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| 3361.
 | 129 | Comparison of iNAV-based Free-Breathing Non-Contrast Coronary Magnetic Resonance Angiography Acquired at 0.7mm3 and 0.9mm3 Resolution Simon J. Littlewood1, Gregory Wood2,3, Karl P. Kunze4, Michael G. Crabb1, Won Yong Kim3, Claudia Prieto1,5, and René M. Botnar1,5,6
1School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom, 2Department of Cardiology, Aarhus University Hospital, Aarhus, Denmark, 3Department of Clinical Medicine, Aarhus University, Aarhus, Denmark, 4MR Research Collaborations, Siemens Healthcare Limited, Camberley, United Kingdom, 5School of Engineering, Pontificia Universidad Católica de Chile, Santiago, Chile, 6Institute for Biological and Medical Engineering, Pontificia Universidad Católica de Chile, Santiago, Chile Keywords: Atherosclerosis, Atherosclerosis, Angiography, whole-heart Motivation: Coronary artery disease remains a significant problem worldwide and current methods for anatomical assessment involve ionising radiation and iodinated contrast agents. Goal(s): To develop a novel free-breathing, 3D whole-heart, coronary magnetic resonance angiography sequence with high spatial resolution for the assessment of coronary anatomy and coronary artery disease. Approach: Nine patients referred for assessment of suspected coronary artery disease were scanned using the proposed sequence at 1.5T. Acquisitions at 0.9mm3 and 0.7mm3 were compared. Results: The 0.7mm3 acquisition demonstrated improved qualitative and semi-quantitative vessel visualisation and coronary stenosis detection compared with 0.9mm3 acquisition in an average scan time of <14 minutes. Impact: This work demonstrates improved coronary artery lumen visualisation and stenosis detection compared to 0.9mm3 acquisitions, providing a further step forward towards clinical adoption as a contrast- and radiation-free alternative to CTCA. |
| 3362.
 | 130 | Single breath hold 3D isotropic whole heart coronary MRA using turbo field echo planar imaging with deep learning constrained Compressed SENSE Kazuo Kodaira1, Michinobu Nagao2, Masami Yoneyama3, Johannes M Peeters4, Yasutomo Katsumata3, Hiroshi Hamano3, Mana Kato1, Takumi Ogawa1, Yutaka Hamatani1, Isao Shiina1, Yasuyuki Morita1, Yasuhiro Goto1, and Shuji Sakai2
1Department of Radiological Services, Tokyo Women’s Medical University, Tokyo, Japan, 2Department of Diagnostic imaging & Nuclear Medicine, Tokyo Women’s Medical University, Tokyo, Japan, 3Philips Japan, Tokyo, Japan, 4Philips Healthcare, Best, Netherlands Keywords: Vascular, Cardiovascular Motivation: Whole-heart-coronary-MRA (WHC-MRA) is typically performed during free-breathing, and respiratory motion is prospectively compensated by using a 1D-right-diaphragmatic-navigator. However, this method requires long acquisition time and causes a heavy burden on the patient. Goal(s): Our goal was to obtain high-resolution WHC-MRA with single-breath-hold while ensuring clinically acceptable signal-to-ratio. Approach: Turbo-field-echo-planar-imaging (TFEPI), a high-speed technique, was combined with deep learning constrained Compressed SENSE (CS-AI) and image quality was evaluated by visual evaluation and contrast-to-ratio. Results: TFEPI with CS-AI provided high spatial resolution isotoropic single-breath-hold WHC-MRA while maintaining clinically acceptable image quality and scan time compared to Compressed SENSE and SENSE. Impact: High-resolution single-breath-hold WHC-MRA with
clinically acceptable image quality by 3D TFEPI with CS-AI may improve the
throughput of cardiac MRI examinations, and in addition reduce patient burden. |
| 3363.
