ABSTRACT
Imaging has always been central to radiotherapy practice. Apart from the use of radioisotopes that are administered systemically, the methodology for external beam radiotherapy and brachytherapy (interstitial or intra-cavitary therapy) remains a localized treatment where the radiation source needs to be aimed or placed at the tumor or target volume. Thus appropriate imaging is crucial for radiotherapy practice in order to identify the target volume(s) in question and to accurately direct the radiation beams to the nominated target(s). Radiation has been utilized for medical treatments since the discovery of ionizing radiation by WC Röntgen in 1895. In the early days of radiation use, visual identification or physical palpation of abnormal masses was used to guide radiotherapy. Subsequently radiological imaging using plain X-rays and anatomical landmarks directed the clinician in the placement of radiotherapy fields. The advent of cross-sectional imaging and advances in medical equipment technology has consequently led to a revolution in the practice of radiotherapy and will be described in the next section.
