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At least 235 records · Page 13Linked to original sources
PubMed2004

Accuracy of diagnostic tests read with and without clinical information: a systematic review.

CONTEXT: Although it is common practice to read tests with clinical information, whether this improves or decreases the accuracy of test reading is uncertain. OBJECTIVE: To determine whether diagnostic tests are more accurate when read with clinical information or without it. DATA SOURCES: MEDLINE search (1966-December 2003) extended by search of reference lists and articles citing the articles retrieved (Web of Science, 1985-December 2003). STUDY SELECTION: All articles comparing the accuracy of tests read twice by the same readers, once without and once with clinical information, but otherwise under identical conditions. Only articles that reported sensitivity and specificity or receiver operating characteristic (ROC) curves were included. DATA EXTRACTION: Data were extracted by one author and reviewed independently by the other. When the data were difficult to interpret, differences were resolved by discussion. DATA SYNTHESIS: Sixteen articles met the inclusion criteria. Eleven articles compared areas under ROC curves for tests read with and without clinical information, and 5 compared only sensitivity and specificity. Ten articles used actual clinical information; 6 used constructed clinical information that was plausible. Overall, clinical information improved test reading accuracy although the effect was smaller in the articles using actual clinical information when compared with those using constructed clinical information. There were no instances in which clinical information resulted in significant reduction in test reading accuracy. In some instances, improved test reading accuracy came from improved sensitivity without loss of specificity. CONCLUSIONS: At least for the tests examined, the common practice of reading diagnostic tests with clinical information seems justified. Future studies should be designed to investigate the best way of providing clinical information. These studies should also give an estimate of the accuracy of clinical information used, display ROC curves with identified data points, and include a wider range of diagnostic tests.

Diagnostic Techniques and Procedures↗
PubMed1999

Effect of localization devices and registration methods on the accuracy of stereotactic frame systems predicted by the Gaussian approach.

A qualitative work-flow analysis of a neurosurgical procedure indicates that the resolution of the image used to plan the intervention is the major source of inaccuracy. Quantitative experimental measurements confirm this observation. They fail, however, to explain the relationship between the accuracy of the frame components involved in a stereotactic procedure and the overall application accuracy. This investigation shows that the novel Gaussian approach is a flexible framework for the calculation of the application accuracy of frame systems. Therefore, the Gaussian approach provides a detailed understanding of the interplay between the various factors affecting accuracy. The basic ideas and limitations of the Gaussian approach are briefly explained. The effect of fiducial marker distribution and registration is investigated and shown to introduce a spatial dependence to the accuracy. The results of the Gaussian approach are compared with experimental data for three stereotactic frame devices: Leksell G, Cosman-Roberts-Wells, and Brown-Roberts-Wells. Although the Gaussian approach is an approximation, it reproduces the accuracy measured in the experiment within the statistical error of that experiment.

Algorithms↗
PubMed1996

Pulse oximetry: accuracy of methods of interpreting graphic summaries.

Although pulse oximetry has been used to determine the frequency and extent of hemoglobin desaturation during sleep, movement artifact can result in overestimation of desaturation unless valid desaturations can be identified accurately. Therefore, we determined the accuracy of pulmonologists' and technicians' interpretations of graphic displays of desaturation events, derived an objective method for interpreting such events, and validated the method on an independent data set. Eighty-seven randomly selected desaturation events were classified as valid (58) or artifactual (29) based on cardiorespiratory recordings (gold standard) that included pulse waveform and respiratory inductive plethysmography signals. Using oximetry recordings (test method), nine pediatric pulmonologists and three respiratory technicians ("readers") averaged 50 +/- 11% (SD) accuracy for event classification. A single variable, the pulse amplitude modulation range (PAMR) prior to desaturation, performed better in discriminating valid from artifactual events with 76% accuracy (P < 0.05). Following a seminar on oximetry and the use of the PAMR method, the readers' accuracy increased to 73 +/- 2%. In an independent set of 73 apparent desaturation events (74% valid, 26% artifactual), the PAMR method of assessing oximetry graphs yielded 82% accuracy; transcutaneous oxygen tension records confirmed a drop in oxygenation during 49 of 54 (89%) valid desaturation events. In conclusion, the most accurate method (91%) of assessing desaturation events requires recording of the pulse and respiratory waveforms. However, a practical, easy-to-use method of interpreting pulse oximetry recordings achieved 76-82% accuracy, which constitutes a significant improvement from previous subjective interpretations.

