scholarly journals The Distribution of Skull Score and Skull Density Ratio in Tremor Patients for MR-Guided Focused Ultrasound Thalamotomy

2021 ◽  
Vol 15 ◽  
Author(s):  
Kevin Wen-Kai Tsai ◽  
Jui-Cheng Chen ◽  
Hui-Chin Lai ◽  
Wei-Chieh Chang ◽  
Takaomi Taira ◽  
...  

ObjectiveMagnetic resonance-guided focused ultrasound (MRgFUS) is a minimum-invasive surgical approach to non-incisionally cause the thermos-coagulation inside the human brain. The skull score (SS) has already been approved as one of the most dominant factors related to a successful MRgFUS treatment. In this study, we first reveal the SS distribution of the tremor patients, and correlate the SS with the image feature from customized skull density ratio (cSDR). This correlation might give a direction to future clinical studies for improving the SS.MethodsTwo hundred and forty-six patients received a computed tomography (CT) scan of the brain, and a bone-enhanced filter was applied and reconstructed to a high spatial resolution CT images. The SS of all patients would be estimated by the MRgFUS system after importing the reconstructed CT images into the MRgFUS system. The histogram and the cumulative distribution of the SS from all the patients were calculated to show the percentage of the patients whose SS lower than 0.3 and 0.4. The same CT images of all patients were utilized to calculated the cSDR by first segmented the trabecular bone and the cortical bone from the CT images and divided the average trabecular bone intensity (aTBI) by the average cortical bone intensity (aCBI). The Pearson’s correlations between the SS and the cSDR, aTBI, and the aCBI were calculated, respectively.ResultsThere were 19.19 and 50% of the patient who had the SS lower than the empirical threshold 0.3 and 0.4, respectively. The Pearson’s correlation between the SS and the cSDR, aCBI, and the aTBI were R = 0.8145, 0.5723, and 0.8842.ConclusionHalf of the patients were eligible for the MRgFUS thalamotomy based on the SS, and nearly 20% of patients were empirically difficult to achieve a therapeutic temperature during MRgFUS. The SS and our cSDR are highly correlated, and the SS had a higher correlation with aTBI than with aCBI. This is the first report to explicitly reveal the SS population and indicate a potential way to increase the chance to achieve a therapeutic temperature for those who originally have low SS.

Author(s):  
Chanho Kong ◽  
So Hee Park ◽  
Jaewoo Shin ◽  
Hee Gyu Baek ◽  
Juyoung Park ◽  
...  

While focused ultrasound (FUS) is non-invasive, the ultrasound energy is attenuated by the skull which results in differences in energy efficiency among patients. In this study, we investigated the effect of skull variables on the energy efficiency of FUS. The thickness and density of the skull and proportion of the trabecular bone were selected as factors that could affect ultrasound energy transmittance. Sixteen 3D-printed skull models were designed and fabricated to reflect the three factors. The energy of each phantom was measured using an ultrasonic sound field energy measurement system. The thickness and proportion of trabecular bone affected the attenuation of transmitted energy. There was no difference in the density of the trabecular bone. In clinical data, the trabecular bone ratio showed a significantly greater correlation with dose/delivered energy than that of thickness and the skull density ratio. Currently, for clinical non-thermal FUS, the data are not sufficient, but we believe that the results of this study will be helpful in selecting patients and appropriate parameters for FUS treatment.


2021 ◽  
pp. 1-9
Author(s):  
Hiroki Hori ◽  
Hirokazu Iwamuro ◽  
Masayuki Nakano ◽  
Takahiro Ouchi ◽  
Takashi Kawahara ◽  
...  

