scholarly journals Validating a Local Arterial Input Function Method for Improved Perfusion Quantification in Stroke

2011 ◽  
Vol 31 (11) ◽  
pp. 2189-2198 ◽  
Author(s):  
Lisa Willats ◽  
Soren Christensen ◽  
Henry K Ma ◽  
Geoffrey A Donnan ◽  
Alan Connelly ◽  
...  
Keyword(s):  
Time Course ◽  
Arterial Input Function ◽  
Input Function ◽  
Perfusion Magnetic Resonance Imaging ◽  
Data Sets ◽  
Bolus Tracking ◽  
Perfusion Quantification ◽  
Magnetic Resonance Imaging Mri ◽  
Arterial Input Functions ◽  
Contrast Bolus

In bolus-tracking perfusion magnetic resonance imaging (MRI), temporal dispersion of the contrast bolus due to stenosis or collateral supply presents a significant problem for accurate perfusion quantification in stroke. One means to reduce the associated perfusion errors is to deconvolve the bolus concentration time-course data with local Arterial Input Functions (AIFs) measured close to the capillary bed and downstream of the arterial abnormalities causing dispersion. Because the MRI voxel resolution precludes direct local AIF measurements, they must be extrapolated from the surrounding data. To date, there have been no published studies directly validating these local AIFs. We assess the effectiveness of local AIFs in reducing dispersion-induced perfusion error by measuring the residual dispersion remaining in the local AIF deconvolved perfusion maps. Two approaches to locating the local AIF voxels are assessed and compared with a global AIF deconvolution across 19 bolus-tracking data sets from patients with stroke. The local AIF methods reduced dispersion in the majority of data sets, suggesting more accurate perfusion quantification. Importantly, the validation inherently identifies potential areas for perfusion underestimation. This is valuable information for the identification of at-risk tissue and management of stroke patients.

scholarly journals Arterial input function measurements for bolus tracking perfusion imaging in the brain

2012 ◽  
Vol 69 (3) ◽  
pp. 771-780 ◽  
Author(s):  
Elias Kellner ◽  
Irina Mader ◽  
Michael Mix ◽  
Daniel Nico Splitthoff ◽  
Marco Reisert ◽  
...  
Keyword(s):  
Perfusion Imaging ◽  
Arterial Input Function ◽  
Input Function ◽  
Bolus Tracking ◽  
The Brain

scholarly journals Quantitative perfusion-CMR is significantly influenced by the placement of the arterial input function

2020 ◽  
Author(s):  
Ibnul Mia ◽  
Melanie Le ◽  
Christophe Arendt ◽  
Diana Brand ◽  
Sina Bremekamp ◽  
...  
Keyword(s):  
Ejection Fraction ◽  
Signal Intensity ◽  
Arterial Input Function ◽  
Input Function ◽  
Left Ventricular ◽  
Strongly Correlated ◽  
Time To Peak ◽  
Wide Range ◽  
Perfusion Quantification ◽  
Peak Signal Intensity

Abstract The aim of this study is to provide a systematic assessment of the influence of the position on the arterial input function (AIF) for perfusion quantification. In 39 patients with a wide range of left ventricular function the AIF was determined using a diluted contrast bolus of a cardiac magnetic resonance imaging in three left ventricular levels (basal, mid, apex) as well as aortic sinus (AoS). Time to peak signal intensities, baseline corrected peak signal intensity and upslopes were determined and compared to those obtained in the AoS. The error induced by sampling the AIF in a position different to the AoS was determined by Fermi deconvolution. The time to peak signal intensity was strongly correlated (r2 > 0.9) for all positions with a systematic earlier arrival in the basal (− 2153 ± 818 ms), the mid (− 1429 ± 928 ms) and the apical slice (− 450 ± 739 ms) relative to the AoS (all p < 0.001). Peak signal intensity as well as upslopes were strongly correlated (r2 > 0.9 for both) for all positions with a systematic overestimation in all positions relative to the AoS (all p < 0.001 and all p < 0.05). Differences between the positions were more pronounced for patients with reduced ejection fraction. The error of averaged MBF quantification was 8%, 13% and 27% for the base, mid and apex. The location of the AIF significantly influences core parameters for perfusion quantification with a systematic and ejection fraction dependent error. Full quantification should be based on obtaining the AIF as close as possible to the myocardium to minimize these errors.