Adolescent↗
PubMed2002

Accuracy evaluation of a 3D ultrasound-based neuronavigation system.

We have investigated the 3D navigation accuracy of a frameless ultrasound-based neuronavigation system (SonoWand) for surgical planning and intraoperative image guidance. In addition, we present a detailed description and review of the error sources associated with surgical neuronavigation based on preoperative MRI data and intraoperative ultrasound. A phantom with 27 precisely defined points was scanned with ultrasound by various translation and tilt movements of the ultrasound probe (180 3D scans in total), and the 27 image points in each volume were located using an automatic detection algorithm. These locations were compared to the physically measured locations of the same 27 points. The accuracy of the neuronavigation system and the effect of varying acquisition conditions were found through a thorough statistical analysis of the differences between the two point sets. The accuracy was found to be 1.40 +/- 0.45 mm (arithmetic mean) for the ultrasound-based neuronavigation system in our laboratory setting. Improper probe calibration was the major contributor to this figure. Based on our extensive data set and thorough evaluation, the accuracy found in the laboratory setting is expected to be close to the overall clinical accuracy for ultrasound-based neuronavigation. Our analysis indicates that the overall clinical accuracy may be as low as 2 mm when using intraoperative imaging to compensate for brain shift.

Humans↗
PubMed2004

Small sample estimation of relative accuracy for binary screening tests.

Comparing the accuracy of two screening tests is ideally achieved by administering both tests as well as a gold standard test to all study subjects. In practice, a more ethical screen positive study design is often used, one that requires gold standard determination only for subjects that screen positive on either test under investigation. Although it is not possible to quantify the absolute accuracy of each test with such a design,the relative accuracy of the tests can be estimated. Since relative accuracy estimation has poor small sample properties, adjusted estimators based on adding constants to the observed data have been proposed. The adjusted estimators have the advantage that they yield point and variance estimates of relative accuracy in all settings. However, we show through both theory and numerical examples that adding constants to the data can be beneficial or detrimental to small sample performance. Furthermore, the performance of the adjusted estimator depends not only on the magnitude of the constant but also on parameters that cannot be estimated with data from a screen positive study, making selection of an optimal constant difficult in practice. We also examine the performance of the adjusted estimator using data from a study comparing the accuracy of two screening tests for cervical cancer.

Adult↗
PubMed2004

Accuracy of absence of fetal breathing movements in predicting preterm birth: a systematic review.

OBJECTIVE: To determine the accuracy with which the absence of fetal breathing movements on ultrasound examination predicts spontaneous preterm birth in women with threatened preterm labor. METHODS: Data sources included Medline, Embase, Pascal, Biosis, Cochrane Library, Medion, National Research Register, SciSearch, conference papers, and manual searching of bibliographies of known primary and review articles. A study was selected if it used absence of fetal breathing movements on ultrasound to predict spontaneous preterm birth in women with threatened preterm labor but before advanced cervical dilatation. Two reviewers independently selected studies and extracted data on their characteristics, quality and accuracy. Accuracy data were used to form 2 x 2 contingency tables with birth within 48 h and within 7 days of testing as the reference standards. Likelihood ratios for a positive test (LR+) and negative test (LR-) were calculated as a measure of accuracy. RESULTS: There were eight studies, which included a total of 328 women, evaluating the accuracy of absence of fetal breathing movements in predicting spontaneous preterm birth in women with threatened preterm labor. There were differences in the methodological quality among the included studies. All were lacking in one or more item that make up an ideal test accuracy study. For women presenting with threatened preterm labor, meta-analysis showed a summary LR+ of 14.80 (95% CI, 6.30-34.79) with a corresponding summary LR- of 0.46 (95% CI, 0.36-0.58) for predicting preterm birth within 7 days, and summary LR+ of 7.84 (95% CI, 1.12-54.99) and summary LR- of 0.25 (95% CI, 0.13-0.48) for predicting preterm birth within 48 h of testing. CONCLUSION: Absence of fetal breathing movements has the potential to be a useful test in predicting preterm birth both within 7 days and within 48 h of testing. However, the available studies were deficient in their sample size and quality of methodology. Future research should be undertaken to evaluate this technology and to address the methodological deficiencies.

