Objective To evaluate the clinical application value of individualized three dimensional (3D) printed thoracic phantoms (referred to as phantoms) in dose verification for intensity-modulated radiation therapy.

Methods A retrospective study was conducted using the CT localization images in digital imaging and communications in medicine format obtained from a patient ( female, 78 years old) with esophageal cancer treated at the Xuzhou Cancer Hospital in October 2023. Intensity-modulated radiation therapy plans were designed on the basis of the patient and phantom CT images. Dosimetric parameters were compared for the target volume (vertebral body), organs at risk (spinal cord, bilateral lungs and heart) and a reference point (a measurement point within the right lung). A thimble ionization chamber was inserted into the target volume and the reference point through predesigned channels in the phantom. The phantom was fastened to the treatment couch of a medical linear accelerator, and the radiation plan was executed to collect dose data. Intergroup comparisons of measurement data were performed using one sample t-test.

Results Dose-volume histogram analysis demonstrated that the dose distribution curves for the target volume and organs at risk nearly overlapped in the phantom and patient intensity-modulated radiation therapy plans. Dose measurement experimental results showed five dose measurements for the target volume: 210.5, 211.1, 210.8, 210.7, 211.9 cGy. The average measured and calculated doses for the target volume were (211.0±0.5) cGy and 210.4 cGy, respectively, with absolute and relative dose deviations of 0.6 cGy (95%CI: −0.08 to 1.28) and 0.29% (95%CI: −0.04% to 0.61%), respectively. One sample t-test revealed a statistically significant difference between the five times measured and calculated doses for the target volume (t=2.449, P=0.035). For the reference point, the five dose measurements were 49.2, 49.8, 49.5, 49.4, 50.8 cGy. The average measured and calculated doses were (49.7±0.6) cGy and 49.1 cGy, respectively, with absolute and related dose deviations of 0.6 cGy (95%CI: −0.14 to 1.42) and 1.22% (95%CI: −0.29% to 2.91%), respectively. One sample t-test showed a statistically significant difference between the dose measured five times and the calculated dose for the reference point (t=2.268, P=0.043). The absolute values of relative dose deviations at both sites were <3%, meeting the requirements of the WS 674—2020 Specification for Testing of Quality Control in Medical Linear Accelerator.

Conclusion The phantom provides a dose verification method for clinical radiotherapy quality assurance.