Thin Skull Research Articles

Luckenschadel Associated with Chiari Type II Malformation: An Autopsy Case Report

Background Luckenschadel is commonly associated with Chiari II malformation and myelomeningocele. The aim of this case report was to revisit this entity. Case report: Antenatal imaging performed at 32 weeks gestation showed severe hydrocephalus with brain parenchymal thinning, cerebellar hypoplasia and lumbar myelomeningocele, suggestive of Chiari type II malformation. Stillbirth occurred before the pregnancy termination. X-rays showed a characteristic honeycomb appearance of the skull. The female 34-week-old stillborn was severely macerated and presented with thin and fenestrated skull, ruptured lumber myelomeningocele and diastematomyelia. Hydrocephalus could not be confirmed because of cerebral maceration. Histological examination did not reveal any significant visceral alteration. Conclusion: This case report highlights two key points. Luckenschadel should be kept in mind when Chiari II malformation is diagnosed. Autopsy with radiographic assessment is very useful in revealing this congenital defect which may escape prenatal detection.

Modified Frameless Stereotactic System for Intracerebral Delivery of Viral Vector in Young Children.

Stereotaxic surgery for viral vector delivery in young children is highly challenging because of their small cranial size, thin and fragile skull, and deformity of the skull or brain after prolonged bed ridden condition. To develop a modified frameless stereotactic system especially suitable for intracerebral delivery of viral vector in young children for accurate localization of intracerebral targets during stereotactic surgery. A modified frameless stereotactic system was developed for intracerebral delivery of viral vector in pediatric patients with congenital enzyme deficiency. Localization markers and a stereotactic stabilizer were designed specifically for surgery in pediatric patients, and this equipment is used along with a pre-existing frameless stereotactic and computer-assisted planning and navigation system. We applied this modified frameless stereotactic system to treat 10 children with aromatic L-amino acid decarboxylase deficiency. It is potentially suitable for stereotactic functional neurosurgery in pediatric patients as young as 1 yr and 8 mo of age.

μECoG Recordings Through a Thinned Skull.

The studies described in this paper for the first time characterize the acute and chronic performance of optically transparent thin-film micro-electrocorticography (μECoG) grids implanted on a thinned skull as both an electrophysiological complement to existing thinned skull preparation for optical recordings/manipulations, and a less invasive alternative to epidural or subdurally placed μECoG arrays. In a longitudinal chronic study, μECoG grids placed on top of a thinned skull maintain impedances comparable to epidurally placed μECoG grids that are stable for periods of at least 1 month. Optogenetic activation of cortex is also reliably demonstrated through the optically transparent μECoG grids acutely placed on the thinned skull. Finally, spatially distinct electrophysiological recordings were evident on μECoG electrodes placed on a thinned skull separated by 500–750 μm, as assessed by stimulation evoked responses using optogenetic activation of cortex as well as invasive and epidermal stimulation of the sciatic and median nerve at chronic time points. Neural signals were collected through a thinned skull in mice and rats, demonstrating potential utility in neuroscience research applications such as in vivo imaging and optogenetics.

Risks to Health and Well-Being From Radio-Frequency Radiation Emitted by Cell Phones and Other Wireless Devices.

Radiation exposure has long been a concern for the public, policy makers, and health researchers. Beginning with radar during World War II, human exposure to radio-frequency radiation1 (RFR) technologies has grown substantially over time. In 2011, the International Agency for Research on Cancer (IARC) reviewed the published literature and categorized RFR as a “possible” (Group 2B) human carcinogen. A broad range of adverse human health effects associated with RFR have been reported since the IARC review. In addition, three large-scale carcinogenicity studies in rodents exposed to levels of RFR that mimic lifetime human exposures have shown significantly increased rates of Schwannomas and malignant gliomas, as well as chromosomal DNA damage. Of particular concern are the effects of RFR exposure on the developing brain in children. Compared with an adult male, a cell phone held against the head of a child exposes deeper brain structures to greater radiation doses per unit volume, and the young, thin skull's bone marrow absorbs a roughly 10-fold higher local dose. Experimental and observational studies also suggest that men who keep cell phones in their trouser pockets have significantly lower sperm counts and significantly impaired sperm motility and morphology, including mitochondrial DNA damage. Based on the accumulated evidence, we recommend that IARC re-evaluate its 2011 classification of the human carcinogenicity of RFR, and that WHO complete a systematic review of multiple other health effects such as sperm damage. In the interim, current knowledge provides justification for governments, public health authorities, and physicians/allied health professionals to warn the population that having a cell phone next to the body is harmful, and to support measures to reduce all exposures to RFR.

