Radiological Physics Research Articles

Medical physics personnel for medical imaging: requirements, conditions of involvement and staffing levels-French recommendations.

The French regulations concerning the involvement of medical physicists in medical imaging procedures are relatively vague. In May 2013, the ASN and the SFPM issued recommendations regarding Medical Physics Personnel for Medical Imaging: Requirements, Conditions of Involvement and Staffing Levels. In these recommendations, the various areas of activity of medical physicists in radiology and nuclear medicine have been identified and described, and the time required to perform each task has been evaluated. Criteria for defining medical physics staffing levels are thus proposed. These criteria are defined according to the technical platform, the procedures and techniques practised on it, the number of patients treated and the number of persons in the medical and paramedical teams requiring periodic training. The result of this work is an aid available to each medical establishment to determine their own needs in terms of medical physics.

Teaching Radiologic Physics to Diagnostic Radiology Residents: How We Do It

hour-long lectures, twice a week, outside of the traditional clinicalday, either at 7:00 AM or 5:30 PM. Although this course may have provided good preparation for the physics board exam for some residents, and this was anecdotally the main motivating factor for them, it had a number of apparent limitations. Given its timing and format, the residents viewed this as an exam review course only, and according to at least some prior residents, they felt thattheydidnothavetoworryabout physics ever again after passing the physics board exam. In addition, relegating all physics lectures to 7:00 AM or 5:30 PM symbolized that physicswasnotanimportanttopicin the residency, and that it should not conflict with clinical responsibilities and other educational activities. Of course, the change in the ABR certification process provided the final impetustodoawaywiththisformat. THE PRESENT The current implementation of

VMAT Head and Neck Treatment Delivery: Benchmarking Accuracy of Patient DVH Based QA With Radiological Physics Center (RPC) Head and Neck Phantom Results

VMAT Head and Neck Treatment Delivery: Benchmarking Accuracy of Patient DVH Based QA With Radiological Physics Center (RPC) Head and Neck Phantom Results

Stress Management and Resiliency Training (SMART) Program among Department of Radiology Faculty: A Pilot Randomized Clinical Trial

To test the efficacy of a Stress Management and Resiliency Training (SMART) program for decreasing stress and anxiety and improving resilience and quality of life among Department of Radiology physicians. The study was approved by the institutional review board. A total of 26 Department of Radiology physicians were randomized in a single-blind trial to either the SMART program or a wait-list control arm for 12 weeks. The program involved a single 90-min group session in the SMART training with two follow-up phone calls. Primary outcomes measured at baseline and week 12 included the Perceived Stress Scale, Linear Analog Self-Assessment Scale, Mindful Attention Awareness Scale, and Connor-Davidson Resilience Scale. A total of 22 physicians completed the study. A statistically significant improvement in perceived stress, anxiety, quality of life, and mindfulness at 12 weeks was observed in the study arm compared to the wait-list control arm; resilience also improved in the active arm, but the changes were not statistically significant when compared to the control arm. A single session to decrease stress among radiologists using the SMART program is feasible. Furthermore, the intervention afforded statistically significant and clinically meaningful improvement in anxiety, stress, quality of life, and mindful attention. Further studies including larger sample size and longer follow-up are warranted.

Shifting Focus of Medical Physics Education During Residency Training

Advances in imaging technology depend heavily on the work of physicists, in collaboration with engineers and mathematicians. As radiologists, our profession is firmly based in and dependent on new advances in physics. We are required to have a fundamental knowledge of medical physics to provide optimal patient care in a safe and effective manner by optimizing the risk/benefit ratio involved in the vast array of imaging modalities. The importance of medical physics in radiology is evident in the required radiology resident curriculum devoted to medical physics.

Sharing Knowledge and Integrated Information in Therapeutic Radiological Physics

In this paper a framework for Sharing Knowledge and Integrated Information in Radiotherapy (SKIIR) for medical physicists involved in Therapeutic Radiological Physics is discussed. The proposed SKIIR is mainly designed for sharing knowledge based on specific cases of treating patients with cancer. Integrated Information and Knowledge are captured for storing knowledge and medical information related to the specific cases of interest, in any useful form and format, for the medical physicists. Various patient cases’ descriptions and related documents of primary interest for the medical physicists are stored and organized for future use in a multimedia library including short descriptions, radiotherapy planning, ultrasound, CT and MRI images, statistical information, bibliography, discharge letters, etc. Codification of knowledge and preservation of anonymity is also discussed.

