Characterization and evaluation of an integrated quality monitoring system for online quality assurance of external beam radiation therapy.

PURPOSE: The aim of this work was to comprehensively evaluate a new large field ion chamber transmission detector, Integral Quality Monitor (IQM), for online external photon beam verification and quality assurance. The device is designed to be mounted on the linac accessory tray to measure and verify photon energy, field shape, gantry position, and fluence before and during patient treatment. METHODS: Our institution evaluated the newly developed ion chamber's effect on photon beam fluence, response to dose, detection of photon fluence modification, and the accuracy of the integrated barometer, thermometer, and inclinometer. The detection of photon fluence modifications was performed by measuring 6 MV with fields of 10 cm × 10 cm and 1 cm × 1 cm "correct" beam, and then altering the beam modifiers to simulate minor and major delivery deviations. The type and magnitude of the deviations selected for evaluation were based on the specifications for photon output and MLC position reported in AAPM Task Group Report 142. Additionally, the change in ion chamber signal caused by a simulated IMRT delivery error is evaluated. RESULTS: The device attenuated 6 MV, 10 MV, and 15 MV photon beams by 5.43 ± 0.02%, 4.60 ± 0.02%, and 4.21 ± 0.03%, respectively. Photon beam profiles were altered with the IQM by < 1.5% in the nonpenumbra regions of the beams. The photon beam profile for a 1 cm × 1 cm2 fields were unchanged by the presence of the device. The large area ion chamber measurements were reproducible on the same day with a 0.14% standard deviation and stable over 4 weeks with a 0.47% SD. The ion chamber's dose-response was linear (R2 = 0.99999). The integrated thermometer agreed to a calibrated thermometer to within 1.0 ± 0.7°C. The integrated barometer agreed to a mercury barometer to within 2.3 ± 0.4 mmHg. The integrated inclinometer gantry angle measurement agreed with the spirit level at 0 and 180 degrees within 0.03 ± 0.01 degrees and 0.27 ± 0.03 at 90 and 270 degrees. For the collimator angle measurement, the IQM inclinometer agreed with a plum-bob within 0.3 ± 0.2 degrees. The simulated IMRT error increased the ion chamber signal by a factor of 11-238 times the baseline measurement for each segment. CONCLUSIONS: The device signal was dependent on variations in MU delivered, field position, single MLC leaf position, and nominal photon energy for both the 1 cm × 1 cm and 10 cm × 10 cm fields. This detector has demonstrated utility repeated photon beam measurement, including in IMRT and small field applications.

Extrinsic doping of the half-Heusler compounds.

Controlling the p- and n-type doping is a key tool to improve the power-factor of thermoelectric materials. In the present work we provide a detailed understanding of the defect thermochemistry in half-Heusler compounds. We calculate the formation energies of intrinsic and extrinsic defects in state of the art n-type TiNiSn and p-type TiCoSb thermoelectric materials. It is shown how the incorporation of online repositories can reduce the workload in these calculations. In TiNiSn we find that Ni- and Ti-interstitial defects play a crucial role in the carrier concentration of TiNiSn. Furthermore, we find that extrinsic doping with Sb can substantially enhance the carrier concentration, in agreement with experiment. In case of TiCoSb, we find ScTi, FeCo and SnSb being possible p-type dopants. While experimental work has mainly focussed on Sn-doping of the Sb site, the present result underlines the possibility to p-dope TiCoSb on all lattice sites.

A failure modes and effects analysis study for gynecologic high-dose-rate brachytherapy.