OBJECTIVE In transcranial magnetic resonance imaging–guided focused ultrasound (TcMRgFUS), a high skull density ratio (SDR) is advantageous to achieve a sufficiently high temperature at the target. However, it is not easy to estimate the temperature rise because the SDR shows different values depending on the reconstruction filter used. The resolution characteristic of a computed tomography (CT) image depends on a modulation transfer function (MTF) defined by the reconstruction filter. Differences in MTF induce unstable SDRs. The purpose of this study was both to standardize SDR by developing a method to correct the MTF and to enable effective patient screening prior to TcMRgFUS treatment and more accurate predictions of focal temperature. METHODS CT images of a skull phantom and five subjects were obtained using eight different reconstruction filters. A frequency filter (FF) was calculated using the MTF of each reconstruction filter, and the validity of SDR standardization was evaluated by comparing the variation in SDR before and after FF correction. Subsequently, FF processing was similarly performed using the CT images of 18 patients who had undergone TcMRgFUS, and statistical analyses were performed comparing the relationship between the SDRs before and after correction and the maximum temperature in the target during TcMRgFUS treatment. RESULTS The FF was calculated for each reconstruction filter based on one manufacturer's BONE filter. In the CT images of the skull phantom, the SDR before FF correction with five of the other seven reconstruction filters was significantly smaller than that with the BONE filter (p < 0.01). After FF correction, however, a significant difference was recognized under only one condition. In the CT images of the five subjects, variation of the SDR due to imaging conditions was significantly improved after the FF correction. In 18 cases treated with TcMRgFUS, there was no correlation between SDR before FF correction and maximum temperature (rs = 0.31, p > 0.05); however, a strong positive correlation was observed after FF correction (rs = 0.71, p < 0.01). CONCLUSIONS After FF correction, the difference in SDR due to the reconstruction filter used is smaller, and the correlation with temperature is stronger. Therefore, the SDR can be standardized by applying the FF, and the maximum temperature during treatment may be predicted more accurately.


Author(s):  
Amal Alzain ◽  
Suhaib Alameen ◽  
Rani Elmaki ◽  
Mohamed E. M. Gar-Elnabi

This study concern to characterize the brain tissues to ischemic stroke, gray matter, white matter and CSF using texture analysisto extract classification features from CT images. The First Order Statistic techniques included sevenfeatures. To find the gray level variation in CT images it complements the FOS features extracted from CT images withgray level in pixels and estimate the variation of thesubpatterns. analyzing the image with Interactive Data Language IDL software to measure the grey level of images. The results show that the Gray Level variation and   features give classification accuracy of ischemic stroke 97.6%, gray matter95.2%, white matter 97.3% and the CSF classification accuracy 98.0%. The overall classification accuracy of brain tissues 97.0%.These relationships are stored in a Texture Dictionary that can be later used to automatically annotate new CT images with the appropriate brain tissues names.


2017 ◽  
Vol 1 (3) ◽  
pp. 54
Author(s):  
BOUKELLOUZ Wafa ◽  
MOUSSAOUI Abdelouahab

Background: Since the last decades, research have been oriented towards an MRI-alone radiation treatment planning (RTP), where MRI is used as the primary modality for imaging, delineation and dose calculation by assigning to it the needed electron density (ED) information. The idea is to create a computed tomography (CT) image or so-called pseudo-CT from MRI data. In this paper, we review and classify methods for creating pseudo-CT images from MRI data. Each class of methods is explained and a group of works in the literature is presented in detail with statistical performance. We discuss the advantages, drawbacks and limitations of each class of methods. Methods: We classified most recent works in deriving a pseudo-CT from MR images into four classes: segmentation-based, intensity-based, atlas-based and hybrid methods. We based the classification on the general technique applied in the approach. Results: Most of research focused on the brain and the pelvis regions. The mean absolute error (MAE) ranged from 80 HU to 137 HU and from 36.4 HU to 74 HU for the brain and pelvis, respectively. In addition, an interest in the Dixon MR sequence is increasing since it has the advantage of producing multiple contrast images with a single acquisition. Conclusion: Radiation therapy field is emerging towards the generalization of MRI-only RT thanks to the advances in techniques for generation of pseudo-CT images. However, a benchmark is needed to set in common performance metrics to assess the quality of the generated pseudo-CT and judge on the efficiency of a certain method.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Danielle Weber-Adrian ◽  
Rikke Hahn Kofoed ◽  
Joseph Silburt ◽  
Zeinab Noroozian ◽  
Kairavi Shah ◽  
...  