Preliminary evaluation of image quality in a new clinical ToF-PET/MR scanner.

A new ToF-PET/MR scanner has recently been deployed at the University Hospital of Zurich for clinical evaluation purposes. The goal of the present work was to compare the image quality obtained on this system with that of equivalent state-of-the-art standalone scanners. The GE Signa PET/MR is a whole-body scanner combining a 3T wide-bore MR system with a 25 cm PET detector ring based on SiPM technology and mounted on a customized radiofrequency coil. MR image quality of this system was tested by scanning two volunteers: One with a brain protocol and another with a whole-body protocol. The same scans were repeated before and after PET detectors were installed on the system. A baseline measurement was acquired on a Discovery 750w scanner with the same volunteers. PET image quality was tested on patients referred for an FDG PET/CT scan. After 15-20 minutes of PET/CT, the patients were moved to the PET/MR, where an equivalent acquisition was performed. Data were reviewed by nuclear medicine and radiology physicians. As seen in Figure ​Figure1,1, MR image quality in the brain is identical between PET/MR (pre- and post-insert) and MR750w. In whole-body scans, shading on the images due to different receive coil sensitivity were observed. These are explained by the replacement of the bed-mounted posterior array coil by a central matrix array at the scanner iso-center. Figure ​Figure22 illustrates the differences in PET, showing equivalent or better quality in the PET/MR data, despite latter acquisition, justified by the increased sensitivity of the scanner. Figure 1 Coronal 2D MERGE views of a healthy volunteer scanned on a Discovery 750w (left), on the PET/MR before the installation of the PET insert (center) and on the same scanner once the insert was in place and online (right). Figure 2 Three-dimensional maximum intensity projection of a PET/CT acquisition (left) and posterior PET/MR acquisition (right) of the same patient. Our results show that the image quality of clinical MR sequences is not affected by the presence of the PET detector insert. PET image quality shows great promise, but will require further testing to confirm this quantitatively.

On the feasibility of comprehensive high-resolution 3D remote dosimetry.

This study investigates the feasibility of remote high-resolution 3D dosimetry with the PRESAGE®/Optical-CT system. In remote dosimetry, dosimeters are shipped out from a central base institution to a remote institution for irradiation, then shipped back to the base institution for subsequent readout and analysis. Two nominally identical optical-CT scanners for 3D dosimetry were constructed and placed at the base (Duke University) and remote (Radiological Physics Center) institutions. Two formulations of PRESAGE® (SS1, SS2) radiochromic dosimeters were investigated. Higher sensitivity was expected in SS1, which had higher initiator content (0.25% bromotrichloromethane), while greater temporal stability was expected in SS2. Four unirradiated PRESAGE® dosimeters (two per formulation, cylindrical dimensions 11 cm diameter, 8.5-9.5 cm length) were imaged at the base institution, then shipped to the remote institution for planning and irradiation. Each dosimeter was irradiated with the same simple treatment plan: an isocentric 3-field "cross" arrangement of 4 × 4 cm open 6 MV beams configured as parallel opposed laterals with an anterior beam. This simple plan was amenable to accurate and repeatable setup, as well as accurate dose modeling by a commissioned treatment planning system (Pinnacle). After irradiation and subsequent (within 1 h) optical-CT readout at the remote institution, the dosimeters were shipped back to the base institution for remote dosimetry readout 3 days postirradiation. Measured on-site and remote relative 3D dose distributions were registered to the Pinnacle dose calculation, which served as the reference distribution for 3D gamma calculations with passing criteria of 5%/2 mm, 3%/3 mm, and 3%/2 mm with a 10% dose threshold. Gamma passing rates, dose profiles, and color-maps were all used to assess and compare the performance of both PRESAGE® formulations for remote dosimetry. The best agreements between the Pinnacle plan and dosimeter readout were observed in PRESAGE® formulation SS2. Under 3%/3 mm 3D gamma passing criteria, passing rates were 91.5% ± 3.6% (SS1) and 97.4% ± 2.2% (SS2) for immediate on-site dosimetry, 96.7% ± 2.4% (SS1) and 97.6% ± 0.6% (SS2) for remote dosimetry. These passing rates are well within TG119 recommendations (88%-90% passing). Under the more stringent criteria of 3%/2 mm, there is a pronounced difference [8.0 percentage points (pp)] between SS1 formulation passing rates for immediate and remote dosimetry while the SS2 formulation maintains both higher passing rates and consistency between immediate and remote results (differences ≤ 1.2 pp) at all metrics. Both PRESAGE® formulations under study maintained high linearity of dose response (R(2) > 0.996) for 1-8 Gy over 14 days with response slope consistency within 4.9% (SS1) and 6.6% (SS2), and a relative dose distribution that remained stable over time was demonstrated in the SS2 dosimeters. Remote 3D dosimetry was shown to be feasible with a PRESAGE® dosimeter formulation (SS2) that exhibited relative temporal stability and high accuracy when read off-site 3 days postirradiation. Characterization of the SS2 dose response demonstrated linearity (R(2) > 0.998) over 14 days and suggests accurate readout over longer periods of time would be possible. This result provides a foundation for future investigations using remote dosimetry to study the accuracy of advanced radiation treatments. Further work is planned to characterize dosimeter reproducibility and dose response over longer periods of time.

