Development and clinical implementation of an enhanced display algorithm for use in networked electronic portal imaging.

PURPOSE: To introduce and clinically validate a preprocessing algorithm that allows clinical images from an electronic portal imaging device (EPID) to be displayed on any computer monitor, without loss of clinical usability. The introduction of such a system frees EPI systems from the constraints of fixed viewing workstations and increases mobility of the images in a department. METHODS AND MATERIALS: The preprocessing algorithm, together with its variable parameters is introduced. Clinically, the algorithm is tested using an observer study of 316 EPID images of the pelvic region in the framework of treatment of carcinoma of the cervix and endometrium. Both anterior-posterior (AP/PA) and latero-lateral (LAT) images were used. The images scored were taken from six different patients, five of whom were obese, female, and postmenopausal. The result is tentatively compared with results from other groups. The scoring system, based on the number of visible landmarks in the port, is proposed and validated. Validation was performed by having the observer panel score images with artificially induced noise levels. A comparative study was undertaken with a standard automatic window and leveling display technique. Finally, some case studies using different image sites and EPI detectors are presented. RESULTS: The image quality for all images in this study was deemed to be clinically useful (mean score >1). Most of the images received a score which was second highest (AP/PA landmarks > or =6 and LAT landmarks > or =5). Obesity, which has been an important factor determining the image quality, was not seen to be a factor here. Compared to standard techniques a highly significant improvement was determined with regard to clinical usefulness. The algorithm performs fast (less than 9 seconds) and needs no additional user interaction in most of the cases. The algorithm works well on both direct detection portal imagers and camera-based imagers whether analog or digital cameras. CONCLUSIONS: We have demonstrated that it is possible to preprocess EPIs in such a way that the clinically relevant landmarks are easily detected on a generic computer screen. The algorithm is system-independent and fast. This allows for the encoding of EPIs in more generalized commercial formats so that distribution of images is facilitated.

Clinical results of computerized tomography-based simulation with laser patient marking.

PURPOSE: Accuracy of a patient treatment portal marking device and computerized tomography (CT) simulation have been clinically tested. METHODS AND MATERIALS: A CT-based simulator has been assembled based on a commercial CT scanner. This includes visualization software and a computer-controlled laser drawing device. This laser drawing device is used to transfer the setup, central axis, and/or radiation portals from the CT simulator to the patient for appropriate patient skin marking. A protocol for clinical testing is reported. Twenty-five prospectively, sequentially accessioned patients have been analyzed. RESULTS: The simulation process can be completed in an average time of 62 min. Under many cases, the treatment portals can be designed and the patient marked in one session. Mechanical accuracy of the system was found to be within +/- 1mm. The portal projection accuracy in clinical cases is observed to be better than +/- 1.2 mm. Operating costs are equivalent to the conventional simulation process it replaces. CONCLUSION: Computed tomography simulation is a clinical accurate substitute for conventional simulation when used with an appropriate patient marking system and digitally reconstructed radiographs. Personnel time spent in CT simulation is equivalent to time in conventional simulation.

CT-based simulation with laser patient marking.

A CT-based simulator has been assembled based on a commercial CT scanner, virtual simulation software developed at the University of North Carolina and a laser drawing device to transfer the radiation portals from the virtual simulator to the patient. The simulation process can be completed in approximately 1 h; under most cases, the treatment portals can be designed and the patient marked in one session. The device has an inherent accuracy of +/- 1 mm. The portal projection accuracy in clinical cases is observed to be better than 2 mm.

Correction for distortion in a beam outline transfer device in radiotherapy CT-based simulation.

In using a CT scanner as a radiation therapy simulator, it would be helpful to be able to transfer the beam outline from the computer plan to the patient's skin. A beam outline transfer device has been constructed and installed on a Siemens' DRH CT scanner gantry. The planned treatment beam geometry from a 3-D computerized simulation and planning system can be projected onto the patient's skin surface accurately and efficiently. The positioning accuracy achieved is within +/- 0.1 cm over a 20 cm x 20 cm field. Integrating the device into the CT scanner, simplifies the device and reduces the cost over an externally mounted device. Two unsuccessful methods to correct the projection distortions are also mentioned. In order to achieve the reported beam outline transfer accuracy, a system based on our empirically derived calibration procedure is described.

Radiotherapy departmental automation.

Cost-effective radiotherapy departmental information systems have been developed to answer a growing need for facility management and clinical research. These systems provide scheduling and management support to improve patient flow, facility utilization, charge capture, quality assurance and clinical studies. Typical data base definition, system utilization and costs are presented.

Data management and radiotherapy.

The realization by radiation therapists that computerized patient information is a valuable resource is slowly evolving. The uses of this data include business, quality control, and research applications. Computer applications in these areas have been limited due to the small numbers of patients and the complexity of radiation therapy problems. Reductions in costs and improved programming techniques over the last decade have made information processing computer systems feasible. Measureable progress has been made in the areas of billing and scheduling systems, improved department data handling systems, and increased participation in cooperative groups with increased data handling capability. A review of costs in terms of dollars, time, and effort supports the use of information processing systems in therapy.

Efficacy of CT-assisted two dimensional treatment planning: analysis of 45 patients.

A method is presented for quantitatively assessing the impact of CT assistance in treatment planning for radiation therapy. A three-phased analysis of treatment plans for 45 patients was undertaken. Nonuniformity and local efficiency of dose delivered were compared without and with the utilization of CT information. Good agreement between the objective assessment of treatment plans and independent subjective optimization of the plans by a radiotherapist support the validity of this technique. On the basis of nonuniformity of dose, 31 of the 45 cases were planned more poorly in the absence of CT information. The addition of CT information permitted optimization by the physician in 25 of the 45 patients. Twenty-three of these showed improved local efficiency (92%). This study indicates that measurable improvements in treatment plans are available by taking advantage of CT information. These were greatest in the brain, lung, and retroperitoneum in this small group of patients.