bluuebunny/crossref_metadata_2025_split huggingface dataset:
Method to plan, administer, and verify supine craniospinal irradiation
Authors: Michalski Jeff M. , Klein Eric E. , Gerber Russell 
Published: February 2007

Craniospinal irradiation remains an important technique in the management of malignancies of the central nervous system. It is technically demanding, with potential for treatment field overlap or gaps to yield unacceptable dosimetric heterogeneity. A method to accurately simulate and verify the three‐field junction is described. We use a comfortable supine position to minimize patient movement. The supine position provides airway access by anesthesiology in patients requiring sedation or anesthesia. Virtual simulation is performed with a dedicated computed tomography (CT) simulator. Multiplanar sagittal and coronal CT reconstructions allow visual confirmation of three‐field matching at the cervical region. The placement of isocenters for each field, table position, and collimator angles are determined by calculation of field sizes accommodating for beam divergence. At treatment, exact matching of the three fields is assured using the record and verify confirmation of beam collimator settings and rotation, digital couch readouts, and gantry parameters. Mini‐verification silver halide (Kodak XV) films are placed behind the patient's neck and are exposed by all treatment fields (posterior flash from the lateral cranial fields and entrance from the PA spine field). These films assess field placement accuracy at the junction of these three fields. Finally, placement of radio‐opaque markers at the junction is visualized in each clinical portal radiograph. Patients readily accept the supine position as their treatment setup is eased. Field placement using digital couch settings is efficient and accurate. Daily mini‐verification films are simple, inexpensive, and allow verification of each treatment field matching. Field placement errors of greater than 1 mm can be readily identified and corrected at subsequent treatment sessions. Virtual simulation and direct junction verification with mini‐verification films allow for simple and quantitative evaluation of the junction associated with the three‐field craniospinal irradiation technique. The supine patient position does not present any difficulties in field matching or verification.PACS number(s): 87.53.–j, 87.53.–j
Technical Note: A new TLD‐phantom measurement system for determining dose distribution levels in the right and left breast from spiral CT chest imaging
Authors: Hall Jeffery L. , Navarrete Jorge L. , Surprenant Edgar , Sklansky Jack , Eisenman Jack I. 
Published: February 2007

Two specially designed plastic/aluminum phantoms positioned thermoluminescent dosimeters (TLDs) at the right and left breast location of an anthrophomorophic chest torso. Imaging was performed on a spiral CT for a volume of the chest phantom through the breast area for a noncontiguous (pitch 1.5) helical chest scan. Conventional pencil beam ionization chamber measurements were made at the same operating parameters. The doses ranged from approximately 1 to 3 cGy. For both breast phantoms, the doses were highest for the medial inner quadrants near the mediastinum. The doses were lowest for the outer quadrants (lateral aspects) of both breasts.PACS number(s): 87.66.–a, 87.52.–g
Surface and buildup dose characteristics for 6, 10, and 18 MV photons from an Elekta Precise linear accelerator
Authors: Klein Eric E. , Esthappan Jacqueline , Li Zuofeng 
Published: February 2007

Understanding head scatter characteristics of photon beams is vital to properly commission treatment planning (TP) algorithms. Simultaneously, having definitive surface and buildup region dosimetry is important to optimize bolus. The Elekta Precise linacs have unique beam flattening filter configurations for each photon beam (6, 10, and 18 MV) in terms of material and location. We performed a comprehensive set of surface and buildup dose measurements with a thin window parallel‐plate (PP) chamber to examine effects of field size (FS), source‐to‐skin distance (SSD), and attenuating media. Relative ionization data were converted to fractional depth dose (FDD) after correcting for bias effects and using the Gerbi method to account for chamber characteristics. Data were compared with a similar vintage Varian linac. At short SSDs the surface and buildup dose characteristics were similar to published data for Varian and Elekta accelerators. The FDD at surface for 6, 10, and 18 MV photons was 0.171, 0.159, and 0.199, respectively, for a , 100 cm SSD field. A blocking tray increased to 0.200, 0.200, and 0.256, while the universal wedge decreased to 0.107, 0.124, and 0.176. increased linearly with FS . decreased exponentially for 10 and 18 MV with increasing SSD. However, the 6 MV actually increased slightly with increasing SSD. This is likely due to the unique distal flattening filter for 6 MV The measured buildup curves have been used to optimize TP calculations and guide bolus decisions. Overall the and buildup doses were very similar to published data. Of interest were the relatively low 10 MV surface doses, and the 6 MV 's dependence on SSD. © 2003 American College of Medical Physics.PACS number(s): 87.53.–j, 87.66.–a
Patient specific quality assurance for the delivery of intensity modulated radiotherapy
Authors: Agazaryan Nzhde , Solberg Timothy D. , DeMarco John J. 
Published: February 2007

