AAPM Task Group 298: Recommendations on certificate program/alternative pathway candidate education and training.

Entry into the field of clinical medical physics is most commonly accomplished through the completion of a Commission on Accreditation of Medical Physics Educational Programs (CAMPEP)-accredited graduate and residency program. To allow a mechanism to bring valuable expertise from other disciplines into clinical practice in medical physics, an "alternative pathway" approach was also established. To ensure those trainees who have completed a doctoral degree in physics or a related discipline have the appropriate background and didactic training in medical physics, certificate programs and a CAMPEP-accreditation process for these programs were initiated. However, medical physics-specific didactic, research, and clinical exposure of those entering medical physics residencies from these certificate programs is often comparatively modest when evaluated against individuals holding Master's and/or Doctoral degrees in CAMPEP-accredited graduate programs. In 2016, the AAPM approved the formation of Task Group (TG) 298, "Alternative Pathway Candidate Education and Training." The TG was charged with reviewing previous published recommendations for alternative pathway candidates and developing recommendations on the appropriate education and training of these candidates. This manuscript is a summary of the AAPM TG 298 report.

Capacitance-Based Dosimetry of Co-60 Radiation using Fully-Depleted Silicon-on-Insulator Devices.

The capacitance based sensing of fully-depleted silicon-on-insulator (FDSOI) variable capacitors for Co-60 gamma radiation is investigated. Linear response of the capacitance is observed for radiation dose up to 64 Gy, while the percent capacitance change per unit dose is as high as 0.24 %/Gy. An analytical model is developed to study the operational principles of the varactors and the maximum sensitivity as a function of frequency is determined. The results show that FDSOI varactor dosimeters have potential for extremely-high sensitivity as well as the potential for high frequency operation in applications such as wireless radiation sensing.

Essentials and guidelines for clinical medical physics residency training programs: executive summary of AAPM Report Number 249.

There is a clear need for established standards for medical physics residency training. The complexity of techniques in imaging, nuclear medicine, and radiation oncology continues to increase with each passing year. It is therefore imperative that training requirements and competencies are routinely reviewed and updated to reflect the changing environment in hospitals and clinics across the country. In 2010, the AAPM Work Group on Periodic Review of Medical Physics Residency Training was formed and charged with updating AAPM Report Number 90. This work group includes AAPM members with extensive experience in clinical, professional, and educational aspects of medical physics. The resulting report, AAPM Report Number 249, concentrates on the clinical and professional knowledge needed to function independently as a practicing medical physicist in the areas of radiation oncology, imaging, and nuclear medicine, and constitutes a revision to AAPM Report Number 90. This manuscript presents an executive summary of AAPM Report Number 249.

Recommendations for clinical electron beam dosimetry: supplement to the recommendations of Task Group 25.

The goal of Task Group 25 (TG-25) of the Radiation Therapy Committee of the American Association of.Physicists in Medicine (AAPM) was to provide a methodology and set of procedures for a medical physicist performing clinical electron beam dosimetry in the nominal energy range of 5-25 MeV. Specifically, the task group recommended procedures for acquiring basic information required for acceptance testing and treatment planning of new accelerators with therapeutic electron beams. Since the publication of the TG-25 report, significant advances have taken place in the field of electron beam dosimetry, the most significant being that primary standards laboratories around the world have shifted from calibration standards based on exposure or air kerma to standards based on absorbed dose to water. The AAPM has published a new calibration protocol, TG-51, for the calibration of high-energy photon and electron beams. The formalism and dosimetry procedures recommended in this protocol are based on the absorbed dose to water calibration coefficient of an ionization chamber at 60Co energy, N60Co(D,w), together with the theoretical beam quality conversion coefficient k(Q) for the determination of absorbed dose to water in high-energy photon and electron beams. Task Group 70 was charged to reassess and update the recommendations in TG-25 to bring them into alignment with report TG-51 and to recommend new methodologies and procedures that would allow the practicing medical physicist to initiate and continue a high quality program in clinical electron beam dosimetry. This TG-70 report is a supplement to the TG-25 report and enhances the TG-25 report by including new topics and topics that were not covered in depth in the TG-25 report. These topics include procedures for obtaining data to commission a treatment planning computer, determining dose in irregularly shaped electron fields, and commissioning of sophisticated special procedures using high-energy electron beams. The use of radiochromic film for electrons is addressed, and radiographic film that is no longer available has been replaced by film that is available. Realistic stopping-power data are incorporated when appropriate along with enhanced tables of electron fluence data. A larger list of clinical applications of electron beams is included in the full TG-70 report available at http://www.aapm.org/pubs/reports. Descriptions of the techniques in the clinical sections are not exhaustive but do describe key elements of the procedures and how to initiate these programs in the clinic. There have been no major changes since the TG-25 report relating to flatness and symmetry, surface dose, use of thermoluminescent dosimeters or diodes, virtual source position designation, air gap corrections, oblique incidence, or corrections for inhomogeneities. Thus these topics are not addressed in the TG-70 report.

