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Dosimetric Evaluation of Structural Modifications Made to a Currently Used 125I Seed for Prostate Brachytherapy
S92
Abstracts / Brachytherapy 9 (2010) S23eS102
equivalent uniform dose (EUD) were calculated for the range of parameter values. Results: For the limited range of radius relevant to ABPI balloon based brachytherapy, a phenomenological parameterization g(r) can be established. Over the range of parameterizations from 192Ir to 103Pd DHI decreases with decreasing energy. The relationship between DHI and EUD is presented as a function of energy parameterization as well as parameters relating calculation of EUD. Conclusions: The choice of device used for APBI balloon-based brachytherapy will have an effect on related dosimetric quantities. The dependence of these effects on balloon size and device energy were presented in a manner that can be applied to new sources or devices as they come on the market. Comparing outcomes of patients receiving APBI at different energies offers an opportunity to determine which dosimetric quantities are related to outcome. The lower values of the DHI metric has been associated with poorer outcome. Using lower energy sources will produce lower values of DHI which could reasonably be expected to adversely affect outcome.
PO32 Analysis of Dosimetric Quantities Associated with Partial Breast Brachytherapy Desmond A. O’Farrell, M.Sc.1, Alexandra J. Stewart, M.D.2, Phillip M. Devlin, M.D.1, Robert A. Cormack, Ph.D.1 1Radiation Oncology, Dana-Farber Cancer Institute/Brigham and Women’s Hospital, Boston, MA; 2Radiation Oncology, Royal Surrey County Hospital, Guildford, United Kingdom. Purpose: Radiation dose to the heart and lung are a concern in accelerated partial breast irradiation (APBI). This work presents an analysis of the metrics inherent to high-dose-rate APBI using a 192Ir brachytherapy source. Materials and Methods: Seven patients, who were simulated in both supine and prone position for XRT, were contoured. Dose to the heart and lung were calculated for all potential dwell locations within the contoured breast for a range of potential dwell times. Summary volume and dose metrics were calculated for heart and lung as function of distance to the normal structures. The distribution of distances was then compared for the prone and supine patients. Results: Upper bounds on metrics as a function of distance were evaluated for all patients. Upper bounds as a function of distance can be parameterized, but patient anatomy variations prevent the creation of a generalized bound on the dose quantities such as D10cc or volume metrics such as V10Gy. The characterization provides a measure of the normal tissue dose parameters that are achievable as a function of dmin. While prone position shift the distribution of lung to breast distances towards greater value, the distribution of heart to breast distances is shifted to smaller distances. Conclusions: Characteristic curves of the achievable volume metrics as a function of minimum distance from implant to normal structures are presented. These curves may be helpful in the decision to use APBI brachytherapy based on the location of the cavity. The choice of treatment position affects the distribution of breast tissue, though the effect on distance to heart and lung differs.
PO33 The Role of the Brachytherapy Specialist in Prostate Brachytherapy Paul W. Mueller, B.S., R.T.T., Thomas G. Shanahan, M.D., Yaxiang Yang, Ph.D., Ray R. Capestrain, M.S., Randy B. Maxey, M.S. Radiation Oncology, Memorial Medical Center, Springfield, IL. Purpose: A radiation therapist with additional training in fluoroscopy, ultrasound (both for volume study and intraoperative), seed ordering and assay quality assurance, intraoperative assistance, and radiation safety procedures could offer a major benefit in continuity of care and relieve time requirements of other ancillary staff. We review the role and value of a brachytheray specialist in a large community prostate brachytherapy practice.
Materials and Methods: A position of brachytherapy specialist was created in 1999 to combine numerous job responsibilities to a single individual with the goal of maximizing efficiency of time, continuity of care, and maximizing radiation procedural safety. From 1999-2009, 1200 patients were implanted in a single institution with the benefits of a brachtherapy specialist combining the roles of radiation physicist, ultrasonogragher, fluoroscopy technician, and scrub nurse. Day 0 CT dosimetry was obtained within 3 hours in each patient with the urinary catheter in place. Results: Main operating room time was less than one hour and total physicist’s time was 30 minutes per patient. Seed counts were maintained throughout the procedure. Conclusions: The role of the brachytherapist can add to the quality and efficiency of the prostate brachytherapy team. In this article we review our experince and many of the benefits of a brachytherapy specialist to a busy community practice.
