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Use of radioactive technetium Tc-99m in peripheral arteriography
Use of Radioactive Technetium TcBm
in Peripheral Arteriography
MIITAPALLI MOHAN RAO, MB, BS,* Bridgeport, ROBERT PASMEG, RT, Bridgeport, Connecticut EDWARD KENNELLY, MS, Bridgeport, Connecticut ANTHONY BRAVO, MD, Bridgeport, Connecticut ROBERT BERRY, MD, Bridgeport, Connecticut
The chief concern of the surgeon in evaluating peripheral arteriosclerotic disease of the lower extremity is the status of the vessels below the popliteal, combined with a thorough knowledge of the common and superficial femoral arteries. In studying these vessels, one attempts to visualize the entire vascular bed with as few injections as possible. Because of the great length of the vascular bed in question, conventional filming with moving tables, serial roentgenograms with multiple injections, and extra large field angiography have been developed. In the simplest of these technics, using a 14 by 34 inch cassette, half of the film is exposed immediately after the injection of contrast material into the common femoral artery, and the other half is exposed a variable time afterward to visualize the more distal vascular bed. The timing of the second exposure varies with the rapidity of circulation. Because of this, the appropriate exposure delay must be selected. This can be done by: (1) routine timing delay studies, which sometimes must be repeated if the circulation is unduly rapid or unduly delayed, and (2) the injection of 5 cc test dose of contrast and the rapidity of circulation assessed by the patient’s response to pain in the calf region. This has the disadvantage of causing extra discomfort to the patient and being dependent on a subjective response. We have been evaluating the rapidity of circulation by means of Tc-99 injected into the common femoral artery as an aid in proper radiographic timing, especially considering the runoff of the popliteal and its branches, p?*ior to the injection of the contrast media. From the Departments of Surgery and Radiology. Bridgeport Hospital, Bridgeport. Connecticut. Reprint requests should be addressed to Dr Bravo, Bridgeport Hospital, Bridgeport, Connecticut. l Present address: Division of Thoracic and Cardiovascular Surgery, Jackson Memorial Hospital, Miami, Florida 33125.
408
Connecticut
Technetium-99m, in the form of sodium pertechnetate, has ideal physical characteristics for use as a localizing agent in femoral arteriography. Tc-99m can readily be obtained by elution from a 99 MO “cow.” It has been used widely for various scanning technics and can be obtained commercially in ampules for use without further preparation. Tc-99m is an isomer of Tc-99, emitting two gamma rays (140 and 142 kev) with a physical half-life equal to six hours. Tc-99 emits no beta particles, which only contribute to the radionuelides in medicine. The daughter of Tc-99m (Tc-99) also is radioactive. However, because it has a very long half-life (2.1 x lo5 years ; 1 mc of Tc-99m decays completely to only 3.3 pc of Tc-99), the radiation dose from Tc-99 is negligible. Utilizing a scintillation detector measuring 1 inch in diameter and an analog recorder, the activity needed to localize an artery is approximately 100 ,.Lc,This results in a whole body dose equal to 1.3 mrads. In comparison to routine radiographic and fluoroscopic studies, the whole body dose for a straight chest film would be 0.4 mrads ; a dental whole mouth series would be 46.6 mrads; a gallbladder series would be 15.6 mrads. Therefore, the whole body dose from this procedure is only slightly greater than that from a chest roentgenogram and considerably less than that from many standard radiographic and fluoroscopic procedures. The radiation doses to the parts of the body from this procedure are estimated to be: male gonads, 1.2 mrads; female gonads, 1.6 mrads; gastric mucosa, 10 mrads ; intestinal mucosa, 16 mrads ; thyroid, 2.7 mrads. Again, these doses are well below levels known to cause somatic damage and are in the range accepted in other diagnostic procedures utilizing ionizing radiation.
Technetium
Method The femoral artery is punctured, utilizing a Cournand type of needle. A 100 pc dose of Tc-99 in 10 cc of saline is injected, and the time of circulation from the site of injection to the popliteal region is determined by means of a scintillation probe placed over the knee. The proximal film for the thigh vessels is exposed at the
end of the injection. Exposure of the second film is made to coincide with the previously determined time of probe deflection after the injection of Tc-99. Films are taken on a 36 inch mounted cassette with a 60 inch film distance. Lateral shifting of the cassette, using lead shielding, is used for two different exposures, thus facilitating visualization of the entire leg. The role of the technetium is to help in the proper timing of the film’s exposure, which is dependent on blood flow and therefore directly proportional to the degree of vascular occlusion. In determining the circulation time, we have found that the time should be determined from the initial deflection of the needle and not at the point of maximal deflection.
Tc-99m
in Peripheral
Arteriography
be obtained in almost all cases with a single injection, without shifting the patient, and without a film changer. The patient is saved the added discomfort and morbidity of prolonged procedures and multiple injections. In addition, valuable information concerning the peripheral blood flow is obtained by accurate determination of the circulation time. This technic has been used in an unselected series of sixty patients with clinically suspected occlusive disease of the femoropopliteal arteries. We have encountered no problems that are not those inherent in puncture of a peripheral vessel and injection of contrast medium. The average circulation times (femoral to popliteal) have been eight to nine seconds. More prolonged circulation times would be more likely in the presence of occlusion of the superficial femoral artery without adequate collaterals, implying recent or acute occlusion. Summary
Results
Utilizing Tc-99 for evaluation of circulation time, adequate examination of both the proximal and distal vascular bed in the lower extremity can
Volume
122, September
1971
A simple method of determining peripheral circulation time and timing of exposures of peripheral arteriography is described. The technic and its advantages are briefly discussed.
