Nuclear imaging modalities for cardiac amyloidosis.

Amyloidosis is a heterogeneous group of diseases characterized by localized or systemic deposition of insoluble extracellular fibrillary proteins in organs and tissues. Several types of amyloid can infiltrate the heart resulting in a restrictive cardiomyopathy, heart failure, and atrial and ventricular arrhythmias. Scintigraphy is a noninvasive method that may facilitate early diagnosis, distinguish various forms of cardiac amyloid, and may be useful in following disease burden. The amyloid-specific tracers presented in this article have been used with planar imaging and/or single-photon emission computed tomography. To date, there are no approved cardiac amyloid tracers although investigational tracers are currently under examination. This article serves to review the current nuclear imaging modalities available in the detection of cardiac amyloid.

Quantitation of osteoblast-like cell mineralization on tissue culture polystyrene and Ti-6Al-4V alloy disks by Tc-99m-MDP labeling and imaging in vitro.

Technetium-99m-methylene-diphosphonate (Tc-99m-MDP) labeling was used to quantify mineralization of cultures of MC3T3 osteoblast-like cells in vitro. MC3T3 cells were cultured on tissue culture polystyrene (TCPS) in mineralizing and non-mineralizing media, and then labeled by Tc-99m-MDP. The gamma signal from labeled samples was imaged with a gamma camera and compared with the calcium content in the same samples determined by inductively coupled plasma. The high correlation (coefficient of determination, 0.88) between these two values validated the radiotracer uptake method as a quantitative analytical tool for certain mineralization studies in vitro. There was an association between mineralization and radionuclide uptake in the MC3T3 cultures on titanium alloy, but the attenuation of the gamma photons by the metal resulted in a less robust correlation. The results warrant implementation of this scintigraphic method for quantitative studies of osteoblast-mediated mineralization in vitro.

[Radiochemical purity and stability of Tc-99m-pyrophosphate]. / Radiohemijska cistoca i stabilnost Tc-99m-pirofosfata.

INTRODUCTION: In vitro stability of 99mTc-radiopharmaceuticals is an important parameter of quality. In the paper the shelf-life of the bone-seeking radiopharmaceutical 99mTc(Sn)-pyrophosphate was examined under different experimental conditions. MATERIAL AND METHODS: The solution of pyrophosphate was prepared and dispensed into 2-ml fractions which were kept at-20 degrees C. In different time intervals the samples were thawed and labeled. The in vitro stability of labeled preparation was examined on the unprotected and the samples protected by nitrogen purge or by addition of solutions of ascorbic or genetisic acid of known concentrations. The content of 99mTc-pertechnetate was determined by paper chromatography. RESULTS AND DISCUSSION: In comparison with unprotected, samples protected by nitrogen purge exhibit better, but not satisfactory stability. Best results are obtained by using chemical stabilizers. The presence of 50-60 micrograms/ml of ascorbic acid keeps the content of 99mTc-pertechnetate below 5% during six hours even in solutions of high initial radioactive concentrations (up to about 814 MBq/ml). With this concentration of ascorbic acid, good results are obtained also by labeling inactive solutions kept at low temperatures during seven days. Genetisic acid is also efficient but its concentration should be about ten times higher. CONCLUSION: The in vitro stability of 99mTc(Sn)-pyrophosphate depends on the initial radioactive concentration of 99mTc and time after labeling. Best results were obtained when the preparation contained ascorbic acid as a chemical stabilizer. Its concentration in the range of 50-60 micrograms/ml is sufficient to keep the content of 99mTc-pertechnetate below 5% during six hours, both in freshly prepared samples and those kept at low temperatures for seven days.