Spanish Ballroom
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Wednesday, June 2!, 1967 9:00—10:30 A.M. Spanish Ballroom SESSION A. BRAIN AND CEREBRAL BLOOD FLOW Session Chairman: WILLIAM H. OuENDoiw, Los Angeles A-i “Comparisonof Indiam 113-rn Chelates and Technetium-99m Pertechnetate as Brain Scanning Agents.― H@i@Y N WAGNER JR., HOWARD S. Si'i@'.m'iAND DAVID A. GOODWIN, (Division of Nuclear Medicine, The Johns Hopkins Medical Institutions, Baltmore, Md.) A major factor in the improved accuracy and better quality of brain scans over the past few years has been the greater yield of emitted photons resulting from the use of multi millicurie doses of the short-lived radionuclide, technetium-99m. Disadvantages of 99mTc @ pertechnetate are : ( 1 ) the short half-life of the parent nuclide, which must be obtained at weekly intervals; (2) the high blood level at the time of the scan may obscure lesions in highly vascular areas; and ( 3 ) the tumor-brain concentration ratios are not as high as we would like. Therefore, it seemed desirable to search for a better agent. Indium-113m can be less obtained from the parent nuclide, @3Sn,which has a half-life of 118 days and therefore needs to be purchased only at six- to eight-month intervals. We pre pared and screened several complexes of indium and found that indium chelates, such as diethyltriamine-pentaacetic acid (DTPA), gave tumor: brain concentration ratios of about 30: 1 in experimental tumors in mice. Indium chelates ( EDTA and DTPA) readily diffuse into the extracellular fluid and are also rapidly excreted by the kidney. The blood clearance half-time of indium chelates in man is about 70 minutes, with over 50 per cent of the admin istered dose appearing in the urine in approximately two hours. The physical characteristics of Indium-113m (1.7 hour half-life, no beta emission) allow millicurie doses to be given without danger of excessive patient radiation. The higher energy of ll3mIn (390 keV) requires collimators with thicker septa than those used with Technetium-99m. To achieve equal sensitivity, it was therefore necessary to use collimators with less spatial resolution. We compared 99mTc pertechnetate and ll3mln DTPA in paired studies of a series of a series of patients with a variety of brain tumors and other mass lesions. Accumulation of radioactivity in the mucous glands of the face, the frontal sinuses, salivary glands and choroid plexus noted with O9mTc pertechnetate were not seen with 113mJ@DTPA. Consequently, it was not necessary to administer atropine and perchlorate (as we do in the case of pertechnetate) to remove these normal areas of concentration that occasionally lead to problems in interpretation. Tumors and other lesions were visualized equaly well with both agents. At this time, it appears that ll3mIn is as good as O9mTc as a brain scanning agent. A-2 “AComparison of In-113 and Tc-99m as Agents for Cerebral Scanning.― ROBERT O'M@u1A,GOPAL SUBRAMANIAN, AND JoHN G. MCA1@, (Department of Nuclear Medicine, Upstate Medical Center, State University of New York, Syracuse, New York.) Like Tc-99m, In-113m is a short-lived daughter radionuclide available from a radioiso tope generator system (physical half-life—104 minutes: gamma emission—.393 MeV). It is eluted from a column of hydrous zirconium oxide containing the parent Sn-i 13 with .05 N HC1 or HNO1. The eluant contains no radiochemical impurities and the leakage of parent Sn-i 13 activity is only i0@ to 106 times the activity of radioindium. The long half-life of the parent nuclide of 118 days offers an economic advantage over the 99mTc generator system. However, a higher fraction of the gamma photons of In-i 13m undergo internal conversion than for Technetium-99m. Consequently, the tissue radiation dose from In-il3m is higher. Because indium is a trivalent cation, it can be easily complexed with various chelating agents, including amino acids. Preliminary screening of 13 different complexes of radioindium 261 262 ABSTRACTS in mice indicated its potential value as an agent for cerebral scanning. A comparison of the tissue distribution was made between In-1i3—DTPA, In-il3m—tryptophane and Tc-99m pertechnetate in C 57 mice with transplantable ependymoblastoma. In-113m—DTPA produced higher tumor-to-brain concentration ratio and a more rapid blood clearance than other agents. The subcellular distribution of these radioactive agents was studied by zonal centrifugation. Preliminary trials of In-i 13m—DTPA compared with 99mTc pertechnetate indicate that the former agent has superior biological characteristics. No concentration is seen in the choroid plexus or in the salivary glands. The rapid blood clearance allows scanning to begin almost immediately after injection and the vascular structures appear less prominent. Because of the higher energy of its gamma omission, however, the resolution obtained with In-i 13m is somewhat inferior to Tc-99m. Brain scans comparing the two compounds will be shown. A-3 “Rapid Sequential Cranial Scintiphotography for the Vascular Characteriza tion of Brain Lesions.