SU-E-T-86: Development and Implementation of the Use of Optically Stimulated Luminescent Detectors in the Radiological Physics Center Anthropomorphic Quality Assurance Phantoms.

PURPOSE: To study the angular dependence of optically stimulated luminescence dosimeters (OSLD) in the Radiological Physics Center anthropomorphic quality assurance pelvic phantom to provide accurate dosimetric measurements as a replacement for TLD. METHODS: A spherical phantom was constructed to investigate the angular response of the OSLD as oriented in the RPC pelvic phantom. Three OSLD per irradiation angle, placed at the center of the spherical phantom, were irradiated with 100 cGy from six different angles. The angular response at each angle was determined relative to the OSLD response when the beam was incident normally on the OSLD surface. A pelvic phantom dosimetry insert was modified to include both TLD and OSLD. Three treatment plans were developed in Pinnacle v9.0 and one in Accuray's Multiplan, each with increasing angular beam delivery (4 field, IMRT, SmartArc, CyberKnife) for the pelvic phantom using a common dose prescription and constraints. Each plan was delivered to the phantom three times, containing two TLD and two OSLD, oriented in the transverse plane, at the center of the PTV. The dose delivered to the TLD and OSLD was calculated for each treatment and then compared. RESULTS: The angular dependence correction factor for the spherical phantom was found to be uniformly 1.041 ± 0.003 from single beam edge-on irradiations. The angular dependence correction in the pelvic phantom from multiple beam orientation irradiations was 1.024 ± 0.002, such that the OSLD dose agreed with the TLD dose. Applying the OSLD pelvic phantom correction factor, the RPC measured dose to planning system calculated dose ratio was 0.995 ± 0.009. The established RPC phantom TLD dose to calculated dose ratio was 0.995 ± 0.010. CONCLUSIONS: An anthropomorphic phantom OSLD angular dependence correction factor was established such that the final OSLD dose measurements agreed with RPC's TLD dose measurements to within 1%. Work supported by grant CA 10953, awarded by NCI, DHHS.

SU-E-T-190: Design, Development, and Evaluation of a Modified, Anthropomorphic, Head, Quality Assurance Phantom for Use in Stereotactic Radiosurgery.

PURPOSE: To develop and evaluate a modified anthropomorphic head phantom for evaluation of stereotactic radiosurgery (SRS) dose planning and delivery. METHODS: A phantom was constructed from a water equivalent, plastic, head-shaped shell. The original phantom design, with only a spherical target, was modified to include a nonspherical target (pituitary) and an adjacent organ at risk (OAR) (optic chiasm), within 2 mm, simulating the anatomy encountered when treating acromegaly. The target and OAR spatial proximity provided a more realistic treatment planning and dose delivery exercise. A separate dosimetry insert contained two TLD for absolute dosimetry and radiochromic film, in the sagittal and coronal planes, for relative dosimetry. The prescription was 25Gy to 90% of the GTV with >= 10% of the OAR volume receiving >= 8Gy. The modified phantom was used to test the rigor of the treatment planning process, dosimeter reproducibility, and measured dose delivery agreement with calculated doses using a Gamma Knife, CyberKnife, and linear accelerator based radiosurgery systems. RESULTS: TLD results from multiple irradiations using either a CyberKnife or Gamma Knife agreed with the calculated target dose to within 4.7% with a maximum coefficient of variation of+/-2.0%. Gamma analysis in the coronal and sagittal film planes showed an average passing rate of 99.3% and 99.5% using +/-5%/3mm criteria, respectively. A treatment plan for linac delivery was developed meeting the prescription guidelines. Dosimeter reproducibility and dose delivery agreement for the linac is expected to have results similar to the results observed with the CyberKnife and Gamma Knife. CONCLUSIONS: A modified anatomically realistic SRS phantom was developed that provided a realistic clinical planning and delivery challenge that can be used to credential institutions wanting to participate in NCI funded clinical trials. Work supported by PHS CA010953, CA081647, CA21661 awarded by NCI. DHHS.

Workplace bullying and psychotropic drug use: the mediating role of physical and mental health status.

OBJECTIVES: The association between workplace bullying and psychotropic drug use is not well established. This study was aimed at exploring the association between workplace bullying, and its characteristics, and psychotropic drug use and studying the mediating role of physical and mental health. METHODS: The study population consisted of a random sample of 3132 men and 4562 women of the working population in the south-east of France. Workplace bullying, evaluated using the validated instrument elaborated by Leymann, and psychotropic drug use, as well as covariates, were measured using a self-administered questionnaire. Covariates included age, marital status, presence of children, education, occupation, working hours, night work, physico-chemical exposures at work, self-reported health, and depressive symptoms. Statistical analysis was performed using logistic regression analysis and was carried out separately for men and women. RESULTS: Workplace bullying was strongly associated with psychotropic drug use. Past exposure to bullying increased the risk for this use. The more frequent and the longer the exposure to bullying, the stronger the association with psychotropic drug use. Observing bullying on someone else at the workplace was associated with psychotropic drug use. Adjustment for covariates did not modify the results. Additional adjustment for self-reported health and depressive symptoms reduced the magnitude of the associations, especially for men. CONCLUSIONS: The association between bullying and psychotropic drug use was found to be significant and strong and was partially mediated by physical and mental health.

Workplace bullying and sleep disturbances: findings from a large scale cross-sectional survey in the French working population.

