Diagnostic value of comprehensive on-site and off-site coronary CT angiography for identifying hemodynamically obstructive coronary artery disease

BackgroundThis study aimed to investigate the diagnostic value of comprehensive on-site coronary computed tomography angiography (CCTA) using stenosis and plaque measures and subtended myocardial mass (V_sub) for fractional flow reserve (FFR) defined hemodynamically obstructive coronary artery disease (CAD). Additionally, the incremental diagnostic value of off-site CT-derived FFR (FFR_CT) was assessed.MethodsProspectively enrolled patients underwent CCTA followed by invasive FFR interrogation of all major coronary arteries. Vessels with ≥30% stenosis were included for analysis. On-site CCTA assessment included qualitative and quantitative stenosis (visual grading and minimal lumen area, MLA) and plaque measures (characteristics and volumes), and V_sub. Diagnostic value of comprehensive on-site CCTA assessment was tested by comparing area under the curves (AUC). In vessels with available FFR_CT, the incremental value of off-site FFR_CT was tested.ResultsIn 236 vessels (132 patients), MLA, positive remodeling, non-calcified plaque volume, and V_sub were independent on-site CCTA predictors for hemodynamically obstructive CAD (p < 0.05 for all). V_sub/MLA² outperformed all these on-site CCTA parameters (AUC = 0.85) and V_sub was incremental to all other CCTA predictors (p = 0.02). In subgroup analysis (n = 194 vessels), diagnostic performance of FFR_CT and V_sub/MLA² was similar (AUC 0.89 and 0.85 respectively, p = 0.25). Furthermore, diagnostic performance significantly albeit minimally increased when FFR_CT was added to on-site CCTA assessment (ΔAUC = 0.03, p = 0.02).ConclusionsIn comprehensive on-site CCTA assessment, V_sub/MLA2 demonstrated greatest diagnostic value for hemodynamically obstructive CAD and V_sub was incremental to all evaluated CCTA indices. Additionally, adding FFR_CT only minimally increased diagnostic performance, demonstrating that on-site CCTA assessment is a reasonable alternative to FFR_CT.     

Magnetic resonance microimaging for noninvasive quantification of myocardial function and mass in the mouse

The purpose of this work was to develop high-resolution cardiac magnetic resonance imaging techniques for the in vivo mouse model for quantification of myocardial function and mass. Eight male mice were investigated on a 7-Tesla MRI scanner. High-quality images in multiple short axis slices (in-plane resolution 117 μm², slice thickness 1 mm) were acquired with an ECG-gated cine sequence. Left ventricular end-diastolic and end-systolic volumes and mass were calculated from segmented slice volumes. There was precise agreement of left ventricular mass determined ex vivo and by MRI. lntraobserver (5%) and interobserver (5%) variability of in vivo MR measurements were low.     

Coronary CT angiography versus intravascular ultrasound for estimation of coronary stenosis and atherosclerotic plaque burden: A meta-analysis

BackgroundNumerous studies have compared coronary CT angiography (CTA) with quantitativecoronary angiography. However, the ability of coronary CTA to identify atherosclerosis and to accurately measure plaque and coronary area and volume measurements as compared with intravascular ultrasound (IVUS) has not been fully defined.ObjectiveWe sought to assess the ability of coronary CTA to quantify coronary and plaque measurements commonly performed with IVUS.MethodsWe searched multiple databases for diagnostic studies that directly compared coronary CTA and IVUS for coronary plaque detection, vessel luminal area, percentage of area stenosis, plaque area, and plaque volume. We used a bivariate mixed-effects binomial regression model to pool test sensitivity and specificity for detection of any coronary plaque.ResultsForty-two studies that evaluated 1360 patients (75% men; mean age, 59 years) were identified. No significant difference was found between coronary CTA and IVUS measurements of vessel lumen cross-sectional area, plaque area, percentage of area stenosis, or plaque volume within the overall cohort and no difference for the measurement of cross-sectional area (n = 5 studies) and plaque volume (n = 8 studies) among a subgroup that used automated or semiautomated measurement techniques. Sensitivity and specificity of coronary CTA to detect any plaque compared with IVUS were 93% and 92%, respectively, with an area under the receiver-operating curve of 0.97.ConclusionsCompared with IVUS, coronary CTA appears to be highly accurate for estimation of luminal area, percentage of area stenosis, plaque volume, and plaque area and for detection of plaque. The use of automated vessel and stenosis measurements appears promising in limited studies to date.     

