Accelerated 4D dobutamine stress MR imaging with k-t BLAST: feasibility and diagnostic performance

PURPOSE: To prospectively determine feasibility and diagnostic performance (with angiography as reference standard) of k-space and time (k-t) broad-use linear acquisition speed-up technique (k-t BLAST) cine imaging during dobutamine stress for identification of inducible cardiac wall motion abnormalities. MATERIALS AND METHODS: The study was conducted according to standards of the Charité and Virchow-Klinikum Ethics Committee. Patients gave written consent. Dobutamine stress magnetic resonance (MR) imaging was conducted in 65 patients (mean age, 63 years +/- 9 [standard deviation]; 49 men) with conventional cine steady-state free precession (SSFP). Accelerated four-dimensional (4D) k-t BLAST single-breath-hold imaging with complete left ventricular (LV) coverage was also performed at rest and during stress. For the cine SSFP and accelerated cine techniques, duration of imaging at rest and LV end-diastolic volume and ejection fraction were assessed. Segmental agreement for resting and inducible wall motion abnormalities was determined. In a subgroup (n = 40), direct comparison between SSFP and accelerated cine was performed for coronary stenosis detection. A paired Student t test was used to assess significance of continuous variables. Pearson correlation was used to test correlation between the techniques. Sensitivity, specificity, and diagnostic accuracy were calculated (standard definitions). For quantitative measurement of agreement, Cohen kappa was applied. RESULTS: For accelerated cine, imaging duration at rest was shortened by 40%. Correlations between cine SSFP and accelerated cine for LV parameters were 135 mL +/- 37 versus 129 mL +/- 31 (r = 0.89) for end-diastolic volume and 59% +/- 8 versus 58% +/- 7 (r = 0.95) for ejection fraction. kappa Values for segmental wall motion at rest and stress ranged from 0.77 to 0.91. Sensitivity, specificity, and diagnostic accuracy for coronary stenosis (>or=50%) detection based on arterial territory were 82%, 87%, and 86%, respectively, for cine SSFP and 82%, 86%, and 85%, respectively, for accelerated cine imaging. CONCLUSION: Accelerated 4D k-t BLAST wall motion imaging at rest and at dobutamine stress is rapid and feasible; LV measurements were nearly identical between the imaging approaches. Segmental wall motion analysis at rest and at stress show excellent agreement and reliable depiction of myocardial territories supplied by coronary arteries with 50% or more luminal narrowing.     

Assessment of left ventricular volumes and mass with fast 3D cine steady-state free precession k-t space broad-use linear acquisition speed-up technique (k-t BLAST)

PURPOSE: To compare left ventricular (LV) volume and mass assessment using two-dimensional (2D) cine steady-state free precession (SSFP) and k-t space broad-use linear acquisition speed-up technique (k-t BLAST) accelerated 3D magnetic resonance imaging (MRI). MATERIALS AND METHODS: On a commercially available 1.5T MR scanner, 2D cine SSFP, six- and eight-fold accelerated 3D k-t BLAST were performed to evaluate LV volumes and mass in 17 volunteers. After semiautomatic segmentation of the different MR data sets, the resulting volumes and mass were compared according to the mean difference, 95% confidence interval, standard deviation (SD), Pearson's correlation coefficient, Bland-Altman analysis, and the Pitman-Morgan test. RESULTS: Data acquisition was successful in all subjects. The number of required breathholds was reduced from a maximal of five for the 2D cine SSFP sequence to two for 3D k-t BLAST sequences. Comparing LV volumes, there was excellent agreement between 2D and 3D cine 8x k-t BLAST SSFP volumes (mean difference +/- 2SD end-diastolic volume [EDV] = 5 +/- 8 mL, end-systolic volume [ESV] = 1 +/-12 mL, and stroke volume [SV] = 3 +/- 8 mL), and mass (-1.8 +/- 9 g). CONCLUSION: k-t BLAST-accelerated 3D sequences allow accurate assessment of LV volumes and mass compared to 2D cine SSFP. This method may reduce costs and increase patient comfort due to shortened data acquisition time and reduced number of breathholds.     