AbstractNon-surgical gene delivery to the brain can be achieved following intravenous injection of viral vectors coupled with transcranial MRI-guided focused ultrasound (MRIgFUS) to temporarily and locally permeabilize the blood–brain barrier. Vector and promoter selection can provide neuronal expression in the brain, while limiting biodistribution and expression in peripheral organs. To date, the biodistribution of adeno-associated viruses (AAVs) within peripheral organs had not been quantified following intravenous injection and MRIgFUS delivery to the brain. We evaluated the quantity of viral DNA from the serotypes AAV9, AAV6, and a mosaic AAV1&2, expressing green fluorescent protein (GFP) under the neuron-specific synapsin promoter (syn). AAVs were administered intravenously during MRIgFUS targeting to the striatum and hippocampus in mice. The syn promoter led to undetectable levels of GFP expression in peripheral organs. In the liver, the biodistribution of AAV9 and AAV1&2 was 12.9- and 4.4-fold higher, respectively, compared to AAV6. The percentage of GFP-positive neurons in the FUS-targeted areas of the brain was comparable for AAV6-syn-GFP and AAV1&2-syn-GFP. In summary, MRIgFUS-mediated gene delivery with AAV6-syn-GFP had lower off-target biodistribution in the liver compared to AAV9 and AAV1&2, while providing neuronal GFP expression in the striatum and hippocampus.


2021 ◽  
Vol 80 (Suppl 1) ◽  
pp. 825.2-826
Author(s):  
M. Jansen ◽  
A. Ooms ◽  
T. D. Turmezei ◽  
J. W. Mackay ◽  
S. Mastbergen ◽  
...  

Background:In addition to cartilage degeneration, knee osteoarthritis (OA) causes bone changes, including cortical bone thickening, subchondral bone density decrease, and bone shape changes as a result of widening and flattening condyles and osteophyte formation. Knee joint distraction (KJD) is a joint-preserving treatment for younger (<65 years) knee OA patients that has been shown to reverse OA cartilage degradation. On radiographs, KJD showed a decrease in subchondral bone density and an increase in osteophyte formation. However, these bone changes have never been evaluated with a 3D imaging technique.Objectives:To evaluate cortical bone thickness, subchondral trabecular bone density, and bone shape on CT scans before and one year after KJD treatment.Methods:19 KJD patients were included in an extended imaging protocol, undergoing a CT scan before and one year after treatment. Stradview v6.0 was used for semi-automatic tibia and femur segmentation from axial thin-slice (0.45mm) CT scans. Cortical bone thickness (mm) and trabecular bone density (Hounsfield units, HU) were measured with an automated algorithm. Osteophytes were excluded. Afterwards, wxRegSurf v18 was used for surface registration. Registration data was used for bone shape measurements. MATLAB R2020a and the SurfStat MATLAB package were used for data analysis and visualization. Two-tailed F-tests were used to calculate changes over time. Two separate linear regression models were used to show the influence of baseline Kellgren-Lawrence grade and sex on the changes over time. Statistical significance was calculated with statistical parametric mapping; a p-value <0.05 was considered statistically significant. Bone shape changes were explored visually using vertex by vertex displacements between baseline and follow-up. Patients were separated into two groups based on whether their most affected compartment (MAC) was medial or lateral. Only patients with axial CT scans at both time points available for analysis were included for evaluation.Results:3 Patients did not have complete CTs and in 1 patient the imaged femur was too short, leaving 16 patients for tibial analyses and 15 patients for femoral analyses. The MAC was predominantly the medial side (medial MAC n=14; lateral n=2). Before treatment, the MAC cortical bone was compared to the rest of the joint (Figure 1). One year after treatment, MAC cortical thickness decreased, although this decrease of up to approximately 0.25 mm was not statistically significant. The trabecular bone density was also higher before treatment in the MAC, and a decrease was seen throughout the entire joint, although statistically significant only for small areas on mostly the MAC where this decrease was up to approximately 80 HU (Figure 1). Female patients and patients with a higher Kellgren-Lawrence grade showed a somewhat larger decrease in cortical bone thickness. Trabecular density decreased less for patients with a higher Kellgren-Lawrence grade, and female patients showed a higher density decrease interiorly while male patients showed a higher decrease exteriorly. None of this was statistically significant. The central areas of both compartments showed an outward shape change, while the outer ring showed inward changes.Conclusion:MAC cortical bone thickness shows a partial decrease after KJD. Trabecular bone density decreased on both sides of the joint, likely as a direct result of the bicompartmental unloading. For both subchondral bone parameters, MAC values became more similar to the LAC, indicating (partial) subchondral bone normalization in the most affected parts of the joint. The bone shape changes may indicate a reversal of typical OA changes, although the inward difference that was seen on the outer edges may be a result of osteophyte-related changes that might have affected the bone segmentation. In conclusion, KJD treatment shows subchondral bone normalization in the first year after treatment, and longer follow-up might show whether these changes are a temporary result of joint unloading or indicate more prolonged bone changes.Disclosure of Interests:None declared.