A patient specific quality assurance program has been developed to facilitate the clinical implementation of intensity modulated radiotherapy (IMRT) delivered using a micro‐multileaf collimator. The methodology includes several dosimetric tasks that are performed prior to the treatment of each patient. Film dosimetry is performed for each individual field and for the multifield composite plan. Individual field measurements are performed at a depth of 5 cm in a water equivalent slab phantom; export of dose calculations from the treatment planning system is similarly specified. For the composite distribution, parameters from the patient plan are applied to an IMRT phantom, and film is exposed in an axial orientation. Distributions are compared with the aid of software developed for the specific tasks. The measured and calculated dose distributions can be superimposed and positioned graphically using move, rotate, and mirror tools, as well as by specifying isocenter coordinates and using fiducial marks. Horizontal and vertical profiles are available for analysis. Dose difference, distance‐to‐agreement, and γ index, the minimum scaled multidimensional distance between a measurement and a calculation point determined in combined dose and physical distance space, are calculated along a specified isodose line and displayed. γ provides an excellent measure of disagreement between measurement and calculation for complex intensity distributions. We specify 3% dose difference and 3 mm distance as our scaling acceptability criteria. Absolute dosimetry for each composite plan is performed using an ionization chamber. To date, excellent agreement between measurements and calculations has been observed. © 2003 American College of Medical Physics.PACS number(s): 87.53.–j, 87.66.–a
Corrections to traditional methods of verifying tangential‐breast 3D monitor‐unit calculations: Use of an equivalent triangle to estimate effective fields
Authors: Prado Karl L. , Kirsner Steven M. , Erice Rolly C. 
Published: February 2007

This paper describes an innovative method for correctly estimating the effective field size of tangential‐breast fields. The method uses an “equivalent triangle” to verify intact breast tangential field monitor‐unit settings calculated by a 3D planning system to within 2%. The effects on verification calculations of loss of full scatter due to beam oblique incidence, proximity to field boundaries, and reduced scattering volumes are handled properly. The methodology is validated by comparing calculations performed by the 3D planning system with the respective verification estimates. The accuracy of this technique is established for dose calculations both with and without heterogeneity corrections. © 2003 American College of Medical Physics.PACS number(s): 87.53.– j
Wire or coated balloon? Searching for an optimal source for intravascular brachytherapy withβemitters using as an example
Authors: Lehmann J. , King C. R. 
Published: February 2007

This study identifies basic dosimetric differences between two designs for intravascular brachytherapy (IVBT) in current clinical practice and ongoing trials and their clinical implications within beta emitting systems using P‐32 as an example. The two designs are (i) the wire‐type source, where the radioactive source material is confined to a wirelike structure within the vessel lumen, and (ii) the balloon‐surface source, where the radioactive source material is distributed over a surface area (balloon‐wall) which is brought in close proximity with the vessel wall. Using Monte Carlo simulations with the EGS4 code, the target coverage, the influence of centering errors, and the perturbation of the dose distribution caused by metallic stents have been compared. The radial dose fall‐off in the target region was found to be steeper for balloon surface systems compared with wire systems. The inner lumen wall dose for a balloon surface source was 25% higher than that for a wirelike source (2.5 mm vessel diameter). However, the comparably shallower fall‐off from wire‐type systems is very sensitive to centering uncertainties. A 0.5 mm displacement, for example, will cause the dose to change by a factor of 2 at the inner vessel wall and by a factor of 1.8 at the prescription point. It is shown that the interference from metallic stents is more significant for wire‐type systems than it is for balloon‐surface‐type systems, where double the dose variation beyond the stent at the radial prescription distance may occur. Centering uncertainties dominate the dose perturbation effects for wire‐type systems. Balloon‐surface‐type designs show a more predictable dose distribution that features, however, a higher inner vessel surface dose. Since a direct clinical comparison of systems of both types is not likely, these findings should be considered when interpreting clinical results from treatments with either type of source and, possibly, for future source design. ©2003 American College of Medical Physics.PACS number(s): 87.53.–j, 87.90.+y
A seed specific dose kernel method for low‐energy brachytherapy dosimetry
Authors: DeMarco John J. , Solberg Timothy D. , Agazaryan Nzhde 
Published: February 2007