MO‐E‐18C‐03: Incorporating Active Learning Into A Traditional Graduate Medical Physics Course

Purpose:To improve the ability of graduate students to learn medical physics concepts through the incorporation of active learning techniques.Methods:A traditional lecture‐based radiological physics course was modified such that: (1) traditional (two‐hour) lectures were provided online for students to watch prior to class, (2) a student was chosen randomly at the start of each class to give a two minute synopsis of the material and its relevance (two‐minute drill), (3) lectures were significantly abbreviated and remaining classroom time used for group problem solving, and (4) videos of the abbreviated lectures were made available online for review. In the transition year, students were surveyed about the perceived effects of these changes on learning. Student performance was evaluated for 3 years prior to and 4 years after modification.Results:The survey tool used a five point scale from 1=Not True to 5=Very True. While nearly all students reviewed written materials prior to class (4.3±0.9), a minority watched the lectures (2.1±1.5). A larger number watched the abbreviated lectures for further clarification (3.6±1.6) and found it helpful in learning the content (4.2±1.0). Most felt that the two‐minute drill helped them get more out of the lecture (3.9±0.8) and the problem solving contributed to their understanding of the content (4.1±0.8). However, no significant improvement in exam scores resulted from the modifications (mean scores well within 1 SD during study period).Conclusion:Students felt that active learning techniques improved their ability to learn the material in what is considered the most difficult course in the program. They valued the ability to review the abbreviated class lecture more than the opportunity to watch traditional lectures prior to class. While no significant changes in student performance were observed, aptitude variations across the student cohorts make it difficult to draw conclusions about the effectiveness of active learning.

MO‐F‐16A‐08: Have An Impact On More Patients From Your Ideas And Inventions

Purpose:To inform physicists how to obtain an FDA 510(k) clearance for the innovations they use in their facility and to make those ideas widely available to patients throughout the U.S.Methods:Give advice from 20 years experience of assisting in well over 100 successful 510(k) clearances.Results:Learn how to develop a 510(k) submission.Conclusion:Many physicists, physicians and radiation therapists have developed innovations that that are helpful to the patients in their institution. But, many of these innovations deserve to be made available to patients throughout the United States. The author, a Certified Radiological Physicist and former FDA employee, has consulted for over twenty years for inventors, start‐ups and established medical device manufacturers to bring new devices to market in the U.S. and to assist them to established FDA compliant quality systems for manufacturing. In this presentation the audience will learn the important points for deciding to go forward with obtaining a Premarket Notification clearance [also known as a 510(k) clearance] to legally market a medical device in the United States. The FDA has published guidelines for submitting a 510(k) application. However, the methods used to efficiently develop the documentation for submission and to obtain clearance in the shortest possible time comes from the author's experience in assisting well over one hundred successful 510(k) clearances.Whether you want to start your own company or to market your idea to an established medical device manufacturer, the value of your innovation increases with a documented 510(k) clearance from FDA.

