bluuebunny/crossref_metadata_2025 huggingface dataset:
The discovery of the first luminous z ∼ 6 quasar in the UKIDSS Large Area Survey
Authors: Venemans B. P. , McMahon R. G. , Warren S. J. , Gonzalez-Solares E. A. , Hewett P. C. , Mortlock D. J. , Dye S. , Sharp R. G.
Published: February 2007

We present the initial results from our search for high-redshift, z≳ 6, quasars using near-infrared (near-IR) data from the UKIRT Infrared Deep Sky Survey Large Area Survey. Our analysis of 106 deg2 of sky from Data Release 1 has resulted in the discovery of ULAS J020332.38+001229.2, a luminous (JAB= 20.0, JVega= 19.1, M1450=−26.2) quasar at z= 5.86. Following candidate selection from the combined IR and optical catalogue data and stacking of multiple epoch Sloan Digital Sky Survey (SDSS) data, we have obtained optical spectroscopy for the only two z≳ 6 quasar candidates. The Very Large Telescope FORS2 spectrum of ULAS J020332.38+001229.2 shows broad Lyα+ N v 1240 emission at ∼8350 Å and an abrupt continuum break due to absorption by the Lyα forest. The quasar is not present in the SDSS DR5 catalogue and the continuum spectral index of α=−1.4 (Fν∝να) is redder than a composite of SDSS quasars at similar redshifts (α=−0.5). The discovery of one z∼ 6 quasar in ∼100 deg2 in a complete sample within our selection criteria down to a median depth of YAB= 20.4 (7σ) is consistent with existing SDSS results. We describe our survey methodology, including the use of optical data from the SDSS and the highly effective procedures developed to isolate the very small surface density of high-probability quasar candidates.
Chimerism and T‐cell receptor repertoire analysis after unrelated cord blood transplantation with a reduced‐intensity conditioning regimen following autologous stem cell transplantation for multiple myeloma
Authors: TOUBAI T. , HIRATE D. , SHONO Y. , OTA S. , IBATA M. , MASHIKO S. , SUGITA J. , SHIGEMATSU A. , MIURA Y. , KATO N. , UMEHARA S. , KAHATA K. , TSUTSUMI Y. , IWAO N. , TOYOSHIMA N. , TANAKA J. , ASAKA M. , IMAMURA M.
Published: February 2007

A 65‐year‐old Japanese male was diagnosed as multiple myeloma with Bence Jones kappa type, clinical stage IIIA. His disease status reached partial remission after chemotherapy. Thereafter, he received tandem transplantation, consisting of high‐dose chemotherapy with autologous stem cell transplantation (ASCT), followed by unrelated cord blood transplantation (U‐CBT). U‐CBT with a reduced‐intensity conditioning regimen (RI‐CBT) was performed in August 2003. HLA mismatch between the patient and the CBT donor was present at two serological loci (B and DR). A total nucleated CBT cell dose of 2.45 × 107/kg body weight was infused on day 0. Graft‐vs.‐host disease (GVHD) prophylaxis consisted of cyclosporine A and short‐term methotrexate. Neutrophil engraftment (>0.5 × 109/l) was obtained on day 46. He developed positive cytomegalovirus antigenemia, grade II acute GVHD involving skin and liver, varicella–zoster virus infection, septic shock, hemorrhagic cystitis caused by adenovirus and acute hepatitis B virus infection after U‐CBT. We retrospectively analyzed T‐cell receptor (TCR) repertoire diversity and found that TCR repertoire diversity decreased continuously after U‐CBT. Therefore, low‐TCR repertoire diversity in this patient appears to be associated with various infections caused by immunodeficiency.
Ecological, social, and genetic contingency of extrapair behavior in a socially monogamous bird
Authors: R. Lindstedt Erin , P. Oh Kevin , V. Badyaev Alexander
Published: February 2007

Extrapair mating strategies are common among socially monogamous birds, but vary widely across ecological and social contexts in which breeding occurs. This variation is thought to reflect a compromise between the direct costs of mates’ extrapair behavior and indirect benefits of extrapair fertilizations (EPF) to offspring fitness. However, in most free‐living populations, the complete spatial and temporal distribution of mating attempts, genetic characteristics of available mates, and their relative contribution to EPF strategies are difficult to assess. Here we examined prevalence of EPF in relation to breeding density, synchrony, and genetic variability of available mates in a wild population of house finchesCarpodacus mexicanuswhere all breeding attempts are known and all offspring are genotyped. We found that 15% of 59 nests contained extra‐pair offspring and 9% of 212 offspring were sired by extra‐pair males. We show experimentally that paired males and females avoided EPF displays in the presence of their social partners, revealing direct selection against EPF behavior. However, at the population level, the occurrence of EPF did not vary with nests dispersion, initiation date, synchrony, or with distance between the nests of extrapair partners. Instead, the occurrence of EPF closely covaried with genetic relatedness of a pool of available mates and offspring of genetically dissimilar mating tended to be resistant to a novel pathogen. These results corroborate findings that, in this population, strong fitness benefits of EPF are specific to each individual, thus highlighting the ecological, social, and genetic contingency of costs and benefits of an individual's extrapair behaviors.
Lack of melanized keratin and barbs that fall off: how the racketed tail of the turquoise‐browed motmot Eumomota superciliosa is formed
Authors: G. Murphy Troy
Published: February 2007