scholarly journals Development of a non-radiometric method for measuring the arterial input function of a 11C-labeled PET radiotracer

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
H. Umesha Shetty ◽  
Sami S. Zoghbi ◽  
Cheryl L. Morse ◽  
Aneta Kowalski ◽  
Jussi Hirvonen ◽  
...  
Keyword(s):  
Time Course ◽  
Arterial Input Function ◽  
Human Subjects ◽  
Radioactive Tracer ◽  
Input Function ◽  
Radiometric Method ◽  
Attractive Alternative ◽  
Molar Activity ◽  
Positron Emission ◽  
Liquid Chromatography Tandem Mass

Abstract Positron emission tomography (PET) uses radiotracers to quantify important biochemical parameters in human subjects. A radiotracer arterial input function (AIF) is often essential for converting brain PET data into robust output measures. For radiotracers labeled with carbon-11 (t1/2 = 20.4 min), AIF is routinely determined with radio-HPLC of blood sampled frequently during the PET experiment. There has been no alternative to this logistically demanding method, neither for regular use nor validation. A 11C-labeled tracer is always accompanied by a large excess of non-radioactive tracer known as carrier. In principle, AIF might be obtained by measuring the molar activity (Am; ratio of radioactivity to total mass; Bq/mol) of a radiotracer dose and the time-course of carrier concentration in plasma after radiotracer injection. Here, we implement this principle in a new method for determining AIF, as shown by using [11C]PBR28 as a representative tracer. The method uses liquid chromatography-tandem mass spectrometry for measuring radiotracer Am and then the carrier in plasma sampled regularly over the course of a PET experiment. Am and AIF were determined radiometrically for comparison. The new non-radiometric method is not constrained by the short half-life of carbon-11 and is an attractive alternative to conventional AIF measurement.

scholarly journals Susceptibility of Tmax to Tracer Delay on Perfusion Analysis: Quantitative Evaluation of Various Deconvolution Algorithms Using Digital Phantoms

2010 ◽  
Vol 31 (3) ◽  
pp. 908-912 ◽  
Author(s):  
Kohsuke Kudo ◽  
Makoto Sasaki ◽  
Leif Østergaard ◽  
Soren Christensen ◽  
Ikuko Uwano ◽  
...  
Keyword(s):  
Arterial Input Function ◽  
Ct Perfusion ◽  
Region Of Interest ◽  
Input Function ◽  
Residue Function ◽  
Data Sets ◽  
Positive Linear Correlation ◽  
The Right ◽  
Value Decomposition ◽  
Digital Phantoms

The time-to-maximum of the tissue residue function ( Tmax) perfusion index has proven very predictive of infarct growth in large clinical trials, yet its dependency on simple tracer delays remains unknown. Here, we determine the dependency of computed tomography (CT) perfusion (CTP) Tmax estimates on tracer delay using a range of deconvolution techniques and digital phantoms. Digital phantom data sets simulating the tracer delay were created from CTP data of six healthy individuals, in which time frames of the left cerebral hemisphere were shifted forward and backward by up to ±5 seconds. These phantoms were postprocessed with three common singular value decomposition (SVD) deconvolution algorithms—standard SVD (sSVD), block-circulant SVD (bSVD), and delay-corrected SVD (dSVD)—with an arterial input function (AIF) obtained from the right middle cerebral artery (MCA). The Tmax values of the left hemisphere were compared among different tracer delays and algorithms by a region of interest-based analysis. The Tmax values by sSVD were positively correlated with ‘positive shifts’ but unchanged with ‘negative shifts,’ those by bSVD had an excellent positive linear correlation with both positive and negative shifts, and those by dSVD were relatively constant, although slightly increased with the positive shifts. The Tmax is a parameter highly dependent on tracer delays and deconvolution algorithm.

