Computerized Medical Systems Research Articles

A comparison of TPS and different measurement techniques in small-field electron beams

In recent years, small-field electron beams have been used for the treatment of superficial lesions, which requires small circular fields. However, when using very small electron fields, some significant dosimetric problems may occur. In this study, dose distributions and outputs of circular fields with dimensions of 5cm and smaller, for nominal energies of 6, 9, and 15MeV from the Siemens ONCOR Linac, were measured and compared with data from a treatment planning system using the pencil-beam algorithm in electron beam calculations. All dose distribution measurements were performed using the Gafchromic EBT film; these measurements were compared with data that were obtained from the Computerized Medical Systems (CMS) XiO treatment planning system (TPS), using the gamma-index method in the PTW VeriSoft software program. Output measurements were performed using the Gafchromic EBT film, an Advanced Markus ion chamber, and thermoluminescent dosimetry (TLD). Although the pencil-beam algorithm is used to model electron beams in many clinics, there is no substantial amount of detailed information in the literature about its use. As the field size decreased, the point of maximum dose moved closer to the surface. Output factors were consistent; differences from the values obtained from the TPS were, at maximum, 42% for 6 and 15MeV and 32% for 9MeV. When the dose distributions from the TPS were compared with the measurements from the Gafchromic EBT films, it was observed that the results were consistent for 2-cm diameter and larger fields, but the outputs for fields of 1-cm diameter and smaller were not consistent. In CMS XiO TPS, calculated using the pencil-beam algorithm, the dose distributions of electron treatment fields that were created with circular cutout of a 1-cm diameter were not appropriate for patient treatment and the pencil-beam algorithm is not convenient for monitor unit (MU) calculations in electron dosimetry.

Research of Dosimetry Parameters in Small Electron Beams

In this study, dose distributions and outputs of circular fields with dimensions of 5 cm and smaller, for 6 and 9 MeV nominal energies from the Siemens ONCOR Linac, were measured and compared with data from a treatment planning system using the pencil beam algorithm in electron beam calculations. All dose distribution measurements were performed using the GafChromic EBT film; these measurements were compared with data that were obtained from the Computerized Medical Systems (CMS) XiO treatment planning system (TPS). Output measurements were performed using GafChromic EBT film, an Advanced Markus ion chamber, and thermoluminescent dosimetry (TLD). Although it is used in many clinics, there is not a substantial amount of detailed information in the literature about use of the pencil beam algorithm to model electron beams. Output factors were consistent; differences from the values obtained from the TPS were at maximum. When the dose distributions from the TPS were compared with the measurements from the ion chamber and GafChromic EBT films, it was observed that the results were consistent with 2 cm diameter fields and larger, but the outputs for 1 cm diameter fields and smaller were not consistent.

Effectiveness of Virtual Reality Simulation Software in Radiotherapy Treatment Planning Involving Non-Coplanar Beams with Partial Breast Irradiation as a Model

Virtual reality simulation software (VRS - FocalSim Version 4.40 with VRS prototype, Computerized Medical Systems, St. Louis, MO) is a new radiation dose planning tool that allows for 3D visualization of the patient and the machine couch (treatment table) in relationship to the linear accelerator. This allows the radiation treatment planner to have a "room's-eye-view" and enhances the process of virtual simulation. The aim of this study was to compare VRS to a standard planning program (XiO - Version 4.50, Computerized Medical Systems, St. Louis, MO) in regards to the time it took to use each program, the angles chosen in each, and to determine if there was a dosimetric benefit to using VRS. Ten patients who had undergone left-sided lumpectomies were chosen to have treatment plans generated. A partial breast irradiation (PBI) treatment plan by external beam radiation therapy (EBRT) was generated for each patient using two different methods. In the first method the full plan was generated using XiO software. In the second method beam angles were chosen using the VRS software, those angles were transferred to XiO, and the remaining part of the plan was completed using XiO (since VRS does not allow dose calculations). On average, using VRS to choose angles took about 10 minutes longer than XiO. None of the five gantry angles differed significantly between the two programs, but four of the five couch angles did. Dose-volume histogram (DVH) data showed a significantly better conformality index, and trends toward decreased hot spots and increased coverage of the planed treatment volume (PTV) when using VRS. However, when angels were chosen in VRS a greater volume of the ipsilateral breast received a low dose of radiation (between 3% and 50% of the prescribed dose) (VRS = 23.06%, XiO = 19.57%, p < 0.0005). A significant advantage that VRS provided over XiO was the ability to detect potential collisions prior to actual treatment of the patient in three of the ten patients studied. The potential to save time with VRS by not having to redo plans because of a collision increases clinic efficiency.