The racket‐tipped tail of the motmots is uniquely shaped and its formation has attracted much attention. Barbs that grow along the wire of the motmot's two central tail feathers are weakly attached and shed soon after development. The cause of the weak attachment of these barbs is unclear. I induced feather growth by plucking the central tail feathers from seven turquoise‐browed motmots Eumomota superciliosa and then collected the regrown feathers before the barbs along the wire had fully shed. I compared the barb‐rachis junction (petiole of the ramus) along the distal flag (the racket‐tip of the tail) where barbs are not shed, to the barb‐rachis junction along the wire where barbs would later be shed. In these two regions, I examined the size and structure of the attachment of the barb to the rachis with a scanning electron microscope (SEM). I also used a light microscope to score the grayness of the proximal rami of these two regions to estimate the amount of melanized keratin. SEM imaging showed that the barbs are attached to the rachis with a larger supporting flange along the distal flag compared to along the wire. Images from a light microscope showed that the rami along the distal flag were black, whereas rami along the wire were translucent or gray. The lower gray‐scale color score of the rami along the wire is likely due to reduced melanized keratin. These data suggest that that the barbs along the wire are weakly attached due to a combination of a reduced structural attachment and a lack of structurally enhancing melanin.
Guide to clinical use of electronic portal imaging
Authors: Herman Michael G. , Kruse Jon J. , Hagness Christopher R.
Published: February 2007

The Electronic Portal Imaging Device (EPID) provides localization quality images and computer‐aided analysis, which should in principal, replace portal film imaging. Modern EPIDs deliver superior image quality and an array of analysis tools that improve clinical decision making. It has been demonstrated that the EPID can be a powerful tool in the reduction of treatment setup errors and the quality assurance and verification of complex treatments. However, in many radiation therapy clinics EPID technology is not in routine clinical use. This low utilization suggests that the capability and potential of the technology alone do not guarantee its full adoption. This paper addresses basic considerations required to facilitate clinical implementation of the EPID technology and gives specific examples of successful implementations. © 2000 American College of Medical Physics.

PACS number(s): 87.53.–j, 87.57.–s
On the need for monitor unit calculations as part of a beam commissioning methodology for a radiation treatment planning system
Authors: Starkschall George , Steadham Roy E. , Wells Nathan H. , O'Neill Laura , Miller Linda A. , Rosen Isaac I.
Published: February 2007

This paper illustrates the need for validating the calculation of monitor units as part of the process of commissioning a photon beam model in a radiation treatment planning system. Examples are provided in which this validation identified subtle errors, either in the dose model or in the implementation of the dose algorithm. These errors would not have been detected if the commissioning process only compared relative dose distributions. A set of beam configurations, with varying field sizes, source‐to‐skin distances, wedges, and blocking, were established to validate monitor unit calculations for two different beam models in two different radiation treatment planning systems. Monitor units calculated using the treatment planning systems were compared with monitor units calculated from point dose calculations from tissue‐maximum ratio (TMR) tables. When discrepancies occurred, the dose models and the code were analyzed to identify the causes of the discrepancies. Discrepancies in monitor unit calculations were both significant (up to 5%) and systematic. Analysis of the dose computation software found: (1) a coordinate system transformation error, (2) mishandling of dose‐spread arrays, (3) differences between dose calculations in the commissioning software and the planning software, and (4) shortcomings in modeling of head scatter. Corrections were made in the beam calculation software or in the data sets to overcome these discrepancies. Consequently, we recommend incorporating validation of monitor unit calculations as part of a photon beam commissioning process.

PACS number(s): 87.53.–j, 87.66.–a
Comparison between TG‐51 and TG‐21: Calibration of photon and electron beams in water using cylindrical chambers
Authors: Cho S. H. , Lowenstein J. R. , Balter P. A. , Wells N. H. , Hanson W. F.
Published: February 2007

A new calibration protocol, developed by the AAPM Task Group 51 (TG‐51) to replace the TG‐21 protocol, is based on an absorbed‐dose to water standard and calibration factor , while the TG‐21 protocol is based on an exposure (or air‐kerma) standard and calibration factor . Because of differences between these standards and the two protocols, the results of clinical reference dosimetry based on TG‐51 may be somewhat different from those based on TG‐21. The Radiological Physics Center has conducted a systematic comparison between the two protocols, in which photon and electron beam outputs following both protocols were compared under identical conditions. Cylindrical chambers used in this study were selected from the list given in the TG‐51 report, covering the majority of current manufacturers. Measured ratios between absorbed‐dose and air‐kerma calibration factors, derived from the standards traceable to the NIST, were compared with calculated values using the TG‐21 protocol. The comparison suggests that there is roughly a 1% discrepancy between measured and calculated ratios. This discrepancy may provide a reasonable measure of possible changes between the absorbed‐dose to water determined by TG‐51 and that determined by TG‐21 for photon beam calibrations. The typical change in a 6 MV photon beam calibration following the implementation of the TG‐51 protocol was about 1%, regardless of the chamber used, and the change was somewhat smaller for an 18 MV photon beam. On the other hand, the results for 9 and 16 MeV electron beams show larger changes up to 2%, perhaps because of the updated electron stopping power data used for the TG‐51 protocol, in addition to the inherent 1% discrepancy presented in the calibration factors. The results also indicate that the changes may be dependent on the electron energy.

