Lung Radiology 1
2INTRODUCTION
Radiologic evaluation of lung lesions can serve many roles including primary detection, narrowing of the differential diagnosis, treatment or surgical planning, and posttreatment surveillance. Plain radiographs are often the first-line modality for evaluation of symptomatic individuals and may be the source of detection of a lung lesion incidentally discovered during the course of other medical work-up. Nevertheless, CT remains as the mainstay of imaging characterization of lung disease due to its widespread access and excellent spatial resolution. CT is also often used as a rapid method of assessing the entire body for metastatic disease in the setting of lung malignancy. CT has a significant advantage over MRI in avoiding motion-related artifacts from breathing, due to the short image acquisition times possible with CT. MRI, on the other hand, is very useful in certain specific situations where its superior contrast resolution can better delineate soft tissue anatomy, such as in the evaluation of mediastinal or superior sulcus invasion by tumor. More recently, F-18 fluorodeoxyglucose-PET has become another widely used tool in diagnostic imaging of lung disease. Fluorodeoxyglucose-PET imaging utilizes the hypermetabolism of most tumors as a method of tumor localization and can be a very powerful tool in detection and assessment of tumor location and activity, sometimes revealing malignancy in places that would otherwise be overlooked by anatomic imaging alone.
In spite of all the technical advances in imaging, clinical and pathologic correlation are often necessary for accurate diagnosis. Image guidance with fluoroscopy, CT, ultrasound, and MRI is commonly used for minimally invasive tissue sampling in the hopes of avoiding or better preparing for a more extensive surgical approach.
This chapter presents the radiologic imaging of a sample of lung pathologies presented in the following order: malignant primary lung carcinoma, benign primary lung neoplasms, metastatic disease, infections, and other miscellaneous lung lesions, some of which can mimic neoplasm on imaging. The goal of this chapter is to provide some insight into the strengths of imaging in diagnosis of lung pathology and to highlight the crucial role that patient history and pathologic correlation often play in overcoming the limitations of imaging alone in order to arrive at a final diagnosis.