Dynamic contrast-enhanced myocardial perfusion MRI accelerated with k-t sense.

In the k-t sensitivity encoding (k-t SENSE) method spatiotemporal data correlations are exploited to accelerate data acquisition in dynamic MRI studies. The present study demonstrates the feasibility of applying k-t SENSE to contrast-enhanced myocardial perfusion MRI and using the speed-up to increase spatial resolution. At a net acceleration factor of 3.9 (k-t factor of 5 with 11 training profiles) accurate representations of dynamic signal intensity (SI) changes were achieved in computer simulations. In vivo, 5x k-t SENSE was compared with 2x SENSE (identical acquisition parameters except for in-plane spatial resolution = 1.48 x 1.48 mm(2) vs. 2.64 x 2.64 mm(2), respectively). In 10 volunteers no differences in myocardial SI profiles were found (relative peak enhancement = 151% vs. 149.7%, maximal upslope = 12.9%/s vs. 13.3%/s for 2x SENSE and 5x k-t SENSE, respectively, all P > 0.05). Overall image quality was similar, but endocardial dark rim artifacts were reduced with k-t SENSE. Signal-to-noise ratio (SNR) in the myocardium was greater with 5x k-t SENSE by a factor of 1.36 +/- 0.23 at peak contrast enhancement with the relative yield decreasing with increasing dynamics in the object in accordance to theory. Higher nominal acceleration factors of up to 10-fold were shown to be feasible in computer simulations and in vivo.     

Fast dynamic contrast-enhanced lung MR imaging using k-t BLAST: a spatiotemporal perspective

Dynamic contrast-enhanced MR imaging has long been an attractive alternative to measure pulmonary perfusion as it offers simultaneous acquisition of high-resolution anatomical images and various functional information without exposing to ionizing radiation. As higher temporal resolution in addition to simultaneous acquisition of more slices from different positions favors more precise diagnosis, rapid acquisition of multiple images during bolus contrast administration remains essential to pulmonary perfusion imaging. Nevertheless, the branching morphology together with asynchronization of contrast-enhanced pulmonary perfusion scattered among distinct blood vessels imposes difficulties to faster imaging. This work demonstrates that k-t broad-use linear acquisition speed-up technique (k-t BLAST), having substantial performance on accelerating cardiac cine imaging, can be applied to accelerate dynamic contrast-enhanced lung imaging up to a factor of 5 with errors less than 6% on five healthy subjects and less than 10% on 13 patients, respectively, in the overall signal intensity. Perfusion parameter estimates show somewhat less errors than those in overall signal intensity. Results from healthy subjects and two groups of patients with various diseases show high consistency between fully sampled datasets and their accelerated counterparts. These suggest feasibility of accelerated contrast-enhanced lung images in clinical examinations and potential of extending k-t BLAST into related applications.     

Low-dose CT coronary angiography for the prediction of myocardial ischaemia

The purpose of this study was to prospectively determine the accuracy of low-dose computed tomography coronary angiography (CTCA) for the diagnosis of functionally relevant coronary artery disease (CAD) using cardiac magnetic resonance (CMR) as a standard of reference. Forty-one consecutive patients (age 64?±?10 years) underwent k-space and time broad-use linear acquisition speed-up technique accelerated CMR (1.5 T) and dual-source CTCA using prospective electrocardiography gating within 1 day. CTCA lesions were analysed and diameter stenoses of more than 50% and more than 75% were compared with CMR findings taken as the reference standard for assessing the functional relevance of CAD. CMR revealed perfusion defects in 21/41 patients (51%). A total of 569 coronary segments were analysed with low-dose CTCA. The image quality of low-dose CTCA was diagnostic in 566/569 segments (99.5%) in 39/41 patients (95%). Low-dose CTCA revealed stenoses of more than 50% in 58/123 coronary arteries (47.2%) in 24/41 patients (59%) and more than 75% stenoses in 46/123 coronary arteries (37.4%) in 23/41 patients (56%). Using a greater than 50% diameter stenosis, low-dose CTCA yielded the following per artery sensitivity, specificity, positive and negative predictive values, and accuracy for the detection of perfusion defects: 89%, 79%, 72%, 92% and 83%, respectively. Low-dose CTCA is reliable for ruling out functionally relevant CAD, but is a poor predictor of myocardial ischaemia.     

