Report to the Aapm Radiation Therapy Committee

RPC Report to the AAPM Radiation Therapy Committee

Report 108

REPORT TO THE AAPM RADIATION THERAPY COMMITTEE

Report No. 108 October 1, 2000 – January 31, 2001

PERSONNEL

Geoffrey S. Ibbott, Ph.D. came on staff January 8, 2001, as Chief of the Section of Outreach Physics and Associate Director of the RPC. William F. Hanson Ph.D. is scheduled to retire August 31, 2001. Between now and then Dr. Ibbott will assume responsibilities as Director of the RPC and PI on the RPC grants and contracts. The transfer of responsibility has begun.

We are recruiting for three new physicists:

· Junior Medical Physicist: We have made an offer to a recent graduate of an accredited Medical Physics program, with two years of clinical experience. The physicist has indicated serious interest, but we have no formal acceptance. We hope to have this physicist on board by June 1, 2001.

· Junior Medical Physicist: An ad has been placed in the AAPM Placement bulletin for this position. A MS level is preferred; however, we will consider entry level Ph.D. We have several potentials under consideration.

· Associate Director of the RPC: This position requires a Ph.D. and 5 years of experience. We will pursue this as Geoff gets more established.

GRANT ACTIVITIES

The RPC major grant began its second of 5 years on Jan 1, 2001.

The Advanced Technology subcontract with the Image Guided Radiation Therapy Quality Assurance Center (IGRTQAC) in St. Louis, begins the last of three years on April 1, 2001.

The COMS grant has been converted to a sub-contract with the COMS PI (University of Pennsylvania). It is designed to support a graduate student to recalculate the dose to critical structures for patients treated with 125I implants.

STUDY GROUP ACTIVITIES

Pre-approval Processes:

· RTOG protocol P0019, radioactive implants for prostate therapy. The RPC is pre-approving institutions to participate. The procedures and criteria are the same as those for the previous Phase II study (protocol 9805). We have three applications in house.

· RTOG protocol H0022, IMRT for head and neck cancer. The pre-approval process is two fold:

§ The institution is required to electronically transmit radiotherapy data to the IGRTQAC in St. Louis.

§ The institution is required to successfully plan and treat the IMRT Head and Neck phantom from the RPC.

· RTOG protocol 95-17: The use of a breast implant as sole therapy for Stage I and II breast carcinoma. An abstract for the 2001 AAPM meeting has been prepared discussing the dose specification and Quality Assurance Procedures for this study. Dr Hanson is the primary author. Comprehensive QA resulted in very compliant treatments, only 4 of 100 patients were evaluated as minor variations from the protocol and none as major deviations from the protocol. This study used ICRU Report 58 specifications. The Dose Homogeneity ratio (the ratio of prescribed dose to mean central dose) was 0.83 ± 0.06% (1s).

Other:

· SWOG Intergroup Protocol S9927, breast treatment allowing everything from simple parallel opposed, through electron treatments, to conformal therapy. SWOG has agreed to have us review these patients. Several patients have been entered onto the study, but we have yet to receive any patients. We anticipate up to 1500 patients, so will consider a method of sampling.

· SWOG TBI Survey: We have received data on TBI procedures for 25 SWOG institutions. The data are under review and will be presented at spring SWOG meeting, summarizing the way that TBI is done and attempting to answer the question from SWOG concerning the diversity of treatments used. This may lead to SWOG guidelines for future protocols.

· RTOG protocol 9406, Conformal therapy for Prostate treatment. Nearly 1100 patients have been treated on this protocol. The 3-D QA Center in St Louis (now the IQRTQAC) has extensive radiotherapy data. The RPC plans a study to evaluate the correctness of these data. We are performing a pilot study of MDACC patients entered onto this study to see of we can evaluate the dose actually delivered from the data at the IGRTQAC. We will use our MDACC pilot, combined with error rates we have from earlier studies, to propose an ancillary study to RTOG.

· GOG has two new proposals that we are dealing with. (1)They wish to include Syed applications as acceptable replacements for conventional Tandem and Ovoid treatment for GYN patients. (2) They also wish to implement Image Based 3-D treatment planning for GYN implants. Both are in reasonably early discussions at this time.

INTERACTION WITH THE SUBCOMMITTEE ON LOW-ENERGY INTERSTITIAL BRACHYTHERAPY DOSIMETRY

The RPC was identified as the principal contact for questions about low-energy brachytherapy sources in the AAPM’s advice to physicists (“Important Notice for Radiation Therapy Physicists using 125I or 103 Pd Brachytherapy Sources.” AAPM Subcommittee on Low-Energy Interstitial Brachytherapy Dosimetry. Letter to membership, August 8, 2000.) Since publication of the letter, the RPC has received numerous calls and emails regarding the changes in calibration standards and dose rate constants.

