S516 I. J. Radiation Oncology d Biology d Physics Volume 72, Number 1, Supplement, 2008

delivers a dose of 5 Gy on average (10% of target dose) to the contralateral lung and contralateral breast, whereas these criticalstructures could be completely spared when using electrons.

Conclusions: Tomotherapy and Electron IMRT are well-suited to deliver homogenous dose distributions in funnel breast targetsand avoid high dose exposures in adjacent organs. The most important treatment improvements in Electron IMRT are the lowerdose in the heart and liver as well as the much smaller irradiated volume and thus the lower risk of radiation-induced diseases.

Author Disclosure: T. Gauer, None; K. Engel, None; J. Sokoll, None; C. Grohmann, None; F. Cremers, None.

2776 Visual Coaching Based on 3D Surface Imaging for Improvement of the Reproducibility and Stability of

Deep-inspiration Breath Hold for Radiation Therapy of Left-breast Cancer Patients

L. I. Cervino, C. Yashar, M. A. Rose, G. White, D. Scanderbeg, S. B. Jiang

University of California, San Diego, La Jolla, CA

Purpose/Objectives: To evaluate the effect of visual coaching from 3D surface imaging in the reproducibility and stability ofDeep-Inspiration Breath Hold (DIBH) for left-breast cancer patients’ radiation therapy.

Materials/Method: Two groups of patients and one group of volunteers were used in this study. The first patient group includes 5breast cancer patients who were treated with brachytherapy and underwent daily CT scans at DIBH without visual coaching for 6consecutive days. Reproducibility of the DIBH was analyzed retrospectively by measuring the spine to breast surface distance inall the scans at the same axial position. The second patient group (5 left-breast cancer patients) and the volunteer group (7 vol-unteers) were studied for DIBH with and without visual coaching. They were instructed to perform a series of four 20-secondDIBHs without coaching followed by a series of 4 DIBHs with visual coaching. A 3D surface imaging system (Vision RTLtd, London) was used to track in real time the motion of the breast surface. The motion signal was shown to the patients andvolunteers through a pair of video goggles for visual coaching. During the non-coached series of DIBHs a proper DIBH levelwas identified for each person. When coached, the patients and volunteers were asked to maintain their DIBH respiratory signalat this level. Reproducibility and stability of the DIBH were measured for each person. Reproducibility is defined as the standarddeviation of the level of the different DIBHs. Stability is measured as the average standard deviation of the breathing signals withineach individual DIBH.

Results: The reproducibility observed in the analysis of the first patient group is 2.2 ± 0.3mm (mean ± 1 standard deviation). In thesecond patient group, the variation of the DIBH level without coaching can be up to 15% of total breast motion. On average, re-producibility improved from 0.7 ± 0.4 mm without visual coaching to 0.3 ± 0.1 mm with visual coaching in the second patientgroup and from 1.0 ± 0.6 mm to 0.3 ± 0.2 mm in the volunteer group. Stability improved from 0.3 ± 0.1 mm to 0.2 ± 0.1 mmin the second patient group and from 0.6 ± 0.4 mm to 0.4 ± 0.3 mm in the volunteer group. Of all the 12 patients and volunteers11 of them improved reproducibility and 9 improved stability when visual coaching was provided. One patient had difficultiesinterpreting and using the visual feedback.

Conclusions: This work indicates that gated radiotherapy at DIBH of the left-breast cancer will benefit from visual coaching of thepatient’s breath hold. Visual coaching improves reproducibility and stability of the DIBH, both properties that need to be guaran-teed for an accurate and efficient gated treatment. In the future more patients will be investigated.

Author Disclosure: L.I. Cervino, None; C. Yashar, None; M.A. Rose, None; G. White, None; D. Scanderbeg, None; S.B. Jiang,None.

2777 Three-dimensional Dose Modeling of the AccuBoost Mammography-based Image Guided Non-invasive

Breast Brachytherapy System for Partial Breast Irradiation

S. Sioshansi1,2, J. R. Hiatt2, M. J. Rivard1, J. T. Hepel1,2, G. A. Cardarelli2, S. O’Leary1, D. E. Wazer1,2

1Department of Radiation Oncology, Tufts Medical Center, Tufts University School of Medicine, Boston, MA, 2Department ofRadiation Oncology, Rhode Island Hospital, Brown University School of Medicine, Providence, RI

Purpose/Objective(s): To perform 3D dose modeling and dose-volume analysis of the AccuBoost system.