Feasibility of k-t BLAST technique for measuring "seven-dimensional" fluid flow

PURPOSE: To investigate the feasibility of rapid MR measurement of "seven-dimensional" (three velocity components, three dimensions, and time) fluid flow using the k-t Broad-use Linear Acquisition Speed-Up Technique (BLAST). MATERIALS AND METHODS: Complete k-space data were acquired for pulsatile fluid flow in a model of a stenosed carotid bifurcation. The data was subsampled to simulate "training" and "accelerated acquisition" data for reconstruction using k-t BLAST. RESULTS: Flow waveforms estimated from k-t BLAST reconstructions were in good agreement with those measured from the full data set for overall speedup factors up to approximately four times when slice-by-slice undersampling in k(y) was used. Accuracy was better than 25 mm/second or 7% (root-mean-square error) for individual time frames under these conditions. Flow patterns in the plane of symmetry, near the bifurcation, and in the stenosis were also in good agreement with those reconstructed from the full data set. Improved performance was obtained from undersampling in both k(y) and k(z), when acceleration factors up to 12 times gave acceptable results. CONCLUSION: The k-t BLAST technique can be applied to flow quantification, and may make feasible the acquisition of time-resolved blood flow from extended arterial regions within acceptable examination times.     

Accelerating cardiac cine 3D imaging using k-t BLAST.

By exploiting spatiotemporal correlations in cardiac acquisitions using k-t BLAST, gated cine 3D acquisitions of the heart were accelerated by a net factor of 4.3, making single breathhold acquisitions possible. Sparse sampling of k-t space along a sheared grid pattern was implemented into a cine 3D SSFP sequence. The acquisition of low-resolution training data, which was required to resolve aliasing in the k-t BLAST method, was either interleaved into the sampling process or obtained in a separate prescan to allow for shorter breathhold durations in patients with heart disease. Volumetric datasets covering the heart with 20 slices at a spatial resolution of 2 x 2 x 5 mm3 were recorded with 20 cardiac phases in a total breathhold duration of 25-27 sec, or 18 sec if partial Fourier sampling was additionally employed. The feasibility of the method was demonstrated on healthy volunteers and on patients. The comparison of endocardial area derived from single slices of the 3D dataset with values extracted from separate single-slice acquisitions showed no significant differences. By shortening the acquisition substantially, k-t BLAST may greatly facilitate volumetric imaging of the heart for evaluation of regional wall motion and the assessment of ventricular volume and ejection fraction.     

Accelerating cine phase-contrast flow measurements using k-t BLAST and k-t SENSE.

Conventional phase-contrast velocity mapping in the ascending aorta was combined with k-t BLAST and k-t SENSE. Up to 5.3-fold net acceleration was achieved, enabling single breath-hold acquisitions. A standard phase-contrast (PC) sequence with interleaved acquisition of the velocity-encoded segments was modified to collect data in 2 stages, a high-resolution under sampled and a low-resolution fully sampled training stage. In addition, a modification of the k-t reconstruction strategy was tested. This strategy, denoted as "plug-in," incorporates data acquired in the training stage into the final reconstruction for improved data consistency, similar to conventional keyhole. "k-t SENSE plug-in" was found to provide best image quality and most accurate flow quantification. For this strategy, at least 10 training profiles are required to yield accurate stroke volumes (relative deviation <5%) and good image quality. In vivo 2D cine velocity mapping was performed in 6 healthy volunteers with 30-32 cardiac phases (spatial resolution 1.3 x 1.3 x 8-10 mm(3), temporal resolution of 18-38 ms), yielding relative stroke volumes of 106 +/- 18% (mean +/- 2*SD) and 112 +/- 15% for 3.8 x and 5.3 x net accelerations, respectively. In summary, k-t BLAST and k-t SENSE are promising approaches that permit significant scan-time reduction in PC velocity mapping, thus making high-resolution breath-held flow quantification possible.     

