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R P Grenier

Publications and source records attributed to R P Grenier.

9 recordsLinked to original sources
PubMed1992

Left ventricular volume calculation using a count-based ratio method applied to first-pass radionuclide angiography.

Most count-based radionuclide methods for calculating left ventricular volume rely on measurement of radioactivity in a peripheral blood sample and a measurement of ventricle to collimator distance. We have developed a method which requires neither a blood sample nor a distance measurement and which is applicable to first-pass radionuclide angiography. The parameters used to calculate volume are the area of pixel, the total counts in the left ventricle and the maximum pixel count. The equation was used to calculate the volumes in 50 patients who had both resting first-pass radionuclide angiography (25 patients with a single crystal and 25 patients with a multicrystal camera) and contrast ventriculography on the same day. Correlation coefficients for end-diastolic and end-systolic volumes showed r ranging 0.93-0.98 and standard error of estimate ranging 23-35 ml for end-diastolic volume (14%-17% of mean end-diastolic volume) and 16-23 ml for end-systolic volume (18%-21% of mean end-systolic volume). Image processing software for extracting the needed values is generally available on most commercial nuclear medicine imaging systems and the additional time for the calculations is short. Although the theory is based on multiple assumptions, the volume calculation appears to be reasonably accurate and clinically applicable.

Adult↗
PubMed1990

Technically suboptimal first-pass radionuclide angiographic studies.

First-pass radionuclide angiography (FPRNA) has proven to correctly assess left ventricular function, however, technical difficulties do occur. One hundred and thirty one patients had contrast angiography and resting radionuclide angiography within 24 h. Of the 131 patients, 86 (66%) had adequate studies and 45 (34%) were technically suboptimal studies. In the latter group, low counts affected the quality of the images but did not change the left ventricular ejection fraction (LVEF) or regional wall motion (RWM) scores. Patients with high background activity showed overestimation of LVEF, however, by using a formula that was derived from the linear regression the LVEF could be calculated accurately in most cases. Multiple technical problems were noted in 14 patients in whom the best correlation was between contrast LVEF and background uncorrected LVEF from FPRNA (r = 0.87). In the latter group, FPRNA showed overestimation of RWM in 8 patients (57%), mainly in the inferior wall. We conclude that for most technically compromised first-pass radionuclide angiographic data, accurate LVEF values can be achieved but errors in regional wall motion interpretation will occur, especially when multiple technical problems exist.

Female↗
PubMed1990

Left ventricular volume calculation using a count-based ratio method applied to multigated radionuclide angiography.

The purpose of this study was to investigate the accuracy of a new count-proportional method for the measurement of left ventricular volume when applied to gated equilibrium blood-pool imaging. An equation is developed that relates total chamber volume, Vt, to the area of a pixel (M) and the ratio (R) of total counts within the chamber to the counts within the hottest pixel in the chamber such that Vt = 1.38 M3R3/2. The value of M is a constant for the particular scintillation camera-collimator system and R is obtained from observed count rates. All calculated volumes were compared to volumes measured using biplane contrast ventriculography. In 25 patients, the method for ventricular volumes gave an r of 0.95 and an s.e.e. of 23 ml [Volume (nuclear) = 0.94 Volume (cath) + 1.3]. Endsystolic volume was best calculated from end-diastolic volume and ejection fraction. Manual regions of interest were more accurate than automated regions of interest. This method appears to be as accurate as more complex approaches and has the advantage of not requiring attenuation correction or blood sampling.

Angiography↗
PubMed1986

High count rate first-pass radionuclide angiography using a digital gamma camera.

In this study, first-pass radionuclide angiography (FPRNA) was performed using a digital single-crystal gamma camera. Twenty-nine men and six women (ages 43-80, mean 61 yr) underwent FPRNA in the supine position immediately prior to cardiac catheterization. Total counts/sec in the whole field-of-view in the right ventricular phase were 150,352 +/- 26,006. Background uncorrected counts in the representative cycle were 7,651 +/- 2,527 at end-diastolie and 4,904 +/- 2,314 at end-systolie. A linear correlation between FPRNA left ventricular (LV) ejection fraction and contrast LV ejection fraction gave an r = 0.95 with an s.e.e. of 0.05. Analyses of intra- and interobserver variability gave r = 0.99 and 0.98 and an s.e.e. of 0.02 and 0.03, respectively. Spearman-Rank correlation coefficients between FPRNA and contrast angiographic wall-motion scores were greater than 0.8 for all walls, while sensitivity/specificity were 0.86/0.90, 0.76/1.00, 0.76/1.00 for anterior, apical, and inferior wall-motion abnormalities, respectively. We conclude that satisfactory counting statistics for FPRNA can be obtained with a digital gamma camera, and that accurate and reproducible measurements of global and regional left ventricular function can be obtained with this technique.

