[Preliminary application assessment of individualized three-dimensional printing titanium mesh combined with guided bone regeneration for repairing alveolar bone defects].

Objective: To preliminarily evaluate the clinical effect of the three-dimensional (3D) printing individualized titanium mesh combined with guided bone regeneration technology for repairing alveolar bone defects. Methods: Six patients with alveolar bone defects (4 males and 2 females, aged 18-27 years, mean 23.3 years) were selected from the Department of Oral Implantology, Stomatological Hospital of Chongqing Medical University from January to June 2018. The patients' cone-beam CT (CBCT) data was imported into the digital design software, and the individualized titanium meshes were designed based on the ideal bone mass around the implant, alveolar bone morphology and soft tissue condition. Then, the ".stl" files were output and the meshes were fabricated by 3D printing technology. The individualized titanium meshes combined with the mixture of autogenous bone and bone substitute materials were used to augmentation during operation. All patients were reviewed at 1, 3 and 6 months after surgery to observe the complications and evaluate the effect of bone augmentation. After taking out the titanium mesh, the CBCT was compared with the preoperative CBCT. The increased bone height and bone width were measured and the bone incremental volume was calculated. Results: Titanium mesh exposure occurred in 2 patients with no obvious infection, and no early removal. In 6 patients, the bone width increased by 1.75-7.54 mm (mean 3.58 mm), the bone height increased by 0.91-11.80 mm (mean 3.37 mm), and bone incremental volume increased by 247-676 mm(3) (mean 503 mm(3)). All of the cases showed sufficiently grafted volume for implant placement. Conclusions: The individualized 3D printing titanium meshes combined with guided bone regeneration could repair alveolar bone defects with excellent clinical effect, but a better design needed to be explored in the future to solve or delay the exposure of titanium mesh.

Performance assessment of the single photon emission microscope: high spatial resolution SPECT imaging of small animal organs.

The single photon emission microscope (SPEM) is an instrument developed to obtain high spatial resolution single photon emission computed tomography (SPECT) images of small structures inside the mouse brain. SPEM consists of two independent imaging devices, which combine a multipinhole collimator, a high-resolution, thallium-doped cesium iodide [CsI(Tl)] columnar scintillator, a demagnifying/intensifier tube, and an electron-multiplying charge-coupling device (CCD). Collimators have 300- and 450-µm diameter pinholes on tungsten slabs, in hexagonal arrays of 19 and 7 holes. Projection data are acquired in a photon-counting strategy, where CCD frames are stored at 50 frames per second, with a radius of rotation of 35 mm and magnification factor of one. The image reconstruction software tool is based on the maximum likelihood algorithm. Our aim was to evaluate the spatial resolution and sensitivity attainable with the seven-pinhole imaging device, together with the linearity for quantification on the tomographic images, and to test the instrument in obtaining tomographic images of different mouse organs. A spatial resolution better than 500 µm and a sensitivity of 21.6 counts·s-1·MBq-1 were reached, as well as a correlation coefficient between activity and intensity better than 0.99, when imaging 99mTc sources. Images of the thyroid, heart, lungs, and bones of mice were registered using 99mTc-labeled radiopharmaceuticals in times appropriate for routine preclinical experimentation of <1 h per projection data set. Detailed experimental protocols and images of the aforementioned organs are shown. We plan to extend the instrument's field of view to fix larger animals and to combine data from both detectors to reduce the acquisition time or applied activity.

Performance assessment of the single photon emission microscope: high spatial resolution SPECT imaging of small animal organs

The single photon emission microscope (SPEM) is an instrument developed to obtain high spatial resolution single photon emission computed tomography (SPECT) images of small structures inside the mouse brain. SPEM consists of two independent imaging devices, which combine a multipinhole collimator, a high-resolution, thallium-doped cesium iodide [CsI(Tl)] columnar scintillator, a demagnifying/intensifier tube, and an electron-multiplying charge-coupling device (CCD). Collimators have 300- and 450-µm diameter pinholes on tungsten slabs, in hexagonal arrays of 19 and 7 holes. Projection data are acquired in a photon-counting strategy, where CCD frames are stored at 50 frames per second, with a radius of rotation of 35 mm and magnification factor of one. The image reconstruction software tool is based on the maximum likelihood algorithm. Our aim was to evaluate the spatial resolution and sensitivity attainable with the seven-pinhole imaging device, together with the linearity for quantification on the tomographic images, and to test the instrument in obtaining tomographic images of different mouse organs. A spatial resolution better than 500 µm and a sensitivity of 21.6 counts·s-1·MBq-1 were reached, as well as a correlation coefficient between activity and intensity better than 0.99, when imaging 99mTc sources. Images of the thyroid, heart, lungs, and bones of mice were registered using 99mTc-labeled radiopharmaceuticals in times appropriate for routine preclinical experimentation of <1 h per projection data set. Detailed experimental protocols and images of the aforementioned organs are shown. We plan to extend the instrument's field of view to fix larger animals and to combine data from both detectors to reduce the acquisition time or applied activity.