Accurate Measurement of Cross-Sectional Area of Femoral Artery on MRI Sequences of Transcontinental Ultramarathon Runners Using Optimal Parameters Selection.

In clinics an accurate vessel segmentation method is important to quantize the vessel volume change with respect to time for artery elasticity measurement. This study proposes a modified version on 3D-expanded dynamic programming to find an optimal surface in a 3D matrix. The aim of this study is to discover the robustness against noises in measuring the cross-sectional area of the femoral artery on MRI datasets of ultra-endurance runners as accurately as possible. To do this, we use phantom images with different added noises and different image contrasts to find out the optimal parameters using grid search. The contrast between the vessel lumen and its background in phantom study is changed to simulate the real MRI dataset. We also add a plaque in phantom images to test the accuracy of the proposed algorithm in dealing pathologic cases. The phantom studies and grid search on selecting optimal parameters can offer an alternative way on parameter selection. In application to MRI, the accuracy is performed via comparisons between the manual tracings of experts and automated results. The mean relative error is 2.1 % ± 2.1 % on testing 11 MRI datasets (total 550 images). The phantom studies and grid search on selecting optimal parameters can offer an alternative way on parameter selection.

Montgomery T-Tube Airway Restoration and Swallowing Rehabilitation for a Near-Hanging Female.

Patients who fail to commit suicide by hanging often end up with laryngotracheal injuries, which may lead to a compromised airway, swallowing dysfunction, and dysphonia. Previous studies have mainly focused on airway management after near-hanging attempts. Few have shed light on the treatment of swallowing dysfunction after laryngotracheal injuries. Here, we present a near-hanging patient who developed complete dysphagia shortly afterward. We used a Montgomery T-tube as an endolaryngeal stent, combined with swallowing rehabilitation. The patient's swallowing ability was gradually restored one month after the surgery, and the stent was removed six months later. The present case report exemplifies the unique way of using the Montgomery T-tubes in clinical practice. Among the patients with airway stenosis affecting the larynx and extending to the vocal cords, Montgomery T-tube may be the only stent that can help manage strictures at the level of the vocal cords and in the supraglottic region, restoring swallowing function and maintaining the airway.

Influence of pain location and hand dominance on scapular kinematics and EMG activities: an exploratory study.

BACKGROUND: Assessment of three-dimensional kinematics and electromyography (EMG) activities is common in patients with chronic neck pain. However, the effect of hand dominance and neck pain location on the measurement of movement and EMG characteristics is still unclear. Therefore, the purpose of this study was to investigate the effect of neck pain location and arm dominance on the scapular kinematics and muscle EMG activities in patients with chronic neck pain. METHODS: Thirty subjects (10 males, 20 females; mean age (sd): 38 (11.9) years) with chronic neck pain for more than 3 months were recruited. The scapular kinematics and EMG activity of the upper trapezius and sternocleidomastoid muscles were measured during the bilateral arm elevation task. The three-way repeated measures ANOVA was used to examine the effect of neck pain location and hand dominance on the measurement of kinematics and EMG muscle activities. RESULTS: The movement of scapular posterior tilt was significantly influenced by arm dominance (P = 0.001) and by the interaction of arm dominance and elevation angle (P = 0.002). The movement of scapular upward/downward rotation was affected by the interaction of arm dominance and elevation angle (P = 0.02). The location of pain did not show any significant influence on the scapular movement and muscle activities. CONCLUSIONS: Hand dominance could have an influence on the scapular kinematics, which should be taken into consideration when describing and comparing neuromuscular characteristics in individuals with chronic neck pain.

Comparative Analgesic Efficacies of Ropivacaine and Bupivacaine for Postoperative Rectus Sheath Block in Paediatric Abdominal Surgery: A Meta-Analysis of Randomized Controlled Trial and Retrospective Cohort Studies.