PURPOSE: To improve the quality of our gynecologic brachytherapy practice and reduce reportable events, we performed a process analysis after the failure modes and effects analysis (FMEA). METHODS AND MATERIALS: The FMEA included a multidisciplinary team specifically targeting the tandem and ring brachytherapy procedure. The treatment process was divided into six subprocesses and failure modes (FMs). A scoring guideline was developed based on published FMEA studies and assigned through team consensus. FMs were ranked according to overall and severity scores. FM ranking >5% of the highest risk priority number (RPN) score was selected for in-depth analysis. The efficiency of each existing quality assurance to detect each FM was analyzed. RESULTS: We identified 170 FMs, and 99 were scored. RPN scores ranged from 1 to 192. Of the 13 highest-ranking FMs with RPN scores >80, half had severity scores of 8 or 9, with no mode having severity of 10. Of these FM, the originating process steps were simulation (5), treatment planning (5), treatment delivery (2), and insertion (1). Our high-ranking FM focused on communication and the potential for applicator movement. Evaluation of the efficiency and the comprehensiveness of our quality assurance program showed coverage of all but three of the top 49 FMs ranked by RPN. CONCLUSIONS: This is the first reported FMEA process for a comprehensive gynecologic brachytherapy procedure overview. We were able to identify FMs that could potentially and severely impact the patient's treatment. We continue to adjust our quality assurance program based on the results of our FMEA analysis.

Medical Physics Practice Guideline 4.a: Development, implementation, use and maintenance of safety checklists.

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 8,000 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.Should and Should Not: Used to indicate a prudent practice to which exceptions may occasionally be made in appropriate circumstances.

Achieving optimum carrier concentrations in p-doped SnS thermoelectrics.

Tin(II)sulfide, SnS, is a commercially viable and environmentally friendly thermoelectric material. Recently it was shown how the carrier concentration and the thermoelectric power factor can be optimized by Ag-doping in a sulphur rich environment. Theoretical calculations lead to a fairly accurate estimation of the carrier concentration, whereas the potential of doping with Li(+) is strongly overestimated. Two principally ubiquitous effects that can result in decreasing the hole concentration, namely the formation of coupled defect complexes and oxidation of the dopant, are discussed as possible origins of this disagreement. It is shown that oxidation limits the chemical potential of Li beyond that already set by the formation of Li2S. This work serves as a comprehensive guide to achieve an efficient p-doped SnS thermoelectric material.

Enhanced surface dose via fine brass mesh for a complex skin cancer of the head and neck: report of a technique.

PURPOSE: The use of fine brass mesh in conjunction with rotational intensity modulated radiation to enhance surface dose for a complex skin cancer of the head and neck has not previously been described. METHODS AND MATERIALS: We present a case of locally advanced basal cell carcinoma with temporal bone erosion treated with rotational intensity modulated radiation via helical tomotherapy with brass mesh. In vivo surface dose was assessed at multiple locations to verify delivered surface dose. Phantom measurements identified the enhancement ratio with the addition of brass mesh, and evaluated impact on the underlying dose distribution. RESULTS: The brass mesh use was feasible and conformed well to the underlying surface. In vivo dosimetry identified excellent skin surface dose with a mean of 103% of the prescription dose at the surface (range, 97%-120%). Phantom measurements identified a surface dose enhancement ratio of 1.36, and 1.38, respectively, with placement of brass mesh. Clinically, the patient is without evidence of disease or major treatment sequelae at 12 months follow-up. CONCLUSIONS: For complex cutaneous malignancies with irregular surfaces unsuitable for tissue equivalent bolus, brass mesh provides an alternate method of increasing surface dose if inadequate surface dosimetry is identified with phantom or in vivo measurements.

Implant time and process efficiency for CT-guided high-dose-rate brachytherapy for cervical cancer.

