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    Research Grants Awarded

    Breast Positioning And Topology Monitoring System Development For Image-Guided Radiation Therapy

    Study Section:
    Treatment

    Scientific Abstract:
    We will develop a new high-precision positioning system for image-guided radiation therapy to enhance modified breast conserving therapy (MBCT). MBCT requires accurate delivery (to within millimeters) to be safe and effective. Surface images of the target breast will be produced by a hand-held industrial scanning laser. We will modify the laser system and create software for human clinical application. After positioning the patient for treatment, the breast surface is scanned into a computer; the image is registered and compared to a reference image. The required translation and rotation to match the reference image will be converted to treatment room coordinates for repositioning the patient prior to daily treatment. Analysis of topological changes between treatments will be monitored to determine if the patient needs to be re-planned. The motivation for developing our system is to reduce treatment setup errors and enable more clinics to offer MBCT. Typical breast conserving therapy (BCT) involves a lumpectomy followed by external beam radiation and has a comparable cure rate to a mastectomy. Both therapies have about 90% non-recurrence of cancer as opposed to 40% using lumpectomy alone. Despite the obvious advantages of BCT, only 10 to 40% of patients who are candidates for BCT actually receive it due to the prolonged treatment regime - typically five to seven weeks. Radiation Therapy Oncology Group (RTOG) 0319 specifies an accelerated therapy lasting one week using higher doses per treatment. For higher daily doses to work, conformal shaped radiation beams are used to target the lumpectomy site while sparing normal tissues. We recently analyzed 2931 electronic portal images taken of 12 patients covering at least 10 fractions. It was shown that inaccurate targeting is dominated by errors in daily positioning or tissue deformation and average 1.5 cm (breathing motion is only ~0.3cm). By using our scanning system, the overall error could be reduced by about half (down to ~0.7cm). We believe this image-based patient positioning system will ultimately enable the widespread use of MBCT, which could benefit the estimated 71,000 patients who qualify for RTOG 0319 type therapy.

    Lay Abstract:
    We will develop a new high-precision positioning system for image-guided radiation therapy to enhance modified breast conserving treatment (MBCT), which requires accurate delivery to within millimeters to be safe and effective. Breast conserving therapy (BCT) involves a lumpectomy followed by external beam radiation and has a comparable cure rate to a mastectomy. Both therapies have about 90% non-recurrence of cancer as opposed to 40% using lumpectomy alone. Despite the obvious advantages of BCT, only 10 to 40% of patients who are candidates for BCT actually receive it due to the prolonged treatment regime - typically five to seven weeks. To make BCT more accessible, fewer daily treatments, but higher doses per treatment can be prescribed - MBCT. For higher daily doses to work, custom designed radiation treatment fields are used which are highly conformed to the target lumpectomy site. Surface imaging will improve current breast conserving radiation treatments by detecting changes in the location and shape of the target during the course of treatment. Typical daily positioning of the patient in the treatment room utilizes skin marks (tattoos). However, breast tissue is both mobile and malleable resulting in a changing target relative to the original tattoos. Our new optical breast positioning system is based on a scanned laser image unlike most currently available systems, which use additional radiation to image the breast. Through the comparison of daily images to a reference image, the breast can be accurately re-positioned. The images can also be used to calculate a new treatment plan to meet the intended prescription if necessary. This will insure the prescribed dose is delivered to the target cancer while sparing neighboring healthy tissue. We believe this image-based patient positioning system will ultimately enable the widespread use of MBCT, which could benefit the estimated 71,000 patients who qualify for this therapy.