SU‐E‐E‐07: When the Old Ways Are the Best Ways: In Defense of Didactic Training

Purpose:Physics education for residents has taken on a more prominent role due to the new ABR examination format. We present a curriculum for a new radiology residency entering its second year. This curriculum favors an extensive traditional didactic teaching approach. The curriculum is designed to minimize the amount of independent learning that is necessary outside the classroomMethods and Materials:idactic training repeats yearly for all four years of residency and consists of two 1‐hour lectures per week and several in‐class tests. The impact of physics on clinical practice is introduced gradually throughout the residency using specific clinical cases. The extensive time spent with the residents allows lectures to be taught at a deep (almost physicist) level and reduces the necessity of learning base concepts outside of lecture. This frees the resident to use resources (e.g., AAPM/RSNA physics modules) to cement concepts through repetition or to learn a slightly confusing concept from a different teaching perspective. Consistent testing reduces the traditional resident studying technique of physics “cramming.”Results:On average, the first year residents scored in the 98th percentile on the American College of Radiology Diagnostic Radiology In‐Service Training Exam (ACR DXIT). Feedback from the new first year residents was very positive and suggestions are constantly solicited and incorporated. For example, based on resident feedback, short‐format quizzes each lecture were eliminated and replaced interactive questions during lecture. Residents felt they have advanced rapidly and have a better understanding of radiologic physics, though they have expressed concern that the 1‐hour lecture block may not be optimal for learning physics.Conclusion:An extensive, physicist‐led series of didactic lectures is effective in the teaching of physics to residents.

SU-E-T-583: Optimizing the MLC Model Parameters for IMRT in the RayStation Treatment Planning System

Purpose: To optimize the MLC model parameters for IMRT in the RayStation v.4.0 planning system and for a Varian C-series Linac with a 120-leaf Millennium MLC. Methods: The RayStation treatment planning system models rounded leaf-end MLC with the following parameters: average transmission, leaf-tip width, tongue-and-groove, and position offset. The position offset was provided by Varian. The leaf-tip width was iteratively evaluated by comparing computed and measured transverse dose profiles of MLC-defined fields at dmax in water. The profile comparison was also used to verify the MLC position offset. The transmission factor and leaf tongue width were derived iteratively by optimizing five clinical patient IMRT QA Results: brain, lung, pancreas, head-and-neck (HN), and prostate. The HN and prostate cases involved splitting fields. Verifications were performed with Mapcheck2 measurements and Monte Carlo calculations. Finally, the MLC model was validated using five test IMRT cases from the AAPM TG119 report. Absolute gamma analyses (3mm/3% and 2mm/2%) were applied. In addition, computed output factors for MLC-defined small fields (2×2, 3×3, 4×4, 6×6cm) of both 6MV and 18MV were compared to those measured by the Radiological Physics Center (RPC). Results: Both 6MV and 18MV models were determined to have the same MLC parameters: 2.5% transmission, tongue-and-groove 0.05cm, and leaftip 0.3cm. IMRT QA analysis for five cases in TG119 resulted in a 100% passing rate with 3mm/3% gamma analysis for 6MV, and >97.5% for 18MV. With 2mm/2% gamma analysis, the passing rate was >94.6% for 6MV and >90.9% for 18MV. The difference between computed output factors in RayStation and RPC measurements was less than 2% for all MLCdefined fields, which meets the RPC's acceptance criterion. Conclusion: The rounded leaf-end MLC model in RayStation 4.0 planning system was verified and IMRT commissioning was clinically acceptable. The IMRT commissioning was well validated using guidance from the AAPMTG119 protocol.

SU‐E‐T‐471: Small Field Jaw/MLC Reference Data

Purpose:In recent years the need for small field data of MLCs has increased due to the use of intensity‐modulated radiation (IMRT), but moreover the use of stereotactic body radiation (SBRT) has increased, which uses not simply small field sizes, but small jaw and field sizes together. Having reference data for these small fields that is reliable would be invaluable to the physics community. Our study has gathered these values and the data distributions from the Radiological Physics Center's (RPC) site visits between 1990 and the present.Methods:For all measurements, the RPC used a 25 × 25 × 25cm water phantom placed at 100cm SSD. All measurements were made with an Exradin A16 cylindrical ion chamber at an effective depth of 10 cm. A total of 42 Varian machine measurements were used to compose the data for a 6 MV beam and 5 TrueBeam 6 MV flattening filter free (FFF) beams were used for FFF data.Results:Jaw/MLC fields were measured for both 6 MV and 6 MF FFF beams with the jaws and MLCs both at the following field sizes: 6×6, 4×4, 3×3, and 2×2cm. Measurements were normalized to the 10×10 field readings (defined by the jaws and MLC). Spread in the data was minimal and demonstrates a high level of accuracy of acquired data.Conclusion:Small field Jaw/MLC reference data for Varian 6MV and 6 MV FFF beams has been analyzed and presented here, composed of the aggregation of numerous RPC site visits. Obtaining reliable small field data remains difficult, however the RPC has collected high fidelity small field Jaw/MLC data. The data are presented as a reference along with their distributions, in such a way that the physicist can act based upon their own desired agreement with the reference data.

