Medical physicist certification and training program accreditation.

As a profession, medical physics combines an advanced understanding of physics and math with knowledge of biology, anatomy and physiology. Consequently, rigorous education and training is required to assure that medical physicists have the requisite fundamental knowledge, specialized technical skills, and clinical understanding to contribute to the medical care of patients safely. There is, therefore, an interest in standardizing the educational pathways and in developing mechanisms to assure that competency is achieved and maintained. Throughout the world, several countries, regions, and professional organizations have developed mechanisms for accrediting medical physics educational programs, both for didactic work performed in undergraduate or post-graduate settings, and for clinical training conducted in hospitals and clinics. In addition, several national and international programs exist for certifying individual medical physicists. In some cases, once initial certification is achieved, the diplomate enters a program of maintenance of certification, to ensure that the skills obtained during training are not lost over a career. This article explores the differences and similarities in the training program accreditation and physicist certification mechanisms.

"SABER": A new software tool for radiotherapy treatment plan evaluation.

PURPOSE: Both spatial and biological information are necessary in order to perform true optimization of a treatment plan and for predicting clinical outcome. The goal of this work is to develop an enhanced treatment plan evaluation tool which incorporates biological parameters and retains spatial dose information. METHODS: A software system is developed which provides biological plan evaluation with a novel combination of features. It incorporates hyper-radiosensitivity using the induced-repair model and applies the new concept of dose convolution filter (DCF) to simulate dose wash-out effects due to cell migration, bystander effect, and/or tissue motion during treatment. Further, the concept of spatial DVH (sDVH) is introduced to evaluate and potentially optimize the spatial dose distribution in the target volume. Finally, generalized equivalent uniform dose is derived from both the physical dose distribution (gEUD) and the distribution of equivalent dose in 2 Gy fractions (gEUD2) and the software provides three separate models for calculation of tumor control probability (TCP), normal tissue complication probability (NTCP), and probability of uncomplicated tumor control (P+). TCP, NTCP, and P+ are provided as a function of prescribed dose and multivariable TCP, NTCP, and P+ plots are provided to illustrate the dependence on individual parameters used to calculate these quantities. Ten plans from two clinical treatment sites are selected to test the three calculation models provided by this software. RESULTS: By retaining both spatial and biological information about the dose distribution, the software is able to distinguish features of radiotherapy treatment plans not discernible using commercial systems. Plans that have similar DVHs may have different spatial and biological characteristics and the application of novel tools such as sDVH and DCF within the software may substantially change the apparent plan quality or predicted plan metrics such as TCP and NTCP. For the cases examined, both the calculation method and the application of DCF can change the ranking order of competing plans. The voxel-by-voxel TCP model makes it feasible to incorporate spatial variations of clonogen densities (n), radiosensitivities (SF2), and fractionation sensitivities (alpha/beta) as those data become available. CONCLUSIONS: The new software incorporates both spatial and biological information into the treatment planning process. The application of multiple methods for the incorporation of biological and spatial information has demonstrated that the order of application of biological models can change the order of plan ranking. Thus, the results of plan evaluation and optimization are dependent not only on the models used but also on the order in which they are applied. This software can help the planner choose more biologically optimal treatment plans and potentially predict treatment outcome more accurately.

The role of medical physicists and the AAPM in the development of treatment planning and optimization.

Developments in radiotherapy treatment planning and optimization by medical physicists and the American Association of Physicists in Medicine are reviewed, with emphasis on recent work in optimization. It is shown that medical physicists have played a vital role in the creation of innovative treatment planning techniques throughout the past century, most significantly since the advent of computerized tomography for three-dimensional (3D) imaging and high-powered computers capable of 3D planning and optimization. Some early advances in 3D planning made by physicists include development of novel planning algorithms, beam's-eye-view, virtual simulation, dose-volume histogram analysis tools, and bioeffect modeling. Most of the recent developments have been driven by the need to develop treatment planning for conformal radiotherapy, especially intensity modulated radiation therapy. These advances include inverse planning, handling the effects of motion and uncertainty, biological planning, and multicriteria optimization.

Intensity modulated neutron radiotherapy for the treatment of adenocarcinoma of the prostate.

PURPOSE: This study investigates the enhanced conformality of neutron dose distributions obtainable through the application of intensity modulated neutron radiotherapy (IMNRT) to the treatment of prostate adenocarcinoma. METHODS AND MATERIALS: An in-house algorithm was used to optimize individual segments for IMNRT generated using an organ-at-risk (OAR) avoidance approach. A number of beam orientation schemes were investigated in an attempt to approach an optimum solution. The IMNRT plans were created retrospectively for 5 patients previously treated for prostate adenocarcinoma using fast neutron therapy (FNT), and a comparison of these plans is presented. Dose distributions and dose-volume histograms (DVHs) were analyzed and plans were evaluated based on percentage volumes of rectum and bladder receiving 95%, 80%, and 50% (V(95), V(80), V(50)) of the prescription dose, and on V(60) for both the femoral heads and GM(muscle) group. RESULTS: Plans were normalized such that the IMNRT DVHs for prostate and seminal vesicles were nearly identical to those for conventional FNT plans. Use of IMNRT provided reductions in rectum V(95) and V(80) of 10% (2-27%) and 13% (5-28%), respectively, and reductions in bladder V(95) and V(80) of 12% (3-26%) and 4% (7-10%), respectively. The average decrease in V(60) for the femoral heads was 4.5% (1-18%), with no significant change in V(60) for the GM(muscle) group. CONCLUSIONS: This study provides the first analysis of the application of intensity modulation to neutron radiotherapy. The IMNRT technique provides a substantial reduction in normal tissue dose in the treatment of prostate cancer. This reduction should result in a significant clinical advantage for this and other treatment sites.