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J J McInerney

Publications and source records attributed to J J McInerney.

15 recordsLinked to original sources
PubMed1994

A line-focus collimator with a field of view of uniform thickness.

A new line-focus x-ray collimator features a field of view (FOV) with uniform thickness in the near field between the collimator and focal line. General design equations were developed and then constrained to define such a uniform FOV. A prototype collimator was experimentally evaluated using a Compton backscatter imaging technique. The full-width-tenth-max (FWTM) thickness, measured at 420 locations in the near field, showed good uniformity (1.51 +/- 0.06 cm) and closely approximated the nominal design thickness (1.8 cm).

Equipment Design↗
PubMed1994

Real-time ventricular volumes and cardiac function in the working rat heart.

The measurement of instantaneous left ventricular volumes throughout the cardiac cycle in a rat heart beating at rates of 300 to 600 min-1 with a chamber volume of only a few tenths of a milliliter is difficult. Combining an x-ray scatter detection system with a small x-ray source collimated to scatter low energy x-rays off a working rat heart, measurements of real-time changes in ventricular volumes can be determined. The x-ray scatter signal is proportional to the volume and can be calibrated to measure the actual volume. Using this system, changes in ventricular function can readily be detected. An example of data obtained from increasing preload with a fixed afterload is shown. This technique not only distinguishes an increasing stroke volume, but also more rapid early diastolic filling and systolic ejection rates with increasing preload. This new x-ray scatter technique appears to be a promising way to measure rapidly changing left ventricular volumes and function in the working rat heart. This could significantly enhance the scientific use of the rat model.

Animals↗
PubMed1994

Analysis of edge-tracking errors inherent in fluoroscopic images of the beating heart.

RATIONALE AND OBJECTIVES: Because of the complex relationships between the dynamic three-dimensional cardiac surface shape and its projected image, errors arise with the use of two-dimensional silhouettes to measure displacements of the heart. The character and frequency of such errors are examined. METHODS: A high-precision x-ray scatter imaging technique was used to reconstruct the three-dimensional shape of the left ventricular free wall throughout the cardiac cycle. Displacements of the three-dimensional surface were then compared with those on the two-dimensional projected silhouette. Silhouette displacement errors were determined as a function of time during the cardiac cycle and variability between hearts. RESULTS: Differences between silhouette measurements and those on the cardiac surface range from 0% to 125% of peak-to-peak displacements occur, along 33% to 75% of the silhouette contours and cover 66% of the cardiac cycle. CONCLUSION: Two-dimensional silhouette displacements provide inconsistent measurements of motion patterns on the three-dimensional cardiac surface.

Animals↗
PubMed1994

Real-time volume measurements in the isolated beating rat heart.

A new technique, utilizing scattered X-rays, has been developed that is capable of measuring isolated working rat heart left ventricular (LV) volumes continuously throughout the cardiac cycle. The technique was validated by comparing cardiac outputs measured via fluid collections (r = 0.959, n = 10). The new methodology will permit real-time measurements of pressure-volume relationships, stroke work, and indexes of diastolic function in the isolated working rat heart.

Animals↗
PubMed1994

The effects of pacing site on left ventricular epicardial surface velocity patterns during systole.

Changes in epicardial LV velocity patterns during isovolumic contraction and ejection as induced by ventricular pacing were studied in 15 canines. A noninvasive imaging technique that provided high temporal resolution was used to study the timing of an outward expansion of the LV during isovolumic contraction and the propagation pattern of an inward LV velocity wavefront during ejection. With this technique, surface displacements were measured (+/- 0.1 mm SD) at 50-70 locations on the LV free wall at 5-msec intervals. Velocities were calculated by differentiating the surface displacement waveforms and an interpolation procedure was used to provide detailed color coded velocity maps of the LV surface. LV surface velocities were determined from data obtained during closed-chest endocardial pacing from each of four sites: right atrium, right ventricular apex, left ventricular apex, and right ventricular outflow tract. These surface velocities showed a distinct spatial and temporal pattern for each pacing site. The results show that this noninvasive mapping procedure has potential for determining the location of an ectopic ventricular focus.