SU-E-T-601: Dosimetric Evaluation of the Parameter Variation with Varying Calculation Grid Size in the IMRT Cases.

The aim of this study is to compare the plan results that are obtained by using different calculation grid sizes ranging from 0.15 to 0.50 cm, and the same dose calculation algorithm (Superposition), in Intensity Modulated Radiotherapy (IMRT) for different treatment sites. Results are then used to study the suitability of dose grid size with respect to site. For each of the calculation grid sizes, three different sites; namely, Lung, Prostate, and Head and Neck were analyzed. Treatment plans were created using 6MV photon beam quality and IMRT technique on the CMS XiO (Computerized Medical System, St.Louis, MO) treatment planning system. Dose volume histograms were generated for each of the cases and statistical analysis performed included mean relative difference and Homogeneity Index for target structures. Comparison was done first by using 0.30 cm calculation grid as a golden standard and keeping the same number of monitor units (MUs) per beam for each grid size, then the second part involved renormalizing plans to have the same target coverage (100% of the prescription dose covering at least 95% of the target volume) for each grid size used. Future study plans include treatment plans delivery on Varian 21 EX linear accelerator with Millennium (120) MLC and their verification with the Sun Nuclear Mapcheck 2D array. To increase the diode array resolution, 2D array will be shifted in 1 mm increments in x and y direction. Measured fields will be merged using Sun Nuclear Files Combined function and compared with intensity maps exported from the CMS XiO treatment planning system calculated with minimum segment size of 1 cm. The maximum percentage of variation recorded between calculation grid sizes used was in the case of the Head and Neck treatments. For the lung and prostate cases there was little variation in the results based on the calculation grid size chosen, specifically between 0.30, 0.20 and 0.15 cm. However head and neck and prostate cases with nodal involvement showed significant variation in the dosimetric results based on the grid size chosen. Overall results vary from case to case and also depend on the plan complexity. For larger treatment areas calculating with the grid size smaller than 0.30 cm may be impossible as time needed for calculation rises exponentially with the field size involved. IMRT places a higher requirement on dose grid resolution than conventional radiation therapy. While 0.30-0.40 cm grid was assumed adequate for conformal treatment planning, smaller dose grid is required at least in the areas of high dose. In the cases where steep dose gradients exist smaller grid size should be used while calculating and evaluating treatment plans, as the choice of the calculation grid size may in certain cases even influence clinical results.

Comparative study of convolution, superposition, and fast superposition algorithms in conventional radiotherapy, three-dimensional conformal radiotherapy, and intensity modulated radiotherapy techniques for various sites, done on CMS XIO planning system

The aim of this study is to compare the dosimetry results that are obtained by using Convolution, Superposition and Fast Superposition algorithms in Conventional Radiotherapy, Three-Dimensional Conformal Radiotherapy (3D-CRT), and Intensity Modulated Radiotherapy (IMRT) for different sites, and to study the suitability of algorithms with respect to site and technique. For each of the Conventional, 3D-CRT, and IMRT techniques, four different sites, namely, Lung, Esophagus, Prostate, and Hypopharynx were analyzed. Treatment plans were created using 6MV Photon beam quality using the CMS XiO (Computerized Medical System, St.Louis, MO) treatment planning system. The maximum percentage of variation recorded between algorithms was 3.7% in case of Ca.Lung, for the IMRT Technique. Statistical analysis was performed by comparing the mean relative difference, Conformity Index, and Homogeneity Index for target structures. The fast superposition algorithm showed excellent results for lung and esophagus cases for all techniques. For the prostate, the superposition algorithm showed better results in all techniques. In the conventional case of the hypopharynx, the convolution algorithm was good. In case of Ca. Lung, Ca Prostate, Ca Esophagus, and Ca Hypopharynx, OARs got more doses with the superposition algorithm; this progressively decreased for fast superposition and convolution algorithms, respectively. According to this study the dosimetric results using different algorithms led to significant variation and therefore care had to be taken while evaluating treatment plans. The choice of a dose calculation algorithm may in certain cases even influence clinical results.