 | 131 | 3D phase contrast MRI of the coronary arteries – Improvements and adaptations at 3T Denise Lichthardt1, Jens Wetzl2, Michaela Schmidt2, Peter Speier2, Christoph Tillmanns3, Armin M. Nagel1, and Daniel Giese2
1Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, Germany, 2Siemens Healthineers AG, Erlangen, Germany, 3Diagnostikum Berlin, Berlin, Germany Keywords: Flow, Motion Correction Motivation: 3D Phase contrast MRI of the coronary arteries remains challenging due to low SNR and motion. Goal(s): Develop a 3D PC sequence for flow quantification in the coronary arteries at 3T with improved SNR and reduced motion artefacts compared to 1.5T. Approach: The sequence was optimized by acquiring datasets separately, enabling inter-scan motion compensation while circumventing SAR limitations. Coronary flow was quantified in 5 subjects at 3T. Results: Phantom measurements showed reduced image artefacts using the proposed sequence. In-vivo mean peak velocities per slice along the left and right coronary arteries were 15.9±5.0cm/s and 14.1±4.9cm/s respectively. Impact: High SNR 3D flow measurements
in the proximal coronary arteries are now possible, as SAR restrictions at 3T have
been overcome. This may enable the non-invasive hemodynamic assessment of coronary arteries in
patients with CAD. |
| 3364.
 | 132 | Comparison between 3T non-selective pulse non-enhanced whole-heart bTFE coronary MR angiography and 3T mDixon water-fat separation GRE method Yong Yuan1, Guangming Lu2, Dongsheng Jin2, Weibo Chen3, Baijun Wang3, Tong Chen4, Qiuju Hu5, Jiajia Zhu5, and Yane Zhao5
1Geriatric Hospital of Nanjing Medical University, Nanjing 210024, China, Nanjing, China, 2Geriatric Hospital of Nanjing Medical University, Nanjing, China, 3Philips Healthcare, Shanghai, China, Shanghai, China, 4Philips Healthcare, Hangzhou, China, Hangzhou, China, 5Geriatric Hospital of Nanjing Medical, Nanjing, China Keywords: Vascular, Cardiovascular Motivation: To improve the image quality of the non-enhanced whole heart bTFE CMRA sequence at 3T. Goal(s): To compare the performance of a newly improved bTFE CMRA sequence with the mDixon water-fat separation GRE method at 3T for CMRA. Approach: Success rate, acquisition time, image quality, and diagnostic performance were compared. Results: This study demonstrated that the performance of the 3D bTFE CMRA sequence at 3T was brilliant, with a high success rate, appropriate acquisition time, excellent image quality, and good diagnostic performance. Impact: The non-enhanced bTFE CMRA sequence at 3T may
be recommended for more extensive clinical applications. |
| 3365.
 | 133 | Efficient native MRA at 0.55T using motion-correction Robert Stoll1, Dominik Nickel1, Christoph Kolbitsch2, and Daniel Giese1
1Siemens Healthineers, Erlangen, Germany, 2Physikalisch - Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany Keywords: Vascular, Cardiovascular Motivation: MRI at 0.55T with an 80cm bore has allowed improved access to CMR for patients. The application of robust native whole-thorax MRA at low-field remains limited especially due to the challenge of respiratory motion. Goal(s): To develop a large field-of-view, whole-thorax, self-gated and breathing-motion corrected native MRA with a predictable scan time and efficient data usage at 0.55T. Approach: An optimized sampling pattern is used with T2-prep, dual-echo Dixon and non-rigid motion correction is developed. Results: The approach was successfully applied in-vivo and shows successful mitigation of motion artefacts and blurring and good separation of water and fat in the entire thoracic region. Impact: Proof of the viability of self-gated MOCO MRA at
0.55T. |
| 3366.
 | 134 | Comparison of MSG-EPI and 3D-BTFE sequences in non-enhanced coronary magnetic resonance imaging Jiajia Zhu1, Wenjing Li1, Guangming Lu2, Dongsheng Jin1, Yong Yuan1, Weibo Chen3, Baijun Wang3, Tong Chen3, and Yane Zhao1
1Jiangsu Province Official Hospital, Nanjing, China, 2Jinling Hospital, Nanjing, China, 3Philips Healthcare, Shanghai, China Keywords: Vascular, Cardiovascular Motivation: Non-contrast enhanced coronary MRA is a non-invasive and non-ionizing radiation imaging technology. 3D-BTFE is the most commonly used coronary MRA sequence but is time-consuming. Goal(s): We compared the MSG-EPI and 3D-BTFE sequences and evaluated the value of MSG-EPI. Approach: The differences of image score, SNR and CNR between the two sequences were compared. Results: We found that the image score, SNR, and CNR differ between MSG-EPI and 3D-BTFE. In lumen display of RCA and LAD, image scores of MSG-EPI were sufficient to attach diagnostic requirements and there was no significant difference in SNR. However, the CNR of 3D-BTFE was significantly higher than MSG-EPI. Impact: This study
compared MSG-EPI and 3D-BTFE sequences and found that although MSG-EPI 's image
quality is slightly inferior to 3D-BTFE 's, its advantage of rapid imaging
makes it promising in clinical applications.