In vivo diode dosimetry for IMRT treatments generated by Pinnacle treatment planning system.

Dose verification using diodes has been proposed and used for intensity modulated radiation therapy (IMRT) treatments. We have previously evaluated diode response for IMRT deliveries planned with the Eclipse/Helios treatment planning system. The Pinnacle treatment planning system generates plans that are delivered in a different fashion than Eclipse. Whereas the Eclipse-generated segments are delivered in organized progression from one side of each field to the other, Pinnacle-generated segments are delivered in a much more randomized fashion to different areas within the field. This makes diode measurements at a point more challenging because the diode may be exposed fully or partially to multiple small segments during one single field's treatment as opposed to being exposed to very few segments scanning across the diode during an Eclipse-generated delivery. We have evaluated in vivo dosimetry for Pinnacle-generated IMRT plans and characterized the response of the diode to various size segments on phantom. We present results of patient measurements on approximately 300 fields, which show that 76% of measurements agree to within 10% of the treatment-plan generated calculated doses. Of the other 24%, about 11% are within 15% of the calculated dose. Comparison of these with phantom measurements indicates that many of the discrepancies are due to diode positioning on patients and increased diode response at short source-to-surface distances (SSDs), with the remainder attributable to other factors such as segment size and partial irradiation of the diode.

Measurement of superficial dose from a static tomotherapy beam.

Superficial doses were measured for static TomoTherapy Hi-Art beams for normal and oblique incidence. Dose was measured at depths < or = 2 cm along the central axis of 40 x 5 cm2 and 40 x 2.5 cm2 beams at normal incidence for source to detector distances (SDDs) of 55, 70, and 85 cm. Measurements were also made at depths normal to the phantom surface for the same beams at oblique angles of 30 degrees, 45 degrees, 60 degrees, 75 degrees, and 83 degrees from the normal. Data were collected with a Gammex/RMI model 449 parallel-plate chamber embedded in a solid water phantom and with LiF thermoluminescent dosimeters (TLDs) in the form of powder. For comparison, measurements were made on a conventional 6 MV beam (Varian Clinac 2100C) at normal incidence and at an oblique angle of 60 degrees from the normal. TomoTherapy surface dose varied with the distance from the source and the angle of incidence. For normal incidence, surface dose increased from 0.16 to 0.43 cGy/MU as the distance from the source decreased from 85 to 55 cm for the 40 x 5 cm2 field and increased from 0.12 to 0.32 cGy/MU for the 40 x 2.5 cm2 field. As the angle of incidence increased from 0 degrees to 83 degrees, surface dose increased from 0.24 to 0.63 cGy/MU for the 40 x 5 cm2 field and from 0.18 to 0.58 cGy/MU for the 40 x 2.5 cm2 field. For normal incidence at 55 cm SDD, the surface dose relative to the dose at d(max) for the 40 x 5 cm2 TomoTherapy Hi-Art beam was 31% less than that from a conventional, flattening filter based linear accelerator. These data should prove useful in accessing the accuracy of the TomoTherapy treatment planning system to predict the dose at superficial depths for a static beam delivery.

