Evaluation of an anti-carcinoembryonic monoclonal antibody suitable for immunoscintigraphy.
(17/1995)
An anti-carcinoembryonic antigen (CEA) monoclonal antibody (mAb 6D1. 1) was evaluated in vitro and in vivo to determine its suitability as a tracer for immunoscintigraphy of colorectal carcinomas. Determination of mAb affinity for CEA showed a constant of association of 0.63 +/- 0.11 x 10(9) M-1. Binding of technetium-99m (99mTc)-6D1.1, labeled by a direct method, to human cultured lineages was highly specific. Binding to only CEA-positive LS-174T cells resulted in a saturable curve inhibited by pre-incubation with unlabeled mAb. No binding at all was observed for the human lineages MeWo (melanoma) or ZR75-30 (breast carcinoma), neither of them expressing CEA cells. Intravenous injection of 99mTc-6D1.1 into nude mice xenografted with human LS-174T tumors resulted in planar images of excellent quality. Localization of an irrelevant mAb labeled with either 99mTc or iodine-125 was never observed in tumor masses. Biodistribution studies on excised tumoral tissue showed retention of 28.48% of the injected dose per gram of LS-174T tumor. The tumor-to-blood ratio was 3.46. The same analysis performed on the other three human xenografted tumors studied demonstrated that only the CEA-producing HT-29 (colorectal adenocarcinoma) retained 99mTc-6D1.1 while the other two (ZR75-30 and MeWo) did not. These data demonstrate that this mAb is an adequate tool for targeting CEA-expressing tumors in experimental models. (+info)
Scintigraphic assessment of pulmonary and whole-body blood flow patterns after surgical intervention in congenital heart disease.
(18/1995)
Glenn shunt and Fontan procedure, the most widely used surgical procedures in congenital heart anomalies, may be associated with abnormal pulmonary blood flow patterns and the development of pulmonary arteriovenous fistulae. METHODS: This study quantified pulmonary and whole-body blood flow using the microsphere technique by sequential injection of 99mTc microspheres into upper and lower limb veins and performing planar lung imaging in four projections and anterior and posterior whole-body scans in 46 patients with either Glenn shunt or Fontan procedure. The right-to-left shunt volume was estimated by a brain and kidneys-to-lungs ratio and compared with calculations from the whole-body scans. RESULTS: In 31 of 46 patients, the blood from the superior vena cava was drained preferentially into the right lung (75%+/-19%). The inferior venous system was drained equally into both lungs. The right-to-left shunt volume was 24%+/-12% after injection into the superior caval system, 50%+/-18% after injection into the inferior caval system. A subgroup of patients who had undergone a palliative Blalock-Taussig shunt (BTS) before the final surgery showed a perfusion pattern that was not known after pulmonary angiography or contrast echocardiography: 15 of 24 patients with BTS had hypoperfusion of the upper lobe on the side of the BTS after injection into the arm vein and corresponding normal perfusion or hyperperfusion when injected into the foot vein. CONCLUSION: Lung perfusion scintigraphy after tracer application into the superior and inferior caval systems detects more abnormal pulmonary blood flow patterns than contrast echocardiography and is the only procedure able to quantify right-to-left shunt volume individually for the superior and inferior caval systems. Thus, this diagnostic technique should be part of the routine follow-up in children after Glenn shunt or Fontan procedure. (+info)
High RBC labeling efficiency by controlling pretinning with the modified in vivo/in vitro labeling method.
(19/1995)
OBJECTIVE: The image quality for gastrointestinal bleeding studies depends on the efficiency of red blood cell labeling. The in vitro technique has been used widely because of its high labeling efficiency. New data for the modified in vivo/in vitro method are lacking. This study reports on the high labeling efficiency that can be obtained with the modified in vivo/in vitro method and the pitfalls to avoid. METHODS: A consecutive series of 91 labeling studies was analyzed. Different amounts of tin, red blood cell concentrations, and infusions of interfering substances also were studied. RESULTS: A mean efficiency of red blood cell labeling of 97% (80%-99%) was obtained. Only 3 cases showed unacceptable results. Suboptimal results were obtained with amounts of tin below 10 microg SnCl2/kg body weight, a reduced hematocrit, and blood transfusion or infusion of HES solution during pretinning. CONCLUSION: The modified in vivo/in vitro red blood cell labeling technique is performed easily, is useful and is comparable to the gold standard in vitro method, provided that the pretinning period is controlled carefully. (+info)
The significance of incidental noncardiac findings in Tc-99m sestamibi myocardial perfusion imaging: illustrated by a case.
(20/1995)
Technetium 99m sestamibi is widely used in the evaluation of myocardial perfusion imaging. Although the aim of such imaging is cardiac evaluation, numerous other organs are included in the imaging field. Failure to identify incidental abnormal findings in these organs delays diagnosis and treatment. In common with other radiopharmaceutical agents, technetium 99m sestamibi is distributed throughout the body and accumulates in multiple tissues. When interpreting studies that involve this radiotracer, the physician must be aware of its physiologic distribution, in order to recognize abnormal uptake. We present an illustrative case in which areas of decreased tracer activity were noted incidentally during the evaluation of unprocessed single photon emission computed tomography data. These findings were due to metastasis of colon cancer to the liver. (+info)
Clinical correlation of hepatic flow studies.
