American Brachytherapy Society consensus guidelines for transrectal ultrasound-guided permanent prostate brachytherapy

For commissioning a linear accelerator for clinical use, medical physicists are faced with many challenges including the need for precision, a variety of testing methods, data validation, the lack of standards, and time constraints. Since commissioning beam data are treated as a reference and ultimately used by treatment planning systems, it is vitally important that the collected data are of the highest quality to avoid dosimetric and patient treatment errors that may subsequently lead to a poor radiation outcome. Beam data commissioning should be performed with appropriate knowledge and proper tools and should be independent of the person collecting the data. To achieve this goal, Task Group 106 (TG-106) of the Therapy Physics Committee of the American Association of Physicists in Medicine was formed to review the practical aspects as well as the physics of linear accelerator commissioning. The report provides guidelines and recommendations on the proper selection of phantoms and detectors, setting up of a phantom for data acquisition (both scanning and no-scanning data), procedures for acquiring specific photon and electron beam parameters and methods to reduce measurement errors (<1%), beam data processing and detector size convolution for accurate profiles. The TG-106 also provides a brief.discussion on the emerging trend in Monte Carlo simulation techniques in photon and electron beam commissioning. The procedures described in this report should assist a qualified medical physicist in either measuring a complete set of beam data, or in verifying a subset of data before initial use or for periodic quality assurance measurements. By combining practical experience with theoretical discussion, this document sets a new standard for beam data commissioning.

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Accelerator beam data commissioning equipment and procedures: report of the TG-106 of the Therapy Physics Committee of the AAPM.

Tumour and target volumes in permanent prostate brachytherapy: A supplement to the ESTRO/EAU/EORTC recommendations on prostate brachytherapy

Purpose: The American Brachytherapy Society recommends that postprostate implant dosimetry be performed on all patients undergoing transperineal interstitial permanent prostate brachytherapy (TIPPB) utilizing CT scan clinical target volume reconstructions. This study was undertaken to assess the recommended dosimetry parameters from a large cohort of patients undergoing TIPPB that would predict for PSA relapse-free survival (PSA-RFS). Methods and Materials: Seven hundred nineteen consecutive patients with clinical stage T1/T2 adenocarcinoma of the prostate underwent TIPPB using either I-125 or Pd-103. Postimplant dosimetry was performed at 2 to 3 weeks with CT scan 3-dimensional reconstructions obtained on all patients. The D90 and D100 doses (defined as the minimum dose covering 90% and 100% of the prostate volume, respectively) and the V100 (defined as the percent of the prostate receiving 100% of the prescribed dose) were obtained for each patient. Regression analysis was performed on the D90 dose, D100 dose, and V100 to test for cutoff points that would predict for PSA-RFS, defined by a modification of the American Society for Therapeutic Radiology and Oncology consensus panel statement. A cutoff value was found and was subjected to subset analysis to assess for its robustness. Treatment-related factors were tested for their ability to achieve dosimetry at or above the cutoff dose. Results: The median follow-up from this cohort is 30 months (7–71 months) with a 48-month PSA-RFS of 89.5%. A D90 dose-response cutoff value ≥90% of the prescribed dose was identified. Prostate implants with a D90 dose p = 0.001). No cutoff value was found for the V100 and D100 dose that predicted for PSA-RFS. Using the cutoff value, the D90 dose at 90% of the prescribed dose, a difference in 4-year PSA-RFS survival was identified for patients treated with I-125 ( p = 0.04), Pd-103 ( p = 0.01), TIPPB as monotherapy ( p = 0.001), the addition of hormone therapy ( p = 0.005), and TIPPB without hormone therapy ( p = 0.001). The D90 dose was not significant for the group of patients treated with external beam radiotherapy and TIPPB ( p = 0.15). The only significant finding from Cox regression analysis to predict for a poor D90 dose ( 1.5 ( p = 0.02). Conclusions: The American Brachytherapy Society recommends that postimplant CT-based dosimetry be performed for all patients treated with TIPPB. This prospective study identified that the D90 dose ≥90% of the prescribed dose can be used as a factor for predicting PSA-RFS in patients treated with brachytherapy. A dose-response using the D90 dose was observed for several typical clinical treatment variations used in the practice of TIPPB. Using the D90 dose appears to be a satisfactory parameter for predicting outcome in patients treated with TIPPB.

/pdf/a-comprehensive-review-of-ct-based-dosimetry-parameters-and-5b89agtw68.pdf

A comprehensive review of CT-based dosimetry parameters and biochemical control in patients treated with permanent prostate brachytherapy

