Biomedical subjects

J M Michalski

Publications and source records attributed to J M Michalski.

28 records · Page 2Linked to original sources

PubMed1995

Adjuvant radiation therapy for rectal carcinoma: predictors of outcome.

PURPOSE: To review predictors of outcome, including sequencing of modalities and pretreatment findings for adjuvantly treated rectal cancer. METHODS AND MATERIALS: From 1975 through 1990, 307 patients with adenocarcinoma of the rectum underwent adjuvant radiation therapy. In 251 cases the radiation therapy was administered preoperatively, either 40-50 Gy (median dose 45 Gy) followed in 6-7 weeks by surgery (210 cases), or 20 Gy in five fractions immediately prior to surgery (41 cases). In 56 cases, patients were referred postoperatively for radiation (median dose 50 Gy). Adjuvant chemotherapy was never given concurrently with the preoperative radiation (RT), although 43 of the cases (including 14 of the preoperative RT cases) received postoperative chemotherapy. RESULTS: Multivariate analysis (Cox model) indicated that significant predictors of better overall freedom from disease were preoperative rather than postoperative RT (p < 0.001), low surgical stage (p < 0.0001), specialist surgeon (p = 0.007), low or moderate histologic grade (p = 0.026), and proximal lesion (p = 0.033). The significant predictors for better local control included use of preoperative RT (p < 0.001), low or moderate grade (p = 0.001), and low surgical stage (p = 0.015). The 5-year local control and freedom from disease for the preoperative RT patients were 90% +/- 2% and 73% +/- 3%, respectively. The selected cases that received the short course of 20 Gy preoperatively did well. Although 24 out of 41 patients proved to have Astler Coller B2 or C disease, local control at last follow-up was 39 out of 41 (95%). A second multivariate analysis of pretreatment factors was performed on the preoperative RT cases. The significant factors for both local control and overall freedom from disease were noncircumferential vs. circumferential tumor, proximal vs. distal lesion, and background of the surgeon. Additional negative factors on univariate analysis (although not achieving independent significance on multivariate analysis) included the finding of near-obstructing lesions and elevated carcinoembryonic antigen (CEA). Grade > or = 3 sequelae occurred in 8% of cases (including 3% bowel obstruction). The only significant factor for complications was background of the surgeon (4% for colorectal specialists vs. 12% for nonspecialists, p = 0.015). CONCLUSIONS: Significant factors for better tumor control included preoperative as opposed to postoperative RT and the experience of the surgeon. In selected cases, excellent results can be obtained with a short course of preoperative radiation. Concurrent chemotherapy need not be given routinely with preoperative radiation. Subgroups of preoperative RT cases at risk for distant metastases (who might benefit from postoperative chemotherapy), and at high risk for local failure (for whom concurrent preoperative chemotherapy and radiation might be considered), are identified.

Adenocarcinoma↗

PubMed1995

The Electronic View Box: a software tool for radiation therapy treatment verification.

PURPOSE: We have developed a software tool for interactively verifying treatment plan implementation. The Electronic View Box (EVB) tool copies the paradigm of current practice but does so electronically. A portal image (online portal image or digitized port film) is displayed side by side with a prescription image (digitized simulator film or digitally reconstructed radiograph). The user can measure distances between features in prescription and portal images and "write" on the display, either to approve the image or to indicate required corrective actions. The EVB tool also provides several features not available in conventional verification practice using a light box. METHODS AND MATERIALS: The EVB tool has been written in ANSI C using the X window system. The tool makes use of the Virtual Machine Platform and Foundation Library specifications of the NCI-sponsored Radiation Therapy Planning Tools Collaborative Working Group for portability into an arbitrary treatment planning system that conforms to these specifications. The present EVB tool is based on an earlier Verification Image Review tool, but with a substantial redesign of the user interface. A graphical user interface prototyping system was used in iteratively refining the tool layout to allow rapid modifications of the interface in response to user comments. RESULTS: Features of the EVB tool include 1) hierarchical selection of digital portal images based on physician name, patient name, and field identifier; 2) side-by-side presentation of prescription and portal images at equal magnification and orientation, and with independent grayscale controls; 3) "trace" facility for outlining anatomical structures; 4) "ruler" facility for measuring distances; 5) zoomed display of corresponding regions in both images; 6) image contrast enhancement; and 7) communication of portal image evaluation results (approval, block modification, repeat image acquisition, etc.). CONCLUSION: The EVB tool facilitates the rapid comparison of prescription and portal images and permits electronic communication of corrections in port shape and positioning.