Improved Contrast in Ultra-Low-Field MRI with Time-Dependent Bipolar Prepolarizing Fields: Theory and NMR Demonstrations

2013 ◽  
Vol 20 (3) ◽  
pp. 327-336 ◽  
Author(s):  
Jaakko O. Nieminen ◽  
Jens Voigt ◽  
Stefan Hartwig ◽  
Hans Jürgen Scheer ◽  
Martin Burghoff ◽  
...  
Keyword(s):  
Field Strength ◽  
Time Course ◽  
Signal Strength ◽  
Relaxation Rates ◽  
Resonance Imaging ◽  
New Approach ◽  
Spin Lattice ◽  
Low Field ◽  
Low Field Mri ◽  
Magnetic Resonance Imaging Mri

Abstract The spin-lattice (T1) relaxation rates of materials depend on the strength of the external magnetic field in which the relaxation occurs. This T1 dispersion has been suggested to offer a means to discriminate between healthy and cancerous tissue by performing magnetic resonance imaging (MRI) at low magnetic fields. In prepolarized ultra-low-field (ULF) MRI, spin precession is detected in fields of the order of 10-100 μT. To increase the signal strength, the sample is first magnetized with a relatively strong polarizing field. Typically, the polarizing field is kept constant during the polarization period. However, in ULF MRI, the polarizing-field strength can be easily varied to produce a desired time course. This paper describes how a novel variation of the polarizing-field strength and duration can optimize the contrast between two types of tissue having different T1 relaxation dispersions. In addition, NMR experiments showing that the principle works in practice are presented. The described procedure may become a key component for a promising new approach of MRI at ultra-low fields

scholarly journals Normative distribution of posterior circulation tissue time-to-maximum: Effects of anatomic variation, tracer kinetics, and implications for patient selection in posterior circulation ischemic stroke

2021 ◽  
pp. 0271678X2098239
Author(s):  
Adam E Goldman-Yassen ◽  
Matus Straka ◽  
Michael Uhouse ◽  
Seena Dehkharghani
Keyword(s):  
Ischemic Stroke ◽  
Selection Criteria ◽  
Arterial Input Function ◽  
Anatomic Variation ◽  
Input Function ◽  
Posterior Circulation ◽  
Anterior Circulation ◽  
Vessel Occlusion ◽  
Perfusion Time

The generalization of perfusion-based, anterior circulation large vessel occlusion selection criteria to posterior circulation stroke is not straightforward due to physiologic delay, which we posit produces physiologic prolongation of the posterior circulation perfusion time-to-maximum (Tmax). To assess normative Tmax distributions, patients undergoing CTA/CTP for suspected ischemic stroke between 1/2018-3/2019 were retrospectively identified. Subjects with any cerebrovascular stenoses, or with follow-up MRI or final clinical diagnosis of stroke were excluded. Posterior circulation anatomic variations were identified. CTP were processed in RAPID and segmented in a custom pipeline permitting manually-enforced arterial input function (AIF) and perfusion estimations constrained to pre-specified vascular territories. Seventy-one subjects (mean 64 ± 19 years) met inclusion. Median Tmax was significantly greater in the cerebellar hemispheres (right: 3.0 s, left: 2.9 s) and PCA territories (right: 2.9 s; left: 3.3 s) than in the anterior circulation (right: 2.4 s; left: 2.3 s, p < 0.001). Fetal PCA disposition eliminated ipsilateral PCA Tmax delays (p = 0.012). Median territorial Tmax was significantly lower with basilar versus any anterior circulation AIF for all vascular territories (p < 0.001). Significant baseline delays in posterior circulation Tmax are observed even without steno-occlusive disease and vary with anatomic variation and AIF selection. The potential for overestimation of at-risk volumes in the posterior circulation merits caution in future trials.

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