PURPOSE: This investigation details the time and teamwork required for CT-guided tandem and ring high-dose-rate brachytherapy. METHODS AND MATERIALS: From 2010 to 2012, 217 consecutive implantations were identified on 52 patients. We gathered key workflow times: preoperative, applicator insertion, CT image, treatment planning, treatment, patient recovery, and total time in clinic. Linear fixed-effects models were used, and key workflow times were the outcome variables and factors including age, body mass index, stage, outside referral, number of implant per patient, number of implants per day, and year of implantation were examined as fixed effects. RESULTS: Of the 52 patients, 62% of the patients were Fédération Internationale de Gynécologie et d'Obstétrique Stage 2B, 88% were treated with concurrent chemotherapy, and 23% were treated at an outside facility and referred for the procedure. The mean times (minutes) for each step were as follows: preoperative evaluation, 93; insertion, 23; imaging, 45; treatment planning, 137; treatment, removal, and recovery, 115; total clinic time, 401. For the insertion time, the greater implant number per patient was significantly associated with a decreased total insertion time, with and without adjusting for other covariates, p = 0.002 and p = 0.0005, respectively. Treatment planning time was expedited with increasing number of implant per patient and comparing treatment times in 2012 with those in 2010, p = 0.01 and p < 0.0001, respectively. CONCLUSIONS: Gynecologic brachytherapy requires a skillfully coordinated and efficient team approach. Identifying critical components and the time required for each step in the process is needed to improve the safety and efficiency of brachytherapy. Continuous efforts should be made to enhance the optimal treatment delivery in high-dose-rate gynecologic brachytherapy.

The equivalent dose contribution from high-dose-rate brachytherapy to positive pelvic lymph nodes in locally advanced cervical cancer.

PURPOSE: Definitive radiation therapy for locally advanced cervical cancer involves external beam radiation therapy (EBRT) and high-dose-rate (HDR) brachytherapy. There remains controversy and practice pattern variation regarding the optimal radiation dose to metastatic pelvic lymph nodes (LNs). This study investigates the contribution of the pelvic LN dose from HDR brachytherapy. METHODS AND MATERIALS: For 17 patients with 36 positive pelvic LNs, each LN was contoured on a computed tomography (CT) plan for EBRT and on brachytherapy planning CTs using positron emission tomographic images obtained before chemoradiation. The mean delivered dose from each plan was recorded, and an equivalent dose in 2-Gy fractions (EQD2) was calculated. A Student's t test was performed to determine if the mean delivered dose is significantly different from the mean prescribed dose and EQD2. RESULTS: The average prescribed dose from the total EBRT was 54.09 Gy. The average prescribed HDR dose to International Commission on Radiation Units point A was 26.81 Gy. The average doses delivered to the involved LNs from EBRT and brachytherapy were 54.25 and 4.31 Gy, respectively, with the corresponding EQD2 of 53.45 and 4.00 Gy. There was no statistically significant difference (p < 0.05) between the mean delivered and the prescribed doses for EBRT and between the delivered dose and the EQD2 for EBRT and brachytherapy. CONCLUSIONS: Our study shows that the HDR contribution is 7% (4.00 Gy) of the total EQD2 (57.45 Gy). The HDR contribution should be accounted for when prescribing the EBRT boost dose to pelvic LNs for the optimal therapeutic dose.

Gratitude as a psychotherapeutic intervention.

Gratitude practice can be a catalyzing and relational healing force, often untapped in clinical practice. In this article, we provide an overview of current thinking about gratitude's defining and beneficial properties, followed by a brief review of the research on mental health outcomes that result from gratitude practice. Following an analysis of our case study of the use of gratitude as a psychotherapeutic intervention, we present various self-strategies and techniques for consciously choosing and cultivating gratitude. We conclude by describing ways in which gratitude might be capitalized upon for beneficial outcomes in therapeutic settings.

The impact of maximum rectal distention and tandem angle on rectal dose delivered in 3D planned gynecologic high dose-rate brachytherapy.

