Home About us Contact
|
Home About us Contact | ||
|
|
||
Dose Distribution (dose + distribution)
Selected AbstractsOPTIMIZING ELECTRON BEAM IRRADIATION OF "TOMMY ATKINS" MANGOES (MANGIFERA INDICA L.)JOURNAL OF FOOD PROCESS ENGINEERING, Issue 4 2007MARIA A. MORENO ABSTRACT We determined the optimum irradiation treatment for decontamination of physiologically mature fresh "Tommy Atkins" mangoes, without detriment to the fruits' sensory and chemical properties. Mangoes were irradiated at 1.0, 1.5 and 3.1 kGy using a 10-MeV linear accelerator (14-kW LINAC, double beam mode). Mangoes were stored for 21 days at 12C and 62.7% relative humidity with nonirradiated fruits as controls. Dose distribution within the fruit was determined using Monte Carlo techniques. Irradiation did not affect the overall sensory quality of mangoes at doses up to 1.5 kGy. Only fruits irradiated at 3.1 kGy were unacceptable by the panelists. Irradiation at 3.1 kGy enhanced the fruit's aroma characteristics. Irradiation at all levels caused a significant (P , 0.05) decrease (,50,70%) in ascorbic acid content by the end of storage. Mangoes irradiated at 1.5 and 3.1 kGy had slightly higher levels of phenolics than the control (27.4 and 18.3%, respectively). E-beam irradiation of Tommy Atkins mangoes up to 3.0 kGy causes no detriment to the fruit's overall sensory and chemical quality. [source] Radiation exposure from work-related medical X-rays at the Portsmouth Naval Shipyard,AMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 3 2005Robert D. Daniels BS Abstract Background Previous analyses suggest that worker radiation dose may be significantly increased by routine occupational X-ray examinations. Medical exposures are investigated for 570 civilian workers employed at the Portsmouth Naval Shipyard (PNS) at Kittery, Maine. The research objective was to determine the radiation exposure contribution of work-related chest X-rays (WRX) relative to conventional workplace radiation sources. Methods Methods were developed to estimate absorbed doses to the active (hematopoietic) bone marrow from X-ray examinations and workplace exposures using data extracted from worker dosimetry records (8,468) and health records (2,453). Dose distributions were examined for radiation and non-radiation workers. Results Photofluorographic chest examinations resulted in 82% of the dose from medical sources. Radiation workers received 26% of their collective dose from WRX and received 66% more WRX exposure than non-radiation workers. Conclusions WRX can result in a significant fraction of the total dose, especially for radiation workers who were more likely to be subjected to routine medical monitoring. Omission of WRX from the total dose is a likely source of bias that can lead to dose category misclassification and may skew the epidemiologic dose,response assessment for cancers induced by the workplace. Am. J. Ind. Med. 47:206,216, 2005. Published 2005 Wiley-Liss, Inc. [source] Appropriate dosing of antiarrhythmic drugs in Japan requires therapeutic drug monitoring,JOURNAL OF CLINICAL PHARMACY & THERAPEUTICS, Issue 1 2005M. Takada PhD Summary Objective:, In general, drugs are used in accordance with an approved dosage regimen in expectation of an appropriate balance between efficacy and toxicity. However, dose control of drugs with a narrow therapeutic range and marked intersubject variability in pharmacokinetics should be established through individualization of dosing based on therapeutic drug monitoring (TDM). The purpose of this study was to examine differences between the approved dosage regimen and the doses of antiarrhythmic drugs and digoxin used in clinical practice and to examine the influence of TDM on dosing. Methods:, Prescription research of antiarrhythmic drugs was performed at five national hospitals in Japan. Prescriptions for antiarrhythmic drugs (cibenzoline, disopyramide, pirmenol, mexiletine, aprindine, flecainide, pilsicainide, amiodarone and digoxin) were counted for the study period. The mean dose and dose distribution of the drugs were determined in each hospital. Comparisons were made of mean dose obtained in the study with the dosage approved by the authority. In addition, the percentage of patients that received TDM was determined. Results:, A difference was seen between the approved dosage and the actual dose. For all drugs except flecainide, the mean dose was smaller than the approved dosage. For all drugs except digoxin, remarkable variations were seen in the dose distribution among the hospitals. Digoxin showed a similar dose distribution among the five hospitals. Overall, the percentage of patients that received TDM was low except for Hospital A. However, TDM of digoxin was relatively common at four of the hospitals. Conclusions:, It