PACS number(s): 87.66.–a, 87.53.–j
An investigation of eye lens dose for gamma knife treatments of trigeminal neuralgia
Authors: Ma Lijun , Chin Lawrence , Sarfaraz Mehrdad , Shepard David , Yu Cedric
Published: February 2007

Stereotactic Gamma Knife radiosurgery has been widely used for treating trigeminal neuralgia (TN). A single large fractional dose of 7000 to 9000 cGy is commonly prescribed as the maximum dose for these treatments. For this reason, if a small percentage of the prescribed dose such as 2–3 % scattered to the eye, it could reach or even exceed the tolerance dose of the lens. For several TN cases, we found that the Leksell Gamma Plan system calculates the lens dose about 0.5–2 % of the maximum dose independent of the use of eye shielding. These dose values are significantly high and it motivated us to investigate the lens dose for the TN patients treated with stereotactic Gamma Knife radiosurgery. Phantom studies and in vivo dosimetry measurements were carried out for six patients treated at our institution. The average dose to the lens ipsilateral to the treated nerve was measured to be . Based on the biological model of Lyman and Emami [Int. J. Radiat. Oncol. Biol. Phys. 21, 109–122 (1991)], the probability of the lens complication (cataract) was determined to be 0.1%. Our findings suggest that few TN patients would develop cataracts after receiving Gamma Knife radiosurgery.

PACS number(s): 87.53.–j, 87.66.–a
Independent corroboration of monitor unit calculations performed by a 3D computerized planning system
Authors: Leszczynski Konrad W. , Dunscombe Peter B.
Published: February 2007

The checking of monitor unit calculations is recognized as a vital component of quality assurance in radiotherapy. Using straightforward but detailed computer‐based verification calculations it is possible to achieve a precision of 1% when compared with a three‐dimensional (3D) treatment planning system monitor unit calculation. The method is sufficiently sensitive to identify significant errors and is consistent with current recommendations on the magnitude of uncertainties in clinical dosimetry. Moreover, the approach is accurate in the sense of being highly consistent with the validated 3D treatment planning system's calculations.

PACS number(s): 87.53.–j, 87.52.–g
Evaluation of an innovative plastic cube phantom designed to improve the efficiency of accelerator QA
Authors: Huang J. C. , Reinstein L. E.
Published: February 2007

A new cubic phantom was designed to improve the efficiency on the QA measurement of accelerator. It has a variety of applications, such as dose constancy check, depth dose verifications, and symmetry and flatness evaluations. In particular, this new design makes it much easier to perform the check on output constancy vs. gantry angles as a cylindrical ion chamber positioned at the center of the phantom. The reproducibility of the setup using this phantom has been investigated. The charge effect of the phantom is found to be insignificant. It also reduces the monthly dosimetric QA time spent on a typical multimodality accelerator by approximately 40%.

PACS number(s): 87.66.–a
Comparison of RTP dose distributions in heterogeneous phantoms with thebeamMonte Carlo simulation system
Authors: Miften Moyed , Wiesmeyer Mark , Kapur Ajay , Ma C.‐M. Charlie
Published: February 2007

Therapeutic treatment plan evaluation is often based on examining the radiotherapy treatment planning (RTP) system dose distributions in the target and surrounding normal structures. To study the effects of tissue inhomogeneities on photon dose distributions, we compared FOCUS RTP system dose distributions from the measurement‐based Clarkson and model‐based MultiGrid Superposition (MGS) algorithms with those from thebeamMonte Carlo code system in a set of heterogeneous phantoms. The phantom inhomogeneities mimic relevant clinical treatment sites, which include lung slab, lung‐bone slab, bone‐lung slab, mediastinum, and tumor geometries. The benchmark comparisons were performed in lung densities of 0.20 and, and a bone density offorandand 15‐MV photon beams. Benchmark comparison results show that the MGS model andbeamdoses match better than 3% or 3 mm, and the MGS model is more accurate than the Clarkson model in all phantoms. The MGS model, unlike the Clarkson model, predicts the build‐down and build‐up of dose near tissue interfaces and penumbra broadening in lung associated with high energy beams. The Clarkson model overestimates the dose in lung by a maximum of 10% compared tobeam. Dose comparisons suggest turning‐off the effective path length inhomogeneity correction in the Clarkson model for lung treatments.

PACS number(s): 87.53.–j, 87.53.Bn
The treatment of large extraskeletal chondrosarcoma of the leg: Comparison of IMRT and conformal radiotherapy techniques
Authors: Chan Maria F. , Chui Chen‐Shou , Schupakm Karen , Amols Howard , Burman Chandra , Ling C. Clifton
Published: February 2007

Extraskeletal chondrosarcoma of the leg is a rare, malignant neoplasm with very few cases having been reported in the literature. In this study we investigate the possibility of using intensity modulated radiotherapy (IMRT) for this type of disease and demonstrate its advantages over conventional three‐dimensional (3D) conformal treatment. A case was presented of a patient with extraskeletal chondrosarcoma of the lateral compartment of the leg in which the target volume was 50 cm in length and twisted around the surrounding bones. Both the 3D conformal plan and IMRT plan were designed using the Memorial Sloan‐Kettering Cancer Center planning system. The IMRT plan produced a superior dose distribution to the patient as compared to the 3D conformal plan both in terms of dose conformity and homogeneity in the target volumes, and reduction of the maximum dose to the bone. The planning time of the IMRT plan was about 3–5 times shorter than that of the 3D conformal plan. It was demonstrated that the IMRT technique can be used not just for small tumors, but also for large and spiral‐shaped tumors close to critical organs. The IMRT method requires less planning time, and provides better target coverage with more sparing of critical structures. When planning patients with multiple target volumes receiving different prescribed doses, the IMRT technique can more easily meet this requirement.

