bluuebunny/crossref_metadata_2025_split huggingface dataset:
Assessment of geometrical accuracy of magnetic resonance images for radiation therapy of lung cancers
Authors: Koch N. , Liu H. H. , Olsson L. E. , Jackson E. F. 
Published: February 2007

The purpose of this research was to investigate the geometrical accuracy of magnetic resonance (MR) images used in the radiation therapy treatment planning for lung cancer. In this study, the capability of MR imaging to acquire dynamic two‐dimensional images was explored to access the motion of lung tumors. Due to a number of factors, including the use of a large field‐of‐view for the thorax, MR images are particularly subject to geometrical distortions caused by the inhomogeneity and gradient nonlinearity of the magnetic field. To quantify such distortions, we constructed a phantom, which approximated the dimensions of the upper thorax and included two air cavities. Evenly spaced vials containing contrast agent could be held in three directions with their cross‐sections in the coronal, sagittal, and axial planes, respectively, within the air cavities. MR images of the phantom were acquired using fast spin echo (FSE) and fast gradient echo (fGRE) sequences. The positions of the vials according to their centers of mass were measured from the MR images and registered to the corresponding computed tomography images for comparison. Results showed the fGRE sequence exhibited no errors mm in the sagittal and coronal planes, whereas the FSE sequence produced images with errors between 2.0 and 4.0 mm along the phantom's perimeter in the axial plane. On the basis of these results, the fGRE sequence was considered to be clinically acceptable in acquiring images in all sagittal and coronal planes tested. However, the spatial accuracy in periphery of the axial FSE images exceeded the acceptable criteria for the acquisition parameters used in this study.PACS number(s): 87.57.–s, 87.61.–c
CT slice index and thickness: Impact on organ contouring in radiation treatment planning for prostate cancer
Authors: Berthelet E. , Liu M. , Truong P. , Czaykowski P. , Kalach N. , Yu C. , Patterson K. , Currie T. , Kristensen S. , Kwan W. , Moravan V. 
Published: February 2007

Objective: To assess the impact of CT slice index and thickness (3 mm versus 5 mm) on (i) prostate volume, dimensions, and isocenter coordinates, (ii) bladder and rectal volumes, and (iii) DRR quality, in the treatment of prostate cancer. Methods: 16 patients with prostate cancer underwent two planning CT‐scans using 3 and 5 mm slice index/thickness. Prostate, bladder, and rectum were outlined on all scans. Prostate isocenter coordinates, maximum dimensions, and volumes were compared along with bladder and rectal volumes. Bladder volumes and maximum diameters were further investigated using a second observer. A comparative analysis of DRR quality was conducted as well as a dosimetric analysis using DVH. Results: The differences in measurements of prostate volume, isocenter coordinates and maximum dimensions between the 3 and 5 mm scans, were small and not statistically significant. Similar finding was seen for rectal volume. However, bladder volume was always larger on the 3 mm scan and the findings were reproduced with the second observer . The differences in volume are caused by a slight increase in (1) the measurement of the longitudinal dimensions on the 3 mm scans, and (2) the slice by slice measured bladder area on the 3 mm scans. The latter is due to partial volume effect. The 3 mm DRR were slightly better than the 5 mm DRR. The bladder DVH differed significantly in some patients. Conclusion: Bladder volume is significantly larger on the 3 mm scans. Differences in contoured areas may be accounted for, in part, by the partial volume effect.PACS number(s): 87.57.–s, 87.53.–j
Quality assurance of registration of CT and MRI data sets for treatment planning of radiotherapy for head and neck cancers
Authors: Moore Craig S. , Liney Gary P. , Beavis Andrew W. 
Published: February 2007

