Abstract
This study aimed to report the first single-photon emission computed tomographic (SPECT) imaging of articular cartilage in mice using 99mTc-NTP 15-5 radiotracer. Mice intravenously injected with 99mTc-NTP 15-5 were submitted to (1) dynamic planar imaging, (2) static planar imaging, (3) 1 mm pinhole SPECT acquisition, and (4) dissection. Tomographic reconstruction of SPECT data was performed with a three-dimensional ordered subset expectation maximization algorithm, and slices were reconstructed in three axes. 99mTc-NTP 15-5 rapidly accumulated in the joint, with a peak of radioactivity being reached from 5 minutes postinjection and maintained for at least 90 minutes. Given that bone and muscle did not show any accumulation of the tracer, highly contrasted joint imaging was obtained from 15 minutes postinjection. When 1 mm pinhole SPECT acquisition was focused on the knee, the medial and lateral compartments of both the femoral condyle and tibial plateau were highly delineated, allowing a separate quantitation of tracer accumulation within each component of the femorotibial joint. A good correlation was found between tracer uptake determined by region of interest analysis of both planar and SPECT scans and dissection. This new approach to imaging of cartilage in mice provides joint functionality assessment in vivo, giving a unique opportunity to achieve a greater understanding of cartilage physiology in health and disease.
Highlights
This study aimed to report the first single-photon emission computed tomographic (SPECT) imaging of articular cartilage in mice using 99mTc-NTP 15-5 radiotracer
This article is the first to report SPECT imaging of articular cartilage in mice in vivo, providing a unique opportunity to achieve a greater understanding of cartilage physiology in health and disease
dynamic planar imaging (DPI) and tissue counting: As expected from previous animal studies, the peak of radioactivity was reached within the articular cartilage of the mouse knee from 5 minutes postinjection and was maintained for at least 90 minutes postinjection.[18,19]
Summary
This study aimed to report the first single-photon emission computed tomographic (SPECT) imaging of articular cartilage in mice using 99mTc-NTP 15-5 radiotracer. A good correlation was found between tracer uptake determined by region of interest analysis of both planar and SPECT scans and dissection This new approach to imaging of cartilage in mice provides joint functionality assessment in vivo, giving a unique opportunity to achieve a greater understanding of cartilage physiology in health and disease. The vectorization toward cartilage matrix PGs is the strategy developed by and used in our group for many years This strategy consists of using the quaternary ammonium function (that exhibits a high affinity for PG) as a selective carrier of oxotechnetium complex to cartilaginous tissues.[16,17,18] Technetium-99m N-[3-(triethylammonio)propyl]-15ane-N5 (99mTc-NTP 15-5) scintigraphic imaging was recently demonstrated to show a high sensitivity to enable accurate assessment of articular functionality in cartilage PG in two experimental OA models with markedly different etiopathologic factors.[18,19] On the basis of these encouraging results, we hypothesized that 99mTcNTP 15-5 scintigraphic imaging would be a powerful tool to assess cartilage functionality in vivo in small animals, which has great potential for OA research. This article is the first to report SPECT imaging of articular cartilage in mice in vivo, providing a unique opportunity to achieve a greater understanding of cartilage physiology in health and disease
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