{"id":801,"date":"2017-08-08T08:28:38","date_gmt":"2017-08-08T07:28:38","guid":{"rendered":"https:\/\/journals.myesr.org\/eur-radiol\/2017\/08\/08\/reply-to-4d-flow-mri\/"},"modified":"2025-09-19T10:22:52","modified_gmt":"2025-09-19T09:22:52","slug":"reply-to-4d-flow-mri","status":"publish","type":"post","link":"https:\/\/journals.myesr.org\/eur-radiol\/opinions\/reply-to-4d-flow-mri\/","title":{"rendered":"Reply to: Four-dimensional flow MRI for evaluation of post-stenotic turbulent flow in a phantom: comparison with flowmeter and computational fluid dynamics"},"content":{"rendered":"

Dear Editor,<\/p>\n

We appreciate the interest in our publication entitled “Four-dimensional flow MRI for evaluation of post-stenotic turbulent flow in a phantom: comparison with flowmeter and computational fluid dynamics”[1] The authors raised the issues of definition of Reynold decomposition and PC-MRI turbulence mapping.
\nIn turbulent flows, Reynolds decomposition is a common technique to evaluate velocity fluctuations. As the authors presented, the fluctuating velocity is defined as \"{u^'}=u-bar{u}\" , the difference between instantaneous velocity \"u\" and mean velocity \"bar{u}\". We calculated the root-mean-square (rms) of \"u^'\" using the common definition as<\/p>\n

\"〖u'〗_{rms}= sqrt(frac{1}{N} sum_〖u'〗^2 )=sqrt(frac{1}{N} sum(u-bar{u})^2 )\"\u00a0 [Equation 1]<\/p>\n

Using the authors’ notations, the definition for PC-MRI velocity can be translated as<\/p>\n

\"〖u'〗_{rms}= sqrt(frac{1}{N} sum_〖u'〗^2_{PC-MRI})=sqrt(frac{1}{N} sum(u_{PC-MRI}-bar{u}_{PC-MRI})^2 )\" [Equation 2]<\/p>\n

If the rms of \"u\", instead of \"u^'\", is plotted as indicated, the highest value will appear at the most stenosed region. However, we agree that \"u_{PC-MRI}\" as an outcome of time-averaging in a voxel loses the turbulent characteristics mostly and high \"〖u'〗_{rms}\" values in Figure 5 were largely affected by the artifact due to low signal-to-noise ratio [2]. Interpretation of our data about velocity fluctuations should be limited when analyzing \"u_{PC-MRI}\" as is, and MR turbulent mapping can be performed within a feasible time by applying refined methods as the authors stated.
\nIn the last decade, novel techniques have been developed to evaluate the turbulent characteristics using 4D PC-MRI, which allow faster and more accurate acquisition of flow patterns [3-5]. These techniques applied to measurement of cardiovascular blood flows in vivo have been used to find a correlation between turbulent flow patterns and diagnostic parameters [6; 7]. Together with introduction of a more elaborate method [8], MR turbulent mapping will offer more opportunities to implement 4D PC-MRI in clinical situations and facilitate better understanding of cardiovascular physiology beyond a direct interpretation of flow measurement as in our work.<\/p>\n

If you would like to comment on this letter, please send your comments together with full contact data to office@european-radiology.org<\/a>. Replies and comments will be reviewed by the Editorial Office and published on this website.<\/em><\/p>\n","protected":false},"excerpt":{"rendered":"