Intravital microscopy: Imaging host-parasite interactions in the brain.

Intravital fluorescence microscopy (IVM) is a powerful technique for imaging multiple organs, including the brain of living mice and rats. It enables the direct visualisation of cells in situ providing a real-life view of biological processes that in vitro systems cannot. In addition, to the technological advances in microscopy over the last decade, there have been supporting innovations in data storage and analytical packages that enable the visualisation and analysis of large data sets. Here, we review the advantages and limitations of techniques predominantly used for brain IVM, including thinned skull windows, open skull cortical windows, and a miniaturised optical system based on microendoscopic probes that can be inserted into deep tissues. Further, we explore the relevance of these techniques for the field of parasitology. Several protozoan infections are associated with neurological symptoms including Plasmodium spp., Toxoplasma spp., and Trypanosoma spp. IVM has led to crucial findings on these parasite species, which are discussed in detail in this review.

Association of AHI and Other Patient Factors with Calvarial Thickness

Background and Hypothesis: Temporal spontaneous cerebrospinal fluid (sCSF) leaks occur when spinal fluid leaks through defects in the skull base bone. Patients with sCSF leaks have approximately 22% thinner skulls but no change in extracranial bone thickness, suggesting an intracranial process causes skull thinning and the development of sCSF leaks. Approximately 83% of sCSF leak patients have obstructive sleep apnea (OSA) as measured by the apnea-hyponea index (AHI) and OSA is associated with spikes in intracranial pressure. We hypothesize that AHI is associated with isolated skull thinning in the general population. 
 Experimental Design: High resolution head CT images from patients with diagnostic sleep studies at IU health from 2010 to 2017 were analyzed (IRB approved) using 3D slicer to measure skull thickness of the squamous temporal bone. Age, body mass index (BMI), race and diabetes recorded. Mixed model analysis was used to determine the effect of a number of factors on skull thickness. 
 Results: 344 CT scans were analyzed. Increased AHI was significantly associated with thinning of the calvarium [2.68 mm - 0.003x, (x = AHI point) P<0.02], while thickening of the calvarium was associated with age [CI = 0.005 to 0.011 per year, P<0.001] and BMI [CI = 0.003 to 0.015 per mg/kg2, P<0.003]. Female gender (P=0.016) and diabetes (P=0.005) were linked to thickening of the calvarium. Hypertension had no effect on calvarial and zygoma thickness (P=0.244 and 0.575, respectively). The extracranial zygoma thickness was not associated with AHI (P=0.54) or BMI (P=0.811) but the zygoma thinned significantly with age [CI = -0.01 to - 0.002, P<0.002] and female gender (P<0.001). 
 Conclusion and Potential Impact: OSA is associated with skull thinning and may play a pathologic role in the development of sCSF leaks over time.

Methodologic recommendations and possible interpretations of video-EEG recordings in immaturerodents used as experimental controls: ATASK1-WG2 report of the ILAE/AES Joint TranslationalTask Force.

SummaryThe use of immature rodents to study physiologic aspects of cortical development requires high‐quality recordings electroencephalography (EEG) with simultaneous video recording (vEEG) of behavior. Normative developmental vEEG data in control animals are fundamental for the study of abnormal background activity in animal models of seizures or other neurologic disorders. Electrical recordings from immature, freely behaving rodents can be particularly difficult because of the small size of immature rodents, their thin and soft skull, interference with the recording apparatus by the dam, and other technical challenges. In this report of the TASK1 Working Group 2 (WG2) of the International League Against Epilepsy/American Epilepsy Society (ILAE/AES) Joint Translational Task Force, we provide suggestions that aim to optimize future vEEG recordings from immature rodents, as well as their interpretation. We focus on recordings from immature rodents younger than 30 days old used as experimental controls, because the quality and correct interpretation of such recordings is important when interpreting the vEEG results of animals serving as models of neurologic disorders. We discuss the technical aspects of such recordings and compare tethered versus wireless approaches. We also summarize the appearance of common artifacts and various patterns of electrical activity seen in young rodents used as controls as a function of behavioral state, age, and (where known) sex and strain. The information herein will hopefully help improve the methodology of vEEG recordings from immature rodents and may lead to results and interpretations that are more consistent across studies from different laboratories.

