Home About us Contact
|
Home About us Contact | ||
|
|
||
Perfusion Parameters (perfusion + parameter)
Selected AbstractsPerfusion parameters derived from bolus-tracking perfusion imaging are immune to tracer recirculation,JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 3 2010Jayme Cameron Kosior PhD Abstract Purpose: To investigate the impact of tracer recirculation on estimates of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT). Materials and Methods: The theoretical model used to derive CBF, CBV, and MTT was examined. CBF and CBV estimates with and without tracer recirculation were compared in computer simulations to examine the effects of tracer recirculation. Results: The equations used to derive CBF, CBV, and MTT assume that the arterial input function and tissue tracer signals define the input and output signals, respectively, of a linear time-invariant system. As a result of the principle of superposition, these perfusion parameters are immune to tracer recirculation, which was confirmed by computer simulation. However, limited acquisition durations can lead to CBV and CBF errors of up to 50%. Conclusion: Tracer recirculation does not impact estimation of CBF, CBV, or MTT. However, previous approaches used to remove recirculation effects may be beneficial when used to compensate for limited acquisition durations in which the passage of the bolus is not adequately captured. J. Magn. Reson. Imaging 2010;31:753,756. © 2010 Wiley-Liss, Inc. [source] Calculation of cerebral perfusion parameters using regional arterial input functions identified by factor analysisJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 4 2006Linda Knutsson MS Abstract Purpose To calculate regional cerebral blood volume (rCBV), regional cerebral blood flow (rCBF), and regional mean transit time (rMTT) accurately, an arterial input function (AIF) is required. In this study we identified a number of AIFs using factor analysis of dynamic studies (FADS), and performed the cerebral perfusion calculation pixel by pixel using the AIF that was located geometrically closest to a certain voxel. Materials and Methods To verify the robustness of the method, simulated images were generated in which dispersion or delay was added in some arteries and in the corresponding cerebral gray matter (GM), white matter (WM), and ischemic tissue. Thereafter, AIFs were determined using the FADS method and simulations were performed using different signal-to-noise ratios (SNRs). Simulations were also carried out using an AIF from a single pixel that was manually selected. In vivo results were obtained from normal volunteers and patients. Results The FADS method reduced the underestimation of rCBF due to dispersion or delay that often occurs when only one AIF represents the entire brain. Conclusion This study indicates that the use of FADS and the nearest-AIF method is preferable to manual selection of one single AIF. J. Magn. Reson. Imaging 2006. © 2006 Wiley-Liss, Inc. [source] Evaluation of an AIF correction algorithm for dynamic susceptibility contrast-enhanced perfusion MRIMAGNETIC RESONANCE IN MEDICINE, Issue 1 2008Peter Brunecker Abstract For longitudinal studies in patients suffering from cerebrovascular diseases the poor reproducibility of perfusion measurements via dynamic susceptibility-weighted contrast-enhanced MRI (DSC-MRI) is a relevant concern. We evaluate a novel algorithm capable of overcoming limitations in DSC-MRI caused by partial volume and saturation issues in the arterial input function (AIF) by a blood flow stimulation-study. In 21 subjects, perfusion parameters before and after administration of blood flow stimulating L -arginine were calculated utilizing a block-circulant singular value decomposition (cSVD). A total of two different raters and three different rater conditions were employed to select AIFs: Besides 1) an AIF selection by an experienced rater, a beginner rater applied a steady state-oriented strategy, returning; 2) raw; and 3) corrected AIFs. Highly significant changes in regional cerebral blood flow (rCBF) by 9.0% (P < 0.01) could only be found when the AIF correction was performed. To further test for improved reproducibility, in a subgroup of seven subjects the baseline measurement was repeated 6 weeks after the first examination. In this group as well, using the correction algorithm decreased the SD of the difference between the two baseline measurements by 42%. Magn Reson Med 60:102,110, 2008. © 2008 Wiley-Liss, Inc. [source] Perfusion computed tomography in the acute phase of mild head injury: Regional dysfunction and prognostic value,ANNALS OF NEUROLOGY, Issue 6 2009Zwany Metting MD Objective Traumatic brain injury is a major cause of disability and death. Most patients sustain a mild head injury with a subgroup that experiences disabling symptoms interfering with return to work. Brain imaging in the acute phase is not predictive of outcome, as 20% of noncontrast computed tomographic (CT) scans on admission is normal in patients with a suboptimal outcome. The aim of this study was to perform perfusion CT imaging in the acute phase of mild head injury in patients without intracranial abnormalities on the noncontrast CT, to assess whether these patients had cerebral perfusion abnormalities. Furthermore, the relation between perfusion CT parameters and severity of head injury and outcome was evaluated. Methods In patients with mild head injury and normal noncontrast CT, perfusion CT was performed directly after admission. The perfusion data were compared with data of 25 healthy control subjects. Outcome was determined 6 months after injury with the extended Glasgow Coma Outcome Scale score and return to work. Results Seventy-six patients were included. In patients with a decreased Glasgow Coma Scale score, a significant decrease of cerebral blood flow and cerebral blood volume was detected in the frontal and occipital gray matter. In logistic regression analyses, decreased cerebral blood flow and cerebral blood volume in the frontal lobes predicted worse outcome according to the extended Glasgow Coma Outcome Scale score. CT perfusion parameters did not predict return to work. Interpretation In the acute phase of mild head injury, disturbed cerebral perfusion is seen in patients with normal noncontrast CT correlating with severity of injury and outcome. Ann Neurol 2009;66:809,816 [source] | ||||||||||