A motion artifact reduction method for dental CT based on subpixel-resolution image registration of projection data

Eldib, Mohamed Elsayed,Hegazy, Mohamed A.A.,Cho, Myung Hye,Cho, Min Hyoung,Lee, Soo Yeol Elsevier 2018 Computers in biology and medicine Vol.103 No.-

<P><B>Abstract</B></P> <P>High-resolution imaging is essential in three-dimensional (3D) CT image-based digital dentistry. A small amount of head motion during a CT scan can degrade the spatial resolution of the images to the extent where the efficacy of 3D image-based digital dentistry is greatly compromised. We introduce a retrospective motion artifact reduction (MAR) method for dental CTs that eliminates the necessity for any external motion tracking devices. Assuming that rigid-body motions are dominant in a dental scan of a human head, we extracted motion information from the projection data. By taking the cross-correlation between two successive projection data for every projection view, we determined the displacement of the projection data at each view. We experimentally found that any motion of the imaging object during the scan resulted in displacement of the projection data proportional to the motion amplitude. We decomposed the displacement into two components, one caused by translational motion and the other caused by rotational motion. The displacement components were used to correct the projection data before CT image reconstruction. We experimentally verified the MAR method using the projection data of a few phantoms acquired through a clinical dental CT machine. When the MAR performance was evaluated by the structural similarity index (SSIM) and the normalized absolute error (NAE) in reference to the motion-less images, the SSIM improved to 99% while the NAE was reduced by 80–90%.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We introduce a retrospective motion artifact reduction (MAR) method for a dental CT. </LI> <LI> A subpixel image registration technique is used to estimate the motion-induced displacements. </LI> <LI> The proposed method can estimate all the motion components including translation and rotation. </LI> <LI> Actuator-controlled and manual motions have been applied on phantoms using a clinical dental CT. </LI> <LI> The experimental results demonstrate the high performance of the proposed method. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

A head motion estimation algorithm for motion artifact correction in dental CT imaging

Hernandez, Daniel,Eldib, Mohamed Elsayed,Hegazy, Mohamed A A,Cho, Myung Hye,Cho, Min Hyoung,Lee, Soo Yeol Institute of Physics in association with the Ameri 2018 Physics in medicine & biology Vol.63 No.6

<P>A small head motion of the patient can compromise the image quality in a dental CT, in which a slow cone-beam scan is adopted. We introduce a retrospective head motion estimation method by which we can estimate the motion waveform from the projection images without employing any external motion monitoring devices. We compute the cross-correlation between every two successive projection images, which results in a sinusoid-like displacement curve over the projection view when there is no patient motion. However, the displacement curve deviates from the sinusoid-like form when patient motion occurs. We develop a method to estimate the motion waveform with a single parameter derived from the displacement curve with aid of image entropy minimization. To verify the motion estimation method, we use a lab-built micro-CT that can emulate major head motions during dental CT scans, such as tilting and nodding, in a controlled way. We find that the estimated motion waveform conforms well to the actual motion waveform. To further verify the motion estimation method, we correct the motion artifacts with the estimated motion waveform. After motion artifact correction, the corrected images look almost identical to the reference images, with structural similarity index values greater than 0.81 in the phantom and rat imaging studies.</P>

Dual‐energy‐based metal segmentation for metal artifact reduction in dental computed tomography

Hegazy, Mohamed A. A.,Eldib, Mohamed Elsayed,Hernandez, Daniel,Cho, Myung Hye,Cho, Min Hyoung,Lee, Soo Yeol Published for the American Association of Physicis 2018 Medical physics Vol.45 No.2

<P>Conclusions: The proposed dual-energy-based method has shown better performance in metal segmentation leading to better MAR performance in dental imaging. We expect the proposed metal segmentation method can be used to improve the MAR performance of existing MAR techniques that have metal segmentation steps in their correction procedures. (C) 2017 American Association of Physicists in Medicine</P>

U-net based metal segmentation on projection domain for metal artifact reduction in dental CT