Dear Editor, We appreciate the interest in our publication entitled “Four-dimensional flow MRI for evaluation of post-stenotic turbulent flow in a phantom: comparison with flowmeter and computational fluid dynamics”[1] The authors raised the issues of definition of Reynold decomposition and PC-MRI turbulence mapping. In turbulent flows, Reynolds decomposition is a common technique to evaluate velocity […]<\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_et_pb_use_builder":"","_et_pb_old_content":"","_et_gb_content_width":"","inline_featured_image":false,"footnotes":""},"categories":[6],"tags":[],"class_list":["post-801","post","type-post","status-publish","format-standard","hentry","category-opinions"],"acf":[],"yoast_head":"\nReply to: Four-dimensional flow MRI for evaluation of post-stenotic turbulent flow in a phantom: comparison with flowmeter and computational fluid dynamics - European Radiology<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/journals.myesr.org\/eur-radiol\/opinions\/reply-to-4d-flow-mri\/\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Reply to: Four-dimensional flow MRI for evaluation of post-stenotic turbulent flow in a phantom: comparison with flowmeter and computational fluid dynamics - European Radiology\" \/>\n<meta property=\"og:description\" content=\"Dear Editor, We appreciate the interest in our publication entitled “Four-dimensional flow MRI for evaluation of post-stenotic turbulent flow in a phantom: comparison with flowmeter and computational fluid dynamics”[1] The authors raised the issues of definition of Reynold decomposition and PC-MRI turbulence mapping. In turbulent flows, Reynolds decomposition is a common technique to evaluate velocity […]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/journals.myesr.org\/eur-radiol\/opinions\/reply-to-4d-flow-mri\/\" \/>\n<meta property=\"og:site_name\" content=\"European Radiology\" \/>\n<meta property=\"article:published_time\" content=\"2017-08-08T07:28:38+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2025-09-19T09:22:52+00:00\" \/>\n<meta name=\"author\" content=\"editor\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"editor\" \/>\n\t<meta name=\"twitter:label2\" content=\"Estimated reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"2 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\/\/journals.myesr.org\/eur-radiol\/opinions\/reply-to-4d-flow-mri\/\",\"url\":\"https:\/\/journals.myesr.org\/eur-radiol\/opinions\/reply-to-4d-flow-mri\/\",\"name\":\"Reply to: Four-dimensional flow MRI for evaluation of post-stenotic turbulent flow in a phantom: comparison with flowmeter and computational fluid dynamics - European Radiology\",\"isPartOf\":{\"@id\":\"https:\/\/journals.myesr.org\/eur-radiol\/#website\"},\"datePublished\":\"2017-08-08T07:28:38+00:00\",\"dateModified\":\"2025-09-19T09:22:52+00:00\",\"author\":{\"@id\":\"https:\/\/journals.myesr.org\/eur-radiol\/#\/schema\/person\/6b90d4d1c826ba40890f732bdc096ff3\"},\"breadcrumb\":{\"@id\":\"https:\/\/journals.myesr.org\/eur-radiol\/opinions\/reply-to-4d-flow-mri\/#breadcrumb\"},\"inLanguage\":\"en-GB\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\/\/journals.myesr.org\/eur-radiol\/opinions\/reply-to-4d-flow-mri\/\"]}]},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\/\/journals.myesr.org\/eur-radiol\/opinions\/reply-to-4d-flow-mri\/#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\/\/journals.myesr.org\/eur-radiol\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Reply to: Four-dimensional flow MRI for evaluation of post-stenotic turbulent flow in a phantom: comparison with flowmeter and computational fluid dynamics\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\/\/journals.myesr.org\/eur-radiol\/#website\",\"url\":\"https:\/\/journals.myesr.org\/eur-radiol\/\",\"name\":\"European Radiology\",\"description\":\"\",\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\/\/journals.myesr.org\/eur-radiol\/?s={search_term_string}\"},\"query-input\":{\"@type\":\"PropertyValueSpecification\",\"valueRequired\":true,\"valueName\":\"search_term_string\"}}],\"inLanguage\":\"en-GB\"},{\"@type\":\"Person\",\"@id\":\"https:\/\/journals.myesr.org\/eur-radiol\/#\/schema\/person\/6b90d4d1c826ba40890f732bdc096ff3\",\"name\":\"editor\",\"image\":{\"@type\":\"ImageObject\",\"inLanguage\":\"en-GB\",\"@id\":\"https:\/\/journals.myesr.org\/eur-radiol\/#\/schema\/person\/image\/\",\"url\":\"https:\/\/secure.gravatar.com\/avatar\/14699bc4a68dcfa7330767f49cf436219cc6a600e0625083b22c8baadc93ef35?s=96&d=mm&r=g\",\"contentUrl\":\"https:\/\/secure.gravatar.com\/avatar\/14699bc4a68dcfa7330767f49cf436219cc6a600e0625083b22c8baadc93ef35?s=96&d=mm&r=g\",\"caption\":\"editor\"},\"url\":\"https:\/\/journals.myesr.org\/eur-radiol\/author\/editor\/\"}]}<\/script>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"Reply