Animals↗
PubMed1994

Inward diastolic motion: a normal component of isovolumic relaxation and rapid refill.

Many reports note expansive events occurring in the left ventricle during isovolumic relaxation. Expansions during isovolumic relaxation require compensatory inward displacements elsewhere in the ventricle. The location and character of such compensatory displacements have been a continuing source of speculation. Using a high-precision Compton backscatter imaging (CBI) technique, we have detected an early diastolic inward motion that initiates during isovolumic relaxation on the right and left epicardial free walls of the heart in 100% of the 14 normal canines we have studied. This inward motion is first detected 20-30 ms after left ventricular maximal rate of pressure decrease over time (-dP/dtmax), lasts into the early rapid filling phase with a mean duration of 92 +/- 5 (SE) ms, and ends approximately 30 ms after opening of the mitral valve. Maximum wall velocities during this time period (approximately 20 mm/s) exceed those occurring in the same regions during systole. Inward surface displacements in the areas undergoing inward motion average 1.1 +/- 0.2 and 0.9 +/- 0.2 mm on the left and right side of the heart, respectively.

Animals↗
PubMed1990

Determination of regional myocardial perfusion by x-ray fluorescence.

Validation studies were performed to demonstrate the effectiveness of an x-ray induced fluorescence system in quantitating regional myocardial perfusion in vivo. In a series of 13 open-chested canines, x-ray induced fluorescence was used to simultaneously monitor iodine concentration transients which arose in the left ventricular lumen and in the myocardium after the intravenous injection of an iodinated flow tracer. Deconvolution of the recorded transients produced a transfer function from which the mean transit time for the tracer to travel between the left ventricular lumen and the myocardium was calculated. Measurements of regional myocardial perfusion (Q) made by radioactive microspheres were compared with the reciprocals of the mean transit times (MTT-1) and gave a linear correlation (n = 38): MTT-1 = 0.033 + 0.069 Q, r = 0.71. Comparison of the percent change in perfusion (dQ) relative to a control study for each dog with the percent change in the respective reciprocals of the mean transit times (dMTT-1) produced a linear correlation coefficient of r = 0.88 for the regression line dMTT-1 = 0.46 dQ - 10.7. The x-ray induced fluorescence system may provide a minimally invasive means for monitoring iodine concentration transients and determining relative, if not absolute, measures of regional myocardial perfusion.

Animals↗
PubMed1989

High precision Compton backscatter maps of myocardial wall dynamics. Theory and applications.

Compton backscatter imaging (CBI) is a technique that uses x-rays scattered from the closed-chest surface of the heart to obtain high frequency (5 msec) and high precision (+/- 0.1 mm SD) measurements of regional surface displacements and velocities. These measurements are acquired in a three-dimensional format that allows the reconstruction of the epicardial surface and the creation of color coded displacement and velocity maps at many time points during the cardiac cycle. Applications of the technique are shown to characterize detailed regional normal wall displacement and velocity patterns, and the significant alteration of those patterns after coronary embolization. The technique is also applied to the characterization of early diastolic wall dynamics. CBI measurements show that a brief and somewhat paradoxical inward displacement of the anterior ventricular wall occurs during early diastole in normal canines. The wall dynamics associated with this inward displacement suggest a brief collapse of the ventricle subsequent to aortic valve closure. Diastolic collapse velocities and displacements are significantly altered subsequent to coronary occlusion with mean and maximum collapse velocities decreasing by 50% and concomitant inward displacements decreasing by 40%. Data acquisition with CBI is non-invasive, does not require contrast agents or radioisotopes, and uses low irradiation levels (125 kVp, 3-5 ma). The average radiation dose to the heart for a typical study is 250 mrem, significantly lower than that of other radiation based imaging techniques.

