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Biomedical subjects

H MacMahon

Publications and source records attributed to H MacMahon.

12 recordsLinked to original sources
PubMed1992

Computerized scheme for the detection of pulmonary nodules. A nonlinear filtering technique.

To aid radiologists in the detection of lung cancer, the authors are developing a computer-aided diagnosis system that locates areas suspicious for nodules in digital chest radiographs. The system involves a difference-image approach and various feature-extraction techniques. The authors describe nonlinear filters used in the difference-image approach. A morphological open operation and a ring-shaped median filter are applied in the difference-image step for signal enhancement and signal suppression, respectively. Using 60 clinical chest radiographs, the nonlinear filtering method detected approximately 63% of actual nodules with approximately 19 false-positive results per image. The locations of the false-positive detections, however, usually did not coincide with those from the linear filtering method. Thus, by using a combination of the detections from the two methods, the false-positive rate was reduced to two to three per image at a sensitivity of 60%.

Evaluation Studies as Topic↗
PubMed1992

Image feature analysis of false-positive diagnoses produced by automated detection of lung nodules.

RATIONALE AND OBJECTIVES: To reduce the number of false-negative diagnoses by radiologists, the authors are developing a computer-aided diagnosis scheme for detection of lung nodules in digital chest images. In this study, the authors attempted to reduce the number of false-positive diagnoses obtained with a previous computer scheme by incorporating additional knowledge from experienced chest radiologists into the computer scheme. METHODS: The authors applied their previous computer scheme, using less-strict criteria, to 60 clinical chest radiographs; this yielded 735 candidate nodules (23 true nodules and 712 false-positive diagnoses). These candidates were analyzed using region-growing, trend-correction, and edge-gradient techniques to determine measures by which to quantify image features of candidate nodules. RESULTS: The 712 false-positive diagnoses represented various anatomic structures that were located throughout the chest image. From this analysis, we were able to decrease the number of false-positive errors from an average of 12 to approximately 5 per image without eliminating any true nodules. CONCLUSION: Our results show that incorporating knowledge from experienced chest radiologists into the computer algorithm will play an important role in the development of computerized schemes for the detection of pulmonary nodules.

Diagnostic Errors↗
PubMed1992

Computer-aided diagnosis: development of automated schemes for quantitative analysis of radiographic images.

Preliminary results obtained with computer-aided diagnosis (CAD) from various radiographic examinations are very encouraging. However, CAD is still at an early stage of its development. It will be necessary to increase further the understanding of image features of normal and abnormal patterns, to establish databases, and to devise specific approaches for particular types of pathology. Although the existing schemes are designed to be applied to digital radiographs, similar techniques can be applied in the future to cross-sectional images such as CT, MRI, and ultrasound. We believe that CAD will become clinically practical in the near future.

Angiography↗
PubMed1979

Intrathoracic rib: radiographic features of two cases.

Two cases of intrathoracic rib are presented. In one of these the anomalous rib was not supernumerary, and the investing layers of pleura caused the rib to appear abnormally dense. The relevant literature is briefly reviewed.

Adult↗
PubMed1979

Erect scanning of pancreas using a gastric window.

A technique that can offer improved ultrasonic visualization of the pancreas is reported and evaluated. One hundred subjects were scanned in an erect sitting position with fluid-filled stomachs ("erect gastric window" technique). Conventional supine scans were initially performed in all cases; oblique, semierect, decubitus, prone, and standing positions with and without fluid-filled stomach were also evaluated. Compared with supine scans, the "erect gastric window" technique, occasionally supplemented by semierect, oblique, or decubitus views, provided significantly improved visualization of the pancreas in 93% of subjects. The nonvisualization rate was reduced from 19% to 1%.

Administration, Oral↗
PubMed1978

Multicentric tracheobronchial and oesophageal granular cell myoblastoma.

Two patients with multiple intrathorcic granular cell myoblastomas are described. In one case multiple tumours were present in the major airways and oesophagus. The patient presented with recurrent pulmonary infections and stridor due to airway obstruction. In the other case dysphagia caused by multiple oesophageal granular cell myoblastomas was the major symptom. Granular cell myoblastoma is a rare tumour of neurogenic origin with a characteristic histological appearance. The pattern of multiple tracheobranchial and oesophageal tumours is uncommon and forms the basis of this report.

Adult↗
PubMed1978

The diagnostic significance of gallium lung uptake in patients with normal chest radiographs.

Nine patients were encountered with normal chest radiographs, but diffuse bilateral lung uptake of 67Ga-citrate. They were divided into three groups. The first consisted of 6 patients who had lymphoma or leukemia and had had multiple cycles of chemotherapy. Here, abnormal uptake may have resulted from a toxic effect of the drugs or from a low-grade, subclinical infectious process. The 2 patients in the second group were drug addicts and a subradiographic interstitial inflammatory reaction was probably responsible for abnormal uptake. The last patient had diffuse uptake of 67Ga-citrate throughout the lungs two weeks before lymphomatous infiltrates became radiographically visible.

Adult↗
PubMed1976

Bronchial web diagnosed by bronchography.

Bronchial webs are rare lesions which often go unrecognized. The authors describe a patient who presented with right-lower-lobe bronchiectasis and at-electasis secondary to a web in the right-lower-lobe bronchus. This is the first known instance where such a lesion has been demonstrated by bronchography. The etiology of this and similar lesions reported in the literature remains obscure.

Bronchi↗
PubMedDate not supplied

Image feature analysis and computer-aided diagnosis in digital radiography: automated detection of pneumothorax in chest images.

In order to aid radiologists in the diagnosis of pneumothorax from chest radiographs, an automated method for detection of subtle pneumothorax is being developed. The computerized method is based on the detection of a fine curved-line pattern, which is a unique feature of radiographic findings of pneumothorax. Initially, regions of interest (ROIs) are determined in each upper lung area, where subtle pneumothoraces commonly appear. The pneumothorax pattern is enhanced by the selection of edge gradients within a limited range of orientations. Rib edges included in this edge-enhanced image are removed, based on the locations of posterior ribs that are determined separately. A subtle curved line due to pneumothorax is then detected by means of the Hough transform. The detected pneumothorax pattern is marked on the chest image displayed on a CRT monitor. With the present computer method applied to 50 chest images (28 normals and 22 abnormals with pneumothorax), we were able to detect 77% of pneumothoraces, with 0.44 false-positives per image.

Humans↗