Solange Amorim Nogueira

SPEM: a state-of-the-art instrument for high resolution molecular imaging of small animal organs

OBJECTIVE To describe the Single Photon Emission Microscope (SPEM), a state-of-the-art instrument for small animal SPECT imaging, and characterize its performance presenting typical images of different animal organs. METHODS SPEM consists of two independent imaging devices based on high resolution scintillators, high sensitivity and resolution Electron-Multiplying CCDs and multi-pinhole collimators. During image acquisition, the mouse is placed in a rotational vertical holder between the imaging devices. Subsequently, an appropriate software tool based on the Maximum Likelihood algorithm iteratively produces the volumetric image. Radiopharmaceuticals for imaging kidneys, heart, thyroid and brain were used. The mice were injected with 74 to 148 MBq/0,3mL and scanned for 40 to 80 minutes, 30 to 60 minutes afterwards. During this procedure, the animals remained under ketamine/xilazine anesthesia. RESULTS SPEM images of different mouse organs are presented, attesting the imaging capabilities of the instrument. CONCLUSION SPEM is an innovative technology for small animal SPECT imaging providing high resolution images with appropriate sensitivity for pre-clinical research. Its use with appropriate radiotracers will allow translational investigation of several animal models of human diseases, their pharmacological treatment and the development of potential new therapeutic agents.

PET-CT as an Alternative to Fiducial Markers Guidance in Liver Metastasis Treatment

The liver is the organ most commonly affected by colorectal cancer metastasis. Currently, liver resection is the treatment of choice, but in cases where it is not possible, intensity-modulated radiation therapy is an alternative. We report the case of a 57-year-old woman whose colorectal carcinoma metastasized to the liver. She was referred for implantation of fiducial markers for intensity-modulated radiation therapy planning. PET-CT stands out as an additional tool for distinguishing metabolically active tumor tissue from other tissues, ensuring effective introduction of percutaneous fiducial markers, especially in cases where use of conventional imaging techniques is limited.

Effectiveness of 18 F-sodium fluoride positron emission tomography/computed tomography scan in the early detection of periradicular lesions

Objective: Establishing the correct diagnosis is key for the implementation of adequate therapy. The aim of this study was to analyze the sensitivity of 18 F-sodium fluoride positron emission tomography/computed tomography (PET/CT), in comparison with conventional radiographic imaging techniques (periapical/parallelism technique and panoramic radiographs), in the early detection of periradicular lesions. Materials and Methods: A total of 256 maxillary and mandibular areas from eight patients were randomly selected for analysis using conventional radiographic techniques and PET/CT. The nuclear image acquisition protocol included scans from the top of the head to the middle third of the neck region. After analysis of the images obtained with different methods (periapical vs. panoramic radiography, and radiography vs. PET/CT). The number of images with positive findings for infection were compared using ANOVA (P ≤ 0.05). Results: There were no significant differences in the number of positive images between the two conventional radiographic techniques: Six (2.34% of the sample) and seven (2.73%) positive images were found among panoramic and periapical radiographs, respectively. Conversely, PET/CT yielded 39 (15.23% of the sample) images positive for infection, significantly higher number when compared with the two conventional radiographic techniques assessed. Conclusion: Positron emission tomography/computed tomography showed to be more effective than conventional radiography in the early detection of dental infection. These findings allow to suggest that the use of PET/CT in endodontics would significantly contribute to the early and accurate diagnosis of periradicular lesions.

Estudo comparativo da qualidade de imagem dos modos de aquisição da PET: validação de um protocolo para reduzir a dose de radiação

OBJECTIVE: The present study is aimed at validating a 3D acquisition protocol for positron emission tomography as a replacement for the 2D mode, to reduce the radiation dose delivered to patients, without any loss in the quality of images. MATERIALS AND METHODS: The study comprised 27 simulations in a Discovery ST equipment with four-minute 2D acquisitions, and two-minute and four-minute 3D acquisitions, utilizing a chest phantom according to the National Electrical Manufacturers Association protocol. Six spheres with different diameters were inserted into this phantom as a means for determining the images quality. The images were blindly reviewed by three experienced nuclear physicians who did not know the acquisition modes. Each observer attributed a score 1 when one of the spheres was not identified, or 2 for visible spheres. RESULTS: The qualitative analysis based on generalized kappa coefficient demonstrated that the frequency of visible spheres was higher with four-minute 3D acquisitions (85%), with an also higher interobserver agreement (88.9%), generalized kappa = 0.725 [0.507;0.942]. CONCLUSION: The protocol with four-minute 3D acquisition with lower 18F-FDG activity can be utilized for patients with a biotype similar to the phantom, without any loss in the imaging quality.