Teruo Odori

A quantitative assessment of scintigraphy of the legs using 201Tl

Abstract201Tl perfusion scintigraphy of the legs was evaluated to define intermittent claudication quantitatively, based on Sapirsteins indicator fractionation principle. After intravenous injection of 201Tl with or without exercise, the distribution of the radiotracer throughout the body was obtained using the whole body scanner. Regional blood flow of cardiac output for three segments of the leg was estimated as a regional fractional uptake (rFU) distributed in these segments compared with the whole body distribution. The validity of the principle was confirmed by a comparative study with 99mTc-MAA (r=0.979). Normal rFUs (%) for each section at rest and after stress, respectively, were 5.49±0.69 and 19.40±2.04 (whole leg); 3.57±0.49 and 12.26±1.91 (thigh); 1.59±0.34 and 6.58±0.61 (calf). The rates of rFU change from the state of rest to stress (ΔrFU) in normals were 3.41±0.45 (whole leg), 3.44±0.61 (thigh), and 4.30±1.03 (calf). Although rFU was within normal limits in patients with arteriosclerosis obliterans (ASO) and thromboangitis obliterans (TAO), ΔrFU of the whole leg was significantly decreased from the normal value of 3.41±0.45 to 1.95±0.40 for ASO (P(0.001) and 1.82±0.47 for TAO (P(0.001). A defect or decreased activity on the stress scintigraph was well correlated with the angiographic findings.

Application of a self-expanding metallic stent to a strictured esophagojejunostomy

We placed a Gianturco self-expanding metallic stent across the recurrent stricture of an esophagojejunostomy in a patient with gastric cancer. Though excellent passage of food resulted, intractable reflux occurred. Two months later the patient succumbed to recurrent tumor. At autopsy, the stent was patent and was partially covered by esophageal mucosa. There were narrow but deep ulcers around the stent hooks. The Gianturco metallic stent may provide an additional option for treating recurrent enteric strictures after other methods fail. Further refinements of the technique appear necessary.

Technetium coordination state as a factor of stability in 99mTc-complexes used in hepatobiliary system: Comparative studies on 99mTc-complexes of pyridoxal with glutamate (Tc-PG) and isoleucine (Tc-PI)

Studies on 99mTc-Penicillamine (Tc-Pen) have given us some insight into the significance of the technetium coordination state in hepatobiliary clearance behavior.A 99mTc-complex of pyridoxal and glutamate (Tc-PG) prepared by Baker et al. (1975) using an autoclaving process or by a Sn-Resin kit method (Horiuchi 1981) was compared with a 99mTc-complex of pyridoxal and isoleucine (Tc-PI) prepared by the method of Kato and Hazue (1978) through an intermediate compound of stannous ion, at room temperature.Tc-PG and TcPI complexes analyzed by thin layer chromatography, sephadex column chromatography (G-15), octanol extraction, and ligand exchange reaction showed different chemical properties. Their biological evaluation also demonstrated great differences in biodistribution in mice, metabolic studies, protein binding, and rat bile excretion.Tc-PG was estimated as an hepatobiliary agent with strong metal-ligand binding, inert to ligand exchange reaction with Pen at physiological pH; the likely occurrence of technetium in a mononuclear or dinuclear state providing the great stability observed in its biological and in vivo behavior was compared with the relatively weaker binding observed in Tc-PI, a highly lipophilic complex of high liver partition but of low stability, denoting its different chemical characteristics.The technetium coordination state in radiopharmaceuticals is responsible for the integrity of the molecule while in the blood pool and its relevance in impaired liver uptake is discussed.

Superimposition of Krypton-81m single photon emission CT and X-ray CT images for cerebral blood flow evaluation.

Selective arteriographic infusion of krypton-81m was used to obtain cerebral single photon emission computed tomograms. These were then superimposed on X-ray computed tomograms to assess topographically the perfusion of the entire brain. This method enhances the detecting capability for abnormal perfusion areas and has been used in 21 patients with various brain diseases.

Tin-adsorbed resin for the preparation of 99mTc-radiopharmaceuticals: Stable complex of 99mTc-bleomycin

Stannous chloride has been the reducing agent of choice for the preparation of 99mTc-containing radiopharmaceuticals, whose effective chemical form is considered to be a complex, or complexes, of the reduced form of technetium. Labeling of 99mTc-BLM, a technetium complex of bleomycin, has been reported previously, but a stable complex for adequate clinical evaluation has been difficult to obtain. The main role of stannous chloride is as reducing agent but, depending upon the amount and the chemical state of the stannous ion, other phenomena have been detected and further implications for the incorporation of 99mTc into a ligand are discussed. However, the stannous ion adsorbed onto a cationic exchange resin showed specific characteristics allowing the preparation of a stable complex of BLM, considered to be a mononuclear complex. The usefulness of this tin-adsorbed resin (Sn-resin) as an efficient device (kit) for the controlled delivery of Sn2+ ion, permitting the simple preparation of a stable complex with good reproducibility in Nuclear Medicine facilities is presented.