Background: The optimal dose and concentration of analgesic efficacy of ropivacaine (RPV) and bupivacaine (BPV) for postoperative pain relief in paediatric abdominal surgery patients is still unclear. Therefore, this meta-analysis compared the efficacy of these analgesics, their administered modes (ultrasound-guided RSB versus LAI) for postoperative pain relief, and side effects. Methods: Three databases, PubMed, Embase, and Cochrane Database of Systematic Reviews, were exhaustively searched with predefined keywords. Eight randomized clinical trials and retrospective studies were selected. Analgesic effect, postoperative pain score, level of side effect, applied dose, and concentration of drug were analysed. Results: Drug dose ranged from 0.5-2.5 mL/kg of 0.2 to 0.5% concentrations. Male participant for RSB and LAI treatment groups varied from 40-62% and 25-83%, respectively. Mean age of RSB and LAI groups ranged from 3.8-11.65 years and 4.3-11.27 years, respectively. Our meta-analysis revealed that RSB could reduce total opioid use postoperatively (WMD = -0.02, 95% CI: -0.02, -0.02), with I 2 value of 15%. We found that the RPV (0.25%, 2.5 ml/kg) was optimal in suppressing the pain. Its lower concentration (0.2%) was ineffective, whereas higher one (0.375%) seems to increase risk of systemic toxicity. Similarly, BPV (0.25%, 2.5 mg/kg) efficaciously reduced the pain score, while its lower concentration was ineffective. The combined postoperative pain score in the RPV-treated group was found to be significantly reduced (p < 0.01) with I 2 value of 85% indicating high heterogeneity. Conclusion: Both RPV and BPV were significantly effective in reducing postoperative pain score. It appears that RSB could be a preferred choice to deliver analgesia, due to reduced opiate dose requirement and improved clinical safety without significant postoperative adverse events.

Removal of CSF pixels on brain MR perfusion images using first several images and Otsu's thresholding technique.

Brain MR perfusion imaging is used to evaluate local perfusion in patients with cerebral vascular disease. Quantitative measurements on the hemodynamic parameters and volume of brain with abnormal perfusion provide an estimation of the severity of the brain perfusion defect. However, quantitative measurements of these focal cerebral hemodynamic parameters are limited by the presence of cerebrospinal fluid (CSF) pixels. We noticed that the CSF has a higher signal than other tissue types on the first perfusion image, which is usually discarded in routine parametric image calculations. This signal difference, however, can be used to segment CSF pixels on the perfusion images. An image division was used to generate ratio images to compensate for spatially dependent signal variation caused by the inhomogeneity of excitation radiofrequency field. By applying an appropriate signal threshold to the ratio images, CSF pixels can be identified and removed from the parametric images. With the removal of CSF pixels, the volume of delayed-perfusion brain parenchyma can be better visualized and the interference from the CSF can be avoided. The proposed technique is simple, fast, automatic, and effective, and no extra scanning is needed to use this technique.

Association between contrast-enhanced MR images and blood-brain barrier disruption following transcranial focused ultrasound.

PURPOSE: To investigate the correlation between the contrast-enhanced magnetic resonance imaging (MRI) signal and the duration of blood-brain barrier (BBB) disruption induced by focused ultrasound (FUS). MATERIALS AND METHODS: FUS was applied to 45 rat brains in the presence of microbubbles, and these rats were scanned on a 3T MRI system at several timepoints. The rat brains were then studied using contrast-enhanced spin echo T1-weighted images. At the same time, BBB disruption was evaluated based on Evans blue (EB) extravasation. The relationship between the normalized signal intensity change of the MRI and EB extravasation was analyzed by least-squares linear regression and the calculation of correlation coefficients. RESULTS: When MRI enhancement was quantitatively evaluated by EB extravasation, a strong correlation between the normalized signal intensity change of the MRI and EB extravasation was identified during BBB disruption after sonication. However, the correlation coefficient decreased as BBB closure occurred after sonication ended. CONCLUSION: The contrast-enhanced MRI signal can potentially be used to evaluate the amount of chemotherapeutic agents entering the targeted tissue, but the accuracy of the assessment will be affected by the time interval since sonication.

Stasis index from hemodynamic analysis using quantitative DSA correlates with hemorrhage of supratentorial arteriovenous malformation: a cross-sectional study.

