AAPM Medical physics practice guideline 15.A: Peer review in clinical physics.

The American Association of Physicists in Medicine (AAPM) is a nonprofit professional society whose primary purposes are to advance the science, education, and professional practice of medical physics. The AAPM has more than 8000 members and is the principal organization of medical physicists in the United States. The AAPM will periodically define new practice guidelines for medical physics practice to help advance the science of medical physics and to improve the quality of service to patients throughout the United States. Existing medical physics practice guidelines will be reviewed for the purpose of revision or renewal, as appropriate, on their fifth anniversary or sooner. Each medical physics practice guideline represents a policy statement by the AAPM, has undergone a thorough consensus process in which it has been subjected to extensive review, and requires the approval of the Professional Council. The medical physics practice guidelines recognize that the safe and effective use of diagnostic and therapeutic radiology requires specific training, skills, and techniques, as described in each document. Reproduction or modification of the published practice guidelines and technical standards by those entities not providing these services is not authorized. The following terms are used in the AAPM practice guidelines: Must and Must Not: Used to indicate that adherence to the recommendation is considered necessary to conform to this practice guideline. While must is the term to be used in the guidelines, if an entity that adopts the guideline has shall as the preferred term, the AAPM considers that must and shall have the same meaning. Should and Should Not: Used to indicate a prudent practice to which exceptions may occasionally be made in appropriate circumstances.

Charged particle therapy versus photon therapy for paranasal sinus and nasal cavity malignant diseases: a systematic review and meta-analysis.

BACKGROUND: Malignant tumours arising within the nasal cavity and paranasal sinuses are rare and composed of several histological types, rendering controlled clinical trials to establish the best treatment impractical. We undertook a systematic review and meta-analysis to compare the clinical outcomes of patients treated with charged particle therapy with those of individuals receiving photon therapy. METHODS: We identified studies of nasal cavity and paranasal sinus tumours through searches of databases including Embase, Medline, Scopus, and the Cochrane Collaboration. We included treatment-naive cohorts (both primary and adjuvant radiation therapy) and those with recurrent disease. Primary outcomes of interest were overall survival, disease-free survival, and locoregional control, at 5 years and at longest follow-up. We used random-effect models to pool outcomes across studies and compared event rates of combined outcomes for charged particle therapy and photon therapy using an interaction test. FINDINGS: 43 cohorts from 41 non-comparative observational studies were included. Median follow-up for the charged particle therapy group was 38 months (range 5-73) and for the photon therapy group was 40 months (14-97). Pooled overall survival was significantly higher at 5 years for charged particle therapy than for photon therapy (relative risk 1·51, 95% CI 1·14-1·99; p=0·0038) and at longest follow-up (1·27, 1·01-1·59; p=0·037). At 5 years, disease-free survival was significantly higher for charged particle therapy than for photon therapy (1·93, 1·36-2·75, p=0·0003) but, at longest follow-up, this event rate did not differ between groups (1·51, 1·00-2·30; p=0·052). Locoregional control did not differ between treatment groups at 5 years (1·06, 0·68-1·67; p=0·79) but it was higher for charged particle therapy than for photon therapy at longest follow-up (1·18, 1·01-1·37; p=0·031). A subgroup analysis comparing proton beam therapy with intensity-modulated radiation therapy showed significantly higher disease-free survival at 5 years (relative risk 1·44, 95% CI 1·01-2·05; p=0·045) and locoregional control at longest follow-up (1·26, 1·05-1·51; p=0·011). INTERPRETATION: Compared with photon therapy, charged particle therapy could be associated with better outcomes for patients with malignant diseases of the nasal cavity and paranasal sinuses. Prospective studies emphasising collection of patient-reported and functional outcomes are strongly encouraged. FUNDING: Mayo Foundation for Medical Education and Research.

The inter- and intrafraction reproducibilities of three common IMRT delivery techniques.

PURPOSE: Intensity modulated radiation therapy (IMRT) treatment delivery requires higher precision than conventional 3D treatment delivery because of the sensitivity of the resulting dose to small geometric misalignment of the modulated beamlets. The chosen treatment delivery technique will affect the treatment precision in different ways, based on the characteristics of the delivery method. Delivery using a multileaf collimator (MLC) can reduce treatment time and therapist workload, but typically requires a greater number of monitor units and the fields are prone to both systematic and random leaf positioning errors. An alternative to MLC-based fields, patient specific brass compensators, do not suffer from these leaf positioning errors. In our study, we set out to investigate which delivery method will provide the highest levels of dosimetric reproducibility and the minimum amount of interfraction variability. METHODS: In our study, a seven field IMRT plan for a head and neck treatment was created using the Pinnacle3 treatment planning system and the intensity maps for each field were obtained. The intensity maps of the fields were delivered with a Varian 2100C/D linear accelerator, using solid compensators and sliding window (SW) and step-and-shoot (SS) MLC segments. Three fields were selected from the seven-beam IMRT plan for comparison. Analysis was carried out using the MatriXX ion chamber array, radiochromic film, and Varian dynalog files. RESULTS: Our results show that the error in MLC leaf positioning has no gantry angle dependence. The compensator and SW deliveries showed excellent agreement, even when stricter than usual gamma criteria were applied. However, we noted that under these strict conditions, the SS field had at least ten times more pixels out of range than did the compensators. When using step-and-shoot MLC fields, it was observed that the increase in dose rate or the increase of MU/segment degrades the quality of the plan. Analysis of the dynalog files showed that while each individual field had its own propensity for error, all fields showed the same trend: a greater percentage of time the leaves are out of position as dose rate increases, MUs decrease, or both. CONCLUSIONS: The compensator-based field and both types of MLC-based fields have MatriXX results that are within the clinically acceptable tolerance of 3% dose difference and 2 mm DTA. However, when the criteria are tightened, it becomes evident that the compensators have a definite advantage over their comparable MLC-based competitors in terms of interfraction reproducibility. Fewer monitor units are required to deliver each portal, potentially improving patient outcomes and reducing unwanted side effects to both patients and therapists. In centers without MLC, compensators represent a simple and cost effective way to offer patients state of the art treatment. Based on the results of this study, compensator-based IMRT is a reliable, viable option for use in clinics both with and without MLC-equipped linacs.

Treatment planning and delivery of IMRT using 6 and 18MV photon beams without flattening filter.

In light of the increasing use of intensity modulated radiation therapy (IMRT) in modern radiotherapy practice, the use of a flattening filter may no longer be necessary. Commissioning data have been measured for a Varian 23EX linear accelerator with 6 and 18 MV photon energies without a flattening filter. Measurements collected for the commissioning of the linac included percent depth dose curves and profiles for field sizes ranging from 2 x 2 to 40 x 40 cm(2) as defined by the jaws and multileaf collimator. Machine total scatter factors were measured and calculated. Measurements were used to model the unflattened beams with the Pinnacle(3) treatment planning system. IMRT plans for prostate, lung, brain and head and neck cancer cases were generated using the flattening filter and flattening filter-free beams. From our results, no difference in the quality of the treatment plans between the flat and unflattened photon beams was noted. There was however a significant decrease in the number of monitor units required for unflattened beam treatment plans due to the increase in linac output-approximately two times and four times higher for the 6 and 18 MV, respectively.