Absolute cerebral blood flow measured by dynamic susceptibility contrast MRI: a direct comparison with Xe-133 SPECT

Absolute regional cerebral blood flow (CBF) was measured in ten healthy volunteers, using both dynamic susceptibility-contrast (DSC) magnetic resonance imaging (MRI) and Xe-133 SPECT within-4 h. After i.v. injection of Gd-DTPA-BMA (0.3 mmol/kg b.w.), the bolus was monitored with a Simultaneous Dual FLASH pulse sequence (1.5 s image), providing one slice through brain tissue and a second slice through the carotid artery. ConcentrationC(t)x − (1 TE) ln[S(t)/S(0)] was related to CBF asC(t)=CBF [AIF(t)⊗R(t)], where AIF is the arterial input function andR(t) is the residue function. A singular-value-decomposition-based deconvolution technique was used for retrieval ofR(t). Absolute CBF was given by Zierler’s area-to-height relation and the central volume principle. For elimination of large vessels (ELV), all MRI-based CBF values exceeding 2.5 times the mean CBF value of the slice were excluded. A correction for partial-volume effects (CPVE) in the artery used for AIF monitoring was based on registration of signal in a phantom with tubes of various diameters (1.5–6.5 mm), providing an individual concentration correction factor applied to AIF data registered in vivo. In the Xe-133 SPECT investigation, 3000–4000 MBq of Xe-133 was administered intravenously, and CBF was calculated using the Kanno-Lassen algorithm. When ELV and CPVE were applied. DSC-MRI showed average CBF values from the entire slice of 43±10 ml/(min 100 g) (small-artery AIF) and 48±17 ml (min 100 g) (carotid-artery AIF) (mean±S.D.,n=10). The corresponding Xe-133-SPECT-based CBF was 33±6 ml (min 100 g) (n=10). The relationships of CBF(MRI) versus CBF(SPECT) showed good linear correlation (r=0.74–0.83).     

Absolute cerebral blood flow measured by dynamic susceptibility contrast MRI: a direct comparison with Xe-133 SPECT

Absolute regional cerebral blood flow (CBF) was measured in ten healthy volunteers, using both dynamic susceptibility-contrast (DSC) magnetic resonance imaging (MRI) and Xe-133 SPECT within 4 h. After i.v. injection of Gd-DTPA-BMA (0.3 mmol/kg b.w.), the bolus was monitored with a Simultaneous Dual FLASH pulse sequence (1.5 s/image), providing one slice through brain tissue and a second slice through the carotid artery. Concentration C(t) is proportional to -(1/TE) ln[S(t)/S(0)] was related to CBF as C(t) = CBF [AIF(t) x R(t)], where AIF is the arterial input function and R(t) is the residue function. A singular-value-decomposition-based deconvolution technique was used for retrieval of R(t). Absolute CBF was given by Zierler's area-to-height relation and the central volume principle. For elimination of large vessels (ELV), all MRI-based CBF values exceeding 2.5 times the mean CBF value of the slice were excluded. A correction for partial-volume effects (CPVE) in the artery used for AIF monitoring was based on registration of signal in a phantom with tubes of various diameters (1.5-6.5 mm), providing an individual concentration correction factor applied to AIF data registered in vivo. In the Xe-133 SPECT investigation, 3,000-4,000 MBq of Xe-133 was administered intravenously, and CBF was calculated using the Kanno Lassen algorithm. When ELV and CPVE were applied, DSC-MRI showed average CBF values from the entire slice of 43 +/- 10 ml/(min 100 g) (small-artery AIF) and 48 +/- 17 ml/(min 100 g) (carotid-artery AIF) (mean +/- S.D., n = 10). The corresponding Xe-133-SPECT-based CBF was 33 +/- 6 ml/(min 100 g) (n = 10). The relationships of CBF(MRI) versus CBF(SPECT) showed good linear correlation (r = 0.74-0.83).     

