Evaluating Coronary Atherosclerosis On 64-Slice Spiral CT And MR Angiography

Part One Evaluating Coronary Artery Lumen with Calcified Plaque on CTA: Comparison with Coronary AngiographyObjective: To evaluate the relationship between Coronary artery stenosis and the size, shape and the calcium score of coronary calcified plaques detected by CTA comparing with CAG lesion to lesion, to improve diagnostic accuracy for coronary stenosis caused by calcified plaque on CTA.Materials and Methods: 43 consecutive patients (37 men; age 66.9±11.7 years) with coronary calcified plaques detected on CTA were included in the study. CTA was performed on Siemens sensation cardiac 64 spiral CT scanner with 0.33s/r, 120kV, eff.900 mAs, slice collimation 64×0.6mm, pitch 0.2, thickness 0.75mm, increment 0.5mm. Contrast media (Ultruvist 370mgI/ml) was injected with 5.0ml/s rate. The image postprocessing included MIP, MPR, coronary tree VR and calcium score. The numbers and the total calcium score of coronary calcified plaques of every patient were calculated. 117 calcified plaques (located in the coronary segment > 1.5mm in diameter and the size can be measured) were studied comparing with CAG lesion to lesion. To evaluate the correlation between the coronary stenosis with calcified plaque and the risk factors of coronary artery disease. To evaluate the shape and the distribution of calcified plaques. The length, width, volume, calcium score and the coronary stenosis with calcified plaque were measured on CTA. The diagnostic accuracy for coronary stenosis with calcified plaque on CTA was calculated. All the patients were performed CAG within two weeks after CTA. The stenosis (>50 % was defined significant stenosis) was also evaluated on CAG lesion to lesion. Statistic analysis included correlation analysis,chi-square test and t test.Results: 29 (of 117) calcified plaques caused significant coronary stenosis on CAG. There was correlation between coronary stenosis with calcified plaque and hypercholesteremia (p<0.05). The coronary stenosis with calcified plaque on CTA was more severe than that on CAG (57%±23.1% vs. 26%±28.9%, p<0.05). The sensitivity, specificity, positive predictive value, negative predictive value and the accuracy of diagnosis of significant coronary stenosis with calcified plaque on CTA was 86.2 % , 44.3 % , 33.8 % , 90.7 % and 54.7% respectively. The frequency of coronary significant stenosis in group of arch or circular calcified plaques was higher than that in group of spotted plaques from cross section image on CTA (58.3% vs. 16.1%, p<0.05). The length, width and the volume of calcified plaque in group of significant stenosis were more than that in group of <50% stenosis (p<0.05). There was no correlation between coronary stenosis with calcified plaque and the distribution of calcified plaque. There was no correlation between The numbers of significant coronary stenosis with calcified plaques and the numbers, volume and total calcium score of the calcified plaques ( p>0.05). Conclusions: There was correlation between coronary stenosis with calcified plaque and hypercholesteremia. The frequency of coronary significant stenosis in group of arch or circular calcified plaques was higher than that in group of spotted plaques from cross section image on CTA. Significant coronary artery stenosis is more frequent in those patients with multiple lesions, large volume and high calcium score of coronary calcified plaque. Calcified plaque with large size may cause significant coronary artery stenosis. CTA overestimates the coronary stenosis with calcified plaque. CTA showed high sensitivity and negative predictive value and low specificity, positive predictive value and accuracy of diagnosis of significant coronary stenosis with calcified plaque.Part Two Evaluating Coronary Artery stenosis with Calcified Plaque on64-slice Spiral CT and Coronary MR AngiographyObjective: To compare the diagnostic accuracy of CMRA with 64-slice spiral CT for coronary stenosis with calcified plaque.Materials and Methods: Consecutive 24 patients with various extent calcified atherosclerotic plaques on CTA were included in the CMRA study. CAG was performed within 1 week after CTA and CMRA. Siemens Sensation Cardiac 64 CT scanner was used with 120kV, 900mAs, 0.4 × 0.4 × 0.4mm spatial resolution, 0.75mm thickness and 0.5mm increment. The contrast media was injected at a rate of 5ml/s (Ultravist 370mgl/ml). The image post processing included MIP, MPR and coronary tree VR. The CMRA was acquired with GE Signa 1.5T HD scanner using navigator-gated 3D-SSFP sequence with a slab of 16-partition and a resolution of 1.1 × 1.1 × 2mm. T2-preparation was applied to suppress the myocardium. The coronary tree was visualized in multiple target slabs. During CTA and CMRA, the heart rate was controlled to be <70bpm. The CTA and CMRA data were graded for the presence of greater than 50% stenosis in vessels larger than 1.5 mm in diameter, and the images were reviewed by two radiologists. The diagnostic accuracies of the two modalities were evaluated with reference to quantitative CAG using the chi square test.Results: Totally 155 calcified atherosclerotic plaques could be detected on 85 segments. 