Valor da PET/CT na abordagem do câncer de cabeça e pescoço

OBJETIVO: Avaliar a PET/CT na abordagem de pacientes com câncer de cabeça e pescoço. MATERIAIS E MÉTODOS: Estudo retrospectivo de 63 prontuários e exames de PET/CT de pacientes com câncer de cabeça e pescoço. RESULTADOS: Foram encontradas alterações em 76% dos exames. Destes, 7 (11%) foram considerados falso-positivos, com SUV < 5,0. A PET/CT mostrou-se negativa em 15 situações (24%). Dos 14 casos nos quais se utilizou o exame para estadiamento, em 3 (22%) houve aumento no estadiamento. CONCLUSÃO: A PET/CT mostra-se como exame de potencial valor na rotina de avaliação de pacientes com câncer de cabeça e pescoço, entretanto, necessitamos de maior número de casos para definirmos protocolo de uso.

Endobronchial valves in severe emphysematous patients: CT evaluation of lung fissures completeness, treatment radiological response and quantitative emphysema analysis

OBJECTIVE: To evaluate lung fissures completeness, post-treatment radiological response and quantitative CT analysis (QCTA) in a population of severe emphysematous patients submitted to endobronchial valves (EBV) implantation. MATERIALS AND METHODS: Multi-detectors CT exams of 29 patients were studied, using thin-section low dose protocol without contrast. Two radiologists retrospectively reviewed all images in consensus; fissures completeness was estimated in 5% increments and post-EBV radiological response (target lobe atelectasis/volume loss) was evaluated. QCTA was performed in pre and post-treatment scans using a fully automated software. RESULTS: CT response was present in 16/29 patients. In the negative CT response group, all 13 patients presented incomplete fissures, and mean oblique fissures completeness was 72.8%, against 88.3% in the other group. QCTA most significant results showed a reduced post-treatment total lung volume (LV) (mean 542 ml), reduced EBV-submitted LV (700 ml) and reduced emphysema volume (331.4 ml) in the positive response group, which also showed improved functional tests. CONCLUSION: EBV benefit is most likely in patients who have complete interlobar fissures and develop lobar atelectasis. In patients with no radiological response we observed a higher prevalence of incomplete fissures and a greater degree of incompleteness. The fully automated QCTA detected the post-treatment alterations, especially in the treated lung analysis.

Correlation between PET/CT results and histological and immunohistochemical findings in breast carcinomas

Objective To correlate the results of 18F-fluoro-2-deoxy-D-glucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) performed with a specific protocol for assessment of breasts with histological/immunohistochemical findings in breast carcinoma patients. Materials and Methods Cross-sectional study with prospective data collection, where patients with biopsy-confirmed breast carcinomas were studied. The patients underwent PET/CT examination in prone position, with a specific protocol for assessment of breasts. PET/CT findings were compared with histological and immunohistochemical data. Results The authors identified 59 malignant breast lesions in 50 patients. The maximum diameter of the lesions ranged from 6 to 80 mm (mean: 32.2 mm). Invasive ductal carcinoma was the most common histological type (n = 47; 79.7%). At PET/CT, 53 (89.8%) of the lesions demonstrated anomalous concentrations of 18F-FDG, with maximum SUV ranging from 0.8 to 23.1 (mean: 5.5). A statistically significant association was observed between higher values of maximum SUV and histological type, histological grade, molecular subtype, tumor diameter, mitotic index and Ki-67 expression. Conclusion PET/CT performed with specific protocol for assessment of breasts has demonstrated good sensitivity and was associated with relevant histological/immunohistochemical factors related to aggressiveness and prognosis of breast carcinomas.

