bluuebunny/crossref_metadata_2025_split huggingface dataset:
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
Dosimetric advantage of using 6 MV over 15 MV photons in conformal therapy of lung cancer: Monte Carlo studies in patient geometries
Authors: Wang Lu , Yorke Ellen , Desobry Gregory , Chui Chen‐Shou 
Published: February 2007

Many lung cancer patients who undergo radiation therapy are treated with higher energy photons (15‐18 MV) to obtain deeper penetration and better dose uniformity. However, the longer range of the higher energy recoil electrons in the low‐density medium may cause lateral electronic disequilibrium and degrade the target coverage. To compare the dose homogeneity achieved with lower versus higher energy photon beams, we performed a dosimetric study of 6 and 15 MV three‐dimensional (3D) conformal treatment plans for lung cancer using an accurate, patient‐specific dose‐calculation method based on a Monte Carlo technique. A 6 and 15 MV 3D conformal treatment plan was generated for each of two patients with target volumes exceeding 200 cm3on an in‐house treatment planning system in routine clinical use. Each plan employed four conformally shaped photon beams. Each dose distribution was recalculated with the Monte Carlo method, utilizing the same beam geometry and patient‐specific computed tomography (CT) images. Treatment plans using the two energies were compared in terms of their isodose distributions and dose‐volume histograms (DVHs). The 15 MV dose distributions and DVHs generated by the clinical treatment planning calculations were as good as, or slightly better than, those generated for 6 MV beams. However, the Monte Carlo dose calculation predicted increased penumbra width with increased photon energy resulting in decreased lateral dose homogeneity for the 15 MV plans. Monte Carlo calculations showed that all target coverage indicators were significantly worse for 15 MV than for 6 MV; particularly the portion of the planning target volume (PTV) receiving at least 95% of the prescription dosedropped dramatically for the 15 MV plan in comparison to the 6 MV Spinal cord and lung doses were clinically equivalent for the two energies. In treatment planning of tumors that abut lung tissue, lower energy (6 MV) photon beams should be preferred over higher energies (15–18 MV) because of the significant loss of lateral dose equilibrium for high‐energy beams in the low‐density medium. Any gains in radial dose uniformity across steep density gradients for higher energy beams must be weighed carefully against the lateral beam degradation due to penumbra widening.PACS number(s): 87.90.+y, 87.52.–g
CT gel dosimetry technique: Comparison of a planned and measured 3D stereotactic dose volume
Authors: Audet C. , Hilts M. , Jirasek A. , Duzenli C. 
Published: February 2007

This study presents a 3D dose mapping of complex dose distributions using an x‐ray computed tomography (CT) polymer gel dosimetry technique. Two polyacrylamide gels (PAGs) of identical composition were irradiated with the same four arc stereotactic treatment to maximum doses of 15 Gy (PAG1) and 8 Gy (PAG2). The PAGs were CT imaged using a previously defined protocol that involves image averaging and background subtraction to improve image quality. For comparison with the planned isodose distribution, the PAG images were converted to relative dose maps using a CT number‐dose calibration curve or simple division. The PAG images were then co‐registered with the planning CT images in the BrainLab® treatment planning software which automatically provides reconstructed sagittal and coronal images for 3D evaluation of measured and planned dose. The hypo‐intense high dose region in both sets of gel images agreed with the planned 80% isodose contour and was shifted by up to 1.5 and 3.0 mm in the axial and reconstructed planes, respectively. This demonstrates the ability of the CT gel technique to accurately localize the high dose region produced by the stereotactic treatment. The resulting agreement of the measured relative dose volume for PAG1 was within 3.0 mm for the 50% and 80% isodose surfaces. However, the dose contrast was too low in PAG2 to allow for accurate definition of measured relative dose surfaces. Thus, a PAG should be irradiated to higher doses if quantitative relative dose information is required. Unfortunately, this implies use of an additional PAG and its CT number dose response since doses greater than 8–10 Gy fall outside the linear regions of the response.PACS number(s): 87.53.–j, 87.57.–s, 87.59.Fm