Compensator‐based intensity‐modulated radiation therapy for malignant pleural mesothelioma post extrapleural pneumonectomy

The present work investigated the potential of compensator‐based intensity‐modulated radiation therapy (CB‐IMRT) as an alternative to multileaf collimator (MLC)–based intensity‐modulated radiation therapy (IMRT) to treat malignant pleural mesothelioma (MPM) post extrapleural pneumonectomy.Treatment plans for 4 right‐sided and 1 left‐sided MPM post‐surgery cases were generated using a commercial treatment planning system, XIO/CMS (Computerized Medical Systems, St. Louis, MO). We used a 7‐gantry‐angle arrangement with 6 MV beams to generate these plans. The maximum required field size was 30×40 cm. We evaluated IMRT plans with brass compensators (•Decimal, Sanford, FL) by examining isodose distributions, dose–volume histograms, metrics to quantify conformal plan quality, and homogeneity. Quality assurance was performed for one of the compensator plans.Conformal dose distributions were achieved with CB‐IMRT for all 5 cases, the average planning target volume (PTV) coverage being 95.1% of the PTV volume receiving the full prescription dose. The average lung V20 (volume of lung receiving 20 Gy) was 1.8%, the mean lung dose was 6.7 Gy, and the average contralateral kidney V15 was 0.6%. The average liver dose V30 was 34.0% for the right‐sided cases and 10% for the left‐sided case. The average monitor units (MUs) per fraction were 980 MUs for the 45‐Gy prescriptions (mean: 50 Gy) and 1083 MUs for the 50‐Gy prescriptions (mean: 54 Gy).Post surgery, CB‐IMRT for MPM is a feasible IMRT technique for treatment with a single isocenter. Compensator plans achieved dose objectives and were safely delivered on a Siemens Oncor machine (Siemens Medical Solutions, Malvern, PA). These plans showed acceptably conformal dose distributions as confirmed by multiple measurement techniques. Not all linear accelerators can deliver large‐field MLC‐based IMRT, but most can deliver a maximum conformal field of 40×40 cm. It is possible and reasonable to deliver IMRT with compensators for fields this size with most conventional linear accelerators.PACS numbers: 87.56.ng, 87.56.N, 87.55.D, 87.55.dk

Clinical implementation of full Monte Carlo dose calculation in proton beam therapy

The goal of this work was to facilitate the clinical use of Monte Carlo proton dose calculation to support routine treatment planning and delivery. The Monte Carlo code Geant4 was used to simulate the treatment head setup, including a time-dependent simulation of modulator wheels (for broad beam modulation) and magnetic field settings (for beam scanning). Any patient-field-specific setup can be modeled according to the treatment control system of the facility. The code was benchmarked against phantom measurements. Using a simulation of the ionization chamber reading in the treatment head allows the Monte Carlo dose to be specified in absolute units (Gy per ionization chamber reading). Next, the capability of reading CT data information was implemented into the Monte Carlo code to model patient anatomy. To allow time-efficient dose calculation, the standard Geant4 tracking algorithm was modified. Finally, a software link of the Monte Carlo dose engine to the patient database and the commercial planning system was established to allow data exchange, thus completing the implementation of the proton Monte Carlo dose calculation engine (‘DoC++’). Monte Carlo re-calculated plans are a valuable tool to revisit decisions in the planning process. Identification of clinically significant differences between Monte Carlo and pencil-beam-based dose calculations may also drive improvements of current pencil-beam methods. As an example, four patients (29 fields in total) with tumors in the head and neck regions were analyzed. Differences between the pencil-beam algorithm and Monte Carlo were identified in particular near the end of range, both due to dose degradation and overall differences in range prediction due to bony anatomy in the beam path. Further, the Monte Carlo reports dose-to-tissue as compared to dose-to-water by the planning system. Our implementation is tailored to a specific Monte Carlo code and the treatment planning system XiO (Computerized Medical Systems Inc.). However, this work describes the general challenges and considerations when implementing proton Monte Carlo dose calculation in a clinical environment. The presented solutions can be easily adopted for other planning systems or other Monte Carlo codes.

Sci-Fri PM: Planning-05: Saving trees and improving workflow.

