Purpose: To obtain a snapshot of X-ray imaging practices for Radiation Therapy (RT) in the United States.
Methods: The ICRP TG-116 “Radiologic aspects of imaging in Radiation Therapy” developed a comprehensive survey to understand x-ray imaging practices in RT. Requests were sent to 72 physicists at US treatment centers. Responses were collected between August and October 2020.
Results: Responses were received from 30 centers (57% were academic institutions) covering 143 linacs. The monthly patient loads (median:117 ranged between [20 – 380] patients per center. Reported imaging modalities for treatment planning include CT, MRI, PET, PET/CT, SPECT, angiograms, ultrasound, and optical systems. 92% of linacs are equipped with kV imaging, 70% of which are <10 years old. 80% of centers use IGRT for >75% patients, with planar kV-imaging and CBCT as standard modalities. All centers reported employing kV-CBCT routinely except for palliative patients. MV-MV pairs remain heavily used in public (tax-payer funded, not-for profit) centers and academic centers. The most frequently treated sites are lung, prostate and breast. The main imaging frequency is “daily” (>90%) except for breast (50% daily, 47% weekly, 3% T.I.W). Most cited reasons for optimizing imaging protocols were patient habitus and adjusting FOV to improve anatomical visualization. Reported imaging dose optimization methods included pediatric protocols for radiologic imaging, and employing Surface Guided RT (breast). Academic RT centers tend to spend more effort on imaging protocols optimization, facilitated by the easier access to local imaging physicists for consultation. Most centers perform monthly imaging QA, citing AAPM TG-142 as reference. However, only 63.3% of centers include imaging dose measurement as part of their QA protocols.
Conclusion: IGRT has become the standard of care in the US. Most academic centers optimize their imaging protocols, but image quality is the main motivator rather than dose optimization, except for pediatric patients.
Not Applicable / None Entered.