to: Four-dimensional flow MRI for evaluation of post-stenotic turbulent flow in a phantom: comparison with flowmeter and computational fluid dynamics - European Radiology","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/journals.myesr.org\/eur-radiol\/opinions\/reply-to-4d-flow-mri\/","og_locale":"en_GB","og_type":"article","og_title":"Reply to: Four-dimensional flow MRI for evaluation of post-stenotic turbulent flow in a phantom: comparison with flowmeter and computational fluid dynamics - European Radiology","og_description":"Dear Editor, We appreciate the interest in our publication entitled “Four-dimensional flow MRI for evaluation of post-stenotic turbulent flow in a phantom: comparison with flowmeter and computational fluid dynamics”[1] The authors raised the issues of definition of Reynold decomposition and PC-MRI turbulence mapping. In turbulent flows, Reynolds decomposition is a common technique to evaluate velocity […]","og_url":"https:\/\/journals.myesr.org\/eur-radiol\/opinions\/reply-to-4d-flow-mri\/","og_site_name":"European Radiology","article_published_time":"2017-08-08T07:28:38+00:00","article_modified_time":"2025-09-19T09:22:52+00:00","author":"editor","twitter_card":"summary_large_image","twitter_misc":{"Written by":"editor","Estimated reading time":"2 minutes"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"WebPage","@id":"https:\/\/journals.myesr.org\/eur-radiol\/opinions\/reply-to-4d-flow-mri\/","url":"https:\/\/journals.myesr.org\/eur-radiol\/opinions\/reply-to-4d-flow-mri\/","name":"Reply to: Four-dimensional flow MRI for evaluation of post-stenotic turbulent flow in a phantom: comparison with flowmeter and computational fluid dynamics - European Radiology","isPartOf":{"@id":"https:\/\/journals.myesr.org\/eur-radiol\/#website"},"datePublished":"2017-08-08T07:28:38+00:00","dateModified":"2025-09-19T09:22:52+00:00","author":{"@id":"https:\/\/journals.myesr.org\/eur-radiol\/#\/schema\/person\/6b90d4d1c826ba40890f732bdc096ff3"},"breadcrumb":{"@id":"https:\/\/journals.myesr.org\/eur-radiol\/opinions\/reply-to-4d-flow-mri\/#breadcrumb"},"inLanguage":"en-GB","potentialAction":[{"@type":"ReadAction","target":["https:\/\/journals.myesr.org\/eur-radiol\/opinions\/reply-to-4d-flow-mri\/"]}]},{"@type":"BreadcrumbList","@id":"https:\/\/journals.myesr.org\/eur-radiol\/opinions\/reply-to-4d-flow-mri\/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/journals.myesr.org\/eur-radiol\/"},{"@type":"ListItem","position":2,"name":"Reply to: Four-dimensional flow MRI for evaluation of post-stenotic turbulent flow in a phantom: comparison with flowmeter and computational fluid dynamics"}]},{"@type":"WebSite","@id":"https:\/\/journals.myesr.org\/eur-radiol\/#website","url":"https:\/\/journals.myesr.org\/eur-radiol\/","name":"European Radiology","description":"","potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/journals.myesr.org\/eur-radiol\/?s={search_term_string}"},"query-input":{"@type":"PropertyValueSpecification","valueRequired":true,"valueName":"search_term_string"}}],"inLanguage":"en-GB"},{"@type":"Person","@id":"https:\/\/journals.myesr.org\/eur-radiol\/#\/schema\/person\/6b90d4d1c826ba40890f732bdc096ff3","name":"editor","image":{"@type":"ImageObject","inLanguage":"en-GB","@id":"https:\/\/journals.myesr.org\/eur-radiol\/#\/schema\/person\/image\/","url":"https:\/\/secure.gravatar.com\/avatar\/14699bc4a68dcfa7330767f49cf436219cc6a600e0625083b22c8baadc93ef35?s=96&d=mm&r=g","contentUrl":"https:\/\/secure.gravatar.com\/avatar\/14699bc4a68dcfa7330767f49cf436219cc6a600e0625083b22c8baadc93ef35?s=96&d=mm&r=g","caption":"editor"},"url":"https:\/\/journals.myesr.org\/eur-radiol\/author\/editor\/"}]}},"_links":{"self":[{"href":"https:\/\/journals.myesr.org\/eur-radiol\/wp-json\/wp\/v2\/posts\/801","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/journals.myesr.org\/eur-radiol\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/journals.myesr.org\/eur-radiol\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/journals.myesr.org\/eur-radiol\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/journals.myesr.org\/eur-radiol\/wp-json\/wp\/v2\/comments?post=801"}],"version-history":[{"count":1,"href":"https:\/\/journals.myesr.org\/eur-radiol\/wp-json\/wp\/v2\/posts\/801\/revisions"}],"predecessor-version":[{"id":1514,"href":"https:\/\/journals.myesr.org\/eur-radiol\/wp-json\/wp\/v2\/posts\/801\/revisions\/1514"}],"wp:attachment":[{"href":"https:\/\/journals.myesr.org\/eur-radiol\/wp-json\/wp\/v2\/media?parent=801"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/journals.myesr.org\/eur-radiol\/wp-json\/wp\/v2\/categories?post=801"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/journals.myesr.org\/eur-radiol\/wp-json\/wp\/v2\/tags?post=801"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}