PACS number(s): 87.53.–j, 87.90.+y
The dose distribution of medium energy electron boosts to the laryngectomy stoma
Authors: Yorke Ellen D. , Kassaee Alireza , Doyle Todd , Loevner Laurie A. , Rosenthal David I.
Published: February 2007

An en face, medium energy electron boost of approximately 10 Gy is often given to stomal and peristomal tissues. Because the boost is considered a simple treatment, CT‐based treatment planning is rarely used. Further, the results of such a plan might be inaccurate, as the complex dose distribution surrounding the stoma air cavity is poorly modeled by many treatment planning systems. We constructed three phantoms—two with a central vertical cavity to mimic the size and shape of the stoma and proximal trachea and one with a cavity inclined at 45° to the horizontal to better simulate anatomy. These were used to investigate the dose distribution surrounding the stoma. In all cases, the entrance to the stoma opening was centered in a field defined by a 7‐cm circular cutout and the phantom was irradiated at a source‐surface distance (SSD) of 100 cm with either vertically incident 9‐ or 12‐MeV electrons. Film measurements were made at a range of depths below and lateral to the cavity. For the vertical cavity phantoms, diode measurements were performed and isodose plans using CT scans of the phantoms were generated on a modern treatment planning system. For these two phantoms, the combined effects of lateral scatter from surrounding material and reduced equivalent thickness for electrons which pass directly through the cavity increases the dose within a centimeter of the bottom of cavity by as much as 50% for 9 MeV and 70% for 12 MeV. In material at the shallower (“superior”) end of the inclined cavity, a overdose was noted. The dose increase is geometry dependent and is not predicted by the available treatment planning system. The potential of such a dose increase to affect normal tissues such as the neopharynx should be considered.

PACS number(s): 87.53.–j, 87.66.–a
An image fusion study of the geometric accuracy of magnetic resonance imaging with the Leksell stereotactic localization system
Authors: Yu Cheng , Petrovich Zbigniew , Apuzzo Michael L. J. , Luxton Gary
Published: February 2007

A special acrylic phantom designed for both magnetic resonance imaging (MRI) and computed tomography (CT) was used to assess the geometric accuracy of MRI‐based stereotactic localization with the Leksell stereotactic head frame and localizer system. The acrylic phantom was constructed in the shape of a cube, 164 mm in each dimension, with three perpendicular arrays of solid acrylic rods, 5 mm in diameter and spaced 30 mm apart within the phantom. Images from two MR scanners and a CT scanner were obtained with the same Leksell head frame placement. Using image fusion provided by the Leksell GammaPlan (LGP) software, the coordinates of the intraphantom rod positions from two MRI scanners were compared to that of CT imaging. The geometric accuracy of MR images from the Siemens scanner was greatly improved after the implementation of a special software patch provided by the manufacturer. In general, much better accuracy was achieved in the transverse plane where images were acquired. Most distortion was found around the periphery while least distortion was present in the middle and most other parts of the phantom. For most intracranial lesions undergoing stereotactic radiosurgery, accuracy of target localization can be achieved within size of a voxel, especially with the Siemens scanner. However, extra caution should be taken for imaging of peripheral lesions where the distortion is the greatest.

PACS number(s): 87.61.–c, 87.57.–s
Technical innovation to calibrate the gantry angle indicators of linear accelerators
Authors: Chang Liyun , Ho Sheng‐Yow , Wu Jia‐Ming , Yu Chin‐Yen , Sung Chien‐Chen
Published: February 2007

Finding the actual zero degree of the gantry angle is important in order to perform the mechanical quality assurance (QA) of linear accelerators. To determine real zero, we must locate a “good surface” which could be defined as a plane on the surface of the gantry head that is perpendicular to the direction of radiation. The actual gantry angle could then be defined as the angle between vertical, as indicated by a plumb bob, and the direction of the beam axis that could be indicated by the position of a BB placed in the central axis and its shadow. From this we located the real zero degree and the good surface. The good surface can be applied to check the important mechanical readouts. The technique we introduce could solve the essential problems of a traditional QA technique, as well as taking up an important role in the quality assurance of a patient's treatment.

