Online Adaptive MRI-Guided Stereotactic Body Radiotherapy for Pancreatic and Other Intra-Abdominal Cancers.

A 1.5T MRI combined with a linear accelerator (Unity®, Elekta; Stockholm, Sweden) is a device that shows promise in MRI-guided stereotactic body radiation treatment (SBRT). Previous studies utilized the manufacturer's pre-set MRI sequences (i.e., T2 Weighted (T2W)), which limited the visualization of pancreatic and intra-abdominal tumors and organs at risk (OAR). Here, a T1 Weighted (T1W) sequence was utilized to improve the visualization of tumors and OAR for online adapted-to-position (ATP) and adapted-to-shape (ATS) during MRI-guided SBRT. Twenty-six patients, 19 with pancreatic and 7 with intra-abdominal cancers, underwent CT and MRI simulations for SBRT planning before being treated with multi-fractionated MRI-guided SBRT. The boundary of tumors and OAR was more clearly seen on T1W image sets, resulting in fast and accurate contouring during online ATP/ATS planning. Plan quality in 26 patients was dependent on OAR proximity to the target tumor and achieved 96 ± 5% and 92 ± 9% in gross tumor volume D90% and planning target volume D90%. We utilized T1W imaging (about 120 s) to shorten imaging time by 67% compared to T2W imaging (about 360 s) and improve tumor visualization, minimizing target/OAR delineation uncertainty and the treatment margin for sparing OAR. The average time-consumption of MRI-guided SBRT for the first 21 patients was 55 ± 15 min for ATP and 79 ± 20 min for ATS.

An introduction to key performance indicators for medical physicists.

Qualified medical physicists (QMPs) are in a unique position to influence the creation and application of key performance indicators (KPIs) across diverse practices in health care. Developing KPIs requires the involvement of stakeholders in the area of interest. Fundamentally, KPIs should provide actionable information for the stakeholders using or viewing them. During development, it is important to strongly consider the underlying data collection for the KPI, making it automatic whenever possible. Once the KPI has been validated, it is important to setup a review cycle and be prepared to adjust the underlying data or action levels if the KPI is not performing as intended. Examples of specific KPIs for QMPs of common scopes of practice are provided to act as models to aid in implementation. KPIs are a useful tool for QMPs, regardless of the scope of practice or practice environment, to enhance the safety and quality of care being delivered.

Dosimetric benefits of dynamic conformal arc therapy-combined with active breath-hold in lung stereotactic body radiotherapy.

To test the hypothesis that dynamic conformal arc therapy (DCAT) in Monaco, compared with volumetric modulated arc therapy (VMAT), maintains plan quality with higher delivery efficiency for lung stereotactic body radiotherapy (SBRT) and to investigate dosimetric benefits of DCAT with active breath-hold (DCAT+ABH), compared with free-breathing (DCAT+FB) for varying tumor sizes and motions. Fifty DCAT plans were used for lung SBRT. Randomly selected 17 DCAT plans were evaluated with respect to the retrospectively generated volumetric modulated arc therapy (VMAT) plans. The maximum dose at 2 cm from planning target volume (PTV) in any direction (D2cm/Rx), the ratio of 50% prescription isodose volume to the PTV (R50%), conformity index (CI), the lung volume receiving ≥20 Gy (V20), and monitor unit (MU) were evaluated. A t-test was used to evaluate the difference of plan quality between DCAT and VMAT. Internal target volume (ITV)/integrated-gross target volume (GTV) attributed by intra-fraction motion and lung V20 were stratified for DCAT+ABH and DCAT+FB across varying GTVs. DCAT maintained plan quality (p = 0.154 for D2cm/Rx, p = 0.089 for R50%, p = 0.064 for CI, and p = 0.780 for lung V20) while reducing MUs up to 30% (p <0.001) from 2748 MU (VMAT) to 1868 MU (DCAT). DCAT+ABH, compared to DCAT+FB, reduced tumor motion, resulting in 19% volume reduction of PTV and 60% reduction in lung V20, on average. The difference in lung V20 between DCAT+ABH and DCAT+FB increased as the target size increased. The DCAT is a favorable approach compared with VMAT. These results support the utility of DCAT as a routine planning platform for lung SBRT, especially when utilized with respiratory motion management using the ABH.

Report of Task Group 201 of the American Association of Physicists in Medicine: Quality management of external beam therapy data transfer.

With the advancement of data-intensive technologies, such as image-guided radiation therapy (IGRT) and intensity-modulated radiation therapy (IMRT), the amount and complexity of data to be transferred between clinical subsystems have increased beyond the reach of manual checking. As a result, unintended treatment deviations (e.g., dose errors) may occur if the treatment system is not closely monitored by a comprehensive data transfer quality management program (QM). This report summarizes the findings and recommendations from the task group (TG) on quality assurance (QA) of external beam treatment data transfer (TG-201), with the aim to assist medical physicists in designing their own data transfer QM. As a background, a section of this report describes various models of data flow (distributed data repositories and single data base systems) and general data test characteristics (data integrity, interpretation, and consistency). Recommended tests are suggested based on the collective experience of TG-201 members. These tests are for the acceptance of, commissioning of, and upgrades to subsystems that store and/or modify clinical treatment data. As treatment complexity continues to evolve, we will need to do and know more about ensuring the quality of data transfers. The report concludes with the recommendation to move toward data transfer open standards compatibility and to develop tools that automate data transfer QA.

