Yi-Jui Liu

T2 measurement of the human myocardium using a T2-prepared transient-state TrueFISP sequence.

A fast and motion‐insensitive technique suitable for myocardial BOLD contrast imaging is presented. The method, termed T2‐TrueFISP, combines T2 magnetization preparation with steady‐state free precession (SSFP) imaging for T2 relaxation mapping of the myocardium in healthy volunteers. The T2 contrast‐to‐noise ratio (CNR) was optimized with the use of transient‐state TrueFISP readout and half‐Fourier readout with linear phase encoding. Single‐slice myocardial T2‐weighted image was obtained within one heartbeat, and a single slice T2 map of the myocardium was obtained in under 5–7 s. A respiratory navigator‐gating method was incorporated for serial measurements and signal averaging, with the subjects breathing freely. The mean myocardial T2 relaxation time measured in 12 healthy volunteers was 54 ± 5.7 ms. Regional variations of T2 values across the myocardium were 7%. Temporal variations across serial T2 measurements in a transmural region covering ∼0.5 cc of the left ventricular (LV) wall were 3.6% without signal averaging (number of excitations (NEX) = 1) and 1.7% with signal averaging (NEX = 10). According to our preliminary results, the T2‐TrueFISP method is expected to provide a robust and sensitive tool for clinical application of myocardial BOLD contrast imaging. Magn Reson Med 57:960–966, 2007.

Angiogenic response of locally advanced breast cancer to neoadjuvant chemotherapy evaluated with parametric histogram from dynamic contrast-enhanced MRI

The aim of this study was to evaluate angiogenic compositions and tumour response in the course of neoadjuvant chemotherapy in patients with locally advanced breast cancer (LABC) using dynamic contrast-enhanced (DCE) MRI. Thirteen patients with LABC underwent serial DCE MRI during the course of chemotherapy. DCE MRI was quantified using a two-compartment model on a pixel-by-pixel basis. Analysis of parametric histograms of amplitude, exchange rate k(out) and peak enhancement over the whole tumour was performed. The distribution patterns of histograms were correlated with the tumour response. Initial kurtosis and standard deviation of amplitude before chemotherapy correlated with tumour response, r = 0.63 and r = 0.61, respectively. Comparing the initial values with the values after the first course of chemotherapy, tumour response was associated with a decrease in standard deviation of amplitude (r = 0.79), and an increase in kurtosis and a decrease in standard deviation of k(out) (r = 0.57 and 0.57, respectively). Comparing the initial values with the values after completing the chemotherapy, tumours with better response were associated with an increase in kurtosis (r = 0.62), a decrease in mean (r = 0.84) and standard deviation (r = 0.77) of amplitude, and a decrease in mean of peak enhancement (r = 0.71). Our results suggested that tumours with better response tended to alter their internal compositions from heterogeneous to homogeneous distributions and a decrease in peak enhancement after chemotherapy. Serial analyses of parametric histograms of DCE MRI-derived angiogenic parameters are potentially useful to monitor the response of angiogenic compositions of a tumour throughout the course of chemotherapy, and might predict tumour response early in the course.

Intracerebral implantation of autologous peripheral blood stem cells in stroke patients: A randomized phase II study