Examining the relationship between blood flow velocity and movement of erythrocytes in a capillary using laser doppler velocimetry

In this study, we consider the relationship between red blood cell velocity and the movement of erythrocytes. Many velocimeters measure fluid velocity by tracking the movement of tracer particles present in the fluid. Generally, in laser Doppler velocimetry, seeding particles of suitable density and size are added to the fluid being measured, but this is not possible for in vivo measurements. In the case of blood, erythrocytes are used as the tracer particles. It is unclear, however, whether the velocity of erythrocytes reflects actual red blood cell velocity. Therefore, we compare the results of flow velocity distribution measurements of blood in the ear vessels of mouse and in water containing tracer particles in a serpentine flow channel. Results of the comparison indicate that the velocity of moving erythrocytes does not correspond exactly to the velocity of the blood. The difference is due to the changes in the fringe pattern under the skin. However, we consider that it is possible to measure red blood cell velocity in any direction using these fringe changes. Moreover, we confirm that results obtained using the proposed method match those obtained using other methods. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Hemodynamics in a three-dimensional printed aortic model: a comparison of four-dimensional phase-contrast magnetic resonance and image-based computational fluid dynamics

Magnetic Resonance Materials in Physics, Biology and Medicine - This study aims to compare an electrocardiogram (ECG)-gated four-dimensional (4D) phase-contrast (PC) magnetic resonance imaging...     

Radiomics-based machine-learning method to diagnose prostate cancer using mp-MRI: a comparison between conventional and fused models

Magnetic Resonance Materials in Physics, Biology and Medicine - Multiparametric MRI (mp-MRI) has been significantly used for detection, localization and staging of Prostate cancer (PCa). However,...     

A new optimal reactive power flow model in rectangular form and its solution by predictor corrector primal dual interior point method

A new optimal reactive power flow (ORPF) model in rectangular form is proposed in this paper. In this model, the load tap changing (LTC) transformer branch is represented by an ideal transformer and its series impedance with a dummy node located between them. The voltages of the two sides of the ideal transformer are then used to replace the turn ratio of the LTC so that the ORPF model becomes quadratic. The Hessian matrices in this model are constants and need to be calculated only once in the entire optimal process, which speed up the calculation greatly. The solution of the ORPF problem by the predictor corrector primal dual interior point method is described in this paper. Two separate prototypes for the new and the conventional methods are developed in MATLAB in order to compare the performances. The results obtained from the implemented seven test systems ranging from 14 to 1338 buses indicate that the proposed method achieves a superior performance than the conventional rectangular coordinate-based ORPF.     

Development of a new two-input PSS to control low-frequency oscillation in interconnecting power systems and the study of a low-frequency oscillation model

In Japan, large and small power systems were interconnected over time and thus ultimately grew into a large-scale national power system. A highly important stability problem arising from large-scale power system interconnections is low-frequency oscillation (about 0.3 Hz to 0.5 Hz) of interconnected systems. The ΔP-type PSS has been applied to all generators in trunk power systems as a measure to improve the damping of local mode oscillation (about 1 Hz). However, it is difficult for this PSS to improve the damping of low-frequency oscillation because of the hardware and the design of PSS control constants. Therefore it has become necessary to develop a new two-input PSS. This paper explains the development of this two-input PSS and the study of a low-frequency oscillation model. This paper can be summarized as follows:

• 1 (1) The effect of control over low-frequency oscillation is affected by the kinds of PSS detecting signals. The Δω-type or Δf-type detecting signals used for lead-phase compensation are suitable for this purpose.
• 2 (2) It is possible to cause low-frequency oscillation studies in a one-machine infinite-bus power system model with medium loads.
• 3 (3) According to the simulation of a three-machine and actual large-power system models, dynamic stability was largely increased by this two-input PSS used for generators.