Dosimetria de pacientes submetidos a exames de PET/CT cerebral para diagnóstico de comprometimento cognitivo leve

Objetivo: O objetivo deste trabalho é avaliar a dose em pacientes submetidos a PET/CT para diagnóstico de comprometimento cognitivo leve. Materiais e Métodos: Para as medidas da dose absorvida proveniente da modalidade CT utilizaram-se detectores TLD-100 inseridos em um simulador Alderson Rando®. Os simuladores antropomórficos (versões masculina e feminina) foram submetidos aos mesmos protocolos técnicos para aquisição das imagens dos pacientes. A dose absorvida resultante da injeção do radiofármaco foi estimada por meio do modelo proposto pela ICRP 106. Resultados: A dose efetiva a que foram submetidos os pacientes com esta técnica diagnóstica foi, aproximadamente, (5,34 ± 1,99) mSv. Conclusão: Protocolos otimizados para cálculo de atividade radioativa que será injetada em cada paciente podem contribuir para a redução da dose efetiva nos pacientes durante a realização do diagnóstico de comprometimento cognitivo leve com PET/CT.

Comparison of standardized uptake values measured on 18F-NaF PET/CT scans using three different tube current intensities

Objective: To analyze standardized uptake values (SUVs) using three different tube current intensities for attenuation correction on 18FNaF PET/CT scans. Materials and Methods: A total of 254 18F-NaF PET/CT studies were analyzed using 10, 20 and 30 mAs. The SUVs were calculated in volumes of interest (VOIs) drawn on three skeletal regions, namely, right proximal humeral diaphysis (RH), right proximal femoral diaphysis (RF), and first lumbar vertebra (LV1) in a total of 712 VOIs. The analyses covered 675 regions classified as normal (236 RH, 232 RF, and 207 LV1). Results: Mean SUV for each skeletal region was 3.8, 5.4 and 14.4 for RH, RF, and LV1, respectively. As the studies were grouped according to mAs value, the mean SUV values were 3.8, 3.9 and 3.7 for 10, 20 and 30 mAs, respectively, in the RH region; 5.4, 5.5 and 5.4 for 10, 20 and 30 mAs, respectively, in the RF region; 13.8, 14.9 and 14.5 for 10, 20 and 30 mAs, respectively, in the LV1 region. Conclusion: The three tube current values yielded similar results for SUV calculation.

Ambient radiation levels in positron emission tomography/computed tomography (PET/CT) imaging center

Objective: To evaluate the level of ambient radiation in a PET/CT center. Materials and Methods: Previously selected and calibrated TLD-100H thermoluminescent dosimeters were utilized to measure room radiation levels. During 32 days, the detectors were placed in several strategically selected points inside the PET/CT center and in adjacent buildings. After the exposure period the dosimeters were collected and processed to determine the radiation level. Results: In none of the points selected for measurements the values exceeded the radiation dose threshold for controlled area (5 mSv/year) or free area (0.5 mSv/year) as recommended by the Brazilian regulations. Conclusion: In the present study the authors demonstrated that the whole shielding system is appropriate and, consequently, the workers are exposed to doses below the threshold established by Brazilian standards, provided the radiation protection standards are followed.

Prevalence of exclusive lower extremity metastases at 18F-NaF PET/CT

AbstractObjective:To evaluate the prevalence of exclusive lower extremity metastases, specifically in the femur and below the knee, observed at 18F-NaF PET/CT.Materials and Methods:One thousand consecutive PET/CT studies were retrospectively evaluated for the presence of exclusive uptake in lower extremities suggesting metastatic involvement. The presumptive diagnoses based on such uptakes were subsequently obtained by evaluation of other imaging studies.Results:No exclusive uptake suggestive of metastasis below the femur was observed in the present series. Exclusive uptake was observed in the proximal femur with a presumptive diagnosis of metastasis in two patients.Conclusion:The prevalence of exclusive metastasis below the femur is low and scanning from head to knees is appropriate in most cases.