SU‐F‐BRE‐14: Uncertainty Analysis for Dose Measurements Using OSLD NanoDots

Purpose:Optically stimulated luminescent dosimeters (OSLD) are an increasingly popular dosimeter for research and clinical applications. It is also used by the Radiological Physics Center for remote auditing of machine output. In this work we robustly calculated the reproducibility and uncertainty of the OSLD nanoDot.Methods:For the RPC dose calculation, raw readings are corrected for depletion, element sensitivity, fading, linearity, and energy. System calibration is determined for the experimental OSLD irradiated at different institutions by using OSLD irradiated by the RPC under reference conditions (i.e., standards): 1 Gy in a Cobalt beam. The intra‐dot and inter‐dot reproducibilities (coefficient of variation) were determined from the history of RPC readings of these standards. The standard deviation of the corrected OSLD signal was then calculated analytically using a recursive formalism that did not rely on the normality assumption of the underlying uncertainties, or on any type of mathematical approximation. This analytical uncertainty was compared to that empirically estimated from >45,000 RPC beam audits.Results:The intra‐dot variability was found to be 0.59%, with only a small variation between readers. Inter‐dot variability was found to be 0.85%. The uncertainty in each of the individual correction factors was empirically determined. When the raw counts from each OSLD were adjusted for the appropriate correction factors, the analytically determined coefficient of variation was 1.8% over a range of institutional irradiation conditions that are seen at the RPC. This is reasonably consistent with the empirical observations of the RPC, where the coefficient of variation of the measured beam outputs is 1.6% (photons) and 1.9% (electrons).Conclusion:OSLD nanoDots provide sufficiently good precision for a wide range of applications, including the RPC remote monitoring program for megavoltage beams.This work was supported by PHS grant CA10953 awarded by the NIH (DHHS).

IMRT credentialing for prospective trials using institutional virtual phantoms: results of a joint European Organization for the Research and Treatment of Cancer and Radiological Physics Center project.

Background and purposeIntensity-modulated radiotherapy (IMRT) credentialing for a EORTC study was performed using an anthropomorphic head phantom from the Radiological Physics Center (RPC; RPCPH). Institutions were retrospectively requested to irradiate their institutional phantom (INSTPH) using the same treatment plan in the framework of a Virtual Phantom Project (VPP) for IMRT credentialing.Materials and methodsCT data set of the institutional phantom and measured 2D dose matrices were requested from centers and sent to a dedicated secure EORTC uploader. Data from the RPCPH and INSTPH were thereafter centrally analyzed and inter-compared by the QA team using commercially available software (RIT; ver.5.2; Colorado Springs, USA).ResultsEighteen institutions participated to the VPP. The measurements of 6 (33%) institutions could not be analyzed centrally. All other centers passed both the VPP and the RPC ±7%/4 mm credentialing criteria. At the 5%/5 mm gamma criteria (90% of pixels passing), 11(92%) as compared to 12 (100%) centers pass the credentialing process with RPCPH and INSTPH (p = 0.29), respectively. The corresponding pass rate for the 3%/3 mm gamma criteria (90% of pixels passing) was 2 (17%) and 9 (75%; p = 0.01), respectively.ConclusionsIMRT dosimetry gamma evaluations in a single plane for a H&N prospective trial using the INSTPH measurements showed agreement at the gamma index criteria of ±5%/5 mm (90% of pixels passing) for a small number of VPP measurements. Using more stringent, criteria, the RPCPH and INSTPH comparison showed disagreement. More data is warranted and urgently required within the framework of prospective studies.

