[Show abstract][Hide abstract] ABSTRACT: During routine myocardial perfusion imaging, a common observation is that patients with normal cardiac function and small hearts, in particular small women, have higher left ventricular ejection fractions (LVEFs), as measured by quantitative gated SPECT (QGS) software, than anticipated, often markedly so. The goal of this project was to determine if the QGS LVEF varies with the change in end-diastolic left ventricular volume (EDV) and in particular to verify that the clinically observed phenomenon of falsely elevated QGS LVEF in patients with small hearts is actually occurring.
A series of mathematically defined left ventricles (LVs) was produced by varying the EDV and targeted LVEF (tLVEF). These were created using concentric hemiellipsoids with nine different EDVs. The tLVEF was varied from 15% to 75% by 5% increments for a total of 13 different ejection fractions. These datasets were then smoothed, creating a total of 234 sets. The smoothed and unsmoothed images were then processed using QGS software. The LVEFs and EDVs were recorded.
For lower LVEFs the agreement between the QGS LVEF and the tLVEF is good. A marked overestimation occurs when the EDVs are low and the ejection fractions are in the higher range. This effect is greater in the smoothed images.
An artifactual increase in the LVEF can occur when measurements are made with the QGS software. These data argue against using QGS LVEF for monitoring the LVEF in patients with small hearts. Our data imply that a mildly decreased LVEF may still appear to be in the normal range when measured by QGS software.
Journal of Nuclear Medicine 04/2001; 42(3):454-9. · 6.16 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Gating of myocardial perfusion imaging helps to differentiate artifacts from perfusion defects. We used this technique to evaluate the impact of routine gating on the interpretation of results by physicians experienced in this field. We studied, prospectively, 270 consecutive patients (161 men and 109 women) who underwent gated myocardial perfusion imaging. Single-photon emission-computed tomography was performed to evaluate myocardial perfusion in patients at rest and after stress, using technetium-99m sestamibi and post-stress gating. Participating physicians interpreted each study and indicated a confidence level for the interpretation. Initially, these opinions were formed on the basis of static slices alone and subsequently, with the addition of gating information. The impact of gating was evaluated by the number of studies in which gating led to a change in interpretation from normal to abnormal or vice versa, or from borderline to definite. The interpretation was changed from abnormal to normal or vice versa in 10 studies (3.7%) and from borderline to definite in 3 (1.1%). In 37 studies (13. 7%), the confidence level was increased from confident to very confident with no change in interpretation. We conclude that routine gating of every myocardial perfusion imaging study for the identification of artifacts is of low value for physicians experienced in interpreting such studies. Although gating frequently increases the confidence level, it seldom leads to a change in interpretation. Specific subgroups of patients who would benefit from gating should be identified.
Texas Heart Institute journal / from the Texas Heart Institute of St. Luke's Episcopal Hospital, Texas Children's Hospital 02/2000; 27(1):14-8. · 0.65 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Although high exercise tolerance is associated with an excellent prognosis, the significance of abnormal myocardial perfusion imaging (MPI) in patients with high exercise tolerance has not been established. This study retrospectively compares the utility of MPI and exercise ECG (EECG) in these patients.
Of 388 consecutive patients who underwent exercise MPI and reached at least Bruce stage IV, 157 (40.5%) had abnormal results and 231 (59.5%) had normal results. Follow-up was performed at 18+/-2.7 months. Adverse events, including revascularization, myocardial infarction, and cardiac death, occurred in 40 patients. Nineteen patients had revascularization related to the MPI results or the patient's condition at the time of MPI and were not included in further analysis. Seventeen patients (12.2%) with abnormal MPI and 4 (1.7%) with normal MPI had adverse cardiac events (P<0.001). Cox proportional-hazards regression analysis showed that MPI was an excellent predictor of cardiac events (global chi2=13.2; P<0.001; relative risk=8; 95% CI=3 to 23) but EECG had no predictive power (global chi2=0.05; P=0.8; relative risk=1; 95% CI=0.4 to 3.0). The addition of Duke's treadmill score risk categories did not improve the predictive power of EECG (global chi2=0.17). The predictive power of the combination of EECG (including Duke score categories) and MPI was no better than that of MPI alone (global chi2=13.5).
Unlike EECG, MPI is an excellent prognostic indicator for adverse cardiac events in patients with known or suspected CAD and high exercise tolerance.
[Show abstract][Hide abstract] ABSTRACT: Technetium 99m sestamibi is widely used in the evaluation of myocardial perfusion imaging. Although the aim of such imaging is cardiac evaluation, numerous other organs are included in the imaging field. Failure to identify incidental abnormal findings in these organs delays diagnosis and treatment. In common with other radiopharmaceutical agents, technetium 99m sestamibi is distributed throughout the body and accumulates in multiple tissues. When interpreting studies that involve this radiotracer, the physician must be aware of its physiologic distribution, in order to recognize abnormal uptake. We present an illustrative case in which areas of decreased tracer activity were noted incidentally during the evaluation of unprocessed single photon emission computed tomography data. These findings were due to metastasis of colon cancer to the liver.
