152 Objectives Normal pharmacologic responses to dipyridamole infusion include increased heart rate, decreased systemic blood pressure and decreased LVESV with resultant increased left ventricular ejection fraction. Our hypothesis was that the LVESV ratio (LVESV measured during dipyridamole effect vs. prior to infusion at rest), was a more accurate method to identify patients with obstructive multivessel CAD vs. TID, decrease in left ventricular ejection fraction (LVEF), or increase in left ventricular end diastolic volume (LVEDV) ratio during dipyridamole infusion. Methods Patients who had undergone both PET/CT Rb-82 myocardial imaging and x-ray coronary arteriography were included. Exclusion criteria included prior revascularization. Patients were divided, based on the absence (Group I, n= 45) or presence of multivessel CAD (Group II, n= 56). One blinded observer [RLE] processed all images using 4DM PET software. Data were analyzed by the area under the curve receiver-operator characteristic curve [AUC-ROC]. Evaluation of perfusion images were excluded from this study. Conclusions The LVESV ratio(AUC 0.86 +/- 0.04) is an accurate method to identify obstructive multivessel CAD, independent of perfusion imaging and superior to measurement of TID, decrease in ejection fraction and increase in LVEDV ratio

2005 Objectives: Our study goal is to acquire aligned stress PET Rb82 and CT images as an alternative to software alignment tools, which may have large inter-operator variability and the potential to create artifactual PET results. Methods: For PET attenuation correction we acquire 3 ultrafast CT image datasets. During free breathing, each CT scan [120 kVp, 11 mAs, 0.5 sec rotation] spanned a field-of-view of 16.6 cm in 2.7 seconds with 2.0 mm thick axial slices. Dose per CT scan was 0.74 mSv. In 102 consecutive patients (pts), 1 CT (sCT1) was acquired 1-2 min after dipyridamole infusion but before acquiring stress PET, and 2 CTs (sCT2 and sCT3) were acquired post-stress PET. Sagittal, coronal and axial images were assessed for PET/CT alignment visually, and graded with the following alignment index (AI): AI=0: no apparent misalignment (ma); AI=1: small ma (1/4-1/2 myocardial wall thickness (MWTh)); AI >1 [>1/2 MWTh]. 2) On 12 randomly selected studies with AI=1, we used a 3D shift-fusion program to determine the AP, LR, and foot-to-head (z) spatial shift necessary to produce AI=0. 3) A PET normal file (nlfile) of 8 pts with low probability of CAD was established. The CT data of the 8 pts were manually shifted towards the feet (-z direction) by 1 and 2 centimeters. PET Bull’s-eyes for the 0, 1 and 2 cm shifted data were compared to nlfile and image findings were correlated with AI determination. Results: 1) 85% patients had at least 1 of 3 CTs with AI = 0, while 14% had AI=1, and 1% had AI>1. 2) Average spatial shift necessary to produce AI=0 from AI=1 was (in mm) AP: 2.8+/1.0; LR: 0.3+/-0.8; z: 4.4+/-2; total: 5.53+/-3.2. 3) Simulation study showed that 100% (9/9) studies were normal with AI=0 and AI=1 (5/5), and that 100% (10/10) studies were abnormal with AI>1. Conclusions: 1) A 3-CT protocol yields a large percentage of studies with AI= 0. 2) Average spatial shift of AI=1 studies is 5.5 +/- 3.2 mm. 3) Simulation study shows that AI=0 or AI=1 yields correct (normal) findings, while AI >1 gives incorrect (abnormal) results. 4) Using a 3-CT, ultrafast protocol, 1 may need software alignment.

Accordingly,defects inmyocardialperlusion images must be interpreted as representing the integrated result of the combinabonof bloodflow and segmentalcontrac@on heterogeneity.

Part I covers metabolic imaging with FDG (in section A), and perfusion imaging with N-ammonia and Rb (in section B). The information for each section is in Table format. First there is an introduction to each table, then the Table itself, and finally Notes for the Table. The Table summarizes the acquisition or patient preparation parameters. Each entry in the table refers to a note which discusses the entry in greater detail.