OBJECTIVE: Assessments of hemorrhage risk based on angioarchitecture have yielded inconsistent results, and quantitative hemodynamic studies have been limited to small numbers of patients. The authors examined whether cerebral hemodynamic analysis using quantitative digital subtraction angiography (QDSA) can outperform conventional DSA angioarchitecture analysis in evaluating the risk of hemorrhage associated with supratentorial arteriovenous malformations (AVMs). METHODS: A cross-sectional study was performed by retrospectively reviewing adult supratentorial AVM patients who had undergone both DSA and MRI studies between 2011 and 2017. Angioarchitecture characteristics, DSA parameters, age, sex, and nidus volume were analyzed using univariate and multivariate logistic regression, and QDSA software analysis was performed on DSA images. Based on the QDSA analysis, a stasis index, defined as the inflow gradient divided by the absolute value of the outflow gradient, was determined. The receiver operating characteristic (ROC) curve was used to compare diagnostic performances of conventional DSA angioarchitecture analysis and analysis using hemodynamic parameters based on QDSA. RESULTS: A total of 119 supratentorial AVM patients were included. After adjustment for age at diagnosis, sex, and nidus volume, the exclusive deep venous drainage (p < 0.01), observed through conventional angioarchitecture examination using DSA, and the stasis index of the most dominant drainage vein (p = 0.02), measured with QDSA hemodynamic analysis, were independent risk factors for hemorrhage. The areas under the ROC curves for the conventional DSA method (0.75) and QDSA hemodynamics analysis (0.73) were similar. A venous stasis index greater than 2.18 discriminated the hemorrhage group with a sensitivity of 52.6% and a specificity of 81.5%. CONCLUSIONS: In QDSA, a higher stasis index of the most dominant drainage vein is an objective warning sign associated with supratentorial AVM rupture. Risk assessments of AVMs using QDSA and conventional DSA angioarchitecture were equivalent. Because QDSA is a complementary noninvasive approach without extra radiation or contrast media, comprehensive hemorrhagic risk assessment of cerebral AVMs should include both DSA angioarchitecture and QDSA analyses.

The respiratory modulation of intracranial cerebrospinal fluid pulsation observed on dynamic echo planar images.

Pressure changes in cerebrospinal fluid (CSF) that occur with respiration rhythms have been studied in animals and humans for more than 100 years. This phenomenon has been recently validated in vivo on MR images by applying spectral analysis to signal-time curves at selected regions of interest. However, selecting regions of interest requires knowledge of physiology and anatomy, and manual selection is time consuming. We postulate that CSF pulsation is passively modulated by intra-thoracic pressure that is secondary to respiration, and this pulsation can be observed as a flow-related enhancement on MR images. To investigate the spatiotemporal patterns of respiratory rhythms in human brains, we conducted a study on MR scanning of 12 healthy volunteers who performed normal-breathing and breath-holding experiments during scanning. Spectral analysis, spectroscopic images, independent component analysis and signal measurements in selected regions were applied to dynamic MR images acquired from these volunteers. Through independent component analysis, respiratory rhythms were found at the vicinity of ventricles and CSF areas in nine subjects in normal-breathing experiments. In breath-holding experiments, respiratory rhythm suppression and vessel dilation were observed in 8 and 10 subjects, respectively. Information obtained from this study further elucidates the respiratory modulation of CSF in vivo.

Automatic flow analysis of digital subtraction angiography using independent component analysis in patients with carotid stenosis.

PURPOSE: Current time-density curve analysis of digital subtraction angiography (DSA) provides intravascular flow information but requires manual vasculature selection. We developed an angiographic marker that represents cerebral perfusion by using automatic independent component analysis. MATERIALS AND METHODS: We retrospectively analyzed the data of 44 patients with unilateral carotid stenosis higher than 70% according to North American Symptomatic Carotid Endarterectomy Trial criteria. For all patients, magnetic resonance perfusion (MRP) was performed one day before DSA. Fixed contrast injection protocols and DSA acquisition parameters were used before stenting. The cerebral circulation time (CCT) was defined as the difference in the time to peak between the parietal vein and cavernous internal carotid artery in a lateral angiogram. Both anterior-posterior and lateral DSA views were processed using independent component analysis, and the capillary angiogram was extracted automatically. The full width at half maximum of the time-density curve in the capillary phase in the anterior-posterior and lateral DSA views was defined as the angiographic mean transient time (aMTT; i.e., aMTTAP and aMTTLat). The correlations between the degree of stenosis, CCT, aMTTAP and aMTTLat, and MRP parameters were evaluated. RESULTS: The degree of stenosis showed no correlation with CCT, aMTTAP, aMTTLat, or any MRP parameter. CCT showed a strong correlation with aMTTAP (r = 0.67) and aMTTLat (r = 0.72). Among the MRP parameters, CCT showed only a moderate correlation with MTT (r = 0.67) and Tmax (r = 0.40). aMTTAP showed a moderate correlation with Tmax (r = 0.42) and a strong correlation with MTT (r = 0.77). aMTTLat also showed similar correlations with Tmax (r = 0.59) and MTT (r = 0.73). CONCLUSION: Apart from vascular anatomy, aMTT estimates brain parenchyma hemodynamics from DSA and is concordant with MRP. This process is completely automatic and provides immediate measurement of quantitative peritherapeutic brain parenchyma changes during stenting.