Animals↗
PubMed1988

Coronary artery embolization in closed-chest canines using flexible radiopaque plugs.

A new technique induces localized myocardial infarction in closed-chest dogs by placing discrete plugs in coronary arteries without using cumbersome coaxial catheters or guide wires. Flexible plugs, essential to this method, are formed by extruding a dental impression polymer, rendered radiopaque with sodium iodide, into spaghetti-like strands. Segments of these strands can be injected through a catheter into a selected coronary artery. Contact with blood or saline causes plugs to swell. The mean increase in plug diameter due to swelling was 27 +/- 20%. Eight anesthetized dogs were embolized via carotid approach [6 left anterior descending (LAD), 1 left circumflex (LCX), and 1 LAD and LCX]. Plug positions were monitored fluoroscopically. One animal died at 2 days postembolization. The remaining seven dogs were killed after 14-37 days. Autopsies showed complete vessel occlusion and localized infarction. Infarcts resulting from coronary artery occlusion with one, two, or three plugs involved 2-26% of the left ventricular mass.

Animals↗
PubMed1980

Validation of dynamic radiography in the dog and evaluation of ischemic dyssynergy.

If a collimated radiation detector (sodium iodide crystal) and a collimated X-ray source are positioned at right angles, scattered radiation will be sensed and the detector will generate a signal as tissue enters and leaves the "sensitive volume" formed by the intersection of the field of view of the detector and incident beam. This technique, called dynamic radiography, was used to identify and quantify the components of epicardial motion in anesthetized open-chested dogs. The data so obtained were validated by two independent optical methods: biplane cinematography and a technique that measures the shadow cast by the heart using a light beam-cadmium sulfide photocell. Displacement measured by dynamic radiography appeared to be the time integral of the scalar product of the velocity vector and the vector normal to the surface area within the sensitive volume, i.e., that component of displacement of myocardial mass that was perpendicular to the surface of the myocardium. In other words, the dynamic radiographic signal was proportional to the mass of tissue within the sensitive volume. Good agreement in terms of absolute motion, its direction, and phase was noted between predicted dynamic radiographic signals and those observed. Thus validated, this technique was found to be reliable in quantifying motion abnormalities produced by acute coronary ligation.

Animals↗
PubMedDate not supplied

The measurement of multidimensional myocardial dynamics using scattered radiation fields.

A new radiographic device, based upon the analysis of scattered radiation fields, has been developed to measure myocardial dynamics. The device consists of an array of detectors arranged to monitor photons scattering from the epicardial surface. Data synthesis permits real-time dynamic displays of the epicardial surface in two and three dimensions. The system has been tested on close-chest canines. Epicardial surface displacements within the closed chest cavity can be measured to 0.1 mm (S.D.). Right or left ventricular surfaces may be monitored on a given scan. Surfaces behind or in front of outer myocardial boundaries within the direct field of view of the detectors are located with equal accuracy. Except for the use of low levels of fluoroscopic x-rays, the procedure is completely noninvasive. Radiation dose levels and component costs for the prototype system are modest. The detector system attaches to a standard fluoroscopic x-ray generator.

Animals↗
PubMedDate not supplied

Convective-dispersive characteristics of tracer transport calculated from transfer function analysis of biological indicator-dilution curves.

A solution to the convection-dispersion model of tracer transport in biological systems is presented. This solution provides for the characterization of tracer transport through a network of blood vessels based on the tracer transients recorded at the inlet and outlet points of the circulation under investigation. Fourier transformations of the transients are used to produce a transfer function from which the mean transit time as well as other transport characteristics can be calculated. The practical aspects of applying transfer function analysis to retrieve transport characteristics under experimental conditions are also presented. The application demonstrates the efficacy of the transfer function analysis method independent of tracer recirculation effects and a priori knowledge of actual tracer concentrations.

Biological Transport↗