Topographical dose determination in an anthropomorphic head and neck phantom
This protocol is extracted from research article:
Determination of topographical radiation dose profiles using gel nanosensors
Sci Adv, Nov 15, 2019; DOI: 10.1126/sciadv.aaw8704

An anthropomorphic head and neck phantom was used to determine the efficacy of topographical dose determination of the gel nanosensor in a clinical setting. Computer tomography (CT) images (1-mm slices) were acquired throughout the head region and transferred to a Philips Pinnacle treatment planning system. To simulate an actual clinical treatment, an irregularly shaped gross target volume (GTV) was generated using several CT images. The GTV was defined superficially above the left maxillary sinus, and a single 6-MV highly conformal photon (x-ray) beam was aimed at a discrete angle at the target to avoid nearby critical structures such as the left orbit. A multileaf collimator was used to shape and conform the radiation dose to a target field of 2.5 cm × 1.9 cm. Within this target region, a crescent-shaped beam was delivered using the multileaf collimator. Radiation beams incident on contoured anatomical structures led to uncertainty and nonuniformity in the radiation dose deposited (42). To flatten the surface exposed to ionizing radiation and ensure homogeneous dose deposition, a 1.5-cm synthetic vinyl gel with physical properties similar to that of tissue (tissue equivalent “bolus”) was placed over the target area. In addition, the use of a bolus facilitates deposition of maximal dose on the skin surface based on dose deposition profiles in x-ray radiotherapy (43). In the absence of the bolus, the radiation dose deposited is typically less than the prescribed dose, which could potentially lead to suboptimal therapeutic outcomes (43). A single dose (2 Gy) was delivered to the surface of the head and neck phantom.

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