Toward normal perfusion after radiosurgery: perfusion MR Imaging with independent component analysis of brain arteriovenous malformations.

BACKGROUND AND PURPOSE: Brain perfusion is disturbed by cerebral arteriovenous malformations (AVMs). Our study was conducted to determine the radiosurgical effects on this disturbed perfusion. METHODS: MR perfusion imaging with independent component analysis was performed in five healthy subjects and 19 patients with AVM before and after radiosurgery (every 6 months up to 2 years). Perfusion map relative cerebral blood volume (rCBV), cerebral blood flow (rCBF), and mean transient time (rMTT) were assessed. Regions of interest (ROIs) on AVM target sections were defined as follows: N, AVM nidus; H, the rest of the ipsilateral hemisphere; P, immediately posterior to the nidus; A, immediately anterior to the nidus; Ar, anterior remote; Pr, posterior remote. Similar ROIs in the contralateral hemisphere (N1, H1, P1, A1, Pr1, and Ar1) served as internal references. Perfusion ratios of ROI-ROI1 were defined. Nonparameteric Mann-Whitney U tests and generalized linear models were used for statistical analysis. RESULTS: Before radiosurgery, patients' H/H1 rCBV and rCBF ratios were significantly higher than those of healthy subjects (P < .005), indicating AVM steal. Three types of perilesional perfusion disturbance were observed. From the first postradiosurgical follow-up at 6 months, N/N1 rCBV and rCBF ratios gradually decreased to 1.0 (both P < .001), whereas rMTT ratios gradually increased to 1.0 (P < .015); H/H1, A/A1, and P/P1 rCBV and rCBF ratios decreased after radiosurgery (P < .005), indicating reversal of steal toward normal perfusion. CONCLUSION: Initial high transnidal flow and perinidal perfusion disturbances were demonstrated. They gradually changed toward normal perfusion after radiosurgery. This explains, in part, the pathophysiologic factors of AVM and therapeutic effects.

Automatic measurements of arterial input and venous output functions on cerebral computed tomography perfusion images: a preliminary study.

BACKGROUND: The current automatic techniques for measuring arterial input function (AIF) and venous output (VOF) on cerebral computed tomography perfusion images are prone to motion artifact and random noise, and their failure rates vary between 10% and 65%. We developed a new automatic technique to overcome these problems. METHODS: A principle axis transformation was applied to perfusion images to correct for translational and rotational motion artifacts. Bone voxels and neighboring voxels were removed from the perfusion images. Only brain voxels were included in the AIF and VOF measurement procedures. The selection criteria, such as large area under the concentration-time curve, early arrival of contrast agents, and narrow effective width, were used to select appropriate arterial and venous voxels for the AIF and VOF measurements. The proposed automatic technique was tested in 20 patients with unilateral cerebral arterial stenosis. The results of the proposed technique were compared to the results obtained by manual measurements and commercially available automatic selection software. RESULTS: The AIFs and VOFs were successfully measured using the proposed automatic technique in all 20 patients. The curve shapes, including the area under the concentration-time curve, peak concentration, time to peak, and effective width of the automatically measured AIFs or VOFs were comparable to that were measured manually. CONCLUSION: The proposed automatic measurement technique successfully overcomes the motion artifact and random noise problems encountered in measuring AIF and VOF. It can be easily integrated into software for the automatic calculation of cerebral blood volume and flow.

Evaluation of dose distribution of molecular delivery after blood-brain barrier disruption by focused ultrasound with treatment planning.

