are the following, each of which is expressly incorporated by reference herein: Diagnostic and Therapeutic Cardiac Cathertization , second edition (Pepine, Hill, and Lambert, editors) Williams & Wilkins, 1994 and the references cited therein; A Practical Guide To Cardiac Pacing, fourth edition (Moses et. al., editors) Little, Brown, and Company, 1995 and the references cited therein; Abrams Angiography , third edition (H. L. Abrams, editor), Little, Brown, and Company, 1983.
A number of specific types of guiding catheters or introducers are known today; but for purposes of practicing the present invention, a number of newly designed or specifically designed catheters of varying lengths and sizes suitable for bypass use are expected and intended to be developed and manufactured subsequently. Equally important, minor modifications of the presently existing general categories of catheters are equally appropriate and are expected to be found suitable for use when practicing the present invention. Accordingly, a summary review of the conventionally known catheter types as well as a overall description of general catheter design and the principles of catheter construction are presented herein.
Catheter Construction and Design:
Presently known specific types of catheters include the following: central venous catheters which are relatively short (usually 20-60 centimeters) in length and are designed for insertion into the internal jugular or subclavian vein; right heart catheters such as the Cournard catheter designed specifically for right heart catheterization; transseptal catheters developed specifically for crossing from right to left atrium through the interarterial septum at the fossa ovalis; angiographic catheters which are varied in shape and are frequently used today in the femorial and brachial approach for cardiac catheterization and angiography in any of the major vessels; coronary angiographic catheters which include the different series of grouping including Sones, Judkins, Amplatz, multipurpose, and bypass graft catheters; as well as many others developed for specific purposes and medical conditions.
Merely representative of guiding and introducer catheters, generally presented herein without regard to their specific past usages or intended applications, are those illustrated by FIGS. 1 and 2 respectively. As exemplified by FIG. 1 , a catheter 2 is seen having a tubular wall of fixed axial length; having two proximal portals 4 and 6 which together generate the proximal end 8 for entry into the interior of the catheter; a single distal portal 10 and the distal end 12 of the catheter, and an internal lumen 14 (which is not visible in the illustration).
Another variation commonly known is illustrated by FIG. 2 which shows a controlling flexible catheter 20 having a tubular wall of fixed axial length; three proximal portals 21 , 22 and 23 respectively which collectively form the proximal end 24 for entry into the internal volume of the catheter; and a single distal portal 25 which designates the distal end 26 or tip of the catheter. It will be appreciated and understood that FIGS. 1 and 2 are presented merely to show the overall general construction and relationship of parts present in each flexible controlling catheter suitable for use with the present methodology.
In accordance with established principles of conventional catheter construction, the axial length of the catheter may be composed of one or several layers in combination. In most multilayered constructions, one hollow tube is stretched over another to form a bond; and the components of the individual layers determine the overall characteristics for the catheter as a unitary construction. Most multilayered catheters comprise an inner tube of teflon, over which is another layer of nylon, woven Dacron, or stainless steel braiding. A tube of polyethylene or polyurethane is then heated and extruded over the two inner layers to form a bond as the third external layer. Other catheter constructions may consist of a polyurethane inner core, covered by a layer of stainless steel braiding, and a third external jacket layer formed of polyurethane.
Several examples of basic catheter construction and design are illustrated by FIGS. 3-6 respectively. FIGS. 3A and 3B are perspective and cross-sectional views of a single tubular wall considered the standard minimum construction for a catheter. FIGS. 4A and 4B are perspective and cross-sectional views of a thin-walled design for a single layer extruded catheter. In comparison, FIGS. 5A and 5B are perspective and cross-sectional views of a standard multilayered catheter construction having a braided stainless steel midlayer in its construction. Finally, FIGS. 6A and 6B are perspective and cross-sectional views of a thin-walled design for a multilayered catheter with a braided stainless steel middle layer.