Cardiac CT: State of the art for the detection of coronary arterial stenosis

The recent evolution of multidetector computed tomography (CT) technology has substantially improved the ability of CT to visualize the heart and coronary arteries. After injection of contrast agent, relatively reliable imaging of the coronary arteries can be achieved, even though some restrictions are caused because the spatial and temporal resolutions are still somewhat limited. Several studies have shown that stenoses of the native coronary arteries can be detected with high sensitivity and specificity if image quality is adequate. More challenging situations include imaging of patients with stents and bypass grafts. Several clinical applications have been defined as “appropriate” and include the use of CT angiography in patients who have symptoms but who cannot exercise or who have an uninterpretable stress test result, or in patients with acute chest pain of intermediate likelihood for coronary artery disease but lack of electrocardiographic changes or myocardial enzyme elevations. It can be expected that further improvement of CT technology will help to more firmly establish the clinical role of CT coronary angiography and to explore further applications of this technique.     

Absolute blood contrast concentration and blood signal saturation on myocardial perfusion MRI: Estimation from CT data

Purpose

To determine the optimal contrast injection rate and absolute blood gadolinium concentration for optimal first‐pass imaging.

Materials and Methods

The concentration of contrast medium in left ventricle (LV) was estimated from dynamic computed tomography (CT) by administering iodinated contrast medium of volume (0.2 mL/kg) equivalent to 0.1 mmol/kg of gadolinium injection in 50 subjects. A blood sample study was performed to determine the relationship between blood signal and gadolinium concentration on perfusion MRI.

Results

The mean peak gadolinium concentration in LV increased as the injection rate increased from 1 mL/sec (3.7 ± 1.2 mM), to 4 mL/sec (6.9 ± 2.7 mM) (P < 0.01). However, no significant improvement was found with an increase in the injection rate from 4 mL/sec to 5 mL/sec (6.8 ± 1.5 mM, P = 0.86). In a blood sample study the linear relationship between blood signal and gadolinium concentration was maintained in the range of ≤0.67 mM (r = 0.992), which corresponds to a peak blood concentration following a 0.01 mmol/kg gadolinium injection.

Conclusion

The optimal contrast injection rate for myocardial perfusion magnetic resonance imaging (MRI) appears to be 4 mL/sec. Saturation of arterial input signal is inevitable if the dose of gadolinium contrast medium exceeds 0.01 mmol/kg. These findings are essential for accurate quantification of myocardial blood flow from perfusion MRI. J. Magn. Reson. Imaging 2009;29:205–210. © 2008 Wiley‐Liss, Inc.     

Real-time fast strain-encoded magnetic resonance imaging to evaluate regional myocardial function at 3.0 Tesla: comparison to conventional tagging

PURPOSE: To compare the utility of the real-time technique fast strain-encoded magnetic resonance imaging (fast-SENC) for the quantification of regional myocardial function to conventional tagged magnetic resonance imaging (MRI). MATERIALS AND METHODS: Healthy volunteers (N = 12) and patients with heart failure (N = 7) were examined using tagged MRI and fast-SENC at 3.0T. Circumferential strain was measured using fast-SENC in six endo- and six subepicardial regions in the basal-, mid-, and apical-septum and the basal-, mid-, and apical-lateral wall from the four-chamber view. These measurements were plotted to tagging, in corresponding myocardial segments. RESULTS: Peak systolic strain (Ecc) and early diastolic strain rate (Ecc/second) acquired by fast-SENC correlated closely to tagged MRI (r = 0.90 for Ecc and r = 0.91 for Ecc/second, P < 0.001 for both). Both fast-SENC and tagging identified differences in regional systolic and diastolic function between normal myocardium and dysfunctional segments in patients with heart failure (for fast-SENC: Ecc = -21.7 +/- 2.7 in healthy volunteers vs. -12.8 +/- 4.2 in hypokinetic vs. 0.6 +/- 3.8 in akinetic/dyskinetic segments, P < 0.001 between all; Ecc/second = 104 +/- 20/second in healthy volunteers vs. 37 +/- 9/second in hypokinetic vs. -16 +/- 15/second in akinetic/dyskinetic segments, P < 0.001 between all). Quantitative analysis was more time-consuming for conventional tagging than for fast-SENC (time-spent of 3.8 +/- 0.7 minutes vs. 9.5 +/- 0.7 minutes per patient, P < 0.001). CONCLUSION: Fast-SENC allows the rapid and accurate quantification of regional myocardial function. The information derived from fast-SENC during a single heartbeat seems to be superior or equal to that acquired by conventional tagging during several heart cycles and prolonged breathholds.     