Hospital Records↗

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

Is weekly port filming adequate for verifying patient position in modern radiation therapy?

PURPOSE: The objective of this study is to use daily electronic portal imaging to evaluate weekly port filming in detecting patient set-up position. METHODS AND MATERIALS: A computer-based portal alignment method was used to quantify the field displacements on 191 digitized weekly port films and 848 daily electronic portal images in 21 radiation therapy patients. An electronic portal image data set as a control for actual daily treatment position was used to evaluate weekly port films with respect to same-day field displacement, rate of field placement error detection, and prediction of subsequent daily field displacements. RESULTS: The field displacements measured on a port film frequently deviated from the corresponding field displacements on the electronic portal image obtained in the same treatment set-up. A linear regression analysis showed that the curves fitted to the same-day field displacements had slopes that differed significantly from unity (p < 0.001). Overall, the respective frequencies of field placement error, beyond clinical tolerance limits of 5, 7, and 10 mm (corresponding to head and neck, thoracic, and pelvic sites) for port filming and electronic portal imaging were 11% and 14% (p = 0.4) in the X-direction (lateral or anteroposterior) and 24% and 13% (p = .0001) in the Y-direction (caphalad-caudad). When the data were broken down by anatomical region, this discrepancy was found to be mainly due to the differences in the thorax, and head and neck image data sets. For thoracic fields, error in Y-shifts was 28% by port filming, but only 9% by portal imaging (p = 0.01). In the head and neck region, 18% of the port films exceeded tolerance, whereas only 6% of the electronic portal images did (p = 0.0001). Field displacements on the treatment set-ups between the acquisition of port films were not predicted by those films. CONCLUSION: There are discrepancies between the field displacements and field placement errors detected by weekly port films and daily electronic portal images. This study suggests that improved methods of treatment verification may be necessary in modern radiation therapy.

Diagnostic Imaging↗

PubMed1993

An evaluation of two methods of anatomical alignment of radiotherapy portal images.

PURPOSE: Two techniques have been developed at our institution to allow anatomical registration of digitized portal images to a simulation film. Accuracy of the portal image alignment methods is tested and single intrauser and multiple interuser variation is examined using each technique. METHODS AND MATERIALS: Method one requires the identification of anatomical fiducial points on a simulation image and its corresponding portal image. The parameters required to align the corresponding points are calculated by a least squares fit algorithm. Method two uses an anatomical template generated from the simulation image and superimposing it upon a portal image. The template is then adjusted by a computer mouse to obtain the best subjective anatomical fit on the portal image. Megavoltage portal images of a skull phantom with various known shifts and eight clinical image files were aligned by each method. Each data set was aligned several times by both a single user and multiple users. RESULTS: Alignment of the anatomical phantom portal images demonstrates an accuracy of less than 0.8 +/- 0.9 mm and 0.7 +/- 1.0 degrees with either method. As out of plane rotation increased from 0 to 5 degrees, simulating out of plane malpositioning, alignment orthogonal to the plane of rotation worsened to 1.5 +/- 1.1 mm with the point method and 2.4 +/- 1.6 mm with the template method. Alignment parallel to the axis of the gantry rotation was insensitive to this change and remained constant as did the rotational alignment parameters. For the clinical image files the magnitude of variation for a single user is typically less than +/- 1 mm or +/- 1 degree. The magnitude of variation of alignment increased when multiple users aligned the same image files. The variation was dependent upon anatomical site and to a lesser degree the method of alignment used. The root mean square deviation of translational shifts range from +/- 0.68 mm when using the template method in the pelvis to as high as +/- 2.94 mm with the template method to align abdominal portal images. In the thorax and pelvis translational alignments along the horizontal axis were more precise than along the vertical axis. Multiple user variability was in part due to poor image quality, user experience, non rigidity of the anatomical features, and the difficulty in locating an exact point on a continuous anatomical structure. CONCLUSION: In well controlled phantom studies both the fiducial point and template method provide similar and adequate results. The phantom studies show that alignment error and variance increase with distortion in anatomical features secondary to out of plane rotations. In clinical situations intrauser variation is small, however, multiple interuser variation is larger. The magnitude of variation is dependent upon the anatomical site aligned.