The importance of PET/CT in the evaluation of patients with Ewing tumors

AbstractThe effective evaluation for the treatment of patients with Ewing tumors depends on the accuracy in the determination of the primary tumor extent and the presence of metastatic disease. Currently, no universally accepted staging system is available to assess Ewing tumors. The present study aimed at discussing the use of PET/CT as a tool for staging, restaging and assessment of therapeutic response in patients with Ewing tumors. In spite of some limitations of PET/CT as compared with anatomical imaging methods, its relevance in the assessment of these patients is related to the capacity of the method to provide further physiological information, which often generates important clinical implications. Currently, the assessment of patients with Ewing tumor should comprise a study with PET/CT combined with other anatomical imaging modalities, such as radiography, computed tomography and magnetic resonance imaging.

Readjustment of abdominal computed tomography protocols in a university hospital: impact on radiation dose

AbstractObjective:To assess the reduction of estimated radiation dose in abdominal computed tomography following the implementation of new scan protocols on the basis of clinical suspicion and of adjusted images acquisition parameters.Materials and Methods:Retrospective and prospective review of reports on radiation dose from abdominal CT scans performed three months before (group A – 551 studies) and three months after (group B – 788 studies) implementation of new scan protocols proposed as a function of clinical indications. Also, the images acquisition parameters were adjusted to reduce the radiation dose at each scan phase. The groups were compared for mean number of acquisition phases, mean CTDIvol per phase, mean DLP per phase, and mean DLP per scan.Results:A significant reduction was observed for group B as regards all the analyzed aspects, as follows: 33.9%, 25.0%, 27.0% and 52.5%, respectively for number of acquisition phases, CTDIvol per phase, DLP per phase and DLP per scan (p < 0.001).Conclusion:The rational use of abdominal computed tomography scan phases based on the clinical suspicion in conjunction with the adjusted images acquisition parameters allows for a 50% reduction in the radiation dose from abdominal computed tomography scans.

Ultrasound scan as a potential source of nosocomial and cross-infection: a literature review

AbstractThe authors review the main concepts regarding the importance of cleaning/disinfection of ultrasonography probes, aiming a better comprehension by practitioners and thus enabling strategies to establish a safe practice without compromising the quality of the examination and the operator productivity. In the context of biosafety, it is imperative to assume that contact with blood or body fluids represents a potential source of infection. Thus, in order to implement cleaning/disinfection practice, it is necessary to understand the principles of infection control, to consider the cost/benefit ratio of the measures to be implemented, and most importantly, to comprehend that such measures will not only benefit the health professional and the patient, but the society as a whole.

Receiver operating characteristic (ROC) curve for classification of18F-NaF uptake on PET/CT

Abstract Objective: To assess the cutoff values established by ROC curves to classify18F-NaF uptake as normal or malignant. Materials and Methods: PET/CT images were acquired 1 hour after administration of 185 MBq of18F-NaF. Volumes of interest (VOIs) were drawn on three regions of the skeleton as follows: proximal right humerus diaphysis (HD), proximal right femoral diaphysis (FD) and first vertebral body (VB1), in a total of 254 patients, totalling 762 VOIs. The uptake in the VOIs was classified as normal or malignant on the basis of the radiopharmaceutical distribution pattern and of the CT images. A total of 675 volumes were classified as normal and 52 were classified as malignant. Thirty-five VOIs classified as indeterminate or nonmalignant lesions were excluded from analysis. The standardized uptake value (SUV) measured on the VOIs were plotted on an ROC curve for each one of the three regions. The area under the ROC (AUC) as well as the best cutoff SUVs to classify the VOIs were calculated. The best cutoff values were established as the ones with higher result of the sum of sensitivity and specificity. Results: The AUCs were 0.933, 0.889 and 0.975 for UD, FD and VB1, respectively. The best SUV cutoffs were 9.0 (sensitivity: 73%; specificity: 99%), 8.4 (sensitivity: 79%; specificity: 94%) and 21.0 (sensitivity: 93%; specificity: 95%) for UD, FD and VB1, respectively. Conclusion: The best cutoff value varies according to bone region of analysis and it is not possible to establish one value for the whole body.