Technetium 99m furifosmin regional myocardial uptake in patients with previous myocardial infarction: Relation to thallium-201 activity and left ventricular function

BACKGROUND: This study was designed to compare the results of rest-redistribution thallium-201 imaging with those of rest technetium 99m furifosmin single photon emission computed tomography in the same patients with chronic ischemic left ventricular (LV) dysfunction. METHODS: Twenty-one patients (mean age 62 +/- 9 years) with chronic myocardial infarction and LV dysfunction (mean LV ejection fraction 34% +/- 8%) underwent rest-redistribution thallium imaging and resting furifosmin single photon emission computed tomography on the same day. In each patient, regional thallium and furifosmin activity was quantitatively measured in 13 myocardial segments. Regional LV function was assessed in corresponding segments by echocardiography. RESULTS: At thallium imaging, 91 (33%) segments had normal uptake, 16 (6%) showed reversible defects, and the remaining 166 (61%) irreversible defects. Of these 166 irreversible defects, 74 (45%) had moderate (> or =58% of peak activity) and 92 (55%) severe (<58% of peak activity) reduction of thallium uptake. Regional furifosmin uptake was significantly related to both rest (r = 0.87, P < .0001) and redistribution (r = 0.90, P < .0001) thallium activity. Agreement in the evaluation of regional perfusion status between thallium and furifosmin imaging was observed in 70% of the 84 hypokinetic segments (kappa = 0.54) and in 76% of the 78 akinetic or dyskinetic segments (kappa = 0.60). Concordance in the detection of myocardial viability between thallium and furifosmin imaging was observed in 69 (82%) of hypokinetic regions (kappa = 0.60) and in 65 (83%) of akinetic or dyskinetic regions (kappa = 0.67). CONCLUSIONS: These results suggest that in patients with chronic coronary artery disease and LV dysfunction, quantitative rest-redistribution thallium scintigraphy and furifosmin tomography at rest provide similar results in the evaluation of perfusion status and in the detection of myocardial viability.     

Interruption or congenital stenosis of the inferior vena cava: prevalence, imaging, and clinical findings

OBJECTIVE: To present the prevalence, clinical, and imaging findings of interruption or congenital stenotic lesions of the inferior vena cava (IVC), associated malformations, and their clinical relevance. MATERIALS AND METHODS: Between March 2004 and March 2006, 7972 patients who had undergone consecutive routine abdominal multidetector row computed tomography were analyzed for interruption or stenotic lesion of the IVC. RESULTS: Prevalence of interruption (n=8) or congenital stenosis (n=4) of the IVC occurred in 12 (0.15%) of 7972 patients. Four patients with interruption and four patients with congenital stenosis of the IVC were symptomatic with DVT (n=4), leg swelling (n=4), leg pain (n=2), lower extremity varices (n=2), hepatic vein thrombosis (n=1), and hematochezia (n=1). All four of the asymptomatic patients were from the interruption group, and these patients had interrupted IVC with well-developed azygos/hemiazygos continuation. Eight symptomatic patients did not have a well-developed azygos/hemiazygos continuation, and drainage of lower extremity was mainly from collateral veins. Additional findings in eight symptomatic patients were abdominal venous collaterals (n=8), venous aneurysm (n=2), lower extremity varices (n=2), varicocele (n=2), and pelvic varices (n=1). CONCLUSION: Interruption or stenosis of the IVC are rare on routine abdominal CT examinations and may cause different clinical findings depending on the variant drainage patterns or collaterals. Interrupted IVC is commonly asymptomatic if associated with well-developed azygos/hemiazygos continuation, whereas commonly symptomatic if well-developed azygos/hemiazygos continuation is not present.     