In our previous study, intracerebral implantation of peripheral blood stem cells (PBSCs) improved functional outcome in rats with chronic cerebral infarction. Based on this finding, a randomized, single blind controlled study was conducted in 30 patients [PBSC group (n = 15) and control group (n = 15)] with middle cerebral artery infarction confirmed on a T2-weighted MRI 6 months to 5 years after a stroke. Only subjects with neurological deficits of intermediate severity based on the National Institute of Health Stroke Scale (NIHSS; range: 9–20) that had been stable for at least 3 months were enrolled. Those in the PBSC group received subcutaneous G-CSF injections (15 μg/kg/day) for 5 consecutive days, and then stereotaxic implantation of 3–8 × 106 CD34+ immunosorted PBSCs. All 30 patients completed the 12-month follow-up. No serious adverse events were noted during study period. Improvements in stroke scales (NIHSS, ESS, and EMS) and functional outcomes (mRS) from baseline to the end of the 12-month follow-up period were significantly greater in the PBSC than the control group. The fiber numbers asymmetry (FNA) scores based on diffusion tensor image (DTI) tractography were reduced in every PBSC-treated subject, but not in the control group. Reduction in the FNA scores correlated well with the improvement in NIHSS. Furthermore, a positive motor-evoked potential (MEP) response by transcranial magnetic stimulation (TMS) appeared in 9 of the 15 subjects in the PBSC group. This phase II study demonstrated that implantation of autologous CD34+ PBSC was safe, feasible, and effective in improving functional outcome.

Volume-Dependent Overestimation of Spontaneous Intracerebral Hematoma Volume by the ABC/2 Formula

Background: Although the ABC/2 formula has been widely used to estimate the volume of intracerebral hematoma (ICH), the formula tends to overestimate hematoma volume. The volume-related imprecision of the ABC/2 formula has not been documented quantitatively. Purpose: To investigate the volume-dependent overestimation of the ABC/2 formula by comparing it with computer-assisted volumetric analysis (CAVA). Material and Methods: Forty patients who had suffered spontaneous ICH and who had undergone non-enhanced brain computed tomography scans were enrolled in this study. The ICH volume was estimated based on the ABC/2 formula and also calculated by CAVA. Based on the ICH volume calculated by the CAVA method, the patients were divided into three groups: group 1 consisted of 17 patients with an ICH volume of less than 20 ml; group 2 comprised 13 patients with an ICH volume of 20 to 40 ml; and group 3 was composed of 10 patients with an ICH volume larger than 40 ml. Results: The mean estimated hematoma volume was 43.6 ml when using the ABC/2 formula, compared with 33.8 ml when using the CAVA method. The mean estimated difference was 1.3 ml, 4.4 ml, and 31.4 ml for groups 1, 2, and 3, respectively, corresponding to an estimation error of 9.9%, 16.7%, and 37.1% by the ABC/2 formula (P<0.05). Conclusion: The ABC/2 formula significantly overestimates the volume of ICH. A positive association between the estimation error and the volume of ICH is demonstrated.

Intervertebral Disk Degeneration Related to Reduced Vertebral Marrow Perfusion at Dynamic Contrast-Enhanced MRI

OBJECTIVE The purpose of this study was to use dynamic contrast-enhanced MRI to ascertain the relation between intervertebral disk degeneration and lumbar vertebral marrow blood perfusion. SUBJECTS AND METHODS We recruited 25 patients (50 vertebral bodies) who underwent dynamic contrast-enhanced MRI of the lumbar spine. The peak signal enhancement of each vertebral body was calculated from the time signal after curve fitting of a pharmacokinetic model. We controlled for other variables that might have affected blood perfusion by assessing two vertebral bodies in each patient. The 25 patients were divided into three groups. In group 1, one of the vertebral bodies (L1 or L3) evaluated was between two adjacent normal disks and the other was between two adjacent degenerated disks. In group 2, each of the two vertebral bodies evaluated was between two normal disks. In group 3 each of the two vertebral bodies evaluated was between two degenerated disks. RESULTS Without normalization by minimization of other variables, there were no statistically significant differences in original peak enhancement values among groups 1, 2, and 3 (p = 0.179). After normalization, the peak enhancement in group 1 (0.846 +/- 0.060) was significantly lower than that in group 2 (0.988 +/- 0.047) (p = 0.003) or group 3 (0.973 +/- 0.081) (p = 0.008). CONCLUSION After normalization, lumbar vertebral marrow perfusion correlated well with intervertebral disk degeneration evaluated with dynamic contrast-enhanced MRI. Blood perfusion was 14% less in the vertebral body marrow between two degenerated disks than in vertebral marrow between two normal disks.