Computer Simulation↗

PubMed1993

The use of on-line image verification to estimate the variation in radiation therapy dose delivery.

PURPOSE: On-line radiotherapy imaging systems provide data that allow us to study the geometric nature of treatment variation. It is more clinically relevant to examine the resultant dosimetric variation. In this work, daily beam position as recorded by the on-line images is used to recalculate the treatment plan to show the effect geometric variation has on dose. METHODS AND MATERIALS: Daily 6 MV or 18 MV x-ray portal images were acquired using a fiberoptic on-line imaging system for 12 patients with cancers in the head and neck, thoracic, and pelvic regions. Each daily on-line portal image was aligned with the prescription simulation image using a template of anatomical structures defined on the latter. The outline of the actual block position was then superimposed on the prescription image. Daily block positions were cumulated to give a summary image represented by the block overlap isofrequency distribution. The summary data were used to analyze the amount of genometric variation relative to the prescription boundary on a histogram distribution plot. Treatment plans were recalculated by considering each aligned portal image as an individual beam. RESULTS: On-Line Image Verification (OLIV) data can differentiate between systematic and random errors in a course of daily radiation therapy. The data emphasize that the type and magnitude of patient set-up errors are unique for individual patients and different clinical situations. Head and neck sites had the least random variation (average 0-100% block overlap isofrequency distribution width = 7 mm) compared to thoracic (average 0-100% block overlap isofrequency distribution width = 12 mm) or pelvic sites (average 0-100% block overlap isofrequency distribution width = 14 mm). When treatment delivery is analyzed case by case, systematic as well as random errors are represented. When the data are pooled by anatomical site, individuality of variations is lost and variation appears random. Recalculated plans demonstrated dosimetric deviations from the original plans. The differences between the two dosimetric distributions were emphasized using a technique of plan subtraction. This allowed quick identification of relative "hot and cold spots" in the recalculated plans. The magnitude and clinical significance of dosimetric variation was unique for each patient. CONCLUSIONS: OLIV data are used to study geometric uncertainties because of the unique nature for individual patients. Dose recalculation is helpful to illustrate the dosimetric consequences of set-up errors.

Humans↗

PubMed1993

On-line image verification in radiation therapy: an early USA experience.

The intense effort in the past 5 to 10 years to develop on-line image verification (OLIV) systems is made partly in anticipation of the increased verification demands of complex 3-dimensional (3D) conformal radiation therapy, and partly to improve on the current practice of weekly treatment verification. These systems allow convenient acquisition of daily portal images or many images during one treatment session. Systems based on fluoroscopic and scanning approaches can now be purchased from various vendors and are being evaluated at several radiation therapy centers. The performances of these systems vary, but all appear to be adequate for clinical use. At the Mallinckrodt Institute of Radiology, we have been conducting clinical on-line imaging for the past 3 years using a fiber-optic fluoroscopic system. Daily operation of the system requires coordinated participation of the physics and radiation therapy technology staff. The major consideration is in the management and evaluation of the large amount of verification images about each individual patient. At present, it is not clear whether the technology would be cost-effective in the clinical setting. However, it is clear that OLIV provides a powerful tool in enhancing our knowledge of treatment variation. The information will be invaluable in the development of improved treatment techniques. It is also likely that these systems will play a important part in the verification of 3D conformal radiation therapy.