The permeability of the blood-brain barrier (BBB) can be enhanced by focused ultrasound (FUS) in localized regions with applications of ultrasound contrast agent (UCA). The purpose of this study was to evaluate the dose distribution of Evans blue (EB) in the targeted brain by sonication with treatment strategy. FUS exposure was applied with an ultrasound frequency of 1 MHz, a 5% duty cycle and a repetition frequency of 1 Hz. Single sonication with two doses of UCA and two sonications at the same location or an interval of 3 mm to induce BBB disruption for assessing dose distribution. The permeability of the BBB was measured quantitatively based on EB extravasation. Gadolinium deposition was monitored by contrast enhanced MR imaging for dose distribution of the focal plane. Hematoxylin and eosin staining was performed for histologic observation. No significant difference was found for EB in the focal regions between the single sonication with UCA at a dose of 300 µL/kg and repeated sonication with UCA at a lower dose of 150 µL/kg. There was a sharper dose distribution in the brain with repeated sonication at the same location, compared with the brain receiving two sonications at an interval of 3 mm. Compared with a single sonication with UCA at a dose of 150 µL/kg, the histologic evaluation of the sonicated regions indicated that more erythrocytes were seen in the brain treated with single sonication at a higher dose of 300 µL/kg or repeated sonication at a dose of 150 µL/kg. This study demonstrated that the dose distribution of molecular delivery could be regulated by sonication with treatment planning.

Improvements in the quantitative assessment of cerebral blood volume and flow with the removal of vessel voxels from MR perfusion images.

OBJECTIVE: To improve the quantitative assessment of cerebral blood volume (CBV) and flow (CBF) in the brain voxels from MR perfusion images. MATERIALS AND METHODS: Normal brain parenchyma was automatically segmented with the time-to-peak criteria after cerebrospinal fluid removal and preliminary vessel voxel removal. Two scaling factors were calculated by comparing the relative CBV and CBF of the segmented normal brain parenchyma with the absolute values in the literature. Using the scaling factors, the relative values were converted to the absolute CBV and CBF. Voxels with either CBV > 8 mL/100 g or CBF > 100 mL/100 g/min were characterized as vessel voxels and were excluded from the quantitative measurements. RESULTS: The segmented brain parenchyma with normal perfusion was consistent with the angiographic findings for each patient. We confirmed the necessity of dual thresholds including CBF and CBV for proper removal of vessel voxels. The scaling factors were 0.208 ± 0.041 for CBV, and 0.168 ± 0.037, 0.172 ± 0.037 for CBF calculated using standard and circulant singular value decomposition techniques, respectively. CONCLUSION: The automatic scaling and vessel removal techniques provide an alternative method for obtaining improved quantitative assessment of CBV and CBF in patients with thromboembolic cerebral arterial disease.

Transfer function analysis of respiratory and cardiac pulsations in human brain observed on dynamic magnetic resonance images.

Magnetic resonance (MR) imaging provides a noninvasive, in vivo imaging technique for studying respiratory and cardiac pulsations in human brains, because these pulsations can be recorded as flow-related enhancement on dynamic MR images. By applying independent component analysis to dynamic MR images, respiratory and cardiac pulsations were observed. Using the signal-time curves of these pulsations as reference functions, the magnitude and phase of the transfer function were calculated on a pixel-by-pixel basis. The calculated magnitude and phase represented the amplitude change and temporal delay at each pixel as compared with the reference functions. In the transfer function analysis, near constant phases were found at the respiratory and cardiac frequency bands, indicating the existence of phase delay relative to the reference functions. In analyzing the dynamic MR images using the transfer function analysis, we found the following: (1) a good delineation of temporal delay of these pulsations can be achieved; (2) respiratory pulsation exists in the ventricular and cortical cerebrospinal fluid; (3) cardiac pulsation exists in the ventricular cerebrospinal fluid and intracranial vessels; and (4) a 180-degree phase delay or inverted amplitude is observed on phase images.

Change in brain perfusion after extracranial-intracranial bypass surgery detected using the mean transit time of computed tomography perfusion.