is concluded that, with the exception of digoxin, the appropriate dosing regimen for antiarrhythmic drugs is not yet established. The establishment of appropriate dosing regimens for antiarrhythmic drugs requires the more widespread adoption of TDM. [source] TREATMENT OF CULTIVATED HIGHBUSH BLUEBERRIES (VACCINIUM CORYMBOSUM L.) WITH ELECTRON BEAM IRRADIATION: DOSIMETRY AND PRODUCT QUALITYJOURNAL OF FOOD PROCESS ENGINEERING, Issue 2 2008M.A. MORENO ABSTRACT We determined the dose distribution within a tray of highbush blueberries (Vaccinium corymbosum L.) exposed to electron beam irradiation at medium levels (1.0,3.2 kGy) using Monte Carlo and computer tomography scanning technology. We also evaluated the quality of irradiated and nonirradiated (control) fruits stored at 5C and 70% relative humidity during 14 days by a series of chemical analyses. Blueberries packed in plastic clamshell containers (trays) were irradiated using a 10-MeV linear accelerator with single-beam fixture (top only). Irradiation of blueberries at 1.1 kGy had no significant (P > 0.05) effect on the fruit quality with the exception of ascorbic acid, which decreased by 17% by the end of storage. Irradiation had an enhancing effect on the total phenolic and tannin content of all the irradiated fruits (10,20% increases). The calculated dose distribution in a pack of blueberries confirmed that the dose is not uniformly distributed within the pack because of density inhomogeneities (flesh, skin air). Dose levels at the bottom of the trays were 18 (±8%) higher than at the top. These results suggest that careful dose distribution examination must be conducted prior to setting up of an irradiation run for the packed fruits. Excellent agreement was found between measured and calculated doses at different electron beam conveyor speeds. PRACTICAL APPLICATIONS Little information is available on how electron beam irradiation penetrates a complex medium such as packed blueberries. This study presents unique results from a dose distribution calculation method using Monte Carlo simulation and computed tomography scanning techniques, which can be an effective tool for the development of proper irradiation treatment planning of packed fruits and other fresh produce. The suitability of using electron beam technology to preserve the quality characteristics and shelf life of packed blueberries was verified. [source] Basic Rules of Dosimetry in Endovascular BrachytherapyJOURNAL OF INTERVENTIONAL CARDIOLOGY, Issue 6 2000PHILIPPE A. COUCKE M.D. Endovascular brachytherapy after percutaneous coronary intervention (PCI), is becoming a standard approach for the treatment and prevention of restenosis. A variety of technical approaches are currently available to deliver ionizing irradiation to the vascular target. Basically two kinds of radioactive isotopes are available that emit gamma radiation (photons) or beta radiation (electrons). The pitfalls and solutions for the optimization of dosimetry are discussed. As might be expected, the inhomogeneous dose distribution across the target volume results in recurrence by underdosage or in complications because of overdosage. Moreover, uniformization of the target definition and reporting of the dose distribution in endovascular brachytherapy is a prerequisite for comparison between the results of the various clinical trials and is absolutely necessary to improve the therapeutic efficacy of this new approach in the prevention of restenosis after coronary angioplasty with or without stenting. [source] Evaluation of megavoltage CT imaging protocols in patients with lung cancerJOURNAL OF MEDICAL IMAGING AND RADIATION ONCOLOGY, Issue 1 2010S Smith Summary Currently, megavoltage CT studies in most centres with tomotherapy units are performed prior to every treatment for patient set-up verification and position correction. However, daily imaging adds to the total treatment time, which may cause patient discomfort as well as results in increased imaging dose. In this study, four alternative megavoltage CT imaging protocols (images obtained: during the first five fractions, once per week, alternating fractions and daily on alternative weeks) were evaluated retrospectively using the daily position correction data for 42 patients with lung cancer. The additional uncertainty introduced by using a specific protocol with respect to the daily imaging, or residual uncertainty, was analysed on a patient and population bases. The impact of less frequent imaging schedules on treatment margin calculation was also analysed. Systematic deviations were reduced with increased imaging frequency, while random deviations were largely unaffected. Mean population systematic errors were small for all protocols evaluated. In the protocol showing the greatest