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[IEEE 2018 IEEE International Ultrasonics Symposium (IUS) - Kobe, Japan (2018.10.22-2018.10.25)] 2018 IEEE International Ultrasonics Symposium (IUS) - Looking at the Skull in a New Light: Rayleigh-Lamb Waves in Cranial Bone
摘要： Current knowledge on the ultrasound wave propagation in the cranial bone is restricted to far-field observations. In order to extend our understanding on how ultrasound waves propagate in the skull, we use short laser pulses to excite ultrasound waves in water-immersed ex vivo mouse and human skulls and explored their near-field. The laser pulses ( 10 ns duration) of 532 nm are absorbed by a small layer of black burnish deposited on the skull’s inner surface and generate ultrasound waves due to the thermoelastic effect. The acoustic near-field is mapped using a needle hydrophone close to the skull surface, following a three-dimensional scanning path derived from a previous pulse-echo scan of the skull with a spherically focused ultrasound transducer. The results for mouse and human skulls show different wave propagation regimes according to their differences in size, thickness, and internal structure. Leaky and non-leaky waves have been observed for both skull samples. Zero order Lamb modes were observed in the mouse skull, whereas Rayleigh-Lamb higher order modes can be observed in the human skull sample, presumably propagating in the outer cortical bone layer. Good agreement is found between the experiments and the multilayered flat plate model.
关键词： Skull Bone,Lamb Waves,Near Field,Surface Acoustic Waves,Rayleigh Waves,Plate waves,Laser ultrasonics
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE International Conference on Imaging Systems and Techniques (IST) - Krakow, Poland (2018.10.16-2018.10.18)] 2018 IEEE International Conference on Imaging Systems and Techniques (IST) - A Novel MRA-Based Framework For Detecting Correlation Between Cerebrovascular Changes and Mean Arterial Pressure
摘要： Systemic hypertension is a signi?cant contributor for strokes and cognitive impairment and is a leading cause of mortality in the USA. Changes in cerebral vascular diameter and cerebral perfusion pressure have been reported to precede elevation of systemic blood pressures. A novel, non-invasive Time-of-Flight - Magnetic Resonance Angiography (TOF-MRA) based framework for detection of cerebrovascular changes is presented. The proposed framework analyzes brain TOF-MRA data to quantify changes in cerebral vascular diameter and cerebral perfusion pressure. The framework has three major steps: 1) Adaptive segmentation to extract large and small diameter cerebral vessels from TOF-MRA images using both appearance and 3-D spatial information of the vascular system; 2) Estimation of the Cumulative Distribution Function (CDF) of the 3-D distance map of the cerebral vascular system, which represents the changes in diameter of the 3-D vascular system ; and 3) Statistical and correlation analysis that measured the effect of Mean Arterial Pressure (MAP) on blood vessels’ diameter changes. The ef?cacy of the framework was evaluated using MRA images and blood pressure (BP) measurements obtained from 15 patients (M=8, F=7, Age=49.2±7.3 years) on Day 0 and Day 700. The framework had a dice similarity coef?cient of 92.23%, a sensitivity of 94.8% and a speci?city of ～ 99% in detecting elevated vascular pressures compared to ground truth. Statistical analysis demonstrated an inverse relationship between blood vessels diameters and MAP. This correlation was valid for both upper (above the circle of Willis) and lower (circle of Willis and below) sections of the brain. The proposed methodology may be used to quantify changes in cerebral vasculature and cerebral perfusion pressure non-invasively through MRA image analysis, which may be a useful tool for clinicians to optimize medical management of pre-hypertension and hypertension.
