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W Harms

Publications and source records attributed to W Harms.

33 records · Page 2Linked to original sources
PubMed1995

The cumulative verification image analysis tool for offline evaluation of portal images.

PURPOSE: Daily portal images acquired using electronic portal imaging devices contain important information about the setup variation of the individual patient. The data can be used to evaluate the treatment and to derive correction for the individual patient. The large volume of images also require software tools for efficient analysis. This article describes the approach of cumulative verification image analysis (CVIA) specifically designed as an offline tool to extract quantitative information from daily portal images. METHODS AND MATERIALS: The user interface, image and graphics display, and algorithms of the CVIA tool have been implemented in ANSCI C using the X Window graphics standards. The tool consists of three major components: (a) definition of treatment geometry and anatomical information; (b) registration of portal images with a reference image to determine setup variation; and (c) quantitative analysis of all setup variation measurements. The CVIA tool is not automated. User interaction is required and preferred. Successful alignment of anatomies on portal images at present remains mostly dependent on clinical judgment. Predefined templates of block shapes and anatomies are used for image registration to enhance efficiency, taking advantage of the fact that much of the tool's operation is repeated in the analysis of daily portal images. RESULTS: The CVIA tool is portable and has been implemented on workstations with different operating systems. Analysis of 20 sequential daily portal images can be completed in less than 1 h. The temporal information is used to characterize setup variation in terms of its systematic, random and time-dependent components. The cumulative information is used to derive block overlap isofrequency distributions (BOIDs), which quantify the effective coverage of the prescribed treatment area throughout the course of treatment. Finally, a set of software utilities is available to facilitate feedback of the information for treatment plan recalculation and to test various decision strategies for treatment adjustment. CONCLUSIONS: The CVIA tool provides comprehensive analysis of daily images acquired with electronic portal imaging devices. Its offline approach allows characterization of the nature of setup variation for the individual patient that would have been difficult to deduce using only a few daily or weekly portal images. Distribution of the tool will help establish an important database of setup variation from many clinics. The information derived from CVIA can also serve as the foundation to integrate treatment verification, treatment planning, and treatment delivery.

Computer Peripherals↗
PubMed1995

Three-dimensional treatment planning and conformal radiation therapy: preliminary evaluation.

Preliminary clinical results are presented for 209 patients with cancer who had treatment planned on our three-dimensional radiation treatment planning (3-D RTP) system and were treated with external beam conformal radiation therapy. Average times (min) for CT volumetric simulation were: 74 without or 84 with contrast material; 36 for contouring of tumor/target volume and 44 for normal anatomy; 78 for treatment planning; 53 for plan evaluation/optimization; and 58 for verification simulation. Average time of daily treatment sessions with 3-D conformal therapy or standard techniques was comparable for brain, head and neck, thoracic, and hepatobiliary tumors (11.8-14 min and 11.5-12.1, respectively). For prostate cancer patients treated with 3-D conformal technique and Cerrobend blocks, mean treatment time was 19 min; with multileaf collimation it was 14 min and with bilateral arc rotation, 9.8 min. Acute toxicity was comparable to or lower than with standard techniques. Sophisticated 3-D RTP and conformal irradiation can be performed in a significant number of patients at a reasonable cost. Further efforts, including dose-escalation studies, are necessary to develop more versatile and efficient 3-D RTP systems and to enhance the cost benefit of this technology in treatment of patients with cancer.

Bile Duct Neoplasms↗
PubMed1994

Design of a fully integrated three-dimensional computed tomography simulator and preliminary clinical evaluation.

