The need to detect and characterize cancer in an individual has resulted in a dramatic increase in the use of imaging over the last 20 years. Clinical imaging is now a routine part of diagnosis, staging, guiding localized therapy, and assessing response to treatment. Cancers occur anatomically among surrounding normal tissues, including critical structures, such as major vessels and nerves, and delineation of the extent of malignant and nonmalignant tissues is essential for planning surgery and radiation therapy. Cancers also have morphological, physiological, and biochemical heterogeneity (see Chaps. 10 and 12), which is important in understanding their biology and response to treatment. The ability to explore and define this heterogeneity with modern imaging methods, as well as serum and tissue-derived metrics, will enable "personalized cancer medicine."
Imaging is diverse in that it offers an "anatomical image" of a mass on a computed tomography (CT) or a magnetic resonance (MR) image, a "functional image" of disease status in positron emission tomography (PET) images of glucose metabolism, and a "microscopic image" used during classification of histological type and grade. Imaging is applied at these multiple levels to help characterize, understand, and treat cancer (Fig. 14–1) and there is general acceptance that advances in imaging are central in the fight against cancer. This chapter provides a brief introduction to the rapidly evolving field of oncological imaging by presenting both the physical principles underlying the most common imaging modalities and their clinical and research applications in oncology.
Different visual representations of cancer at different spatial scales and time points. A) Traditional hematoxylin and eosin (H&E) staining of a cervix cancer xenograft. These stains highlight the cellular architecture and are used to assess histological type and grade of cancer. B) More advanced immunohistochemical staining of the same tumor demonstrating the complex microenvironment with the tumor. Substantial variation in microvasculature (CD31, green) and oxygen tension (EF5, red) are seen despite the evidence that the tumor is perfused (indicated by the injected Hoechst 33342 dye, blue). C) T2-weighted MR image of a cancer of the cervix before (left) and during (right) radiotherapy (after 48 Gy) showing regression of the tumor as outlined in red. D) Slice taken from a CT image of a lung cancer patient being planned for radiation therapy. The corresponding fluorodeoxyglucose (FDG)-PET image is on the right. Functional and anatomical information are often complementary in describing the extent and nature of the cancer. The purple outlines demonstrate the volume to be irradiated as part of the radiation treatment.
14.2 GENERAL CONCEPTS RELATING TO CANCER IMAGING
Imaging is a broad science that encompasses the design, development, evaluation, and application of technologies that allow spatial and temporal characterization of an object; ideally, with a minimum of invasion. When using imaging, it is important to understand ...