ABSTRACT
Conventional simulators, more commonly called treatment simulators, have been developed to facilitate the radiographic visualization of treatment elds (Greene, Nelson, and Gibb 1964). Radiographs taken using the therapeutic source of treatment machines are of poor quality because megavoltage photon beams result in mostly Compton scattering. A conventional simulator will have identical machine parameters to those of a megavoltage treatment unit, including geometrical, mechanical, and optical properties, except it is tted with a diagnostic x-ray tube as shown in Figure 67.1. e exposure from the diagnostic x-ray tube provides high image contrast so that anatomical structures can be clearly dened for the assessment of the appropriateness of eld placement and eld shaping to minimize the irradiation of the surrounding normal tissues. Besides having superior radiographic quality, conventional simulators are used for time-consuming patient position verication procedures and for correcting unforeseen setup problems, hence freeing the treatment machines for other clinical use (e.g., treating patients), which results in higher patient throughput.
