RESUMO
PURPOSE: In vivo quantification of radiopharmaceuticals has great potential as a tool in developing new drugs. We investigated the accuracy of in vivo quantification with multi-pinhole single-photon emission computed tomography (SPECT) in rats. METHODS: Fifteen male Lewis rats with different stages of renal dysfunction were injected with 50 MBq 99mTc-dimercaptosuccinic acid. Four to six hours after injection, SPECT of the kidneys was acquired with a new four-headed multi-pinhole collimator camera. Immediately after imaging the rats were sacrificed and the kidneys were counted in a gamma-counter to determine the absorbed activity. SPECT data were reconstructed iteratively and regions of interest (ROIs) were drawn manually. The absolute activity in the ROIs was determined. RESULTS: Uptake values ranging from 0.71% to 21.87% of the injected activity were measured. A very strong linear correlation was found between the determined activity in vivo and ex vivo (r2=0.946; slope m=1.059). CONCLUSION: Quantification in vivo using this multi-pinhole SPECT system is highly accurate.
Assuntos
Renografia por Radioisótopo/instrumentação , Renografia por Radioisótopo/veterinária , Ácido Dimercaptossuccínico Tecnécio Tc 99m/farmacocinética , Tomografia Computadorizada de Emissão de Fóton Único/instrumentação , Tomografia Computadorizada de Emissão de Fóton Único/veterinária , Animais , Desenho de Equipamento , Análise de Falha de Equipamento , Aumento da Imagem/instrumentação , Aumento da Imagem/métodos , Testes de Função Renal/instrumentação , Testes de Função Renal/métodos , Testes de Função Renal/veterinária , Masculino , Renografia por Radioisótopo/métodos , Compostos Radiofarmacêuticos/análise , Compostos Radiofarmacêuticos/farmacocinética , Ratos , Ratos Endogâmicos Lew , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Ácido Dimercaptossuccínico Tecnécio Tc 99m/análise , Tomografia Computadorizada de Emissão de Fóton Único/métodosRESUMO
OBJECTIVE: To image inflammatory arthritic lesions in experimental arthritis and in patients with arthritis, using a newly developed high-resolution multipinhole single-photon-emission computed tomography (MPH-SPECT) technique. METHODS: Six interleukin-1 receptor antagonist-deficient mice with arthritis of the front and back paws and 2 control BALB/c mice were imaged with MPH-SPECT and scored macroscopically for arthritis. SPECT imaging was performed with a conventional gamma camera upgraded with a pyramidal lead collimator affixed with MPH apertures. All images were reconstructed, and uptake in the paws was quantified in counts/weight and injected activity. To transfer the imaging technique to humans we examined the clinically dominant hand of 6 individuals (3 with established rheumatoid arthritis [RA], 1 with early RA, 1 with osteoarthritis, and 1 healthy control). RESULTS: MPH-SPECT images were high-resolution 3-dimensional tomographic images, which allowed exact localization and quantifiable observation of increased bone metabolism. MPH-SPECT counts of inflamed joints in mice correlated with macroscopic scoring and histologic joint analysis postmortem. In humans, MPH-SPECT images depicted a detailed visualization of tracer accumulation in bony structures of hand and finger joints, and were also capable of imaging increased bone metabolism that had appeared normal with other imaging modalities, e.g., magnetic resonance imaging. CONCLUSION: The MPH-SPECT technique represents a new diagnostic tool in the detection of bone pathology in small-animal arthritis research. Compared with macroscopic scoring, this new method provides a more objective and higher-precision quantifiable measurement of bone reaction, allowing visualization of inflammatory processes of the whole skeleton in vivo. These results suggest that MPH-SPECT may be useful as a diagnostic instrument for monitoring experimental arthritis, with further potential for use in human studies of RA.