Adult↗
PubMed1986

Background correction in first-pass radionuclide angiography: comparison of several approaches.

This study was designed to test the comparative accuracy of several commonly used background correction techniques in first-pass radionuclide angiography (FPRNA). Thirty patients underwent FPRNA and single plane contrast angiography (CA) within 1 hr of each other. The left ventricular ejection fractions (LVEF) calculated from the different background subtraction approaches to FPRNA were compared to the CA LVEF. When applied to a representative cycle, a horseshoe-shaped background region of interest (BKROI) underestimated LVEF (p less than 0.005, r = 0.91, s.e.e. = 0.06) while a ring shaped BKROI adjusted at end-systole for aortic valve motion insignificantly overestimated LVEF (p = NS, r = 0.91, s.e.e. = 0.07). A lung background approach applied to a representative cycle gave the best correlation with CA (p = NS, r = 0.96, s.e.e. = 0.04). Without using a representative cycle, time-activity curves from a horseshoe-shaped BKROI and the LV ROI were created and the LV curve was normalized to the peak counts in the BKROI curve. LVEF calculated from the normalized curve correlated favorably with CA LVEF (p = NS, r = 0.91, s.e.e. = 0.08). The influence of some recently described improvements in representative cycle generation are also documented.

Aged↗
PubMed1984

Peak exercise and immediate postexercise imaging for the detection of left ventricular functional abnormalities in coronary artery disease.

Eleven patients without significant coronary artery disease (CAD) (group A), 22 patients with significant CAD and no prior myocardial infarction (MI) (group B), and 10 patients with CAD and a previous MI (group C) were imaged at rest, at peak exercise and immediately after exercise by first-pass radionuclide angiography. At peak exercise, mean left ventricular (LV) ejection fraction (EF) did not change significantly in group A or C and decreased significantly in group B. However, in all groups mean LVEF increased significantly immediately after exercise. Examination of potential criteria for an abnormal LVEF response showed that changes from rest to peak exercise were sensitive for detection of CAD but were not specific. Postexercise criteria were more specific but relatively insensitive: 15 of 32 patients (47%) with CAD showed a normal (greater than 5% increase over rest) response after exercise. Similarly, a regional abnormality at peak exercise was 100% sensitive, compared with a sensitivity of 78% after exercise for the whole group, and only 68% in patients without prior MI. Seven patients would have been misclassified as normal if postexercise imaging alone had been performed. The likelihood of an abnormal postexercise EF response was related to the extent of CAD: No patient with 1-vessel, 8 of 17 with 2-vessel and 9 of 12 with 3-vessel CAD showed such a response. Peak exercise imaging is necessary to achieve maximal sensitivity for the detection of CAD, and a high false-negative rate will be obtained if postexercise imaging only is used. The combination of peak exercise and postexercise imaging may be of value in assessing the severity of CAD.

Adult↗
PubMed1984

First-pass radionuclide angiography via pulmonary arterial catheters. A critical analysis of background components.

Residual background activity following first-pass radionuclide angiography was assessed in 44 patients after eliminating activity in the right heart, left lung, and most of the right lung. The ejection fraction (EF) was calculated in two ways: (a) assuming background activity was present only in the right heart and lungs, and (b) correcting for scattered radiation by placing a circular region of interest around the left ventricle. With the first method, contrast EF was significantly underestimated in both AP and RAO views. With the second method, correlation was close in both views and absolute values agreed well with contrast EF. These results indicate that there is a substantial and measurable background component, due mainly to Compton scatter, even when activity from the right heart and lungs is eliminated.

Adult↗
PubMedDate not supplied

Application of a new nuclear scintigraphy camera to evaluate flow and mechanical pumping of artificial hearts.

To assist in the development of an artificial blood pump, The Milwaukee Heart (MH-1), a new nuclear scintigraphy camera was used to study the wash-in and wash-out patterns of the MH-1. These studies indicate the MH-1 has an ejection fraction of 59.3%, with a stroke volume of 72 +/- 3 ml, and an afterload of 130 mmHg. Flow through the device is highly uniform, with no areas of stagnation. Regional ejection fraction images demonstrate homogeneous ejection from apex to base. The ability to scan through the first pass images allows study of wash-in, mixing, and wash-out of the tracer. In conclusion, this technique may provide a new approach to evaluating artificial heart pumps.

Blood Flow Velocity↗