PO34 Dosimetric Evaluation of Structural Modifications Made to a Currently Used 125I Seed for Prostate Brachytherapy Jose L. Garcia Ramirez, M.S., Kevin Moore, Ph.D., Olga Pechnaya, Ph.D. Radiation Oncology, Washington University School of Medicine St. Louis, St. Louis, MO. Purpose: To determine the dosimetric differences between a standard ‘‘bare’’ IsoAid Advantage 125IÔ seed (model IAI-125A) and AnchorSeedÔ, which consists of a standard IAI-125A seed surrounded by bands of suture-like material. Materials and Methods: Two sources with equivalent seed activity were acquired from the manufacturer. Dose calibrator and relative film dosimetry measurements were performed. Results: Measured air-kerma strength (Sk) values of the two sources were found to be within 0.5%. Relative film dosimetry indicated agreement within 1%/1mm in the dose distribution. Conclusions: The new modifications made to the current source do not alter the dosimetric characteristics of the seed model. The dosimetric data currently used should not be changed.
PROSTATE POSTERS ThursdayeSaturday PO35 Interstitial High-Dose-Rate Brachytherapy under Local Anesthesia for Early Stage Prostate Cancer: A Report of 504 Cases Rufus J. Mark, M.D.1, Paul J. Anderson, M.D.1, Robin S. Akins, M.D.2, Murali Nair, Ph.D.1 1Radiation Oncology, Joe Arrington Cancer Center, Lubbock, TX; 2Radiation Oncology, Wilford Hall Medical Center, Lackland Airforce Base, TX. Purpose: Transrectal ultrasound (TRUS)- guided interstitial implant for prostate cancer using low-dose-rate (LDR) and high-dose-rate (HDR) techniques has been reported with results comparing very favorably to external beam radiation therapy. TRUS interstitial implant of the prostate has been traditionally performed under general or spinal anesthetic in an operating room. We report our results with a technique performed under local anesthesia in a department procedure room. Materials and Methods: Patients with T1 and T2 localized prostate cancer were judged to be candidates for TRUS guided interstitial implant. Conscious sedation consisted of intravenous morphine (12-22 mg) and versed (6-14 mg), or intravenous demerol (50-225 mg) and versed (3-12 mg). Local anesthetic was given with a mixture of 1% lidocaine, 0.25% marcaine, 1:100,000 epinephrine, and 4% sodium bicarbonate neutralizing solution (20-120 cc). Local anesthesia was given to a 5 x 5 cm perineal area to a depth of 10 cm under TRUS guidance. The implants were placed under mobile multi-plane prostate template (Radiation Therapy Products Prostate Template) guidance using from 3 to 4 planes, and 12 to 22 needles. Needle spacing was 1.0 cm. The implant procedure included sigmoidoscopy and cystoscopy.
Abstracts / Brachytherapy 9 (2010) S23eS102
equivalent uniform dose (EUD) were calculated for the range of parameter values. Results: For the limited range of radius relevant to ABPI balloon based brachytherapy, a phenomenological parameterization g(r) can be established. Over the range of parameterizations from 192Ir to 103Pd DHI decreases with decreasing energy. The relationship between DHI and EUD is presented as a function of energy parameterization as well as parameters relating calculation of EUD. Conclusions: The choice of device used for APBI balloon-based brachytherapy will have an effect on related dosimetric quantities. The dependence of these effects on balloon size and device energy were presented in a manner that can be applied to new sources or devices as they come on the market. Comparing outcomes of patients receiving APBI at different energies offers an opportunity to determine which dosimetric quantities are related to outcome. The lower values of the DHI metric has been associated with poorer outcome. Using lower energy sources will produce lower values of DHI which could reasonably be expected to adversely affect outcome.
PO32 Analysis of Dosimetric Quantities Associated with Partial Breast Brachytherapy Desmond A. O’Farrell, M.Sc.1, Alexandra J. Stewart, M.D.2, Phillip M. Devlin, M.D.1, Robert A. Cormack, Ph.D.1 1Radiation Oncology, Dana-Farber Cancer Institute/Brigham and Women’s Hospital, Boston, MA; 2Radiation Oncology, Royal Surrey County Hospital, Guildford, United Kingdom. Purpose: Radiation dose to the heart and lung are a concern in accelerated partial breast irradiation (APBI). This work presents an analysis of the metrics inherent to high-dose-rate APBI using a 192Ir brachytherapy source. Materials and Methods: Seven patients, who were simulated in both supine and prone position for XRT, were contoured. Dose to the heart and lung were calculated for all potential dwell locations within the contoured breast for a range of potential dwell times. Summary volume and dose metrics were calculated for heart and lung as function of distance to the normal structures. The distribution of distances was then compared for the prone and supine patients. Results: Upper bounds on metrics as a function of distance were evaluated for all patients. Upper bounds as a function of distance can be parameterized, but patient anatomy variations prevent the creation of a generalized bound on the dose quantities such as D10cc or volume metrics such as V10Gy. The characterization provides a measure of the normal tissue dose parameters that are achievable as a function of dmin. While prone position shift the distribution of lung to breast distances towards greater value, the distribution of heart to breast distances is shifted to smaller distances. Conclusions: Characteristic curves of the achievable volume metrics as a function of minimum distance from implant to normal structures are presented. These curves may be helpful in the decision to use APBI brachytherapy based on the location of the cavity. The choice of treatment position affects the distribution of breast tissue, though the effect on distance to heart and lung differs.