Safety and efficacy of fractionated stereotactic radiotherapy for acoustic neuromas.

BACKGROUND: The treatment of acoustic neuromas (AN) has historically involved surgical excision or stereotactic radiosurgery, with a relatively limited number of reports available describing the use of fractionated stereotactic radiotherapy (FSRT). To enhance the existing knowledge regarding the safety and efficacy of this treatment modality, we describe our initial experience with FSRT for AN. METHODS: From 1999-2005, 20 patients (12F, 8M) with AN underwent FSRT. All patients were treated using the Radionics X-Knife 4.0 3D planning system, receiving 54 Gy in 1.8 Gy daily fractions with a prescription isodose line of 90%. Treatments were delivered stereotactically using a dedicated Varian 6/100 linear accelerator, with immobilization achieved via the Gill-Thomas-Cosman relocatable frame. Median tumor size (maximum diameter) was 2.1 cm (range, 1.1-3.4 cm). Median patient age was 49.5 years, with median follow-up of 22 months (range, 1-66 months). All patients were evaluated with pre- and post-gadolinium-enhanced magnetic resonance imaging. RESULTS: Following FSRT, local tumor control was achieved in every patient, with the treatment well-tolerated by all patients. No patient experienced acute complications or facial nerve weakness. Two patients experienced permanent trigeminal nerve morbidity manifesting as facial numbness. All nine patients with preserved hearing before treatment had hearing preservation at last follow-up, although four of these patients experienced hearing decline following FSRT. CONCLUSION: In our series of 20 patients with AN, all had local tumor control following FSRT, with minimal morbidity. These results support the growing body of literature demonstrating the safety and efficacy of FSRT in achieving local control for AN, further validating the viability of FSRT as a treatment modality for this patient population.

ASTRO's 2007 core physics curriculum for radiation oncology residents.

In 2004, the American Society for Therapeutic Radiology and Oncology (ASTRO) published a curriculum for physics education. The document described a 54-hour course. In 2006, the committee reconvened to update the curriculum. The committee is composed of physicists and physicians from various residency program teaching institutions. Simultaneously, members have associations with the American Association of Physicists in Medicine, ASTRO, Association of Residents in Radiation Oncology, American Board of Radiology, and American College of Radiology. Representatives from the latter two organizations are key to provide feedback between the examining organizations and ASTRO. Subjects are based on Accreditation Council for Graduate Medical Education requirements (particles and hyperthermia), whereas the majority of subjects and appropriated hours/subject were developed by consensus. The new curriculum is 55 hours, containing new subjects, redistribution of subjects with updates, and reorganization of core topics. For each subject, learning objectives are provided, and for each lecture hour, a detailed outline of material to be covered is provided. Some changes include a decrease in basic radiologic physics, addition of informatics as a subject, increase in intensity-modulated radiotherapy, and migration of some brachytherapy hours to radiopharmaceuticals. The new curriculum was approved by the ASTRO board in late 2006. It is hoped that physicists will adopt the curriculum for structuring their didactic teaching program, and simultaneously, the American Board of Radiology, for its written examination. The American College of Radiology uses the ASTRO curriculum for their training examination topics. In addition to the curriculum, the committee added suggested references, a glossary, and a condensed version of lectures for a Postgraduate Year 2 resident physics orientation. To ensure continued commitment to a current and relevant curriculum, subject matter will be updated again in 2 years.

Radiation exposure during head repositioning with the automatic positioning system for gamma knife radiosurgery.