k-t BLAST and k-t SENSE: dynamic MRI with high frame rate exploiting spatiotemporal correlations.

Dynamic images of natural objects exhibit significant correlations in k-space and time. Thus, it is feasible to acquire only a reduced amount of data and recover the missing portion afterwards. This leads to an improved temporal resolution, or an improved spatial resolution for a given amount of acquisition. Based on this approach, two methods were developed to significantly improve the performance of dynamic imaging, named k-t BLAST (Broad-use Linear Acquisition Speed-up Technique) and k-t SENSE (SENSitivity Encoding) for use with a single or multiple receiver coils, respectively. Signal correlations were learned from a small set of training data and the missing data were recovered using all available information in a consistent and integral manner. The general theory of k-t BLAST and k-t SENSE is applicable to arbitrary k-space trajectories, time-varying coil sensitivities, and under- and overdetermined reconstruction problems. Examples from ungated cardiac imaging demonstrate a 4-fold acceleration (voxel size 2.42 x 2.52 mm(2), 38.4 fps) with either one or six receiver coils. k-t BLAST and k-t SENSE are applicable to many areas, especially those exhibiting quasiperiodic motion, such as imaging of the heart, the lungs, the abdomen, and the brain under periodic stimulation.     

Optimizing spatiotemporal sampling for k-t BLAST and k-t SENSE: application to high-resolution real-time cardiac steady-state free precession.

In k-t BLAST and k-t SENSE, data acquisition is accelerated by sparsely sampling k-space over time. This undersampling in k-t space causes the object signals to be convolved with a point spread function in x-f space (x = spatial position, f = temporal frequency). The resulting aliasing is resolved by exploiting spatiotemporal correlations within the data. In general, reconstruction accuracy can be improved by controlling the k-t sampling pattern to minimize signal overlap in x-f space. In this work, we describe an approach to obtain generally favorable patterns for typical image series without specific knowledge of the image series itself. These optimized sampling patterns were applied to free-breathing, untriggered (i.e., real-time) cardiac imaging with steady-state free precession (SSFP). Eddy-current artifacts, which are otherwise increased drastically in SSFP by the undersampling, were minimized using alternating k-space sweeps. With the synergistic combination of the k-t approach with optimized sampling and SSFP with alternating k-space sweeps, it was possible to achieve a high signal-to-noise ratio, high contrast, and high spatiotemporal resolutions, while achieving substantial immunity against eddy currents. Cardiac images are shown, demonstrating excellent image quality and an in-plane resolution of approximately 2.0 mm at >25 frames/s, using one or more receiver coils.     

Automated quantitative Rb-82 3D PET/CT myocardial perfusion imaging: Normal limits and correlation with invasive coronary angiography

Background

We aimed to characterize normal limits and to determine the diagnostic accuracy for an automated quantification of 3D 82-Rubidium (Rb-82) PET/CT myocardial perfusion imaging (MPI).

Methods

We studied 125 consecutive patients undergoing Rb-82 PET/CT MPI, including patients with suspected coronary artery disease (CAD) and invasive coronary angiography, and 42 patients with a low likelihood (LLk) of CAD. Normal limits for perfusion and function were derived from LLk patients. QPET software was used to quantify perfusion abnormality at rest and stress expressed as total perfusion deficit (TPD).