Mohamed A. A. Hegazy,Myung Hye Cho,Min Hyoung Cho,Soo Yeol Lee 대한의용생체공학회 2019 Biomedical Engineering Letters (BMEL) Vol.9 No.3

Unlike medical computed tomography (CT), dental CT often suff ers from severe metal artifacts stemming from high-densitymaterials employed for dental prostheses. Despite the many metal artifact reduction (MAR) methods available for medical CT,those methods do not suffi ciently reduce metal artifacts in dental CT images because MAR performance is often compromisedby the enamel layer of teeth, whose X-ray attenuation coeffi cient is not so diff erent from that of prosthetic materials. Wepropose a deep learning-based metal segmentation method on the projection domain to improve MAR performance in dentalCT. We adopted a simplifi ed U-net for metal segmentation on the projection domain without using any information from themetal-artifacts-corrupted CT images. After training the network with the projection data of fi ve patients, we segmented themetal objects on the projection data of other patients using the trained network parameters. With the segmentation results,we corrected the projection data by applying region fi lling inside the segmented region. We fused two CT images, one fromthe corrected projection data and the other from the original raw projection data, and then we forward-projected the fusedCT image to get the fused projection data. To get the fi nal corrected projection data, we replaced the metal regions in theoriginal projection data with the ones in the fused projection data. To evaluate the effi cacy of the proposed segmentationmethod on MAR, we compared the MAR performance of the proposed segmentation method with a conventional MARmethod based on metal segmentation on the CT image domain. For the MAR performance evaluation, we considered thethree primary MAR performance metrics: the relative error (REL), the sum of square diff erence (SSD), and the normalizedabsolute diff erence (NAD). The proposed segmentation method improved MAR performances by around 5.7% for REL,6.8% for SSD, and 8.2% for NAD. The proposed metal segmentation method on the projection domain showed better MARperformance than the conventional segmentation on the CT image domain. We expect that the proposed segmentation methodcan improve the performance of the existing MAR methods that are based on metal segmentation on the CT image domain.

Investigation of jack-up leg extension for deep water operations

Yousri M. A. Welaya,Ahmed Elhewy,Mohamed Hegazy 대한조선학회 2015 International Journal of Naval Architecture and Oc Vol.7 No.2

Since the first jack-up was built, jackups have become the most popular type of mobile offshore drilling unit (MODU) for offshore exploration and development purposes in shallow water. The most pivotal component of the jack-up unit is the leg, which can directly affect the global performance of the unit. In this paper, an investigation into extending the length of the jack up leg is carried out in order to study the enhancement of the rig capability to drill in deeper water approaching the range of the Semisubmersible Drilling Unit (SSDU) (300-1000ft). A study of the performance of a deep-water jack-up unit is performed with different leg lengths. Typical leg scantling dimensions and identical external loads are assigned, and then a detailed Finite Element Analysis (FEA) model is created in order to simulate the jack-up leg unit’s structural behavior. A Multi-point Constraint (MPC) element together with the spring element is used to deal with the boundary conditions. Finally, a comparative analysis for five leg lengths is carried out to illustrate their performance, including the ultimate static strength, and weight.

Investigation of jack-up leg extension for deep water operations

Welaya, Yousri M.A.,Elhewy, Ahmed,Hegazy, Mohamed The Society of Naval Architects of Korea 2015 International Journal of Naval Architecture and Oc Vol.7 No.2

Since the first jack-up was built, jackups have become the most popular type of mobile offshore drilling unit (MODU) for offshore exploration and development purposes in shallow water. The most pivotal component of the jack-up unit is the leg, which can directly affect the global performance of the unit. In this paper, an investigation into extending the length of the jack up leg is carried out in order to study the enhancement of the rig capability to drill in deeper water approaching the range of the Semisubmersible Drilling Unit (SSDU) (300-1000ft). A study of the performance of a deep-water jack-up unit is performed with different leg lengths. Typical leg scantling dimensions and identical external loads are assigned, and then a detailed Finite Element Analysis (FEA) model is created in order to simulate the jack-up leg unit's structural behavior. A Multi-point Constraint (MPC) element together with the spring element is used to deal with the boundary conditions. Finally, a comparative analysis for five leg lengths is carried out to illustrate their performance, including the ultimate static strength, and weight.