(21/1995)
In 100 consecutive hepatic flow studies, 84 were read as negative. Of these, 73 (87%) also had negative static images. Knowing the nature of the primary tumor did not definitively aid in predicting whether hepatic meastases would have detectable early flow. Five cases showed early flow without defects seen in the static images. Three of these were probably related to lymphomas or allied disorders with altered flow. Two cases were in individuals with gastric carcinoma who had abdoninal radiation. One extrahepatic tumor was detected in the series. (+info)
Forward cardiac output measurement with first-pass technique using 99mTc-labeled myocardial perfusion imaging agents.
(22/1995)
The aim of this study was to develop and validate a new first-pass method for the measurement of forward cardiac output (CO) using 99mTc-labeled myocardial perfusion imaging agents. METHODS: In protocol 1, to test the new method for measuring CO, the conventional method and the new method for CO measurement were performed in 1 d in 57 patients (32 men, 25 women; age 68 +/- 11 y). In the conventional method, radionuclide angiography (1 frame/s) with in vivo 99mTc labeling (110 MBq) of red blood cells was performed for 2 min in the left anterior oblique projection. Five minutes later, a 1-min equilibrium image was obtained, and a blood sample was taken for calculation of the distribution volume. To obtain data for the new method, further radionuclide angiography (1 frame/sec) with 99mTc labeling (600-740 MBq) of red blood cells was then performed in the anterior projection. CO was calculated using the following equation: CO = Cmax x V(LV)/integral of f(t)dt, where Cmax is the background-corrected peak count of the whole thorax during angiography, integral of f(t)dt is the area under the gamma variate-fitted left ventricular (LV) time-activity curve after background correction and V(LV) is the LV volume obtained by the area length method applied to the radionuclide angiography and myocardial tomography. In protocol 2, to evaluate the new method, 24 patients (16 men, 8 women; age 71 +/- 9.2 y) underwent radionuclide angiography with 99mTc-tetrofosmin (600-740 MBq), and the measured CO was compared with the CO obtained by the conventional method with 99mTc-labeled red blood cells. RESULTS: In protocol 1, good correlation was observed between the CO by the new method (Y) and the CO by the conventional method (X): Y = 1.0X + 57 mL/min and r = 0.95. There was good agreement between the two methods (mean difference -56 +/- 381 mL/min). Inter- and intraobserver correlation coefficients were 0.96 and 0.98, respectively. In protocol 2, the CO by the new method using 99mTc-tetrofosmin (Y) showed a good correlation with the CO by the conventional method (X): Y = 0.90X + 453 mL/min and r = 0.93. Good agreement between the two methods was observed (mean difference 73 +/- 390 mL/min). Inter- and intraobserver correlation coefficients were 0.95 and 0.98, respectively. CONCLUSION: This new method permits accurate forward CO measurement using the first-pass data with 99mTc-terofosmin, which is applicable to other 99mTc-labeled myocardial perfusion imaging agents. (+info)
Organometallic 99mTc-aquaion labels peptide to an unprecedented high specific activity.
(23/1995)
A new peptide labeling method that uses the organometallic aquaion [99mTc(H2O)3(CO)3]+ has been developed. METHODS: A selection of amino acids was labeled at different concentrations with the organometallic aquaion, and the labeling yield was determined by high-performance liquid chromatography. This investigation has shown histidine to be a very potent ligand, with specific activities of up to 6 TBq/micromol (160 Ci/micromol) ligand. Histidine derivatives have been coupled to neurotensin(8-13) (NT[8-13]) and have been labeled with the aquaion, resulting in high specific activities with (N(alpha)-histidinyl)acetic acid-NT(8-13) similar to those with histidine. RESULTS: Histidine derivatives of NT(8-13) labeled using this approach fully retained their receptor affinity, showing KD values of all investigated NT analogs below 1 nmol/L on colon carcinoma HT29 cells. Biodistrbution experiments in BALB/c mice showed complete clearance of (N(alpha)-histidinyl)acetic acid-NT(8-13) from the blood after 24 h and no unwanted accumulation in any tissue. CONCLUSION: The novel labeling method using the organometallic 99mTc-aquaion combines the advantage of highest specific activities with minimal functionalization of proteins and peptides under retention of biologic affinity. (+info)
Entry of CART into brain is rapid but not inhibited by excess CART or leptin.
(24/1995)
Cocaine- and amphetamine-regulated transcript (CART) is a new anorectic peptide found in the brain and periphery. It is closely associated with leptin, an anorectic agent saturably transported across the blood-brain barrier (BBB). Using multiple time-regression analysis, we found that CART has a rapid rate of entry into brain from blood. However, there was no self-inhibition with CART, even when perfused in blood-free buffer or in fasted mice, showing a lack of saturation. HPLC showed that at least 58% of the injected CART reached brain tissue in intact form, and capillary depletion with and without washout showed that the CART was not bound to endothelial cells or adherent to vascular components. There was no evidence for an efflux system out of the brain for CART. Thus CART can cross the BBB from blood to brain, but its rapid rate of entry is not inhibited by excess CART or leptin. (+info)