PO33 The Role of the Brachytherapy Specialist in Prostate Brachytherapy Paul W. Mueller, B.S., R.T.T., Thomas G. Shanahan, M.D., Yaxiang Yang, Ph.D., Ray R. Capestrain, M.S., Randy B. Maxey, M.S. Radiation Oncology, Memorial Medical Center, Springfield, IL. Purpose: A radiation therapist with additional training in fluoroscopy, ultrasound (both for volume study and intraoperative), seed ordering and assay quality assurance, intraoperative assistance, and radiation safety procedures could offer a major benefit in continuity of care and relieve time requirements of other ancillary staff. We review the role and value of a brachytheray specialist in a large community prostate brachytherapy practice.
Materials and Methods: A position of brachytherapy specialist was created in 1999 to combine numerous job responsibilities to a single individual with the goal of maximizing efficiency of time, continuity of care, and maximizing radiation procedural safety. From 1999-2009, 1200 patients were implanted in a single institution with the benefits of a brachtherapy specialist combining the roles of radiation physicist, ultrasonogragher, fluoroscopy technician, and scrub nurse. Day 0 CT dosimetry was obtained within 3 hours in each patient with the urinary catheter in place. Results: Main operating room time was less than one hour and total physicist’s time was 30 minutes per patient. Seed counts were maintained throughout the procedure. Conclusions: The role of the brachytherapist can add to the quality and efficiency of the prostate brachytherapy team. In this article we review our experince and many of the benefits of a brachytherapy specialist to a busy community practice.
PO34 Dosimetric Evaluation of Structural Modifications Made to a Currently Used 125I Seed for Prostate Brachytherapy Jose L. Garcia Ramirez, M.S., Kevin Moore, Ph.D., Olga Pechnaya, Ph.D. Radiation Oncology, Washington University School of Medicine St. Louis, St. Louis, MO. Purpose: To determine the dosimetric differences between a standard ‘‘bare’’ IsoAid Advantage 125IÔ seed (model IAI-125A) and AnchorSeedÔ, which consists of a standard IAI-125A seed surrounded by bands of suture-like material. Materials and Methods: Two sources with equivalent seed activity were acquired from the manufacturer. Dose calibrator and relative film dosimetry measurements were performed. Results: Measured air-kerma strength (Sk) values of the two sources were found to be within 0.5%. Relative film dosimetry indicated agreement within 1%/1mm in the dose distribution. Conclusions: The new modifications made to the current source do not alter the dosimetric characteristics of the seed model. The dosimetric data currently used should not be changed.
PROSTATE POSTERS ThursdayeSaturday PO35 Interstitial High-Dose-Rate Brachytherapy under Local Anesthesia for Early Stage Prostate Cancer: A Report of 504 Cases Rufus J. Mark, M.D.1, Paul J. Anderson, M.D.1, Robin S. Akins, M.D.2, Murali Nair, Ph.D.1 1Radiation Oncology, Joe Arrington Cancer Center, Lubbock, TX; 2Radiation Oncology, Wilford Hall Medical Center, Lackland Airforce Base, TX. Purpose: Transrectal ultrasound (TRUS)- guided interstitial implant for prostate cancer using low-dose-rate (LDR) and high-dose-rate (HDR) techniques has been reported with results comparing very favorably to external beam radiation therapy. TRUS interstitial implant of the prostate has been traditionally performed under general or spinal anesthetic in an operating room. We report our results with a technique performed under local anesthesia in a department procedure room. Materials and Methods: Patients with T1 and T2 localized prostate cancer were judged to be candidates for TRUS guided interstitial implant. Conscious sedation consisted of intravenous morphine (12-22 mg) and versed (6-14 mg), or intravenous demerol (50-225 mg) and versed (3-12 mg). Local anesthetic was given with a mixture of 1% lidocaine, 0.25% marcaine, 1:100,000 epinephrine, and 4% sodium bicarbonate neutralizing solution (20-120 cc). Local anesthesia was given to a 5 x 5 cm perineal area to a depth of 10 cm under TRUS guidance. The implants were placed under mobile multi-plane prostate template (Radiation Therapy Products Prostate Template) guidance using from 3 to 4 planes, and 12 to 22 needles. Needle spacing was 1.0 cm. The implant procedure included sigmoidoscopy and cystoscopy.