Results

Relative perfusion databases did not differ in any of the 17 segments between males and females. The areas under the receiver operating characteristic curve for detection of CAD were 0.86 for identification of ??50% and ??70% stenosis. The sensitivity/specificity was 86%/86% for detecting ??50% stenosis and 93%/77% for ??70% stenosis, respectively. In regard to normal limits, mean rest and stress left ventricular ejection fraction (LVEF) were 67%?±?10% and 75%?±?9%, respectively. Mean transient ischemic dilation ratio was 1.06?±?0.14 and mean increase in LVEF with stress was 7.4%?±?6.1% (95th percentile of 0%).

Conclusion

Normal limits have been established for 3D Rb-82 PET/CT analysis with QPET software. Fully automated quantification of myocardial perfusion PET data shows high diagnostic accuracy for detecting obstructive CAD.     

Diagnostic performance of combined noninvasive coronary angiography and myocardial perfusion imaging using 320-MDCT: the CT angiography and perfusion methods of the CORE320 multicenter multinational diagnostic study

OBJECTIVE: Coronary MDCT angiography has been shown to be an accurate noninvasive tool for the diagnosis of obstructive coronary artery disease (CAD). Its sensitivity and negative predictive value for diagnosing percentage of stenosis are unsurpassed compared with those of other noninvasive testing methods. However, in its current form, it provides no information regarding the physiologic impact of CAD and is a poor predictor of myocardial ischemia. CORE320 is a multicenter multinational diagnostic study with the primary objective to evaluate the diagnostic accuracy of 320-MDCT for detecting coronary artery luminal stenosis and corresponding myocardial perfusion deficits in patients with suspected CAD compared with the reference standard of conventional coronary angiography and SPECT myocardial perfusion imaging. CONCLUSION: We aim to describe the CT acquisition, reconstruction, and analysis methods of the CORE320 study.     

Magnetic resonance myocardial first-pass perfusion imaging: parameter optimization for signal response and cardiac coverage.

Fast imaging techniques allow monitoring of contrast medium (CM) first-pass kinetics in a multislice mode. Employing shorter recovery times improves cardiac coverage during first-pass conditions, but potentially flattens signal response in the myocardium. The aim of this study was therefore to compare in patients with suspected coronary artery disease (CAD) two echo-planar imaging strategies yielding either extended cardiac coverage or optimized myocardial signal response (protocol A/B, six/four slices; preparation pulse, 60 degrees /90 degrees; delay time, 10/120 msec; readout flip angle, 10 degrees /50 degrees; respectively). In phantoms and myocardium of normal volunteers (N= 10) the CM-induced signal increase was 2.5-3 times higher with protocol B (P < 0.005) than with protocol A. For the detection of individually diseased coronary arteries (> or =1 stenosis with > or =50% diameter reduction on quantitative coronary angiography (QCA)), receiver-operator characteristics of protocol B (signal upslope in 32 sectors/heart) yielded a sensitivity/specificity of 82%/73%, which was superior to protocol A (P < 0.05, N= 14). For the overall detection of CAD, the sensitivity/specificity of protocol B was 85%/81%. An adequate signal response in the myocardium is crucial for a reliable detection of perfusion deficits during first-pass conditions. The presented protocol B detects CAD with a sensitivity and specificity similar to scintigraphic techniques.     

Single-breathhold four-dimensional assessment of left ventricular volumes and function using k-t BLAST after application of extracellular contrast agent at 3 Tesla