肺炎性肿块的CT诊断及鉴别诊断

目的探讨肺内炎性肿块的CT表现.材料和方法回顾性分析我院经手术切除、CT导引下穿刺活检及临床追踪证实的肺内炎性肿块38例(47个病灶)的CT表现.结果病灶位于肺外围、贴近胸膜面伴胸膜肥厚占80.9%;呈不规则形,三角形或锥形,尖端指向肺门或病灶长轴与支气管肺树一致占74.596;块内见气泡/蜂窝状边缘占76.6%.结论肺炎性肿块的CT表现有一定的特点,可以与肺癌鉴别.     

Simultaneous assessment of coronary stenosis, myocardial perfusion, and ventricular function in a patient with acute myocardial infarction

Cardiac CT angiography (CTA) is an ideal tool to investigate cardiac and noncardiac causes of acute chest pain. In this case, careful planning of the CTA acquisition and reconstruction limits permitted not only the exclusion of aortic dissection and provided high resolution images of coronary anatomy but also showed a concordant abnormality in myocardial perfusion and ventricular function in the setting of an acute coronary syndrome. Detailed planning of every CTA acquisition reconstruction protocol is essential to obtain the information necessary for clinical decision-making strategies and interventions in the patient with chest pain.     

双源CT对壁冠状动脉狭窄程度与心肌桥长度和厚度相关性的研究

目的 利用双源CT(DSCT)探讨壁冠状动脉(MCA)收缩期的狭窄程度与心肌桥(MB)的长度及厚度间的相关关系.方法 应用DSCT对450例可疑冠心病(CHD)和部分体检者行冠状动脉CTA,2名CT诊断医师独立判断MB-MCA的存在,结果一致时确定为MB-MCA.测量MB长度、厚度,结果 用x±s表示.以每隔5%R-R间期为1个重建时相,观察并测量MCA在整个心动周期中管径的变化,探索管径最大和最小时的时相显示规律,计算MCA最大狭窄程度,应用Pearson相关统计分析狭窄程度与MB的长度及厚度之间的相关关系.结果 450例可疑CHD和体检者,冠状动脉CTA发现MB-MCA 163例(36.2%),192处.在选取的被心肌完全包绕或覆盖的30例MB-MCA中,MCA收缩期管径最小时出现于R-R间期30%～35%者27例(90.0%),MCA舒张期管径最大时出现于R-R间期70%～80%者27例(90.0%).统计学结果显示,MCA管腔狭窄程度与MB的厚度呈明显相关(r=0.675,P<0.01),而与MB的长度无明显相关性(r=0.096,P>0.05).结论 DSCT冠状动脉成像MCA管径最小和最大时一般分别出现于R-R间期30%～35%和70%～80%处;MCA收缩期狭窄程度与MB的厚度呈明显相关,而与MB的长度无明显相关.     

Quantification of left and right ventricular function and myocardial mass: comparison of low-radiation dose 2nd generation dual-source CT and cardiac MRI

Objective

To prospectively evaluate the accuracy of left and right ventricular function and myocardial mass measurements based on a dual-step, low radiation dose protocol with prospectively ECG-triggered 2nd generation dual-source CT (DSCT), using cardiac MRI (cMRI) as the reference standard.

Materials and methods

Twenty patients underwent 1.5 T cMRI and prospectively ECG-triggered dual-step pulsing cardiac DSCT. This image acquisition mode performs low-radiation (20% tube current) imaging over the majority of the cardiac cycle and applies full radiation only during a single adjustable phase. Full-radiation-phase images were used to assess cardiac morphology, while low-radiation-phase images were used to measure left and right ventricular function and mass. Quantitative CT measurements based on contiguous multiphase short-axis reconstructions from the axial CT data were compared with short-axis SSFP cardiac cine MRI. Contours were manually traced around the ventricular borders for calculation of left and right ventricular end-diastolic volume, end-systolic volume, stroke volume, ejection fraction and myocardial mass for both modalities. Statistical methods included independent t-tests, the Mann–Whitney U test, Pearson correlation statistics, and Bland–Altman analysis.

Results

All CT measurements of left and right ventricular function and mass correlated well with those from cMRI: for left/right end-diastolic volume r = 0.885/0.801, left/right end-systolic volume r = 0.947/0.879, left/right stroke volume r = 0.620/0.697, left/right ejection fraction r = 0.869/0.751, and left/right myocardial mass r = 0.959/0.702. Mean radiation dose was 6.2 ± 1.8 mSv.