Despite its limited sensitivity and specificity in patients with low to intermediate probability of coronary artery disease (CAD), exercise treadmill testing (ETT) is frequently used as the initial test for investigation of chest pain. Although myocardial perfusion imaging is a significantly more accurate test, its added cost to ETT is considerable. The cost of a non-contrast electron beam computed tomography (EBCT) scan is comparable to that of ETT and the calcium score (CS) correlates closely with the volume of atherosclerotic plaque. Therefore, we tested the hypothesis that EBCT might be an effective and cost-beneficial technique for the identification of angiographically obstructive CAD (> or = 50% stenosis) in patients with low to intermediate pretest probability of disease. We calculated the theoretic cost of attaining a diagnosis of CAD based on a Bayesian model that utilizes published sensitivity and specificity levels for ETT, EBCT, and stress myocardial perfusion imaging. We then submitted a cohort of 207 patients with low to intermediate probability of disease both to EBCT and ETT in random order, and estimated the cost of achieving a correct diagnosis by either route based on the number of expected further tests. An EBCT calcium score of 150 was chosen as a cut-point with a sensitivity of 74% and a specificity of 89% for the presence of obstructive CAD. The theoretic Bayesian model predicted substantial cost savings when EBCT was used as the initial test instead of ETT, with decreasing benefit as the prevalence of disease increased (44% saving at 0% prevalence; 15% saving at 100% prevalence). In the patient cohort, the diagnostic pathway starting with EBCT provided a 45% to 65% cost saving over the ETT pathway. We conclude that in patients with low to intermediate pretest probability of disease, a pathway based on EBCT as the initial test to investigate presence of obstructive CAD provides a substantial cost benefit over a pathway based on ETT. Such cost advantages decrease as the prevalence of disease increases.

This article reviews selected literature that can be useful for analysis of cost-effectiveness (CE) of diagnostic procedures in patients with known or suspected coronary artery disease. First, a clinical example illustrates some of the issues involved. Four questions are used to organize the material: (1) What is CE analysis? (2) Why should we use CE analysis? (3) Who should perform CE analysis? and (4) How should CE analysis be performed? (1) What is CE analysis? CE analysis differs from cost-reduction or cost-benefit analysis but may encompass cost-utility analysis. Marginal CE emphasizes differences in CE between different strategies. (2) Why should we use CE analysis? Nuclear cardiology depends on the fruits of medical technology, and many policy makers blame technology for escalating costs of health care. This situation requires us to reduce the absolute cost or the increment in cost, as well as to assess the true value of the technology we use. (3) Who should perform CE analysis? A team approach is the best answer to combine the expertise from clinicians and economists. A team approach and detailed definitions of assumptions can help minimize potential bias. (4) How should CE analysis be performed? CE analysis requires formulating important questions, designing alternative scenarios or strategies, selecting values for the numeric variables and including the probability that an event will occur, calculating cost per outcome, and sensitivity analysis of the model. The appropriate goal of CE analysis of the clinical use of cardiac imaging procedures is, first, to help improve patient outcome and, second, to limit costs.

Diagnosis and assessment of coronary artery disease (CAD) is especially difficult in women. The history of chest discomfort and various noninvasive tests each have particular problems, which indicate the need to consider more accurate tests such as cardiac magnetic resonance imaging (MRI) and positron emission tomography (PET). MRI of cardiac function at rest and during dobutamine stress has good accuracy, and MR Myocardial perfusion imaging (MPI) with gadolinium DTPA looks promising. The most exciting MR method is cineangiography (MRA), which images blood flow through the coronary arterial lumen as an intense signal. In an initial clinical trial this method showed excellent sensitivity and fair specificity in patients in whom adequate images could be obtained. MR spectroscopy (MRS) has imaged changes in high energy phosphates in patients with severe coronary stenoses during handgrip exercise, but is still experimental. PET MPI corrects the images for attenuation problems that limit the use of other radionuclide imaging procedures in women more than in men. Many studies show excellent sensitivity and specificity to diagnose CAD by PET MPI. In view of its clinical validation and the safety of dipyridamole relative to dobutamine, PET MPI appears to be the best test for assessing CAD in women. The greater accuracy of PET (or perhaps of fully developed MRI/MRA systems) will produce better clinical outcomes and cost-effectiveness for most patients than will less accurate modalities, despite their higher initial cost.

A 63-year old, obese lady is seen by her doctor because of atypical chest pain (Figure 9-1) (see Color Plates section). She has a history of diabetes, hypertension, and mildly elevated cholesterol levels, and her electrocardiogram (ECG) is consistent with left ventricular hypertrophy. Her private physician believes in performing the cheapest, least invasive test first. He orders a stress ECG ($330). The ECG is positive (1.5 mm of horizontal ST depression) at 6 min of a modified stress test. Because there is a history of hypertension and left ventricular hypertrophy on ECG, the significance of the “abnormality” on the stress ECG is questioned by the physician, who then decides a radionuclide stress test might add more certainty to the diagnosis. Exercise 201Tl SPECT imaging ($1200) is then performed, but the presence of attenuation caused by breast tissue causes an “equivocal” interpretation. At this point, cardiac catheterization is performed ($4800) and the patient is found to have normal coronary arteries at a total cost of $6330 for all three procedures. Had this physician obtained a positron emission tomography (PET) MPI after the equivocal 201Tl, the negative result would have saved 53% or $3300 ($6330–$3000). If a PET had been obtained in this woman as the first test, the savings would have been 72% or $4530.