PURPOSE: To prospectively determine the feasibility and accuracy of a four-dimensional (4D) k-space over time broad-use linear acquisition speed-up technique (k-t BLAST) for the evaluation of left ventricular (LV) volumes in comparison to standard multiple-breathhold cine imaging, using a 3.0 Tesla (3T) MR system. MATERIALS AND METHODS: In 23 subjects, short-axis cine loops completely covering the LV were acquired using conventional turbo gradient echo (GRE) imaging. Immediately after administration of gadobenate dimeglumine, a rapid single-breathhold k-t BLAST 4D dataset with the same coverage was acquired and reconstructed to short-axis views. Quantitative aortic flow measurement for LV stroke volume (LVSV) was used to calibrate both techniques. For GRE and k-t BLAST cine imaging: LV volumes, ejection fraction (EF), and blood-to-myocardium-contrast (BMC) were determined. RESULTS: k-t BLAST and GRE sequences showed a strong correlation for LV volumes and EF (r = 0.97-0.99; P < 0.001). Excellent agreement was also found between the LVSV determined by aortic flow measurements and LVSV assessed using GRE sequence and k-t BLAST sequence. BMC of GRE was similar to that of k-t BLAST cine imaging. CONCLUSION: The use of the single-breathhold 4D k-t BLAST technique for the assessment of LV volume is feasible and accurate in 3T MRI.     

Diagnostic accuracy of stress myocardial perfusion MRI and late gadolinium-enhanced MRI for detecting flow-limiting coronary artery disease: a multicenter study

The aim of this study was to determine the diagnostic performance of stress and rest perfusion magnetic resonance imaging (MRI) and late gadolinium-enhanced (LGE) MRI for identifying patients with obstructive coronary artery disease (CAD). A total of 50 patients with suspected CAD underwent stress-rest perfusion MRI, followed by LGE MRI with a 1.5-T system. Stress-rest perfusion MRI resulted in an area under the receiver-operating characteristic curve (AUC) of 0.92 for observer 1 and 0.84 for observer 2 with sensitivity and specificity of 89% (32/36) and 79% (11/14) by observer 1, 83% (30/36) and 71% (10/14) by observer 2, respectively, showing a moderate interobserver agreement (Cohen’s κ = 0.49). While combination of stress-rest perfusion and LGE MRI did not result in improved accuracy for the prediction of flow-limiting obstructive CAD (AUC 0.81 for observer 1 and 0.80 for observer 2), the sensitivity was increased to 92% in both observers with a substantial interobserver agreement (κ = 0.70). Stress-rest myocardial perfusion MRI is an accurate diagnostic test for identifying patients with obstructive CAD.     

Diagnostic performance of an expert system for the interpretation of myocardial perfusion SPECT studies.

An expert system (PERFEX) developed for the computer-assisted interpretation of myocardial perfusion SPECT studies is now becoming widely available. To date, a systematic validation of the diagnostic performance of this expert system for the interpretation of myocardial perfusion SPECT studies has not been reported. METHODS: To validate PERFEX's ability to detect and locate coronary artery disease (CAD), we analyzed 655 stress/rest myocardial perfusion prospective SPECT studies in patients who also underwent coronary angiography. The patient population comprised CAD patients (n = 480) and healthy volunteers (n = 175) (449 men, 206 women). Data from 461 other patient studies were used to implement and refine 253 heuristic rules that best correlated the presence and location of left ventricular myocardial perfusion defects on SPECT studies with angiographically detected CAD and with human expert visual interpretations. Myocardial perfusion defects were automatically identified as segments with counts below sex-matched normal limits. PERFEX uses the certainty of the location, size, shape, and reversibility of the perfusion defects to infer the certainty of the presence and location of CAD. The visual interpretations of tomograms and polar maps, vessel stenosis from coronary angiography, and PERFEX interpretations were all accessed automatically from databases and were used to automatically generate comparisons between diagnostic approaches. RESULTS: Using the physician's reading as a gold standard, PERFEX's sensitivity and specificity levels for detection and localization of disease were, respectively, 83% and 73% for CAD, 76% and 66% for the left anterior descending artery, 90% and 70% for the left circumflex artery, and 74% and 79% for the right coronary artery. These results were extracted from a receiver operating characteristic curve using the average optimal input certainty factor. CONCLUSION: This study shows that the diagnostic performance of PERFEX for interpreting myocardial perfusion SPECT studies is comparable with that of nuclear medicine experts in detecting and locating CAD.     