Female↗
PubMed1993

Prediction of protein secondary structure at better than 70% accuracy.

We have trained a two-layered feed-forward neural network on a non-redundant data base of 130 protein chains to predict the secondary structure of water-soluble proteins. A new key aspect is the use of evolutionary information in the form of multiple sequence alignments that are used as input in place of single sequences. The inclusion of protein family information in this form increases the prediction accuracy by six to eight percentage points. A combination of three levels of networks results in an overall three-state accuracy of 70.8% for globular proteins (sustained performance). If four membrane protein chains are included in the evaluation, the overall accuracy drops to 70.2%. The prediction is well balanced between alpha-helix, beta-strand and loop: 65% of the observed strand residues are predicted correctly. The accuracy in predicting the content of three secondary structure types is comparable to that of circular dichroism spectroscopy. The performance accuracy is verified by a sevenfold cross-validation test, and an additional test on 26 recently solved proteins. Of particular practical importance is the definition of a position-specific reliability index. For half of the residues predicted with a high level of reliability the overall accuracy increases to better than 82%. A further strength of the method is the more realistic prediction of segment length. The protein family prediction method is available for testing by academic researchers via an electronic mail server.

Mathematical Computing↗
PubMed1994

Accuracy of pregnancy/non pregnancy diagnosis in zebu and crossbred cattle and Murrah buffaloes by milk progesterone determination post insemination.

Milk samples collected on days 0, 6, 20, 22 and 24 post insemination from Sahiwal and Tharparkar (zebu) cows, Karan Swiss (Sahiwal x Brown Swiss) and Karan Fries (Tharparkar x Holstein Friesian) crossbred cows and Murrah buffaloes were analysed for progesterone by enzyme-linked immunosorbent assay to determine the accuracy of pregnancy and non pregnancy diagnosis in each of the 3 groups of animals. The accuracy of pregnancy diagnosis was markedly improved in cows when the milk progesterone values on days 20, 22 and 24 were considered together, and a further improvement when the levels on days 0, 6, 20, 22 and 24 were considered together particularly in crossbred cows. In contrast, buffaloes exhibited the highest degree of accuracy from samples collected on day 24, and improvement in accuracy was minimal when values were considered for all 5 days, viz. 0, 6, 20, 22 and 24 post insemination. Overall, the accuracy of positive pregnancy diagnosis was greatest in zebu cows (90.9%) followed by crossbred cows (86.6%) and Murrah buffaloes (76.5%) when milk progesterone values on all 5 days were considered. The accuracy for negative pregnancy diagnosis was 100% on all days. The results suggest that there is a greater variability in oestrous cycle length in cattle than in buffaloes, and embryonic mortality is greater in buffaloes than in cattle.

Animals↗
PubMed2004

Constraints on the spatiotemporal accuracy of interceptive action: effects of target size on hitting a moving target.

Results of two experiments are reported that examined how people respond to rectangular targets of different sizes in simple hitting tasks. If a target moves in a straight line and a person is constrained to move along a linear track oriented perpendicular to the target's motion, then the length of the target along its direction of motion constrains the temporal accuracy and precision required to make the interception. The dimensions of the target perpendicular to its direction of motion place no constraints on performance in such a task. In contrast, if the person is not constrained to move along a straight track, the target's dimensions may constrain the spatial as well as the temporal accuracy and precision. The experiments reported here examined how people responded to targets of different vertical extent (height): the task was to strike targets that moved along a straight, horizontal path. In experiment 1 participants were constrained to move along a horizontal linear track to strike targets and so target height did not constrain performance. Target height, length and speed were co-varied. Movement time (MT) was unaffected by target height but was systematically affected by length (briefer movements to smaller targets) and speed (briefer movements to faster targets). Peak movement speed (Vmax) was influenced by all three independent variables: participants struck shorter, narrower and faster targets harder. In experiment 2, participants were constrained to move in a vertical plane normal to the target's direction of motion. In this task target height constrains the spatial accuracy required to contact the target. Three groups of eight participants struck targets of different height but of constant length and speed, hence constant temporal accuracy demand (different for each group, one group struck stationary targets = no temporal accuracy demand). On average, participants showed little or no systematic response to changes in spatial accuracy demand on any dependent measure (MT, Vmax, spatial variable error). The results are interpreted in relation to previous results on movements aimed at stationary targets in the absence of visual feedback.

