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A prospective evaluation comparing CT localization with daily ultrasound during image-guided radiation therapy for the treatment of prostate cancer
Abstract
Purpose: To describe the results of a prospective trial which compared isocenter shifts produced by the BAT ultrasound (U/S) to the shifts produced by a computed tomography (CT) unit in the treatment room to aid in positioning during image-guided radiation therapy.
Methods: Fifteen consecutive patients with localized prostate cancer were included. All patients underwent CT and MR simulation immobilized supine in an Alpha cradle and were treated with intensity modulated radiation therapy. BAT U/S were used daily to correct for interfraction motion by obtaining a shift in the x, y and z directions. Two days a week during their therapy, CT scans were obtained blinded to the U/S shifts, and were recorded.
Results: Two hundred and eighteen alignments from 15 patients were analyzed. There was a high level of correlation between the CT and U/S isocenter shifts [correlation coefficient 0.877 (AP), 0.842 (lateral) and 0.831 (superior-anterior)]. The systematic errors were less than 1 mm, while the random errors were approximately 2 mm. The total errors including both systemic and random errors were less than 2 mm in all directions.
Conclusions: The software used to calculate the isocenter shifts for the CT highly correlates with BAT U/S system produced shifts.
Methods: Fifteen consecutive patients with localized prostate cancer were included. All patients underwent CT and MR simulation immobilized supine in an Alpha cradle and were treated with intensity modulated radiation therapy. BAT U/S were used daily to correct for interfraction motion by obtaining a shift in the x, y and z directions. Two days a week during their therapy, CT scans were obtained blinded to the U/S shifts, and were recorded.
Results: Two hundred and eighteen alignments from 15 patients were analyzed. There was a high level of correlation between the CT and U/S isocenter shifts [correlation coefficient 0.877 (AP), 0.842 (lateral) and 0.831 (superior-anterior)]. The systematic errors were less than 1 mm, while the random errors were approximately 2 mm. The total errors including both systemic and random errors were less than 2 mm in all directions.
Conclusions: The software used to calculate the isocenter shifts for the CT highly correlates with BAT U/S system produced shifts.
Keywords
Image guided radiotherapy, prostate cancer, CT localization, ultrasound localization