Biomedical subjects

J Drace

Publications and source records attributed to J Drace.

5 recordsLinked to original sources

PubMed1995

Registration error quantification of a surface-based multimodality image fusion system.

This paper presents a new reference data set and associated quantification methodology to assess the accuracy of registration of computerized tomography (CT) and magnetic-resonance (MR) images. Also described is a new semiautomatic surface-based system for registering and visualizing CT and MR images. The registration error of the system was determined using a reference data set that was obtained from a cadaver in which rigid fiducial tubes were inserted prior to imaging. Registration error was measured as the distance between an analytic expression for each fiducial tube in one image set and transformed samples of the corresponding tube obtained from the other. Registration was accomplished by first identifying surfaces of similar anatomic structures in each image set. A transformation that best registered these structures was determined using a nonlinear optimization procedure. Even though the root-mean-square (rms) distance at the registered surfaces was similar to that reported by other groups, it was found that rms distances for the tubes were significantly larger than the final rms distances between the registered surfaces. It was also found that minimizing rms distance at the surface did not minimize rms distance for the tubes.

Biophysical Phenomena↗

PubMed1990

Evaluation of a fiber optic glove for semi-automated goniometric measurements.

Normal subjects were used to evaluate a fiber optic instrumented glove for semi-automated goniometric measurement. The glove electronically records and transmits hand and finger position to a host computer by measuring the amount of joint flexion. The glove was put through a series of range-of-motion (ROM) tests with five subjects. Metacarpal (MP) and proximal interphalangeal (PIP) joint angles of the five digits were compared during repetitive standardized motions to evaluate the glove's repeatability. The results showed an overall error of 5.6 degrees, as compared to an error of between 5 and 8 degrees with manual measurement. Additional tests were done to determine factors such as fit, grip force, and wrist motion that may contribute to the overall error. The glove should have applicability to some aspects of hand evaluation as a semi-automated goniometric measurement device.

Adolescent↗

PubMed1987

Use of cerebrospinal fluid gating to improve T2-weighted images. Part II. Temporal lobes, basal ganglia, and brain stem.

Ungated and gated magnetic resonance images of the temporal lobes, basal ganglia, and brain stem acquired with the use of long repetition times (TRs) and long echo-delay times (TEs), were compared quantitatively. Twenty-five pairs of images obtained on a 1.5-T system were evaluated. Ungated images (TR = 2,000 msec, TE = 80 msec) were acquired in the same manner as gated images except for TR, which, for gated studies, was determined by a patient's heart rate and generally fell into the 1,500-1,800-msec range. Three image parameters were assessed: signal-to-noise ratio (S/N), object contrast, and resolving power. In both normal and abnormal brain tissue, gated images were superior to ungated images in object contrast and resolving power and equivalent in S/N. More so than in comparable studies of the spinal cord, ungated studies were susceptible to both false-positive and false-negative interpretations. As in spinal cord studies, the major benefit of gating was the elimination of phase shift images arising from basal cisterns and the third ventricle.

Basal Ganglia↗

PubMed1986

Mammographic microcalcifications: detection with xerography, screen-film, and digitized film display.

Pulverized bone specks and aluminum oxide specks were measured by hand into sizes ranging from 0.2 mm to 1.0 mm and then arranged in clusters. These clusters were superimposed on a human breast tissue phantom, and xeromammograms and screen-film mammograms of the clusters were made. The screen-film mammograms were digitized using a high-resolution laser scanner and then displayed on cathode ray tube (CRT) monitors. Six radiologists independently counted the microcalcifications on the xeromammograms, the screen-film mammograms, and the digitized-film mammograms. The xeromammograms were examined with a magnifying glass; the screen-film images were examined with a magnifying glass and by hot light; and the digitized-film images were examined by electronic magnification and image processing. The bone speck size that corresponded to a mean 50% detectability level for each technique was as follows: xeromammography, 0.550 mm; digitized film, 0.573 mm; and screen-film, 0.661 mm. We postulate that electronic magnification and image processing with edge enhancement can improve the capability of screen-film mammography to enhance the detection of microcalcifications.

Breast Diseases↗

PubMed1984

Specific CT findings in Krabbe disease.

Specific computed tomography (CT) findings in four patients with biochemically proven Krabbe disease included symmetric increased attenuation in the cerebellum, brainstem, thalami, caudate nuclei, and corona radiata before and in conjunction with decreased attenuation of white matter followed by atrophy at a later stage. Familiarity with the CT findings in the acute phase of Krabbe disease may assist clinicians in limiting the differential diagnosis and requesting appropriate laboratory tests.

Brain↗