Radiologic Assessment of Mesothelioma X Ray
Imaging plays an essential role in the diagnosis, staging, and clinical management of patients with mesothelioma X ray imaging techniques [chest radiography and computed tomography (CT)], magnetic resonance imaging (MRI), and positron emission tomography (PET) have all been used to evaluate this disease, although the relative importance of these imaging modalities has changed over time. Our understanding of mesothelioma has been advanced through radiologic examination, and nearly every mesothelioma patient makes numerous trips to the radiology department during the course of treatment.
Imaging studies define the morphology and extent of mesothelioma, tumor perfusion, tumor physiology, the presence of mediastinal or chest wall involvement, and the presence of concomitant disease. The image acquisition device (i.e., the hardware) is only one component of the radiologic examination; software tools for the subsequent visualization and postprocessing of the acquired image data are required to extract useful information from the image pixels and to fully exploit the wealth of information contained within the image. This chapter describes the imaging modalities that have been employed for the evaluation of mesothelioma and emphasizes the role of CT in the important task of tumor thickness measurement for the assessment of tumor progression or response to therapy.
Imaging Modalities Mesothelioma X Ray
Chest radiography continues to rank as the most common radiologic procedure performed in the United States. Consequently, initial detection of mesothelioma in a patient is likely to result from a radiographic
chest examination. The two-dimensional radiographic projection of mesothelioma with its complex three-dimensional morphology, however, provides neither a sensitive nor a specific diagnosis, and a
follow-up study with another imaging modality is almost always indicated. The ability to diagnose mesothelioma on chest radiography usually occurs at later, more advanced stages of the disease when tumor burden is greater.
Initial radiographic signs of mesothelioma include a unilateral pleural abnormality with an associated ipsilateral pleural effusion, ipsilateral shift of the mediastinum, and unilateral lung volume loss due to encasement of the lung by the tumor (1) (Fig. 28.1).
Signs of other asbestos-related disease are usually absent, and the typical finding of diffuse lobulated pleural thickening is indistinguishable from pleural metastases (2,3). At later stages of the disease, radiography may demonstrate thickening of interlobular septa, rib or vertebral body destruction, lymph node metastases, and metastatic pulmonary nodules (4).
Contralateral pleural abnormalities, when present, are typically the result of benign asbestos-related disease rather than metastases (5), since mesothelioma generally spreads by contiguous growth; nevertheless, hematogenous spread of mesothelioma may be observed on imaging studies (see Fig. 28.4) and was present in 44 of 66 autopsy cases in one series (6). Radiography plays a role in the posttherapy follow-up of patients. For example, patients who undergo extrapleural pneumonectomy may be monitored for complications and recurrence with chest radiography once the affected hemithorax has opacified (5).
Findings such as mediastinal shift, a new air–fluid level in the affected hemithorax, or nodules in the contralateral lung would indicate that a CT scan is warranted to differentiate between recurrent disease, infection, or a postsurgery complication (5) (Fig. 28.2). More often, however, CT is being used as the sole imaging modality for routine posttherapy follow-up.
Computed Tomography (CT SCAN) Mesothelioma X Ray
The imaging modality with the greatest impact on the current evaluation of mesothelioma x ray is CT. The transaxial images generated by CT overcome the superposition of anatomic and pathologic structures that limits the two-dimensional projection images acquired by radiography. Accordingly, the spatial extent and radiologic characteristics of mesothelioma tumor may be more clearly appreciated with CT.
The radiologic manifestation of pleural response to a variety of diseases falls into three broad categories: pleural effusion, pleural thickening, and pleural calcification (7). Computed tomography is especially capable of demonstrating such pleural responses. The particular CT findings of mesothelioma, however, are not pathognomonic; a variety of benign and malignant diseases (including metastatic disease, tuberculous pleurisy, empyema, and asbestos-related advanced pleural abnormalities) can have similar characteristics on CT (8,9).
On CT, mesothelioma is characterized by a circumferential, lobulated soft tissue mass that often involves the interlobar fissures and the mediastinal pleura of a hemithorax (2) (Fig. 28.3); bilateral disease is rare(10). Pleural effusions (see Figs. 28.11 and 28.13A below) and nodular pleural thickening, especially in the lower thoracic zone, are typical CT
findings in mesothelioma patients (5,10). A tendency for right-sided
disease has been observed (10).
Intravenous iodinated contrast administered intravenously is typically used to identify mediastinal lymph
node enlargement and to determine the relation of lesions to adjacent vascular structures (10); a recognized shortcoming of CT, however, is
its limited sensitivity for hilar lymph node involvement (10). Although pleural plaques are a common CT finding in mesothelioma, this reflects the role of asbestos exposure in the pathogenesis of both lesions; the possible preneoplastic nature of such plaques has not been proven (11,12).
In a series of 50 patients, Ng et al (13) observed that 76% of the initial CT scans demonstrated pleural effusions, of which the majority were considered “small” (i.e., they occupied less than one third of the hemithorax). Pleural thickening was observed in 94% of cases, of which 72% was nodular, 50% showed a lower zone predominance, and 47% exceeded 1 cm (13).
Superior mediastinal pleural thickening was observed in 70% of cases, diaphragmatic crural thickening was demonstrated in 84% of cases, and thickening of the pleural surfaces of the interlobar fissures was present in 84% of cases (13). Kawashima and Libshitz (14) report similar findings. In their series of CT scans from 50 mesothelioma patients, 74% of cases demonstrated pleural effusions (of which approximately half occupied less than one third of the hemithorax), 86% of cases demonstrated thickening of the pleural surfaces of the interlobar fissures, and pleural thickening of various extent, thickness, and nodularity was observed in 92% of cases. Focal pleural masses (ranging from 7 to 18 cm in maximum diameter) were observed in 8% of cases; half of these cases demonstrated chest wall invasion (14) (Fig. 28.2).
Use of MRI in Mesothelioma X Ray
MRI exams complement CT scanning in some patients, providing better delineation of soft tissues and allowing imaging in the sagittal and coronal planes. MRI scans also enable better detection of mesothelioma metastasis, whereas CT scans are more likely to miss metastasis, Yendamuri said. MRI tests are also suitable for patients who cannot tolerate the contrast dyes used during CT scans. CT scans and MRI tests do not provide an unequivocal diagnosis of mesothelioma, so tissue biopsy is required for definitive diagnosis.
Common MRI findings include:
- Solitary foci of chest wall invasion, endothoracic fascial involvement, and diaphragmatic invasion.
- Iso-intense T1 signals of chest wall musculature
- Moderate increased signals on T2-weighted images or enhanced T1-weighted images when gadolinium is injected
Use of PET Scans for Mesothelioma X Ray
PET nuclear scans are helpful in determining the prognosis of patients with malignant pleural mesothelioma, as they are sensitive enough to detect small increases in metabolic activity, allowing the detection of extremely small collections of cancer cells in remote locations of the body. Resolution of PET scan images are relatively low, hence the use of dual-imaging combinations of PET and CT scans at most modern cancer centers. This imaging technology is less valuable in the diagnosis and staging of peritoneal mesothelioma, but can be helpful in specific instances.
Common PET findings include:
- Extent or stage of lymph node involvement, tumors or metastases
- Differentiation of pleural mesothelioma from benign pleural lesions
- Pleural inflammation
This is a specialized ultrasound to evaluate the function of the heart. This helps determine if there is fluid in the lining around the heart as well as the overall function. It allows for visualization of the valves as the heart pumps. This is helpful when your doctors want to take a closer look at heart function beyond what is seen on a CT or MRI.