{"id":3287,"date":"2011-01-24T09:20:11","date_gmt":"2011-01-24T08:20:11","guid":{"rendered":"http:\/\/www.rontgen.com\/wp-doctor\/?p=3287"},"modified":"2011-01-24T09:20:11","modified_gmt":"2011-01-24T08:20:11","slug":"hur-manga-mr-bilder-behovs","status":"publish","type":"post","link":"https:\/\/www.rontgen.com\/wp-doctor\/hur-manga-mr-bilder-behovs","title":{"rendered":"Hur m\u00e5nga MR-bilder beh\u00f6vs"},"content":{"rendered":"<p><img loading=\"lazy\" decoding=\"async\" class=\"alignleft\" style=\"border: 0pt none;\" title=\"Fr\u00e5ga\" src=\"https:\/\/www.rontgen.com\/wp-doctor\/wp-content\/uploads\/2008\/12\/icon_mini_faq.gif\" alt=\"\" width=\"12\" height=\"13\" \/> Hur m\u00e5nga bilder beh\u00f6vs ca f\u00f6r en komplett MRT p\u00e5 en hj\u00e4rna i 2D och 3D? 3D ca 1100 stycken, tror jag eller?<br \/>\nHur stor i Megabyte \u00e4r ett bildsnitt p\u00e5 en MRT hj\u00e4rna?<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignleft\" style=\"border: 0pt none;\" title=\"Svar\" src=\"https:\/\/www.rontgen.com\/wp-doctor\/wp-content\/uploads\/2008\/12\/icon_mini_register.gif\" alt=\"\" width=\"12\" height=\"13\" \/> Storleken i megabyte p\u00e5 en MR-bild hj\u00e4rna beror p\u00e5 vilken typ av unders\u00f6kning som g\u00f6rs, men vid en ganska normal unders\u00f6kning av hj\u00e4rnan anv\u00e4nds en snittjocklek p\u00e5 3 mm och bildmatrisen \u00e4r p\u00e5 512 x 512 bildelement. Varje bildelement har ett bitdjup p\u00e5 12 bitar (= 1,5 byte) vilket ger 4096 olika niv\u00e5er av \u201dgr\u00e5skalan\u201d.<br \/>\nEn 2D (tv\u00e5-dimensionell) bild blir allts\u00e5: 1,5 * 512 * 512 =  393216 byte = 384 kilobyte = 0,375 megabyte. Sen tillkommer n\u00e5gra kilobyte till varje bild i form av en \u201dbild-header\u201d som inneh\u00e5ller information om patienten, hur unders\u00f6kningen gjordes, datum och klockslag, mm.<br \/>\nJag vet inte exakt hur m\u00e5nga 3 mm snitt som beh\u00f6vs f\u00f6r att t\u00e4cka in hela hj\u00e4rnan, men jag uppskattar att stacken b\u00f6r vara ca 15 cm h\u00f6g. Detta skulle inneb\u00e4ra 50 st 2D-bilder om dessa ligger \u201dkant i kant\u201d. S\u00e5ledes blir stacken 50 * 0,375 megabyte = 18,75 megabyte stor. \u00c4ven h\u00e4r tillkommer \u201dbild-header\u201d s\u00e5 storleken blir totalt p\u00e5 ungef\u00e4r 19 megabyte.<\/p>\n<p>F\u00f6r att bilderna ska ta mindre plats i bildarkivet kan dessa komprimeras. Villkoret f\u00f6r kompressionen \u00e4r att ingen information f\u00e5r f\u00f6rloras, s\u00e5 att bilden alltid kan \u00e5terskapas exakt s\u00e5som originalet var. Man pratar om \u201dlossless compression\u201d. Anv\u00e4nds bildkompression kan storleken oftast halveras.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"alignleft\" style=\"border: 0pt none;\" title=\"Svarat av\" src=\"https:\/\/www.rontgen.com\/wp-doctor\/wp-content\/uploads\/2008\/12\/icon_mini_profile.gif\" alt=\"\" width=\"12\" height=\"13\" \/> M. O. Sjukhusfysiker<br \/>\nR\u00f6ntgenavdelningen, Helsingborgs lasarett<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Hur m\u00e5nga bilder beh\u00f6vs ca f\u00f6r en komplett MRT p\u00e5 en hj\u00e4rna i [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[10],"tags":[64,141,145],"class_list":["post-3287","post","type-post","status-publish","format-standard","hentry","category-teknik","tag-bilder","tag-mr","tag-teknik"],"_links":{"self":[{"href":"https:\/\/www.rontgen.com\/wp-doctor\/wp-json\/wp\/v2\/posts\/3287","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.rontgen.com\/wp-doctor\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.rontgen.com\/wp-doctor\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.rontgen.com\/wp-doctor\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.rontgen.com\/wp-doctor\/wp-json\/wp\/v2\/comments?post=3287"}],"version-history":[{"count":0,"href":"https:\/\/www.rontgen.com\/wp-doctor\/wp-json\/wp\/v2\/posts\/3287\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.rontgen.com\/wp-doctor\/wp-json\/wp\/v2\/media?parent=3287"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.rontgen.com\/wp-doctor\/wp-json\/wp\/v2\/categories?post=3287"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.rontgen.com\/wp-doctor\/wp-json\/wp\/v2\/tags?post=3287"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}