The importance of the chemical state of 99mTc radiopharmaceuticals: an effective tumor imaging form of 99mTc bleomycin

Abstract 99 m Tc-labeled bleomycin ( 99 m Tc-BLM) has been introduced as a tumor-imaging agent. Nevertheless, this complex has been misjudged and its value for clinical use has received no proper evaluation. Various 99 m Tc-BLM species labeled with 99 m Tc in different chemical states are produced depending upon the labeling conditions such as the concentrations of BLM and SnCl 2 , pH and reaction time. As a consequence, their biological behavior is found to be markedly affected by the state of 99 m Tc in the labeled compound administered. Detailed studies of the labeling reactions lead us to conclude that of the complexes tested, a 99 m Tc-BLM complex in which tetravalent 99 m Tc is coordinated through three nitrogen atoms of BLM, is considered to be a valuable one for clinical use. This 99 m Tc species is chemically the most stable and a rapid clearance from blood is obtained; yielding a high tumor-blood ratio of 99 m Tc activity after injection into tumor-bearing mice. A selective labeling method for this 99 m Tc complex is described.

Analysis of 99mTc-pyridoxylidene-glutamate complex formation and its preparation with tin-adsorbed-resin: Sn-Resin kit method.

Abstract99mTc-Pyridoxylidene-glutamate (Pc-PG) was introduced in 1975 by Baker et al. as a cholescintigraphic agent. Nevertheless its routine use has been limited due to the autoclaving process involved. To shorten the labeling procedure, an analysis of Tc-PG complex formation using the stannous chloride method was carried out. Sn-Resin (stannous ion adsorbed onto cation exchange resin) was used for labeling a stable Tc-PG with high efficiency. A preautoclaved complex of pyridoxal and glutamate was required but the labeling procedure took only 10–15 min after the elution of 99m-TcO4-from the generator.Formation of a complex other than a 99mTc-complex of the Schiff-base ligand pyridoxylidene-glutamate is discussed.The new formulation of a Tc-PG kit (Sn-Resin) simplified the labeling method and reproducible data to that already reported by Baker was obtained in chromatographic studies. Its suitability in hospital departments has already been shown in clinical studies.

Evaluation of 99mTc-HIDA Complex as a Cholescintigraphic Agent

In the reaction labeling N-(2,6-dimethylphenylcarbamoylmethyl) iminodiacetic acid (HIDA) with 99mTc, several complexes with different chemical characteristics were observed to occur with slight changes in the labeling conditions. Among these complexes, a complex detected in the bile of rats was limited to one complex, named as complex II. The preparation method of 99mTc-HIDA complex II and the exchange reaction between this complex and penicillamine indicate that 99mTc is coordinated with HIDA as low-hydrolyzed 99mTc in this complex. This complex is excreted rapidly through the bile and within 1 hr, about 65% of the total activity injected is recovered from bile in rats. The organ distribution of this complex was studied in mice by radioassay and in rabbits by scintillation camera and, in both cases, the radioactivity was accumulated in the gallbladder. These results suggest that the 99mTc chemical state, low-hydrolyzed state, relates to the bile excretion behavior of this complex, a potentially useful cholescintigraphic agent.

99mTc-2-Mercaptopropionylglycine : Different Biliary Excretion Behavior in Different Animal Species

Labeling of 2-mercaptopropionylglycine (2-MPG) with 99mTc, was studied and its chemical characteristics were examined. Further, biliary excretion behavior of this complex was comparatively estimated in mice, rats, and rabbits. 99mTc-2-MPG was rapidly excreted in large quantities into the bile in mice and rats: within 1 hr after injection, 51% of the injected dose was recovered from the bile in rats. On the other hand, the ligand exchange reaction between this complex and penicillamine indicates that a low hydrolyzed 99mTc species is coordinated with 2-MPG. These results suggest that a low hydrolyzed 99mTc is an effective feature in biliary excretion behavior of 99mTc compounds. Another interesting in vivo behavior of 99mTc-2-MPG is the difference observed in mice and rabbits: in mice, very high 99mTc activity is concentrated in the gallbladder and the clearance from tissues other than the gallbladder is rapid, whereas in rabbits, although a rapid and high excretion into the gallbladder is observed, a considerable high 99mTc activity is retained in the liver and the kidney. One reasons for this different in vivo behavior is the low stability of this complex at high dilution: a big animal has the large dilution volume which lead to higher decomposition estimated by the higher liver and kidney retention or the lower bile excretion. In conclusion, studies carried on 99mTc-2-MPG showed a good biliary excretion behavior but an in vivo unstableness in big animals.