BACKGROUND: Cerebral perfusion can be evaluated using a computed tomography (CT) scan by intravenous bolus injection of contrast media. The purpose of this study was to investigate the value of CT perfusion (CTP) in follow-up of extracranial-intracranial (EC-IC) bypass surgery. METHODS: We retrospectively reviewed pre- and postoperative CTP studies in 14 patients who received EC-IC bypass surgery because of cerebral arterial occlusion or stenosis. Brain areas showing prolongation of the mean transit time (MTT) were automatically identified and quantitatively measured. RESULTS: All 14 patients showed MTT prolongation in the preoperative CTP study. In 13 patients, a reduction in brain volume with MTT prolongation was noted during postoperative CTP. These 13 patients had a patent EC-IC anastomosis, and 42 ± 21% of the brain area with MTT prolongation returned to normal MTT during CTP 7 ± 4 days (range 2-13 days) after surgery. On clinical follow up of 41 ± 16 months (range 14-60 months), no stroke or transient ischemic attack was noted after bypass surgery in these 13 patients. The brain volume with MTT prolongation did not decrease in just one patient whose EC-IC anastomosis was not patent, and the patient suffered a minor stroke during surgery. CONCLUSION: Quantitative results for the brain area with MTT prolongation were positively correlated with improvement in brain perfusion shown on MTT, EC-IC bypass patency, and patient outcome.

Validation and absolute quantification of MR perfusion compared with CT perfusion in patients with unilateral cerebral arterial stenosis.

OBJECTIVE: The aim of the study was to assess absolute quantification of dynamic susceptibility contrast-enhanced magnetic resonance perfusion (MRP) comparing with computed tomography perfusion (CTP) in patients with unilateral stenosis. MATERIALS AND METHODS: We retrospectively post-processed MRP in 20 patients with unilateral occlusion or stenosis of >79% at the internal carotid artery or the middle cerebral artery (MCA). Absolute quantification of MRP was performed after applying the following techniques: cerebrospinal fluid removal, vessel removal, and automatic segmentation of brain to calculate the scaling factors to convert relative cerebral blood volume (rCBV) and relative cerebral blood flow (rCBF) values to absolute values. For comparison between MRP and CTP, we manually deposited regions of interest in bilateral MCA territories at the level containing the body of the lateral ventricle. RESULTS: The correlation between MRP and CTP was best for mean transit time (MTT) (r=0.83), followed by cerebral blood flow (CBF) (r=0.52) and cerebral blood volume (CBV) (r=0.43). There was no significant difference between CTP and MRP for CBV, CBF, and MTT on the lesion side, the contralateral side, the lesion-contralateral differences, or the lesion-to-contralateral ratios (P>0.05). The mean differences between MRP and CTP were as follows: CBV -0.57 mL/100g, CBF 2.50 mL/100g/min, and MTT -0.90 s. CONCLUSION: Absolute quantification of MRP is possible. Using the proposed method, measured values of MRP and CTP had acceptable linear correlation and quantitative agreement.

Mesenchymal stem cell-conditioned medium facilitates angiogenesis and fracture healing in diabetic rats.

The most critical factor for fracture union is the blood supply to the fracture site, which is usually impaired in patients with diabetes. Recently, mesenchymal stem cells-derived conditioned medium (MSC-CM) has shown significantly higher levels of angiogenic factors, such as VEGF and IL-6. We demonstrate in this report that MSC-CM delivered in gelatin sponges stimulates angiogenesis and promotes fracture healing in a diabetic rat model. Subcutaneous implantation of gelatin sponges soaked in MSC-CM demonstrated better tissue ingrowth and higher capillary densities at 2 and 3 weeks than gelatin sponges in minimal essential medium (MEM) or 293 cell-derived conditioned medium (293-CM). Implantation of fibular defects with gelatin sponges soaked in MSC-CM enhanced bone ingrowth and fracture healing rates compared to 293-CM and MEM groups at 8 weeks. Micro-computed tomography analysis further indicated a higher new bone volume in the MSC-CM group compared to the other diabetic groups. Histological analysis with CD31 immunostaining also revealed that MSC-CM increased endothelial cell counts compared to the other groups. Together, these results indicated that gelatin sponges used to deliver MSC-CM promote angiogenesis and fracture healing in a diabetic model and may be an alternative strategy for treating fracture non-union in patients with diabetes.