Catheters are generally sized by external and internal diameter and length. The internal specified either by diameter (in thousandths of an inch or millimeters or French). Many newer thin-walled catheter designs provide a much larger internal lumen volume to external diameter ratio than has been previously achieved; and this has resulted in catheters which can accommodate much more volume and allow the passage of much larger sized articles through the internal lumen. External diameter is typically expressed in French sizes which are obtained by multiplying the actual diameter of the catheter in millimeters by a factor of 3.0. Conversely, by traditional habit, the size of any catheter in millimeters may be calculated by dividing its French size by a factor of 3.0. French sizes from 5-8 are currently used for diagnostic angiography. For purposes of practicing the present invention, it is also desirable that French sizes ranging from 4-16 respectively be employed unless other specific size requirements are indicated by the particular application or circumstances. In addition, because of the variation between standard, thin-walled, and super high-flow catheter construction designs, a range and variety of external and internal lumen diameter sizes exist. To demonstrate the conventional practice, the data of Table 1 is provided.
A number of different dual-lumen catheters are known today which differ in the size and spatial relationship between their individual lumens. This is illustrated by FIGS. 7A-7D respectively which show different dual-lumen constructions for four catheters having similar or identical overall diameter (French) size.
As shown therein, FIG. 7A shows a dual-lumen catheter 30 wherein a first external tubular wall 32 provides an outer lumen volume 34 into which a second internal tubular wall 36 has been co-axially positioned to provide an inner lumen volume 38 . Clearly, the construction of catheter 30 is a co-axial design of multiple tubular walls spaced apart and co-axially spaced but separate internal lumens of differing individual volumes.
In comparison, FIG. 7B shows a second kind of construction and design by dual-lumen catheter 40 having a single external tubular wall 42 ; and an centrally disposed inner septum 44 which divides the interior tubular space into two approximately equally lumen volumes 46 and 48 respectively. Thus, in this construction, the diameter, length, and volume of internal lumen 46 is effectively identical to the diameter, length and volume of internal lumen 40 ; and both of these exist and are contained within a single, commonly-shared, tubular wall.
A third kind of construction is illustrated by FIG. 7 C and shows an alternative kind of construction and design. As seen in FIG. 7C , dual-lumen catheter 50 has a single external tubular wall 52 ; and contains an asymmetrically positioned internal divider 54 which divides the interior tubular space into two unequal and different lumen volumes 56 and 58 respectively. Thus, in this alternative construction, the discrete volume of internal lumen 56 is markedly smaller than the volume of the adjacently positioned internal lumen 58 ; and yet both of these internal lumens 56 and 58 exist in, are adjacently positioned, and are both contained within a commonly-shared single tubular wall.
A fourth construction and design for a dual-lumen catheter is presented by FIG. 7D which shows a catheter 60 having a single external tubular wall 62 of relatively large size and thickness. Within the material substance 68 of the tubular wall 60 are two discrete bore holes 64 and 66 of differing diameters which serve as two internal lumens of unequal volume. Internal lumen 64 is clearly the smaller while internal lumen 66 is far greater in spatial volume. Yet each internal lumen volume 64 and 66 is adjacent to the other, lies in parallel, and follows the other over the axial length of the catheter.
Introducer Catheters and Catheter Ends:
In general, an introducer catheter is straight or linear over its axial length and does not have any bends or curves towards the distal end or at the distal tip. A representative illustration of the distal end and tip of an introducer catheter is shown by FIG. 8 .
As seen in FIG. 8 , an introducer catheter 80 has an elongated tubular body 82 formed by a cylindrical-shaped sidewall 84 and provides a hollow internal lumen 86 which extends over its linear axial length. The catheter distal end 88 terminates as a single tip 90 having one central distal portal 92 to the lumen 86 . Similarly, the catheter proximal end 94 terminates as an enlarged proximal tip 96 and has one central proximal portal 98 to access the internal lumen 86 . Conventional practice also permits a number of different distal ends or tips which vary in design and appearance to be used with any given style or type of catheter. Merely representative of these permitted and conventional variances in distal end design for catheters generally are the distal ends of some ventricular catheters which can include a "pigtail" design and construction which has a curled-tip format and multiple side holes; the Lehman ventricular catheter end which provides a number of side holes in different places along the distal end; and the Gensini design which provides multiple side holes at varying angles. Accordingly, for purposes of practicing the present invention, any construction of the catheter distal end whether having one or more curves, or none; and whether or not there is more than one central portal for exiting the lumen or multiple side holes, are all considered conventional variations in catheter tip construction and design. Any and all of these distal tip designs and constructions are therefore deemed to be encompassed completely and to lie within the general catheter scope of construction suitable for use with the present invention.
