Limits...
A review of 3D first-pass, whole-heart, myocardial perfusion cardiovascular magnetic resonance.

Fair MJ, Gatehouse PD, DiBella EV, Firmin DN - J Cardiovasc Magn Reson (2015)

Bottom Line: The mechanisms include rapid sequences, non-Cartesian k-space trajectories, reduced k-space acquisitions, parallel imaging reconstructions and compressed sensing.An attempt is made to explain, rather than simply state, the varying methods with the hope that it will give an appreciation of the different components making up a 3D FPP protocol.Basic estimates demonstrating the required total acceleration factors in typical 3D FPP cases are included, providing context for the extent that each acceleration method can contribute to the required imaging speed, as well as potential limitations in present 3D FPP literature.

View Article: PubMed Central - PubMed

Affiliation: National Heart & Lung Institute, Imperial College London, London, UK. M.Fair@rbht.nhs.uk.

ABSTRACT
A comprehensive review is undertaken of the methods available for 3D whole-heart first-pass perfusion (FPP) and their application to date, with particular focus on possible acceleration techniques. Following a summary of the parameters typically desired of 3D FPP methods, the review explains the mechanisms of key acceleration techniques and their potential use in FPP for attaining 3D acquisitions. The mechanisms include rapid sequences, non-Cartesian k-space trajectories, reduced k-space acquisitions, parallel imaging reconstructions and compressed sensing. An attempt is made to explain, rather than simply state, the varying methods with the hope that it will give an appreciation of the different components making up a 3D FPP protocol. Basic estimates demonstrating the required total acceleration factors in typical 3D FPP cases are included, providing context for the extent that each acceleration method can contribute to the required imaging speed, as well as potential limitations in present 3D FPP literature. Although many 3D FPP methods are too early in development for the type of clinical trials required to show any clear benefit over current 2D FPP methods, the review includes the small but growing quantity of clinical research work already using 3D FPP, alongside the more technical work. Broader challenges concerning FPP such as quantitative analysis are not covered, but challenges with particular impact on 3D FPP methods, particularly with regards to motion effects, are discussed along with anticipated future work in the field.

No MeSH data available.


Acquisition timings. Whilst conventional 2D multi-slice FPP is acquired throughout the cycle, typically starting in early systole (a), there are two popular options in 3D FPP. The 3D acquisition can be placed either in mid-systole (b) or mid-diastole (c), although the durations of these periods of minimal motion can be problematic (see text). Trigger delay (TD), saturation time (TS) and acquisition time (TA) are labelled for each in the first cardiac cycle
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC4522116&req=5

Fig1: Acquisition timings. Whilst conventional 2D multi-slice FPP is acquired throughout the cycle, typically starting in early systole (a), there are two popular options in 3D FPP. The 3D acquisition can be placed either in mid-systole (b) or mid-diastole (c), although the durations of these periods of minimal motion can be problematic (see text). Trigger delay (TD), saturation time (TS) and acquisition time (TA) are labelled for each in the first cardiac cycle

Mentions: Whilst the above timings already prevent a temporal resolution of one (or two) cardiac cycles, the cardiac motion itself further limits the acquisition “window” for FPP to either the mid-diastolic or end-systolic pause (Fig. 1). Although some formulations exist for predicting these pause times based on the R-R interval, generally in CMR it is best practice to measure them using cine imaging [17]. For 3D FPP, the end-systolic period has a benefit of the heart being contracted along its long-axis, therefore requiring a smaller 3D partition-direction field-of-view (FOV) which directly reduces the imaging time needed per image. In this phase the myocardium is also transmurally thicker, which has been shown to give greater visualisation of perfusion defects [18]. End-systolic imaging in healthy subjects has been shown in 3D FPP to produce image quality comparable to diastole [19]. The systolic pause is however very short, so a large number of 3D FPP acquisitions to date are acquired in the diastolic pause. During physiological or pharmacological stress both pauses become shorter, particularly at mid-diastole, and so potential acquisition windows are shortened further. Whilst 3D FPP work has a wide range of stated acquisition windows (Table 1), here an ideal time of less than 150 ms for the readout time is used in our estimates. With diastasis durations of ≤100 ms associated with HRs of ≥75 bpm [20], even 150 ms is a compromise towards the longer acquisition windows currently being reported in 3D FPP literature.Fig. 1


A review of 3D first-pass, whole-heart, myocardial perfusion cardiovascular magnetic resonance.