Clinical significance of myocardial perfusion abnormalities in patients with varying degree of coronary artery stenosis

OBJECTIVES: (1) To identify myocardial perfusion abnormalities in a cohort of patients having coronary artery disease (CAD) risk factors, with either suspected or clinical evidence of ischaemic heart disease (IHD), and with varying degree of coronary artery stenosis. (2) To evaluate the clinical significance of the extent and severity of perfusion abnormalities assessed by myocardial perfusion scintigraphy (MPS) in relation to the anatomical location of coronary stenosis demonstrated by five-vessel selective coronary angiography (SCA). METHODS: One hundred and thirty-eight patients (106 male, 32 female) with suspected or clinical evidence of IHD underwent diagnostic evaluation at the Central Hospital of Nicosia, between November 2002 and August 2003. The diagnostic work-up included clinical examination, exercise tolerance test, SCA and myocardial perfusion scintigraphy (MPS) using either Tl chloride or Tc-tetrofosmin. RESULTS: Based on the results of SCA, patients were divided into five groups on the basis of stenosis as cross-sectional area of coronary artery lumen and its haemodynamic significance, ranging from group 1=less than 50% coronary stenosis to group 5=100% stenosis (occlusion). Nine of 11 (40.9%) patients with angiographically normal coronary arteries (group 1) had moderate inducible reversible ischaemia on MPS and 9/47 (19.1%) patients with insignificant coronary stenosis (less than 75% stenosis=group 2) had fixed perfusion defects, compatible with previous myocardial infarction. The extent of perfusion abnormalities in post-stress MPS patients from group 2 was not found to be statistically significant (P>0.05) when compared to patients belonging to groups 3, 4 and 5. However, the extent of perfusion abnormalities between patients from group 2, when compared to groups 3, 4 and 5 demonstrated significant statistical difference (P<0.05) on post-rest MPS studies. Furthermore, there was no significant statistical correlation between anatomical location of coronary stenosis and severity of perfusion abnormalities in the corresponding myocardial segments. CONCLUSION: Patients with CAD risk factors, and coronary arteries with insignificant stenosis on angiography, may demonstrate inducible reversible myocardial ischaemia. This is suggestive of coronary endothelial dysfunction. Patients with insignificant coronary artery stenosis and no previous history of adverse coronary events may demonstrate features of previous myocardial infarction on MPS. The severity of perfusion defects demonstrated by MPS may be independent of the anatomical location of coronary artery stenosis.     

A direct comparison of the sensitivity of CT and MR cardiac perfusion using a myocardial perfusion phantom

BackgroundDirect comparison of CT and magnetic resonance (MR) perfusion techniques has been limited and in vivo assessment is affected by physiological variability, timing of image acquisition, and parameter selection.ObjectiveWe precisely compared high-resolution k-t SENSE MR cardiac perfusion at 3 T with single-phase CT perfusion (CTP) under identical imaging conditions.MethodsWe used a customized MR imaging and CT compatible dynamic myocardial perfusion phantom to represent the human circulation. CT perfusion studies were performed with a Philips iCT (256 slice) CT, with isotropic resolution of 0.6 mm³. MR perfusion was performed with k-t SENSE acceleration at 3 T and spatial resolution of 1.2 × 1.2 × 10 mm. The image contrast between normal and underperfused myocardial compartments was quantified at various perfusion and photon energy settings. Noise estimates were based on published clinical data.ResultsContrast by CTP highly depends on photon energy and also timing of imaging within the myocardial perfusion upslope. For an identical myocardial perfusion deficit, the native image contrast-to-noise ratio (CNR) generated by CT and MR are similar. If slice averaging is used, the CNR of a perfusion deficit is expected to be greater for CTP than MR perfusion (MRP). Perfect timing during single time point CTP imaging is difficult to achieve, and CNR by CT decreases by 24%–31% two seconds from the optimal imaging time point. Although single-phase CT perfusion offers higher spatial resolution, MRP allows multiple time point sampling and quantitative analysis.ConclusionThe ability of CTP and current optimal MRP techniques to detect simulated myocardial perfusion deficits is similar.     