PACS number(s): 87.56.–v
Development of a treatment planning protocol for prostate treatments using intensity modulated radiotherapy
Authors: Ezzell Gary A. , Schild Steven E. , Wong William W.
Published: February 2007

We have developed a treatment planning protocol for intensity‐modulated radiation therapy of the prostate using commercially available inverse planning software. Treatment plans were developed for ten patients using the Corvus version 3.8 planning system, testing various prescription options, including tissue types, dose volume histogram values for the target and normal structures, beam arrangements, and number of intensity levels. All plans were scaled so that 95% of the clinical target volume received 75.6 Gy; mean doses to the prostate were typically 79 Gy. The reproducibility of the inverse planning algorithm was tested by repeating a set of the plans five times. Plans were deemed acceptable if they satisfied predefined dose constraints for the targets and critical organs. Figures of merit for target coverage, target dose uniformity, and organ sparing were used to rank acceptable plans. Certain systematic behaviors of the optimizer were noted: the high dose regions for both targets and critical organs were 5–10 Gy more than prescribed; reducing bladder and rectum tolerance increased the range of doses within the target; increasing the number of fields incrementally improved plan quality. A set of planning parameters was found that usually satisfied the minimum requirements. Repeating the optimization with different beam order produced similar but slightly different dose distributions, which was sometimes useful for finding acceptable solutions for difficult cases. The standard set of parameters serves as a useful starting point for individualized planning.

PACS number(s): 87.53.–j, 87.90.+y
Geometry function of a linear brachytherapy source
Authors: King R. Paul , Anderson R. Scott , Mills Michael D.
Published: February 2007

An equation is derived for the TG43 geometry function, G(r,θ), of a linear brachytherapy source in terms of its active length. This equation is validated by comparison to published values. It is then used to calculate values of the geometry function for the Model seed, which is a segmented linear source.

PACS number(s): 87.53.–j
Comment on “Independent corroboration of monitor unit calculations performed by a 3D computerized planning system” [J. Appl. Clin. Med. Phys. 1, 120‐125 (2000)]
Authors: Mihailidis Dimitris N.
Published: February 2007

PACS number(s): 87.53.–j, 87.66.–a
Evaluation of a quality control phantom for digital chest radiography
Authors: Mah Eugene , Samei Ehsan , Peck Donald J.
Published: February 2007

Rationale and Objectives: To examine the effectiveness and suitability of a quality control (QC) phantom for a routine QC program in digital radiography. Materials and Methods: The chest phantom consists of copper and aluminum cutouts arranged to resemble the appearance of a chest. Performance of the digital radiography (DR) system is evaluated using high and low contrast resolution objects placed in the “heart,” “lung,” and “subdiaphragm” areas of the phantom. In addition, the signal levels from these areas were compared to similar areas from clinical chest radiographs. Results: The test objects included within the phantom were effective in assessing image quality except within the subdiaphragm area, where most of the low contrast disks were visible. Spatial resolution for the DR systems evaluated with the phantom ranged from 2.6 lp/mm to 4 lp/mm, falling within the middle of the line pair range provided. The signal levels of the heart and diaphragm regions relative to the lung region of the phantom were significantly higher than in clinical chest radiographs (0.67 versus 0.21 and 0.28 versus 0.10 for the heart and diaphragm regions, respectively). The heart‐to‐diaphragm signal level ratio, however, was comparable to those in clinical radiographs. Conclusion: The findings suggest that the attenuation characteristics of the phantom are somewhat different from actual chests, but this did not appear to affect the post‐processing used by the imaging systems and usefulness for QC of these systems. The qualitative and quantitative measurements on the phantom for different systems were similar, suggesting that a single phantom can be used to evaluate system performance in a routine QC program for a wide range of digital radiography systems. This makes the implementation of a uniform QC program easier for institutions with a mixture of different digital radiography systems.

PACS number(s): 87.57.–s, 87.62.+n
Commissioning of a mobile electron accelerator for intraoperative radiotherapy
Authors: Mills Michael D. , Fajardo Liliosa C. , Wilson David L. , Daves Jodi L. , Spanos William J.
Published: February 2007

Radiation performance characteristics of a dedicated intraoperative accelerator were determined to prepare the unit for clinical use. The linear accelerator uses standing wave X‐band technology (wavelength approximately 3 centimeters) in order to minimize the mass of the accelerator. The injector design, smaller accelerator components, and low electron beam currents minimize radiation leakage. The unit may be used in a standard operating room without additional shielding. The mass of the accelerator gantry is 1250 Kg (weight approximately 2750 lbs) and the unit is transportable between operating rooms. Nominal electron energies are 4, 6, 9, and 12 MeV, and operate at selectable dose rates of 2.5 or 10 Gray per minute. depths in water for a 10 cm applicator are 0.7, 1.3, 1.7, and 2.0 for these energies, respectively. The depths of 80% dose are 1.2, 2.1, 3.1, and 3.9 cm, respectively. Absolute calibration using the American Association of Physicists in Medicine TG‐51 protocol was performed for all electron energies using the 10 cm applicator. Applicator sizes ranged from 3 to 10 cm diameter for flat applicators, and 3 to 6 cm diameter for 30° beveled applicators. Output factors were determined for all energies relative to the 10 cm flat applicator. Central axis depth dose profiles and isodose plots were determined for every applicator and energy combination. A quality assurance protocol, performed each day before patient treatment, was developed for output and energy constancy.

