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H MacMahon

Publications and source records attributed to H MacMahon.

At least 73 records · Page 4Linked to original sources
PubMed1990

[Computer-aided diagnosis of interstitial lung diseases].

We are developing an automated method for determination of quantitative physical measures of lung textures in digital chest radiographs in order to detect and characterize interstitial lung disease. We describe a scheme of our approach for lung texture analysis, an automated classification method for distinction between normal and abnormal lungs with interstitial disease, and the effect of digital parameters on the accuracy of this computerized analysis, as well as applications of this method to the ILO pneumoconioses standard radiographs. The root-mean-square (rms) variation and the first moment of the power spectrum of the lung texture were determined as quantitative texture measures based on a frequently analysis of lung textures, which represent the magnitude and coarseness (or fineness) of the lung textures, respectively. The computerized classification method is based on the analysis of these texture measures and on a data base derived from clinical cases. This classification method includes three independent tests, one for a definitely abnormal focal pattern, one for a relatively localized abnormal pattern, and one for a diffuse abnormal pattern. A comparison of receiver operating characteristic (ROC) curves obtained by radiologists and by means of the computerized classification method indicates that the computerized approach may provide performance similar to human observers in distinguishing lungs with mild interstitial disease from normal lungs. By investigating the effect of digital parameters such as pixel size, ROI size and the number of quantization levels on these texture measures obtained from the lung texture analysis and the performance of this computerized method, we attained a useful guide in the design of this computerized scheme. Texture measures obtained from computer analysis of the ILO pneumoconioses standard radiographs corresponded closely with the ILO classification categories for small opacities, though it was necessary for a qualified radiologist to identify representative areas in each ILO radiograph because of the inhomogeneous distribution of texture patterns in these standard radiographs. Our results suggest strongly that this computerized method can be a valuable aid to radiologists in their assessment of interstitial lung diseases.

Humans↗
PubMed1990

Dynamic digital subtraction evaluation of regional pulmonary ventilation with nonradioactive xenon.

A method of evaluating pulmonary ventilation with a 57-cm image intensifier/television (II/TV) digital chest system is reported. With this method, the patient inhales a mixture of xenon and oxygen gases while dynamic imaging of the chest is done. Images of the airways and ventilated portions of the lungs are obtained by subtraction of images acquired before and after the xenon-oxygen mixture is administered. The feasibility of the method was evaluated by studies with xenon-filled tubes, an airway phantom, and a ventilation phantom. The results indicate that tubes larger than 3.2 mm in diameter are detectable at a xenon concentration of 41%, and that gas flow and flow distribution can be examined after image subtraction. If background subtraction is incomplete because of motion, the visibility of small airways is reduced greatly, although unventilated regions can still be delineated. The initial evaluation of this technique included imaging a healthy volunteer during xenon inhalation.

Contrast Media↗
PubMed1990

Improvement in radiologists' detection of clustered microcalcifications on mammograms. The potential of computer-aided diagnosis.

Relatively simple, but important, detection tasks in radiology are nearing accessibility to computer-aided diagnostic (CAD) methods. The authors have studied one such task, the detection of clustered microcalcifications on mammograms, to determine whether CAD can improve radiologists' performance under controlled but generally realistic circumstances. The results of their receiver operating characteristic (ROC) study show that CAD, as implemented by their computer code in its present state of development, does significantly improve radiologists' accuracy in detecting clustered microcalcifications under conditions that simulate the rapid interpretation of screening mammograms. The results suggest also that a reduction in the computer's false-positive rate will further improve radiologists' diagnostic accuracy, although the improvement falls short of statistical significance in this study.

Calcinosis↗
PubMed1990

Computer-aided diagnosis in chest radiology.

Digital radiography offers several important advantages over conventional systems, including abilities for image manipulation, transmission, and storage. In the long term, however, the unique ability to apply artificial intelligence techniques for automated detection and quantitation of disease may have an even greater impact on radiologic practice. Although CAD is still in its infancy, the results of several recent studies clearly indicate a major potential for the future. The concept of using computers to analyze medical images is not new, but recent advances in computer technology together with progress in implementing practical digital radiography systems have stimulated research efforts in this exciting field. Several facets of CAD are presently being developed at the University of Chicago and elsewhere for application in chest radiology as well as in mammography and vascular imaging. To date, investigators have focused on a limited number of subjects that have been, by their nature, particularly suitable for computer analysis. There is no aspect of radiologic diagnosis that could not potentially benefit from this approach, however. The ultimate goal of these endeavors is to provide a system for comprehensive automated image analysis, the results of which could be accepted or modified at the discretion of the radiologist.

Breast Diseases↗
PubMed1990

Pulmonary nodules: computer-aided detection in digital chest images.

Currently, radiologists fail to detect pulmonary nodules in up to 30% of cases with actually positive findings. Diagnoses may be missed due to camouflaging effects of anatomic background, subjective and varying decision criteria, or distractions in clinical situations. We developed a computerized method to detect locations of lung nodules in digital chest images. The method is based on a difference-image approach and feature-extraction techniques, including growth, slope, and profile tests. Computer results were used to alert 12 radiologists to possible nodule locations in 60 clinical cases. Preliminary results suggest that computer aid can improve the detection performance of radiologists.