Fair MJ, Gatehouse PD, DiBella EV, Firmin DN - J Cardiovasc Magn Reson (2015)

Acquisition timings. Whilst conventional 2D multi-slice FPP is acquired throughout the cycle, typically starting in early systole (a), there are two popular options in 3D FPP. The 3D acquisition can be placed either in mid-systole (b) or mid-diastole (c), although the durations of these periods of minimal motion can be problematic (see text). Trigger delay (TD), saturation time (TS) and acquisition time (TA) are labelled for each in the first cardiac cycle
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4522116&req=5

Fig1: Acquisition timings. Whilst conventional 2D multi-slice FPP is acquired throughout the cycle, typically starting in early systole (a), there are two popular options in 3D FPP. The 3D acquisition can be placed either in mid-systole (b) or mid-diastole (c), although the durations of these periods of minimal motion can be problematic (see text). Trigger delay (TD), saturation time (TS) and acquisition time (TA) are labelled for each in the first cardiac cycle
Mentions: Whilst the above timings already prevent a temporal resolution of one (or two) cardiac cycles, the cardiac motion itself further limits the acquisition “window” for FPP to either the mid-diastolic or end-systolic pause (Fig. 1). Although some formulations exist for predicting these pause times based on the R-R interval, generally in CMR it is best practice to measure them using cine imaging [17]. For 3D FPP, the end-systolic period has a benefit of the heart being contracted along its long-axis, therefore requiring a smaller 3D partition-direction field-of-view (FOV) which directly reduces the imaging time needed per image. In this phase the myocardium is also transmurally thicker, which has been shown to give greater visualisation of perfusion defects [18]. End-systolic imaging in healthy subjects has been shown in 3D FPP to produce image quality comparable to diastole [19]. The systolic pause is however very short, so a large number of 3D FPP acquisitions to date are acquired in the diastolic pause. During physiological or pharmacological stress both pauses become shorter, particularly at mid-diastole, and so potential acquisition windows are shortened further. Whilst 3D FPP work has a wide range of stated acquisition windows (Table 1), here an ideal time of less than 150 ms for the readout time is used in our estimates. With diastasis durations of ≤100 ms associated with HRs of ≥75 bpm [20], even 150 ms is a compromise towards the longer acquisition windows currently being reported in 3D FPP literature.Fig. 1

Bottom Line: The mechanisms include rapid sequences, non-Cartesian k-space trajectories, reduced k-space acquisitions, parallel imaging reconstructions and compressed sensing.An attempt is made to explain, rather than simply state, the varying methods with the hope that it will give an appreciation of the different components making up a 3D FPP protocol.Basic estimates demonstrating the required total acceleration factors in typical 3D FPP cases are included, providing context for the extent that each acceleration method can contribute to the required imaging speed, as well as potential limitations in present 3D FPP literature.

View Article: PubMed Central - PubMed

Affiliation: National Heart & Lung Institute, Imperial College London, London, UK. M.Fair@rbht.nhs.uk.

ABSTRACT
A comprehensive review is undertaken of the methods available for 3D whole-heart first-pass perfusion (FPP) and their application to date, with particular focus on possible acceleration techniques. Following a summary of the parameters typically desired of 3D FPP methods, the review explains the mechanisms of key acceleration techniques and their potential use in FPP for attaining 3D acquisitions. The mechanisms include rapid sequences, non-Cartesian k-space trajectories, reduced k-space acquisitions, parallel imaging reconstructions and compressed sensing. An attempt is made to explain, rather than simply state, the varying methods with the hope that it will give an appreciation of the different components making up a 3D FPP protocol. Basic estimates demonstrating the required total acceleration factors in typical 3D FPP cases are included, providing context for the extent that each acceleration method can contribute to the required imaging speed, as well as potential limitations in present 3D FPP literature. Although many 3D FPP methods are too early in development for the type of clinical trials required to show any clear benefit over current 2D FPP methods, the review includes the small but growing quantity of clinical research work already using 3D FPP, alongside the more technical work. Broader challenges concerning FPP such as quantitative analysis are not covered, but challenges with particular impact on 3D FPP methods, particularly with regards to motion effects, are discussed along with anticipated future work in the field.

No MeSH data available.