118 calcified plaques ( of 155 ) were judged as significant stenosis. But on CAG, only 63 of the 118 plaques caused significant stenosis. Compared to CAG, the sensitivity, specificity and accuracy of CTA detecting significant stenosis with calcified plaque was 89%, 33%, 55%, respectively. On CMRA, 62 (of 155) calcified plaques corresponding coronary segments were judged significant stenosis and 52 (of 62) were consistent with CAG The sensitivity, specificity and accuracy of CMRA detecting significant stenosis with calcifiedplaque was 83%, 89%, 86%, respectively. On diagnosing coronary stenosis with calcified plaque, both CTA and CMRA had high sensitivities (p>0.05), the specificity of CMRA was significantly higher than that of CTA (P<0.05). The overall diagnostic accuracy of CMRA for coronary significant stenosis with calcified plaque was significantly higher than that of CTA (P<0.05). Conclusions: CMRA had significantly higher specificity than CTA for diagnosing coronary artery stenosis with calcified plaque, and both of the two modalities had high sensitivities for detection of significant stenosis with calcified plaque. The overall diagnostic accuracy of CMRA was significantly higher than that of CTA.Part ThreeEvaluating Coronary Atherosclerotic Plaque and Stenosis on CoronaryMR Angiography with and without Contrast ApplicationObjective: To improve the SNR and CNR of coronary artery angiography images by contrast enhancement. To compare the diagnostic accuracy of CMRA with and without contrast enhancement for coronary atherosclerotic plaques and stenosis. Materials and Methods: 14 healthy human volunteers(mean age 44.1, 8 males) and 20 consecutive patients (mean age 57.3, 14males) with coronary non-calcified plaque detected by CTA were enrolled in pre- and post contrast CMRA studies. CMRA was performed within one week after CTA. Pre- and post-contrast CMRA were performed with navigator-gated 3D-SSFP sequence with TR 4.7ms, TE 2.3ms(post-contrast CMRA, TR 4.9ms, TE 2.1ms), Flip angle 65, FOV 28cm×28cm, Matrix 256×256 (post-contrast CMRA, 320×256), thickness 2mm, a slab of 16-partition and a resolution in-plane of 1.1×1.1mm(post-contrast CMRA, 0.9×1.1mm). T2-preparation was applied to suppress the myocardium. Gadolinium-DTPA 20ml was intravenously injected (Magnevist, a injection rate of 1.5ml/s ) using automatic injector. The coronary tree was visualized in multiple target slabs. During CMRA, the heart rate was controlled to be <70bpm. CMRA images were graded the significant stenosis in coronary stenosis>50% in segments > 1.5mm in diameter. SNR and CNR (blood versus thoracic muscle) of pre- and post-contrast CMRA were measured and compared both in healthy human volunteers and in patients with coronary artery disease. The noncalcified plaques and the mixed type plaques with main noncalcified component were included in the study. To compare the detection rates of atherosclerotic plaques and coronary stenosis between pre- and post-contrast CMRA, and the CNRs between the plaque and the surrounding connective tissue and the coronary lumen were also compared. The coordination between the diagnostic accuracy for coronary stenosis of pre- and post-contrast CMRA was analysed with reference standard ofCTA. SPSS11.5 soft ware was used to statistic analyze. MRA data were double-blind reviewed by two radiologists.Results: The mean SNR of blood and the CNRof post-contrast CMRA showed significantly higher than that of pre-contrast CMRA both in healthy volunteers and patients. The detection rate for atherosclerotic plaque of post-contrast CMRA was significant higher than that of pre-contrast CMRA (96.8% vs. 32.3%, p < 0.05). Comparison with pre-contrast CMRA, post-contrast CMRA improved the CNRs between the plaque and the surrounding connective tissue and the coronary lumen (9.81±4.6 vs. 95.62±6.61, 12.54±5.5 vs 8.79±6.63, p < 0.05). The detection rate for coronary stenosis of post-contrast CMRA was higher than that of pre-contrast CMRA (100%, 77.4%). The coincidence of diagnosing significant coronary stenosis on pre- and post-contrast MRA was 0.742 (P<0.05). Conclusions: Post-contrast CMRA improving the SNR and CNR of coronary artery images, and improving the CNRs between the plaque and the surrounding connective tissue and the coronary lumen. Post-contrast CMRA improved the detection rate of atherosclerotic plaques and coronary stenosis, but didn't improve the diagnostic accuracy of coronary artery significant stenosis.