Adult↗
PubMed2000

Endoscopic ultrasonography in the preoperative staging of gastric cancer: accuracy and impact on surgical therapy.

BACKGROUND: Endoscopic ultrasonography (EUS) is a standard procedure in the preoperative staging of patients with gastric carcinomas. Herein we present our experience with EUS and discuss the results and their implications for surgical therapy. METHODS: A total of 116 patients with histologically confirmed gastric adenocarcinoma were referred to EUS and classified prospectively by the TNM system. The results of the preoperative endosonographic staging were compared with the definitive histopathological results after the operation. RESULTS: The overall accuracy of EUS for determination of the T stage was 78%. The accuracy for the T1 and T2 stages was 80% and 63%, respectively. With 20% and 30%, there was a relatively high rate of overstaging in these cases. The accuracy for T3 and T4 tumors was 95% and 83%, respectively. The accuracy of EUS for determination of the N stage was 77%, with a sensitivity of 91% and a specificity of 84%. Resectability was predicted correctly with a sensitivity of 94% and a specificity of 83%. CONCLUSIONS: Generally accepted standards for the therapy of advanced gastric carcinomas do not exist. In cases where the therapeutic strategy is surgical exploration, no preoperative staging is necessary. In cases with differentiated treatment strategies, the accuracy of EUS is not sufficient for the selection of patients for endoscopic resection. Its accuracy for submucosal cancer invasion and for the detection of lymph node metastases needs to be further enhanced. If only multimodal therapy is considered, EUS staging seems to be absolutely mandatory. Patients classified preoperatively as T1 to T3 can be operated on primarily with sufficient security. In patients where radical resection of the tumor seems doubtful, we recommend that a diagnostic laparoscopy be performed to confirm the diagnosis.

Adult↗
PubMed2002

Accuracy of endorectal ultrasonography in preoperative staging of rectal tumors.

PURPOSE: Preoperative staging of rectal tumors is considered essential to tailor treatment for individual patients. The aim of the present study was to evaluate the accuracy of endorectal ultrasonography in preoperative staging of rectal tumors. METHODS: Eleven hundred eighty-four patients with rectal adenocarcinoma or villous adenoma underwent endorectal ultrasonography evaluation at a single institution during a ten-year period. We compared the endorectal ultrasonography staging with the pathology findings based on the surgical specimens in 545 patients who had surgery (307 by transanal excision, 238 by radical proctectomy) without adjuvant preoperative chemoradiation. Comparisons between groups were performed using chi-squared tests and logistic regression analysis. RESULTS: Overall accuracy in assessing the level of rectal wall invasion was 69 percent, with 18 percent of the tumors overstaged and 13 percent understaged. Accuracy depended on the tumor stage and on the ultrasonographer. Overall accuracy in assessing nodal involvement in the 238 patients treated with radical surgery was 64 percent, with 25 percent overstaged and 11 percent understaged. CONCLUSION: The accuracy of endorectal ultrasonography in assessing the depth of tumor invasion, particularly for early cancers, is lower than previously reported. The technique is more precise in distinguishing between benign tumors and invasive cancers and between tumors localized to the rectal wall and tumors with transmural invasion. Differences in image interpretation may in part explain discrepancies in accuracy between studies.

Adenocarcinoma↗
PubMed2005

Estimating and comparing diagnostic tests' accuracy when the gold standard is not binary.