2020 ◽  
Vol 319 (3) ◽  
pp. R366-R375
Author(s):  
Hugo F. Posada-Quintero ◽  
Youngsun Kong ◽  
Kimberly Nguyen ◽  
Cara Tran ◽  
Luke Beardslee ◽  
...  

We have tested the feasibility of thermal grills, a harmless method to induce pain. The thermal grills consist of interlaced tubes that are set at cool or warm temperatures, creating a painful “illusion” (no tissue injury is caused) in the brain when the cool and warm stimuli are presented collectively. Advancement in objective pain assessment research is limited because the gold standard, the self-reporting pain scale, is highly subjective and only works for alert and cooperative patients. However, the main difficulty for pain studies is the potential harm caused to participants. We have recruited 23 subjects in whom we induced electric pulses and thermal grill (TG) stimulation. The TG effectively induced three different levels of pain, as evidenced by the visual analog scale (VAS) provided by the subjects after each stimulus. Furthermore, objective physiological measurements based on electrodermal activity showed a significant increase in levels as stimulation level increased. We found that VAS was highly correlated with the TG stimulation level. The TG stimulation safely elicited pain levels up to 9 out of 10. The TG stimulation allows for extending studies of pain to ranges of pain in which other stimuli are harmful.


1984 ◽  
Vol 66 (1) ◽  
pp. 109-112 ◽  
Author(s):  
R. Hesp ◽  
A. C. Deacon ◽  
Patricia Hulme ◽  
J. Reeve

1. Mean linear attenuation coefficients for trabecular bone (T) in the distal radius and total absorption coefficients (TA) in the radial mid-shafts of 22 patients with crush fracture osteoporosis were measured serially for a year by using computed tomography. After approximately 6 months, each patient was admitted to a metabolic ward for an 18-day calcium balance study. 2. The rate of change (trend) in trabecular bone (T) in the distal radius was a better predictor of calcium balance than the trend in mid-shaft cortical bone (TA). 3. The scatter in the regressions of the trends of T and TA on calcium balance could be accounted for by known methodological uncertainties.


2021 ◽  
pp. 1-6
Author(s):  
Ken Iijima ◽  
Hajime Yokota ◽  
Toshio Yamaguchi ◽  
Masayuki Nakano ◽  
Takahiro Ouchi ◽  
...  

OBJECTIVE Sufficient thermal increase capable of generating thermocoagulation is indispensable for an effective clinical outcome in patients undergoing magnetic resonance–guided focused ultrasound (MRgFUS). The skull density ratio (SDR) is one of the most dominant predictors of thermal increase prior to treatment. However, users currently rely only on the average SDR value (SDRmean) as a screening criterion, although some patients with low SDRmean values can achieve sufficient thermal increase. The present study aimed to examine the numerical distribution of SDR values across 1024 elements to identify more precise predictors of thermal increase during MRgFUS. METHODS The authors retrospectively analyzed the correlations between the skull parameters and the maximum temperature achieved during unilateral ventral intermediate nucleus thalamotomy with MRgFUS in a cohort of 55 patients. In addition, the numerical distribution of SDR values was quantified across 1024 elements by using the skewness, kurtosis, entropy, and uniformity of the SDR histogram. Next, the authors evaluated the correlation between the aforementioned indices and a peak temperature > 55°C by using univariate and multivariate logistic regression analyses. Receiver operating characteristic curve analysis was performed to compare the predictive ability of the indices. The diagnostic performance of significant factors was also assessed. RESULTS The SDR skewness (SDRskewness) was identified as a significant predictor of thermal increase in the univariate and multivariate logistic regression analyses (p < 0.001, p = 0.013). Moreover, the receiver operating characteristic curve analysis indicated that the SDRskewness exhibited a better predictive ability than the SDRmean, with area under the curve values of 0.847 and 0.784, respectively. CONCLUSIONS The SDRskewness is a more accurate predictor of thermal increase than the conventional SDRmean. The authors suggest setting the SDRskewness cutoff value to 0.68. SDRskewness may allow for the inclusion of treatable patients with essential tremor who would have been screened out based on the SDRmean exclusion criterion.


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