B. The Obturator
The second requisite component part of the catheter apparatus is the obturator. Each embodiment of an obturator is comprised of at least three parts, and preferably comprises four component parts. The minimal requisite three elements include a puncturing headpiece; a perforating end tip on the headpiece; an elongated shaft integral with the puncturing headpiece. The fourth highly desirable component is the means for expanding and contracting the size of the puncturing headpiece on-demand. Various embodiments representative of each of these structural components are individually illustrated within FIGS. 9-15 respectively.
One general embodiment of an obturator is illustrated by FIGS. 9-10 . As seen therein, the obturator 120 comprises a puncturing headpiece 122 which is substantially bullet-shaped (frusto-conical) in configuration, and comprises an outer shell 124 and a base plate 126 . The outer shell 124 has determinable surface dimensions and an overall girth which can be either fixed or varied in size. At the distal end 128 of the puncturing headpiece 122 is a perforating end tip 130 which appears as a cross-shaped cutting edge for the headpiece 122 . As shown by FIG. 10 , the perforating end tip 130 does not extend over the entire surface area of the outer shell 124 ; instead, the perforating end tip 130 is limited in size and orientation to the distal end 128 . The perforating end tip 130 serves as the sharp cutting edge for the obturator 120 as a whole.
Integral with the puncturing headpiece 122 is an elongated shaft 134 whose overall axial length may be varied to accommodate the surgeon and the particular medical circumstances of usage. The distal end 136 of the shaft is integrated with the puncturing headpiece 122 and can provide access to the interior volume of the headpiece bounded by the outer shell 124 and the base plate 126 . The proximal end 138 of the elongated shaft 134 is intended to be held by the surgeon performing the vascular bypass surgery. Accordingly, the axial length of the elongated shaft 134 will vary and accommodate the surgeon; and thus vary from a few inches to a few feet in length. The function of the elongated shaft 134 is for the carrying and transport of a bypass conduit to the chosen site on the unobstructed or primary blood vessel in-vivo. The elongated shaft 134 acts to support, maintain and convey the conduit within the lumen of the catheter in a manner such that the conduit can be used as a bypass graft.
The Fixed Size Embodiments of the Obturator
The minimalist format for the obturator does not provide any means nor mechanism to alter the surface dimensions or configuration of the puncturing headpiece integrated with the elongated shaft. Thus, the initial dimensions and girth for the puncturing headpiece 122 shown by FIGS. 9 and 10 respectively will remain constant and fixed; and neither the size, shape, aspect ratios, nor overall geometry will be changed or modified during the intended in-vivo use for the obturator embodiment. The fixed size embodiment, however, is a less preferred format for clinical applications; and this minimalist format may cause more procedural difficulty and inconvenience for the surgeon than the preferred variable-size embodiments of the obturator.
The Variable-size Embodiments of the Obturator
A highly desirable and preferred component feature of the puncturing headpiece and the obturator as a whole is that means exist for expanding and contracting the puncturing headpiece on-demand. The effect of this fourth feature and capability for the obturator is illustrated by FIGS. 11-13 respectively. As seen within FIG. 11 , the puncturing headpiece 122 appears in its initial size identical to that shown by FIGS. 9 and 10 . The outer shell 124 is substantially cone-shaped in configuration, has an initial internal volume, and has a girth dimension d equal to the initial diameter of the base plate 126 . The internal volume of the puncturing headpiece, as determined by the dimensions of the outer shell 124 and the base plate 126 , provides an initial internal volume of determinable quantity.
When the mechanism for contracting the puncturing headpiece is activated, the consequence is illustrated by FIG. 12 in which the dimensions of the outer shell 124 have been diminished and the girth of the headpiece has been reduced as shown by the reduced diameter d′ of the base plate 126 . Note also, that as the puncturing headpiece 122 becomes contracted in overall volume and dimensions, the configuration of the puncturing headpiece 122 has consequentially become altered and now appears to be spear-like in configuration. Similarly, the overall angular disposition of the perforating end tip 130 serving as the cutting edge will also be slightly altered in overall appearance as a consequence of contracting the puncturing headpiece 122 .