PURPOSE: To measure radiation exposure to a patient during head repositioning with the automatic positioning system (APS) for Gamma Knife radiosurgery. METHODS AND MATERIALS: A 16-cm diameter spherical solid phantom, provided by the manufacturer, was mounted to the APS unit using a custom-made holder. A small-volume ionization chamber (0.07-cm(3) volume) was placed at the center of the phantom. We recorded the temporal variation of ionization current during the entire treatment. Measurements were made for 3 test cases and 7 clinical cases. RESULTS: The average transit time between successive shots, during which the APS unit was moving the phantom for repositioning the shot coordinates, was 20.5 s for 9 cases. The average dose rate, which was measured at the center of the phantom and at a point outside the shot location, was 0.36 +/- 0.09 cGy/min when the beam output was approximately 3.03 Gy/min for the 18-mm collimator helmet. Hence, the additional intracranial radiation dose during the APS-driven head repositioning between two successive shots (or APS transit dose) was 0.12 +/- 0.050 cGy. The APS transit dose was independent of the helmet size and the position of shots within the phantom relative to the measurement point. CONCLUSION: The head repositioning with the APS system adds a small but not negligible dose to the dose expected for the manual repositioning method.

Fractionated stereotactic radiotherapy for pituitary adenomas following microsurgical resection: safety and efficacy.

The treatment of pituitary adenomas following medical management has historically involved surgical excision or stereotactic radiosurgery, with the two modalities often utilized collectively. However, there have been only a limited number of reports on the use of fractionated stereotactic radiotherapy (FSRT) for the treatment of pituitary adenomas. To enhance the existing knowledge regarding the safety and efficacy of this treatment modality, we describe our initial experience with FSRT for residual pituitary adenomas following microsurgical resection. From 1999 to 2005, 14 patients (7F, 7M) with residual pituitary adenomas (7 nonsecretory, 2 growth hormone secreting, 2 prolactin secreting, 2 thyrotropin secreting, 1 adrenocorticotropic hormone secreting) underwent FSRT. All patients were planned using the Radionics X-Knife 3D planning system, and received a median dose of 50.4 Gy in daily 1.8 Gy fractions administered to the 90% prescription isodose line. Treatments were delivered stereotactically using a dedicated Varian 6/100 linear accelerator, with immobilization achieved with the Gill-Thomas-Cosman relocatable head frame. Mean tumor size was 3.6 cm (median, 3.2 cm), and mean patient age was 44.6 years (median, 47 years). The mean dosages to the optic chiasm and brainstem were 0.159 and 0.040 Gy (median, 0.163 and 0.031 Gy) per fraction. All patients were evaluated with visual field testing and pre- and postgadolinium-enhanced magnetic resonance imaging at a minimum of one year follow-up (median, 22.5 months; mean, 27.8 months). Following FSRT, local control (defined as absence of tumor progression) was achieved in all fourteen patients. Three patients developed hypopituitarism (average, 30 months after treatment), with no patient experiencing visual changes or acute complications following FSRT. These results demonstrate the efficacy and safety of FSRT for achieving long-term local tumor control for pituitary adenomas, further validating this technique as an appropriate treatment modality for residual adenomas following microsurgery.

The treatment of a large acoustic tumor with fractionated stereotactic radiotherapy.

The treatment of acoustic neuromas (AN) usually involves surgical excision or stereotactic radiosurgery. However, for large AN (mean diameter > 3 cm), stereotactic radiosurgery is rarely used, leaving patients with limited noninvasive treatment options. Recently, the use of fractionated stereotactic radiotherapy (FSRT) has been effective in treating small to medium-sized AN. We present a patient with a large AN treated with FSRT. The patient was a 43-year-old man presenting with imbalance, tinnitus, vertigo, and right-sided hearing decline associated with vomiting and hydrocephalus. Magnetic resonance (MR) imaging revealed a large, 3.8-cm, right cerebellopontine-angle tumor compressing the fourth ventricle. Following right frontal ventriculoperitoneal shunt placement, the patient underwent FSRT for treatment of the tumor. Using the Radionics X-Knife 4.0 3D treatment planning system, a total of 54 Gy was delivered in 1.8-Gy daily fractions with the prescription isodose line of 90%. Treatments were delivered using a dedicated Varian 6/100 linear accelerator, and head immobilization was achieved with the Gill-Thomas-Cosman relocatable stereotactic frame. The patient was subsequently evaluated with serial contrast-enhanced MR imaging. Following FSRT, local control (defined as the absence of tumor progression) was achieved, and treatment was well tolerated. There was no hearing-related, trigeminal, or facial-nerve morbidity following FSRT at 63-month follow-up. Treating a patient with a large AN with FSRT resulted in local tumor control, with no trigeminal nerve, facial nerve, or hearing-related morbidity. These results support FSRT as a potential noninvasive treatment modality for AN some would consider too large for single-fraction stereotactic radiosurgery (SRS).