OBJECTIVE: Computed tomography-based treatment planning for cervical cancer has allowed investigation into the volumetric radiation dose delivered to the rectum. The goal of intracavitary brachytherapy is to maximize the tumor dose while decreasing the dose to normal tissue like the rectum. We investigated the effects of tandem angle and maximum rectal distention on rectal dose delivered in HDR brachytherapy for locally advanced cervical cancer. MATERIALS AND METHODS: Between July 2007 and January 2010, 97 brachytherapy treatment planning computed tomographic scans from the first and last implant of 51 patients with locally advanced cervical cancer were reviewed. The rectum was manually contoured from the ischial tuberosity to the bottom of the sacroiliac joint. The maximum rectal distention was determined by measuring the largest anterior-posterior diameter of the rectum superior to the tandem ring and inferior to the end of the applicator. A volumetric measurement of the maximum and mean rectal dose, dose to 2 cc (D2cc), dose to 1cc (D1cc) of the rectum was calculated. The tandem angle and the Internal Commission on Radiation Units and Measurement rectal point were recorded, and a dose volume histogram was referenced. RESULTS: The mean maximum rectal distention was 3.01 cm. The mean D1cc, D2cc, mean rectal dose, maximum rectal dose, and Internal Commission on Radiation Units and Measurement rectal dose were 3.03 Gy, 2.78 Gy, 4.19 cGy, 1.40 cGy, and 2.99 Gy per treatment, respectively. In a multivariate analysis controlling for surface area, tandem angle, and body mass index, there was a significant increase in D2cc with increasing rectal distention (P = 0.016). There were no significant findings when observing the effects of tandem angle on D2cc. CONCLUSION: Rectal distention significantly affects D2cc delivered in HDR brachytherapy. In contrast, tandem angle does not. Concerted efforts to decrease rectal distention should be considered during treatment planning and delivery.

The impact of body mass index on rectal dose in locally advanced cervical cancer treated with high-dose-rate brachytherapy.

PURPOSE: The impact of body mass index (BMI) on rectal dose in brachytherapy for cervical cancer is unknown. We assessed the association of BMI on rectal dose and lower gastrointestinal (GI) toxicity. METHODS AND MATERIALS: Between 2007 and 2010, 51 patients with 97 brachytherapy planning images were reviewed. Volumetric measurements of the maximum percentage, mean percentage, dose to 2cc (D2cc), and dose to 1cc (D1cc) of the rectum, and the Internal Commission on Radiation Units and Measurement (ICRU) rectal point were recorded. Linear mixed effect models, analysis of variance, and regression analyses were used to determine the correlation between multiple observations or to detect a difference in the mean. The GI acute and late toxicity were prospectively recorded and retrospectively analyzed. RESULTS: The average BMI (kg/m(2)) was 27.7 with a range of 17.4-46.6. Among the patients, 8% were morbidly obese, 25% obese, 25% overweight, 40% normal weight, and 2% underweight. The mean D1cc, D2cc, mean rectal dose (%), maximum rectal dose (%), and ICRU rectum was 3.03 Gy, 2.78 Gy, 20%, 60%, and 2.99 Gy, respectively. On multivariate analysis, there was a significant decrease in the D1cc and D2cc rectal dose (p=0.016), ICRU rectal point dose (p=0.022), and mean rectal dose percentage (p=0.021) with an increase in BMI. There was, however, no statistically significant relationship between BMI and GI toxicity. CONCLUSIONS: Obesity decreases the rectal dose given in high-dose-rate brachytherapy for locally advanced cervical cancer because of an increase in fatty tissue in the recto-uterine space. There is no significant correlation between BMI and acute or late GI toxicity.

Skin dose effects of postmastectomy chest wall radiation therapy using brass mesh as an alternative to tissue equivalent bolus.