Observation of Guided Acoustic Waves in a Human Skull

Human skull poses a significant barrier for the propagation of ultrasound waves. Development of methods enabling more efficient ultrasound transmission into and from the brain is therefore critical for the advancement of ultrasound-mediated transcranial imaging or actuation techniques. We report on the first observation of guided acoustic waves in the near field of an ex vivo human skull specimen in the frequency range between 0.2 and 1.5MHz. In contrast to what was previously observed for guided wave propagation in thin rodent skulls, the guided wave observed in a higher-frequency regime corresponds to a quasi-Rayleigh wave, confined mostly to the cortical bone layer. The newly discovered near-field properties of the human skull are expected to facilitate the development of more efficient diagnostic and therapeutic techniques based on transcranial ultrasound.

Intravital Imaging of Neuroimmune Interactions Through a Thinned Skull.

Innate and adaptive immune interactions within the central nervous system (CNS) and surrounding meninges contribute significantly to neural homeostasis as well as a variety of different neurological disorders. Two-photon laser scanning microscopy is a deep tissue imaging technique that provides a means to image immune cell dynamics and interactions in the living CNS with high spatial and temporal resolution. Optical access to the brain and meninges can be achieved through the creation of thinned skull windows, which can be made without inducing damage and inflammation in the underlying tissue. This protocol provides guidance on how to create a thinned skull window without causing CNS injury. We also describe a highly reproducible method to induce a mild traumatic brain injury using the thinned skull approach. © 2018 by John Wiley & Sons, Inc.

Advanced Pediatric Neurosonography Techniques: Contrast-Enhanced Ultrasonography, Elastography, and Beyond.

Recent technical advances in neurosonography continue broadening the diagnostic utility, sensitivity, and specificity of ultrasound for detecting intracranial abnormalities bed side. The clinical and functional applications of neurosonography have significantly expanded since the 1980s when transcranial Doppler sonography first allowed anatomic and hemodynamic delineation of the intracranial vessels through the thin temporal skull. In the past few years, contrast-enhanced ultrasonography, elastography, 3D/4D reconstruction tools, and high-resolution microvessel imaging techniques have further enhanced the diagnostic significance of neurosonography. Given these advances, a thorough familiarity with these new techniques and devices is crucial for a successful clinical application allowing improved patient care. It is essential that future neurosonography studies compare these advanced techniques against the current "gold standard" computed tomography and magnetic resonance imaging to assure the accuracy of their diagnostic potential. This review will provide a comprehensive update on currently available advanced neurosonography techniques.

Psycholegal Assessment of Co-occurring Chronic Pain and Schizophrenia Post-MVC: Analysis of Causation Using Two Case Examples

The key aspect of any psycholegal assessment is the analysis of causation, which requires consideration of important legal constructs such as the but for test, material contribution test, thin skull, and crumbling skull. An analysis of causation can be especially helpful in determining overall liability when evaluating the impact of two major co-occurring conditions. This paper focuses on the utility of conducting an analysis of causation using two case examples in which chronic pain and schizophrenia co-occurred following a motor vehicle collision (MVC). Collision-related injuries often lead to the development of chronic pain and could result in permanent and serious impairment and disability. Schizophrenia is a rare psychological occurrence in the collision context and is associated with its own unique and overwhelming physical, psychological, and cognitive challenges. In the psycholegal context, evaluating the impact of two major co-occurring conditions can be problematic and lead to conceptual challenges. In the two cases presented, some assessors attributed nearly all post-collision changes to schizophrenia as if it were pre-existing or in a latent state and failed to assess or even consider the contribution of MVC-related sequelae to the onset of schizophrenia. As part of addressing these conceptual challenges, we present a model of psycholegal assessment that takes into account the pre-, peri- and post-MVC variables that best explain the occurrence of these two conditions. The model also allows the assessor to determine the current and future needs of injured persons, the permanent physical, psychological, and cognitive sequelae that impact quality of life and/or work, and prognosis for the near and distant future.