For commissioning a linear accelerator for clinical use, medical physicists are faced with many challenges including the need for precision, a variety of testing methods, data validation, the lack of standards, and time constraints. Since commissioning beam data are treated as a reference and ultimately used by treatment planning systems, it is vitally important that the collected data are of the highest quality to avoid dosimetric and patient treatment errors that may subsequently lead to a poor radiation outcome. Beam data commissioning should be performed with appropriate knowledge and proper tools and should be independent of the person collecting the data. To achieve this goal, Task Group 106 TG-106 of the Therapy Physics Committee of the American Association of Physicists in Medicine was formed to review the practical aspects as well as the physics of linear accelerator commissioning. The report provides guidelines and recommendations on the proper selection of phantoms and detectors, setting up of a phantom for data acquisition both scanning and no-scanning data , procedures for acquiring specific photon and electron beam parameters and methods to reduce measurement errors 1% , beam data processing and detector size convolution for accurate profiles. The TG-106 also provides a brief discussion on the emerging trend in Monte Carlo simulation techniques in photon and electron beam commissioning. The procedures described in this report should assist a qualified medical physicist in either measuring a complete set of beam data, or in verifying a subset of data before initial use or for periodic quality assurance measurements. By combining practical experience with theoretical discussion, this document sets a new standard for beam data commissioning. © 2008 American Association of Physicists in Medicine. DOI: 10.1118/1.2969070

/pdf/accelerator-beam-data-commissioning-equipment-and-procedures-2kcub464cn.pdf

[Accelerator beam data commissioning equipment and procedures: report of the TG-106 of the therapy physics committee of the AAPM].

Purpose: The utilization of transperineal interstitial permanent prostate brachytherapy (TIPPB) is increasing in the United States. Quality assessment of TIPPB is in its infancy, and to date, dosimetric analyses have only been reported from centers with a large experience in prostate brachytherapy. The purpose of this report is to critically analyze the dosimetric coverage achieved following TIPPB in the first 63 cases performed by a multidisciplinary group of investigators with no prior experience with TIPPB. Methods and Materials: The information in this report concerns the first 63 men treated with TIPPB alone at our institution between September 1997 and September 1998. All men were treated similarly, adapting the methods described by Blasko and Grimm. All men were treated with 125 I. The prescription dose was 144 Gy according to the TG43 formalism. TIPPB was performed jointly by a radiation oncologist and a urologist. One month following TIPPB, all men underwent a computed tomography (CT) scan of the pelvis according to a protocol using 3-mm abutting slices. CT images were transferred by a local area network to a commercially available treatment planning system and dose-volume histograms were calculated with 0.5-mm pixel spacing. A variety of dosimetric endpoints were examined. A single measure of dose homogeneity, the dose-homogeneity index (DHI), is defined as the volume within the prostate that receives 100–150% of the prescription dose (144–216 Gy) divided by the volume within the prostate that receives 100% of the prescription dose (144 Gy). Three measures of target (prostate) dosimetric coverage are provided. C100 is defined as the percentage of the prostate volume defined on postimplant CT that receives at least 100% of the prescription dose. C90 and C80 are similar but represent the percentage of the prostate volume that receive 90% and 80% of the prescription dose, respectively. Statistical analyses were performed using commercially available computer software. To investigate any changes with time the first 30 cases (group 1) are compared to cases 31–63 (group 2). All p -values are two-sided. Results: The mean C100, C90, and C80 for all 63 patients were 80.7% (SD 10.1), 85.1% (SD 10.2), and 89.3% (SD 9.5). The quantifiers of implant adequacy were all improved in the most recent 33 patients compared to the first 30 patients, (group 1: C100, 75.8% [SD 12.2], C90 79.9% [SD 11.4], C80 84.3% [SD 11.1]; group 2: C100, 85.2 [SD 7.0], C90 89.9% [SD 5.8], C80 93.8% [SD 4.2]; p p = 0.0001). Using C90 and C80 as the dependent variable produced similar results (C90, p = 0.0001; C80, p = 0.0001). Conclusion: In this single institution experience with the first 63 men receiving TIPPB by a multidisciplinary group of investigators, there is evidence for a learning curve. All quantifiers of implant adequacy improved as clinicians gained experience. In the most recent group of patients, quantifiers of implant adequacy are similar to those reported from other groups with significantly more experience with TIPPB.

Postimplant analysis of transperineal interstitial permanent prostate brachytherapy: evidence for a learning curve in the first year at a single institution.

Three-field isocentric breast irradiation using asymmetric jaws and a tilt board.

A new prototype 6‐MV flattening filter was designed by the manufacturer for use in a popular dual energy linear accelerator. To satisfy the contract demands, this filter was designed to produce a beam whose characteristics matched precisely with those of the 6‐MV beam produced from a single photon peak energy unit from the same manufacturer and already in operation in the department. A single set of 6‐MV dosimetric files for both units can now be maintained. The new filter has forced percent depth values over a wide clinical range of field sizes and depths to agree within 1.3%. Beam profiles now agree to within 1% over the useful area. For wedges with similar wedge angles, transmission factors now agree to within 1%. Standard acceptance testing performance specifications provided by the manufacturer were not adequate for clinical beam matching. The purchase contract for these units included our own specifications, which were more rigid and pertinent to our goal. Details of the effort are discussed.

Mark G. Marshall

Papers

Postimplant analysis of transperineal interstitial permanent prostate brachytherapy: evidence for a learning curve in the first year at a single institution.

Three-field isocentric breast irradiation using asymmetric jaws and a tilt board.

Matching the 6-MV photon beam characteristics of two dissimilar linear accelerators