Tc-Labeled Colloids

Diffuse pulmonary accumulation of radiocolloids may result from elevated plasma levels of aluminum in patients with antacid therapy, because the Tc-tin colloid coprecipitates with larger aggregates of aluminum phosphate (Ponto et al. 1987). A number of clinical conditions associated with pulmonary uptake of Tc-labeled colloids have been reported (Hladik et al. 1987 a). 

Increased splenic uptake has been seen with decreased liver function, i.e., cirrhosis (Atkins et al. 1975). Extrahepatic accumulation of " Tc-labeled colloids is also seen in the bone marrow in the case of hyperplastic bone marrow and with certain hematological disorders (Hofer and Egert 1963 Hofer et al. 1964 Nelp and Bower 1969). Occasionally, uptake has been observed in the lung and kidneys (Klingensmith et al. 1976). 

Androgen therapy may stimulate the phagocytic activity of the RES, so that macrophages are released from storage sites and trapped in the lung. In the lung these phagocytic cells extract the Tc-labeled colloid (Hladik et al. 1987 b). 

Nagai K, Ito Y, Otsuka N, Muranaka A (1982) Deposition of small Tc-labeled colloids in bone marrow and lymph nodes. Eur J Nucl Med 7 66-70 Nitz DWP, Heidenreich P (1999) Sentinel-Lymphknoten. In Der Nuklearmediziner. Demeter, Munich... 

Radiopharmaceutical formulations based on ° Tc may be divided into two major classes. The Class I formulations include what may be described as technetium tagged materials. These may be particles such as cells or colloidal substances, or they may be molecular species such as proteins or other large biological molecules. The essential feature of these agents is that their biodistribution behaviour is determined by the nature of the substrate material. Thus the attachment of a Tc label should have little or no effect on their biodistribution. However, it cannot necessarily be assumed that this will be the case, especially when relatively low molecular weight substrates are involved. 

Studies of liver structure may be carried out using colloidal dispersions labelled with " Tc. The " Tc-sulfur colloid provides one such example and is usually described as Tc2S7, although its chemical composition remains uncertain. An improved method for the preparation of this... 

For Tc labelled peptides, ITLC-SG analysis was accomplished using three different mobile phases 2-Butanone to determine the amount of free TcO (Rf = 1), O.IM sodium citrate at pH5 to determine Tc coligand and TCO4 (- f = 1)> and methanoklM ammonium acetate (1 1 vol./vol.) to determine Tc-colloid (Rf = 0). The Rf values of the radiolabelled peptide in each system were 0.0,0.0 and 0.7-1.0, respectively. 

Another aspect is hydrolysis and colloid formation. During the reduction of pertechnetate with stannous salts, tin is oxidized and hydrolyzed to form highly polydispersed colloidal particles. In some cases, mainly when weak or unsuitable ligands are used in the " Tc labeling, interference of colloidal tin oxides on the biodistribution of " Tc-radiolabeled tracers may occur. Such effects and the biodistribution of Tc-Sn colloid in dependence of the preparation conditions were subject of detailed studies. 

Belkas EP, Archimandritis S (1979) Quality control of colloid and particulate " Tc-labelled radiopharmaceuticals. Eur J Nucl Med 4 375... 

The kit contains the lyophilized, sterile ingredients in a multidose vial. Labeling with 99mrpc-pertechnetate is carried out under aseptic conditions by adding a suitable volume of sterile Tc eluate, up to 3.7 GBq (100 mCi) to the reaction vial. The reaction is allowed to proceed at room temperature for 20 min. Tc-tin colloid is a sterile, pyrogen-free, opalescent solution suitable for intravenous injection. The pH is 4.0-6.0 on pH paper. 

The liver, spleen, and red marrow are the most exposed organs. Calculations of the absorbed radiation dose resulting from liver and spleen scintigraphy are based on technetium-labeled colloids (International Commission on Radiological Protection 1987). The effective dose equivalent is 0.014 mSv/MBq. The effective whole-body dose in adults (70 kg) resulting from an intravenous injection of 185 MBq of Tc-tin colloid is... 

Inorganic colloids may remain within the macrophages indefinitely. It has been reported, however, that Tc-labeled sulfur colloid may be metabolized and excreted (Warbick-Cerone and Phythian 1982). However, the urinary excretion (in 48 h) measured in three patients was less than 4% of the injected radioactivity (Larson and Nelp 1966). 

The NanoCis kit (TCK-17) consists of two vials, A and B. Vial A contains a sterile, pyrogen-free solution of ingredients. Vial B contains lyophilized sodium pyrophosphate and stannous chloride. Two milliliters of sterile water for injection are added to vial B to dissolve its content. Half a milliliter of solution B is transferred to vial A, and mixed well. Then, 1-2 ml of Tc eluate is added under aseptic conditions (not less than 370 MBq [10 mCi] to assure a specific activity of > 100 MBq/ml/0.15 mg). The reaction vial is placed into a boiling water bath for 15-30 min. After cooling, the labeled colloid is ready for use. 99mTc-(Re)-sulfide nanocolloid is a sterile, pyrogen-free, brown solution, suitable for subcutaneous (interstitial) injection. The pH is between 4.0 and 7.0 on pH paper. 

The liver and spleen can be studied with Tc-labeled sulfur colloid. Space-occupying lesions such as cysts, abscesses, hematomas, or tumors can be detected in static images. For hepatobiliary evaluation derivatives of iminodiacetic acid labeled with... 

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