PURPOSE: The use of brass mesh as a bolus is relatively uncommon in postmastectomy chest wall radiation therapy (PMRT). This study aimed to characterize the skin dose effects of using 2-mm fine brass mesh as an alternative to the traditional tissue-equivalent bolus during chest wall PMRT. METHODS AND MATERIALS: Data were collected from patients who received PMRT using brass mesh at the University of California Davis Department of Radiation Oncology between January 2008 and June 2011. Several patient characteristics including age, body habitus, and ethnicity were analyzed along with several disease and treatment characteristics to determine whether or not they had an impact on the skin reaction observed during radiation treatment. Additionally, in vivo surface dose measurements were obtained for 16 of the 48 patients (33%). RESULTS: Forty-eight female patients aged 28-83 received PMRT using brass mesh. As expected, the severity of skin toxicity increased with subsequent doses of radiation with all patients beginning treatment with no skin reaction (National Cancer Institute scores [NCIS] = 0) and the majority of patients completing treatment with either faint to moderate erythema (n = 19, 40%, NCIS = 1) or moderate to brisk erythema (n = 23, 48%, NCIS = 2). In vivo dosimetry analysis revealed surface doses between 81% and 122% of the prescribed dose, with an average of 99% of the prescribed radiation dose and standard deviation of 10% being delivered. CONCLUSIONS: For postmastectomy chest wall radiation therapy, brass mesh is an effective alternative to tissue-equivalent bolus. The brass mesh achieved moderate erythema in the majority of patients at the end of treatment and the surface dose was validated using in vivo dosimetry.

Gamma knife radiosurgery for recurrent glossopharyngeal neuralgia after microvascular decompression.

BACKGROUND: We report the first application of Gamma Knife radiosurgery (GKR) for recurrent glossopharyngeal neuralgia (GN) after microvascular decompression (MVD). The patient is a 51-year-old male with left-sided GN. He underwent MVD and did well for almost 4 years. Later on, the patient started to experience recurrent intolerable throat pain, frequently 10/10 in intensity. Based on the application of radiosurgery for trigeminal neuralgia, GKR was offered to the patient. METHODS: After careful identification of the nerve with the assistance of a neuroradiologist, we targeted the nerve root complex, which is the cisternal portion of the nerve, using the Coherent Oscillatory State Acquisition for the Manipulation of Image Contrast (COSMIC) pulse sequence with contiguous 1-mm slices obtained by an 1.5 Tesla MRI. The radiosurgery was planned utilizing the Leksell Gamma Plan version 8.1. A single shot with a 4-mm collimator was used to deliver 80 Gy to the 100% isodose line. RESULTS: Four weeks after the treatment, the patient began to notice significant pain relief. At the 12-month follow-up, the patient's pain, which was intolerable prior to radiosurgery, was mild and occasional. CONCLUSION: GKR, which is now widely used for refractory trigeminal neuralgia, can be considered for refractory or recurrent GN. With a multidisciplinary approach and advanced neuroimaging, GKR is feasible for GN after MVD, despite the shortness of the intracranial cisternal nerve portion. Further studies are necessary to establish the role of GKR for refractory GN after MVD; however, given its rarity and the lack of experience with GKR for this condition, retrospective studies with dozens of patients are almost impossible at this time.

Development of a patient-specific two-compartment anthropomorphic breast phantom.

The purpose of this paper is to develop a technique for the construction of a two-compartment anthropomorphic breast phantom specific to an individual patient's pendant breast anatomy. Three-dimensional breast images were acquired on a prototype dedicated breast computed tomography (bCT) scanner as part of an ongoing IRB-approved clinical trial of bCT. The images from the breast of a patient were segmented into adipose and glandular tissue regions and divided into 1.59 mm thick breast sections to correspond to the thickness of polyethylene stock. A computer-controlled water-jet cutting machine was used to cut the outer breast edge and the internal regions corresponding to glandular tissue from the polyethylene. The stack of polyethylene breast segments was encased in a thermoplastic 'skin' and filled with water. Water-filled spaces modeled glandular tissue structures and the surrounding polyethylene modeled the adipose tissue compartment. Utility of the phantom was demonstrated by inserting 200 µm microcalcifications as well as by measuring point dose deposition during bCT scanning. Affine registration of the original patient images with bCT images of the phantom showed similar tissue distribution. Linear profiles through the registered images demonstrated a mean coefficient of determination (r(2)) between grayscale profiles of 0.881. The exponent of the power law describing the anatomical noise power spectrum was identical in the coronal images of the patient's breast and the phantom. Microcalcifications were visualized in the phantom at bCT scanning. The real-time air kerma rate was measured during bCT scanning and fluctuated with breast anatomy. On average, point dose deposition was 7.1% greater than the mean glandular dose. A technique to generate a two-compartment anthropomorphic breast phantom from bCT images has been demonstrated. The phantom is the first, to our knowledge, to accurately model the uncompressed pendant breast and the glandular tissue distribution for a specific patient. The modular design of the phantom allows for studies of a single breast segment and the entire breast volume. Insertion of other devices, materials and tissues of interest into the phantom provide a robust platform for future breast imaging and dosimetry studies.