Alternatively, when the puncturing headpiece 122 is expanded, the overall result is shown by FIG. 13 . As seen therein, the outer shell 124 has been expanded in overall dimensions and volume; and the girth of the headpiece has been expanded and can be determined by the diameter d″ of the expanded base plate 126 . Note that the overall appearance of the puncturing headpiece has been altered as a consequence of its expansion and now appears to be elliptical in shape overall. Similarly, the perforating end tip 130 has similarly been altered in appearance and has angularly expanded somewhat to conform with the expanded dimensions and angularity of the outer shell 124 .
It will be recognized and appreciated also that throughout the changes in appearance, internal volume (designated as V, V′ and V″) and overall size for the contracted or expanded puncturing headpiece 122 (as shown via FIGS. 11 , 12 , and 13 respectively), the dimensions and overall configuration of the elongated shaft 134 have not been altered meaningfully or significantly. Although this is not an absolute requirement in each and every embodiment of an obturator, it is preferred that the elongated shaft 134 , particularly at the integrated distal end 136 , remain constant in size and volume as much as possible and be unaffected subsequent to the on-demand expansion or contraction of the puncturing headpiece 122 . This preference and feature will maintain the integrity of the synthetic prosthesis or the excised vascular segment intended to be carried and transported by the elongated shaft during the bypass grafting procedure. Thus, to avoid or minimize any physical damage to the graft material, it is desirable that the elongated shaft be maintained in appearance, configuration and dimensions without change whenever possible.
Means for Contracting or Expanding the Puncturing Headpiece
A feature and component of each preferred obturator is the existence and availability of specific means for expanding and contracting the puncturing headpiece on-demand. A number of different mechanisms and means for expanding and contracting the puncturing headpiece of the obturator are conventionally known and easily employed. Merely to demonstrate some different and conventionally known mechanisms, attention is directed to the means illustrated by FIGS. 14 and 15 respectively.
The means for expanding and contracting the puncturing headpiece on-demand illustrated by FIG. 14 constitute a mechanical approach and design mechanism which is carried within the internal volume of the puncturing headpiece 122 and the integrated elongated shaft 134 . As seen therein, a central rod 150 extends through the hollow interior of the elongated shaft 134 and extends into the internal volume defined by the outer shell 124 and the base plate 126 of the puncturing headpiece 122 . Within the internal volume of the outer shell 124 , a plurality of rotable ribs 152 are joined to the central rod 150 at the distal end to form a central pivot point 154 . Each rotable rib 152 is mobile and pivotable around the central point 154 and forms an umbrella-like scaffolding structure which can be expanded outwardly or collapsed inwardly at will. Mounted on the central rod 150 is an expansion wheel 156 . This expansion wheel 156 is centrally mounted on the rod 150 ; is moveable over the axial length of the central rod 150 ; and is controlled in the direction of axial movement (distally and proximally). The expansion wheel 156 comprises a center hub 158 and a plurality of hub supports 160 , both of which maintain the expansion wheel in proper position as it engages the plurality of rotable ribs 152 . Joined to the central hub 158 of the expansion wheel 156 are linear movement members 162 which are positioned within the interior volume of the elongated shaft 134 and have a length sufficient to reach to the proximal end 138 of the elongated shaft 134 for control by the surgeon or invasive radiologist. The linear movement members 162 engage the center hub 158 of the expansion wheel 156 ; and extend or withdraw the expansion wheel closer to or away from the perforating end tip 130 of the puncturing headpiece 122 . When the expansion wheel is engaged and pushed forward, expansion wheel engages the rotable ribs 152 and expands the rotable ribs outwardly thereby increasing the overall girth of the puncturing headpiece as a unit. Alternatively, when the linear movement members 162 are withdrawn, the expansion wheel recedes towards the proximal end and the engaged rotable ribs 152 collapse inwardly within the volume of the outer shell 124 . The consequence of this movement is a contraction of the puncturing headpiece 122 as a unit. It will be recognized and appreciated that this mechanical approach for expanding and contracting the puncturing headpiece is completely conventional in design and operation; and accordingly, any conventional refinement of these basic component parts is considered to be a variation within the scope of this mechanical system.