Traumatic Head Injury in Pediatric Head Trauma

The cause of the traumatic head injury (THI) and the capacity of the brain to respond to trauma depend on the age of the patient. The most common abnormality seen in newborns after birth trauma is the subdural hematoma, which is usually posteriorly located, caused by tearing of the tentorium and venous structures after difficult delivery. At this age, intradural hematomas may occur within the opposing layers of the falx and tentorium, which are loosely attached. Doctors should be aware of complications such as intraparenchymal hemorrhage, subarachnoidal hemorrhage (in this case, hydrocephalus may follow), epidural hematomas and fractures. Children under 2 years of age, particularly small infants, have large heads, weak neck muscles, thin and deformable skull and nonfused sutures. This last feature leads to a greater degree of intracranial expansion. In case of cerebral swelling, the calvarium expands, but the brain does not herniate infratentorially. However, the perimesencephalic cistern can be obliterated and the brain stem compressed. In addition, the lack of myelination makes the parenchyma more compressible and permits, at least partially, the absorption of impact. As a consequence, less damage occurs. The same unmyelinated white matter is however unfortunately sensitive to shearing injury, i.e., diffuse axonal injury (DAI). In addition, exclusive to this age group is the risk of a growing skull fracture. A further complication after THI in all age-groups with fractures and associated dura laceration is meningitis. After the age of 2, and especially within adolescents, DAI is more common and results from stress to axons during severe trauma, such as may occur in a motor vehicle accident. DAI is always multiple, regardless whether or not magnetic resonance imaging (MRI) recognizes more than one lesion. In this group, computed tomography (CT) and MRI findings do not differ from those seen in the adult population.

Collateral blood flow in different cerebrovascular hierarchy provides endogenous protection in cerebral ischemia.

Collateral blood flow as vascular adaptions to focal cerebral ischemia is well recognized. However, few studies directly investigate the dynamics of collateral vessel recruitment in vivo and little is known about the effect of collateral blood flow in different cerebrovascular hierarchy on the neuropathology after focal ischemic stroke. Here, we report that collateral blood flow is critically involved in blood vessel compensations following regional ischemia. We occluded a pial arteriole using femtosecond laser ablating under the intact thinned skull and documented the changes of collateral flow around the surface communication network and between the surface communication network and subsurface microcirculation network using in vivo two photon microscopy imaging. Occlusion of the pial arteriole apparently increased the diameter and collateral blood flow of its leptomeningeal anastomoses, which significantly reduced the cortical infarction size. This result suggests that the collateral flow via surface communicating network connected with leptomeningeal anastomoses could greatly impact on the extent of infarction. We then further occluded the target pial arteriole and all of its leptomeningeal anastomoses. Notably, this type of occlusion led to reversals of blood flow in the penetrating arterioles mainly proximal to the occluded pial arteriole in a direction from the subsurface microcirculation network to surface arterioles. Interesting, the cell death in the area of ischemic penumbra was accelerated when we performed occlusion to cease the reversed blood flow in those penetrating arterioles, suggesting that the collateral blood flow from subsurface microcirculation network exerts protective roles in delaying cell death in the ischemic penumbra. In conclusion, we provide the first experimental evidence that collateral blood vessels at different cerebrovascular hierarchy are endogenously compensatory mechanisms in brain ischemia.

Optic-nerve-transmitted eyeshine, a new type of light emission from fish eyes

BackgroundMost animal eyes feature an opaque pigmented eyecup to assure that light can enter from one direction only. We challenge this dogma by describing a previously unknown form of eyeshine resulting from light that enters the eye through the top of the head and optic nerve, eventually emanating through the pupil as a narrow beam: the Optic-Nerve-Transmitted (ONT) eyeshine. We characterize ONT eyeshine in the triplefin blenny Tripterygion delaisi (Tripterygiidae) in comparison to three other teleost species, using behavioural and anatomical observations, spectrophotometry, histology, and magnetic resonance imaging. The study’s aim is to identify the factors that determine ONT eyeshine occurrence and intensity, and whether these are specifically adapted for that purpose.ResultsONT eyeshine intensity benefits from locally reduced head pigmentation, a thin skull, the gap between eyes and forebrain, the potential light-guiding properties of the optic nerve, and, most importantly, a short distance between the head surface and the optic nerves.ConclusionsThe generality of these factors and the lack of specifically adapted features implies that ONT eyeshine is widespread among small fish species. Nevertheless, its intensity varies considerably, depending on the specific combination and varying expression of common anatomical features. We discuss whether ONT eyeshine might affect visual performance, and speculate about possible functions such as predator detection, camouflage, and intraspecific communication.

