Magnetic resonance angiography of coronary arteries with a 3-dimensional magnetization-prepared true fast imaging with steady-state precession sequence compared with conventional coronary angiography

Left main coronary artery disease: A review of the spectrum of noninvasive diagnostic modalities

Medically managed significant left main (LM) stem disease has been considered a determinant of increased cardiac mortality approaching 50% at 3-year follow-up. Despite the clinical significance of LM disease, studies comparing the various diagnostic modalities, especially noninvasive, are sparse. Clinicians, particularly imagers, should be aware of the strengths and weaknesses of existing modalities to diagnose LM disease as integrating many clues (history, symptoms, electrocardiogram, and stress hemodynamics are essential to suspect this diagnosis and proceed to the next step). Here we review the existing data on the current role of electrocardiography, nuclear myocardial perfusion imaging (single photon emission computed tomography and positron emission tomography), stress echocardiography, cardiac computed tomography, and cardiac magnetic resonance imaging in diagnostic evaluation of LM disease. Wherever applicable we have extended our discussion to multivessel coronary artery disease encompassing scenarios where LMS can present as LM equivalent with or without extensive multivessel coronary artery disease.

Steady-state MR imaging sequences: physics, classification, and clinical applications

Steady-state sequences are a class of rapid magnetic resonance (MR) imaging techniques based on fast gradient-echo acquisitions in which both longitudinal magnetization (LM) and transverse magnetization (TM) are kept constant. Both LM and TM reach a nonzero steady state through the use of a repetition time that is shorter than the T2 relaxation time of tissue. When TM is maintained as multiple radiofrequency excitation pulses are applied, two types of signal are formed once steady state is reached: preexcitation signal (S-) from echo reformation; and postexcitation signal (S+), which consists of free induction decay. Depending on the signal sampled and used to form an image, steady-state sequences can be classified as (a) postexcitation refocused (only S+ is sampled), (b) preexcitation refocused (only S- is sampled), and (c) fully refocused (both S+ and S- are sampled) sequences. All tissues with a reasonably long T2 relaxation time will show additional signals due to various refocused echo paths. Steady-state sequences have revolutionized cardiac imaging and have become the standard for anatomic functional cardiac imaging and for the assessment of myocardial viability because of their good signal-to-noise ratio and contrast-to-noise ratio and increased speed of acquisition. They are also useful in abdominal and fetal imaging and hold promise for interventional MR imaging. Because steady-state sequences are now commonly used in MR imaging, radiologists will benefit from understanding the underlying physics, classification, and clinical applications of these sequences.

Three-dimensional cine imaging using variable-density spiral trajectories and SSFP with application to coronary artery angiography

A single breath-hold 3D cardiac phase resolved steady-state free precession (SSFP) sequence was developed, allowing 3D visualization of the moving coronary arteries. A 3D stack of spirals was acquired continuously throughout the cardiac cycle, and a sliding window reconstruction was used to achieve high temporal resolution. A coil specific field of view reconstruction technique was combined with Parallel Imaging with Localized Sensitivities (PILS) to allow acquisition of a reduced field of view. A view ordering incorporating fat suppression was employed to allow use of sliding window reconstruction. The technique was evaluated on healthy volunteers (n=8), yielding images with 102 ms temporal resolution and 1.35 mm in-plane resolution, and reasonable visualization of the left and right coronary arteries was achieved.

Noninvasive imaging for coronary artery disease: a technology assessment for the Medicare Coverage Advisory Commission

This report describes a review of the available scientific evidence through 2005 on direct noninvasive imaging tests (NITs) for coronary artery disease. In particular, the report addresses 6 key questions provided by the Agency for Healthcare Research and Quality and the Centers for Medicare and Medicaid Services. The questions examine the degree to which current evidence supports confident judgments about the use of NITs in the assessment of native coronary artery stenosis in clinical practice. The 2 NITs that are examined in detail in this report are 16 (and higher)-multidetector computed tomography angiography and 1.5-T magnetic resonance angiography to evaluate for stenosis in native coronary arteries. Reported sensitivity of NITs ranged from 68% to 100%; reported specificity ranged from 57% to 100% (patient-based analysis). Limitations include the exclusion of significant numbers of segments and patients, with often only the proximal coronary segments visualized. There is no direct evidence assessing the clinical use of NITs in terms of the incremental benefits or risks compared to alternative testing strategies. Although the ability of noninvasive direct coronary imaging technologies is promising-particularly the 64-multidetector computed tomography angiography-the evidence does not provide strong guidance on whether and how such technologies should be used in the population generally, or for Medicare beneficiaries specifically. Informed clinical and policy decision making will require further study of these technologies in well-characterized clinical contexts, in typical practice settings, and with attention to impact on management and health outcomes.