Barbara Newby

Combined Assessment of Coronary Anatomy and Myocardial Perfusion Using Multidetector Computed Tomography for the Evaluation of Coronary Artery Disease

Multidetector computed tomography (MDCT) is increasingly used as an alternative to invasive coronary angiography. Although computed tomographic coronary angiography (CTCA) has been validated against invasive coronary angiography and nuclear myocardial perfusion imaging, the potential of MDCT to evaluate perfusion has not been fully explored. We sought to (1) develop a new technique for quantitative assessment of myocardial enhancement based on analysis of MDCT images acquired for CTCA, (2) identify the underlying causes of myocardial hypoenhancement detected by MDCT, and (3) determine the added diagnostic value of the MDCT perfusion index when combined with CTCA. We studied 84 patients undergoing clinical CTCA (64 patients with invasive coronary angiogram and a control group of 20 patients). MDCT perfusion index was calculated from x-ray attenuation measured in 16 myocardial segments. Hypoenhancement was automatically detected using comparisons with the normal range obtained in the control group, and its added value was determined against invasive coronary angiographic findings combined with known previous myocardial infarction. Myocardial hypoenhancement was detected in 29 of 64 patients in 47 vascular territories, of which 36 (77%) were abnormal by the reference technique. Of these 36 abnormalities, 10 (28%) were associated with previous myocardial infarction, whereas 26 (72%) corresponded to significant coronary stenosis. The addition of MDCT perfusion index to CTCA improved its diagnostic accuracy (sensitivity 0.87 to 0.96, accuracy 0.84 to 0.88, despite a decrease in specificity 0.79 to 0.68). In conclusion, myocardial hypoenhancement is a potentially valuable addition to MDCT evaluation of coronary artery disease without additional cost in radiation dose or contrast load.

Multidetector computed tomography evaluation of left ventricular volumes: sources of error and guidelines for their minimization.

BACKGROUND Although multidetector computed tomography (MDCT) is known to overestimate left ventricular (LV) end-systolic and end-diastolic volumes (ESV, EDV) compared to magnetic resonance imaging reference, the potential sources of error have not been thoroughly investigated. OBJECTIVES We sought to quantitatively assess the effects of the number of reconstructed phases and number of slices used for volume calculation on the accuracy of LV volume measurements. METHODS MDCT images obtained in 28 patients (Philips Brilliance 64) were reconstructed at 10, 20, 33, and 100 phases per cardiac cycle. For each number of phases, ESV was measured between aortic valve closure and mitral valve opening and normalized by reference ESV measured at 100 phases/R-R. Both reference ESV and EDV were measured using 20 and separately 10 fixed-thickness slices. Reproducibility was assessed using repeated measurements. RESULTS In 16 of 28 patients, the timing of end-systole varied with increasing number of reconstructed phases, resulting in a gradual decrease in ESV from 118 +/- 20% of reference ESV to 100 +/- 0%. Reduction in number of slices caused a significant increase in EDV and ESV (4.2 +/- 3.2% and 6.4 +/- 5.5%, respectively), roughly twice the corresponding intraobserver variability (2.5 +/- 1.5% and 3.8 +/- 2.4%). CONCLUSIONS Misidentification of end-systole due to insufficient number of reconstructed phases significantly affects ESV measurements. Also, the number of slices used for volume calculation affects both ESV and EDV beyond intermeasurement variability. To ensure accurate quantification of LV volumes, reconstruction at time intervals smaller than 5% of the RR-interval (>20 phases/cardiac cycles) and tracing endocardial borders in >10 slices are recommended.

Volumetric quantification of myocardial perfusion using analysis of multi-detector computed tomography 3D datasets: comparison with nuclear perfusion imaging

BackgroundAlthough the ability of multi-detector computed tomography (MDCT) to detect perfusion abnormalities associated with acute and chronic myocardial infarction (MI) has been demonstrated, this methodology is based on visual interpretation of selected 2D slices.ObjectivesWe sought to develop a new technique for quantitative volumetric analysis of myocardial perfusion from 3D datasets and test it against resting nuclear myocardial perfusion imaging (NMPI) reference.MethodsWe studied 44 patients undergoing CTCA: a control group of 15 patients and a study group of 29 patients. MDCT datasets acquired for CTCA were analyzed using custom software designed to: (1) generate bull’s eye display of myocardial perfusion and (2) calculate a quantitative index of extent and severity of perfusion abnormality, QH, for 16 volumetric myocardial segments. Visual interpretation of MDCT-derived bull’s eyes was compared with rest NMPI scores using kappa statistics of agreement on a coronary territory and patient basis. Quantitative MDCT perfusion data were correlated with rest NMPI summed scores and used for objective detection of perfusion defects.ResultsVisual analysis of MDCT-derived bull’s eyes accurately detected perfusion defects in agreement with NMPI (kappa = 0.70 by territory; 0.79 by patient). Quantitative data were in good agreement with NMPI, as reflected by: (1) correlation of 0.87 (territory) and 0.84 (patient) between summed QH and NMPI scores, (2) area under ROC curve 0.87 with sensitivity of 0.79–0.92, specificity 0.83–0.91, and accuracy 0.83–0.89 for objective detection of abnormalities.ConclusionsOur new technique for volumetric analysis of 3D MDCT images allows accurate objective detection of perfusion defects. This perfusion information can be obtained without additional radiation or contrast load, and may aid in elucidating the significance of coronary lesions.

