MRI Quantitative T2* Mapping to Predict Dominant Composition of In Vitro Thrombus.

BACKGROUND AND PURPOSE: MR imaging quantitative T2* mapping, which provides information about thrombus composition and specifically the red blood cell content, may be obtained in the setting of acute ischemic stroke before treatment. This could be useful to adapt the endovascular strategy. We aimed to analyze the red blood cell content of in vitro thrombi in relation to the thrombus-T2* relaxation time. MATERIALS AND METHODS: Thirty-five thrombus analogs of different compositions were scanned with an MR imaging quantitative T2* mapping sequence. Two radiologists, blinded to thrombus composition, measured the thrombus-T2* relaxation time twice at an interval of 2 weeks. Quantitative histologic evaluations of red blood cell content were performed. Inter- and intraobserver reproducibility of the thrombus-T2* relaxation time was assessed by calculating intraclass correlation coefficients. Finally, a Spearman product moment correlation between the thrombus-T2* relaxation time and red blood cell content was performed. RESULTS: The median thrombus-T2* relaxation time was 78.5 ms (range, 16-268 ms; interquartile range, 60.5 ms). The median red blood cell content was 55% (range, 0%-100%; interquartile range, 75%). Inter- and intraobserver reproducibility of the thrombus-T2* relaxation time was excellent (>0.9). The Spearman rank correlation test found a significant inverse correlation between thrombus-T2* relaxation time and red blood cell content (ρ = -0.834, P < .001). CONCLUSIONS: MR imaging quantitative T2* mapping can reliably identify the thrombus red blood cell content in vitro. This fast, easy-to-use sequence could be implemented in routine practice to predict stroke etiology and adapt devices or techniques for endovascular treatment of acute ischemic stroke.

In-vitro validation of 4D flow MRI measurements with an experimental pulsatile flow model.

PURPOSE: The purpose of this study was to assess the precision of four-dimensional (4D) phase-contrast magnetic resonance imaging (PCMRI) to measure mean flow and peak velocity (Vmax) in a pulsatile flow phantom and to test its sensitivity to spatial resolution and Venc. MATERIAL AND METHODS: The pulsatile flow phantom consisted of a straight tube connected to the systemic circulation of an experimental mock circulatory system. Four-dimensional-PCMR images were acquired using different spatial resolutions (minimum pixel size: 1.5×1.5×1.5mm3) and velocity encoding sensitivities (up to three times Vmax). Mean flow and Vmax calculated from 4D-PCMRI were compared respectively to the reference phantom flow parameters and to Vmax obtained from two-dimensional (2D)-PCMRI. RESULTS: 4D-PCI measured mean flow with a precision of -0.04% to+5.46%, but slightly underestimated Vmax when compared to 2D-PCMRI (differences ranging from -1.71% to -3.85%). 4D PCMRI mean flow measurement was influenced by spatial resolution (P<0.001) with better results obtained with smaller voxel size. There was no effect of Venc on mean flow measurement. Regarding Vmax, neither spatial resolution nor Venc did influence the precision of the measurement. CONCLUSION: Using an experimental pulsatile flow model 4D-PCMRI is accurate to measure mean flow and Vmax with better results obtained with higher spatial resolution. We also show that Venc up to 3 times higher than Vmax may be used with no effect on these measurements.

Efficacy of second intra-tendinous platelet-rich-plasma injection in case of incomplete response of the first injection: three-year follow up experience.