Patient treatment preparation is a multi-step process requiring inputs from a range of disciplines and technologies. Our centre generates just over 4500 treatment plans annually and operates from two main campuses. A large, split program presents unique challenges during treatment preparation and has provided the impetus for a completely electronic treatment process. Throughout 2006 and 2007, we migrated our external beam treatment planning to the Computerized Medical Systems (CMS) product line. Utilizing a thin-client architecture, CMS supports distributed (multi-site) planning. Coincident with the treatment planning upgrade, IMPAC Multi-Access was configured to provide a paperless and filmless treatment record and electronic patient workflow. Standardized treatment objectives were also implemented in the form of site-group approved care plans. Details of the pretreatment process and the CMS / IMPAC implementation will be presented as well as a workflow time analysis. To date, treatment preparation times have been reduced by 25% (2.5 days) as a result of workflow improvements, representing a clear benefit to both staff and patients.

A MC tool for CT-based calculations of dose delivery and activation in proton therapy

The feasibility and value of offline PET/CT imaging for in-vivo, non-invasive verification of proton beam delivery is currently under investigation at Massachusetts General Hospital, Boston. Within this project we have developed a Monte Carlo framework for CT-based calculation of dose and irradiation induced positron emitter distributions using the FLUKA Monte Carlo code. Particle transport in the patient is performed on the CT grid, taking into account realistic tissue composition as well as the correlation between CT numbers and stopping power ratio to water as used by the commercial treatment planning system (XiO, Computerized Medical System Inc.). Positron emitter production is computed by combining during runtime proton fluence with experimental and evaluated cross-sections for all the major reaction channels yielding measurable tissue activation. In this paper we describe our dedicated implementation which might be easily generalised for use in other proton therapy centres or extended to include further activation reaction channels, provided that initial beam information or experimental cross sections are known. Further, we present clinical examples for calculation of delivered dose and irradiation induced PET activation.

Clinical CT-based calculations of dose and positron emitter distributions in proton therapy using the FLUKA Monte Carlo code

Clinical investigations on post-irradiation PET/CT (positron emission tomography/computed tomography) imaging for in vivo verification of treatment delivery and, in particular, beam range in proton therapy are underway at Massachusetts General Hospital (MGH). Within this project, we have developed a Monte Carlo framework for CT-based calculation of dose and irradiation-induced positron emitter distributions. Initial proton beam information is provided by a separate Geant4 Monte Carlo simulation modelling the treatment head. Particle transport in the patient is performed in the CT voxel geometry using the FLUKA Monte Carlo code. The implementation uses a discrete number of different tissue types with composition and mean density deduced from the CT scan. Scaling factors are introduced to account for the continuous Hounsfield unit dependence of the mass density and of the relative stopping power ratio to water used by the treatment planning system (XiO (Computerized Medical Systems Inc.)). Resulting Monte Carlo dose distributions are generally found in good correspondence with calculations of the treatment planning program, except a few cases (e.g. in the presence of air/tissue interfaces). Whereas dose is computed using standard FLUKA utilities, positron emitter distributions are calculated by internally combining proton fluence with experimental and evaluated cross-sections yielding 11C, 15O, 14O, 13N, 38K and 30P. Simulated positron emitter distributions yield PET images in good agreement with measurements. In this paper, we describe in detail the specific implementation of the FLUKA calculation framework, which may be easily adapted to handle arbitrary phase spaces of proton beams delivered by other facilities or include more reaction channels based on additional cross-section data. Further, we demonstrate the effects of different acquisition time regimes (e.g., PET imaging during or after irradiation) on the intensity and spatial distribution of the irradiation-induced β+-activity signal for the cases of head and neck and para-spinal tumour sites.

Validation des plans de radiothérapie conformationnelle avec modulation d'intensité avec les images portales

The goal of this study was to show the feasibility of step and shoot intensity-modulated radiation therapy pre-treatment quality control for patients using the electronic portal imaging device (iViewGT) fitted on a Sli+ linac (Elekta Oncology Systems, Crawley, UK) instead of radiographic films. Since the beginning of intensity-modulated radiation therapy treatments, the dosimetric quality control necessary before treating each new patient has been a time-consuming and therefore costly obligation. In order to fully develop this technique, it seems absolutely essential to reduce the cost of these controls, especially the linac time. Up to now, verification of the relative dosimetry field by field has been achieved by acquiring radiographic films in the isocenter plane and comparing them to the results of the XiO planning system (Computerized Medical Systems, Missouri, USA) using RIT113 v4.1 software (Radiological Imaging Technology, Colorado, USA). A qualitative and quantitative evaluation was realised for every field of every patient. A quick and simple procedure was put into place to be able to make the same verifications using portal images. This new technique is not a modification of the overall methodology of analysis. The results achieved by comparing the measurement with the electronic portal imaging device and the calculation with the treatment planning system were in line with those achieved with the films for all indicators we studied (isodoses, horizontal and vertical dose profiles and gamma index).