Geometrical accuracy of a 3-tesla magnetic resonance imaging unit in Gamma Knife surgery.

OBJECT: The authors sought to evaluate and improve the geometrical accuracy of a 3-tesla magnetic resonance (MR) imaging unit used for Gamma Knife surgery (GKS). METHODS: To evaluate the geometrical accuracy of a Siemens Magnetom Trio 3-tesla MR imaging unit, two phantoms were used. Both phantoms were imaged with computed tomography (CT), a 1.5-tesla MR imaging unit (Siemens Avanto), and the 3-tesla MR imaging unit. A pair of orthogonal films was obtained with a radiotherapy simulator to validate the spatial coordinates of the marker positions determined with CT. The coordinates of the markers were measured using the GammaPlan treatment planning software. Magnetic resonance imaing was performed using three-dimensional (3D) magnetization-prepared rapid acquisition gradient echo (MPRAGE) and fast low-angle shot sequence (FLASH) pulse sequences. The voxel size was 1 x 1 x 1 mm3. CONCLUSIONS: The root-mean-square error of MR images was 2 +/- 0.73 mm for 3D MPRAGE. The error was reduced to 1.5 +/- 0.64 mm for FLASH. The errors were decreased further by applying an image distortion correction method (the field-of-view filter) to the images acquired with FLASH. The mean errors were 1.3 +/- 0.39 mm and 1.5 +/- 0.77 mm for the two phantoms. The errors increased from 1 mm to 3.1 mm as the measurement points approached the caudal edge of the head coil (larger z value). Proper selection of a pulse sequence together with a geometrical distortion correction improved the geometrical accuracy of MR images. However, further study is needed to increase the geometrical accuracy of 3-tesla MR imaging units for radiosurgical applications.

The use of a commercial QA device for daily output check of a helical tomotherapy unit.

Helical tomotherapy radiation therapy units, due to their particular design and differences from a traditional linear accelerator, require different procedures by which to perform routine quality assurance (QA). One of the principal QA tasks that should be performed daily on any radiation therapy equipment is the output constancy check. The daily output check on a Hi-Art TomoTherapy unit is commonly performed utilizing ionization chambers placed inside a solid water phantom. This provides a good check of output at one point, but does not give any information on either energy or symmetry of the beam, unless more than one point is measured. This also has the added disadvantage that it has to be done by the physics staff. To address these issues, and to simplify the process, such that it can be performed by radiation therapists, we investigated the use of a commercially available daily QA device to perform this task. The use of this device simplifies the task of daily output constancy checks and eliminates the need for continued physics involvement. This device can also be used to monitor the constancy of beam energy and cone profile and can potentially be used to detect gross errors in the couch movement or laser alignment.

Fractionated stereotactic radiotherapy for pediatric patients with retinoblastoma.