error, the treatment margins necessary to accommodate residual errors were 1.2, 1.3 and 1.7 mm larger in the left,right, superior,inferior and anterior,posterior directions, respectively, compared with the margins calculated using the daily imaging data. The increased uncertainty because of the use of less frequent imaging protocols may be acceptable when compared with other sources of uncertainty in lung cancer cases, such as target volume delineation and motion because of respiration. Further work needs to be carried out to establish the impact of increased residual errors on dose distribution. [source] Dosimetric comparison of intensity modulated radiotherapy techniques and standard wedged tangents for whole breast radiotherapy*JOURNAL OF MEDICAL IMAGING AND RADIATION ONCOLOGY, Issue 1 2009Andrew Fong Summary Prior to introducing intensity modulated radiotherapy (IMRT) for whole breast radiotherapy (WBRT) into our department we undertook a comparison of the dose parameters of several IMRT techniques and standard wedged tangents (SWT). Our aim was to improve the dose distribution to the breast and to decrease the dose to organs at risk (OAR): heart, lung and contralateral breast (Contra Br). Treatment plans for 20 women (10 right-sided and 10 left-sided) previously treated with SWT for WBRT were used to compare (a) SWT; (b) electronic compensators IMRT (E-IMRT); (c) tangential beam IMRT (T-IMRT); (d) coplanar multi-field IMRT (CP-IMRT); and (e) non-coplanar multi-field IMRT (NCP-IMRT). Plans for the breast were compared for (i) dose homogeneity (DH); (ii) conformity index (CI); (iii) mean dose; (iv) maximum dose; (v) minimum dose; and dose to OAR were calculated (vi) heart; (vii) lung and (viii) Contra Br. Compared with SWT, all plans except CP-IMRT gave improvement in at least two of the seven parameters evaluated. T-IMRT and NCP-IMRT resulted in significant improvement in all parameters except DH and both gave significant reduction in doses to OAR. As on initial evaluation NCP-IMRT is likely to be too time consuming to introduce on a large scale, T-IMRT is the preferred technique for WBRT for use in our department. [source] Generalized monotonic functional mixed models with application to modelling normal tissue complicationsJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES C (APPLIED STATISTICS), Issue 2 2008Matthew Schipper Summary., Normal tissue complications are a common side effect of radiation therapy. They are the consequence of the dose of radiation that is received by the normal tissue surrounding the site of the tumour. Within a specified organ each voxel receives a certain dose of radiation, leading to a distribution of doses over the organ. It is often not known what aspect of the dose distribution drives the presence and severity of the complications. A summary measure of the dose distribution can be obtained by integrating a weighting function of dose (w(d)) over the density of dose. For biological reasons the weight function should be monotonic. We propose a generalized monotonic functional mixed model to study the dose effect on a clinical outcome by estimating this weight function non-parametrically by using splines and subject to the monotonicity constraint, while allowing for overdispersion and correlation of multiple obervations within the same subject. We illustrate our method with data from a head and neck cancer study in which the irradiation of the parotid gland results in loss of saliva flow. [source] Selective transcutaneous delivery of energy to porcine soft tissues using intense ultrasound (IUS),,LASERS IN SURGERY AND MEDICINE, Issue 2 2008W. Matthew White MD Abstract Objective Various energy delivery systems have been utilized to treat superficial rhytids in the aging face. The Intense Ultrasound System (IUS) is a novel modality capable of transcutaneously delivering controlled thermal energy at various depths while sparing the overlying tissues. The purpose of this feasibility study was to evaluate the response of porcine tissues to various IUS energy source conditions. Further evaluation was performed of the built-in imaging capabilities of the device. Materials and Methods Simulations were performed on ex vivo porcine tissues to estimate the thermal dose distribution in tissues after IUS exposures to determine the unique source settings that would produce thermal injury zones (TIZs) at given depths. Exposures were performed at escalating power settings and different exposure times (in the range of 1,7.6 J) using three IUS handpieces with unique frequencies and focal depths. Ultrasound imaging was performed before and after IUS exposures to detect changes in tissue consistency. Porcine tissues were examined using nitro-blue tetrazolium chloride (NBTC) staining sensitive