We are implementing the use of magnetic resonance (MR) images for head and neck radiotherapy planning, which involves their registration with computed tomography (CT). The quality assurance (QA) of the registration process was an initial step of this program.A phantom was built, and appropriate materials were identified to produce clinically relevant MR and contrast for its constituent “anatomy.” We performed a characterization of the distortion detectable within our phantom. Finally, we assessed the accuracy of image registration by contouring structures in the registered/fused data sets using the treatment planning system. Each structure was contoured using each modality, in turn, blind of the other. The position, area, and perimeter of each structure were assessed as a measure of accuracy of the entire image registration process.Distortion effects in the MR image were shown to be minimized by choosing a suitable receiver bandwidth. Remaining distortion was deemed clinically acceptable within of the magnetic field isocenter. A coefficient of agreement (A) analysis gave values to be within 9% of unity, where

urn:x-wiley:15269914:media:acm20025:acm20025-math-0005
is the ratio of the area/perimeter of a particular structure on CT to that on MR. The center of each structure of interest agreed to within 1.8 mm.A QA process has been developed to assess the accuracy of using multimodality image registration in the planning of radiotherapy for the head and neck; we believe its introduction is feasible and safe.PACS numbers: 87.53.Xd, 87.57.Gg, 87.59.Fm; 87.61.‐c, 87.66.Xa
Quality assurance devices for dynamic conformal radiotherapy
Authors: Wong Victy Y.W. 
Published: February 2007

Two quality control devices, a light‐field device and a radiation‐field device, have been specially designed to assist the clinical implementation of conformal dynamic arc treatment (CDAT) and intensity‐modulated radiation therapy (IMRT). With these devices, the light field as well as the radiation field projected from the individual beams at any treatment position (i.e., arbitrary gantry angle) can be evaluated. The devices are attached at the front end of the couch and placed at the isocenter of the linear accelerator treatment system (LINAC). The devices are designed to be able to rotate parallel to the gantry head so that the light field and the radiation field projected from a direct beam can be assessed. The aim of this study was to evaluate the geometric precision of the beam placement and the dosimetric accuracy performed in CDAT and IMRT with the aid of these devices. The devices are placed separately from the LINAC during use and provide an independent check on the quality performance of the LINAC in three dimensions. The condition of gantry sagging and any mechanical displacement resulting in field shift can be observed and traced during gantry rotation. Mistakes that occur during the isocenter calibration can lead to significant displacement in the field projection, which would not be revealed with the conventional quality control setting (i.e., gantry 0°). This was demonstrated with the aid of the two quality control devices in the study. The influence of gravitational acceleration in the multi‐leaf collimator (MLC) leaf positioning error, which would consequently lead to inaccurate dose delivery, was investigated. The results of our study show that the existence of a gravitational influence is statistically significant, although the magnitude of the dose inaccuracy is small.PACS numbers: 87.53.Kn, 87.56.Fc, 87.66.Cd
Results of a one year survey of output for linear accelerators using IMRT and non‐IMRT techniques
Authors: Mechalakos James G. , Germain Jean St. , Burman Chandra M. 
Published: February 2007

This paper presents the results of a one year survey of treated fields for 3 treatment machines at our New Jersey regional center. One machine, predominantly, treated IMRT prostate patients using a sliding window technique. The others were not equipped to deliver IMRT. Information obtained for each treated field included patient number, modality, monitor units delivered, gantry angle and time. Data was obtained directly from our record and verify system, and analyzed using a spreadsheet. We studied workload (MU/wk), patient load and average MU per patient as a function of time as well as angular distributions and number of treatment fractions per patient. We also calculated the fraction of time the beam was on during treatments.By the end of the survey year, the workload of the IMRT machine reached , approximately, and that of the non‐IMRT machines, around . This was largely due to the higher number of monitor units for IMRT plans. Patient loads were not significantly different for the 3 machines. Duty cycle was 14% and 16% for the non‐IMRT machines, and 27% for the IMRT machine.The difference in workload for IMRT treatments relative to non‐IMRT treatments confirms an earlier study performed at our institution using a much smaller data sample. One needs to consider the increase in leakage associated with this higher workload when designing shielding for an IMRT room.PACS numbers: 87.52.Df, 87.53.St
A TCP‐NTCP estimation module using DVHs and known radiobiological models and parameter sets
Authors: Warkentin Brad , Stavrev Pavel , Stavreva Nadia , Field Colin , Fallone B. Gino 
Published: February 2007