TH‐B‐224C‐03: Robotically Assisted Needle Placement for Prostate Brachytherapy

Purpose: To present preliminary results for a robotically‐assisted prostate brachytherapy treatment system. Method and Materials: A 4 degree‐of‐freedom (DOF) robotic device was developed to replace the ultrasound template in a commercially available prostate brachytherapy treatment system (Interplant, Computerized Medical Systems, St. Louis, MO). The robot mounts to the existing template mounting points on the ultrasound stepper, and is capable of positioning the needles at arbitrary positions and orientations. The robot is spatially co‐registered to the Interplant treatment planning software through a calibration procedure. We performed a seed‐implantation experiment on a prostate training phantom in which the needles were positioned by the robot. The needles were preloaded with one seed, then inserted manually by the operator under transrectal ultrasound (TRUS) guidance. In this experiment, ten seeds were implanted, and their implanted positions were reconstructed using data from a post‐implant CT of the phantom and the Interplant post‐implant analysis software (iPAS). Results: Using the results from the iPAS software, we measured both the relative error of each seed (with respect to the other seeds), and the absolute error of each seed with respect to the treatment plan. The relative root‐mean‐ square (RMS) transverse error was 0.8 mm (worst case 2.1 mm, 70% under 0.7mm), and the relative RMS sagittal error was 2.5 mm (worst case 4mm, 60% under 2.5 mm). The absolute transverse RMS error was 2.4 mm (worst case 4.3 mm, 50% under 2.4 mm), and the absolute sagittal RMS error was 2.5 mm (worst case 4.5 mm, 80% under 2.5 mm). However, the absolute transverse errors were characterized by an offset in each direction, most likely resulting from errors in the measurement of the robot position relative to the phantom. Conclusion: Our system for robotically‐assisted prostate brachytherapy shows potential for improved needle placement, repeatability, and accuracy.

SU‐FF‐T‐442: Use Of A 2D Array Of Diodes To Test The Accuracy Of MLC Leaf Position And Gap Width

Purpose: For MLC‐modulated IMRT fields, it is important that the leaf positioning be accurate and that the gap between opposing leaf pairs be precisely set. One test of the MLC is the “picket fence” pattern, which consists of narrow, sequentially delivered, abutting sub‐fields of radiation. Typically in current practice, a radiographic film is irradiated and visually inspected for a discontinuous radiation pattern. Here, a 2D‐array of 455 diodes (MapCheck, Sun Nuclear, Melbourne, FL) was used to detect the radiation pattern. Method and Materials: The array was oriented such that 120 diodes aligned with the center of the MLC leaves at each of their sub‐field edges. Measurements were compared against a dose distribution calculated by the XiO treatment planning system (Computerized Medical Systems, St. Louis, MO) for a picket‐fence segment pattern delivered to a flat phantom. MapCheck software was used to obtain the relative percent difference, normalized to the center diode, between the 455 diode‐measured and calculated points. Spreadsheet software was written that extracted the desired 120 sample points from the 455 measured points and performed routine data analysis in less than 30 s. Results: Four different Siemens accelerators equipped with 29‐leaf pair MLCs were measured over a two‐month period. By careful adjustment of MLC leaves, the percent difference between measurement and calculation, averaged for 120 points, could be kept within ±5% with a standard deviation of 6.0%. This standard deviation is attributable to individual MLC leaves and deviations in leaf position for various set positions across the field. The trial‐to‐trial variation is about 2% for the average difference for the 120 points. A 1‐mm leaf offset in the picket fence delivery corresponded to an average difference of about 17%. Conclusion: A rapid, quantitative method, sensitive to submillimeter changes in MLC leaf positioning and gap width has been devised.