AAPM medical physics practice guideline 10.a.: Scope of practice for clinical medical 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 (MPPG) 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 radiation requires specific training, skills, and techniques as described in each document. As the review of the previous version of AAPM Professional Policy (PP)-17 (Scope of Practice) progressed, the writing group focused on one of the main goals: to have this document accepted by regulatory and accrediting bodies. After much discussion, it was decided that this goal would be better served through a MPPG. To further advance this goal, the text was updated to reflect the rationale and processes by which the activities in the scope of practice were identified and categorized. Lastly, the AAPM Professional Council believes that this document has benefitted from public comment which is part of the MPPG process but not the AAPM Professional Policy approval process. The following terms are used in the AAPM's MPPGs: Must and Must Not: Used to indicate that adherence to the recommendation is considered necessary to conform to this practice guideline. Should and Should Not: Used to indicate a prudent practice to which exceptions may occasionally be made in appropriate circumstances.

Redefining and reinvigorating the role of physics in clinical medicine: A Report from the AAPM Medical Physics 3.0 Ad Hoc Committee.

Derived from 2 yr of deliberations and community engagement, Medical Physics 3.0 (MP3.0) is an effort commissioned by the American Association of Physicists in Medicine (AAPM) to devise a framework of strategies by which medical physicists can maintain and improve their integral roles in, and contributions to, health care and its innovation under conditions of rapid change and uncertainty. Toward that goal, MP3.0 advocates a broadened and refreshed model of sustainable excellence by which medical physicists can and should contribute to health care. The overarching conviction of MP3.0 is that every healthcare facility can benefit from medical physics and every patient's care can be improved by a medical physicist. This large and expansive challenge necessitates a range of strategies specific to each area of medical physics: clinical practice, research, product development, and education. The present paper offers a summary of the Phase 1 deliberations of the MP3.0 initiative pertaining to strategic directions of the discipline primarily but not exclusively oriented toward the clinical practice of medical physics in the United States.

Clinical implementation and evaluation of the Acuros dose calculation algorithm.

PURPOSE: The main aim of this study is to validate the Acuros XB dose calculation algorithm for a Varian Clinac iX linac in our clinics, and subsequently compare it with the wildely used AAA algorithm. METHODS AND MATERIALS: The source models for both Acuros XB and AAA were configured by importing the same measured beam data into Eclipse treatment planning system. Both algorithms were validated by comparing calculated dose with measured dose on a homogeneous water phantom for field sizes ranging from 6 cm × 6 cm to 40 cm × 40 cm. Central axis and off-axis points with different depths were chosen for the comparison. In addition, the accuracy of Acuros was evaluated for wedge fields with wedge angles from 15 to 60°. Similarly, variable field sizes for an inhomogeneous phantom were chosen to validate the Acuros algorithm. In addition, doses calculated by Acuros and AAA at the center of lung equivalent tissue from three different VMAT plans were compared to the ion chamber measured doses in QUASAR phantom, and the calculated dose distributions by the two algorithms and their differences on patients were compared. Computation time on VMAT plans was also evaluated for Acuros and AAA. Differences between dose-to-water (calculated by AAA and Acuros XB) and dose-to-medium (calculated by Acuros XB) on patient plans were compared and evaluated. RESULTS: For open 6 MV photon beams on the homogeneous water phantom, both Acuros XB and AAA calculations were within 1% of measurements. For 23 MV photon beams, the calculated doses were within 1.5% of measured doses for Acuros XB and 2% for AAA. Testing on the inhomogeneous phantom demonstrated that AAA overestimated doses by up to 8.96% at a point close to lung/solid water interface, while Acuros XB reduced that to 1.64%. The test on QUASAR phantom showed that Acuros achieved better agreement in lung equivalent tissue while AAA underestimated dose for all VMAT plans by up to 2.7%. Acuros XB computation time was about three times faster than AAA for VMAT plans, and computation time for other plans will be discussed at the end. Maximum difference between dose calculated by AAA and dose-to-medium by Acuros XB (Acuros_Dm,m ) was 4.3% on patient plans at the isocenter, and maximum difference between D100 calculated by AAA and by Acuros_Dm,m was 11.3%. When calculating the maximum dose to spinal cord on patient plans, differences between dose calculated by AAA and Acuros_Dm,m were more than 3%. CONCLUSION: Compared with AAA, Acuros XB improves accuracy in the presence of inhomogeneity, and also significantly reduces computation time for VMAT plans. Dose differences between AAA and Acuros_Dw,m were generally less than the dose differences between AAA and Acuros_Dm,m . Clinical practitioners should consider making Acuros XB available in clinics, however, further investigation and clarification is needed about which dose reporting mode (dose-to-water or dose-to-medium) should be used in clinics.

A report from the AAPM Subcommittee on Guidelines for Competency Evaluation for Clinical Medical Physicists in Radiation Oncology.

The goal of this report is to provide a framework from which an institution can develop a competency and credentialing program. It is not intended to be adopted as written, but rather as a list of suggestions from which the institution develops their program. A clear distinction should be made between the initial evaluation of the competency of new staff (credentialing) and the ongoing verification of the competency of existing staff. Furthermore, whenever new technologies are imple-mented, the entire staff would be subject to the credentialing process. Competencies involve the ongoing verification of the performance of a procedure according to the established policies and procedures at a facility. This can be done by audits of work product, direct observation of performance, self-evaluation, or testing. PACS number(s): 87.10.-e, 87.90.+y