for thermal lesions, both grossly and histologically. The dimensions and depth of the TIZs were measured from digital photographs and compared. Results IUS can reliably achieve discrete, TIZ at various depths within tissue without surface disruption. Changes in the TIZ dimensions and shape were observed as source settings were varied. As the source energy was increased, the thermal lesions became larger by growing proximally towards the tissue surface. Maximum lesion depth closely approximated the pre-set focal depth of a given handpiece. Ultrasound imaging detected well-demarcated TIZ at depths within the porcine muscle tissue. Conclusion This study demonstrates the response of porcine tissue to various energy dose levels of Intense Ultrasound. Further study, especially on human facial tissue, is necessary in order to understand the utility of this modality in treating the aging face and potentially, other cosmetic applications. Lesers Surg. Med. 40:67,75, 2008. © 2008 Wiley-Liss, Inc. [source] Preliminary results of interstitial motexafin lutetium-mediated PDT for prostate cancerLASERS IN SURGERY AND MEDICINE, Issue 5 2006K.L. Du MD Abstract Background and Objectives Interstitial photodynamic therapy (PDT) is an emerging modality for the treatment of solid organ disease. Our group at the University of Pennsylvania has performed extensive studies that demonstrate the feasibility of interstitial PDT for prostate cancer. Our preclinical and clinical experience is herein detailed. Study Design/Materials and Methods We have treated 16 canines in preclinical studies, and 16 human subjects in a Phase I study, using motexafin lutetium-mediated PDT for recurrent prostate adenocarcinoma. Dosimetry of light fluence, drug level and oxygen distribution for these patients were performed. Results We demonstrate the safe and comprehensive treatment of the prostate using PDT. However, there is significant variability in the dose distribution and the subsequent tissue necrosis throughout the prostate. Conclusions PDT is an attractive option for the treatment of prostate adenocarcinoma. However, the observed variation in PDT dose distribution translates into uncertain therapeutic reproducibility. Our future focus will be on the development of an integrated system that is able to both detect and compensate for dose variations in real-time, in order to deliver a consistent overall PDT dose distribution. Lasers Surg. Med. 38:427,434, 2006. © 2006 Wiley-Liss, Inc. [source] Improved target volume characterization in stereotactic treatment planning of brain lesions by using high-resolution BOLD MR-venographyNMR IN BIOMEDICINE, Issue 7-8 2001Lothar R. Schad Abstract In this methodological paper I report the stereotactic correlation of different magnetic resonance imaging (MRI) techniques [MR angiography (MRA), MRI, blood bolus tagging (STAR), functional MRI, and high-resolution BOLD venography (HRBV)] in patients with cerebral arterio-venous malformations (AVM) and brain tumors. The patient's head was fixed in a stereotactic localization system which is usable in both MR-systems and linear accelerator installations. Using phantom measurements global geometric MR image distortions can be ,corrected' (reducing displacements to the size of a pixel) by calculations based on modeling the distortion as a fourth-order two-dimensional polynomial. Further object-induced local distortions can be corrected by additionally measured field maps. Using this method multimodality matching could be performed automatically as long as all images are acquired in the same examination and the patient is sufficiently immobilized to allow precise definition of the target volume. Information about the hemodynamics of the AVM was provided by a dynamic MRA with the STAR technique, leading to an improved definition of the size of the nidus, the origin of the feeding arteries, whereas HRBV imaging yielded detailed and improved information about the venous pattern and drainage. In addition, functional MRI was performed in patients with lesions close to the primary motor cortex area, leading to an improved definition of structures at risk for the high-dose application in radiosurgery. In patients with brain tumors the potential of HRBV to probe tumor angiogenesis and its use in intensity-modulated treatment planning is still hampered by the open question of how to translate a BOLD signal pattern measured in the tumor to a dose distribution, which should be addressed in future studies. Copyright © 2001 John Wiley & Sons, Ltd. [source] Definitive radiotherapy with interstitial implant boost for squamous cell carcinoma of the tongue baseHEAD & NECK: JOURNAL FOR THE SCIENCES & SPECIALTIES OF THE HEAD AND NECK, Issue 5 2005Omur Karakoyun-Celik MD Abstract Background. The