The response of the RPC has been to confirm, on the basis of published reports and direct contacts, that the information provided by the manufacturers has been relayed correctly from the dosimetry consultants and should be implemented. We have advised a number of physicists of these changes, and have assisted them to implement the changes in their clinic.

The RPC has also published on its web site a statement identifying the iodine and palladium sources that appear to meet the AAPM Prerequisites ("Dosimetric prerequisites for routine clinical use of new low energy photon interstitial brachytherapy sources: Recommendations of the American Association of Physicists in Medicine Radiation Therapy Committee". Med. Phys., 25, 2269-2270 (1998)). In addition, the RPC is preparing a spreadsheet identifying the seeds affected by the dosimetry changes, the magnitude and impact of the changes, and the particulars of the transfer of the calibration standard from NIST to the ADCLs. We have not decided at this point if or how to publish this information.

The AAPM advice letter stated “In the near future, the AAPM, together with the manufacturers of the affected sources, will conduct a coordinated program to advise you of any necessary changes.” Several manufactures have informed their customers that they have instituted a change, and have provided dosimetric information both to their customers and to the ADCLs. However, several physicists have expressed concern that the notifications did not have the AAPM imprimatur. They point out that the AAPM advice letter implies that the AAPM will participate in the notifications. It may be appropriate for the AAPM to revise the advice published on its web page to indicate that manufacturers are now providing these notifications, and that more detail may be obtained from the RPC.

IMPLEMENTATION OF TG-51

1. The data from the RPC’s and Marilyn Stovall’s RDS TLD services indicate that approximately 7-8% of the institutions in the USA have switched to TG-51 after 1-½ years. The TG-51 switchover rate is running at about half of what it was for TG-21 at this same time after publication.

2. We continue to give seminars and workshops on how to implement TG-51 and areas of potential problems. To date we have given 10 workshops and 23 presentations. The most recent was to the SEAAPM Spring meeting in Atlanta.

3. One can find a great deal of useful information about TG-51 on the RPC’s website, http:\\rpc.mdanderson.org. There are instructional videos, PowerPoint presentations, drylab exercises with answers, abstracts and publications from the RPC.

4. We have two TG-51 related manuscripts being prepared:

· Expected TG51/TG21 ratios for 11 cylindrical chambers and 7 parallel plate chambers based on calculations, and

· Expected differences between cylindrical and parallel plate chambers based on measurement.

5. All of the RPC on-site dosimetry review visits are conducted using the TG-51 protocol. As a courtesy to the institution, we also provide the TG-21 output for the reference field size. The majority of the output discrepancies noted are for the electron energies where the difference between the protocols is slightly greater.

6. The visits also serve to educate the physicist as to how to implement TG-51. In addition, we continue to field numerous phone calls from physicists who are trying to implement TG-51 and are having problems or are getting unexpected results.

ANTHROPOMORPHIC PHANTOMS

As part of the RPC’s QA activities and our commitment to the Advanced Technology Consortium, we continue to employ and develop anthropomorphic phantoms that can be sent to institutions to verify the dose delivery for a specific treatment site or modality. All of the phantoms have the same general design, i.e., they are water fillable, have dosimetry and imaging inserts (except the breast phantom), heterogeneous structures and use TLD and film as dosimeters. We currently have 5 phantoms built and being used or tested.

1. The stereotactic head phantom has been in use for some years now. We have 5 of these phantoms in use.

2. The IMRT Head and Neck phantom was built as part of the QA and pre-approval process for a specific RTOG protocol (H0022). It has been built and is being shipped to several institutions for testing. Four more of these phantoms have been built and are awaiting commissioning.

3.
The heterogeneous lung phantom has been built and is in the commissioning phase. This phantom is a part of a MS student’s work and he is concentrating on ways to minimize the dose needed to get reliable results with the radiochromic film.

4. The IMRT pelvic phantom has been built and the commissioning work is finished. This phantom is currently being used at Stoneybrook with a bang/gel dosimeter as part of a collaboration between them and the RPC. This phantom was also a MS project and a good deal of work has gone into the development of DAH’s to assess planar coverage of the target and critical structures.

5. The breast phantom is built and is undergoing testing. It uses regular x-ray film and we are working on the film analysis aspects of the phantom measurements.

PARTICIPANT FEE

Institutions invoiced FY00-01 1116

Canceled/Inactive 27

Invoiced by RDS 12

Institutions paid 857 (80%)

INTERNATIONAL ACTIVITIES

The IAEA Contract, to provide on-site evaluation of institutions in Latin America and the Caribbean with suspected dosimetry problems (from IAEA TLD Program), has been extended another 2 years and an additional $30,000.