PURPOSE: We describe the conceptual structure and process of a fully integrated three-dimensional (3-D) computed tomography (CT) simulator and present a preliminary clinical and financial evaluation of our current system. METHODS AND MATERIALS: This is a preliminary report on 117 patients treated with external beam radiation therapy alone on whom a 3-D simulation and treatment plan and delivery were carried out from July 1, 1992, through June 30, 1993. The elements of a fully integrated 3-D CT simulator were identified: (a) volumetric definition of tumor volume and patient anatomy obtained with a CT scanner, (b) virtual simulation for beam setup and digitally reconstructed radiographs, (c) 3-D treatment planning for volumetric dose computation and plan evaluation, (d) patient-marking device to outline portal on patient's skin, and (e) verification (physical) simulation to verify portal placement on the patient. Actual time-motion (time and effort) recording was made by each professional involved in the various steps of the 3-D simulation and treatment planning on computer-compatible forms. Data were correlated with the anatomic site of the primary tumor being planned. Cost accounting of revenues and operation of the CT simulator and the 3-D planning was carried out, and projected costs per examination, depending on case load, were generated. RESULTS: Average time for CT volumetric simulation was 74 min without or 84 min with contrast material. Average times were 36 min for contouring of tumor/target volume and 44 min for normal anatomy, 78 min for treatment planning, 53 min for plan evaluation/optimization, and 58 min for verification simulation. There were significant variations in time and effort according to the specific anatomic location of the tumor. Portal marking of patient on the CT simulator was not consistently satisfactory, and this procedure was usually carried out on the physical simulator. Based on actual budgetary information, the cost of a volumetric CT simulation (separate from the 3-D treatment planning) showed that 1500 examinations per year (six per day in 250 working days) must be performed to make the operation of the device cost effective. The same financial projections for the entire 3-D planning process and verification yielded five plans per day. Some features were identified that will improve the use of the 3-D simulator, and solutions are offered to incorporate them in existing devices. CONCLUSIONS: Commercially available CT simulators lack some elements that we believe are critical in a fully integrated 3-D CT simulator. Sophisticated 3-D simulation and treatment planning can be carried out in a significant number of patients at a reasonable cost. Time and effort and therefore cost vary according to the anatomic site of the tumor being planned and the number of procedures performed. Further efforts are necessary, with collaboration of radiation oncologists, physicists, and manufacturers, to develop more versatile and efficient 3-D CT simulators, and additional clinical experience is required to make this technology cost effective in standard radiation therapy of patients with cancer.

Adult↗
PubMed1994

Portable software tools for 3D radiation therapy planning.

PURPOSE: Produce a collection of software tools (computer programs) that support three-dimensional (3D) radiation therapy planning. The tools are not a complete 3D planning system. Instead, they work with any 3D planning system that meets certain minimal specifications. The tools assist in deriving anatomic data from images, generating target volume contours, evaluating treatment plans, and verifying accurate treatment delivery. The tools are portable: they can run without source code changes in any computing environment that provides a library of functions and data definitions called the Foundation. The Foundation couples the portable tools to the (usually nonportable) file system and dose calculation associated with a particular 3D planning system. METHODS AND MATERIALS: Tools were written at three different (geographically separated) institutions. Software developers from all three sites specified the Foundation. The programmers' interface to the Foundation is portable, but a Foundation implementation need not be portable. Each group implemented a Foundation adapted to the (different) 3D planning system used at their site. RESULTS: All tools run at all three sites without source code changes. Each Foundation was implemented in a few person-months of programming effort. The program text and documentation for the tools have been placed in the public domain. CONCLUSIONS: It is practical and economical to produce portable radiotherapy treatment planning tools. Providers of 3D planning programs should offer Foundations for their systems, so they can be used with tools. Researchers considering new computer programs should write them as tools, so they can work with any 3D planning system.

Costs and Cost Analysis↗
PubMed1991

Dose-volume histograms.

A plot of a cumulative dose-volume frequency distribution, commonly known as a dose-volume histogram (DVH), graphically summarizes the simulated radiation distribution within a volume of interest of a patient which would result from a proposed radiation treatment plan. DVHs show promise as tools for comparing rival treatment plans for a specific patient by clearly presenting the uniformity of dose in the target volume and any hot spots in adjacent normal organs or tissues. However, because of the loss of positional information in the volume(s) under consideration, it should not be the sole criterion for plan evaluation. DVHs can also be used as input data to estimate tumor control probability (TCP) and normal tissue complication probability (NTCP). The sensitivity of TCP and NTCP calculations to small changes in the DVH shape points to the need for an accurate method for computing DVHs. We present a discussion of the methodology for generating and plotting the DVHs, some caveats, limitations on their use and the general experience of four hospitals using DVHs.