Value of multidetector computed tomography evaluation of myocardial perfusion in the assessment of ischemic heart disease: comparison with nuclear perfusion imaging

MDCT-derived myocardial perfusion has not yet been validated against accepted standards. We developed a technique for quantification of myocardial perfusion from MDCT images and studied its diagnostic value against SPECT myocardial perfusion imaging (MPI). Ninety-eight patients were studied. Abnormal perfusion was detected by comparing normalized segmental x-ray attenuation against values obtained in 20 control subjects. Disagreement with resting MPI was investigated in relationship to MDCT image quality, severity of MPI abnormalities, and stress MPI findings. Resting MPI detected mild or worse abnormalities in 20/78 patients. MDCT detected abnormalities in 15/20 patients (sensitivity of 0.75). Most abnormalities missed by MDCT analysis were graded as mild on MPI. Additional abnormalities found in 16/78 patients were not confirmed on resting MPI (specificity of 0.72). However, 8 of these 16 apparently false positive MDCT perfusion tests had abnormal stress MPI; of these 8 patients, 7 had optimal MDCT image quality, while in 6/8 remaining patients, image quality was suboptimal. When compared with resting MPI, MDCT detected perfusion abnormalities with high accuracy. Moreover, half of MDCT perfusion abnormalities not confirmed by resting MPI were associated with abnormal stress MPI. Importantly, this information can be obtained without additional radiation dose or contrast agent.

Quantitative three-dimensional evaluation of myocardial perfusion during regadenoson stress using multidetector computed tomography.

Objective The ability of multidetector computed tomography (MDCT) to detect stress-induced myocardial perfusion abnormalities is of great clinical interest as a potential tool for the combined evaluation of coronary stenosis and its hemodynamic significance. We tested the hypothesis that quantitative 3-dimensional (3D) analysis of myocardial perfusion from MDCT images obtained during regadenoson stress would more accurately detect the presence of significant coronary artery disease (CAD) than identical analysis when performed on resting MDCT images. Methods We prospectively studied 50 consecutive patients referred for CT coronary angiography (CTCA) who agreed to undergo additional imaging with regadenoson (0.4 mg; Astellas). Images were acquired using prospective gating (256-channel; Philips). Custom analysis software was used to define 3D myocardial segments, and calculate for each segment an index of severity and extent of perfusion abnormality, Qh, which was compared with perfusion defects predicted by the presence and severity of coronary stenosis on CTCA. Results Three patients were excluded because of image artifacts. In the remaining 47 patients, CTCA depicted stenosis more than 50% in 23 patients in 37 of 141 coronary arteries. In segments supplied by the obstructed arteries, myocardial attenuation was slightly reduced compared with normally perfused segments at rest (mean [SD], 91 [21] vs 93 [26] Hounsfield units, not significant) and, to a larger extent, at peak stress (102 [21] vs 112 [20] Hounsfield units, P < 0.05). In contrast, index Qh was significantly increased at rest (0.40 [0.48] vs 0.26 [0.41], P < 0.05) and reached a nearly 3-fold difference at peak stress (0.66 [0.74] vs 0.28 [0.51], P < 0.05). The addition of regadenoson improved the diagnosis of CAD, as reflected by an increase in sensitivity (from 0.57 to 0.91) and improvement in accuracy (from 0.65 to 0.77). Conclusions Quantitative 3D analysis of MDCT images allows objective detection of CAD, the accuracy of which is improved by regadenoson stress.

3D ANALYSIS OF MYOCARDIAL PERFUSION FROM REGADENOSON STRESS COMPUTED TOMOGRAPHY: CAN ACCURACY BE IMPROVED BY ITERATIVE RECONSTRUCTION?

methods: We studied 34 consecutive patients referred for CT coronary angiography (CTCA) who agreed to undergo additional imaging with regadenoson (Astellas). Images were acquired using prospective gating (256-channel, Philips) and reconstructed using 2 different algorithms: filtered back-projection (FBP) and IR applied at the highest level (iDose7, Philips). Custom software was used to analyze both FBP and IR images. An index of severity and extent of perfusion abnormality was calculated for each 3D myocardial segment and compared to perfusion defects predicted by coronary stenosis >50% on CTCA.

Quantification of myocardial perfusion using multi-detector computed tomography: Validation against invasive coronary angiography

While CT coronary angiography (CTCA) has been validated, the potential of CT to evaluate perfusion has not been explored. We sought to: (1) develop and test a technique for quantitative assessment of myocardial perfusion from CT images, (2) identify the underlying causes of perfusion abnormalities detected by CT, (3) determine the added diagnostic value of CT perfusion. We studied 84 consecutive patients undergoing clinical CTCA. Accuracy of automated detection of perfusion abnormalities was determined against invasive coronary angiography findings combined with known prior myocardial infarction (MI). Perfusion abnormalities were detected in 29/64 patients in 47 vascular territories, of which 36 were confirmed as abnormal. Of these 36, 10 were associated with prior MI, while 26 corresponded to significant stenosis. The addition of perfusion to CTCA improved its diagnostic accuracy. In conclusion, myocardial perfusion is a potentially valuable addition to CT tools for the evaluation of coronary artery disease without additional cost in radiation dose or contrast load.