In this report we discuss the application of a modified Gill-Thomas-Cosman (GTC) relocatable head frame to enable fractionated stereotactic radiotherapy (SRT) of infants under anesthesia. This system has been used to treat two infants, ages 12 and 18 months for bilateral retinoblastoma on a Varian 6/100 linear accelerator. The GTC head frame was used to reproduceably position and treat the orbits of these children to between 2520 and 3960 cGy in 180 cGy fractions. A standard head and neck tray, with accompanying thermoplastic mask, was adapted to mount to the head frame to enable these treatments. We found the maximum average deviation in the repeat fixations, as compared with the initial fitting data, to be +/- 2 mm. The overall average difference and standard deviation in measurement was 0.47 +/- 0.63 mm for the first case, and 0.19 +/- 0.94 mm for the second case with a combined average of 0.35 +/- 0.79 mm overall from a total of 381 point measurements. The stereotactic treatment plan (Radionics) incorporated a single isocenter for each orbit and 3-4 arcs per isocenter. Inter-comparisons have been made between this technique and a standard lateral field technique, designed using the SRS planning system. Dose-volume histograms and corresponding normal tissue complication probabilities (NTCP) based on pediatric bone growth inhibition have been calculated for each method for the orbital bone areas. We have found that the NTCP is reduced from 95-100% in the standard treatment method to 16% or less with SRT. Use of the modified head frame provides excellent setup reproducibility, facilitates access to patients for anesthesia and reduces the chances of a poor cosmetic result in these growing children.

Implementation of enhanced dynamic wedges in Pinnacle treatment planning system.

Enhanced dynamic wedges (EDW) provide many advantages over traditional hard wedges for linear accelerator treatments. Along with these advantages comes the responsibility of ensuring that this complex technology delivers the correct dose to patients. This involves determining the enhanced dynamic wedge factors for various field sizes and depths for use in the hand calculation of monitor units (MUs). The accurate representation of dynamic wedges in the treatment planning computer must also be ensured. This is required so that the final isodose distributions are correct and the MUs calculated by the treatment planning computer match those determined by hand calculation. We have commissioned and implemented the use of EDW in the Pinnacle radiation therapy planning system. The modeled dose profiles agree with the measured ones with a maximum difference of 2%. The MUs generated by Pinnacle are also within 2% of those calculated independently. The process of data collection and verification, beam modeling, and a discussion of a potential pitfall encountered in this process are presented in this paper.

ASTRO's core physics curriculum for radiation oncology residents.

In 2002, the Radiation Physics Committee of the American Society of Therapeutic Radiology and Oncology (ASTRO) appointed an Ad-hoc Committee on Physics Teaching to Medical Residents. The main initiative of the committee was to develop a core curriculum for physics education. Prior publications that have analyzed physics teaching have pointed to wide discrepancies among teaching programs. The committee was composed of physicists or physicians from various residency program based institutions. Simultaneously, members had associations with the American Association of Physicists in Medicine (AAPM), ASTRO, Association of Residents in Radiation Oncology (ARRO), American Board of Radiology (ABR), and the American College of Radiology (ACR). The latter two organizations' representatives were on the physics examination committees, as one of the main agendas was to provide a feedback loop between the examining organizations and ASTRO. The document resulted in a recommended 54-h course. Some of the subjects were based on American College of Graduate Medical Education (ACGME) requirements (particles, hyperthermia), whereas the majority of the subjects along with the appropriated hours per subject were devised and agreed upon by the committee. For each subject there are learning objectives and for each hour there is a detailed outline of material to be covered. Some of the required subjects/h are being taught in most institutions (i.e., Radiation Measurement and Calibration for 4 h), whereas some may be new subjects (4 h of Imaging for Radiation Oncology). The curriculum was completed and approved by the ASTRO Board in late 2003 and is slated for dissemination to the community in 2004. It is our hope that teaching physicists will adopt the recommended curriculum for their classes, and simultaneously that the ABR for its written physics examination and the ACR for its training examination will use the recommended curriculum as the basis for subject matter and depth of understanding. To ensure that the subject matter and emphasis remain current and relevant, the curriculum will be updated every 2 years.

Linac-based stereotactic radiosurgery for treatment of trigeminal neuralgia.

