The need to detect and characterize cancer in an individual has resulted in a dramatic increase in the use of imaging. Clinical imaging is 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 organs, vessels, and nerves, and delineation of the extent of malignant and nonmalignant tissues is essential for planning surgery and radiation therapy. Cancers also have morphologic, physiologic, and biochemical heterogeneity (see Chap. 13), which is important in understanding their biology and potential 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 more precise cancer treatments.
Imaging is diverse in that it offers multiple different representations of disease information. For example, computed tomography (CT) or magnetic resonance (MR) imaging provides an “anatomical image” of the malignant tissue among nonmalignant tissue; positron emission tomography (PET) images generate a “functional image” of disease status related to tissue function such as glucose metabolism (see Chap. 12) or hypoxic fraction (see Chap. 12); and optical imaging can be used to generate a “microscopic image” used during classification of histologic type and grade. Imaging is applied at these multiple levels to help characterize, understand, and plan the treatment of cancers (Fig. 14–1). Advances in imaging are central in the fight against cancer. This chapter introduces the rapidly evolving field of oncologic 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 histologic 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 25 × 1.8-Gy fractions) 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, where the radiation target delineation has been refined by the functional information provided by the PET image.