Adult↗
PubMed1990

Quantitative computer-aided analysis of lung texture in chest radiographs.

The authors describe a computerized method to quantify and characterize interstitial diseases by using physical texture measures obtained from an analysis of the power spectrum of lung textures in digital chest radiographs. They compared these texture measures obtained from standard radiographs from the International Labour Office (ILO) classification scheme and the ILO classification categories for small opacities in pneumoconioses. Their preliminary results indicate that texture measures obtained from this computer analysis of the ILO standard radiographs correspond closely with the ILO classification categories.

Computer Graphics↗
PubMed1990

Potential usefulness of an artificial neural network for differential diagnosis of interstitial lung diseases: pilot study.

An artificial neural network approach was applied to the differential diagnosis of interstitial lung diseases. The neural network was designed to distinguish between nine types of interstitial lung diseases on the basis of 20 items of clinical and radiographic information. A data base for training and testing the neural network was created with 10 hypothetical cases for each of the nine diseases. The performance of the neural network was evaluated by means of receiver operating characteristic analysis. The decision performance of the neural network was high; it was comparable to that of chest radiologists and superior to that of senior radiology residents. The preliminary results strongly suggest that the neural network approach has potential utility in the computer-aided differential diagnosis of interstitial lung diseases.

Computer Simulation↗
PubMed1990

Evaluation of radiographs developed by a new ultrarapid film processing system.

The image quality of radiographs developed by a new ultrarapid processor was evaluated to determine if faster processing causes degradation in the image. The processor used was the Konica Super-Rapid SRX-501 model. Two films designed for this processor (Konica MGH-SR and MGL-SR) were processed in 45 sec and were compared with standard rapid processing in 90 sec of corresponding conventional films (Kodak TMG and OC). Rare-earth screens (Kodak Lanex Regular and Lanex Medium) used with the new and conventional films interleaved during angiographic studies or for phantom images were assessed for image quality. The basic imaging properties of the screen-film systems were examined by measuring (1) Hurter and Driffield curves, (2) modulation transfer functions by using the slit method, and (3) noise Wiener spectra. Subjective clinical assessment showed that the images obtained with ultrarapid processing were acceptable, with increased contrast and graininess. Hurter and Driffield curve measurements confirmed higher gradients. Modulation transfer function measurements were the same as for the conventional films. Noise Wiener spectrum measurements showed a 10% increase in noise for MGH-SR vs TMG film and a 30% increase for MGL-SR vs OC film. We conclude that acceptable image quality can be obtained using ultrarapid processing, with processing time approximately 60% that of conventional rapid processing. Potential applications include all areas in which rapid availability of the radiograph for interpretation is important. Although the processor studied was the first of its kind available, our evaluation indicates that the technology is available for a new class of ultrarapid processors.

Evaluation Studies as Topic↗
PubMed1989

Efficacy of computed tomography of the thorax and upper abdomen and whole-body gallium scintigraphy for staging of lung cancer.

To assess the efficacy of performing both computed tomography (CT) of the thorax and upper abdomen and whole-body gallium scintigraphy for staging lung cancer, the results of each test were compared with those obtained by chest radiography and clinical examination in 100 patients. Clinical efficacy was defined in terms of accuracy in staging the tumor based either on surgery, biopsy, or clinical and radiologic follow-up. The CT provided significantly superior accuracy in 27 patients and minor additional staging information in 17 patients compared with the gallium scan. Whole-body gallium scintigraphy provided important additional information in nine patients and minor additional information in a further eight. The diagnostic yield of CT and gallium scanning was considered equivalent in 39 cases. Of the nine cases in which gallium was significantly superior to CT, clinical findings which suggested the presence of metastases had been noted before the scan in four cases. The authors' results confirm the utility of CT for staging lung cancer and indicate that the additional yield from gallium scintigraphy is relatively low provided a thorough history and physical examination have been performed.

Adult↗
PubMed1989

Occult lung carcinoma presenting with dysphagia. The value of computed tomography.

Dysphagia is a relatively uncommon presenting symptom of lung carcinoma that usually occurs in association with mediastinal adenopathy. However, a bronchogenic carcinoma will occasionally involve the esophagus by direct invasion. These central lesions can be difficult to visualize on chest radiographs and may not be detected by esophagoscopy or barium swallow. In such cases, a computed tomography scan of the thorax may suggest the correct diagnosis.

Adult↗
PubMed1989

Digital imaging of the chest.