PURPOSE: Tendinopathy is a frequent and ubiquitous disease developing early disorganized collagen fibers with neo-angiogenesis on histology. Peritendinous injection of corticosteroid is the commonly accepted strategy despite the absence of inflammation in tendinopathy. Platelet-rich plasma (PRP) might be a useful strategy to rapidly accelerate healing of the tendinopathy but there is a lack ok knowledge about the amount of PRP to be injected and the opportunity of a second injection in case of partial pain relief. The aim of our study was to assess the potential therapeutic effect of early second PRP intra-tendinous to treat persistent painful tendon tear and tendinosis in a long-term follow-up by ultrasonography (US) and clinical data in case of incomplete efficiency of first PRP treatment injection. MATERIALS AND METHODS: Twenty-four consecutive patients referred for US treatment of tendon tear or tendinosis (T+) were included retrospectively. All had previously received a single intra-tendinous injection of PRP under US guidance (PRPT+) and benefited of a second PRP injection (PRPT2+) under US guidance in order to treat persistent painful. US and clinical data were collected for each anatomic compartment for upper and lower limbs before treatment (D0), 6 weeks (W6) after first treatment, 6 weeks (W12) after second treatment and until 32-month follow-up. We used Mac Nemar test and regression model to compare US and clinical data. RESULTS: The residual US size of lesions was not significantly lower at W12 after PRPT2+ as compared to W6 (P=0.86 in upper and P=NS in lower member) independently of age (P=0.22), gender (P=0.97) and kind of tendinopathy (P=NS). Quick dash test values and WOMAC values were not significantly lower in PRPT+ at W12 (average: 21.5 months) as compared to W6 (P>0.66) and long-term follow-up (P>0.75) independently of age (P=0.39), gender (P=0.63) and kind of tendinopathy (P=NS). Nevertheless, comparison between D0 and long-term follow-up (LTF) functionnal score was statistically significant (p<0.001 in upper and lower member). CONCLUSION: Our study suggests that second early intra-tendinous PRP injection under US guidance does not permit rapid decrease of tendinopathy area in US, nor does it quickly improve clinical pain and functional data in case of incomplete efficiency of first PRP injection. However, in long-term follow-up, patients improved their ability to mobilize pathologic tendons.

Overestimation of moderate carotid stenosis assessed by both Doppler US and contrast enhanced 3D-MR angiography in the CARMEDAS study.

PURPOSE: To evaluate the agreement and diagnostic accuracy of Contrast enhanced magnetic resonance angiography (CE-MRA), Doppler ultrasound (DUS) and Digital subtraction angiography (DSA) in the assessment of carotid stenosis. METHODS: DUS, CE-MRA and DSA were performed in 56 patients included in the Carotide-angiographie par résonance magnétique-échographie-doppler-angioscanner (CARMEDAS) multicenter study with a carotid stenosis ≥ 50%. Three readers evaluated stenoses on CE-MRA and DSA (NASCET criteria). Velocities criteria were used for stenosis estimation on DUS. RESULTS: CE-MRA had a sensitivity and specificity of 96-98% and 66-83% respectively for carotid stenoses ≥ 50% and a sensitivity and specificity of 94% and 76-84% respectively for carotid stenoses ≥ 70%. The interobserver agreement of CE-MRA was excellent, except for moderate stenoses (50-69%). DUS had a sensitivity and specificity of 88 and 75% respectively for carotid stenoses ≥ 50% and a sensitivity and specificity of 83 and 86% respectively for carotid stenoses ≥ 70%. Combined concordant CE-MRA and DUS had a sensitivity and specificity of 100 and 85-90% respectively for carotid stenoses ≥ 50% and a sensitivity and specificity of 96-100% and 80-87% respectively for carotid stenoses ≥ 70%. The positive predictive value of the association CE-MRA and DUS for carotid stenoses ≥ 70% is calculated between 77 and 82% while the negative predictive value is calculated between 97 and 100%. CE-MRA and DUS have concordant findings in 63-72%, and the overestimations cases were recorded only for carotid stenosis ≤ 69%. CONCLUSION: Combined DUS-CE-MRA is excellent for evaluation of severe stenosis but remains debatable in moderate stenosis (50-69%) due to the risk of overestimations.

[State of the art: high resolution MR imaging of carotid atherosclerotic plaque]. / Mise au point sur l'IRM haute résolution de la plaque carotidienne.

A third of cerebrovascular accidents are a complication from carotid artery plaque. In addition to the degree of stenosis, plaque composition and morphology are key elements in determining the probability of complication from the atherosclerotic plaque. High resolution MRI can characterize plaque composition and morphology and therefore help identify unstable plaque. The purpose of this review is to summarize recent concepts on unstable plaque and underlying inflammation. The signal characteristics of the different components of plaque on high resolution MRI then be reviewed. Finally, current morphological and functional criteria for unstable plaque will be discussed.