CT "halo sign" in pulmonary tuberculoma.

The CT halo sign has been described as the CT finding of a low-attenuation zone surrounding a pulmonary nodule. It is an early clue to the diagnosis of invasive pulmonary aspergillosis. We describe a case of CT halo sign associated with a pulmonary tuberculoma. Therefore, we think that a diagnosis other than invasive pulmonary aspergillosis should be considered in the presence of the CT halo sign in immunocompetent patients.

[Contrast-enhanced study of solitary pulmonary nodules with thin-section computed tomography]. / Lo studio contrastografico dei noduli polmonari solitari con Tomografia Computerizzata con strato sottile.

INTRODUCTION: Since many benign and malignant pathologic conditions can appear as solitary pulmonary nodules, to establish nodule nature is always necessary for correct patient management. Recently, some authors have demonstrated the effectiveness of incremental dynamic CT in distinguishing cancerous from noncancerous lesions. The purpose of this work is to report our personal experience in this field. MATERIAL AND METHODS: We reviewed the incremental dynamic CT scans of 21 patients with a solitary pulmonary nodule < 3.5 cm phi without any calcifications, cavities and fat--namely, 15 carcinomas, 3 granulomas, 2 hamartomas, 1 abscess. Lesion density was evaluated before and 30 s, 1, 2, 3 and 5 min after contrast agent administration; we used a circular region of interest consisting of the central portion of the nodule in all cases and of 60-70% of its area in most cases. We subdivided the nodules into two groups, according to their enhancement: the nodules with > 20 HU and those with < 20 HU. All the lesions were submitted to surgery and histologic studies. RESULTS: Fourteen of 15 carcinomas and one hamartoma had contrast enhancement > 20 HU; an abscess exhibited marked ring-shaped contrast enhancement (positive predictive value: 87%). One carcinoma, three granulomas and one hamartoma had no contrast enhancement, or else it was < 20 HU (negative predictive value: 80%). DISCUSSION: Recently, some authors have demonstrated that malignant nodules, studied with incremental dynamic CT, have higher contrast enhancement than benign nodules. A value > 20 HU is a good predictor of malignancy (positive predictive value: 90%) and, conversely, a value < 20 HU is an unquestionable sign of benignity (negative predictive value: 100%). Our findings confirm the positive predictive value of enhancement > 20 HU, but not its negative predictive value because we found a malignant nodule without contrast enhancement. CONCLUSIONS: Incremental dynamic CT is an effective indicator of solitary pulmonary nodule nature, but its predictive value is not absolute and therefore this technique should be integrated with biopsy in the cases which are clinically or radiologically suspicious.

[The enhancement phenomenon of serous cavity effusions]. / Il fenomeno dell'enhancement dei versamenti delle cavità sierose.

The enhancement of ascites following a high dose of contrast medium has been recently described. The CT behavior of 26 peritoneal, pleural or pericardial effusions has been studied in 23 patients after the administration of a high dose of urographic contrast medium. The effusions were enhanced in all patients but one. No difference between malignant and non-malignant effusions could be observed with ionic and non-ionic contrast medium. Low molecular weight of the urographic contrast medium (600-800 daltons) can explain the free passage of the solute through peritoneum, pleura, and pericardium. The knowledge of such a phenomenon is mandatory to avoid misdiagnosing hematic effusion or urinary-peritoneal fistula.

[Computed tomography in endobronchial mucus accumulation]. / La tomografia computerizzata nella malattia da accumulo endobronchiale di muco.

To investigate the value of CT in depicting endobronchial mucoid collections, the authors retrospectively reviewed the CT scans of 22 patients, 14 with mucous plugs, 7 with mucoid pseudotumors, and one with a bronchocele due to bronchial atresia. Atelectasis could be seen in 11 of 14 patients with mucous plugs. In 12 of 14 patients with mucous plugs CT showed the involved bronchi filled by fluid representing abnormal mucus accumulation. In the patients with atelectasis CT showed mucus-filled bronchi as low-attenuation branching structures (mucoid bronchogram). All the mucoid pseudotumors appeared as low-attenuation (< 20 HU) polypoid wall lesions with no involvement of the bronchial walls. In a patient with bronchial atresia CT showed a solitary pulmonary nodule (representing the obstructed and dilated bronchus filled by mucus) surrounded by peripheral pulmonary hyperinflation. Characteristically, the endobronchial mucoid collections never enhanced after bolus contrast medium. Endobronchial mucoid collections had to be differentiated from endobronchial neoplasms. In some cases bronchoscopy was necessary to make the differential diagnosis. In conclusion, CT is a valuable tool with good sensitivity and specificity in diagnosing endobronchial mucoid collections.