Humans↗
PubMed1991

Three-dimensional photon treatment planning in carcinoma of the larynx.

The role of three-dimensional (3-D) treatment planning in the definitive treatment of carcinoma of the larynx with radiation was evaluated at four institutions as part of an NCI contract. A total of 30 different treatment approaches were devised for two patients with larynx cancer. CT scans were obtained for both patients and various treatment planning tools were employed to optimize beam arrangements and to evaluate the resulting dose distribution. The effect on dose distribution of a number of factors was also examined: 1) the use of dose calculation algorithms which correct for tissue inhomogeneities, 2) the variation of the CT numbers used for inhomogeneity corrections to simulate inaccuracies in the knowledge of the CT numbers, and 3) the modification of beam energy. A multitude of data was used in plan evaluation and a numerical score was given to each plan to estimate the tumor control probability and the normal tissue complication probability. We found 3-D treatment planning to be of potential value in optimizing treatment plans in larynx cancer. Improved target coverage was achieved when complete information describing 3-D geometry of the anatomy was utilized. In some cases, the treatment planning tools employed, such as the beam's eye view, helped devise novel beam arrangements which were useful alternatives to standard techniques. We found little effect of change in CT number on dose distributions. A comparison between dose distributions calculated with tissue inhomogeneity corrections to those calculated without this correction showed little difference. We did find some improvement in the dose to the primary tumor volume at lower beam energies, but with an increased larynx volume potentially receiving doses above tolerance.

Adult↗
PubMed1986

[Not Available].

Explore the source record for details and available documents.

History, Early Modern 1451-1600↗
PubMed1979

[Local therapy of ulcers].

The allergic contact dermatitis caused by iatrogenic sensibilisation represents one of the major problems involved in the local therapy of skin diseases due to chronic venous insufficiency. Among other forms of treatment it is suggested to use a local therapy without potential allergens in combination with compression therapy.

Administration, Topical↗
PubMedDate not supplied

Contemporary role of modern brachytherapy techniques in the management of malignant thoracic tumors.

Sole brachytherapy for carcinoma of the lung is most often performed using high-dose-rate (HDR) remote afterloading equipment, which delivers the treatment within the tracheobronchial tree in an outpatient setting. It provides excellent, rapid palliation in advanced stages, and can also be used selectively for curative intent in early stages. In better-performance patients, fractionated external beam radiation therapy (EBRT) is preferred to brachytherapy as an initial treatment because it appears to provide a modest gain in survival, and more sustained palliation. In patients with centrally located tumors and limited extent of disease, the combination of external and endoluminal irradiation enables curative treatment options. Intraoperative brachytherapy may complement standard adjuvant treatment in incompletely resected, unresectable, or medically inoperable patients, and has the potential to improve local control in selected cases. Due to the rarity of the disease, the role of endoluminal brachytherapy in the treatment regimen of tracheal neoplasms is not yet clearly defined. The risk of fatal bleeding after endoluminal brachytherapy appears to be correlated with tumor localization and fraction size, but in the majority of cases fatal bleeds are caused by progression of local disease. The use of a distanceable applicator provides a central positioning of the source, prevents the delivery of high-contact doses to the mucosa, and may reduce toxicity. The standard technique for interstitial brachytherapy after breast-conserving surgery and adjuvant EBRT is the use of low-dose-rate (LDR) brachytherapy, but it may also be applied by means of pulsed-dose-rate (PDR) or HDR techniques. Prospective trials comparing different boost techniques and indications are needed to define more precisely the subgroup of patients who are most suitable for interstitial brachytherapy. Reirradiation of chest wall local recurrences using brachytherapy molds is effective and provides a high local control rate with acceptable toxicity.

Brachytherapy↗