― M@rrii@ws B FISH, MYRON POLLYCOVE, SEAN O'REILLY AND ARCHIE KHENTIGAN, (Niicli@Medicine Section, Clinical Laboratories, San Francisco General Hospital, Division of Clinical Path ology and Laboratory Medicine, Department of Pathology, University of California School of Medicine, San Francisco, California) The ready availability of near-ideal nuclides for clinical use such as D9mTc and the development of the Anger-type scintillation camera has made possible the imaging of a number of vascular structures and organs. Utilizing this approach, a procedure involving rapid serial scintiphotography of a vascular isotope bolus as it transverses these structures was devised. Rapid safe assessment of the vascular nature of intracranial lesions is accomplished employing an antecubital intravenous bolus injection of 9DmTc@pertechnetate ion, 10 mC, and an Anger type scintillation camera with standard manual photographic attachment. Rapid sequential studies obtained in over 20 subjects without demonstrable intracranial lesions exhibited the following vascular phases on anterior view : Aorta—early carotid arteries, mean of 5.3 sec. after injection; carotid and cerebral arteries, 7.9 sec.; cerebral arteries—capil laries, 9.5 sec.; early venous, 10.5 sec.; and late venous, 12.5 sec. The routine procedure which has evolved from these studies involves sequential scintiphotography at 1.5 sec. intervals after bolus injection followed by conventional multiple view cranial scintipho tography at i-5 minutes (vascular equilibration) and 60-80 minutes (extracellular fluid equilibration). Such studies have been performed in over 80 patients with suspected intra cranial pathology. The vascular nature of all demonstrated lesions was easily established. Primary neoplasms including malignant glioma and meningioma as well as vascular malfor mations exhibited increased vascularity. Cerebral infarcts and subdural hematomata demon strated decreased vascularity. In summary, this technique affords a simple, rapid, safe procedure for routine assessment of cerebral vascular disease and vascular characterization of intracranial lesions. These favor able features allow its use in outpatients, as a means of screening patients for cerebral arteriog raphy, as well as in patients in which cerebral arteriography is contraindicated. A-4 “KineticStudies in Brain Scintiphotography.― MARsIIAu S MILLER, AND Gu@ H. SIMMONS,(Departments of Radiology and M@di@ine,University of Cin cinnati College of Medicine and Training and Manpower Development Program, National Center for Radiological Health, U.S. Public Health Service, Cincinnati, Ohio) Kinetic studies on 20 individuals undergoing brain scintiphotography with intravenous pertechnetate demonstrate the necessity for a 30-minute interval between injection and start of examination. Count rates registered by the gamma camera were recorded continuously on a strip chart from the time of injection until at least one hour later and correlated with serial scintiphotos and blood levels. The patients remained motionless throughout the pro cedure. An initial peak brain count rate at 17 seconds is associated with high concentration in large vessels. As pertechnetate disseminates into tissues, the count rate falls by 35% to a minimum at 49 seconds and pictorial detail becomes poor. As 99mTc collects in venous struc FOURTEENTH ANNUAL MEETING 263 tures, the count rate again rises. Maximum concentrations in antecubital and finger blood are found at about one minute, then begin a decline well described by a power function. Brain count rate continues to rise to a second maximum at five minutes and persists six mm utes before gradual decline. When pictures are taken with facial structures ( salivary glands, etc. ) shielded from the view of the crystal, there is little or no effect on the kinetic phenomena described. Photographic detail is improved by use of a newly available 4000-hole collimator. It would seem desirable to obtain scmntiphotos when the camera brain count/antecubital blood count ratio is maximum. This point is seldom reached before 30 minutes. Patients pre-treated with perchlorate maintain a lower brain/blood count ratio than the same patients studied without perchiorate. Cases are presented to show the possibility of missing lesions by examin ing a patient too soon, even though count rates over brain are higher at earlier times. This consideration is especially important in scmntiphotography compared to rectilinear scanning because of the swiftness with which all views are begun and taken on the gamma camera. A-5 “Correlationof Cerebral Blood Flow Dynamics with Time Lapse Scinti photography Using the Gamma Camera with Multichannel Analyzer.― KENNETH 0 HENDRICKS, JAMES T. LAMBETH, AND ALEXANDER GorrsciIAu, (ArgonneCancerResearchHospitalandthe Universityof Chicago,Chi cago, Illinois) Using an Anger Camera, modified 70 mm roll film magazine, and a RIDL 1600 channel analyzer, dynamic studies of cerebral blood flow have been performed on over thirty patients. Ten mC of 9OmTc pertechnetate were injected via an antecubital vein with the subject posi tioned beneath the camera in a half-axial projection similar to that used in carotid arteriog raphy.