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| 3367.
 | 135 | A clinical strategy of 3.0-T non-contrast coronary MRA: a combination of diastole and systole imaging Hongfei Lu1, Hang Jin1, Mengsu Zeng1, Xiuzheng Yue2, and Weibo Chen3
1Department of Radiology, Zhongshan Hospital, Fudan University, Shanghai, China, 2Philips Healthcare, Beijing, China, 3Philips Healthcare, Shanghai, China Keywords: Vascular, Cardiovascular, coronary Motivation: Coronary magnetic resonance angiography (MRA) has not been widely used due to lower diagnostic accuracy. The combination of diastole and systole imaging may enhance its clinical applications. Goal(s): Designing a coronary MRA protocol combining diastole and systole imaging and evaluating its diagnostic performance for detecting significant coronary artery disease (CAD). Approach: 3.0-T non-contrast coronary MRA was carried out twice at diastole and systole. Significant CAD was evaluated by coronary MRA as follows:1) by diastole mode, 2) by systole mode, and 3) by combined mode. Results: Combined coronary MRA showed equally high sensitivity but improved specificity than single diastolic mode. Impact: This study demonstrated that 1) 3.0-T non-contrast coronary MRA using combinational diastole and systole imaging can noninvasively detect CAD with high sensitivity and moderate specificity; 2) Combining diastole and systole imaging improved the diagnostic accuracy of coronary MRA, especially specificity. |
| 3368.
 | 136 | Delivery of small mocluer drugs with Metal-Organic Cage-Based Microenvironment-Responsive Nanomedicine for Atherosclerosis theranostic Dongye Li1, Kan Deng2, Xinyu Yan1, Xieqing Yang1, and Cunjing Zheng1
1department of radiology, Sun Yat sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China, 2Philips Healthcare, Guangzhou, China Keywords: Atherosclerosis, Atherosclerosis Motivation: Due to the complex pathogenesis of AS formation, the clinical treatment of AS with medicine is durable and often ineffective. it is necessary to seek a new strategy that is broadly applicable to all patients for AS theranostics . Goal(s): MM nanoparticles could delivering small molecule drugs to plaques and monitored by MR in real time upon Mn2+ released from AS microenvironment-responsive MnO2 nanoparticles. Approach: In vitro and vivo studies on 3.0T and 9.4T MR scaner. Results: In vitro and vivo studies showed that MM could be monitored by MR in real time upon Mn2+ released from acidic- and H2O2- microenvironment-responsive MnO2 nanoparticles. Impact: Nanocarriers(MM) exhibited
remarkable in vivo MRI monitoring of the therapeutic process with a long
imaging window and good biocompatibility and biosafety. This MRI-visible
nanomedicine shows immense potential as a theranostic platform for AS therapy. |
| 3369.
