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Biomedical subjects

D P Carmody

Publications and source records attributed to D P Carmody.

12 recordsLinked to original sources
PubMed2001

Machine classification of dental images with visual search.

RATIONALE AND OBJECTIVES: The authors performed this study to assess the performance of a computer-based classification system that uses gaze locations of observers to define the subspace for machine learning. MATERIALS AND METHODS: Thirty-two dental radiographs were classified by an expert viewer into four categories of disease of the periapical region: no disease (normal tooth), mild disease (widened periodontal ligament space), moderate disease (destruction of the lamina dura), and severe disease (resorption of bone in the periapical area). There were eight images in each category. Six observers independently viewed the images while their eye gaze position was recorded. They then classified the images into one of the four categories. A sample of image space was used as input to a machine learning routine to develop a machine classifier. Sample space was determined with three techniques: visual gaze, random selection, and constrained random selection. K analyses were used to compare classification accuracies with the three sampling techniques. RESULTS: With use of the expert classification as a standard of reference, observers classified images with 57% accuracy, and the machine classified images with 84% accuracy by using the same gaze-selected features and image space. Results of kappa analyses revealed mean values of 0.78 for gaze-selected sampling, 0.69 for random sampling, 0.68 for constrained random selection, and 0.44 for observers. The use of sample space selected with the visual gaze technique was superior to that selected with both random-selection techniques and by the observers. CONCLUSION: Machine classification of dental images improves the accuracy of individual observers using gaze-selected image space.

Artificial Intelligence↗
PubMed2001

Spatial orientation adjustments in children with autism in Hong Kong.

Abnormal spatial orientation and body postures in children with autism often interfere with visual abilities to attend tasks and social interactions. Twenty-four children diagnosed with autism from Kowloon, Hong Kong were assessed for spatial orientation and spatial management abilities. Positive changes in spatial orientation were evident when the children wore ambient prism lenses and included changes in posture from slanted to erect. Adjustments in spatial management were evident in improved ball catching ability, a task requiring visual tracking and eye-hand coordination. The findings suggest that alterations to the sensory systems may lead to behavioral change in some children.

Adolescent↗
PubMed1997

A signal detection theory analysis of gap detection in the rat.

An innocuous sensory event (a prestimulus) briefly preceding a startle-eliciting stimulus (SES) reduces the amplitude of the elicited reflex. This study used signal detection theory (SDT) techniques to quantify the effects of gaps (pauses in otherwise continuous noise) on the rat's acoustic startle reflex. Sixteen rats were given four identical test sessions consisting of the randomized presentation of 150 trials of the SES alone and 150 trials of a gap-and-SES combination. Gap duration (1, 2, 4, and 8 msec) varied between sessions. Data analyses based on amplitude, difference scores, percentage scores, and SDT techniques identified similar patterns. The three longest gaps, but not the shortest, were reliably detected, and differences among these three were identified with percentage and SDT analyses. Analyses of amplitude changes over test sessions yielded different patterns for each measure. The results demonstrate that an SDT analysis is a sensitive index of prestimulus effects.

Animals↗
PubMed1996

Postural orientation modifications in autism in response to ambient lenses.

Autistic children often display abnormal postures, head tilts, and other spatial management dysfunctions. Methods were introduced to measure spatial orientation in tasks in a group of fourteen autistic children in Montreal, Canada. Ambient lenses were found to improve posture, correct head tilts, and improve ball catching abilities. A model of spatial orientation is described and recommendations are made to incorporate ambient lenses in treatment programs.

Adolescent↗
PubMed1991

Limitations in distinguishing malignant from benign lesions of the breast by systematic review of mammograms.

Our objective was to assess whether or not a systematic review of mammographic descriptors would result in improved classifications of nonpalpable lesions of the breast and reductions of biopsies for benign conditions. The prelocalization mammograms of 200 consecutive patients who had 231 biopsies were reviewed in random order by four radiologists experienced in mammography. Each reader assessed the presence of 32 specific descriptors regarding masses and calcifications. The following descriptors were highly associated with malignancy: for masses, inhomogeneous density; irregular shape; spiculated borders; and for calcifications, many calcifications; microcalcifications; linear or branching patterns, or both, and high spatial density. For masses, the descriptors highly associated with benignity were homogeneous density, oval shape and sharp or lobulated borders. For calcifications, the descriptors highly associated with benignity were solid, round and irregularly shaped. Readers indicated their over-all rating of each lesion, ranging from definitely benign to definitely malignant. Ratings were compared with the findings of pathologic reports (181 benign to 50 malignant), and receiver operating characteristic analyses were performed. The areas under the curves (A[z]) varied from 0.65 to 0.78. If biopsies had not been performed on those patients who were judged to have most likely benign lesions, one could reduce the number of biopsies for benign conditions by 48 to 69 per cent; however, 18 to 46 per cent of the malignancies would be missed. We conclude that diagnoses based on a systematic review of descriptors are not sufficiently accurate to reduce the number of mammary biopsies.