Hematoma Shape, Hematoma Size, Glasgow Coma Scale Score and ICH Score: Which Predicts the 30-Day Mortality Better for Intracerebral Hematoma?

Purpose To investigate the performance of hematoma shape, hematoma size, Glasgow coma scale (GCS) score, and intracerebral hematoma (ICH) score in predicting the 30-day mortality for ICH patients. To examine the influence of the estimation error of hematoma size on the prediction of 30-day mortality. Materials and Methods This retrospective study, approved by a local institutional review board with written informed consent waived, recruited 106 patients diagnosed as ICH by non-enhanced computed tomography study. The hemorrhagic shape, hematoma size measured by computer-assisted volumetric analysis (CAVA) and estimated by ABC/2 formula, ICH score and GCS score was examined. The predicting performance of 30-day mortality of the aforementioned variables was evaluated. Statistical analysis was performed using Kolmogorov-Smirnov tests, paired t test, nonparametric test, linear regression analysis, and binary logistic regression. The receiver operating characteristics curves were plotted and areas under curve (AUC) were calculated for 30-day mortality. A P value less than 0.05 was considered as statistically significant. Results The overall 30-day mortality rate was 15.1% of ICH patients. The hematoma shape, hematoma size, ICH score, and GCS score all significantly predict the 30-day mortality for ICH patients, with an AUC of 0.692 (P = 0.0018), 0.715 (P = 0.0008) (by ABC/2) to 0.738 (P = 0.0002) (by CAVA), 0.877 (P<0.0001) (by ABC/2) to 0.882 (P<0.0001) (by CAVA), and 0.912 (P<0.0001), respectively. Conclusion Our study shows that hematoma shape, hematoma size, ICH scores and GCS score all significantly predict the 30-day mortality in an increasing order of AUC. The effect of overestimation of hematoma size by ABC/2 formula in predicting the 30-day mortality could be remedied by using ICH score.

Effects of gender, age, and body mass index on fat contents and apparent diffusion coefficients in healthy parotid glands: an MRI evaluation.

ObjectivesTo establish standard apparent diffusion coefficient (ADC) and the fat content as a function of age, gender and body mass index (BMI) in healthy parotid glands, and to address the influences of fat suppression on ADC measurements.MethodsA total of 100 healthy adults (gender and age evenly distributed) were prospectively recruited, with parotid fat content measured from gradient-echo images with fat–water separated using iterative decomposition with echo asymmetry and least squares (IDEAL). The ADCs were estimated using both fat-saturated and non-fat-saturated diffusion-weighted imaging via a periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) technique.ResultsParotid fat content was larger in men than in women by about 10 percentage points (P < 0.005), and positively associated with BMI and age for both genders (mostly with P < 0.001). ADCs estimated with non-fat-saturated PROPELLER were significantly lower in men than in women (P < 0.005), but showed no gender difference if measured using fat-saturated PROPELLER (P = 0.840). The negative association between parotid ADC and age/BMI/fat (P < 0.001) showed greater regression slopes in non-fat-saturated PROPELLER than in fat-saturated data.ConclusionsParotid fat content in healthy adults correlates positively with both age and BMI; the correlation with age is gender-dependent. Parotid ADC measurements are strongly influenced by fat saturation.Key Points• Parotid fat content in healthy adults correlates positively with age and BMI.• The rate of aging-related increase in fat contents is gender-dependent.• Parotid ADC measurements are strongly influenced by fat saturation.

