Comparing computed tomography localization with daily ultrasound during image‐guided radiation therapy for the treatment of prostate cancer: a prospective evaluation

Steven J Feigenberg,Eric M Horwitz,Lu Wang,Andre Konski,Shawn Mcneeley,Charlie Ma,Alan Pollack,Kamen Paskalev

doi:10.1120/jacmp.v8i3.2268

Steven J Feigenberg, Eric M Horwitz + Show 6 more

Open Access

https://doi.org/10.1120/jacmp.v8i3.2268

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Abstract

In the present paper, we describe the results of a prospective trial that compared isocenter shifts produced by BAT Ultrasound (Nomos, Sewicky, PA) to those produced by a computed tomography (CT) unit in the treatment room to aid in positioning during image‐guided radiation therapy.The trial included 15 consecutive patients with localized prostate cancer. All patients underwent CT and MR simulation immobilized supine in an Alpha Cradle and were treated with intensity‐modulated radiation therapy. BAT Ultrasound was used daily to correct for interfraction motion by obtaining shift in the x, y, and z directions. Two days per week during therapy, CT scans blinded to the ultrasound shifts were obtained and recorded.We analyzed 218 alignments from the 15 patients and observed a high level of correlation between the CT and ultrasound isocenter shifts (correlation coefficients: 0.877 anterior–posterior, 0.842 lateral, and 0.831 superior–inferior). The systematic differences were less than 1 mm, and the random differences were approximately 2 mm. The average absolute differences, including both systemic and random differences, were less than 2 mm in all directions.The isocenter shifts generated by using a CT unit in the treatment room correlate highly with shifts produced by the BAT Ultrasound system.PACS numbers: 87.53, 87.59.fm, 87.63.Df

Highlights

Improvements in radiotherapy treatment and delivery techniques have led to improvements in treatment outcomes
Daily uncertainties regarding patient setup reproducibility and the position of the prostate within the pelvis because of combinations of rectal and bladder filling diminish the ability to achieve this goal.[2]. The frequently changing nature of these variations has in the past made correction difficult and dictated that a wider margin of normal tissue be included within the radiation field to ensure complete tumor coverage
A recent study described the margins required to account for prostate motion 95% of the time: 5.3 mm in the lateral direction; 10.4 mm in the anterior–posterior (AP); and 10.4 mm in the superior–inferior.[1,2] These margins related to interfraction setup error can be reduced by several techniques that directly visualize the prostate before treatment

Summary

INTRODUCTION

Improvements in radiotherapy treatment and delivery techniques have led to improvements in treatment outcomes. A recent study described the margins required to account for prostate motion 95% of the time: 5.3 mm in the lateral direction; 10.4 mm in the anterior–posterior (AP); and 10.4 mm in the superior–inferior.[1,2] These margins related to interfraction setup error can be reduced by several techniques that directly visualize the prostate before treatment To reduce these uncertainties at Fox Chase Cancer Center in the mid-1990s, we first performed daily computed tomography (CT) scans for patients receiving three-dimensional conformal radiation therapy.[3] In this costly and time-consuming process, patients underwent CT simulation in one room and were transported to the treatment machine while remaining in the immobilization cast. The present paper describes the first part of a prospective trial that compared the isocenter shifts produced by the BAT Ultrasound system with the shifts produced by software provided by Siemens for the Primatom CT-on-Rails (Siemens Medical Solutions, Concord, CA)

PATIENTS AND METHODS

Comparison of CT versus ultrasound

RESULTS

DISCUSSION