We describe a method for independently verifying the dose distributions from pre‐ and post‐implant brachytherapy source distributions. Monte Carlo calculations have been performed to characterize the three‐dimensional dose distribution in water phantom from a low‐energy brachytherapy source. The calculations are performed in a voxelized, Cartesian coordinate geometry and normalized based upon a separate Monte Carlo calculation for the seed specific air‐kerma strength to produce an absolute dose grid with units of . The seed‐specific, three‐dimensional dose grid is stored as a text file for processing using a separate visual basic program. This program requires the coordinate positions of each seed in the pre‐ or post‐plan and sums the kernel file for a three‐dimensional composite dose distribution. A kernel matrix size of with a voxel size of was chosen as a compromise between calculation time, kernel size, and truncation of the stored dose distribution as a function of radial distance from the midpoint of the seed. Good agreement is achieved for a representative pre‐ and post‐plan comparison versus a commercial implementation of the TG‐43 brachytherapy dosimetry protocol. © 2003 American College of Medical Physics.PACS number(s): 87.53.‐j, 87.52.‐g
Enhanced dynamic wedge factors at off‐axis points in asymmetric fields
Authors: Prado K. L. , Kirsner S. M. , Kudchadker R. J. , Steadham R. E. , Lane R. G. 
Published: February 2007

Several recent reports have described methods for calculating enhanced dynamic wedge factors (EDWFs). Many of these reports use the monitor‐unit (MU) fraction method to predict EDWFs as a function of field size. Although simple in approach MU fraction methods do not produce accurate EDWFs in large or asymmetric fields. A recently described technique, based on the MU fraction method works well for large and asymmetric fields, but only when the calculation point is in the center of the field. Other existing methods based on beam‐segment superposition do not have this limitation. These beam summation methods, however, are difficult to implement in routine clinical MU calculation schemes. In this paper, we present a simple calculation method that estimates EDWFs at off‐axis calculation points in both symmetric and asymmetric fields. Our method, which also is based on the MU fraction method, similarly uses empirically determined field‐size corrections but also applies wedged‐field profiles to estimate EDWFs that are independent of calculation‐point location and field symmetry. EDWF measurements for a variety of field sizes and calculation‐point locations for both 6‐ and 18‐MV x‐ray beams were performed to validate our calculations and those of our ADAC Pinnacle3 Treatment Planning System. The disagreement between the calculated and measured EDWFs over the useful clinical range of field sizes and calculation‐point locations was less than 2%. The worst disagreement was 3% and occurred at a point 8.5 cm from the center of an asymmetric 60°‐wedged field. Detailed comparisons of measurements with calculations and wedge factors obtained from the ADAC Pinnacle3 Treatment Planning System will be presented. In addition, the strengths and weaknesses of this calculation method will be discussed. © 2003 American College of Medical Physics.PACS number(s): 87.53.–j, 87.66.–a
Multimodality image fusion in dose escalation studies of brain tumors
Authors: Rajasekar D. , Datta N. R. , Gupta R. K. , Pradhan P. K. , Ayyagari S. 
Published: February 2007