During the past several years, image acquisition in nuclear medicine, computed tomography, ultrasonography, subtraction angiography, and magnetic resonance has been by digitization. Despite these advances, research in the development of digital imaging in conventional radiography has lagged behind. Although studies with a variety of digital techniques have been carried out on several fronts, we still do not possess a method that has captured the imagination of the majority of radiologists and other physicians to a point where it could replace conventional screen-film imaging. This article reviews the current status and general principles of the technology, focusing on the four digital radiographic techniques that have shown the greatest promise - film digitization, an image intensifier - based system, photostimulable phosphor plates, and a scanned projection system. The physical aspects of each of the four systems and the clinical results that have been reported to date, as well as the advantages and disadvantages of each system, are presented.

Humans↗
PubMed1989

Pulmonary nodule mimicked by ECG lead artifact.

Recently, a new ECG lead has been introduced that can mimic a pulmonary nodule to the uninitiated. Alternatively, in those institutions where the lead is commonly seen, physicians may dismiss a real finding on the chest x-ray film as a lead "artifact." We describe the appearance of this new chest wall artifact.

Aged↗
PubMed1988

Efficacy of plain abdominal radiography in patients with gastrointestinal bleeding.

To assess the value of plain abdominal radiography in cases of gastrointestinal hemorrhage, the records of 100 such consecutive patients were reviewed. Seventy-eight of the patients had presented to the emergency department, and 22 were inpatients. The radiologic and clinical records were scrutinized to determine the actual effect of the radiologic examination on management of the patient. Three patients had pneumoperitoneum attributed to bowel perforation, and two had confirmed bowel obstruction. In each, the clinical findings suggested the diagnosis. We found no instance of silent gastrointestinal bleeding in which plain radiography contributed important diagnostic information. We conclude that gastrointestinal bleeding is not, in itself, a valid indication for abdominal radiography.

Evaluation Studies as Topic↗
PubMed1988

Digital chest radiography: effect on diagnostic accuracy of hard copy, conventional video, and reversed gray scale video display formats.

Observer performance tests were conducted to compare the effects on diagnostic accuracy of hard copy (film) versus video display and to determine the diagnostic merits of conventional negative ("white bone") versus positive ("black bone") video displays. Subjective preferences were elicited from each observer for each display modality, and diagnostic accuracy was determined with receiver operating characteristic analysis. Digitized chest radiographs were used, including normal and abnormal cases with a variety of subtle abnormalities. The hard copy was printed with a 1,024 X 1,024-matrix by a high-quality drum scanner in conventional white bone format only. The video images were displayed on a 1,023-line monitor (30 Hz, interlaced) in both white bone and black bone formats with fixed window and brightness settings. Most observers preferred hard copy to video, but preferences were sharply divided between white bone and black bone video. Diagnostic accuracy was significantly greater with hard copy than with video display, and the conventional white bone format was significantly superior in accuracy to the black bone display.

Computer Systems↗
PubMed1987

Basic imaging properties of a large image intensifier-TV digital chest radiographic system.

The basic imaging properties of a large (57 cm) image intensifier (I.I.)-TV digital imaging system were examined to determine the effects of various physical parameters on the quality of the digital chest images obtained, and also to explore the clinical usefulness of the system. The characteristic curve of the digital system, which relates the output pixel value to the input relative x-ray intensity, was measured with an aluminum stepwedge. MTFs were determined using slit images, and the veiling-glare fraction was measured with a lead-disk technique. Noise Wiener spectra were obtained from uniformly exposed images. The current limitations of the large II-TV digital chest system are its low spatial resolution, and the presence of large amounts of veiling glare and structure mottle. Advantages of this system over other digital chest imaging systems include the high speed of image data acquisition and the capability of "real-time" dynamic imaging of the chest at a radiation dose comparable to that in conventional radiography of the chest.

Humans↗
PubMed1987

Digital mammography. ROC studies of the effects of pixel size and unsharp-mask filtering on the detection of subtle microcalcifications.

We investigated the spatial resolution requirement and the effect of unsharp-mask filtering on the detectability of subtle microcalcifications in digital mammography. Digital images were obtained by digitizing conventional screen-film mammograms with a 0.1 X 0.1 mm2 pixel size, processed with unsharp masking, and then reconstituted on film with a Fuji image processing/simulation system (Fuji Photo Film Co., Tokyo, Japan). Twenty normal cases and 12 cases with subtle microcalcifications were included. Observer performance experiments were conducted to assess the detectability of subtle microcalcifications in the conventional, the unprocessed digital, and the unsharp-masked mammograms. The observer response data were evaluated using receiver operating characteristic (ROC) and LROC (ROC with localization) analyses. Our results indicate that digital mammograms obtained with 0.1 X 0.1 mm2 pixels provide lower detectability than the conventional screen-film mammograms. The detectability of microcalcifications in the digital mammograms is improved by unsharp-mask filtering; the processed mammograms still provide lower accuracy than the conventional mammograms, however, chiefly because of increased false-positive detection rates for the processed images at each subjective confidence level. Viewing unprocessed digital and unsharp-masked images in pairs resulted in approximately the same detectability as that obtained with the unsharp-masked images alone. However, this result may be influenced by the fact that the same limited viewing time was necessarily divided between the two images.

Breast Neoplasms↗