W sidłach prawa : tłumacz prawniczy w obliczu metafor

Thin skull doctrine, living tree, blue-sky law, clean hands, cloud on title… Metaphors play a very important role in the English legal language. How can we explain the popularity of metaphors in legal langauge of common law? Metaphors help understand abstract concepts thanks to pictueresque and well known images. This function of metaphors will be discussed in this paper. Having reviewed two groups of metaphors in the English legal language (called in French les metaphores corporelles and les metaphores «naturelles»), the author thouches upon the problems connected with their translation. It is concluded that apart from the most popular translation method (adaptation of metaphors due to the more abstract nature of the French language), other translation may be applied as well including literal translation. The author analyzes certain metaphors in respect of which literal translation may be applied.

Scattering compensation by focus scanning holographic aberration probing (F-SHARP)

A long-standing goal in biomedical imaging, the control of light inside turbid media, requires knowledge of how the phase and amplitude of an illuminating wavefront are transformed as the electric field propagates inside a scattering sample onto a target plane. So far, it has proved challenging to non-invasively characterize the scattered optical wavefront inside a disordered medium. Here, we present a non-invasive scattering compensation method, termed F-SHARP, which allows us to measure the scattered electric-field point spread function (E-field PSF) in three dimensions. Knowledge of the phase and amplitude of the E-field PSF makes it possible to optically cancel sample turbulence. We demonstrate the imaging capabilities of this technique on a variety of samples and notably through vertebrate brains and across thinned skull in vivo. A non-invasive scattering compensation method, termed F-SHARP, gives direct access to the phase and amplitude of the electric-field point spread function, enabling fast and high-resolution correction of aberrations and scattering in living tissue.

30 Evolution of cerebrovascular changes in mouse cortex during normal pregnancy by in vivo two-photon imaging

Introduction Past studies have shown that cerebral autoregulation is a physiologic process that maintains blood flow at an appropriate level. Impairment of cerebral autoregulation during pregnancy may contribute to further diseases like preeclampsia and eclampsia. However, little is known about the normative cerebrovascular adaptation during pregnancy. Objectives In the present study we observed adaptive changes in the blood flow and vessel diameter from prepregnancy to late pregnancy by in vivo two-photon imaging. Methods 12 female C57 mice were randomly divided into four groups: non-pregnancy, early-pregnancy, middle-pregnancy, late pregnancy. After the animals were anesthetized, a mouse head holder was used to hold the head. A thinned skull window was made (1–2 mm in diameter) over the motor cortex. One day later, Rhodamin B dissolved in saline (3 mg/ml, 0.2 ml/20 kg) was injected intraperitoneally to label the vessels 15 min before beginning the imaging experiments. The animal was anesthetized and placed under two photon microscope to observe; blood flow signal pictures were taken using line-scan and analyzed by blood flow analysis software programmed. Results The blood flow velocity of arteriovenous vessels and capillaries increased significantly in middle and late pregnancy compared to non-pregnancy and early-pregnancy; vascular diameters in middle and late pregnancy also became bigger than that in non-pregnancy and early-pregnancy. Conclusions Both the blood flow velocity and diameter of cortical micro vessels increased significantly from non-pregnancy and early-pregnancy to middle and late pregnancy. Such results demonstrated a progressive cerebrovascular adaptation from prepregnancy to late pregnancy.

512-Channel and 13-Region Simultaneous Recordings Coupled with Optogenetic Manipulation in Freely Behaving Mice.

The development of technologies capable of recording both single-unit activity and local field potentials (LFPs) over a wide range of brain circuits in freely behaving animals is the key to constructing brain activity maps. Although mice are the most popular mammalian genetic model, in vivo neural recording has been traditionally limited to smaller channel count and fewer brain structures because of the mouse’s small size and thin skull. Here, we describe a 512-channel tetrode system that allows us to record simultaneously over a dozen cortical and subcortical structures in behaving mice. This new technique offers two major advantages – namely, the ultra-low cost and the do-it-yourself flexibility for targeting any combination of many brain areas. We show the successful recordings of both single units and LFPs from 13 distinct neural circuits of the mouse brain, including subregions of the anterior cingulate cortices, retrosplenial cortices, somatosensory cortices, secondary auditory cortex, hippocampal CA1, dentate gyrus, subiculum, lateral entorhinal cortex, perirhinal cortex, and prelimbic cortex. This 512-channel system can also be combined with Cre-lox neurogenetics and optogenetics to further examine interactions between genes, cell types, and circuit dynamics across a wide range of brain structures. Finally, we demonstrate that complex stimuli – such as an earthquake and fear-inducing foot-shock – trigger firing changes in all of the 13 brain regions recorded, supporting the notion that neural code is highly distributed. In addition, we show that localized optogenetic manipulation in any given brain region could disrupt network oscillations and caused changes in single-unit firing patterns in a brain-wide manner, thereby raising the cautionary note of the interpretation of optogenetically manipulated behaviors.