purpose of this study was to examine the long-term outcome of a cohort of patients with unresected base of tongue carcinoma who received interstitial brachytherapy after comprehensive external beam radiation therapy. Methods. Between 1983 and 2000, 122 patients with primary or recurrent squamous cell carcinoma of the oropharynx or oral cavity received interstitial brachytherapy as part of their overall management. Forty patients had primary, unresected carcinoma of the base of tongue and are the subjects of this analysis. The median age was 54 years. Fifty-four percent had T3 or T4 disease, and 70% had clinical or radiographic lymphadenopathy. Twenty-four (60%) received two to three cycles of neoadjuvant chemotherapy. The oropharynx, bilateral neck, and supraclavicular fossae were comprehensively irradiated, and the tongue base received a median external beam dose of 61.2 Gy (50,72 Gy). The primary site was then boosted with an interstitial 192Iridium implant by use of a gold-button single-strand technique and three-dimensional treatment planning. The dose rate was prescribed at 0.4 to 0.5 Gy/hr. The median implant dose was 17.4 Gy (9.6,24 Gy) and adjusted to reach a total dose to the primary tumor of 80 Gy. N2 to 3 disease was managed by a planned neck dissection performed at the time of the implant. Results. The median follow-up for all patients was 56 months, and the overall survival rates were 62% at 5 years and 27% at 10 years. The actuarial primary site control was 78% at 5 years and 70% at 10 years. The overall survival and primary site control were independent of T classification, N status, or overall stage. Systemic therapy was associated with an improvement in overall survival (p = .04) and a trend toward increased primary site control with greater clinical response. There were seven documented late effects, the most frequent being grade 3 osteonecrosis (n = 2), grade 2 swallowing dysfunction (n = 2), trismus (n = 2), and chronic throat pain (n = 1). Conclusions. In an era of greatly improved dose distributions made possible by three-dimensional treatment planning and intensity-modulated radiation therapy, brachytherapy allows a highly conformal dose to be delivered in sites such as the oropharynx. If done properly, the procedure is safe and delivers a dose that is higher than what can be achieved by external beam radiation alone with the expected biologic advantages. The long-term data presented here support an approach of treating advanced tongue base lesions that includes interstitial brachytherapy as part of the overall management plan. This approach has led to a 78% rate of organ preservation at 5 years, with a 5% incidence of significant late morbidity (osteonecrosis) that has required medical management. © 2005 Wiley Periodicals, Inc. Head Neck27: XXX,XXX, 2005 [source] Centre credentialing for Trans Tasman Radiation Oncology Group trial 06.02: multicentre feasibility study of accelerated partial breast irradiationJOURNAL OF MEDICAL IMAGING AND RADIATION ONCOLOGY, Issue 4 2009T Kron Summary Introduction:, Inconsistencies in contouring target volumes for partial breast irradiation (PBI) may result in geographical misses and compromise treatment outcomes. The present study aimed to (1) determine the variability of the target volumes contoured and treatment plans generated by participating centres in credentialing for participation in a multicentre PBI trial; and (2) assess dosimetric changes when standardized target volumes were used. Methods:, The CT image sets of two de-identified patients post-breast conserving surgery were used. Contouring of the target volumes for the two cases was performed and a treatment plan as per protocol specifications was generated for each case by the seven participating centres. Planning of both cases was repeated by five centres using a set of standardized target volumes to evaluate resulting dosimetric changes in the treatment plans. Results:, The surgical cavity, the part of the planning target volume used for dose evaluation and ipsilateral whole breast volumes contoured by the centres varied by 25%, 16% and 21% (1 standard deviation), respectively. The dosimetric variations found when the standardized target volumes were used were smaller than those noted when centre-specific volumes were used. The volumes of the ipsilateral lungs receiving 30% of the prescribed dose and the volumes of the ipsilateral whole breasts receiving 95% and 50% of the prescribed dose were reduced in the treatment plans developed using the standardized target volumes. Conclusions:, Given the impact of contouring on dose distributions, quality assurance procedures in clinical trials of PBI need to take into account both the technical approaches and the contouring. [source] | ||||||||||