Texas Heart Institute journal / from the Texas Heart Institute of St. Luke's Episcopal Hospital, Texas Children's Hospital 02/1999; 26(3):229-31. · 0.65 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The design of an automated computer algorithm for labeling the
cardiac blood pool within gated 3-D reconstructions of the radiolabeled
red blood cells is investigated. Due to patient functional
abnormalities, limited resolution, and noise, certain spatial and
temporal features of the cardiac blood pool that one would anticipate
finding in every study are not present in certain frames or with certain
patients. The labeling of the cardiac blood pool requires an algorithm
that only relies upon features present in all patients. The authors
investigate the design of a fully-automated region growing algorithm for
[Show abstract][Hide abstract] ABSTRACT: We assessed the transmyocardial laser revascularization (TMLR) as sole therapy in patients with symptomatic coronary artery disease refractory to interventional or medical treatment.
Thirty-one patients were evaluated with positron emission tomography (PET), dobutamine echocardiography, 201Tl single-photon emission computed tomography (201Tl-SPECT), and multigated acquisition radionuclide ventriculography (MUGA). TMLR was performed in 21 patients who had demonstrable ischemia in viable myocardium. The mean Canadian Cardiovascular Society (CCS) angina class was 3.70 +/- 0.7 (4 patients with unstable angina). Untreated septal segments were used as controls. At 3 months, (n = 15 patients), the mean CCS angina class was to 2.43 +/- 0.9 (P < .05). On dobutamine echocardiography, the mean resting wall motion score index was improved by 16% in lased segments (P < .03 vs control), and mean LVEF at peak stress increased by 19% (P = NS vs baseline). On 201Tl-SPECT, perfusion of lased and nonlased segments did not change. On PET, the mean ratio of subendocardial to subepicardial perfusion (SEn/SEp) increased 14% over baseline (P < .001 vs control). At 6 months (n = 15 patients), the mean CCS angina class was 1.7 +/- 0.8 (P < .05). The mean resting wall motion score index was up by 13% in lased segments (P < .05 vs control). Resting LVEF was unchanged. Stress LVEF increased 21% (P = NS vs baseline). Myocardial perfusion remained unchanged by 201Tl-SPECT. On PET, 36% of the lased segments were better, and 25% were worse compared with baseline. The resting SEn/SEp by PET was up 21% (P < .001 vs control). All deaths (two perioperative and three late) occurred in patients with preoperative congestive heart failure. Two patients required repeat revascularization of new coronary lesions.
These results suggest that TMLR improves anginal status, relative endocardial perfusion, and cardiac function in patients who do not have preoperative congestive heart failure.
[Show abstract][Hide abstract] ABSTRACT: The design of automated computer algorithms for delineating the left and right ventricular regions within gated 3-D reconstructions of the cardiac blood pool is investigated. Due to patient functional abnormalities, limited resolution, and noise, certain spatial and temporal features of the cardiac blood pool that one would anticipate finding in every study are not present in certain frames or with certain patients. Therefore, the labeling of the chambers of the cardiac blood pool requires an algorithm that only relies upon features present in all patients. We examine a sequential algorithm wherein the limiting factor in the accuracy and reliability of the algorithm is that of locating the atrio-ventricular valve planes
Nuclear Science Symposium and Medical Imaging Conference Record, 1995., 1995 IEEE; 11/1995
[Show abstract][Hide abstract] ABSTRACT: Nuclear medicine (NM) has traditionally been a non-nursing field. This specialty has grown rapidly and continues to expand. Most nurses have had very limited exposure to nuclear medicine, except in the area of patient preparation for the nuclear medicine department. Because this specialty has had significant advances that require patient monitoring in many diagnostic and therapeutic procedures, nurses will benefit by learning more about this field and by equipping themselves to care for pre- and postprocedural patients. This article is an overview of the nuclear medicine process and its most common clinical applications in the GI field as they relate to nursing practice.
[Show abstract][Hide abstract] ABSTRACT: A method for Monte Carlo simulation of a gated SPECT cardiac blood pool studies is presented. The method more accurately captures the complex structure of time-varying in vivo distributions of radiolabeled blood cells than is possible with a physical phantom. The projected utility of this method is the quantitative evaluation of manual, semi-automated, and automated methods for assessing cardiac function
Nuclear Science Symposium and Medical Imaging Conference, 1994., 1994 IEEE Conference Record; 01/1994