PACS number(s): 87.53.–j, 87.52.–g
Reproducibility of interactive registration of 3D CT and MR pediatric treatment planning head images
Authors: Vaarkamp Jaap
Published: February 2007

The reproducibility of an interactive image registration technique used as part of the radiotherapy treatment planning process was investigated for 3D CT and MR pediatric head images. Over a nine month period, 85 CT/MR image registrations, required for treatment planning, were repeated, 52 by the same operator and 33 by a different operator. All were performing image registrations for normal clinical care and the first registration was used clinically. Inter‐ and intra‐operator reproducibility of the translation and rotation were calculated separately. The standard deviation of the average total translation and rotation was 0.39 mm and 1.7°, and 0.58 mm and 2.8°, respectively. The maximum difference between registrations was 1.1 mm and 4.1° when repeated by the same operator, and 1.4 mm and 5.8° when repeated by another operator. The variation for the lowest resolution parameters, out of plane translation and rotations, was 2 to 3 times larger than for in‐plane movements. A registration took between 5 minutes and over half an hour for difficult cases, with a mean of 14.3 minutes. One to two millimeter reproducibility was not achieved and interactive registration was relatively time consuming. There is a clear image resolution effect on registration reproducibility, suggesting that reducing slice thickness could considerably improve registration reproducibility.

PACS number(s): 87.53.–j, 87.57. –s
Verification of the accuracy of 3D calculations of breast dose during tangential irradiation: measurements in a breast phantom
Authors: Kirsner Steven M. , Prado Karl L. , Tailor Ramesh C. , Bencomo José A.
Published: February 2007

This report specifically describes the use of a unique anthropomorphic breast phantom to validate the accuracy of three‐dimensional dose calculations performed by a commercial treatment‐planning system for intact‐breast tangential irradiation. The accuracy of monitor‐unit calculations has been corroborated using ionization chamber measurements made in this phantom. Measured doses have been compared to those calculated from a variety of treatment plans. The treatment plans utilized a 6‐MV x‐ray beam and incorporated a variety of field configurations and wedge combinations. Dose measurements at several clinically relevant points within the breast phantom have confirmed the accuracy of calculated doses generated from the variety of treatment plans. Overall agreement between measurements and calculations averaged . These results indicate that the dose per monitor‐unit calculations performed by the treatment‐planning system can be confidently utilized in the fulfillment of clinical dose prescriptions.

PACS number(s): 87.53.–j, 87.66.–a
Radiation therapy vault shielding calculational methods when IMRT and TBI procedures contribute
Authors: Rodgers James E.
Published: February 2007

The additional intensity modulated radiation therapy (IMRT) and total body irradiation (TBI) to conventional treatment clinical treatment procedures can significantly increase the contribution of accelerator head leakage radiation. Previously recommended procedures by the National Council on Radiation Protection and Measurements (NCRP) for vault design, specifically calculations of primary and secondary barrier thicknesses, are not valid when leakage radiation significantly exceeds direct radiation. Use factor distributions are also influenced by IMRT and TBI procedures. Methods are proposed to extend the NCRP barrier design formulas to resolve these problems. The medical accelerator (weekly) workload is separately determined for the direct, leakage, and scatter radiation components. Applications of the formulas to the calculation of primary and secondary barriers are discussed. The addition of IMRT to the shielding design is explored as a function of the fraction patients receiving IMRT and the MU to dose ratio. Secondary barrier thicknesses could be increased by as much as 1 TVL.

PACS number(s): 87.52.–g, 87.53.–j
Radiation safety issues regarding the cremation of the body of an I‐125 prostate implant patient
Authors: Que William
Published: February 2007

Radiation exposure to the public is estimated if the body of an I‐125 prostate implant patient is cremated. Precautions regarding the handling of cremated remains are suggested. Cremation can be performed safely at any time.

PACS number(s): 87.52.–g, 87.53.Jw
A method for checking high dose rate treatment times for vaginal applicators
Authors: Mayo Charles S. , Ulin Kenneth
Published: February 2007

A method is presented for checking the treatment time calculation for high dose rate (HDR) vaginal cylinder treatments. The method represents an independent check of the HDR planning system and can take into account nonuniform isodose line coverage around the cylinder. Only the air kerma strength of the source and information that is available from the written directive are required. The maximum discrepancy for a representative set of cylinder plans done on a Nucletron unit was 5%. A working HTML JavaScript program is included in the Appendix.

PACS number(s): 87.53.–j, 87.90.+y
Fluoroscopic evaluation of diaphragmatic motion reduction with a respiratory gated radiotherapy system
Authors: Mageras Gikas S. , Yorke Ellen , Rosenzweig Kenneth , Braban Louise , Keatley Eric , Ford Eric , Leibel Steven A. , Ling C. Clifton
Published: February 2007