 | 137 | Turbo spin-echo based enhanced acceleration-selective arterial spin labeling (eAccASL) for the lower extremity MR angiography Natsuo Konta1,2, Shuhei Shibukawa3, Tomohiko Horie1, Tetsu Niwa4, Makoto Obara5, Takashi Okazaki4, Yui Kawamura4, and Toshiaki Miyati2
1Department of Radiology, Tokai University Hospital, Kanagawa, Japan, 2Division of Health Sciences, Graduate School of Medical Sciences, Kanazawa University, Ishikawa, Japan, 3Department of Radiological Technology, Juntendo University, Tokyo, Japan, 4Department of Diagnostic Radiology, Tokai University School of Medicine, Kanagawa, Japan, 5Philips Japan, Tokyo, Japan Keywords: Vascular, Blood vessels Motivation: The lower extremity MR angiography (MRA) without electrocardiography (ECG) or peripheral pulse unit (PPU) triggering and contrast enhancement is useful for diagnosing peripheral arterial disease (PAD), which can avoid synchronization failure and nephrogenic systemic fibrosis (NSF). Goal(s): Our goal was to improve peripheral arterial depiction without ECG or PPU and contrast agent. Approach: TSE-based enhanced acceleration-selective arterial spin labeling (eAccASL) (TSE-Acc) was compared with TFE-based eAccASL (TFE-Acc), and TRANCE as a reference standard by SIR, CNR, and visual inspection. Results: CNR and arterial visibility score for TSE-Acc were higher than TFE-Acc, but no difference compared with TRANCE. Impact: TSE-based enhanced acceleration-selective arterial spin labeling (eAccASL) can provide clear depiction of the peripheral arteries without ECG or PPU and contrast agent, providing sufficient diagnostic performance in PAD patients with arrhythmia and CKD. |
| 3370.
 | 138 | Optimizing Pulmonary Vascular Resistances in Single Ventricle Children at Glenn Physiology using Computational Fluid Dynamics Sebastian Laudenschlager1, Samuel Schofield2, Nicolas Drysdale3, Matthew Stone4, Jennifer Romanowicz2, Benjamin Frank2, Michael DiMaria2, Vitaly Kheyfets5, and Mehdi Hedjazi-Moghari6
1Department of Radiology, School of Medicine, University of Colorado, Aurora, CO, United States, 2Department of Cardiology, University of Colorado and Children's Hospital Colorado, Aurora, CO, United States, 3Department of Surgery, School of Medicine, University of Colorado, Aurora, CO, United States, 4Department of Surgery, University of Colorado and Children's Hospital Colorado, Aurora, CO, United States, 5Department of Critical Care, University of Colorado and Children's Hospital Colorado, Aurora, CO, United States, 6Department of Radiology, University of Colorado and Children's Hospital Colorado, Aurora, CO, United States Keywords: Flow, Cardiovascular, Catheterization, Computational Fluid Dynamics, Lumped Parameter Model, Pulmonary Vascular Resistance, Glenn Physiology, Simulation of Fontan Surgery Motivation: Individual pulmonary vascular resistances (PVR) of the left and right lung are needed to perform in-silico virtual cardiac surgery to improve Fontan conduit designs, yielding more balanced blood flow to the lungs. Goal(s): Predict patient-specific PVR of both lungs using clinical flow and pressure data acquired from cardiovascular magnetic resonance exams and catheterizations. Approach: Utilize computational fluid dynamics (CFD) and lumped parameter (LP) models to iteratively optimize the PVR of both lungs. Results: There is excellent correlation between the PVR estimates of the CFD and LP models, and both models fit to clinical outlet flow and pressure with less than 10% error. Impact: Accurate prediction of individual lung resistances is needed for patient-specific in-silico virtual cardiac surgery to optimize the design of the Fontan conduit. This design could then be implemented by surgeons to provide more balanced pulmonary blood flow in Fontan patients. |
| 3371.
 | 139 | The impact of nonlinear blood behavior on hemodynamic parameters in large vessels: more than expected Hernán Mella1, Felipe Galarce2, Julio Sotelo3, and Ernesto Castillo4
1School of Electrical Engineering, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile, 2School of Civil Engineering, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile, 3Departamento de Informática, Universidad Técnica Federico Santa María, Santiago, Chile, 4Department of Mechanical Engineering, Universidad de Santiago de Chile, Santiago, Chile Keywords: Flow, Velocity & Flow Motivation: It has not been exhaustively studied how the nonlinear behavior of the blood impacts the estimation of hemodynamic parameters Goal(s): To demonstrate the impact of nonlinear viscosities produced by diseases such as anemia and polycythemia on the estimation of hemodynamic parameters Approach: Hemodynamic parameters were estimated from synthetically generated 4D Flow images obtained from CFD simulations of the aorta using a nonlinear model for the viscosity and different levels of nonlinearity Results: Important differences were observed in WSS, OSI, and energy loss estimated using a nonlinear model for the viscosity compared to results obtained using constant viscosities. Comparisons were made for several cases Impact: This investigation could impact how the MR community estimate hemodynamic parameters from 4D MR images. |
| 3372.
