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Biomedical subjects

M Carlin

Publications and source records attributed to M Carlin.

15 recordsLinked to original sources
PubMed2001

Tumor size on computed tomography scans: is one measurement enough?

BACKGROUND: Bidimensional tumor measurements are used routinely as surrogates for tumor volume. The purpose this study was to determine whether there is any added benefit in bidimensional or tridimensional measurements over a unidimensional measurement. METHODS: Sixty-nine colorectal hepatic metastases on 19 computed tomography scans (1-8 lesions per scan) from 9 patients were analyzed. Five patients contributed 2-4 scans each (mean, 3 scans). The standard volume of these lesions was determined by the "summation of areas" technique. The maximum axial dimension, the product of the greatest axial dimensions, and several volume estimates (based on the volumes of a sphere, an ellipsoid, and a cube) each were correlated with the standard volume. RESULTS: The maximum axial dimension and the product of the greatest axial dimensions correlated equally with tumor volume (correlation coefficient = 0.93). Surrogate measures based on the equations for a sphere and an ellipsoid underestimated tumor volume, whereas the equation for a cube overestimated volume. CONCLUSIONS: When reporting tumor size, there is no significant added benefit in reporting bidimensional or tridimensional measurements over the maximum axial dimension.

Data Interpretation, Statistical↗
PubMed1996

Paraspinal muscle hematoma after electromyography.

There have been few reports of complications related to electromyography. Needle examination of certain muscles is sometimes avoided in patients taking anticoagulant agents, although no clear guidelines have been established. We describe a patient who was not receiving an anticoagulant and developed a large paraspinal muscle hematoma after routine electromyography. Subsequently, all patients who underwent paraspinal muscle electromyography and were diagnosed with radiculopathy at our institution over a 14-month period were reviewed. From this group, 17 patients were identified who had also underwent MRI of the appropriate spinal levels within 1 week after the needle examination. These images were reviewed for evidence of paraspinal muscle hematomas. Four small hematomas were identified in four different patients. None of these were radiologically significant compared with the large hematoma described in the case report. Radiologically apparent paraspinal hematomas after electromyography are an unusual complication of needle examination and do not appear to have any clinical significance. Nevertheless, the presence of these lesions justifies caution when considering electromyography of paraspinal and other deeper muscles in anticoagulated patients.

Adult↗
PubMed1995

Perturbation of target-directed neurite outgrowth in embryonic CNS co-cultures grown in the presence of ethanol.

Studies were conducted to determine the influence of ethanol on target-directed fiber outgrowth in culture, using embryonic chick spinal cord-muscle, and fetal rat septal-hippocampal co-cultured explants. Process extension from the spinal cord and septal explants in control cultures was selectively oriented toward the appropriate target tissue. Ethanol in the culture medium (500 mg/dl) eliminated this target-oriented outgrowth in both systems, although the overall extent of neurite outgrowth was not affected. In an effort to further characterize the source of this disruption, target explants were grown alone, with and without ethanol, and the target-conditioned culture media was subsequently harvested and placed on newly plated spinal cord or septal explants, to determine whether ethanol decreased the target production of soluble substances. To determine whether deposition of substrate-bound materials by the target tissue was affected by ethanol, spinal cord or septal explants were plated in wells which had previously been occupied by the appropriate target tissue. These studies revealed that ethanol significantly inhibited production of soluble and substrate-bound materials by muscle explants, but not by hippocampal explants. It was concluded that the ethanol-induced loss of target-directed neurite outgrowth in the spinal cord explants could be accounted for primarily by the attenuated production of neurotropic/neurotropic substances by the muscle tissue. The loss of target-directionality in the septal explants appeared to be due to other factors, possibly related to ethanol-induced compromise of the capacity of the septal neurons to respond appropriately to target-derived neurotrophic/neurotropic substances. The implications of these results for the fetal alcohol syndrome are considered.

Animals↗
PubMed1994

Development of a digital duplication system for portable chest radiographs.

To provide high-quality duplicate chest images for the intensive care units, we have developed a digital duplication system in which film digitization is performed in conjunction with nonlinear density correction, contrast adjustment, and unsharp mask filtering. This system provides consistent image densities over a wide exposure range and enhancement of structures in the mediastinum and upper abdominal areas, improving visibility of catheters and tubes. The image quality is often superior to that of the original radiograph and is more consistent from day to day. Repeat rates for portable chest radiographs have been reduced by more than a factor of two since implementation of digitization in December 1991, and the number of repeat examinations caused by exposure errors have been substantially reduced.

Computer Systems↗
PubMed1994

Incongruous item generation effects: a multiple-cue perspective.

In a series of studies, generation effects were obtained under encoding conditions designed to induce incongruous, unrelated item generation. Experiments 1 and 2, using free- and cued-recall measures, respectively, provided evidence that this unrelated generation effect was due to response-specific processing. Experiment 3 demonstrated a lack of relation between free recall and indices of clustering. A preliminary protocol study suggested that Ss generate multiple items in their search for appropriate unrelated responses. In Experiments 4 and 5, conditions designed to produce more extensive multiple generations demonstrated enhanced free recall. These results supported a multiple-cue account of facilitated recall for incongruous item generation. The multiple-cue perspective is consistent with traditional conceptualizations of memory, such as the principle of congruity, and contemporary distinctions between cue-target relational and item-specific processing.

Adult↗
PubMed1994

Evaluation of an asymmetric screen-film system for chest radiography.

