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Recent studies suggest that 99mTc-labeled radiocolloid (SC) compounded with hydrogen sulfide can be used to visualize lymph channels and nodes. Our study prospectively compared SC with 99mTc antimony sulfide (SbS) colloid, in 28 patients undergoing internal mammary lymphoscintigraphy. Images were recorded on a scintillation camera and computer at 0.5, 1.0, and 3.0 hr. Quantitative analysis included assessment of percent (%) injected dose in nodes, the percent remaining at the injection site, and the relative intensity of the most cephalad node compared to a 57Co standard. The mean (means) % injected dose of both radiocolloids within visualized nodes was less than 1% at each time interval, with no significant differences between means's. The means % injected dose remaining at the injection site at 3.0 hr was 83 for SbS and 76 for SC not statistically significant (N.S.). The means of the ratio of counts within the most cephalad node at 3.0 hr to counts within a 57Co standard was 0.98 for SbS and 1.03 for SC (N.S.). Clinical assessment of number of nodes visualized and extent of radiocolloid migration showed no difference between the two agents. The biological and clinical parameters for the two colloids appear similar when used for internal mammary lymphoscintigraphy.

Studies in dogs showed that heat-treated 99mTc-labeled red blood cells (HT/RBC) afford a highly sensitive means of detecting gastrointestinal bleeding as low as 0.12 ml/min., which could not be seen with unheated 99mTc-RBC, 99mTc-sulfur colloid, or 99mTc-DTPA. In addition, as the right upper quadrant and epigastrium remained free of activity, only one fifth to one tenth of the dose of 99mTc was needed. The safety of HT/RBC in humans has been documented, and the experiments in dogs suggest that it may have advantages over other agents in detecting gastrointestinal bleeding.

For the purpose of radiation dose estimates, organ assays and excretion measurements of the Tc-99m and In-111 complexes with DTPA were conducted in dogs at various time intervals up to 24 hr, and the results compared with available human data. The peak concentration of the Tc-99m complex, at 3 min after injection, was 5% of the administered dose for one kidney, 3.5% for the liver, and 3.5% for the small bowel. No organ system except the urinary tract reached a concentration higher than that in blood for several hours after the injection. The biliary excretion of these agents was extremely low, and their elimination in the feces was negligible. In man, it appears that the residual 4-5% of an administered dose not eliminated in the urine by 24 hr is widely distributed in various tissues. The distribution of the In-111 complex is similar but not identical to that of the Tc-99m complex.

A comparison of Tc-99m-labeled human serum albumin (HSA) and in vitro labeled red blood cells (RBC) was carried out in five subjects. The disappearance of radioactivity from the blood was more rapid for HSA (T 1/2, 281.6 minutes, range 202.1--318.3) than for RBC (T 1/2, 1719.8 minutes, range 767.6--5059.5). Urinary excretion was twice as great for HSA. Ratios of activity in heart blood pool to lung and liver were considerably greater for RBC up to 2 hours after administration. The results indicate that labeled RBC are superior to labeled HSA for blood pool imaging.

Goodpasture's syndrome is characterized by the triad of glomerulonephritis, intra-alveolar pulmonary hemorrhage, and presence of antiglomerular basement membrane antibodies. It has been shown earlier that intra-alveolar hemorrhage can be detected with radioisotopic techniques. A patient with Goodpasture's syndrome showing increased pulmonary accumulation of Tc-99m DTPA with no evidence of pulmonary hemorrhage is presented.

The physical characteristics of a new tin radiopharmaceutical, 4+Sn-117m diethylenetriamine-pentaacetic acid (DTPA), may make this compound appropriate for orthopedic therapeutic application. The physical and biologic half-lives of this tracer are 14 and 7.8 days, respectively. The decay scheme consists of short-range tissue destroying beta, conversion, and Auger electrons, and a 159-keV gamma ray. Significantly, this compound has a high degree of affinity for newly calcified bone at the site of experimental burr holes in contrast to the adjacent bone marrow. Radioactive skeletal retention was one-half of whole body retention.

Technetium-99m-labeled heat-damaged erythrocytes were evaluated as a spleen imaging agent in 14 patients. Spleen-to-liver deposition ratios were increased to such an extent that the liver was rarely visualized, and interference from the hepatic left lobe of the liver was eliminated. Information obtained was accurate and diagnostically adequate in various splenic involvements. This tracer appears to be one of the better spleen imaging agents presently available.

Combined direct injection venography (DIV) and equilibrium angiography (EA) were performed in 13 patients, by injecting in vitro labeled 99mTc autologous RBC, via pedal veins, and imaging the first pass and the equilibrium phase. This paired comparative study of DIV with EA shows that DIV has advantages over EA because it provides selective information on the deep venous system from the calves to the inferior vena cava. DIV provides information on the flow dynamics and the high contrast first pass images provide better definition of non filling venous segments as well as visualization of collaterals. When using 99mTc-MAA, lung perfusion can also be imaged. DIV is recommended as the procedure of choice for the diagnosis of DVT and EA should be employed only when pedal vein injection is not possible.

The rates of blood clearance and splenic uptake as well as the total splenic uptake of heat damaged red blood cells labeled with 99mTc were determined in eight patients. Splenic uptake at two hours was 72.0 +/- 18.5%. Approximately 82.6% of the initial radioactivity was cleared from the blood by two hours, with a rapid T1/2 component of 6.3 +/- 4.7 minutes. The T1/2 of splenic uptake was 8.3 +/- 4.6 minutes, and splenic radioactivity reached a plateau by 30 minutes. The results indicate that the method of preparation is reliable, but its usefulness for evaluating spleen function remains to be determined.

99MTc-pertechnetate distribution studies were performed in rabbits and mice following pretreatment between 5--336 hours with various routinely used stannous complexes (HSA, MAA, GHT, DTPA, PYPs) containing different amounts of Sn++ (0.17--15.0 mu mg/kg). Beyond a concentration of 0.26 mu mg/kg of Sn++ an alteration in 99mTc-ertechnetate distribution was observed. The red blood cell was found to be the most prominent target. An in-vivo reduction of 99mTc-pertechnetate apparently occurred by the presence of stannous ion within the red blood cell. Preloading time period between 5--24 hours did not alter the uptake of RBC/plasma ratio. Beyond that period it decreased slowly and still persisted up to 2 weeks following pretreatment. RBC/plasma ratio of 99mTcO4-increased with increased Sn++ content of various commercially available pharmaceutical kits.

The use of radioactive labels for tracers is an important part of the investigation of renal disease. These techniques seldom replace, but often complement radiographic techniques. Generally, the radionuclide methods provide functional and dynamic information in a non-invasive, non-traumatic type of examination. The examinations usually are relatively simple to perform and carry a very low risk of untoward reaction. The past decade has seen significant advances in radiopharmaceutical design and instrumentation. It is expected that the next decade will produce an even greater advance in this field. [ABSTRACT FROM PUBLISHER]