 | 140 | A preliminary study of accelerated mDIXON for segmented coronary adipose tissue evaluation in patients with suspected coronary artery disease Pengfei Peng1, Jiayu Sun1, and Xiaoyong Zhang2
1Radiology, West China Hospital, Sichuan University,, Chengdu, China, 2Clinical Science, Philips Healthcare, Chengdu, China Keywords: Atherosclerosis, Cardiovascular, pericoronary adipose tissue Motivation: We attempted to assess pericoronary adipose tissue using the mDIXON sequence of magnetic resonance imaging Goal(s): To evaluate the relationship between pericoronary adipose tissue and coronary stenosis grade and plaque type Approach: Study design to test the hypothesis Results: Pericoronary adipose tissue volume is independently associated with the type of coronary plaque Impact: Magnetic resonance imaging is more accurate for the assessment of adipose tissue. This is the first time to apply MRI to the assessment of pericoronary adipose tissue, and to verify its direct relationship with coronary plaque type and stenosis grade. |
| 3373.
 | 141 | Quantitative Flow Visualization in a Patient-Specific Compliant Type B Aortic Dissection Phantom Using 0.55T MRI Coskun Bilgi1, Abbas N Moghaddam1,2, Haojie Geng1, Prakash Kumar3, Gregory A Magee4, Krishna S Nayak3, and Niema M Pahlevan1,5
1Aerospace and Mechanical Engineering, University of Southern California, Los Angeles, CA, United States, 2Biomedical Engineering Department, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran (Islamic Republic of), 3Ming Hsieh Department of Electrical and Computer Engineering, University of Southern California, Los Angeles, CA, United States, 4Division of Vascular Surgery and Endovascular Therapy, Department of Surgery, University of Southern California, Los Angeles, CA, United States, 5Division of Cardiovascular Medicine, University of Southern California, Los Angeles, CA, United States Keywords: Flow, Velocity & Flow, Low-field Motivation: PC-MRI allows for both in-vivo and in-vitro evaluation of complex flow patterns. The accuracy and consistency of these measurements needs to be re-evaluated at new low- and mid-field strengths such as 0.55T. Goal(s): To evaluate flow and velocity patterns using 0.55T PC-MRI to assess the scanner’s suitability for complex flow quantification. Approach: Using an in-vitro human circulatory setup with a patient-specific type-B aortic dissection phantom to measure complex velocity fields. Results: Excellent agreement between MRI-obtained and measured flowrates were observed. Complex rotational flow patterns were captured. Results are consistent within slices and experimental conditions, demonstrating the efficacy of 0.55T MRI for flow evaluation. Impact: This study establishes the viability of 0.55T MRI for phase contrast imaging for three-dimensional velocity field measurements. The findings validate the consistency of flow quantification, and open new avenues for further opportunities on complex flow visualization. |
| 3374.
 | 142 | The Staging of Lower Limb Venous Thrombosis using DANTE-MP2RAGE Sequence: A Comparative Analysis Mingxia Tan1, Lanbin Huang2, Zeping Liu3, Liping Liao2, Zehe Huang2, Song Chen2, Qizeng Ruan2, Qingchun Li2, Mengzhu Wang Wang4, and Chen ZHAO5
1Radiologist, The First Pepole's Hospital of Qinzhou, Qinzhou, China, 2Radiologist, The first People's hospital of Qinzhou, Qinzhou, China, 3Radiologist, Guangdong Provincial People's Hospital, Guangzhou, China, 4MR Research Collaboration, Beijing, China, 5MR Research Collaboration, Siemens Healthineers, Beijing, China Keywords: Blood Vessels, Vessels, MP2RAGE;Venous thrombosis;T1 mapping;Dante Motivation: The aim of this work was to investigate fast T1-mapping for the characterization of deep vein thrombosis
(DVT). Goal(s): Discuss the research value of Dante-MP2RAGE technology in venous thrombosis of the lower extremities Approach: Select 15 patients with venous thrombosis in the lower extremities and analyze the correlation between the T1 value formed by Dante-MP2RAGE and the stage of venous thrombosis in the lower extremities. Results: DANTE-MP2RAGE is related to venous thrombosis in the lower extremities and provides an accurate T1 value。 Impact: Without injecting contrast agents, it provides an effective quantitative indicator for the staging of venous thrombosis in the lower extremities. |
| 3375.