SU‐C‐BRD‐07: The Radiological Physics Center (RPC): 45 Years of Improving Radiotherapy Dosimetry

Purpose:The RPC, established in 1968 has contributed to the development, conduct, and QA of NCI funded multi‐institutional cooperative group clinical trials and institutions, primarily in the USA/Canada and 242 other countries, participating in trials.Methods:The RPC QA program components were designed to audit the radiation dose calculation chain from the NIST traceable reference beam calibration, to inclusion of dosimetry parameters used to calculate tumor doses, to the delivery of the radiation dose. The QA program included: 1) remote TLD/OSLD audit of machine output, 2) on‐site dosimetry review visits, 3) credentialing for advanced technologies, and 4) review of patient treatment records. The RPC presented and published their findings to the radiation oncology community.Results:The number of institutions monitored by the RPC increased from around 1200 in the late 90s, to ∼2000 in 2013. There were over 4000 megavoltage therapy machines and ∼28,000 therapy beams in the 1991 institutions monitored by the RPC by the end of 2013. Within the 14,000 photon, electron and proton beam outputs remotely monitored with TLD/OSLD annually, between 10‐20% of the institutions have one or more beams outside the RPC 5% criterion. Dosimetry site visits to photon and proton centers continue to result in 2‐4 recommendations affecting key dosimetry parameters that impact patient treatment times. One in four patient treatment records reviewed by the RPC have their dose data corrected by >5% before trial groups use them for outcomes analysis. Twelve of fourteen clinically active proton centers are approved to participate in NCI funded clinical trials. The RPC published 222 peer reviewed articles since 1972.Conclusion:Findings from the RPC suggest that human errors continue to play a role in radiotherapy discrepancies and without the RPC independent QA program, the number of undetected errors and time elapsed before their discovery would have been greater.Work supported by MGH C06 CA059267 and grants CA10953, CA081647 awarded by NCI, DHHS.

MO‐G‐BRE‐02: A Survey of IMRT QA Practices for More Than 800 Institutions

Purpose:A wide range of techniques and measurement devices are employed for IMRT QA, causing a large variation of accepted action limits and potential follow up for failing plans. Such procedures are not well established or accepted in the medical physics community. To achieve the goal of proving insight into current IMRT QA practices, we created an electronic IMRT QA survey. The survey was open to a variety of the most common QA devices and assessed the type of comparison to measurement, action limits, delivery methods, and clinical action for failing QA plans.Methods:We conducted an online survey through the Radiological Physics Center's (RPC) annual survey with the goal of ascertaining elements of routine patient‐specific IMRT QA. A total of 874 institutions responded to the survey. The questions ranged from asking for action limits, dosimeter type(s) used, delivery techniques, and actions taken when a plan fails IMRT QA.Results:The most common (52%) planar gamma criteria was 3%/3 mm with a 95% of pixels passing criteria. The most common QA device were diode arrays (48%). The most common first response to a plan failing QA was to re‐measure at the same point the point dose (89%), second was to re‐measure at a new point (13%), and third was to analyze the plan in relative instead of absolute mode (10%) (Does not add to 100% as not all institutions placed a response for each QA follow‐up option). Some institutions, however, claimed that they had never observed a plan failure.Conclusion:The survey provided insights into the way the community currently performs IMRT QA. This information will help in the push to standardize action limits among dosimeters.

An anthropomorphic spine phantom for proton beam approval in NCI-funded trials.

As part of the approval process for the use of scattered or uniform scanning proton therapy in National Cancer Institute (NCI)‐sponsored clinical trials, the Radiological Physics Center (RPC) mandates irradiation of two RPC anthropomorphic proton phantoms (prostate and spine). The RPC evaluates these irradiations to ensure that they agree with the institutions' treatment plans within criteria of the NCI‐funded cooperative study groups. The purpose of this study was to evaluate the use of an anthropomorphic spine phantom for proton matched‐field irradiation, and to assess its use as a credentialing tool for proton therapy beams. We used an anthropomorphic spine phantom made of human vertebral bodies embedded in a tissue substitute material called Muscle Substitute/Solid Rigid Number 4 (MS/SR4) comprising three sections: a posterior section containing the posterior surface and the spinous processes, and left and right (L/R) sections containing the vertebral bodies and the transverse processes. After feasibility studies at three institutions, the phantom, containing two thermoluminescent dosimeters (TLDs) for absolute dose measurements and two sheets of radiochromic film for relative dosimetry, was shipped consecutively to eight proton therapy centers participating in the approval study. At each center, the phantom was placed in a supine or prone position (according to the institution's spine treatment protocol) and imaged with computed tomography (CT). The images then were used with the institution's treatment planning system (TPS) to generate two matched fields, and the phantom was irradiated accordingly. The irradiated phantom was shipped to the RPC for analysis, and the measured values were compared with the institution's TPS dose and profiles using criteria of ± 7% for dose agreement and 5 mm for profile distance to agreement. All proton centers passed the dose criterion with a mean agreement of 3% (maximum observed agreement, 7%). One center failed the profile distance‐to‐agreement criterion on its initial irradiation, but its second irradiation passed the criterion. Another center failed the profile distance‐to‐agreement criterion, but no repeat irradiation was performed. Thus, seven of the eight institutions passed the film profile distance‐to‐agreement criterion with a mean agreement of 1.2 mm (maximum observed agreement 5 mm). We conclude that an anthropomorphic spine phantom using TLD and radiochromic film adequately verified dose delivery and field placement for matched‐field treatments.PACS number: 87.55.‐x, 87.55.N‐

RECIST measurements in cancer treatment: is there a role for physician assistants? - A pilot study.