Kilovoltage rotational external beam radiotherapy on a breast computed tomography platform: a feasibility study.

PURPOSE: To demonstrate the feasibility of a dedicated breast computed tomography (bCT) platform to deliver rotational kilovoltage (kV) external beam radiotherapy (RT) for partial breast irradiation, whole breast irradiation, and dose painting. METHODS AND MATERIALS: Rotational kV-external beam RT using the geometry of a prototype bCT platform was evaluated using a Monte Carlo simulator. A point source emitting 178 keV photons (approximating a 320-kVp spectrum with 4-mm copper filtration) was rotated around a 14-cm voxelized polyethylene disk (0.1 cm tall) or cylinder (9 cm tall) to simulate primary and primary plus scattered photon interactions, respectively. Simulations were also performed using voxelized bCT patient images. Beam collimation was varied in the x-y plane (1-14 cm) and in the z-direction (0.1-10 cm). Dose painting for multiple foci, line, and ring distributions was demonstrated using multiple rotations with varying beam collimation. Simulations using the scanner's native hardware (120 kVp filtered by 0.2-mm copper) were validated experimentally. RESULTS: As the x-y collimator was narrowed, the two-dimensional dose profiles shifted from a cupped profile with a high edge dose to an increasingly peaked central dose distribution with a sharp dose falloff. Using a 1-cm beam, the cylinder edge dose was <7% of the dose deposition at the cylinder center. Simulations using 120-kVp X-rays showed distributions similar to the experimental measurements. A homogeneous dose distribution (<2.5% dose fluctuation) with a 20% decrease in dose deposition at the cylinder edge (i.e., skin sparing) was demonstrated by weighted summation of four dose profiles using different collimation widths. Simulations using patient bCT images demonstrated the potential for treatment planning and image-guided RT. CONCLUSIONS: Rotational kV-external beam RT for partial breast irradiation, dose painting, and whole breast irradiation with skin sparing is feasible on a bCT platform with the potential for high-resolution image-guided RT.

Failure mode and effect analysis for delivery of lung stereotactic body radiation therapy.

PURPOSE: To improve the quality and safety of our practice of stereotactic body radiation therapy (SBRT), we analyzed the process following the failure mode and effects analysis (FMEA) method. METHODS: The FMEA was performed by a multidisciplinary team. For each step in the SBRT delivery process, a potential failure occurrence was derived and three factors were assessed: the probability of each occurrence, the severity if the event occurs, and the probability of detection by the treatment team. A rank of 1 to 10 was assigned to each factor, and then the multiplied ranks yielded the relative risks (risk priority numbers). The failure modes with the highest risk priority numbers were then considered to implement process improvement measures. RESULTS: A total of 28 occurrences were derived, of which nine events scored with significantly high risk priority numbers. The risk priority numbers of the highest ranked events ranged from 20 to 80. These included transcription errors of the stereotactic coordinates and machine failures. CONCLUSION: Several areas of our SBRT delivery were reconsidered in terms of process improvement, and safety measures, including treatment checklists and a surgical time-out, were added for our practice of gantry-based image-guided SBRT. This study serves as a guide for other users of SBRT to perform FMEA of their own practice.

Abdominal pediatric cancer surveillance using serial computed tomography: evaluation of organ absorbed dose and effective dose.

