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To investigate blood flow in head and neck arteries by phase contrast MRI1MAXILLOFACIAL SURGERY, EA Chimere 7516, AMIENS, France, 2MAXILLOFACIAL SURGERY, FACING FACES INSTITUTE, AMIENS, France, 3BIO FLOW IMAGE, EA Chimere 7516, AMIENS, France
Synopsis
The 2D-cine PC MRI allows to know precisely the
arterial flow in small vessels but it is unsuited for clinical use. The
principal aim of this study was to determine the precision loss when rapid monophasic PC sequences (whiches are not synchronised with cardiac cycle) are
used compared to the traditional 2D-cine sequences in ten healthy volunteers. Pearson’s
coefficient between the two technics was determined and Bland Altman tests were
used. The precision loss was between 0,55 % et 27 %, depending on the studied
vessel, so the monophasic PC sequences can be used for clinical vascular evaluation in
pretherapeutic conditions.
INTRODUCTION
The measure of arterial blood flow of internal carotid artery (ICA), external carotid artery (ECA), vertebral artery (VA), superior thyroid artery (SThA), lingual artery (LA), internal maxillary artery (IMA) and superficial temporal artery (STA) is necessary in clinical practice in maxillo-facial surgery. Phase-contrast MRI gets around the echo-Doppler limits by allowing a precise and reproducible measure of the flow [2] [3] in small vessels. These sequences are synchronized with the cardiac cycle and take in average 3 minutes per artery, what it is unsuited in clinical practice. Monophasic sequences average the blood flow during the cardiac cycle, with an acquisition time of a few seconds, without synchronization, but at a price in precision loss. Our main objective of was to evaluate the precision loss of monophasic PC acquisitions with a traditional 2D-cine PC acquisition.
MATERIELS, METHODS AND POPULATION
It is a monocentric trial, on 10 healthy volunteers, without any cardiovascular pathology or cervico-facial surgery. The phase-contrast sequences were performed on a 3 Tesla MRI (Achieva Dxstream, Philips) with a 32 elements head coil. A pulse sensor was used for the 2D-cine PC sequences. The 3D PCA acquisition were performed for finding the arteries of interest (ICA, ECA, SThA, LA, FA, IMA, TA) on both sides. The cutting planes were placed perpendicularly to the axis of the vessel by operator, on two orthogonal cross-sections. The appropriate encoding velocity for each vessel was used. Were then performed: a 2D-cine PC synchronized with the cardiac cycle of the subject, then 4 monophasic sequences performed without synchronisation. The acquisition parameters are presented in Figure 1. The comparison of surface, velocity and flow values was performed between the mean value obtained from 32 phases of cardiac cycle during the 2D-cine PC acquisition and the mean value of the 4 monophasic acquisitions. The Pearson’s coefficient and Bland Altman tests were used to compare the two technics. The repeatability of monophasic PC sequences was determined by the mean and the standard deviations of the 4 sequences. The homogeneity was defined as the standard deviation / mean ratio for each artery.RESULTS
97 2D-cine PC and 388 monophasic PC sequences were done for a total of 158 analysed arteries: 20 ICA, 19 ECA, 20 VA, 19 TA, 21 IMA, 25 FA, 26 LA, 8 SThA. An artery could be analysed twice if the section of this artery was perpendicular twice. The correlations between 2D-cine PC sequences and monophasic sequences for the surface, velocity, flow are presented in Figure 2. For example, the linear correlations for arteries with flow values more or less than 100 ml/min are presented in Figure 3. On the Bland Altman graphics, the means of differences between 2D-cine PC and monophasic sequences were between 0,4%(ICA) and 3,8% (VA) for surfaces, 0,9% (VA) and16,7 % (SThA) for velocities and 1% (LA) and 9,3% (IMA) for flow values. The limits of agreement were from 11,3 % (VA) to 61,1% (SThA) for surfaces, from 14, 3% (ECA) to 81,8% (SThA) for velocities and from 9,4% (ICA) to 45% (LA) for flow values. 95% of values were in the limits of agreement, except for ICA (5%) and FA (8%) surface measurements, ICA (10%) velocity measurement and LA (11,5%) flow measurements. The repeatability for flow values of the monophasic acquisitions is presented in Figure 4, the homogeneity for all values in Figure 5. The total duration of acquisition is reduced from 37 minutes to 10 minutes and 10 seconds, a decrease of 70 %.DISCUSSION
The low number of SThA acquisitions is explicated by the absence of right SThA in 2 volunteers and by the orthodontic brackets, responsible for artefacts in 5 volunteers. The loss of precision in monophasic sequences compared to 2D-cine PC sequences for small diameter vessels, around 0,55% to 27% shouldn’t stop the use of monophasic PC sequences. In fact, the decrease of 70 % of the duration even for many vessels make possible its application in clinical practice. The precision is acceptable, nearby one of the echo-doppler [3], the current standard method, and appears sufficient to quantify a flow in small vessels, for example, to guide the choice of recipient vessel before cervico-facial reconstruction. Some protocol improvements are envisaged, including increasing spatial resolution and using surface coils but Gadolinium injections are not envisaged because our preoccupation was to develop a non-invasive technic.
CONCLUSION
The monophasic PC-MRI is a quantitative vascular examination, non-invasive, quick, and useful in clinical practice. Therefore, the protocol improvement stay necessary for the smallest vessels to obtain better precision in order to compare flow values before and after treatments or to follow up, for example, patients with facial vascular malformations.Acknowledgements
Caroline, Garance, Sophie, nos manipulatrices radio
EA CHIMERE 7516
Facing Faces Institute
GIE Faire-Face
ARS
Equipex
References
[1] Bettoni J, Pagé G, Salsac A-V, Constans J-M, Testelin S, Devauchelle B, Balédent O, Dakpé S, 3T Non-Injected Phase-Contrast MRI Sequences for the Mapping of the External Carotid Branches: In Vivo Radio-Anatomical Pilot Study for Feasibility Analysis, Journal of CranioMaxillofacial Surgery (2017), doi: 10.1016/j.jcms.2017.09.005
[2] Ambarki K., Hallberg P., Jóhannesson G., Lindén C., Zarrinkoob L., Wåhlin A., Birgander R., Malm J., Eklund A., Blood Flow of Ophthalmic Artery in Healthy Individuals Determined by Phase-Contrast Magnetic Resonance Imaging,Investigative Ophthalmology & Visual Science (2013), Vol.54, 2738-2745. doi:10.1167/iovs.13-11737
[3] Yzet T., Bouzerar R., Allart J.-D., Demuynck F., Legallais C., Robert B., Balédent O. Hepatic vascular flow measurements by phase contrast MRI and doppler echography: A comparative and reproducibility study. Journal of Magnetic Resonance Imaging (2010), 31(3), 579–588. doi:10.1002/jmri.22079
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