Radiotherapy treatment plan evaluation relies on an implicit estimation of the tumor control probability (TCP) and normal tissue complication probability (NTCP) arising from a given dose distribution. A potential application of radiobiological modeling to radiotherapy is the ranking of treatment plans via a more explicit determination of TCP and NTCP values. Although the limited predictive capabilities of current radiobiological models prevent their use as a primary evaluative tool, radiobiological modeling predictions may still be a valuable complement to clinical experience. A convenient computational module has been developed for estimating the TCP and the NTCP arising from a dose distribution calculated by a treatment planning system, and characterized by differential (frequency) dose‐volume histograms (DDVHs). The radiobiological models included in the module are sigmoidal dose response and Critical Volume NTCP models, a Poisson TCP model, and a TCP model incorporating radiobiological parameters describing linear‐quadratic cell kill and repopulation. A number of sets of parameter values for the different models have been gathered in databases. The estimated parameters characterize the radiation response of several different normal tissues and tumor types. The system also allows input and storage of parameters by the user, which is particularly useful because of the rapidly increasing number of parameter estimates available in the literature. Potential applications of the system include the following: comparing radiobiological predictions of outcome for different treatment plans or types of treatment; comparing the number of observed outcomes for a cohort of patient DVHs to the predicted number of outcomes based on different models/parameter sets; and testing of the sensitivity of model predictions to uncertainties in the parameter values. The module thus helps to amalgamate and make more accessible current radiobiological modeling knowledge, and may serve as a useful aid in the prospective and retrospective analysis of radiotherapy treatment plans.PACS number: 87.53.Tf
Dosimetric benefits of respiratory gating: a preliminary study
Authors: Butler Laura E. , Forster Kenneth M. , Stevens Craig W. , Bloch Charles , Liu H. Helen , Tucker Susan L. , Komaki Ritsuko , Liao Zhongxing , Starkschall George 
Published: February 2007

In this study, we compared the amount of lung tissue irradiated when respiratory gating was imposed during expiration with the amount of lung tissue irradiated when gating was imposed during inspiration. Our hypothesis was that the amount of lung tissue spared increased as inspiration increased. Computed tomography (CT) image data sets were acquired for 10 patients diagnosed with primary bronchogenic carcinoma. Data sets were acquired during free breathing, during breath‐holds at 0% tidal volume and 100% tidal volume, and, when possible, at deep inspiration corresponding to approximately 60% vital capacity. Two treatment plans were developed on the basis of each of the gated data sets: one in which the treatment portals were those of the free‐breathing plan, and the other in which the treatment portals were based on the gated planning target volumes. Dose‐mass histograms of the lungs calculated at 0% tidal volume were compared to those calculated at deep inspiration and at 100% tidal volume. Data extracted from the dose‐mass histograms were used to determine the most dosimetrically beneficial point to gate, the reduction in the amount of irradiated lung tissue that resulted from gating, and any disease characteristics that might predict a greater need for gating. The data showed a reduction in the mass of normal tissue irradiated when treatment portals based on the gated planning target volume were used. More normal lung tissue was spared at deep inspiration than at the other two gating points for all patients, but normal lung tissue was spared at every point in the respiratory cycle. No significant differences in the amount of irradiated tissue by disease characteristic were identified. Respiratory gating of thoracic radiation treatments can often improve the quality of the treatment plan, but it may not be possible to determine which patients may benefit from gating prior to performing the actual treatment planning.PACS numbers 87.53 –j; 87.53.Tf
Anthropomorphic breast phantoms for quality assurance and dose verification
Authors: Bencomo José A. , Chu Connel , Tello Victor M. , Cho Sang Hyun , Ibbott Geoffrey S. 
Published: February 2007