RATIONALE AND OBJECTIVES: Investigators often need to assess the accuracies of diagnostic tests when the gold standard is not binary-scale. The objective of this article is to describe nonparametric estimators of diagnostic test accuracy when the gold standard is continuous, ordinal, and nominal scale. MATERIALS AND METHODS: A nonparametric method of estimating and comparing the area under receiver operating characteristic (ROC) curves, proposed by DeLong et al, is extended to situations in which the gold standard is not binary. Two examples illustrate the methods. RESULTS: Measures of diagnostic test accuracy, their variance, and tests for comparing two diagnostic tests' accuracies in paired designs are presented for situations in which the gold standard is continuous, ordinal, and nominal scale. These summary measures of diagnostic test accuracy are analogous in form and interpretation to the area under the ROC curve. CONCLUSION: Dichotomizing the outcomes of a gold standard so that traditional ROC methods can be applied can lead to bias. The methods described here are useful for assessing and comparing summary test accuracy when the gold standard is not binary scale. They have limitations similar to other summary indices.

Diagnostic Imaging↗
PubMed2005

Accuracy of endoscopic optical coherence tomography in the detection of dysplasia in Barrett's esophagus: a prospective, double-blinded study.

BACKGROUND: Endoscopic optical coherence tomography (EOCT) is a high-resolution, cross-sectional tissue-imaging technique that provides microscopic morphologic information. EOCT should detect dysplasia in Barrett's epithelium, but this has not been established in a prospective blinded study. This study evaluated the accuracy of EOCT for the diagnosis and the exclusion of dysplasia in patients with Barrett's esophagus. METHODS: A 2.4-mm diameter EOCT probe was modified for use with a cap-fitted, two-channel endoscope. Pairs of EOCT image streams and jumbo biopsy specimens were obtained. Endoscopy/EOCT procedures were performed by 4 endoscopists who separately reviewed the EOCT digital images for the absence or the presence of dysplasia (low grade, high grade, or cancer) for each biopsy specimen obtained. The endoscopists were blinded to the interpretation of the pathology. An experienced pathologist blinded to the endoscopic/EOCT findings evaluated each biopsy for the absence or the presence of dysplasia. The setting of the study was a major academic medical center. Adult patients with documented Barrett's esophagus greater than 2 cm were included in the study. The main outcome measurement was the accuracy of EOCT in the detection of dysplasia in patients with Barrett's esophagus. RESULTS: A total of 314 usable EOCT image stream/biopsy pairs were obtained in 33 patients. By using histology as the standard, the performance of EOCT was sensitivity, 68%; specificity, 82%; positive predictive value, 53%; negative predictive value, 89%; and diagnostic accuracy, 78%. Diagnostic accuracy for the 4 endoscopists ranged from 56% to 98%. Limitations of the study were the variability in endoscopists' accuracy rates, difficulty in real-time interpretation, and the need for refined criteria of dysplasia by EOCT imaging. CONCLUSIONS: The current EOCT system has an accuracy of 78% for the detection of dysplasia in patients with Barrett's esophagus. EOCT could be used to target biopsies to areas of Barrett's epithelium with a higher probability for the presence of dysplasia. However, further modifications, including increased resolution and identification of further potential OCT characteristics of dysplasia, are needed before EOCT can be used clinically.

Adult↗
PubMed2006

Geometric accuracy of a real-time target tracking system with dynamic multileaf collimator tracking system.

PURPOSE: Dynamically compensating for target motion during radiotherapy will increase treatment accuracy. A laboratory system for real-time target tracking with a dynamic MLC has been developed. In this study, the geometric accuracy limits of this DMLC target tracking system were evaluated. METHODS AND MATERIALS: A motion simulator was programmed to follow patient-derived tumor motion paths, parallel to the leaf motion direction. A target attached to the simulator was optically tracked, and the leaf positions adjusted to continually align the DMLC beam aperture to the target. Analysis of the tracking accuracy was based on video images of the target and beam alignment. The system response time was determined and the tracking error measured. Response time-corrected tracking accuracy was also calculated to investigate the accuracy limits of an improved system. RESULTS: The response time of the system is 160 +/- 2 ms. The geometric precision for tracking patient motion is 0.6 to 1.1 mm (1 sigma) for the 3 patient datasets tested, with tracking errors relative to the original patient motion of 35, 40, and 100%. CONCLUSIONS: A DMLC target tracking system has been developed that can account for detected motion parallel to the leaf motion direction. The tracking error has a negligible systematic component. Reducing the response time will further increase the overall system accuracy.