Materials/Methods: AccuBoost is an image-guided breast brachytherapy system consisting of breast immobilization via moder-ate compression followed by 2D mammographic target localization. Tungsten applicators direct HDR 192Ir emissions along twoaxes. Dosimetric characterization of individual applicators has been performed. However, 3D dose modeling of all four applicatortreatment positions has not been examined due to limitations of conventional brachytherapy treatment planning systems to modelthe tungsten applicator collimation, and variable tissue deformation as a consequence of breast compression in both axes. Conse-quently, Pinnacle was modified where the cylindrical AccuBoost dose distribution in breast was modeled as a single point-sourcewith appropriate simulated anisotropy using the 2D brachytherapy dosimetry formalism. These source data were combined withcompressed breast CT data where patients were placed prone on a specially constructed table such that the breast would fall freelyforward. Two image datasets were taken, using cranial-caudal (CC) and medial-lateral (ML) compression axes. Patient and phan-tom dose distributions were calculated using a 1 mm3 grid. PTV, normal breast, and other clinical indicators of dose coverage wereassessed.

Results: As applicator size increased, normal breast dose coverage gradually increased and PTV coverage markedly improvedupon selection of the appropriate applicator size. 3D dose modeling of a single irradiation axis indicated target dose uniformityas a function of applicator diameter and applicator separation (i.e., breast compression). Even with one axis, target isodose coveragewas $95% while delivering .50% of the prescription dose to\20% of the remaining normal breast (largely confined to within thetreatment axis). Chest wall or underlying lung dose was typically #10%. Using four treatment fields, target dose conformity wasfurther enhanced while normal breast dose was distributed over a larger volume. PTV dose distributions for combined CC+MLtreatment positions produced relatively uniform dose distribution for breast compression #7 cm. Comparisons of AccuBoost plansgenerated in the same patients for tumor bed boost with en-face electrons or 3D-CRT accelerated partial breast irradiation (APBI)showed comparable or superior target coverage with AccuBoost.

Proceedings of the 50th Annual ASTRO Meeting S517

Conclusions: AccuBoost 3D dose modeling demonstrates excellent target coverage and normal tissue exposures within acceptabledose limits. Preliminary data suggests that AccuBoost may have comparable or superior dosimetric characteristics to electron beamand 3D-CRT APBI techniques.

Author Disclosure: S. Sioshansi, I am related to the President and CEO of Advanced Radiation Therapy, the AccuBoost manufac-turer, G. Other; J.R. Hiatt, None; M.J. Rivard, Advanced Radiation Therapy, F. Consultant/Advisory Board; J.T. Hepel, None;G.A. Cardarelli, None; S. O’Leary, None; D.E. Wazer, Advanced Radiation Therapy, F. Consultant/Advisory Board.

2778 A Modulated Electron Radiotherapy Program: Planning, Optimization, Delivery and Verification

E. E. Klein, M. Surucu, M. Mamalui-Hunter, D. B. Mansur, D. A. Low

Washington University, St. Louis, MO

Purpose/Objective(s): To develop a comprehensive program for modulated electron radiotherapy (MERT). All steps; MonteCarlo (MC) based treatment planning, energy and segment optimization, delivery using the photon multileaf collimators, and mon-itoring during treatment, are necessary. Comparisons with conventional (CRT) and photon IMRT plans will be conducted.

Materials/Methods: We previously demonstrated the multi-leaf collimation (MLC) system for modulating photons is ideal forMERT due to the systems’ efficiency and safety. Multiple electron segments were combined to deliver predictable, conformaldose distributions. Monte Carlo calculations were used; BEAMnrc for phase space file generation, MCSim for MC dose calcula-tions, and CERR for energy/segment size/dose weighting optimization using custom GUIs. Once segments were devised, MLC leafdelivery instructions were appropriated using Shaper. Dosimetric validation was performed with film and ionization chambers forVarian IX accelerator delivered electrons. Phantom targets including imbedded heterogeneities (bone, lung) were planned withdelivery validated by measurements. Clinical cases (post-mastectomy chest wall and cutaneous lymphoma of the scalp) previouslytreated by CRT or IMRT methods were planned for MERT. Comparison of isodose and DVHs was conducted in CERR for MERT,IMRT (Pinnacle or Tomotherapy) and/or CRT plans. Treatment execution at 70cm SSD, necessary for MERT, was simulated toensure safety and efficiency. Service mode operation is currently required to deliver MERT with the photon MLC. AlignRT (Vi-sionRT, UK), a video based surface imaging system, was tested for daily localization and monitoring.