     

Dynamic susceptibility contrast perfusion MRI using phase-based venous output functions: comparison with pseudo-continuous arterial spin labelling and assessment of contrast agent concentration in large veins

Objectives

Contrast agent (CA) relaxivities are generally not well established in vivo, and the relationship between frequency/phase shift and magnetic susceptibility might be a useful alternative for CA quantification.

Materials and methods

Twenty volunteers (25–84 years old) were investigated using test–retest pre-bolus dynamic susceptibility-contrast (DSC) magnetic resonance imaging (MRI). The pre-bolus phase-based venous output function (VOF) time integral was used for arterial input function (AIF) rescaling. Resulting cerebral blood flow (CBF) data for grey matter (GM) were compared with pseudo-continuous arterial spin labelling (ASL). During the main bolus CA passage, the apparent spatial shift (pixel shift) of the superior sagittal sinus (seen in single-shot echo-planar imaging (EPI)) was converted to CA concentration and compared with conventional ΔR2*-based data and with a predicted phase-based VOF from the pre-bolus experiment.

Results

The phase-based pre-bolus VOF resulted in a reasonable inter-individual GM CBF variability (coefficient of variation 28 %). Comparison with ASL CBF values implied a tissue R2*-relaxivity of 32 mM^?1 s^?1. Pixel-shift data at low concentrations (data not available at peak concentrations) were in reasonable agreement with the predicted phase-based VOF.

Conclusion

Susceptibility-induced phase shifts and pixel shifts are potentially useful for large-vein CA quantification. Previous predictions of a higher R2*-relaxivity in tissue than in blood were supported.

     

Effect of new manganese contrast agent on tissue intensities in human volunteers: comparison of 0.23, 0.6 and 1.5 T MRI,a part of a phase I trial

To evaluate the effect of a new oral manganese contrast agent (CMC-001) on magnetic resonance imaging (MRI) intensities at different magnetic field strengths. Twelve healthy volunteers underwent abdominal MRI 1 week before and within 2.5–4.5 h after CMC-001 (MnCl₂ and absorption promoters dissolved in water) intake at three different MR scanners of 0.23, 0.6 and 1.5 T. Image contrast and intensity enhancement of liver and pancreas were analysed relatively to muscle and fat intensities. Manganese blood levels were followed for 24 h. Whole-blood manganese concentration levels stayed within the normal range. The liver intensities on T2w images decreased about 10% for the 1/2 contrast dose and about 20% for the full contrast dose independent of the field strength. The liver intensities on T1w images increased more than 30% for 1/2 contrast dose and over 40% for full contrast dose. The maximum T1 enhancement was achieved at the highest field. Pancreas intensities were not affected. Contrast between liver, muscle and fat intensities increased with magnetic field, as well as standard errors of the volunteer-averaged intensities. Oral intake of CMC-001 influences liver intensities and does not affect pancreas intensities at different magnetic field strengths.     

High-permittivity pads to enhance SNR and transmit efficiency in MRI of the heart at 7T: a simulation study

Magnetic Resonance Materials in Physics, Biology and Medicine - High-permittivity pads have shown promising results in enhancing SNR and transmit efficiency when used for MRI of the brain, but...     

Sensory brain activation during rectal balloon distention: a pilot study in healthy volunteers to assess safety and feasibility at 1.5T

Objective

Although increasing evidence suggests a central mechanism of action for sacral neuromodulation, the exact mechanism remains unclear. We set up a scanning paradigm to measure brain activation related to various stages of rectal filling using rectal balloon distention.

Materials and Methods

Six healthy volunteers underwent rectal balloon distention during MRI scanning at a 1.5T scanner with a Tx/Rx head coil. MR images were collected at four levels of distention: empty balloon (EB), first sensation volume (FSV), desire to defecate volume (DDV), maximum tolerable volume (MTV). Data were analyzed using BrainVoyager 20.4. Whole brain and ROI-based fixed-effects general linear model analyses were performed on the fMRI time-course data from all participants.