Comparative Study on Bone Marrow-Versus Adipose-Derived Stem Cells on Regeneration and Re-Innervation of Skeletal Muscle Injury in Wistar Rats

Moussa Manal H.,Hamam Ghada G.,Abd Elaziz Asmaa E.,Rahoma Marwa A.,Abd El Samad Abeer A.,El-Waseef Dalia A. A.,Hegazy Mohamed A. 한국조직공학과 재생의학회 2020 조직공학과 재생의학 Vol.17 No.6

Background: Skeletal muscle injuries are frequent clinical challenges due to associated fibrosis and disability. Regenerative medicine is an emerging promising strategy for such cases. The aim of this study was to compare between the effects of bone marrow-mesenchymal stem cells (BM-MSCs) versus adipose tissue stromal cells (ADSCs) on regeneration and re-innervation of skeletal muscle laceration injury in Wistar rats at different time intervals. Methods: Six young male rats were used as a source of allogenic MSCs. Eighty-four adult female rats were divided into: Group I (control), Group II (Untreated Laceration): right gluteal muscle was lacerated and left for spontaneous healing, Group III (BM-MSCs): right gluteal muscle was lacerated with concomitant local intramuscular injection of 1 × 106 BM-MSCs in the lacerated muscle, Group IV (ADSCs): right gluteal muscle was lacerated with concomitant local intramuscular injection of 1 × 106 ADSCs in lacerated muscle. Rats were sacrificed after one, two and eight weeks. Muscles were processed to prepare sections stained with H&E, Mallory’s trichrome and immune-histochemical staining (neurofilament light chain). Results: A significant increase in collagen fibers and failure of re-innervation were noticed in untreated laceration group. BM-MSCs-treated groups showed regeneration of muscle fibers but with increased collagen fibers. Meanwhile, ADSCs showed better regenerative effects evidenced by significant increase in the number of myotubes and significant decrease in collagen deposition. Re-innervation was noticed in MSCs-injected muscles after 8 weeks of laceration. Conclusion: Both BM-MSCs and ADSCs improved regeneration of skeletal muscle laceration injury at short- and long-term durations. However, fibrosis was less in ADSCs-treated rats. Effective re-innervation of injured muscles occurred only at the long-term duration.

Morbidity Profile of Cases Attended Oncology Center of Mansoura University (OCMU), Egypt: A Cross-Sectional Study

Miada M. F. Elmetwaly,Ziad A. Emarah,Mohamed A. Hegazy,Emily A. Kamel,Adel I. Al-Wehedy,Abd Elhamied M. Abd Elhamied 질병관리본부 2019 Osong Public Health and Research Persptectives Vol.10 No.3

Objectives: In Egypt, the National Cancer Registry Program integrates hospital-based data from multiple Egyptian governorates to obtain representative rates. Unfortunately, Dakahlia (one of the largest Egyptian governorates) was not integrated in the National Cancer Registry Program. This research aimed to acquire malignancy rates from the Oncology Center of Mansoura University, which is one of the two oncology centers present in Dakalia Governorate in Egypt. Methods: Electronic records of patients who attended the Oncology Center of Mansoura University during 2016 were accessed with permission. Analysis was performed to extract diagnostic categories (age, gender, and geographic distribution of cases). Results: Most commonly diagnosed malignancies were breast cancer which represented about 10% of cases in the Oncology Center of Mansoura University during 2016. This was followed by leukemia (3.80%), lymphoma (3.59%), and liver cancer (3.44%). Diagnoses encountered included benign and malignant tumors as well as non-tumor diagnoses. The Mansoura district had the highest proportionate rate of breast cancer cases. Females in the age group ≥ 35 < 60 years had the highest incidence of malignancy cases across all diagnoses. Conclusion: The burden of breast cancer in Mansoura district is high. Risk factors need further evaluation with a recommendation to perform an environmental risk assessment.