An evaluation of two anthropomorphic breast phantoms, which have been designed for quality assurance and dose verification of radiotherapy treatment of breast cancer patients, is presented. These phantoms are identical in terms of their dimensions and shape and composed of several layers of either Plastic Water™ or tissue‐equivalent material. Both water‐and tissue‐equivalent phantoms include lung‐ and rib‐equivalent components. The phantoms simulate large, medium and small breasts. The value of the phantoms as breast treatment quality assurance tools was assessed by dose measurements with ionization chamber and thermoluminescence dosimeters (TLD) at different points inside the phantom. Measurements were made by irradiating the phantoms under conditions representing the different treatment techniques found by the Radiological Physics Center (RPC) during its dosimetry quality audits. Most irradiations were performed with the water‐equivalent breast phantom. One experiment was performed under consistent irradiation conditions to compare the tissue‐equivalent phantom with the water‐equivalent phantom. Measurements were compared with the dose estimated by the RPC's manual calculations used to check clinical charts of patients entered in a National Surgical Adjuvant Breast and Bowel Project (NSABP) protocol. Measurements were also compared with isodose distributions generated by a commercial radiation treatment planning (RTP) system. In the homogeneous three‐dimensional (3‐D) phantom, fairly good agreement (within 5%) was observed at the NSABP dose prescription point between measurements and 2‐D dose estimation by manual calculations. At the same dose prescription point, but located in the heterogeneous 3‐D phantom, agreement between measurements and a 3‐D RTP system was within about 3%. Manual calculation resulted in overestimation of up to 6%. The general agreement between the TLD measurements and the 2‐D RTP values was within 3% at various off‐axis points, with the exception of a few points far off‐axis, near the high‐dose gradient region at the surface of the phantom.PACS number(s): 87.53Dq, 87.66Xa, 87.53Xd
Surface buildup dose dependence on photon field delivery technique for IMRT
Authors: Yokoyama Shigeru , Roberson Peter L. , Litzenberg Dale W. , Moran Jean M. , Fraass Benedick A. 
Published: February 2007

The more complex delivery techniques required for implementation of intensity‐modulated radiotherapy (IMRT) based on inverse planning optimization have changed the relationship between dose at depth and dose at buildup regions near the surface. Surface buildup dose is dependent on electron contamination primarily from the unblocked view of the flattening filter and secondarily from air and collimation systems. To evaluate the impact of beam segmentation on buildup dose, measurements were performed with fields, which were delivered with 3 static or strips, 5 static strips, 10 static strips, and dynamic delivery, compared with a open field. Measurements were performed in water and Solid Water using parallel plate chambers, a stereotactic diode, and thermoluminescent dosimeters (TLDs) for a 6 MV X‐ray beam. Depth doses at 2 mm depth (relative to dose at 10 cm depth) were lower by 6%, 7%, 11%, and 10% for the above field delivery techniques, respectively, compared to the open field. These differences are most influenced by differences in multileaf collimator (MLC) transmission contributing to the useful beam. An example IMRT field was also studied to assess variations due to delivery technique (static vs. dynamic) and intensity level. Buildup dose is weakly dependent on the multileaf delivery technique for efficient IMRT fields.PACS numbers: 87.53.‐j, 87.53.Dq
Real‐time motion detection of functional MRI data
Authors: Steger Theodore R. , Jackson Edward F. 
Published: February 2007