We report on initial patient studies to evaluate the performance of a commercial respiratory gating radiotherapy system. The system uses a breathing monitor, consisting of a video camera and passive infrared reflective markers placed on the patient's thorax, to synchronize radiation from a linear accelerator with the patient's breathing cycle. Six patients receiving treatment for lung cancer participated in a study of system characteristics during treatment simulation with fluoroscopy. Breathing synchronized fluoroscopy was performed initially without instruction, followed by fluoroscopy with recorded verbal instruction (i.e., when to inhale and exhale) with the tempo matched to the patient's normal breathing period. Patients tended to inhale more consistently when given instruction, as assessed by an external marker movement. This resulted in smaller variation in expiration and inspiration marker positions relative to total excursion, thereby permitting more precise gating tolerances at those parts of the breathing cycle. Breathing instruction also reduced the fraction of session times having irregular breathing as measured by the system software, thereby potentially increasing the accelerator duty factor and decreasing treatment times. Fluoroscopy studies showed external monitor movement to correlate well with that of the diaphragm in four patients, whereas time delays of up to 0.7 s in diaphragm movement were observed in two patients with impaired lung function. From fluoroscopic observations, average patient diaphragm excursion was reduced from 1.4 cm (range 0.7–2.1 cm) without gating and without breathing instruction, to 0.3 cm (range 0.2–0.5 cm) with instruction and with gating tolerances set for treatment at expiration for 25% of the breathing cycle. Patients expressed no difficulty with following instruction for the duration of a session. We conclude that the external monitor accurately predicts internal respiratory motion in most cases; however, it may be important to check with fluoroscopy for possible time delays in patients with impaired lung function. Furthermore, we observe that verbal instruction can improve breathing regularity, thus improving the performance of gated treatments with this system.

PACS number(s): 87.53.–j, 87.62.+n
A translational couch technique for total body irradiation
Authors: Sarfaraz Mehrdad , Yu Cedric , Chen D. J. , Der Leon
Published: February 2007

We have constructed a computer controlled translational couch to administer total body irradiation reproducibly and safely. The system has replaced the previous stationary anterior‐posterior technique in our institution and 30 plus patients have been treated with it so far. In this technique, patients comfortably lie on a couch in supine and prone positions and are transported slowly through a narrow beam with the gantry in an upright position. Dose to the patient is determined by the couch velocity that is calculated based on physical parameters such as patient's dimensions, beam geometry, and machine dose rate. In our design, the couch velocity is continuously updated to compensate for machine dose rate fluctuations. The translational couch technique provides better dose uniformity within the patient compared to fixed beam techniques, and allows a more precise shielding block placement for organs at risk. At the same time, it presents a special challenge for dosimetry calculations. A dosimetry parameter is introduced that converts the moving beam output to the fixed beam output factor. Based on this factor, a simple dosimetry calculation method has been developed that takes advantage of conventional dosimetry parameters, eliminating extensive dosimetry measurements. Multiple point dose measurements within a phantom confirmed the validity of the calculation method.

PACS number(s): 87.53.–j, 87.66.–a
In vivo dosimetry using a single diode for megavoltage photon beam radiotherapy: Implementation and response characterization
Authors: Colussi Valdir C. , Beddar A. Sam , Kinsella Timothy J. , Sibata Claudio H.
Published: February 2007

The AAPM Task Group 40 reported that in vivo dosimetry can be used to identify major deviations in treatment delivery in radiation therapy. In this paper, we investigate the feasibility of using one single diode to perform in vivo dosimetry in the entire radiotherapeutic energy range regardless of its intrinsic buildup material. The only requirement on diode selection would be to choose a diode with the adequate build up to measure the highest beam energy. We have tested the new diodes from Sun Nuclear Corporation (called QED and ISORAD‐p–both p‐type) for low‐, intermediate‐, and high‐energy range. We have clinically used both diode types to monitor entrance doses. In general, we found that the dose readings from the ISORAD (p‐type) are closer of the dose expected than QED diodes in the clinical setting. In this paper we report on the response of these newly available ISORAD (p‐type) diode detectors with respect to certain radiation field parameters such as source‐to‐surface distance, field size, wedge beam modifiers, as well as other parameters that affect detector characteristics (temperature and detector‐beam orientation). We have characterized the response of the high‐energy ISORAD (p‐type) diode in the low‐ (1–4 MV), intermediate‐ (6–12 MV), and high‐energy (15–25 MV) range. Our results showed that the total variation of the response of high‐energy ISORAD (p‐type) diodes to all the above parameters are within in most encountered clinical patient treatment setups in the megavoltage photon beam radiotherapy. The usage of the high‐energy buildup diode has the additional benefit of amplifying the response of the diode reading in case the wrong energy is used for patient treatment. In the light of these findings, we have since then switched to using only one single diode type, namely the “red” diode; manufacturer designation of the ISORAD (p‐type) high‐energy (15–25 MV) range diode, for all energies in our institution and satellites.

PACS number(s): 87.66.–a, 87.53.–j
Experiences with the European guidelines on quality criteria for radiographic images in Tanzania
Authors: Muhogora W. E. , Nyanda A. M. , Kazema R. R.
Published: February 2007

Objective assessment of the quality of radiographic images is practically a difficult task and protocols that address this problem are few. In 1996, the European union published nearly objective image quality criteria to unify the practices in Europe. However, experience with these criteria in countries of lower health care levels is little documented. As a case study in Tanzania, we present the general performance of European guidelines in some Tanzanian hospitals to a total of 200 radiographs obtained from some common x‐ray examinations. The results show that more than 70% of chest (PA), lumbar spine (AP), and pelvis AP radiographs passed the quality criteria, while the performance of lumbar spine LAT x‐ray examinations was about 50% and therefore less satisfactory. The corresponding mean entrance dose to the patient for specified x‐ray techniques was of range 0.08–0.56 mGy, 3.1–7.7 mGy, 2.53–5.4 mGy, and 4.0–16.78 mGy for chest PA, lumbar spine AP, pelvis AP and lumbar spine LAT x‐ray examinations, respectively. Although a good number of observers were not well familiar to the guidelines, the quality criteria have been found useful and their adoption in the country recommended. The need to provide relevant education and training to staff in the radiology departments is of utmost importance.

