[Radiological diagnostics of Hodgkin- and non-Hodgkin lymphomas of the thorax]

Diagnostic value of software-based image fusion of computed tomography and F18-FDG PET scans in patients with malignant lymphoma

AIM

The purpose of this study was to evaluate the accuracy of 2-deoxy-2-[fluorine-18]fluoro-D-glucose (FDG) positron emission tomography (PET), computed tomography (CT), and software-based image fusion of both modalities in the imaging of non-Hodgkin's lymphoma (NHL) and Hodgkin's disease (HD).

METHODS

77 patients with NHL (n = 58) or HD (n = 19) underwent a FDG PET scan, a contrast-enhanced CT, and a subsequent digital image fusion during initial staging or followup. 109 examinations of each modality were evaluated and compared to each other. Conventional staging procedures, other imaging techniques, laboratory screening, and follow-up data constituted the reference standard for comparison with image fusion. Sensitivity and specificity were calculated for CT and PET separately.

RESULTS

Sensitivity and specificity for detecting malignant lymphoma were 90% and 76% for CT and 94% and 91% for PET, respectively. A lymph node region-based analysis (comprising 14 defined anatomical regions) revealed a sensitivity of 81% and a specificity of 97% for CT and 96% and 99% for FDG PET, respectively. Only three of 109 image fusion findings needed further evaluation (false positive).

CONCLUSION

Digital fusion of PET and CT improves the accuracy of staging, restaging, and therapy monitoring in patients with malignant lymphoma and may reduce the need for invasive diagnostic procedures.

[Computerized tomography of mediastinal tumors]

Tumors of the mediastinum represent a very heterogeneous group of primary and metastatic tumors. Most tumors of the mediastinum are detected on chest radiography, but for more precise view additional imaging methods are necessary. The most common causes of tumor mass in anterior mediastinum are thymoma, germ cell tumors, retrosternal goitre and Hodgkin's lymphoma. In the middle mediastinum most commonly tumors are congenital cysts, such as bronhogenic and pericardial cysts, and enlarged lymph nodes, while in the posterior mediastinum dominantly present neurogenic tumors. Complex anatomy of mediastinum infrequently makes difficulties in radiological diagnosis of these tumors. Computerized tomography (CT) is a radiological method of choice in the diagnosis of primary and/or secondary mediastinal lesions. Localization and structure of the tumor masses are very important for diagnosis. Knowledge of anatomy, with the standard topographic divisions on the anterior, middle and posterior mediastinum is necessary prerequisite for a valid CT diagnostic. Lesions in all parts of the mediastinum are systematically presented from the aspect of practical recommendations, with a view of the typical pathological findings.