Manjeet Chadha MD, Presenter: Grant, Resonant Medical Inc

Robert Masino MS, Abstract Co-Author: Nothing to Disclose

Denise Kraemer RT, Abstract Co-Author: Nothing to Disclose

Susan Boolbol MD, Abstract Co-Author: Nothing to Disclose

Eli Furhang PhD, Abstract Co-Author: Nothing to Disclose

Louis B. Harrison MD, Abstract Co-Author: Nothing to Disclose

There is a growing interest in IGRT techniques that visualize the target and allow correction for target motion prior to delivering the RT fraction. This is particularly relevant when using small conformal radiation beams for treatment delivery. Most current IGRT techniques result in additional radiation exposure to the patient. We describe the application of 3D US for localizing the breast boost. The objectives of this study are to assess the feasibility of using 3D US IGRT in a busy practice, and to evaluate the inter-fractional localization of the target in relation to the electron beam’s eye view (EBEV).

This is an IRB approved prospective study using the ClarityTM 3D US breast system (Resonant Medical). At simulation, concurrent CT and 3D US images are captured to obtain a fused CT/US dataset. The target volume (TV) for boost is delineated as the lumpectomy cavity plus a1.5 to 2 cm margin. In addition, for this study we contour the seroma cavity (SC) within the TV as visualized on US. This is established as the reference volume (RV) for IGRT tracking. For each fraction, an US scan of the SC is acquired in treatment position. As the treatment field is aligned on the breast for the planned boost treatment, the Clarity software interface tracks the acquired SC image relative to the stored RV image and the EBEV. The visual graphics as well as the positions of the SC image, RV image and the EBEV are recorded for analysis.

To date 12 patients are enrolled. Four patients did not have a SC and could not be included in the study. Analysis of data on the first 20 treatment fractions is described. The SC for IGRT tracking was easily identifiable for all treatment fractions. Between fractions the radial deviations of SC and RV in the EBEV averaged 0.5 ± 0.3 cm. In 45% of fractions this deviation exceeded 0.5 cm, potentially placing the margins of the target volume within the dosimetric penumbra of the field. Once the staff was fully trained the use of 3D US added an average of 3 minutes to each treatment session.

Our initial observations suggest that 3D US can be successfully used without significantly interfering with patient throughput in a busy department. The 3D US for IGRT tracking could be used only when a SC is present. Although the Clarity software enables us to correct for target motion on the treatment table, this initial study design does not include adjusting the patient set up based on the localization of the SC. In almost half the treatment fractions we observed that set up adjustments based on the US image may be indicated to improve compliance of prescription dose to target. The study is ongoing and a full analysis on 100 treatment fractions is planned.

Chadha, M, Masino, R, Kraemer, D, Boolbol, S, Furhang, E, Harrison, L, Image-guided Radiation Therapy (IGRT) in the Treatment of Breast Cancer Using Three-dimensional Ultrasound (3D US) Breast System: Preliminary Results.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/7001354.html