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Medical doctors usually inject dextran at a constant flow rate. However, they often cannot obtain clear angioscopy visibility because the flushing out of the blood is insufficient. Good flushing conditions producing clear angioscopy visibility will increase the rate of success of angioscopy operations. This study aimed to determine a way to improve the clarity for angioscopy under different values for the parameters of the injection waveform, endoscope position, and catheter angle. We also determined the effect of a stepwise waveform for injecting the dextran only during systole while synchronizing the waveform to the cardiac cycle. To evaluate the visibility of the blood-vessel walls, we performed a computational fluid dynamics (CFD) simulation and calculated the visible area ratio (VAR), representing the ratio of the visible wall area to the total area of the wall at each point in time. Additionally, the normalized integration of the VAR called the area ratio (ARVAR) represents the ratio of the visible wall area as a function of the dextran injection period. The results demonstrate that the ARVAR with a stepped waveform, bottom endoscope, and three-degree-angle catheter results in the highest visibility, around 25 times larger than that under the control conditions: a constant waveform, a center endoscope, and 0 degrees. This set of conditions can improve angioscopy visibility.<\/jats:p>","DOI":"10.3390\/jfb13020069","type":"journal-article","created":{"date-parts":[[2022,6,1]],"date-time":"2022-06-01T12:48:31Z","timestamp":1654087711000},"page":"69","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["A Parametric Study of Flushing Conditions for Improvement of Angioscopy Visibility"],"prefix":"10.3390","volume":"13","author":[{"given":"Kohei","family":"Mitsuzuka","sequence":"first","affiliation":[{"name":"Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan"},{"name":"Graduate School of Biomedical Engineering, Tohoku University, 6-6 Azaaoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6597-7769","authenticated-orcid":false,"given":"Yujie","family":"Li","sequence":"additional","affiliation":[{"name":"Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan"},{"name":"Centre for Healthy Futures, Torrens University Australia, 1-51 Foveaux Street, Sydney, NSW 2010, Australia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Toshio","family":"Nakayama","sequence":"additional","affiliation":[{"name":"National Institute of Technology, Nara College, 22 Yatacho, Yamatokoriyama 639-1080, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hitomi","family":"Anzai","sequence":"additional","affiliation":[{"name":"Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Daisuke","family":"Goanno","sequence":"additional","affiliation":[{"name":"Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan"},{"name":"Graduate School of Biomedical Engineering, Tohoku University, 6-6 Azaaoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0982-8210","authenticated-orcid":false,"given":"Simon","family":"Tupin","sequence":"additional","affiliation":[{"name":"Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0118-1160","authenticated-orcid":false,"given":"Mingzi","family":"Zhang","sequence":"additional","affiliation":[{"name":"Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan"},{"name":"Macquarie Medical School, Faculty of Medicine, Health, and Human Sciences, Macquarie University, 75 Talavera Rd., Sydney, NSW 2109, Australia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Haoran","family":"Wang","sequence":"additional","affiliation":[{"name":"Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Kazunori","family":"Horie","sequence":"additional","affiliation":[{"name":"Department of Cardiology, Sendai Kousei Hospital, 4-15 Hirose, Aoba-ku, Sendai 980-0873, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8571-6400","authenticated-orcid":false,"given":"Makoto","family":"Ohta","sequence":"additional","affiliation":[{"name":"Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2022,6,1]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"e005375","DOI":"10.1161\/CIRCOUTCOMES.118.005375","article-title":"Mortality from Ischemic Heart Disease: Analysis of Data from the World Health Organization and Coronary Artery Disease Risk Factors from NCD Risk Factor Collaboration","volume":"12","author":"Nowbar","year":"2019","journal-title":"Circ. 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