Conclusions

Prospectively ECG-triggered, dual-step pulsing cardiac DSCT accurately quantifies left and right ventricular function and myocardial mass in comparison with cMRI with substantially lower radiation exposure than reported for traditional retrospective ECG-gating.     

64层螺旋CT对心肌桥与冠状动脉粥样硬化相关性的评价

目的：利用64层螺旋CT评价左冠状动脉前降支心肌桥（MB）与该支冠状动脉粥样硬化的相关关系。方法：连续收集300例因怀疑冠心病（CHD）而行64层螺旋CT冠状动脉血管成像（CTA）的病例的资料,由2名CT诊断医师独立判断并在结果一致时确定为前降支MB。将所有病例分为前降支MB组和非MB组,利用MPR、CPR、VR等后处理技术联合观察左冠状动脉前降支钙化及粥样硬化斑块的总体发生率,测量前降支由于斑块所致的狭窄率,比较MB组与非MB组的平均狭窄程度以及钙化、粥样硬化斑块的总体发生率。结果：在300例受检对象中冠状动脉CTA发现前降支MB74例（24.7%,74/300）。MB组与非MB组前降支钙化的发生率分别为36.5%与31.3%,粥样硬化斑块的发生率分别为54.1%与45.1%,MB组与非MB组的平均狭窄程度分别为48.4%与44.6%,两组之间钙化的发生率、粥样硬化斑块的发生率及平均狭窄程度差别均无明显统计学意义（P=0.40;P=0.18;P=0.97）。结论：左冠状动脉前降支MB对该支冠状动脉狭窄程度及粥样硬化斑块的总体发生率影响不明显。     

螺旋CT结合呼吸门控对矽肺形态与功能变化的研究

目的 探讨呼吸门控定量CT在评价矽肺形态与功能改变中的应用价值。方法 46例矽肺病人在50％肺活量（VC）状态下行全肺螺旋CT扫描，在20％VC、80％VC呼吸水平下于隆突层、隆突上、下各5cm处行高分辨率CT（HRCT）扫描。用Pulmo软件评估全肺各区间像素指数（PI），并与临床肺功能指标进行相关分析。结果 CT能清晰地显示矽肺的病变特征，HRCT能更好地显示肺间质病变。随着期别的增高，分布在＜－910HU（A区间，API）和＞－60HU（E区间，EPI）的PI增加（P＜0．05或P＜0．01）。API、EPI与第1秒用力呼气容积（FEV1．0）和VC呈中至高度相关（r=-0.801-0.690)。结论 呼吸门控定量CT能反映矽肺形态和功能异常的变化趋势，并有利于病变的追踪观察，为矽肺的研究提供了一种新的诊断方法。     

Optimization of image sampling rate to lower the radiation dose of dynamic myocardial CT perfusion

BackgroundDynamic myocardial CT perfusion (CTP) has emerged as a potential strategy to combine anatomical and functional evaluation in a single modality. However, this method results in a high radiation dose.MethodsDynamic CTP was performed in 56 patients with suspected or known ischemic heart disease of whom 48 had complete CT-data. Datasets with reduced sampling rate of 2- and 3 RR-intervals (2RR and 3RR) were constructed post hoc. Myocardial blood flow (MBF) estimates from the 2RR and 3RR datasets were compared with estimates based on the full dataset (1RR) using the two one-sided test of equivalence for paired samples.ResultsSignificant equivalence was found for rest MBF_LV (p ​< ​0.001), stress MBF_LV (p ​< ​0.001) and for the CFR_LV (p ​= ​0.005) when comparing 2RR blood flow estimates with the results based on the 1RR dataset. The 2RR reconstruction protocol led to an estimated reduction in radiation dose of 35.4 ​± ​3.8%.ConclusionMBF can be quantitated with dynamic CTP using a sampling strategy of one volume for every second heartbeat. This strategy could lead to a significant reduction in radiation dose.     