Results: Dosimetric validation for all available energies in the phantom studies was successful (2 mm/3% agreement) for segmentsizes ranging from 10 to 100 mm. The MERT chest wall cases were planned and optimized for a single table and gantry position, 9segments, and 4 energies. Phantom delivery time was 3.50. Planning provided homogeneous coverage (± 10%) to the chest wall andIM nodes, without consequence of excessive high dose regions, as with IMRT and CRT. Dose to lung and heart were lower forMERT plans, typically less than half. Dose to the contralateral breast using MERT was less than 10% of the dose received usingCRT or IMRT. The VisionRT system worked for the MERT technique (short SSD). Scalp planning was complex, requiring 2 tableand 3 gantry angles, 2 energies, and 11 segments. Planning provided homogeneous coverage (± 9%), with complete sparing ofbrain tissue.

Conclusions: We have demonstrated conformal distributions for chest wall and scalp with MERT, superior to CRT or IMRT. Plan-ning, optimization, delivery, and verification for MERT were achieved. IRB approval for MERT with photon MLCs is being pursued.

Author Disclosure: E.E. Klein, None; M. Surucu, None; M. Mamalui-Hunter, None; D.B. Mansur, None; D.A. Low, None.

2779 Interstitial High Dose Rate (HDR) Brachytherapy for Early Stage Breast Cancer: Five Year Follow-up of

168 Cases using Multi-catheter Technique

P. J. Anderson1, R. Mark1,2, T. Neumann1, M. Nair1, R. Akins3, S. Gurley1, D. White1

1Joe Arrington Cancer Center, Lubbock, TX, 2Texas Tech University, Lubbock, TX, 3University of Miami, Miami, FL

Purpose/Objective(s): External Beam Radiation Therapy (EBRT) has been the standard of care for breast conservation radiationtherapy. Recent data indicates that Interstitial Implant and High Dose Rate (HDR) radiation afterloading compares very favorablyto EBRT in selected patients.

Materials/Methods: Patients with Tis, T1, and T2 tumors measuring #3 cm, negative surgical margins, and negative axillarylymph nodes were judged to be candidates for Interstitial Implant. Implants were performed under Stereotactic Mammographicguidance with conscious sedation and local anesthesia. The implants were placed using the Anderson-Nair Template usingfrom 3 to 8 planes, and 8 to 62 needles. Catheters were subsequently threaded thru the needles, and the needles removed. Catheterspacing was 1.0 to 1.5 cm. Radiation Treatment planning was performed using CT Scanning and the Plato System. Treatment vol-umes ranged from 25 cm3 to 359 cm3. HDR treatment was given using the Nucletron afterloading system. The breast implant vol-ume received 3,400 cGy in 10 fractions prescribed to the Planning Target Volume, given BID over 5 days.

Results: Between 2000 and 2008, 168 patients underwent Interstitial HDR Implant. The procedure was well tolerated. No patientrequired hospital admission. With a median follow-up 60 months (range, 6-98 months), local recurrence occurred in 3.6% (6/168).Cosmetic results were good to excellent in 88.1% (148/168) of the patients. There were no infections. Wound healing complica-tions developed in 4.8% (8/168). Three of these patients had received anthracycline based Chemotherapy. The other five had large(.200 cm3) implant volumes, catheter spacing of 1.5 cm, and V-150% of .30%. Two patients healed after 6 months of conser-vative treatment. Surgery was required in 6 patients who developed fat necrosis.

Conclusions: With median 60 month follow-up, Breast Conservation radiation therapy utilizing Interstitial Multi-Catheter HDRImplant has yielded local recurrence rates and cosmetic results which compare favorably to EBRT in selected patients. Treatmentwith anthracycline based Chemotherapy, large (.200 cm3) implant volumes, and V-150% .30%, appear to be relative contrain-dications to Interstitial HDR Implant. Finally, catheter spacing of 1 cm yielded optimal dosimetry and minimized complications.Compared to MammoSite technique, the Interstitial Multi-Catheter method offers greater flexibility of radiation delivery. Advan-tages include, no concern regarding surgical cavity shape irregularities, balloon conformality to surgical cavity, balloon rupture,balloon movement, air gaps, skin balloon proximity to skin, balloon shape distortion, and catheter movement within the balloon.

Author Disclosure: P.J. Anderson, None; R. Mark, None; T. Neumann, None; M. Nair, None; R. Akins, None; S. Gurley, None; D.White, None.