Calibration↗
PubMed2006

Repositioning accuracy of two different mask systems-3D revisited: comparison using true 3D/3D matching with cone-beam CT.

PURPOSE: The repositioning accuracy of mask-based fixation systems has been assessed with two-dimensional/two-dimensional or two-dimensional/three-dimensional (3D) matching. We analyzed the accuracy of commercially available head mask systems, using true 3D/3D matching, with X-ray volume imaging and cone-beam CT. METHODS AND MATERIALS: Twenty-one patients receiving radiotherapy (intracranial/head-and-neck tumors) were evaluated (14 patients with rigid and 7 with thermoplastic masks). X-ray volume imaging was analyzed online and offline separately for the skull and neck regions. Translation/rotation errors of the target isocenter were analyzed. Four patients were treated to neck sites. For these patients, repositioning was aided by additional body tattoos. A separate analysis of the setup error on the basis of the registration of the cervical vertebra was performed. The residual error after correction and intrafractional motility were calculated. RESULTS: The mean length of the displacement vector for rigid masks was 0.312 +/- 0.152 cm (intracranial) and 0.586 +/- 0.294 cm (neck). For the thermoplastic masks, the value was 0.472 +/- 0.174 cm (intracranial) and 0.726 +/- 0.445 cm (neck). Rigid masks with body tattoos had a displacement vector length in the neck region of 0.35 +/- 0.197 cm. The intracranial residual error and intrafractional motility after X-ray volume imaging correction for rigid masks was 0.188 +/- 0.074 cm, and was 0.134 +/- 0.14 cm for thermoplastic masks. CONCLUSIONS: The results of our study have demonstrated that rigid masks have a high intracranial repositioning accuracy per se. Given the small residual error and intrafractional movement, thermoplastic masks may also be used for high-precision treatments when combined with cone-beam CT. The neck region repositioning accuracy was worse than the intracranial accuracy in both cases. However, body tattoos and image guidance improved the accuracy. Finally, the combination of both mask systems with 3D image guidance has the potential to replace therapy simulation and intracranial stereotaxy.

Algorithms↗
PubMed2006

Accuracy of spatial normalization of the hippocampus: implications for fMRI research in memory disorders.

Functional magnetic resonance imaging (fMRI) studies in memory impairment have detected functional alterations in medial temporal lobe (MTL) structures, notably the hippocampus. Many of these studies employ spatial normalization to place subjects in a standardized template space prior to analysis; however, little is known about the effects of local atrophy on the normalization process in structures such as the hippocampus. The purpose of this study was to compare the accuracy of spatial normalization of the hippocampus between memory-impaired patients and controls. Twenty clinically-defined mild cognitive impairment (MCI) subjects and twenty elderly controls were studied at 4T with structural and functional MRI during a memory encoding-retrieval task. Bilateral hippocampal regions-of-interest (ROIs) were manually drawn for all subjects and further divided into anterior/posterior subregions. To assess normalization accuracy to the Montreal Neurological Institute template, the percentage of each template-defined hippocampal ROI originating from true hippocampal tissue was determined for all subjects. To assess the ability of spatial normalization to equalize group differences in hippocampal volume, pre- and post-normalization hippocampal volumes were compared. Finally, fMRI measures from template and non-template analyses were compared. Poorer normalization accuracy of the bilateral hippocampi, particularly the posterior portions, was found for MCI subjects. Significant group differences were found in left hippocampal and bilateral posterior hippocampal volumes, and these differences were not corrected with normalization. Hippocampal volumes were significantly correlated with normalization accuracy across MCI and control groups, but some significant differences in normalization accuracy persisted independent of these volume differences. Template and non-template fMRI analyses were significantly correlated in controls, but not MCI subjects, during memory retrieval. These findings suggest decreased normalization accuracy in memory-impaired subjects is a potentially important confounder of template-based fMRI analyses in the hippocampus and MTL.

Adult↗
PubMed2006

Accuracy of stress Tc-99m tetrofosmin myocardial perfusion tomography for the diagnosis and localization of coronary artery disease in women.