This article examines the utility of integrating images from computed tomography (CT), magnetic resonance imaging (MRI), and single photon emission computed tomography (SPECT) for radiation treatment planning of brain tumors for dose escalation studies. The information obtained from these imaging modalities is complementary to each other and could provide anatomic (through CT and MRI) and metabolic (through SPECT) information of the target. This anato‐metabolic target localization could be expected to facilitate precise radiation therapy planning for brain tumors by delineating the boundary between the tumor, edema, and the normal brain parenchyma and identify the viable tumor nidus with greater degree of certainty. This could in turn lead to minimize dose to the normal tissue and permit dose escalation to the region of interest. The utility of these anato‐metabolic imaging modalities for defining the clinical target volumes along with planning target volumes for different phases of the radiation therapy is illustrated. © 2003 American College of Medical Physics.PACS number(s): 87.53.Tf, 87.57.Gg, 87.61.Pk
Interpretation of normal anatomic structures on chest radiography: Comparison of Fuji Computed Radiography (FCR) 5501D with FCR 5000 and screen‐film system
Authors: Nakashima Kazuaki , Ashizawa Kazuto , Ochi Makoto , Hashmi Rashid , Hayashi Kuniaki , Gotoh Shinichi , Honda Sumihisa , Igarashi Akito , Komaki Takao 
Published: February 2007

The purpose of this study was to investigate the usefulness of Fuji Computed Radiography (FCR) 5501D by comparing it with FCR 5000 and a screen‐film system (S/F). Posteroanterior chest radiographs often patients with no abnormality on chest CT scans were obtained with FCR 5501D, FCR 5000, and S/F. Six observers (three radiologists and three radio‐technologists) evaluated the visibility of nine normal anatomic structures (including lungs, soft tissue, and bones) and overall visibility on each image. Observers scored using a five‐point scale on each structure. FCR 5000 showed a significantly higher score in soft tissue and bone structures, and overall visibility compared with S/F, but, there was no significant difference between them in the visibility of all four normal lung structures. Compared with S/F, the score for FCR 5501D was higher in eight of the nine normal structures, including three of the four lung structures (unobscured lung, retrocardiac lung, and subdiaphragmatic lung), and overall visibility. Compared with FCR 5000, the score for FCR 5501D was higher in three normal structures, including two of the four lung structures (unobscured lung and subdiaphragmatic lung), and overall visibility. FCR 5501D was the best among the three techniques to visualize normal anatomic structures, particularly the obscured and unobscured lung. © 2003 American College of Medical Physics.PACS number(s): 87.57.–s, 87.62.+n
Comparison of computed radiography and film/screen combination using a contrast‐detail phantom
Authors: Lu Z. F. , Nickoloff E. L. , So J. C. , Dutta A. K. 
Published: February 2007

The purpose of this work is to compare computed radiography (Kodak CR 400) and film/screen combination (Speed 400) systems in regards of patient dose, technique settings, and contrast‐detail detectability. A special contrast‐detail phantom with drilled holes of varying diameter (detail) and varying depth (contrast) was utilized. Various thicknesses of the Lucite sheets were utilized to simulate scattering tissues. Images of the phantom were acquired using a range of 60–120 kVp for film/screen and CR with a conventional x‐ray tube and then for CR with additional 2 mm aluminum added filtration to the x‐ray beam. The patient entrance skin dose was measured while maintaining 1.6 o.d. for film/screen images and 1900 Exposure Index for CR images. CR phantom images were displayed on the diagnostic workstation for soft copy reading as well as printed on films for hard copy reading on viewbox. Four physicists evaluated the images by scoring the threshold target depth along the row of the same target diameter. Detection ratio was calculated by counting the number of detectable targets divided by the total number of targets in the phantom. The overall score was related to the patient entrance skin dose, kVp, and the thickness of the scattering material. The patient entrance skin dose was reduced as the additional aluminum filter was added to the x‐ray beam. Our findings suggested using a higher kVp setting and additional added filtration would reduce the patient entrance skin dose without compromising the contrast‐detail detectability, which was compensated by the contrast manipulation on soft‐copy display workstations. © 2003 American College of Medical Physics.PACS number(s): 87.57.–s, 87.62.+n
TG‐51: Experience from 150 institutions, common errors, and helpful hints
Authors: Tailor R. C. , Hanson W. F. , Ibbott G. S. 
Published: February 2007