STUDY OBJECTIVES: The purpose of this study was to explore the associations between workplace bullying, the characteristics of workplace bullying, and sleep disturbances in a large sample of employees of the French working population. DESIGN: Workplace bullying, evaluated using the validated instrument developed by Leymann, and sleep disturbances, as well as covariates, were measured using a self-administered questionnaire. Covariates included age, marital status, presence of children, education, occupation, working hours, night work, physical and chemical exposures at work, self-reported health, and depressive symptoms. Statistical analysis was performed using logistic regression analysis and was carried out separately for men and women. SETTING: General working population. PARTICIPANTS: The study population consisted of a random sample of 3132 men and 4562 women of the working population in the southeast of France. RESULTS: Workplace bullying was strongly associated with sleep disturbances. Past exposure to bullying also increased the risk for this outcome. The more frequent the exposure to bullying, the higher the risk of experiencing sleep disturbances. Observing someone else being bullied in the workplace was also associated with the outcome. Adjustment for covariates did not modify the results. Additional adjustment for self-reported health and depressive symptoms diminished the magnitude of the associations that remained significant. CONCLUSIONS: The prevalence of workplace bullying (around 10%) was found to be high in this study as well was the impact of this major job-related stressor on sleep disturbances. Although no conclusion about causality could be drawn from this cross-sectional study, the findings suggest that the contribution of workplace bullying to the burden of sleep disturbances may be substantial.

The potential use of intensity modulated radiotherapy (IMRT) in women with pectus excavatum desiring breast-conserving therapy.

The purpose of this study was to determine if intensity modulated radiation therapy (IMRT) offers a better treatment plan compared to conventional radiotherapy for patients with pectus excavatum desiring breast-conserving therapy and to assess the feasibility of simultaneous modulated accelerated radiation therapy (SMART) boost. A patient with pectus excavatum desired breast-conserving therapy for her early stage breast cancer. She underwent lumpectomy and axillary lymph node dissection followed by chemotherapy. She was then referred for radiotherapy. A breast board (Med-Tec) with aquaplast body cast was used to limit the movement of the patient, chest wall, and breasts before planning a computed tomography (CT) scan. IMRT including dose-volume histogram (DVH) was compared to that of the conventional plan using parallel opposed tangential beams with a 15-degree wedge pair. Forty-five gray was prescribed to the whole breast to each plan, while 50 Gy was prescribed to the tumor bed using IMRT with SMART boost in 25 fractions over 5 weeks. The coverage of the whole breast was adequate for both plans. IMRT allowed a more homogeneous dose distribution within the breast at the desired dose range. With IMRT there is less volume of ipsilateral lung receiving the radiation dose that is above the tolerance threshold of 15 Gy when compared to that of the conventional plan. However, there is more volume of surrounding normal tissues (the heart, spinal cord, and contralateral breast and lung) receiving low-dose irradiation when IMRT was employed. SMART boost was feasible, allowing a mean dose of 57 Gy to be delivered to the tumor bed simultaneously along with the rest of the breast in 5 weeks. IMRT is feasible in treating early breast cancer patients with pectus excavatum by decreasing the ipsilateral lung volume receiving high-dose radiation when compared to the conventional method. SMART boost shortens the overall treatment time that may have potential radiobiological benefit.

The elements of tissue-air ratio and systematic error.

The definition of tissue-air ratio (TAR) is based on the concept of primary dose. To determine TAR, both in-phantom and in-air ionization measurements are utilized. To convert ionization in the phantom into dose and that in air into primary dose, correction factors must be applied to chamber readings in both geometries. Due to difficulties in selecting proper correction factors, TAR is subject to systematic error. The error comes from two sources of uncertainty: (1) Primary dose cannot be measured. Therefore approximate methods, such as in-air ionization measurements, are used. (2) Detectors of ionization are of finite dimensions and they are inhomogeneous. In this study, analytical expression for a systematic error is derived. Because in this derivation systematic error is an accumulative error, it is no longer necessary to convert ionization, both in air and in phantom, into a dose when calculating TARs. A method of determining systematic error is described. This method is based on the ability to produce accurate zero-field data in photon beams by means of a linear extrapolation technique. Using 60Co gamma radiation in water as an example, it is shown how to generate TAR data free of systematic error. A possibility of determining TARs for therapeutic x rays is discussed.

A comparison of intensity modulated conformal therapy with a conventional external beam stereotactic radiosurgery system for the treatment of single and multiple intracranial lesions.

PURPOSE: To compare the stereotactic radiosurgery treatment plans generated by a conventional radiosurgery treatment system with the plan generated by a system using intensity modulated beams. METHODS AND MATERIALS: Optimized conformal radiation treatment plans were generated for both single and multiple intracranial lesions using a conventional radiosurgery treatment-planning system computer and the Peacock treatment-planning computer. The Peacock system is a conformal therapy system that uses intensity modulated beams, back projection, and the simulated annealing optimization technique. The dose delivered to critical structures and the target volume were compared by means of dose volume histograms between plans generated by the two different systems. The Radiation Therapy Oncology Group (RTOG) stereotactic radiosurgery criteria were also used to evaluate each plan. RESULTS: (a) For a single small target, radiosurgery plans generated by the conventional radiosurgery system and the Peacock system were comparable. (b) For two separate small targets, where nonoverlapping arcs could be used, plans generated by the two systems were also comparable. (c) For a single large (>4 cm) irregular-shaped target, the Peacock system appeared to be able to generate a treatment plan superior to that of the conventional radiosurgery system. CONCLUSIONS: A treatment plan generated using intensity modulated beams appears to be superior to a multiple isocenter plan using a conventional radiosurgery system, for the treatment of a large irregular shaped intracranial target.