Relationship of Idiopathic Osteonecrosis of the Femoral Head to Perfusion Changes in the Proximal Femur by Dynamic Contrast-Enhanced MRI

OBJECTIVE The purpose of this article is to relate intramedullary perfusion of the proximal femur to severity of osteonecrosis of the femoral head by using dynamic contrast-enhanced MRI (DCE-MRI). SUBJECTS AND METHODS Twelve patients (14 symptomatic hips) who underwent DCE-MRI and had subsequent core decompression of the femoral head were examined. Hips were graded for severity according to MRI findings and were assigned scores of 0 (negative findings), 1 (focal marrow abnormalities), and 2 (subchondral collapse). Thirteen asymptomatic hips acted as controls. The DCE-MRI data were analyzed by use of a pharmacokinetic two-compartment model. RESULTS Compared with control hips, there was significantly greater peak enhancement in the femoral head in hips of all grades (p < 0.001) and in the femoral neck (p = 0.001) and intertrochanteric area (p = 0.001) in grade 2 hips. The time to peak was significantly delayed in the femoral head in grade 0 hips (p = 0.02) and in the intertrochanteric area in grade 2 hips (p = 0.003) compared with the controls. CONCLUSION As evaluated by DCE-MRI, intramedullary peak enhancement in the femoral head increased with progression of idiopathic osteonecrosis of the femoral head, whereas there was delayed peak enhancement in the femoral head in hips with negative findings and intertrochanteric stasis in advanced osteonecrosis of the femoral head. Such perfusion changes as shown on MRI can occur with early osteonecrosis in the absence of other MRI abnormalities.

Multiplying optical tweezers force using a micro-lever.

This study presents a photo-driven micro-lever fabricated to multiply optical forces using the two-photon polymerization 3D-microfabrication technique. The micro-lever is a second class lever comprising an optical trapping sphere, a beam, and a pivot. A micro-spring is placed between the short and long arms to characterize the induced force. This design enables precise manipulation of the micro-lever by optical tweezers at the micron scale. Under optical dragging, the sphere placed on the lever beam moves, resulting in torque that induces related force on the spring. The optical force applied at the sphere is approximately 100 to 300 pN, with a laser power of 100 to 300 mW. In this study, the optical tweezers drives the micro-lever successfully. The relationship between the optical force and the spring constant can be determined by using the principle of leverage. The arm ratio design developed in this study multiplies the applied optical force by 9. The experimental results are in good agreement with the simulation of spring property.

Are the Local Blood Oxygen Level–Dependent (BOLD) Signals Caused by Neural Stimulation Response Dependent on Global BOLD Signals Induced by Hypercapnia in the Functional MR Imaging Experiment? Experiments of Long-Duration Hypercapnia and Multilevel Carbon Dioxide Concentration

BACKGROUND AND PURPOSE: The relationship between the local blood oxygen level–dependent (BOLD) signals caused by neural stimulation (fBOLD) and the global BOLD signals induced by hypercapnia (hBOLD) has not been fully investigated. In this study, we examine whether fBOLD is modulated by hBOLD signals, by means of experiments using a relatively wide range of inhaled carbon dioxide (CO2) for a long duration of 5 minutes. MATERIALS AND METHODS: Ten healthy volunteers were recruited, each undergoing 6 separate experiments by inhaling gas mixtures with different fractions of CO2 (room air, 3%–7%). Each experiment contained 3 phases, prehypercapnic, hypercapnic, and posthypercapnic, during which boxcar visual stimulus was given. The local fBOLD signals were measured from areas showing activation patterns highly correlated with the visual stimulus paradigm, whereas the global hBOLD signals were measured from areas showing no visual activations. Percentage changes in fBOLD during transient-state hypercapnia and steady-state hypercapnia were both investigated in response to varying degrees of hypercapnic perturbations. RESULTS: The hBOLD signals increased with increase of inhaled CO2 fractions. The duration for the hBOLD signals to reach steady state prolonged with increase of inhaled CO2 fractions. Normalized fBOLD ratio was inversely related to the inhaled CO2 during steady-state hypercapnia but showed positive association with hBOLD during transient-state hypercapnia. CONCLUSION: Our study concludes that the steady-state fBOLD signal intensity is dependent on and inversely related to the hBOLD signals. Previous reports documenting independent and additive relationships between hBOLD and fBOLD may likely be due to transient-state observations.