4. Brachytherapy Imaging for Treatment Planning

Various imaging modalities have been used to stage patients with gynecologic cancers and are invaluable in assessing local, regional, and metastatic spread of disease. As cervical cancer is directly accessible on pelvic examination, clinical findings based on visual and digital examination, and documented on clinical diagrams, also remain essential. Plain radiographs, including chest x rays, barium enemas (BE), intravenous urography (IVU), skeletal surveys, and lymphangiography (LAG), as well as cystoscopy and rectal endoscopy, have long been mainstays of staging of cervical cancer and remain so in many parts of the world. Radiographs to guide both external-beam therapy and brachytherapy have been used nearly universally, but are limited by their inability to demonstrate the tumor and its extensions to many of the critical, adjacent abdomino-pelvic organs. Reliance on bony anatomy is not sufficient for treatment planning for cervical cancer (Finlay et al., 2006; McAlpine et al., 2004). More recently, three-dimensional (3D)-imaging methods such as computed tomography (CT) and magnetic resonance imaging (MRI) have become the techniques of choice for external-beam and brachytherapy treatment planning, for monitoring response during treatment, and for post-treatment surveillance. Functional imaging, in particular positron-emission tomography (PET) combined with CT, and, recently functional MRI, play increasingly important roles. Ultrasound (US) has been replaced by MRI in the last two decades in the initial staging of patients, but it might have an essential role for image-guided intracavitary and interstitial gynecologic brachytherapy. The focus in the following will be on the role of clinical diagrams and imaging in treatment planning and response monitoring leading to adaptive therapy.