Results

Rectal filling until FSV evoked the most blood-oxygen-level-dependent responses in several clusters throughout the cortex, followed by the responses evoked by rectal filling until DDV. Interestingly, rectal filling until MTV evoked negative responses compared to baseline throughout the cortex. No negative side effects were found.

Discussion

This study shows that a standardized paradigm for functional MRI combined with rectal filling is feasible and safe in healthy volunteers and is ready to be used in fecal incontinent patients to assess whether their brain activity differs from healthy controls.

     

Tumor microvasculature observed using different contrast agents: a comparison between Gd-DTPA-Albumin and B-22956/1 in an experimental model of mammary carcinoma

OBJECTIVE: The aim of this study was to compare a pure macromolecular contrast agent (Gd-DTPA-albumin) with a new protein-binding blood pool contrast agent (B22956/1) in terms of their capacity to investigate the microvasculature in an experimental model of mammary carcinoma. MATERIALS AND METHODS: Tumors were induced by subcutaneous injection of 5 x 10(5) BB1 cells into the backs of 5-7 week-old female FVB/neuNT233 mice. The animals were observed using DCE-MRI when the longest diameter of the tumor was 10.2+/-2.0 mm. DCE-MRI experiments were carried out using B22956/1 and (24 h later) Gd-DTPA-albumin. RESULTS: DCE-MRI data showed that vasculature in the tumor rim was characterized by greater fractional plasma volume and transendothelial permeability than vasculature in the tumor core as measured by both contrast agents. Permeability to Gd-DTPA-albumin in the tumor core was hardly measurable while permeability to B22956/1 was substantial. Histologically the tumor core showed areas of well vascularized, viable tissue surrounded by necrotic regions. CONCLUSIONS: DCE-MRI experiments performed with B22956/1 are useful in the investigation of vasculature in those tumor regions that are characterized by low permeability to macromolecules.     

A quantitative alternative to the Goutallier classification system using Lava Flex and Ideal MRI techniques: volumetric intramuscular fatty infiltration of the supraspinatus muscle,a cadaveric study

Magnetic Resonance Materials in Physics, Biology and Medicine - The Goutallier classification system is the most commonly used method for grading intramuscular fatty infiltration in rotator cuff...     

Sex,body mass index,and blood pressure are related to aortic characteristics in healthy,young adults using magnetic resonance vessel wall imaging: the AMBITYON study

Objectives

More detailed evaluation of atherosclerosis and its key determinants in young individuals is warranted to improve knowledge on the pathophysiology of its development and progression. This study evaluated associations of magnetic resonance imaging (MRI)-derived aortic wall area, wall thickness, and pulse wave velocity (PWV) with cardiovascular risk factors in asymptomatic, young adults.

Materials and methods

In 124 adults (age: 25–35 years) from the general population-based Atherosclerosis Monitoring and Biomarker Measurements in the Young study, demography, anthropometry, and blood samples were collected. The studied MRI-parameters were measured using a 3.0T MRI system. Relations between cardiovascular risk factors and aortic characteristics were assessed using multivariable linear regression analyses.

Results

Mean age was 31.8 years, 47.6% was male. Aortic wall area was positively associated with age [β = 0.01, (95% confidence interval (CI) 2.00 × 10^?3, 0.02), p = 0.01] and BMI [β = 0.01, (0.01, 0.02), p = 0.003] and negatively associated with sex (reference: men) [β = ?0.06, (?0.11, ?0.01), p = 0.02]. Natural logarithm transformed (ln) aortic wall thickness was positively associated with BMI [β = 0.01, (1.00 × 10^?3, 0.02), p = 0.02]. Ln aortic PWV was positively associated with 10 mmHg increment of SBP [β = 0.06, (0.03, 0.09), p < 0.001] and DBP [β = 0.06, (0.02, 0.09), p = 0.006]. No relations were observed for smoking and lipids.

Conclusions

Already in early adulthood, aortic wall geometry and stiffness vary by age, sex, BMI, and blood pressure.