Automatic model‐based analysis of skeletal muscle BOLD‐MRI in reactive hyperemia

Schewzow, Kiril; Andreas, Martin; Moser, Ewald; Wolzt, Michael; Schmid, A.

doi:10.1002/jmri.23919

Cited by 12 publications

(13 citation statements)

References 20 publications

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“…Another strategy to raise significance is to reduce variability by taking model fitted peak and TTP, since the raw peak and TTP is based on a single data point so is highly susceptible to noise. Fitting the responses to a known mathematical function, such as a gamma-variate function, has been demonstrated for reactive hyperemic blood oxygen-level dependent imaging [30]. While the function may also fit ASL reactive hyperemia of the healthy subjects, the diseased responses may not resemble a gamma-variate function, as exemplified by response 9 in Fig 6.…”

Section: Discussionmentioning

confidence: 99%

A physiological model for interpretation of arterial spin labeling reactive hyperemia of calf muscles

Chen

Wright

2017

PLoS ONE

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To characterize and interpret arterial spin labeling (ASL) reactive hyperemia of calf muscles for a better understanding of the microcirculation in peripheral arterial disease (PAD), we present a physiological model incorporating oxygen transport, tissue metabolism, and vascular regulation mechanisms. The model demonstrated distinct effects between arterial stenoses and microvascular dysfunction on reactive hyperemia, and indicated a higher sensitivity of 2-minute thigh cuffing to microvascular dysfunction than 5-minute cuffing. The recorded perfusion responses in PAD patients (n = 9) were better differentiated from the normal subjects (n = 7) using the model-based analysis rather than characterization using the apparent peak and time-to-peak of the responses. The analysis results suggested different amounts of microvascular disease within the patient group. Overall, this work demonstrates a novel analysis method and facilitates understanding of the physiology involved in ASL reactive hyperemia. ASL reactive hyperemia with model-based analysis may be used as a noninvasive microvascular assessment in the presence of arterial stenoses, allowing us to look beyond the macrovascular disease in PAD. A subgroup who will have a poor prognosis after revascularization in the patients with critical limb ischemia may be associated with more severe microvascular diseases, which may potentially be identified using ASL reactive hyperemia.

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Section: Discussionmentioning

confidence: 99%

A physiological model for interpretation of arterial spin labeling reactive hyperemia of calf muscles

Chen

Wright

2017

PLoS ONE

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“…To improve SNR, the time courses were smoothed using a moving average window of three time points. To extract the curve parameters peak value (PV), time to peak (TTP), and time from the peak to half peak signal (TT½P) of T 2 *‐weighted signal automatically and to avoid operator‐dependent bias, a model function

f (t) = g (t) + s (t) + l (t)

g (t) = g_{0} \cdot {(t - t_{0})}^{g_{1}} \cdot exp (- g_{2} (t - t_{0}))

s (t) = s_{0} / (1 + exp (- s_{1} (t - t_{0} - t_{1})))

l (t) = l_{0} + l_{1} (t - t_{0})

was fitted to the T 2 *‐weighted time courses of GAS during recovery. PV, TTP and TT½P were calculated numerically from the fit curves.…”

Section: Methodsmentioning

confidence: 99%

Dynamic ASL and T2* -weighted MRI in exercising calf muscle at 7 T: A feasibility study

et al. 2014

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“…The S EPI signal as a function of time ( t ) during recovery was then fitted to a model

\begin{matrix} f (t) = g (t) + s (t) + l_{0} + l_{1} (t - t_{0}) \\ g (t) = g_{0} (t - t_{0})^{g_{1}} {normale}^{g_{2} (t - t_{0})} \\ s (t) = s_{0} \frac{1}{1 + {normale}^{- s_{1} (t - t_{0} - t_{1})}} \end{matrix}

described previously . From the fit results, post exercise time to peak (TTP) and peak amplitudes were derived.…”

Section: Methodsmentioning

confidence: 99%

Exercising calf muscle changes correlate with pH, PCr recovery and maximum oxidative phosphorylation

et al. 2014

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Skeletal muscle metabolism is impaired in disorders like diabetes mellitus or peripheral vascular disease. The skeletal muscle echo planar imaging (EPI) signal (SEPI) and its relation to energy metabolism are still debated.Localised 31P MRS and SEPI data from gastrocnemius medialis of 19 healthy subjects were combined in one scanning session to study direct relationships between phosphocreatine (PCr), pH kinetics and parameters of time courses. Dynamic spectroscopy (semi-LASER) and EPI were performed immediately before, during and after 5 min of plantar flexions. Data were acquired in a 7 T MR scanner equipped with a custom-built ergometer and a dedicated 31P/1H radio frequency (RF) coil array.Using a form-fitted multi-channel 31P/1H coil array resulted in high signal-to-noise ratio (SNR). PCr and pH in the gastrocnemius medialis muscle were quantified from each 31P spectrum, acquired every 6 s. During exercise, SEPI(t) was found to be a linear function of tissue pH(t) (cross-correlation r = –0.85 ± 0.07). Strong Pearson's correlations were observed between post exercise time-to-peak (TTP) of SEPI and (a) the time constant of PCr recovery τPCr recovery (r = 0.89, p < 10− 6), (b) maximum oxidative phosphorylation using the linear model, Qmax, lin (r = 0.65, p = 0.002), the adenosine-diphosphate-driven model, Qmax,ADP (r = 0.73, p = 0.0002) and (c) end exercise pH (r = 0.60, p = 0.005).Based on combined accurately localised 31P MRS and weighted MRI, both with high temporal resolution, strong correlations of the skeletal muscle SEPI during exercise and tissue pH time courses and of post exercise SEPI and parameters of energy metabolism were observed. In conclusion, a tight coupling between skeletal muscle metabolic activity and tissue signal weighting, probably induced by osmotically driven water shift, exists and can be measured non-invasively, using NMR at 7 T.

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Automatic model‐based analysis of skeletal muscle BOLD‐MRI in reactive hyperemia

Cited by 12 publications

References 20 publications

A physiological model for interpretation of arterial spin labeling reactive hyperemia of calf muscles

A physiological model for interpretation of arterial spin labeling reactive hyperemia of calf muscles

Dynamic ASL and T2* -weighted MRI in exercising calf muscle at 7 T: A feasibility study

Exercising calf muscle changes correlate with pH, PCr recovery and maximum oxidative phosphorylation

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