128层CT探讨心肌桥-壁冠状动脉与冠脉动脉粥样硬化的关系

目的:探讨心肌桥-壁冠状动脉(myocardiac bridge and mural coronary artery,MB-MCA)检出率及MB-MCA与动脉动脉粥样硬化的关系。方法:回顾性分析455例冠状动脉的MSCT资料。在薄层横断面图像基础上,主要通过分析CPR、VR图像判断MB-MCA。评估右冠状动脉、左前降支和左旋支3支的近、中、远段,以及MCA本身及其近、远侧段血管有无动脉粥样硬化钙化斑块、钙化积分评分、软斑块及其狭窄情况。结果:检出MB-MCA者的各支冠脉动脉粥样硬化钙化斑块和软斑块主要累及近段,较未检出MB-MCA者中段、远段增多且差异具有统计学意义(P均0.05)。MB近侧动脉粥样硬化斑块检出率显著多于MCA本身和其远侧(P0.001)。结论:MB-MCA并不会促进动脉粥样硬化的发生和进展,反而在某种程度上降低其发生的风险。     

Dual-isotope myocardial imaging: feasibility,advantages and limitations

Two hundred and thirty-one patients underwent dual-isotope myocardial imaging (rest thallium-201 followed by stress technetium-99m sestamibi). The feasibility of the procedure was excellent: camera scheduling flexibility was improved and the duration of the procedure was less than that of a classical stress-redistribution procedure. Interpretation of defects due to image attenuation was facilitated by the different attenuation properties of ²⁰¹Tl and ^99mTc-sestamibi in 11 of 19 patients. ²¹⁰Tl cross-over on ^99mTc was found to be 15% ± 3% with doses of ²⁰¹Tl and ^99mTc-sestamibi of 3 and 10 mCi, respectively, and 7% ± 2% with doses of 3 and 20 mCi. This protocol should preferentially be reserved for patients with a history of myocardial infarction and/or a basal left ventricular dysfunction, in whom assessment of myocardial viability is of major interest. Extensive clinical validation of the dual-isotope procedure is required and optimal acquisition and reconstruction parameters should be established.     

Acquired left coronary artery fistula draining to the cardiac vein system after acute myocardial infarction revealed by CT scan

Coronary artery fistula (CAF) is a congenital condition characterized by a pathological communication between a coronary artery and a systemic vein or one of the cardiac chambers. Iatrogenic CAFs were reported to develop secondary to the rupture of coronary aneurysm. Instances of acquired CAF draining into the cardiac chambers have been described after acute myocardial infarction. Angiography is the gold standard in diagnosing CAF. We describe the case of a patient who developed a fistula draining into the middle cardiac vein on the posterior interventricular sulcus, after acute myocardial infarction, revealed by CT scan.     

SPECT myocardial perfusion imaging in morbidly obese patients: Image quality, hemodynamic response to pharmacologic stress, and diagnostic and prognostic value

BACKGROUND: Obesity is a growing epidemic in the United States, and little is known about the characteristics of the morbidly obese population (body mass index [BMI] > or = 40 kg/m2) undergoing stress myocardial perfusion imaging (MPI). METHODS AND RESULTS: We retrospectively reviewed all consecutive morbidly obese patients without known coronary artery disease presenting for a clinically indicated technetium 99m (Tc-99m) gated stress single photon emission computed tomography imaging study over a 42-month period. Studies were analyzed for image quality, for the contribution of attenuation correction to image interpretation, and for the hemodynamic response to pharmacologic stress. In patients who subsequently had cardiac catheterization, the results were compared with those from the initial MPI study, and the Social Security Death Index and hospital medical records were searched to the assess survival rate in the entire cohort. A total of 433 patients were identified with a mean BMI of 47.3 +/- 8 kg/m2 and a mean Tc-99m stress dose of 35.6 +/- 5.4 mCi. Image quality was good in 61% of the patients, adequate in 37%, and poor in 2%. It was found to be dependent on the stressor used (better with exercise) but did not correlate with increasing weight or BMI. Attenuation correction was used in 95% of the studies reviewed and was helpful for image interpretation in 60%. The heart rate response to dipyridamole and adenosine was more pronounced and the blood pressure response to dipyridamole was less pronounced in morbidly obese patients compared with nonobese control patients. In the 43 patients who underwent catheterization, stress MPI had a sensitivity of 95% and negative predictive value of 80%. Kaplan-Meier survival analysis at 1 year showed a significant difference in survival rate of 98.3% for normal MPI studies and 94.0% for abnormal MPI studies (P = .02). CONCLUSION: Diagnostic-quality single photon emission computed tomography imaging is feasible in the majority (98%) of morbidly obese patients with the use of a dual-head camera, attenuation correction, and high stress Tc-99m tracer doses. Exercise stress was associated with better image quality. The prognostic value of a normal MPI study in this population appears to be less favorable than in non-morbidly obese patients.