关键词： Vessel Diameter,Skull Stripping,CDF,Automatic Segmentation,Mean Arterial Pressure,Blood Vessels,MRA,Hypertension,Median Vascular Radius
更新于2025-09-23 15:22:29
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Penetration Profiles of Visible and Near-Infrared Lasers and Light-Emitting Diode Light Through the Head Tissues in Animal and Human Species: A Review of Literature
摘要： Background and objective: Photobiomodulation (PBM) therapy is a promising and noninvasive approach to stimulate neuronal function and improve brain repair. The optimization of PBM parameters is important to maximize effectiveness and tolerability. Several studies have reported on the penetration of visible-to-near-infrared (NIR) light through various animal and human tissues. Scientific findings on the penetration of PBM light vary, likely due to use of different irradiation parameters and to different characteristics of the subject such as species, age, and gender. Materials and methods: In this article, we review published data on PBM penetration through the tissues of the head in both animal and human species. The patterns of visible-to-NIR light penetration are summarized based on the following study specifications: wavelength, coherence, operation mode, beam type and size, irradiation site, species, age, and gender. Results: The average penetration of transcranial red/NIR (630–810 nm) light ranged 60–70% in C57BL/6 mouse (skull), 1–10% in BALB/c mouse (skull), 10–40% in Sprague–Dawley rats (scalp plus skull), 20% in Oryctolagus cuniculus rabbit (skull), 0.11% in pig (scalp plus skull), and 0.2–10% in humans (scalp plus skull). The observed variation in the reported values is due to the difference in factors (e.g., wavelengths, light coherence, tissue thickness, and anatomic irradiation site) used by researchers. It seems that these data challenge the applicability of the animal model data on transcranial PBM to humans. Nevertheless, two animal models seem particularly promising, as they approximate penetration in humans: (I) Penetration of 808 nm laser through the scalp plus skull was 0.11% in the pig head; (II) Penetration of 810 nm laser through intact skull was 1.75% in BALB/c mouse. Conclusions: In conclusion, it is worthwhile mentioning that since the effectiveness of brain PBM is closely dependent on the amount of light energy reaching the target neurons, further quantitative estimation of light penetration depth should be performed to validate the current findings.
关键词： optical properties,penetration depth,skull,low-level laser (light) therapy,brain tissues,transcranial photobiomodulation
更新于2025-09-12 10:27:22
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In vivo monitoring blood-brain barrier permeability using spectral imaging through optical clearing skull window
摘要： The blood–brain barrier (BBB) plays a key role in the health of the central nervous system. Opening the BBB is very important for drug delivery to brain tissues to enhance the therapeutic effect on brain diseases. It is necessary to in vivo monitor the BBB permeability for assessing drug release with high resolution; however, an effective method is lacking. In this work, we developed a new method that combined spectral imaging with an optical clearing skull window to in vivo dynamically monitor BBB opening caused by 5-aminolevulinic acid (5-ALA)-mediated photodynamic therapy (PDT), in which the Evans blue dye (EBd) acted as an indicator of the BBB permeability. Using this method, we effectively monitored the cerebrovascular EBd leakage process. Moreover, the analysis of changes in the vascular and extravascular EBd concentrations demonstrated that the PDT-induced BBB opening exhibited spatiotemporal differences in the cortex. This spectral imaging method based on the optical clearing skull window provides a low-cost and simply-operated tool for in vivo monitoring BBB opening process. This has a high potential for the visualization of drug delivery to the central nervous system. Thus, it is of tremendous significance in brain disease therapy.
关键词： spectral imaging,blood-brain barrier,skull optical clearing,in vivo optical imaging
更新于2025-09-10 09:29:36
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Utility of first positron emission tomography-computed tomography scan as a prognostic tool following treatment of sinonasal and skull base malignancies
摘要： Background: The prognostic value of the first posttreatment whole body integrated positron emission tomography-computed tomography (PET/CT) scanning in patients with sinonasal/skull base malignancies is undetermined. Methods: We retrospectively reviewed the data of all patients that underwent surgery for sinonasal/skull base malignancies in 2000-2015. The results of the pretreatment and posttreatment PET/CT findings and the clinical course were retrieved. Results: Thirty-eight patients (average age 60.6 years, 20 males) were included. Sensitivity and specificity, positive predictive value, and negative predictive value of the first PET/CT scan for predicting persistent/recurrent disease were 85.7%, 87.5%, 80%, and 91.3%, respectively. Overall 5-year survival was significantly lower in the first posttreatment PET/CT-positive group (35%) compared to the PET/CT-negative group (93%) (P = .0008). Conclusion: Posttreatment PET/CT findings are highly prognostic in patients with sinonasal/skull base malignancies. Negative findings on the first posttreatment PET/CT scan predict a significantly better overall survival.
关键词： sinonasal malignancy,skull base,prognosis,PET/CT,survival
更新于2025-09-09 09:28:46