~(99m)Tc-MIBI潘生丁负荷心肌灌注断层显像评价冠状动脉支架术后血管再狭窄的价值

目的: 通过对冠状动脉(简称冠脉)支架植入前后进行静息和潘生丁负荷99mTc-MIBI断层显像(R-MPTI、P-MPTI),以了解SPECT在支架置入术前筛选、术后再狭窄评价中的价值.材料和方法: 95例冠心病患者在冠状动脉介入治疗前、术后3～6个月行R-MPTI和P-MPTI.潘生丁最大剂量时注射740MBq99mTc-MIBI,1h后行心肌断层显象;24h后重复静态心肌显象.与术后复查冠脉造影(CAG)对比,分析心肌灌注显像对支架术后再狭窄的诊断效果.结果: 95例冠心病患者共有855个心肌血流灌注节段,术前R-MPTI发现196个心肌血流灌注缺损,P-MPTI发现351个.支架置入后R-MPTI检查发现62个心肌血流灌注缺损病变节段,P-MPTI检查发现145个心肌血流灌注缺损病变节段.术后CAG随访92例,18例(18/92,19.6%)共29支血管发生再狭窄.按再狭窄冠脉支数计算,R-MPTI、P-MPTI对再狭窄的诊断准确性、阳性预测值和阴性预测值分别为84.5%、92.6%; 59.5%、75.7%;95.7%、98.9%,所有指标均有显著差异(χ~2＝15.54)(P<0.01).结论: P-MPTI可以早期发现冠状动脉内支架术后再狭窄,诊断效率高于R-MPTI,有利于准确判断病情和指导治疗.     

A comparative regional analysis of coronary atherosclerosis and calcium score on multislice CT versus myocardial perfusion on SPECT.

For the noninvasive evaluation of coronary artery disease (CAD), both multislice CT and gated SPECT are available. How these 2 modalities relate, however, is yet unclear. The purpose of this study was to perform a head-to-head comparison of the results of multislice CT and gated SPECT on a regional basis (per vessel distribution territory) in patients with known or suspected CAD. METHODS: One hundred forty patients underwent both multislice CT for coronary calcium scoring and coronary angiography and gated SPECT for myocardial perfusion imaging. The coronary calcium score was determined for each coronary artery. Coronary arteries on multislice CT angiography were classified as having no CAD, insignificant stenosis (<50% luminal narrowing), significant stenosis, or total or subtotal occlusion (>/=90% luminal narrowing). Gated SPECT findings were classified as normal or abnormal (reversible or fixed defects) and were allocated to the territory of one of the various coronary arteries. RESULTS: In coronary arteries with a calcium score of 10 or less, the corresponding myocardial perfusion was normal in 87% (n = 194/224). In coronary arteries with extensive calcifications (score > 400), the percentage of vascular territories with normal myocardial perfusion was lower, 54% (n = 13/24). Similarly, in most of the normal coronary arteries on multislice CT angiography, the corresponding myocardial perfusion was normal on SPECT (156/175, or 89%). In contrast, the percentage of normal SPECT findings was significantly lower in coronary arteries with obstructive lesions (59%) or with total or subtotal occlusions (8%) (P < 0.01). Nonetheless, only 48% of vascular territories with normal perfusion corresponded to normal coronary arteries on multislice CT angiography, whereas insignificant and significant stenoses were present in, respectively, 40% and 12% of corresponding coronary arteries. CONCLUSION: Although a relationship exists between the severity of CAD on multislice CT and myocardial perfusion abnormalities on SPECT, analysis on a regional basis showed only moderate agreement between observed atherosclerosis and abnormal perfusion. Accordingly, multislice CT and gated SPECT provide complementary rather than overlapping information, and further studies should address how these 2 modalities can be integrated to optimize patient management.