(TRICKS) Time resolved imaging of contrast kinetics is a MRI technique, which increases the temporal resolution of dynamic contrast enhanced magnetic resonance angiography (CE-MRA) sequences. The K-space is divided into regions by increasing the sampling rate at the lower spatial frequencies and by reducing the sampling rate at the higher spatial frequencies. Since the time duration between two frames is shortened, it can be observed how frequently and how quickly the images are repeated at the exact same location.
TRICKS is particularly useful for dynamic vascular studies with high temporal resolution. TRICKS improves the calculation of the contrast bolus arrival and improves the characterization of arterio-venous malformations (AVMs).

See also Automatic Bolus Detection, MRA, Cardiac MRI.

A bolus is a rapid infusion of high dose contrast agent. Dynamic and accumulation phase imaging can be performed after bolus injection. Since the transit time of the bolus through the tissue is only a few seconds, high temporal resolution imaging can be required to obtain sequential images during the wash in and wash out of the contrast material and, therefore, resolve the first pass of the tracer.
For the same injected dose of contrast agent the injection rate (and, consequently, the total injected volume) modifies the bolus peak profile. Increasing the injection rate produces a sharpening of the peak (Cmax increase, Tmax decrease, peak length decrease). At a low injection rate, the first pass presents a plateau form. Substantial changes in the gadolinium concentrations during signal acquisition induce artifacts. Furthermore, the haemodynamic parameters (cardiac output, blood pressure) influence the bolus profile. The characteristics of gadolinium agents are favorable in the early bolus phase, whereas the advantages of large complexes (e.g. blood pool agents) and ultrasmall superparamagnetic iron oxide (USPIO) are most evident in the distribution phase.

(MR mammography) Magnetic resonance imaging of the breast is particularly useful in evaluation of newly diagnosed breast cancer, in women whose breast tissue is mammographically very dense and for screening in women with a high lifetime risk of breast cancer because of their family history or genetic disposition.
Breast MRI can be performed on all standard whole body magnets at a field strength of 0.5 T - 1.5 Tesla. Powerful gradient strengths over 15 mT/m will help to improve the balance between spatial resolution, scanning speed, and volume coverage. The use of a dedicated bilateral breast coil is obligatory.
Malignant lesions release angiogenic factors that increase local vessel density and vessel permeability. Breast cancer is detectable due to the strong enhancement in dynamic breast imaging that peaks early (about 1-2 min.) after contrast medium injection. If breast cancer is suspected, a breast biopsy may be necessary to secure the diagnosis.

See also Magnetic Resonance Imaging MRI, Biopsy and MR Guided Interventions.

Requirements in breast MRI procedures:
For Ultrasound Imaging (USI) see Breast Ultrasound at Medical-Ultrasound-Imaging.com.

See also the related poll result: 'MRI will have replaced 50% of x-ray exams by'

Cine sequences used in cardiovascular MRI are collection of images (usually at the same spatial location) covering of one full period of cardiac cycle or over several periods in order to obtain complete coverage.
The pulse sequence used, is either a standard gradient echo pulse sequence, a segmented data acquisition, a gradient echo EPI sequence or a gradient echo with balanced gradient waveform. In cardiac gating studies it is possible to assign consecutive lines either to different images, yielding a multiphase sequence with as many images as lines, or the lines are grouped together into segments and assigned to the same image. The overall time to acquire such a segment has to be small compared to the RR-interval of the cardiac cycle, i. e. 50 ms, and hence contains typically 8 to 16 image lines.
This strategy is called segmented data acquisition, and has the advantage of reducing overall imaging time for cardiac images so that they can be acquired within a breath hold, but obviously decreasing the temporal resolution of each individual image. This method shows dynamic processes, such as the ejection of blood out of the heart into the aorta, by means of fast imaging and displaying the resulting images in a sequential-loop, the impression of a real-time movie is generated. Ejection fractions and stroke volumes calculated from these cine MRI images in different cardiac axes have been shown to be more accurate than any other imaging modality.

See also Cardiac Gating.

A mathematical method for evaluating whether two features, i.e., ROI measurements obtained from a temporal series of images, share common characteristics and are therefore correlated.