409
in Peripheral Arteriography
MIITAPALLI MOHAN RAO, MB, BS,* Bridgeport, ROBERT PASMEG, RT, Bridgeport, Connecticut EDWARD KENNELLY, MS, Bridgeport, Connecticut ANTHONY BRAVO, MD, Bridgeport, Connecticut ROBERT BERRY, MD, Bridgeport, Connecticut
The chief concern of the surgeon in evaluating peripheral arteriosclerotic disease of the lower extremity is the status of the vessels below the popliteal, combined with a thorough knowledge of the common and superficial femoral arteries. In studying these vessels, one attempts to visualize the entire vascular bed with as few injections as possible. Because of the great length of the vascular bed in question, conventional filming with moving tables, serial roentgenograms with multiple injections, and extra large field angiography have been developed. In the simplest of these technics, using a 14 by 34 inch cassette, half of the film is exposed immediately after the injection of contrast material into the common femoral artery, and the other half is exposed a variable time afterward to visualize the more distal vascular bed. The timing of the second exposure varies with the rapidity of circulation. Because of this, the appropriate exposure delay must be selected. This can be done by: (1) routine timing delay studies, which sometimes must be repeated if the circulation is unduly rapid or unduly delayed, and (2) the injection of 5 cc test dose of contrast and the rapidity of circulation assessed by the patient’s response to pain in the calf region. This has the disadvantage of causing extra discomfort to the patient and being dependent on a subjective response. We have been evaluating the rapidity of circulation by means of Tc-99 injected into the common femoral artery as an aid in proper radiographic timing, especially considering the runoff of the popliteal and its branches, p?*ior to the injection of the contrast media. From the Departments of Surgery and Radiology. Bridgeport Hospital, Bridgeport. Connecticut. Reprint requests should be addressed to Dr Bravo, Bridgeport Hospital, Bridgeport, Connecticut. l Present address: Division of Thoracic and Cardiovascular Surgery, Jackson Memorial Hospital, Miami, Florida 33125.
408
Connecticut
Technetium-99m, in the form of sodium pertechnetate, has ideal physical characteristics for use as a localizing agent in femoral arteriography. Tc-99m can readily be obtained by elution from a 99 MO “cow.” It has been used widely for various scanning technics and can be obtained commercially in ampules for use without further preparation. Tc-99m is an isomer of Tc-99, emitting two gamma rays (140 and 142 kev) with a physical half-life equal to six hours. Tc-99 emits no beta particles, which only contribute to the radionuelides in medicine. The daughter of Tc-99m (Tc-99) also is radioactive. However, because it has a very long half-life (2.1 x lo5 years ; 1 mc of Tc-99m decays completely to only 3.3 pc of Tc-99), the radiation dose from Tc-99 is negligible. Utilizing a scintillation detector measuring 1 inch in diameter and an analog recorder, the activity needed to localize an artery is approximately 100 ,.Lc,This results in a whole body dose equal to 1.3 mrads. In comparison to routine radiographic and fluoroscopic studies, the whole body dose for a straight chest film would be 0.4 mrads ; a dental whole mouth series would be 46.6 mrads; a gallbladder series would be 15.6 mrads. Therefore, the whole body dose from this procedure is only slightly greater than that from a chest roentgenogram and considerably less than that from many standard radiographic and fluoroscopic procedures. The radiation doses to the parts of the body from this procedure are estimated to be: male gonads, 1.2 mrads; female gonads, 1.6 mrads; gastric mucosa, 10 mrads ; intestinal mucosa, 16 mrads ; thyroid, 2.7 mrads. Again, these doses are well below levels known to cause somatic damage and are in the range accepted in other diagnostic procedures utilizing ionizing radiation.
Technetium
Method The femoral artery is punctured, utilizing a Cournand type of needle. A 100 pc dose of Tc-99 in 10 cc of saline is injected, and the time of circulation from the site of injection to the popliteal region is determined by means of a scintillation probe placed over the knee. The proximal film for the thigh vessels is exposed at the
end of the injection. Exposure of the second film is made to coincide with the previously determined time of probe deflection after the injection of Tc-99. Films are taken on a 36 inch mounted cassette with a 60 inch film distance. Lateral shifting of the cassette, using lead shielding, is used for two different exposures, thus facilitating visualization of the entire leg. The role of the technetium is to help in the proper timing of the film’s exposure, which is dependent on blood flow and therefore directly proportional to the degree of vascular occlusion. In determining the circulation time, we have found that the time should be determined from the initial deflection of the needle and not at the point of maximal deflection.
Tc-99m
in Peripheral
Arteriography
be obtained in almost all cases with a single injection, without shifting the patient, and without a film changer. The patient is saved the added discomfort and morbidity of prolonged procedures and multiple injections. In addition, valuable information concerning the peripheral blood flow is obtained by accurate determination of the circulation time. This technic has been used in an unselected series of sixty patients with clinically suspected occlusive disease of the femoropopliteal arteries. We have encountered no problems that are not those inherent in puncture of a peripheral vessel and injection of contrast medium. The average circulation times (femoral to popliteal) have been eight to nine seconds. More prolonged circulation times would be more likely in the presence of occlusion of the superficial femoral artery without adequate collaterals, implying recent or acute occlusion. Summary
Results
Utilizing Tc-99 for evaluation of circulation time, adequate examination of both the proximal and distal vascular bed in the lower extremity can
Volume
122, September
1971
A simple method of determining peripheral circulation time and timing of exposures of peripheral arteriography is described. The technic and its advantages are briefly discussed.
409