The objective of this work was to implement a motion‐detection algorithm on a commercial real‐time functional magnetic resonance imaging (fMRI) processing package for neurosurgical planning applications. A real‐time motion detection module was implemented on a commercial real‐time processing package. Simulated functional data sets with introduced translational, in‐plane rotational, and through‐plane rotational motion were created. The coefficient of variation (COV) of the center of intensity was used as a motion quantification metric. Coefficients of variation were calculated before and after image registration to determine the effectiveness of the motion correction; the limits of correctability were also determined. The motion‐detection module allowed for real‐time quantification of the motion in an fMRI experiment. Along with knowledge of the limits of correctability, this enables determination of whether an experiment needs to be reacquired while the patient is in the scanner. This study establishes the feasibility of using real‐time motion detection for presurgical planning fMRI and establishes the limits of correctable motion.PACS number: 87.61.‐c
Stereotactic IMRT for prostate cancer: Dosimetric impact of multileaf collimator leaf width in the treatment of prostate cancer with IMRT
Authors: Wang L. , Movsas B. , Jacob R. , Fourkal E. , Chen L. , Price R. , Feigenberg S. , Konski A. , Pollack A. , Ma C. 
Published: February 2007

The focus of this work is the dosimetric impact of multileaf collimator (MLC) leaf width on the treatment of prostate cancer with intensity‐modulated radiation therapy (IMRT). Ten patients with prostate cancer were planned for IMRT delivery using two different MLC leaf widths—4 mm and 10 mm— representing the Radionics micro‐multileaf collimator (mMLC) and Siemens MLC, respectively. Treatment planning was performed on the XKnifeRT2 treatment‐planning system (Radionics, Burlington, MA). All beams and optimization parameters were identical for the mMLC and MLC plans. All the plans were normalized to ensure that 95% of the planning target volume (PTV) received 100% of the prescribed dose. The differences in dose distribution between the two different plans were assessed by dose–volume histogram (DVH) analysis of the target and critical organs. We specifically compared the volume of rectum receiving 40 Gy , 50 Gy , 60 Gy , the dose received by 17% and 35% of rectum ( and ), and the maximum dose to 1 cm3 of the rectum for a prescription dose of 74 Gy. For the urinary bladder, the dose received by 25% of bladder , , and the maximum dose to 1 cm3 of the organ were recorded. For PTV we compared the maximum dose to the “hottest” 1 cm3 and the dose to 99% of the PTV . The dose inhomogeneity in the target, defined as the ratio of the difference in and to the prescribed dose, was also compared between the two plans. In all cases studied, significant reductions in the volume of rectum receiving doses less than 65 Gy were seen using the mMLC. The average decrease in the volume of the rectum receiving 40 Gy, 50 Gy, and 60 Gy using the mMLC plans was 40.2%, 33.4%, and 17.7%, respectively, with for and and for . The mean dose reductions for and for the rectum using the mMLC were 20.4% and 18.3% , respectively. There were consistent reductions in all dose indices studied for the bladder. The target dose inhomogeneity was improved in the mMLC plans by an average of 29%. In the high‐dose range, there was no significant difference in the dose deposited in the “hottest” 1 cm3 of the rectum between the two plans for all cases . In conclusion, the use of the mMLC for IMRT of the prostate resulted in significant improvement in the DVH parameters of the prostate and critical organs, which may improve the therapeutic ratio.PACS number: 87.53.Tf
A tissue‐equivalent phantom series for mammography dosimetry
Authors: Argo William P. , Hintenlang Kathleen , Hintenlang David E. 
Published: February 2007

A breast tissue‐equivalent series (BRTES) of phantoms is manufactured to mimic both the attenuation and the density of the range of glandular and adipose tissue compositions encountered in mammography. The BRTES simulates breast tissues across the range of 20% to 70% glandularity and can be assembled in a variety of thicknesses to represent a compressed breast thickness corresponding to glandularity to simulate various patient demographics. The fabrication techniques are presented, and the physical properties of the completed series of phantoms are described. The BRTES phantoms provide a dosimetry comparison with commonly used phantoms, including the American College of Radiology accreditation phantom and BR12, a 50% glandularity tissue‐equivalent material. The comparison shows that the average glandular dose is a strong function of compressed breast thickness and tissue composition. Patient doses measured using photo‐timed exposures with the BRTES phantoms can be up to a factor of 3 greater than or less than the doses predicted using conventional phantoms.PACS numbers: 87.52‐g, 87.57.‐s