PET-CT in presurgical lymph node staging in non-small cell lung cancer: the importance of false-negative and false-positive findings. / La PET-TC en la estadificación ganglionar prequirúrgica del carcinoma de pulmón de células no pequeñas: implicación de los falsos negativos y falsos positivos.

OBJECTIVE: To assess the importance of false-negative and false-positive findings in computed tomography (CT) and 18F-FDG positron emission tomography (PET) in mediastinal lymph node staging in patients undergoing surgery for non-small cell lung cancer (NSCLC). MATERIAL AND METHODS: This retrospective study included 113 consecutive patients and 120 resected NSCLCs; 22 patients received neoadjuvant treatment. We compared the findings on preoperative 18F-FDG PET-CT studies with the postoperative pathology findings. Lymph node size and primary tumor size were measured with CT, and lymph nodes and primary tumors were evaluated qualitatively and semiquantitatively (using standardized uptake values (SUVmax)) with PET. RESULTS: Metastatic lymph nodes were found in 26 (21.7%) of the 120 tumors and in 41 (7.7%) of the 528 lymph node stations analyzed. 18F-FDG PET-CT yielded 53.8% sensitivity, 76.6% specificity, 38.9% positive predictive value, 85.7% negative predictive value, and 71.7% diagnostic accuracy. The false-negative rate was 14.2%. Multivariable analysis found that the factors associated with false-negative findings were a moderate degree of differentiation in the primary tumor (p = 0.005) and an SUVmax of the primary tumor >4 (p = 0.027). The false-positive rate was 61.1%, and the multivariable analysis found that lymph node size >1cm was associated with false-positive findings (p < 0.001). CONCLUSIONS: In mediastinal lymph node staging in patients with NSCLC, 18F-FDG PET-CT improves the specificity and negative predictive value and helps clinicians to select the patients that will benefit from surgery. Given the high rate of false positives, histological confirmation of positive cases is recommendable.

Left ventricular pseudothrombus: multimodality imaging rules out a "ghost image" of a thrombus seen on cardiac computed tomography. / Pseudotrombo en ventrículo izquierdo. "Imagen fantasma" en tomografía axial computarizada. Diagnóstico multimodalidad.

Cardiac computed tomography showed a hypodense area in the apex of the left ventricle in a 57-year-old man with a history of anterior myocardial infarction three years earlier. To confirm or rule out a suspected thrombus, he underwent gadolinium-enhanced cardiac magnetic resonance imaging, contrast-enhanced two-dimensional transthoracic echocardiography, and three-dimensional transthoracic echocardiography. Multimodality imaging ruled out the presence of a thrombus.

PET/MRI: A luxury or a necessity? / PET/RM: ¿un lujo o una necesidad?

PET/MRI is a new multimodality technique with a promising future in diagnostic imaging. Technical limitations are being overcome. Interference between the two systems (PET and MRI) seems to have been resolved. MRI-based PET attenuation correction can be performed safely. Scan time is acceptable and the study is tolerable, with claustrophobia prevalence similar to that of MRI. Quantification with common parameters, such as Standardized Uptake Value (SUV), shows a fairly good correlation between both systems. However, PET/CT currently provides better results in scan time, scan costs, and patient comfort. Less patient radiation exposure is a big advantage of PET/MRI over PET/CT, which makes it particularly recommended in paediatric and adolescent patients requiring one or more studies. PET/MRI indications are the same as those of PET/CT, given that in cases where MRI is superior to CT, PET/MRI is superior to PET/CT. This superiority is clear in many soft tissue tumours. Moreover, it is common to perform both PET/CT and MRI in neurological diseases, as well as in some tumours, such as breast cancer. A single PET/MRI study replaces both with obvious benefit. MRI also allows other MRI-based PET corrections, such as motion or partial volume effect corrections. The better spatial resolution of MRI allows the transfer of well-defined MRI areas or small volumes of interest to PET image, in order to measure PET biomarkers in these areas. The richness of information of both techniques opens up immense possibilities of synergistic correlation between them.