As a representated alternative, hydraulic means for expanding and contracting the puncturing headpiece of the obturator on demand is also provided. In this system, as shown by FIG. 15 , the internal volume of the puncturing headpiece 122 and the integrated elongated shaft 134 includes an elastic sack 180 comprised of a fluid containing elastic bubble 182 and a fluid delivering elastic conduit 184 . The outer shell 124 and base plate 126 of the puncturing headpiece 122 are as previously shown; and the headpiece 122 is integrated with the elongated shaft 134 as previously described herein. Within the internal volume of the puncturing headpiece 122 , is a fluid containing elastic bubble 182 which is in fluid communication with the elastic conduit 184 carried within the internal volume of the elongated shaft 134 . The elastic sack 180 is formed of elastomeric material (such as rubber, elastic plastic, and the like) and is fluid-tight along its seams. The elastic sack 180 contains any liquid which is compatible with the material of the elastic sack; and it is the intrinsic nature of the material forming the elastic sack 180 that the material exerts a compression force or pressure upon the fluid contained within the elastic sack itself. In this way a hydraulic system for expanding and contracting the puncturing headpiece of the obturator is created.
As fluid is introduced through the elastic conduit 180 by the surgeon or invasive radiologist, that fluid is conveyed and delivered into the elastic bubble 182 positioned within the puncturing headpiece 122 . The elasticity of the bubble 182 exerts a mild compression force and pressure against the quantity of fluid contained within the bubble interior volume; accordingly, the greater the quantity of fluid within the elastic bubble 182 , the larger in overall volume the elastic bubble becomes. Thus, as more fluid is delivered through the conduit 184 into the elastic bubble 182 , the larger in overall volume the elastic bubble becomes; and as the volume of the elastic bubble expands, the overall configuration and internal volume of the piercing headpiece 122 also enlarges. In this manner, by carefully controlling the amount of fluid conveyed through the conduit 184 into the elastic bubble, the overall size and configuration of the piercing headpiece 122 can be controllably expanded. Subsequently, to reduce the overall size and configuration of the puncturing headpiece 122 , a quantity of fluid is permitted to be released from the elastic conduit 184 at the proximal end by the surgeon or radiologist. Because the material is elastic and exerts a compression force against the quantity of fluid present within the bubble at any given moment in time, the release of fluid through the elastic conduit will cause a reduction in overall size for the elastic bubble 182 ; and as the overall volume of the elastic bubble is reduced in size, the puncturing headpiece will consequently be contracted and reduced in configuration and overall volume as well. It will be noted and appreciated also that this hydraulic mechanism for expanding and contracting the puncturing headpiece on demand is a conventionally known fluid system and technique; and many conventionally known variations and changes in hydraulic design and fluid control systems are presently known and commonly available for use. Accordingly, all hydraulic systems are envisioned as suitable for use as one means for expanding and contracting the puncturing headpiece of the obturator on-demand.
Alternative Obturator Structures
A number of different physical embodiments for the obturator are also envisioned and intended for use. Some examples, which are merely illustrative of the range and variety of physical formats and which serve to merely illustrate the range and degree of difference available for the various puncturing headpieces of an obturator, are illustrated by FIGS. 16-22 respectively. It will be recognized and understood, however, that these alternative embodiments are merely representative of obturators and puncturing headpieces generally and do not signify any limitation or restriction on their structural construction or design.
The embodiment illustrated by FIGS. 16 and 17 respectively shows a puncturing headpiece 200 which is substantially cone-shaped in overall appearance and comprises an outer shell 202 and a base plate 206 . The distal end 208 of the puncturing headpiece 200 has a perforating end tip 210 which is also substantially cone-shaped in configuration and appearance and covers only a small surface area of the outer shell 202 . Integral with the puncturing headpiece is the elongated shaft 134 as described previously herein; and means for expanding and contracting the puncturing headpiece 200 on-demand are included within the obturator as a integrated unit.
Another embodiment for the puncturing headpiece is illustrated by FIGS. 18 and 19 respectively. As shown therein, the puncturing headpiece 220 comprises the outer shell 222 and the base plate 224 integral with the elongated shaft 134 . A particular feature of this embodiment, however, is the distal end 226 seen most clearly within FIG. 19 as providing a perforating end tip 230 which is substantially star-shaped and extends over the surface area of the outer shell 222 . The result is to provide a series of grooves 228 alternating with sharp cutting edges 232 over the surface of the outer shell 222 . This embodiment for the puncturing headpiece 220 provides a much greater area for cutting and perforation as a spe
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