Association between Lateral Skull Base Thickness and Surgical Outcomes in Spontaneous CSF Otorrhea.

(1) Correlate skull base thickness with perioperative outcomes for spontaneous cerebrospinal fluid (CSF) otorrhea. (2) Augment perioperative counseling of patients with abnormally thin skull bases. Case series with chart review. Tertiary center. Patients with spontaneous CSF otorrhea have thin skull bases. This is associated with obesity and/or idiopathic intracranial hypertension. The influence of skull base thinning on perioperative outcomes is unknown. A retrospective review was conducted from 2004 to 2014. Forty-eight cases of spontaneous CSF otorrhea met the inclusion criteria of primary surgery by the senior authors: preoperative dedicated temporal bone computed tomography, absence of other leak etiologies, and follow-up >6 months. Patients were stratified into thin (<0.9 mm) and thick (>0.9 mm) groups based on computed tomography measures of their tegmen. Primary outcomes measures were as follows: postoperative meningitis, recurrent leak, second site leak (contralateral ear/anterior fossa), and permanent shunt placement. Hearing outcomes were not assessed in this study. Thirty and 15 patients composed the thin and thick groups, respectively. Both the incidence (P < .0001) and the rate (P = .005) of adverse outcomes were significantly higher in the thin group. Only 2 patients in the thick group experienced an adverse outcome. Eleven patients underwent multiple procedures for spontaneous leaks. The recurrence rate was 14.5%. All but 1 recurrence occurred in the thin group. An abnormally thin tegmen was significantly associated with adverse perioperative outcomes in cases of spontaneous CSF otorrhea. A thick skull base and the presence of an encephalocele may be protective against recurrence. The effect of untreated intracranial hypertension on the results is unknown.

Effect of iodine contrast agent concentration on cerebrovascular dose for synchrotron radiation microangiography based on a simple mouse head model and a voxel mouse head phantom by Monte Carlo simulation.

Effective setting strategies using Monte Carlo simulation are presented to mitigate the irradiation damage in synchrotron radiation microangiography (SRA). A one-dimensional mouse head model and a segmented voxel phantom mouse head were simulated using the EGSnrc/DOSXYZnrc code to investigate the dose enhancement effect of an iodine contrast agent irradiated by a monochromatic synchrotron radiation source. The influence of the iodine concentration, vessel width and depth, protection with and without the skull layer, and various incident X-ray energies were all simulated. The dose enhancement effect and the absolute dose based on the segmented voxel mouse head phantom were evaluated. The dose enhancement ratio depended little on the irradiation depth, but strongly and linearly increasing on iodine concentration. The protection given by the skull layer cannot be ignored in SRA because a 700 µm-thick skull can decrease the dose by 10%. The incident X-ray energy can affect the dose significantly. Compared with a dose of 33.2 keV for 50 mgI ml(-1), a dose of 32.7 keV decreased by 38%, whereas a dose of 33.7 keV increased by 69.2% and the variation strengthened more with enhanced iodine concentration. The segmented voxel mouse head phantom also showed that the average dose enhancement effect and the maximal voxel dose per photon depended little on the iodine voxel volume ratio but strongly on the iodine concentration. To decrease the damage caused by the dose in SRA, a high-Z contrast agent should be used as little as possible and irradiation of the injection site of the contrast agent should be avoided immediately after the injection. The fragile vessel containing iodine should avoid being closely irradiated. Avoiding irradiating through a thin (or no) skull region, or attaching a thin equivalent material on the outside for protection are better methods. An incident X-ray energy as low as possible should be used as long as the SRA image quality is ensured. The use of the synergetic and synchronous shuttering technique in SRA is also very critical in order to effectively shorten the accumulative irradiation time in in vivo animal irradiation experiments.