The Radiological Physics Center (RPC) is a resource to the medical physics community for assistance regarding dosimetry procedures. Since the publication of the AAPM TG‐51 calibration protocol, the RPC has responded to numerous phone calls raising questions and describing areas in the protocol where physicists have had problems. At the beginning of the year 2000, the RPC requested that institutions participating in national clinical trials provide the change in measured beam output resulting from the conversion from the TG‐21 protocol to TG‐51. So far, the RPC has received the requested data from of the institutions in the RPC program. The RPC also undertook a comparison of TG‐21 and TG‐51 and determined the expected change in beam calibration for ion chambers in common use, and for the range of photon and electron beam energies used clinically. Analysis of these data revealed two significant outcomes: (i) a large number of the reported calibration changes for photon and electron beams were outside the RPC's expected values, and (ii) the discrepancies in the reported versus the expected dose changes were as large as 8%. Numerous factors were determined to have contributed to these deviations. The most significant factors involved the use of plane‐parallel chambers, the mixing of phantom materials and chambers between the two protocols, and the inconsistent use of depth‐dose factors for transfer of dose from the measurement depth to the depth of dose maximum. In response to these observations, the RPC has identified a number of circumstances in which physicists might have difficulty with the protocol, including concerns related to electron calibration at low energies , and the use of a cylindrical chamber at 6 MeV electrons. In addition, helpful quantitative hints are presented, including the effect of the prescribed lead filter for photon energy measurements, the impact of shifting the chamber depth for photon depth‐dose measurements, and the impact of updated stopping‐power data used in TG‐51versus that used in TG‐21, particularly for electron calibrations.PACS number(s): 87.53.–j, 87.66.–a
Computed tomography localization of radiation treatment delivery versus conventional localization with bony landmarks
Authors: Fung Albert Y. C. , Grimm S.‐Y. Lisa , Wong James R. , Uematsu M. 
Published: February 2007

A computed tomography (CT) scanner was installed in the linear accelerator room (Primatom) at Morristown. Since June 2000, we have been providing prostate, lung, and liver cancer patients with fusion of CT and linac radiation treatment. This paper describes our registration methods between planning and treatment CT images, and compares treatment localization by CT versus conventional localization by bony landmarks such as portal imaging. For image registration, we printed out beforehand the beam's eye view of the treatment fields. Prostate tumor volume from each Primatom CT slice was mapped on the printouts, and the necessary isocenter shift relative to the skin marks was deduced. No port film was necessary for our Primatom patients. For ten patients we generated digitally‐reconstructed radiographs (DRRs) with bone contrast from the CT scans, and deduced the required shift as the difference between the DRRs of the Primatom CT versus the planning CT This represented the best observable shift should portal imaging be employed. Shift from bony landmark significantly correlated with the Primatom CT shift. Positioning adjustment based on bony anatomy was generally in the same direction as the CT shift for individual patient, but frequently did not go far enough. Our study confirmed that prostate organ motion relative to the bones has an average length of 4.7 mm (with standard deviation of 2.7 mm), and indicated the superiority of CT versus conventional bony structure (such as portal imaging) localization.PACS number(s): 87.53.Kn, 87.53.–j
Behavior of the Siemens Virtual Wedge™ following an interruption to beam delivery
Authors: Richmond N. D. , Walker C. P. 
Published: February 2007

Investigations were made into the beam profile shape and dose delivered by the Siemens Virtual Wedge™ under standard operational conditions compared with those following delivery interruption on two Siemens Primus linear accelerators (Type 7445 and 8067) running different versions of control software (7.2 and 7.0, respectively). The shape of the Virtual Wedge™ profiles was found to be unaffected by beam delivery interruption. An increase in the dose delivered to the central axis was found when delivery was interrupted and subsequently resumed using information recorded in a recall data file on one of the accelerators. This dose increase was attributed to a difference in delivered monitor units recorded in the recall data file compared to those displayed on the linear accelerator control console.PACS number(s): 87.53.–j, 87.52.–g