Trigeminal neuralgia (TN) is a disabling pain condition that has classically been treated using either surgical or medical techniques. Several researchers have shown that stereotactically delivered radiation can be an effective tool in the amelioration of this condition. For these studies, the Gamma Knife was used to deliver the radiation treatment. The target location was designated as the proximal nerve at the root entry zone, and doses greater than 70 Gy to the maximum point in a single fraction were found to be effective in controlling pain in 80% of the patients treated. LINAC-based stereotactic radiosurgery has been notably absent from the treatment of TN, even though it has many similarities to Gamma Knife-based stereotactic radiosurgery. The aim of this paper is to describe our LINAC-based stereotactic technique for treatment of TN. We also compare treatment of TN using our technique to that using the Gamma Knife. We found that a LINAC-based treatment of TN can be accomplished with accuracy comparable to treatments delivered using the Gamma Knife. The dose distributions are essentially equivalent for the two treatment approaches. The LINAC-based system is easy to plan and offers the ability to reduce the involvement of sensitive structures from the treatment fields as well as the Gamma Knife system does. A disadvantage of the LINAC-based system is the time involved for treatment.

Long-term follow-up of trigeminal neuralgia treatment using a linear accelerator.

While most of the studies examining radiosurgery for trigeminal neuralgia have used a Gamma Knife, a linear accelerator can also be utilized for treatment. We report on 20 patients with trigeminal neuralgia who received 23 treatments with a linear accelerator that delivered a maximum dose of 82.3-100 Gy. The median patient follow-up was 56.5 months, 70% of patients had received previous surgical treatment and 20% had secondary (nonessential) trigeminal neuralgia. Eight (35%) radiosurgery treatments resulted in complete pain relief; 5 (63%) patients with initial pain relief had pain recurrence at a mean time of 21.5 months. Ten (43%) patients reported a 50% or more decrease in pain severity but have not achieved a pain-free state. A total of 18 (78%) treatments resulted in no pain or a 50% or greater improvement in pain. Five treatments (22%) resulted in less than 50% improvement in pain. We conclude that linear accelerator stereotactic radiosurgery is a viable treatment option for trigeminal neuralgia patients, especially for patients who have not had a previous invasive treatment.

The response of Kodak EDR2 film in high-energy electron beams.

Kodak XV2 film has been a key dosimeter in radiation therapy for many years. The advantages of the recently introduced Kodak EDR2 film for photon beam dosimetry have been the focus of several IMRT verification dosimetry publications. However, no description of this film's response to electron beams exists in the literature. We initiated a study to characterize the response and utility of this film for electron beam dosimetry. We exposed a series of EDR2 films to 6, 9, 12, 16, and 20 MeV electrons in addition to 6 and 18 MV x rays to develop standard characteristic curves. The linac was first calibrated to ensure that the delivered dose was known accurately. All irradiations were done at dmax in polystyrene for both photons and electrons, all films were from the same batch, and were developed at the same time. We also exposed the EDR2 films in a solid water phantom to produce central axis depth dose curves. These data were compared against percent depth dose curves measured in a water phantom using an IC-10 ion chamber, Kodak XV2 film, and a PTW electron diode. The response of this film was the same for both 6 and 18 MV x rays, but showed an apparent energy-dependent enhancement for electron beams. The response of the film also increased with increasing electron energy. This caused the percent depth dose curves using film to be shifted toward the surface compared to the ion chamber data.

Dosimetric considerations for patients with HIP prostheses undergoing pelvic irradiation. Report of the AAPM Radiation Therapy Committee Task Group 63.

This document is the report of a task group of the Radiation Therapy Committee of the AAPM and has been prepared primarily to advise hospital physicists involved in external beam treatment of patients with pelvic malignancies who have high atomic number (Z) hip prostheses. The purpose of the report is to make the radiation oncology community aware of the problems arising from the presence of these devices in the radiation beam, to quantify the dose perturbations they cause, and, finally, to provide recommendations for treatment planning and delivery. Some of the data and recommendations are also applicable to patients having implanted high-Z prosthetic devices such as pins, humeral head replacements. The scientific understanding and methodology of clinical dosimetry for these situations is still incomplete. This report is intended to reflect the current state of scientific understanding and technical methodology in clinical dosimetry for radiation oncology patients with high-Z hip prostheses.