Selection of arterial input function for postprocessing of cerebral ct perfusion in chronic unilateral high-grade stenosis or occlusion of the carotid or middle cerebral artery.

RATIONALE AND OBJECTIVES: We evaluated the effect of the arterial input function (AIF) on computed tomography perfusion (CTP) in patients with unilateral high-grade stenosis or occlusion in the carotid artery or middle cerebral artery without acute stroke. MATERIALS AND METHODS: CTP datasets were retrospectively postprocessed using the same venous output function and different AIF selections: the second segment of the anterior cerebral artery (A2 AIF), the second segment of the middle cerebral artery (MCA) on the lesion side (affected M2 AIF), and M2 on the contralateral side (nonaffected M2 AIF). We measured CTP values in the region of interest (ROI) in the bilateral MCA territory and evaluated the lesion-to-contralateral ratios. RESULTS: The mean and standard deviations of cerebral blood flow (CBF) on the normal side were similar to previously reported data only when using "non-affected M2 AIF." Selecting an "affected M2 AIF" overestimated the CBF and shortened the mean transit time (MTT) in normal and lesion areas. Selecting an "A2 AIF" may cause overestimation of CBF in the normal side in patients with nonaffected-side A1 hypoplasia or occlusion. The sensitivity of the CBF ratio or MTT ratio to detect these unilateral cerebrovascular diseases was 100% using "nonaffected M2 AIF for bilateral MCA ROIs" and 70% (CBF ratio) and 90% (MTT ratio) using "respective AIF." CONCLUSION: The use of "nonaffected AIF for the bilateral MCA ROIs" was found to be the best of these AIF-ROI combinations in patients with chronic unilateral carotid or M1 severe stenosis or occlusion.

Hemodynamic segmentation of MR perfusion images in patients with unilateral carotid stenosis using independent component analysis.

PURPOSE: To assess spatiotemporal patterns of local perfusion in MR brain perfusion images for patients with unilateral carotid stenosis. MATERIALS AND METHODS: MR perfusion images acquired from 12 patients with unilateral carotid stenosis were retrospectively segmented using independent component analysis. Regions of interest selected from the segmentation results were used to measure the time to peak (TTP), time to maximum of the residue curve (Tmax), and mean transit time (MTT) for arteries and brain parenchyma on normal and stenotic sides. RESULTS: The tissue types that can be identified in segmentation results include normal artery, artery with proximal stenosis, normal brain parenchyma, delayed-perfusion brain parenchyma, vein and sinus, choroid plexus, cerebrospinal fluid, and leukoaraiosis. Concentration-time curves measured on normal and stenotic artery regions can be modeled as two arterial input functions. Unilateral carotid stenosis associated with either middle cerebral artery stenosis or poor collateral circulation at the circle of Willis resulted in increased differences of brain parenchyma TTP, Tmax, and MTT between normal and stenotic sides. CONCLUSION: Independent component analysis on perfusion images of patients with unilateral carotid stenosis provides useful spatiotemporal information regarding blood supply to arteries and local perfusion of brain parenchyma.

Spoiled gradient-echo as an arterial spin tagging technique for quick evaluation of local perfusion.

PURPOSE: To introduce a simple gradient-echo arterial spin tagging (GREAST) technique available for most commercial magnetic resonance (MR) systems, for a quick evaluation of tissue perfusion. MATERIALS AND METHODS: The GREAST technique uses a combination of a short TR spoiled gradient-echo (SPGR) sequence with a selective presaturation radio frequency (RF) pulse that allows acquiring each tagged and control image within 10-20 seconds. The phantom and human studies were performed for evaluating the feasibility in measurement of local perfusion and the efficacy in alleviation of the asymmetric magnetization transfer (MT) and slice profile effects. RESULTS: Results show a good linear relationship between the signal attenuation caused by the presaturation pulse and flow rates in the phantom experiment and effective alleviation of the asymmetric MT and slice profile effects for various orientations of imaging slices. Human studies showed good perfusion results in brain imaging. Perfusion imaging on the liver and kidney were also conducted. The results could be significantly improved by effectively lessening motion-related artifacts. CONCLUSION: The GREAST technique is simple, easy to use, and applicable to examine local perfusion of the brain and other organs in the trunk.