Antimicrobial peptide for bacterial infection imaging: first case reported in Brazil

ABSTRACT Molecular imaging markers can be used to differentiate between infection and aseptic inflammation, determine the severity of infection, and monitor treatment responses. One of these markers is ubiquicidin(29-41) (UBI), a cationic peptide fragment that binds to the bacterial membrane wall and is labeled with gallium-68 (68Ga), a positron emitter radioisotope. The use of UBI in positron emission tomography (PET)/computed tomography (CT) for improved detection of lesions has been receiving considerable attention recently. Herein, we report the first case of 68Ga-UBI PET/CT performed in Brazil. The patient was a 39-year-old woman referred for a scan to confirm a clinical suspicion of chronic osteomyelitis of her fractured left tibia. PET images revealed radiotracer uptake near the posterior contour of the tibial fracture focus and the fixation plate, in the soft tissue around the distal half of the tibia, and in the non-consolidated fracture of the left distal fibula. Surgery for local cleaning was performed, and culture of a specimen collected from the surgical site confirmed the presence of Staphylococcus aureus. In the present case, 68Ga-UBI PET/CT, a non-invasive imaging modality, identified the infection foci in vivo, indicating its potential for clinical use.

PET/MRI: a novel hybrid imaging technique. Major clinical indications and preliminary experience in Brazil / PET/RM: um novo método de imagem híbrida. Principais indicações clínicas e experiência preliminar no Brasil

ABSTRACT In recent years, medical imaging with hybrid techniques has widely accepted and employed in clinical routine. PET/MRI offers significant advantages, including excellent contrast and resolution and reduced ionizing radiation, as compared to well-established PET/CT. Therefore, PET/MRI is a promising modality for oncologic imaging of some regions, such as brain, head and neck, liver and pelvis. This article set out to analyze clinical conditions that could benefit from PET/MRI imaging based on our caseload. The potential of PET/MRI to become the imaging modality of choice for assessment of neurologic and oncologic conditions associated with soft tissues is highlighted. Clinical aspects of PET/MRI and its application to clinical cases are illustrated with examples extracted from the authors’ preliminary experience.

RESUMO Nos últimos anos, imagens médicas com tecnologias híbridas tornaram-se amplamente aceitas e utilizadas na prática clínica. O PET/RM possui vantagens importantes, incluindo excelentes contrastes e resolução, e menor radiação ionizante, em comparação ao PET/TC. Por isto, é uma modalidade promissora para exames de imagem de pacientes oncológicos, para avaliar o cérebro, cabeça e pescoço, o fígado e a pelve. O objetivo deste artigo foi analisar as situações clínicas que se beneficiariam de exames de PET/RM a partir de uma casuística. Destacamos o potencial desta técnica se tornar o método de imagem de escolha para doenças neurológicas e oncológicas que envolvam partes moles. Os aspectos clínicos de PET/RM e sua aplicação aos casos clínicos são ilustrados com exemplos da experiência inicial dos autores.

Estudo comparativo da qualidade de imagem dos modos de aquisição da PET: validação de um protocolo para reduzir a dose de radiação / Comparative study on imaging quality in PET acquisition modes: validation of a protocol for reducing the radiation dose

OBJETIVO: O presente experimento visa a validar um protocolo de aquisição em 3D na tomografia por emissão de pósitrons, em substituição ao modo 2D, de forma a reduzir a dose de radiação nos pacientes, sem perda da qualidade de imagens. MATERIAIS E MÉTODOS: Foram realizadas 27 simulações em equipamento Discovery ST, nos modos 2D com quatro minutos de aquisição e 3D com dois e quatro minutos. Utilizou-se um simulador do protocolo da National Electrical Manufacturers Association. No interior deste simulador estão inseridas seis esferas com diferentes diâmetros para a determinação da qualidade de imagem. As aquisições foram comparadas por três médicos nucleares, sem que eles identificassem o modo de aquisição. Cada observador atribuiu o valor igual a 1 quando alguma esfera não foi identificada ou valor 2 para esferas visíveis. RESULTADOS: A análise qualitativa pelo kappa generalizado demonstrou que a frequência de esferasvisíveis foi maior no modo 3D com quatro minutos (85%) e a porcentagem de concordância também foi maior (88,9%), com kappa generalizado = 0,725 [0,507;0,942]. CONCLUSÃO: O modo 3D com quatro minutos de aquisição e com menores atividades de FDG-18F pode ser utilizado em pacientes com biótipo equivalente ao simulador, sem perda de qualidade de imagem.

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, utilizinga chest phantom according to the National Electrical Manufacturers Association protocol. Six spheres withdifferent 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.

Adaptação da técnica convencional de PET/CT para o planejamento radioterápico / Modification of conventional PET/CT technique for radiotherapy planning

A definição do volume a ser irradiado é o aspecto mais importante do planejamento radioterápico. As imagens de fusão da PET/CT permitem a visualização do tecido com aumento da atividade metabólica, o que melhora a delimitação do volume a ser tratado . A fim de reduzir os erros de fusão das imagens da PET com a TC, foram propostas algumas alterações do protocolo original que permitiram utilizar a PET/CT no planejamento radioterápico. No protocolo adaptado foi acrescentada, antes da aquisição da PET/CT, uma sequência tomográfica para visualização dos localizadores colocados no paciente durante a simulaçaõ do procedimento radioterápico e outra, logo após, com cortes mais finos, para reconstrução das imagens na estação de trabalho do planejamento radioterápico. De agosto/2004 a novembro/2005, foram realizados 88 planejamentos radioterápicos com auxílio das imagens da PET/CT. O alinhamento mecânico do eixo das duas modalidades permitiu a coincidência das imagens, reduzindo os erros de fusão em 99% dos casos, e possibilitou uma melhor avaliação da área de tratamento.

The definition of the tissue volume to be irradiated is the most important task in radiotherapy planning. A PET/CT fusion images allows the identification of the tissue with increased metabolic activity, thus enhancing the precise definition of the limits of the volume to be treated. To minimize errors that may occur by fusing the PET images with those of CT, some modifications were included to the original acquisition protocol which permitted the convenient utilization of PET/CT technique for the purposes of radiotherapy planning. The new protocol added one transmission tomographic sequence before conventional PET/CT, to check the position of the locators previously set for radiotherapy simulation, and a second multislice sequence after PET/CT for the purpose of reconstruction in the radiotherapy planning workstation. This second sequence is the one effectively used for the dosimetry plans. From August2004 through November 2005 88 radiotherapy plannings were performed at the PET/CT center according to the above described protocol. The mechanical axial alignment of the two imaging procedures thus achieved, resulted in near perfect image fusion in99% of the cases and improved the restriction of the treatment to the effective neoplasic tissue.

Experimental model in rat for sentinel node biopsy

Although sentinel node procedure has been used world wide, there are many aspects to be defined and better standardized. This study address if the experimental model in rats is appropriate for sentinel node biopsy. In this model, the lymph nodes are showed by lymphoscintigraphy, they are dyed by patent blue and identified by intraoperative gamma probe detection. It isnÆt necessary to use magnification for the procedure. The model demonstrated that sentinel node biopsy in rats is feasible. So, besides allowing researches in this field, the model is useful for training and diffusing this technique.