Adult↗
PubMed1990

Limited correlation of left ventricular end-diastolic pressure with radiographic assessment of pulmonary hemodynamics.

Left ventricular end-diastolic pressure (LVEDP) is a reliable indicator of the diastolic function of the left ventricle. The purpose of this study was to correlate the radiographic assessment of pulmonary hemodynamics with LVEDP. The study population consisted of 104 consecutive patients with four categories of LVEDP: less than 13 mm Hg (n = 26), 13-19 mm Hg (n = 30), 20-24 mm Hg (n = 24), and more than 24 mm Hg (n = 24). Chest radiographs obtained within 24 hours of cardiac catheterization were assessed for evidence of congestive heart failure (CHF) by three experienced radiologists. Findings were graded from 0 to 3 (normal to abnormal) on the basis of the following signs of CHF: redistribution, perihilar and perivascular haze, peribronchial cuffing, pulmonary artery-bronchus ratio, septal lines, subpleural edema, air-space edema, pleural effusion, cardiomegaly, and overall radiographic assessment of CHF. A consensus report was then generated. In patients with LVEDP over 20 mm Hg, 38% did not show CHF in the overall assessment. Correlation between radiographic signs of CHF and LVEDP was limited.

Cardiac Catheterization↗
PubMed1980

An analysis of perceptual and cognitive factors in radiographic interpretation.

Detection of small tumors in chest x-ray films was studied under tachistoscopic viewing conditions designed to stimulate single fixations varying in dwell time, found in free search. Two questions were asked: How much dwell time is required to detect a nodule (experiment 1)? How effective are peripheral inputs in the detection of a nodule (experiment 2)? Our findings indicate that a dwell time of 300 ms was sufficient to detect 85% of the nodules when they were viewed directly. Detection accuracy was reduced by one-half when the tumor was located 5 degrees from the axis of gaze. Taken together with data from eye movement experiments, these results provide useful estimates of perceptual and cognitive parameters of visual search.

Cognition↗
PubMed1977

Global detection of symmetry.

Two experimental approaches examined observers' ability to characterize shape symmetry based upon the information obtained within a single fixation. Exp. I tested observers' ability to discriminate among three levels of symmetry on the basis of a 25-msec. presentation. Results indicated that identification accuracy was higher for symmetrical and asymmetrical shapes than for mixed shapes, which contained both symmetrical and asymmetrical components. Exp. II tested observers' ability to detect a given level of symmetry by means of a signal-detection approach. Symmetrical shapes were detected better than asymmetrical shapes. Detectability of mixed shapes was lower than that for both symmetrical and asymmetrical shapes. The results of Exps. I and II demonstrate that observers can characterize shape symmetry on the basis of information available within a single fixation. The data are supportive of the hypothesis that a global response to the over-all configuration of the shape serves to facilitate form perception.

Discrimination, Psychological↗
PubMedDate not supplied

Global and segmented search for lung nodules of different edge gradients.

Chest films were inspected by staff and resident radiologists for lung nodules under two viewing conditions: segmented search, in which films were divided into six sections and viewed piecemeal, and global search, in which the complete film was presented and viewed in its entirety. Nodules varied in edge gradient from sharp to fuzzy. Nodules with sharper edges were identified faster, more frequently, and with higher confidence than nodules with less sharp edges. Segmented search did not increase the probability of nodule detection; rather, it led to an increase in the number of false-positives, resulting in lower overall performance when compared with global search. The results are interpreted according to a visual search model which calls for the use of comparative scanning strategies to differentiate nodule-containing areas from nodule-free areas on chest films.

Decision Making↗
PubMedDate not supplied

Comparison scans while reading chest images. Taught, but not practiced.

Radiology instructors and residents were surveyed for their methods of instruction concerning viewing techniques. A similar group of radiologists had their eye activity measured as they viewed chest images. Image reading techniques are taught to be systematic and directive with comparisons of bilateral features. Yet, most images are read by a free search method; bilateral comparisons comprise less than 4% of the visual activity. Instructors and residents show this discrepancy between instructional techniques and reading practice.

Eye Movements↗