PACS number(s): 87.57.–s, 87.52.–g
Anatomic variation of prescription points and treatment volume with fractionated high‐dose rate gynecological brachytherapy
Authors: Elhanafy Osman A. , Das Rupak K. , Paliwal Bhudatt R. , Migahed Mostafa D. , Sakr Hanim A. , Elleithy Mostafa
Published: February 2007

The purpose of this report is to evaluate the geometric movement (relative to the bony pelvis) and dose variation of brachytherapy reference points in the same patient at repeated high‐dose rate (HDR) intracavitary implants. A study was also concluded to find the variation in treatment volume from repeated fractions. Twenty‐five consecutive cervical cancer patients (all stages) treated with external beam and fractionated HDR intracavitary implants at the University of Wisconsin were reviewed. Each brachytherapy insertion had a different plan generated prior to treatment delivery. ICRU #38 prescription points (A, B, P, bladder, and rectum) were used. Dose volume histogram was generated and treated volume to the prescription dose was recorded for each fraction. Motion analysis of the various points (from a common origin) in subsequent fractions relative to the first fraction revealed a shift of 2–9 mm in a single plane. Vector analysis revealed the magnitude of the average shift ranged from 10–13 mm. These shifts resulted in a dose difference of for the bladder and rectum points, but < than 8% for the other points. Dose volume histograms revealed that with the change in the anatomy of the cervix and upper vagina during a patient's course of treatment, the treatment volume changes considerably. Thirty‐six percent of all patients (9/16) had a reduction in the size of the ovoid during the treatment course. Sixty percent of all patients (15/25) had volume changes . Sixty‐two and one half percent of patients (10/16) who did not undergo a reduction of avoid size during the entire course of the treatment had volume change . Since there is a change in the anatomy of the cervix and upper vagina during the course of a treatment along with the irre‐producibility of the packing, there is movement of the absolute position of the prescription points between fractions, thus emphasizing the importance of individual dosimetry. Moreover, due to the same reasons, there are significant changes in the treatment volume among implants for the same patient. Volume reduction caused by reduction in ovoid size alone could not be extracted from this study.

PACS number(s): 87.53.–j
Superimposition of beams to vary shot size in gamma knife stereotactic radiosurgery
Authors: Bank Morris I. , Timmerman Robert
Published: February 2007

The Leksell Gamma Knife [Elekta Corp] uses helmets as collimators to produce four standard beam sizes. The nominal beam diameters are 18, 14, 8, and 4 mm. During computer treatment planning for gamma knife stereotactic radiosurgery, the size of the treated volume may differ from the standard beam sizes. To maintain conformality of the isodose curves to the treated volume, beam sizes may be superimposed during computer treatment planning to produce beam diameters that are intermediate to the standard beams. A study of superimposed gamma knife beams was performed to confirm the accuracy of this method and to verify the accuracy of the GammaPlan treatment planning computer. Superimposed beams were simulated on the Elekta treatment planning computer, GammaPlan, version 4.12, and tested by film measurements of beam profiles for single helmet sizes and superimposed shots with various beam weightings. The weighting for each beam size is varied to attain the beam size diameter desired. The beams were defined at the 50% isodose line. The profiles of the superimposed beams were obtained and compared with the single helmet shots. The uniformity of the resulting beams was measured. The results show a linear relationship between beam size and beam weighting for the superimposed beams. The film measurements confirm the computer calculations.

PACS number(s): 87.66.–a, 87.53.–j
Prostate immobilization using a rectal balloon
Authors: McGary John. E. , Teh Bin S. , Butler E. Brian , Grant Walter
Published: February 2007

We use a rectal balloon for prostate immobilization during intensity modulated radiotherapy (IMRT) prostate treatment. To improve the accuracy of our prostate planning target volume, we have measured prostate displacements using computed tomography (CT)‐CT fusion on patients that previously received gold seed implants. The study consists of ten patients that were scanned twice per week during the course of IMRT treatment. In addition to biweekly scans, breathing studies were performed on each patient to estimate organ motion during treatment. The prostate displacement in the anterior‐posterior and the lateral direction is minimal, on the order of measurement uncertainty . The standard deviation of the superior‐inferior (SI) displacements is 1.78 mm. The breathing studies show that no organ displacement was detected during normal breathing conditions with a rectal balloon.

PACS number(s): 87.53.–j, 87.90.+y
An investigation of the reproducibility and usefulness of automatic couch motion in complex radiation therapy techniques
Authors: Woo Milton K. , Kim Bryan
Published: February 2007

Radiation therapy techniques that incorporate multiple couch motions are becoming more common, and they often involve an increasing level of complexity along with a need for automatic motion. The reproducibility of automatic couch motion is thus a growing concern. In this work we carried out various tests to assess the automatic motion of a commercial treatment couch, including tests to evaluate the digital readout reproducibility, as well as an independent verification of the reproducibility of the couch positions on repeated motions, using phantoms as well as a volunteer subject. It was shown that the couch motion is highly reproducible, with no discomfort to the patient, and can greatly improve treatment times as well as reduce errors in couch positioning.

PACS number(s): 87.52.–g, 87.53.–j