To evaluate the potential utility of an asymmetric screen-film system for chest radiography, its image quality and detail visibility compared with a conventional screen-film system are investigated. The basic imaging properties were evaluated by measuring Hurter and Driffield curves, resolution properties, and noise Wiener spectra. The visibility of simulated anatomical and pathological details in radiographs of a chest phantom and normal anatomy in chest radiographs of patients were evaluated subjectively. The dynamic range of each system is comparable, though the asymmetric screen-film system can provide an advantage over the conventional system due to a relative dose reduction of approximately 35% and higher resolution properties at high optical densities. The noise level of the asymmetric screen-film system is slightly greater at low optical densities and much greater at high optical densities. However, the visibility of lung details with the asymmetric screen-film system is slightly superior to the conventional screen-film system despite the increase in noise. Mediastinal and retrodiaphragmatic details are similar, though marginally superior with the asymmetric screen-film system. It is concluded that the asymmetric screen-film system provided slightly superior image quality to the conventional screen-film system for chest radiography, provided the average lung density is maintained at a higher level than is customary with conventional systems.

Biophysical Phenomena↗
PubMed1993

Clinical experience with an advanced laser digitizer for cost-effective digital radiography.

Film digitization has not been widely pursued in clinical settings mainly because of perceived limitations involving film latitude and image quality. However, a high-quality laser digitizer can be combined with wide-latitude film and specially developed digital processing techniques to achieve image quality comparable or superior to that of storage phosphor computed radiography (SPR) over a wide range of exposure. This film digitization system provides the operational advantages of digital radiography, such as consistent image density, high-quality inexpensive duplicates, and digital storage and retrieval capability. The reliability and monetary costs of the system also compare favorably with those of SPR. In the long term, technologies that employ reusable plates and do not require chemical processing to produce diagnostic images may well replace screen-film systems. Presently, however, film digitization remains a practical and cost-effective approach to digital radiography.

Cost-Benefit Analysis↗
PubMed1992

Laser alignment system for high-quality portable radiography.

In portable radiography, image quality is degraded by scattered radiation. Use of an accurately aligned, antiscatter grid can provide consistently high image quality, but the necessary precision for grid alignment is difficult to achieve with conventional techniques. The authors developed a simple laser alignment method for bedside radiography. A compact laser device is mounted on the collimator housing of a mobile radiography machine, so that the laser beam is precisely parallel to the central x-ray beam. A small reflector device, which attaches to the edge of the grid cassette, indicates beam centering and alignment in a clear, intuitive way. In clinical use, the laser alignment technique provided uniformly high image quality, equivalent to that of fixed equipment. The system has the advantages of being simple to use and inexpensive to implement with existing equipment.

Adult↗
PubMed1991

Direct comparison of conventional and computed radiography with a dual-image recording technique.

To compare the image quality of computed radiographic (CR) with conventional screen-film images, the authors used a dual-image recording technique. Images were simultaneously acquired with a conventional screen-film combination and a storage-phosphor imaging plate loaded into a single cassette. Wiener spectra and modulation transfer function were compared for both image types. A preliminary observer performance test was conducted with chest images obtained with the dual-image recording technique on portable and fixed equipment. Analysis of physical parameters and observer test results suggests that the conventional screen-film system can provide slightly superior image quality, although the CR system has some advantage in bedside applications.

Confidence Intervals↗
PubMed1983

Physical and clinical evaluation of new high-strip-density radiographic grids.

The imaging performance of new high-strip-density (HSD) grids having 57 lines/cm was compared with that of conventional low-strip-density (LSD) grids having 33 or 40 lines/cm. The unique advantage of HSD grids is that, under most standard radiographic conditions, the grid lines are not noticeable on the final image, even if the grid is stationary. This is due to the combined effect of the high fundamental spatial frequency of HSD grids, the modulation transfer function of screen-film systems and of the human visual system, and scattered radiation. Monte Carlo simulation studies, phantom images, and clinical evaluation indicate that HSD grids can provide contrast improvement factors and Bucky factors that are comparable to or slightly better than those obtained with LSD grids. Therefore, it may now be possible to eliminate moving Bucky trays from radiographic tables and fluoroscopic devices.

Bone and Bones↗
PubMedDate not supplied

Comparison of fixed and adjustable window width and level settings in the CT evaluation of diffuse lung disease.

OBJECTIVE: The purpose of this investigation was to assess the utility of allowing free adjustment of window width and level in comparison with the use of a fixed lung window in the CT evaluation of diffuse lung disease. MATERIALS AND METHODS: Six radiologists each judged 36 cases (28 diffuse lung disease and 8 normal) using a standardized form. In half of the sessions, images were viewed in a fixed lung window (level = -500 HU; width = 2,000 HU). In the other sessions, the observer was able to adjust the window and level freely while viewing the images. Each case was seen twice in separate sessions: once in a fixed lung window and once with window width and level adjusted by the reader. A variety of diagnostic features were evaluated using a 5 point scale. These included visibility of fine lung structures, abnormalities of the lung parenchyma, and overall evaluation of the lung. RESULTS: The visibility of lung structures was not improved with adjustable window settings. Receiver operating characteristic (ROC) analysis showed fixed windows to be superior to adjustable windows for overall evaluation of the cases [fixed A(z) = 0.90, adjustable A(z) = 0.84, p < 0.05, jackknife method]. Time to rate each case was increased by 15% with window width and level adjustment. CONCLUSION: Free adjustment of window width and level produced no improvement in reader performance over that achieved with fixed window width and level.

Humans↗
PubMedDate not supplied

Prometheus unbound.

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Facility Design and Construction↗