BackgroundDecision making in cancer treatment is influenced by standardized RECIST measurements which are subjective to interobserver variability. Aim of this pilot study was to evaluate whether it is feasible to transfer the radiologist’s task of RECIST measurements to a trained radiology physician assistant and whether this influences diagnostic performance.Methods177 lesions in twenty patients were measured on baseline and two follow-up CTs using RECIST 1.1: Arm A according to routine clinical practice where various radiologists read scans of the referred patients. Arm B according to the experimental setting where a radiology physician assistant performed RECIST measurements of target lesions defined by the radiologists on baseline scans. Performance and agreement were compared between groups.ResultsStandard deviation between lesion measurements of arm A and B was four millimeters. Interobserver agreement comparing response category classification was substantial, ĸ = 0.77 (95% CI: 0.66 - 0.87). Sensitivity and specificity for the radiology physician assistant for assessing progressive disease were 100% (95% CI: 61% - 100%) and 94% (95% CI: 81% - 98%) respectively.ConclusionRECIST measurements performed by a paramedic are a feasible alternative to standard practice. This could impact the workflow of radiological units, opening ways to re-assigning radiologists’ important, standardized but time consuming tasks to paramedics.

Remote auditing of radiotherapy facilities using optically stimulated luminescence dosimeters

On 1 July 2012, the Australian Clinical Dosimetry Service (ACDS) released its Optically Stimulated Luminescent Dosimeter (OSLD) Level I audit, replacing the previous TLD based audit. The aim of this work is to present the results from this new service and the complete uncertainty analysis on which the audit tolerances are based. The audit release was preceded by a rigorous evaluation of the InLight® nanoDot OSLD system from Landauer (Landauer, Inc., Glenwood, IL). Energy dependence, signal fading from multiple irradiations, batch variation, reader variation, and dose response factors were identified and quantified for each individual OSLD. The detectors are mailed to the facility in small PMMA blocks, based on the design of the existing Radiological Physics Centre audit. Modeling and measurement were used to determine a factor that could convert the dose measured in the PMMA block, to dose in water for the facility's reference conditions. This factor is dependent on the beam spectrum. The TPR20,10 was used as the beam quality index to determine the specific block factor for a beam being audited. The audit tolerance was defined using a rigorous uncertainty calculation. The audit outcome is then determined using a scientifically based two tiered action level approach. Audit outcomes within two standard deviations were defined as Pass (Optimal Level), within three standard deviations as Pass (Action Level), and outside of three standard deviations the outcome is Fail (Out of Tolerance). To-date the ACDS has audited 108 photon beams with TLD and 162 photon beams with OSLD. The TLD audit results had an average deviation from ACDS of 0.0% and a standard deviation of 1.8%. The OSLD audit results had an average deviation of -0.2% and a standard deviation of 1.4%. The relative combined standard uncertainty was calculated to be 1.3% (1σ). Pass (Optimal Level) was reduced to ≤2.6% (2σ), and Fail (Out of Tolerance) was reduced to >3.9% (3σ) for the new OSLD audit. Previously with the TLD audit the Pass (Optimal Level) and Fail (Out of Tolerance) were set at ≤4.0% (2σ) and >6.0% (3σ). The calculated standard uncertainty of 1.3% at one standard deviation is consistent with the measured standard deviation of 1.4% from the audits and confirming the suitability of the uncertainty budget derived audit tolerances. The OSLD audit shows greater accuracy than the previous TLD audit, justifying the reduction in audit tolerances. In the TLD audit, all outcomes were Pass (Optimal Level) suggesting that the tolerances were too conservative. In the OSLD audit 94% of the audits have resulted in Pass (Optimal level) and 6% of the audits have resulted in Pass (Action Level). All Pass (Action level) results have been resolved with a repeat OSLD audit, or an on-site ion chamber measurement.