Radiation Protection for Angiography Procedure.
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Published: Thu, 01 Mar 2018
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.
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