SU‐FF‐T‐06: Megavoltage CT Imaging Enables CT‐Based Low‐Doserate Brachytherapy Planning Without CT‐Compatible Applicators

Purpose: To determine feasibility of megavoltage computed tomography (MVCT) imaging for low dose rate (LDR) brachytherapy for cervical carcinoma. Method and Materials: A helical tomotherapy treatment unit (Tomotherapy HiArt, Tomotherapy Inc., Madison, WI) using a nominal 3.5 MV x‐ray beam was used to image a dosimetry phantom containing standard, non‐CT compatible Fletcher‐Suit applicators and dummy Cs‐137 tube sources (3M Model 6500). The phantom contained several small steel BB markers which were used as dose points. The MVCT images were transferred to a commercially available treatment planning system (CMS XiO 4.2, Computerized Medical Systems, St. Louis, MO). Digitally reconstructed radiographs (DRRs) were generated from the MVCT data set, and doses (dose rates) were calculated at the phantom dose points using standard 2D, film‐based dosimetry methods. Doses were also calculated using a CT‐based, 3D dosimetry technique in which the brachytherapy source tips and ends were localized directly on MVCT images. Separate experiments were performed to verify the spatial accuracy of the MVCT image reconstruction in‐phantom. Results: In‐phantom localization accuracy was 0.6 ± 0.3 mm, slightly less than the size of an axial MVCT image pixel and less than half of the MVCT slice thickness. Point doses in‐phantom calculated by 2D and by 3D methods agreed within an average of 1.5%. The techniques developed for successful MVCT imaging in‐phantom can be used to calculate 3D dose distributions in a human patient undergoing a traditional (non‐CT compatible) Fletcher‐Suit implant. Conclusion: MVCT imaging allows CT‐based dosimetry planning without the use of special, “CT‐compatible” applicators.

Re-treatment of a lung tumour using a simple intensity-modulated radiotherapy approach

We present a lung tumour case where, although the proximal spinal cord had already reached its dose tolerance, re-treatment was indicated. Minimization of the cord dose was defined as the main constraint for this case, however additional dose to the heart was considered. A simple (4 field) intensity-modulated radiotherapy (IMRT) treatment which proved superior to the standard conformal plan was developed using the Computerized Medical Systems (CMS) XiO treatment planning system. The IMRT plan was found to be superior to the conventional conformal plan regarding tumour coverage. It provided 100% saturation of the planning target volume (PTV) by the 95% isodose cloud, whereas the latter only provided 77% coverage. A step and shoot delivery using 10 intensity levels was developed and subsequently delivered for this patient. We considered it to be a routine application of IMRT and an important example of how it can offer benefit in individual and appropriate cases where conventional treatment is inadequate.

Clinical impact of the detector size effect in 3D-CRT

Objective The detector size artificially increases the measured penumbra of radiotherapy fields. The aim of this work is to determine the influence of the detector size when planning three-dimensional conformal radiation therapy (3D-CRT) treatments. Material and methods Two anatomical sites of interest in 3D-CRT were studied: prostate and hypophysis chordoma. Conventional 3D-CRT treatments for two cases in these locations were planned with a FOCUS 4.0.0 (Computerized Medical Systems, USA) treatment planning system (TPS) equipped with Fast Fourier Transform Convolution (FFTC) and Multigrid Superposition (MGS) algorithms, making use of beams modelled from radiation profiles measured either with a 2.0 mm diameter detector (PFD 3G diode) or with a 5.5 mm diameter detector (PTW-31002 ionisation chamber). These detectors cover up the range of detector sizes commonly used to measure radiation profiles for 3D-CRT. Dose–volume histograms (DVHs), radiobiological indexes, tumor control probability (TCP) and normal tissue complication probability (NTCP) were analysed and compared for planning target volumes (PTVs) and organs at risk (OAR) studied. Results Important differences in DVH were found. OAR received higher dose levels when a 5.5 mm detector was used to measure profiles compared to the case in which a 2.0 mm detector was used. A 2 Gy increment in the mean rectal dose was found when the larger detector was used. In the same way, NTCP of brain stem in hypophysis chordoma treatments was doubled when this detector was used. Conclusion The current use of ionisation chambers of about 5 mm active diameter to get the necessary data to model treatment machines in radiotherapy treatment planning systems (TPS) implies a significant overirradiation of OAR close to the PTV in 3D-CRT treatments due to errors in the measured penumbra of beam profiles. To avoid this overirradiation, the measured profiles should either being acquired with a suitable detector size (2–3 mm active diameter) or being deconvoluted.