BACKGROUND: Earlier studies have suggested a modest accuracy of stress thallium 201 myocardial perfusion imaging (MPI) for the diagnosis of coronary artery disease (CAD) in women. The accuracy of stress MPI with technetium 99m tetrofosmin has not been studied in women. The aim of this study was to assess the accuracy of stress Tc-99m tetrofosmin MPI for the diagnosis and localization of CAD in women. METHODS AND RESULTS: We studied 88 women who underwent exercise or dobutamine stress Tc-99m tetrofosmin tomography and coronary angiography within 3 months. Significant CAD was defined as a stenosis 50% or greater in diameter in at least 1 major epicardial coronary artery. Myocardial perfusion abnormalities were detected in 44 of 53 patients with significant CAD and in 7 of 35 patients without significant CAD (overall sensitivity, 83% [95% confidence interval (CI), 73%-93%]; specificity, 80% [95% CI, 67%-93%]; and accuracy, 82% [95% CI, 74%-90%]). The sensitivity was 72% (18/25) in patients with single-vessel CAD and 93% (26/28) in patients with multivessel CAD. Perfusion abnormalities were detected in 2 or more vascular distributions in 20 of 28 patients with multivessel CAD and in 4 of 60 patients without multivessel CAD (sensitivity for the identification of multivessel CAD, 71% [95% CI, 55%-88%]; specificity, 93% [95% CI, 86%-98%]; and accuracy, 86% [95% CI, 79%-93%]). The sensitivity, specificity, and accuracy were 82%, 84%, and 83%, respectively, for the diagnosis of CAD in the left anterior descending artery; 77%, 84%, and 81%, respectively, for CAD in the right coronary artery; and 74%, 80%, and 78%, respectively, for CAD in the left circumflex artery. CONCLUSION: Stress Tc-99m tetrofosmin MPI is an accurate noninvasive technique for the diagnosis and localization of CAD in women.

Aged↗
PubMed2004

Repositioning accuracy of a commercially available thermoplastic mask system.

BACKGROUND AND PURPOSE: To evaluate the repositioning accuracy of a commercially available thermoplastic mask system for single dose radiosurgery treatments and fractionated treatment courses. PATIENTS AND METHODS: The repositioning accuracy of the Raycast-HP mask system (Orfit Industries, Wijnegem, Belgium) was analyzed. Twenty-two patients that were treated by intensity-modulated radiation therapy (IMRT) or intensity modulated radiosurgery (IMRS) for 43 intracranial lesions, underwent repeated CT imaging during their course of treatment, or as a positional control immediately before radiosurgery. We evaluated multiple anatomical landmark coordinates and their respective shifts in consecutive repeated CT-controls. An iterative optimization algorithm allowed for the calculation of the x, y and z-components of translation of the target isocenter(s) for each repeated CT, as well as rotation in the respective CT data sets. In addition to absolute target isocenter translation, the total magnitude vector (i.e. sum-vector) of isocenter motion was calculated along with patient rotations about the three principle axes. RESULTS: Fifty-five control CT datasets were analyzed for the target isocenter's respective position relative to the original treatment planning CT simulation. Mean target isocenter translation was 0.74+/-0.53, 0.75+/-0.60 and 0.93+/-0.78 mm in x, y and z-directions, respectively. Mean rotation about the x, y and z-axes was 0.67+/-0.66, 0.61+/-0.63 and 0.67+/-0.61 degrees, respectively. The respective median and mean magnitude vectors of isocenter translation were 1.28 and 1.59+/-0.84 mm. Analysis of the accuracy of the first setup control, representative of setup accuracy for radiosurgery treatments, compared with setup accuracy throughout a fractionated radiation treatment course were statistically equivalent (P= 0.15) thus indicating no measurable deterioration of setup accuracy throughout the treatment course. CONCLUSIONS: The analyzed Orfit thermoplastic mask system performed favorably compared with other mask immobilization systems for which peer-reviewed repositioning data exist. While the performance of the system for fractionated treatment courses was considered to be excellent, use of this mask system for radiosurgery immobilization in our clinic is subject to additional quality assurance measures to prohibit the delivery of treatments with target dislocations larger than 2 mm. The measured data in the present study should enable the users of this system to assign appropriate margins for the generation of planning target volumes.

Cranial Irradiation↗