 | 143 | Non-invasive estimation of relative pressure in the murine aortic arch using virtual work-energy (vWERP) Patrick Winter1,2,3, Kristina Andelovic4, Thomas Kampf3,5, Volker Herold3, Alma Zernecke6, Peter Michael Jakob3, Wolfgang Rudolf Bauer7, David Marlevi8,9, and Susanne Schnell1,2
1Department of Medical Physics, University of Greifswald, Greifswald, Germany, 2Department of Radiology, Northwestern University Feinberg School of Medicine, Chicago, IL, United States, 3Experimental Physics V, University of Wuerzburg, Wuerzburg, Germany, 4Department of Functional Materials in Medicine and Dentistry, University of Wuerzburg Institute of Functional Materials and Biofabrication (IFB), Wuerzburg, Germany, 5Department of Diagnostic and Interventional Radiology, University Clinics Wuerzburg, Wuerzburg, Germany, 6Institute of Experimental Biomedicine, University Clinics Wuerzburg, Wuerzburg, Germany, 7Department of Medical Clinic and Policlinic I, University Clinics Wuerzburg, Wuerzburg, Germany, 8Department of Molecular Medicine and Surgery, Karolinska Institutet, Solna, Sweden, 9Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA, United States Keywords: Flow, Blood vessels Motivation: MRI-based relative pressure is a promising imaging biomarker. A new technique, vWERP, improves pressure estimations compared to more simplified approaches. Validated in clinical settings, it's unexplored in mouse models. Goal(s): To apply the vWERP algorithm to MRI-microscopy for pressure measurements in wild-type and atherosclerotic mouse models. Approach: 4D flow MRI was performed in wild-type and ApoE-/- mice. Post-processing involved segmenting the aorta, defining analysis planes, and calculating pressure drops using the vWERP algorithm for analysis. Results: Using vWERP with 4D flow MRI shows promise for studying vascular disease hemodynamics. Preliminary findings suggest pressure as a robust parameter to examine changes in CVD progression. Impact: Application of vWERP to MRI-microscopy in mice reveals high potential for assessing cardiovascular disease progression, particularly in studying pressure changes. This new diagnostic tool benefits vascular health studies in preclinical settings and may be used to study atherosclerotic plaque development. |
| 3376.
 | 144 | MRI findings of aneurysmal inside and walls associated with sac shrinkage after endovascular aortic repair Teppei Nakagomi1, Takahiko Mine2, Masashi Abe2, Tetsuro Sekine3, Daisuke Yasui3, Rika Kobayashi1, Seigoh Happoh2, Shinpei Ikeda2, Yasuhiro Kawase4, Masahiro Fujii4, Hiromitsu Hayashi1, and Shin-ichiro Kumita1
1Dapartment Of Radiology, Nippon Medical School Hospital, Tokyo, Japan, 2Dapartment Of Radiology, Nippon Medical School Chiba Hokusoh Hospital, Inzai, Japan, 3Dapartment Of Radiology, Nippon Medical School Musashikosugi Hospital, Kawasaki, Japan, 4Department Of Cardiothoracic Surgery, Nippon Medical School Chiba Hokusoh Hospital, Inzai, Japan Keywords: Vascular, Cardiovascular, Abdominal aortic aneurysm Motivation: To survey radiographical parameters to predict outcomes after EVAR. Goal(s): To reveal new MRI findings associated with aneurysmal shrinkage. Approach: Various MRI findings were extracted from fifty patients and the relationship between each finding and aneurysmal volume change was analyzed. Results: Lack of endoleak, endoleak with clear boundary shapes, homogenous signal pattern or uncomplex heterogenous signal pattern of intra-aneurysmal thrombus, and aneurysmal wall enhancement and thickening were noted as the factors for sac shrinkage.
Impact: Some specific MRI findings as lack of endoleak, clear endoleak boundary, homogenous or uncomplex heterogenous thrombus, and aneurysmal wall enhancement thickening were noted as the factors for sac shrinkage. |