An IMRT dose distribution study using commercial verification software

The introduction of IMRT requires users to confirm that the isodose distributions and relative doses calculated by their planning system match the doses delivered by their linear accelerators. To this end the commercially available software, VeriSoft (PTW-Freiburg, Germany) was trialled to determine if the tools and functions it offered would be of benefit to this process. The CMS XiO (Computerized Medical System, St. Louis, MO) treatment planning system was used to generate IMRT plans that were delivered with an upgraded Elekta SL15 linac. Kodak EDR2 film sandwiched in RW3 solid water (PTW-Freiburg, Germany) was used to measure the IMRT fields delivered with 6 MV photons. The isodose and profiles measured with the film generally agreed to within +/- 3% or +/- 3 mm with the planned doses, in some regions (outside the field) the match fell to within +/- 5%. The isodose distributions of the planning system and the film could be compared on screen, allowing for electronic records of the comparison to be kept if desired. The features of this software would be of benefit to an IMRT QA program.

Comparison of two treatment techniques for breast irradiation including internal mammary nodes

Techniques to treat breast cancer inclusive of the internal mammary lymph node chain (IMC) vary. This study compared a presently accepted technique implemented at the Radiation Oncology Department at Barnes-Jewish Hospital/Washington University School of Medicine (BJ/WU) to a proposed technique for irradiation of breast tissue and the IMC. The present technique consists of parallel-opposed breast tangential beams in combination with photon and electron IMC fields angled along the chest wall. The proposed method involves a wide medial tangent field covering the IMC, with an angled electron IMC field for a portion of the treatment regimen and an opposed lateral breast-only tangent. This technique uses a multileaf collimation (MLC) reduction to treat the IMC aspect following the wide medial tangent, to supplement the IMC to a tumorcidal dose. These techniques were compared by reviewing isodoses with subsequent isodensity confirmation. Computerized tomography imaging sets of patients with various body types (chest wall, small and large breasts) for left-sided tumors were planned using a three-dimensional treatment planning system (FOCUS, Computerized Medical Systems). The plans were evaluated by comparing irradiated heart and lung volumes and the respective dose distribution at the IMC field/medial tangent junction. Specific treatment aids and photon/electron energies were employed to produce desirable isodose distributions, with a dose prescription of 4680-cGy total dose. The efficiency of the radiation treatments itself was also evaluated. The proposed technique decreases treatment time by eliminating an additional IMC field that involves repositioning and placement of a block. Phantom-based film isodensity measurements were evaluated to validate the calculated dosimetry for these techniques.

高エネルギーX線に対するRadiochromic Filmの濃度測定精度の検討

Radiochromic film (RC-film) is of great interest as a film-type dosimeter for radiation oncology applications. We present a two-dimensional image-based evaluation of the measurement accuracy of a commercial RC-film product (Gafchromic MD-55-2 film, ISP TECHNOLOGIES, Inc.) by using a commercial Laser Densitometer (Model 1710, Computerized Medical Systems, Inc.) as an optical density imaging system. The coefficient of variation of the density (pixel-value) in one sample was approximately 3% to 11% at 3 Gy or less, and 3% or less at 4 to 60 Gy. Although the coefficient of variation between three samples at the same dose was about 14% at 1 Gy, it decreased as the dose increased, reaching several percent. In 1 to 6 Gy samples, geometric imaging artifacts [interference (moire) patterns] were observed, and it was found that scan-sampling pitch influenced the accuracy of measurement of the density of the sample. To improve the accuracy of density measurement, sufficient knowledge about characteristic features of the density measuring system is essential.

Selected Impressions on the Beginning of the Electronic Medical Record and Patient Information

To present an overview of early European and American work on Electronic Medical Records and patient information. The invited lectures of "pioneers of electronic patient information" given at the farewell symposium of Wolfgang Giere in Frankfurt, Germany, are summarized and discussed. The origin of medical record writing goes back to Hippocrates and over many centuries this important medical duty was regarded as an annoying, laborious and error-prone task. First steps towards a better medical record started in 1936 with punch cards. In the 1960s the minimum basic data set, a unique patient ID was introduced and even for outpatients first computerized medical record systems were developed applying some important standards and well accepted data structures. Nowadays multimedia are included in patient record systems, highly specialized subsystems e.g. for radiology or cardiology are available, and semantic and statistic mining techniques as well as medical classifications and standardized terminologies support evaluation. All these methods should primarily improve the quality of care, reduce errors, improve communication between multiple specialists, reduce wait times for patients and improve efficiency. Over decades it became obvious that the structure of a medical record notably for coded data but also for narrative text and pictures must be carefully modelled. Well maintained standardized health terminologies and medical classifications are important issues for a user-friendly electronic medical record, which bring benefits for clinicians and patients.