Calibration↗

PubMed1990

Primary central nervous system lymphoma: analysis of prognostic variables and patterns of treatment failure.

The authors retrospectively analyzed the data on 36 patients with primary central nervous system (CNS) lymphoma. Most patients received radiation therapy to the whole brain with or without a boost. Chemotherapy was administered to six patients (18%) as part of their initial therapy. The 1- and 2- year rates of progression-free survival were 46% and 27%. The following factors had a favorable impact on survival: age of 60 years or less, normal or mildly impaired preirradiation neurologic function, and confinement of the tumor to the cerebral hemispheres or cerebellum. Chemotherapy as part of initial therapy appears to improve local control. Increasing radiation doses delayed local failure. Failure occurred in the brain (88%), in the eye (23%), and systemically (8%). There were no neuraxis failures identified. The authors conclude that primary CNS lymphoma is a locally aggressive disease that is poorly controlled with conventional radiation therapy. Investigation for more effective therapy is ongoing.

Aged↗

PubMedDate not supplied

Innovations in three-dimensional treatment planning and quality assurance.

Radiation therapy treatment planning and treatment delivery are in the process of changing dramatically over the next several years. This change has been driven in large part by continued advances in computer hardware and software and in medical imaging. Three-dimensional radiation treatment planning systems are rapidly being implemented in clinics around the world. These developments in turn have prompted manufacturers to employ advanced microcircuitry and computer technology to produce treatment delivery systems capable of precise shaping of dose distributions via computer-controlled multileaf collimators which cause the beam intensity to be varied across the beam. Image-based 3D planning and beam intensity modulated delivery systems show significant potential for improving the quality of radiotherapy and improving the efficiency with which radiation therapy can be planned and delivered. However, significant research and development work on these systems and their clinical use remains to be performed. The techniques used for the treatment planning and the methods used for quality assurance procedures and testing must all be revised and/or redesigned to allow efficient clinical use of these technological advances. Although much of the current 3D radiation therapy process requires interactive tasks (and some still very laborious) the path is clear toward solving the technological obstacles so that a nearly automated planning, delivery, and verification system will become a reality over the next decade. Such systems will allow radiation oncologists to significantly increase dose to many tumor sites while concomitantly lowering doses to critical organs-at-risk. Most of the tasks will be automated, thus lowering the overall costs currently needed to provide high-quality external beam radiation therapy.

Humans↗

PubMedDate not supplied

New trends in prostatic cancer research. Three-dimensional conformal radiation therapy (3-D CRT), brachytherapy, and new therapeutic modalities.

In prostatic cancer research three-dimensional conformal radiation therapy (3-D CRT), brachytherapy and new therapeutic modalities have been applied. Treatment planning and delivery of radiation therapy have substantially evolved in the past 20 years. The treatment of localized carcinoma of the prostate with 3-D CRT is described, preliminary clinical results are presented and compared with those with standard radiation therapy (SRT). The benefit of 3-D CRT hypothetically could be linked to improved local tumor control because of a better coverage of the target volume with a specific dose of irradiation, less acute and late toxicity, possibility of carrying out dose-escalation studies. Intensity modulated radiation therapy (IMRT) may be particularly useful in some cases. Further efforts are necessary with collaboration of urologists and radiation oncologists to continue to explore approaches to optimally select and manage patients with localized prostate cancer. A reliable assessment of the impact of 3-D CRT and IMRT on outcome should come from prospective randomized long-term studies. As for brachytherapy, standardized protocols should be developed to objectively evaluate brachytherapy in localized prostatic cancer. Recently a great deal of interest has been focused on new therapeutic modalities with chemotherapeutic agents, a new agent named prostate specific enhancer, a regulatory element of the PSA gene is being tested. Laboratory and animal studies of the viral construct have been reported. A phase I human clinical trial is being initiated in the U.S.A. in patients with postirradiation hormone refractory prostate cancer.

Brachytherapy↗