PUBLICATIONS AND ABSTRACTS

Publications Accepted/Published (1999-2001):

1) Cho, S.H., Lowenstein, J.R., Balter, P.A., Wells, N.H., and Hanson, W.F. Comparison between TG-51 and TG-21: Calibration of photon and electron beams in water using cylindrical chambers. J. of Applied Clinical Medical Physics 1:108-115, 2000

2) Williamson, J., Coursey, B.M., DeWerd, L.A., Hanson, W.F., Nath, R., Rivard, M.J., Ibbott, G. Recommendations of the American Association of Physicists in Medicine on 103Pd interstitial source calibration and dosimetry: Implications for dose specification and prescription. Medical Physics 27:634-642, 2000.

3) Almond, P.R., Biggs, P.J., Coursey, B.M., Hanson, W.F., Huq, M.S., Nath, R., Rogers, D.W.O. AAPM’s TG-51 protocol for clinical reference dosimetry of high-energy photon and electron beams, Medical Physics 26:1847-1870, 1999.

4) Cho, S.H., Muller-Runkel, R., and Hanson W.F.: Determination of the tissue attenuation factor along two major axes of a high dose rate (HDR) Ir-192 source. Medical Physics 26:1492-1497, 1999.

5) Cho, S. H. and Reece, W. D. The Monte Carlo calculations of the dose backscatter factor for monoenergetic electrons. Phys. Med. Biol. 44(1):13-26, 1999.

6) Williamson, J.F., Coursey, B.M., DeWerd, L.A., Hanson, W.F., Nath, R., and Ibbott, G.: Guidance to users of Nycomed Amersham and North American Scientific, Inc., I-125 interstitial sources: dosimetry and calibration changes. Medical Physics 26:570-573, 1999.

LETTER TO THE EDITOR

1) Ibbott, G.S. and Nath, R.: Dose-rate constant for Imagyn 125I brachytherapy source. Medical Physics 28:1, 2001.

ABSTRACTS SUBMITTED TO AAPM – 2001

1) Krintz, A., Followill, D., Melia, M., and Hanson W.F.: A Reanalysis of the Collaborative Ocular Melanoma Study Medium Tumor Trial Eye Plaque Dosimetry.

2) Radford, D.A., Followill, D.S., Hanson, and W.F.: A Standard Method of Quality Assurance for Intensity Modulated Radiation Therapy of the Prostate.

3) Followill, D.S., Hernandez, N., and Hanson, W.F.: Standard Wedge and Tray Transmission Values for Varian, Seimens, Elekta/Philips Accelerators; A Quality Assurance Tool.

4) Tailor, R.C. and Hanson, W.F.: Estimated Absorbed - Dose Ratios "TG51/TG21" for Most Commonly Used Cylindrical and Parallel-Plate Ion Chambers over a Range of Photon and Electron Energies.

5) BenComo, J.A., Hernandez, N., and Hanson, W.F.: Problems and Shortcomings of the RPC Remote Monitoring Program of Institutions Dosimetry Data.

6) Balter, P.A., Lowenstein, J.L., and Hanson, W.F.: Electron Calibrations: Parallel Plate Chambers vs. Cylindrical Chambers Using TG-51.

7) Hanson, W.F., Martin, B., Kuske, R., Arthur, D., Rabinovitch, R., White, J., Wilenzick, R. Harris, I., Tailor, R., and Davis, D.: Dose Specification and Quality Assurance of RTOG Protocol 95-17, A Cooperative Group Study of 192Ir Breast Implants as Sole Therapy.

TG-51 WORKSHOPS

William Hanson TG-51 Workshop at Southwest Chapter of AAPM meeting San Antonio

Peter Balter TX. Oct 6-7, 2000.

Jessica Lowenstein

David Followill TG-51 Symposium and Workshop, East Jefferson General Hospital, New

& Peter Balter Orleans, LA, October 12-13, 2000

Peter Balter TG-51 Workshop at the Florida Chapter of AAPM Meeting, Orlando

Jessica Lowenstein Florida, November 10, 2000.

VISITS TO INSTITUTIONS

1. David Followill performed radiological physics measurement and reviewed patient dosimetry at Covenant Cancer Center, Waterloo, Iowa, October 2 - 5, 2000.

2. Peter Balter and Irene Harris participated in the resolution of a problem found through breast patient chart reviews at Oschner Clinic to, New Orleans, Louisiana, October 12 - 13, 2000.

3. Jessica Lowenstein performed radiological physics measurements and reviewed patient dosimetry at Rockingham Memorial Cancer Center, Harrisonburg, Virginia, and at Danville Cancer Center, Danville, Virginia, October 28 - November 3, 2000.

4. Ramesh Tailor performed radiological physics measurements and reviewed patient dosimetry at Cancer Care Center, Rapid City, South Dakota, and at United Medical Center, Minot, North Dakota, November 10 - 16, 2000.

5. Jessica Lowenstein performed radiological physics measurements and reviewed patient dosimetry at the University of California, San Francisco, California, December 9 - 17, 2000.

6. David Followill performed radiological physics measurements and reviewed patient dosimetry at the University of California, San Francisco, California, December 11 - 14, 2000.

Report to the Aapm Radiation Therapy Committee