Computed tomography (CT) is used extensively in cancer diagnosis, staging, evaluation of response to treatment, and in active surveillance for cancer reoccurrence. A review of CT technology is provided, at a level of detail appropriate for a busy clinician to review. The basis of x-ray CT dosimetry is also discussed, and concepts of absorbed dose and effective dose (ED) are distinguished. Absorbed dose is a physical quantity (measured in milligray [mGy]) equal to the x-ray energy deposited in a mass of tissue, whereas ED uses an organ-specific weighting method that converts organ doses to ED measured in millisieverts (mSv). The organ weighting values carry with them a measure of radiation risk, and so ED (in mSv) is not a physical dose metric but rather is one that conveys radiation risk. The use of CT in a cancer surveillance protocol was used as an example of a pediatric patient who had kidney cancer, with surgery and radiation therapy. The active use of CT for cancer surveillance along with diagnostic CT scans led to a total of 50 CT scans performed on this child in a 7-year period. It was estimated that the patient received an average organ dose of 431 mGy from these CT scans. By comparison, the radiation therapy was performed and delivered 50.4 Gy to the patient's abdomen. Thus, the total dose from CT represented only 0.8% of the patient's radiation dose.

Verification of monitor unit calculations for non-IMRT clinical radiotherapy: report of AAPM Task Group 114.

The requirement of an independent verification of the monitor units (MU) or time calculated to deliver the prescribed dose to a patient has been a mainstay of radiation oncology quality assurance. The need for and value of such a verification was obvious when calculations were performed by hand using look-up tables, and the verification was achieved by a second person independently repeating the calculation. However, in a modern clinic using CT/MR/PET simulation, computerized 3D treatment planning, heterogeneity corrections, and complex calculation algorithms such as convolution/superposition and Monte Carlo, the purpose of and methodology for the MU verification have come into question. In addition, since the verification is often performed using a simpler geometrical model and calculation algorithm than the primary calculation, exact or almost exact agreement between the two can no longer be expected. Guidelines are needed to help the physicist set clinically reasonable action levels for agreement. This report addresses the following charges of the task group: (1) To re-evaluate the purpose and methods of the "independent second check" for monitor unit calculations for non-IMRT radiation treatment in light of the complexities of modern-day treatment planning. (2) To present recommendations on how to perform verification of monitor unit calculations in a modern clinic. (3) To provide recommendations on establishing action levels for agreement between primary calculations and verification, and to provide guidance in addressing discrepancies outside the action levels. These recommendations are to be used as guidelines only and shall not be interpreted as requirements.

Dwell position inaccuracy in the Varian GammaMed HDR ring applicator.

Varian has issued two Product Notification Letters warning of known inaccuracies in dwell positions for their GammaMed HDR ring applicator. This inaccuracy was measured for two sets of applicators. Autoexposed radiographs were taken of the HDR source at different dwell positions and analyzed per Varian recommendations using tools within the BrachyVision treatment planning program. Comparison between programmed and actual dwell positions showed the actual positions shifted distally by an average of 0.34 cm (0.17 cm-0.59 cm) across all positions in all rings. A correction method was developed and tested. During planning, the tip of the ring was extrapolated distally beyond its actual position in the patient image set and a proximal offset of the same distance was applied to the dwell positions. A global shift of 0.3 mm corrected all but the most proximal actual dwell position to within +2 mm of the planned position.

Information technology resource management in radiation oncology.

The ever-increasing data demands in a radiation oncology (RO) clinic require medical physicists to have a clearer understanding of the information technology (IT) resource management issues. Clear lines of collaboration and communication among administrators, medical physicists, IT staff, equipment service engineers and vendors need to be established. In order to develop a better understanding of the clinical needs and responsibilities of these various groups, an overview of the role of IT in RO is provided. This is followed by a list of IT related tasks and a resource map. The skill set and knowledge required to implement these tasks are described for the various RO professionals. Finally, various models for assessing one's IT resource needs are described. The exposition of ideas in this white paper is intended to be broad, in order to raise the level of awareness of the RO community; the details behind these concepts will not be given here and are best left to future task group reports.