title: Impact of luminal density on plaque classification by CT coronary angiography.
abstract: Non-invasive coronary CT angiography (CCTA) has the potential to characterize the composition of non-calcified coronary plaques. CT-density values characterized by Hounsfield Units (HU) may classify non-calcified plaques as fibrous or lipid-rich, but the luminal density caused by the applied contrast material influences HU in the plaques in vitro. The influence of luminal density on HU in non-calcified plaques in vivo is unknown. Hence the purpose of this study was to test whether plaque characterization by CCTA in vivo depends on luminal density. Two CCTA-scans using two different contrast protocols were obtained from 14 male patients with coronary artery disease. The two contrast protocols applied resulted in high and low luminal density. Eleven non- calcified and 13 calcified plaques were identified and confirmed by intravascular ultrasound. Luminal attenuation differed with the two contrast protocols; 326[284;367] vs. 118[103;134] HU (P < 0.00001). In non-calcified plaques mean HU-values was lower 48[28;69] vs. 11[-4;25] HU (P = 0.004) with the low density protocol. As a consequence three out of eleven non-calcified plaques (27%) were reclassified from fibrous (high) to lipid rich (low). For calcified plaques a less pronounced but still significant difference in HU-values was found with the low luminal density. 770[622;919] vs. 675[496;855] HU (P = 0.02).
  
  
  CONCLUSIONS
  Non-calcified plaques can be identified and classified by CCTA. However, the luminal density affects the absolute HU of both non-calcified and calcified plaques. Characterization and classification of non-calcified plaques by absolute CT values therefore requires standardization of contrast protocols.
authors.affiliation: Department of Cardiology, Aarhus University Hospital, Skejby, Brendstrupgårdsvej 100, 8200 Aarhus N, Denmark. maikendalager@gmail.com
authors.forename: Maiken Glud
authors.initials: MG
authors.lastname: Dalager
authors.forename: Morten
authors.initials: M
authors.lastname: Bøttcher
authors.forename: Gratien
authors.initials: G
authors.lastname: Andersen
authors.forename: Jesper
authors.initials: J
authors.lastname: Thygesen
authors.forename: Erik Morre
authors.initials: EM
authors.lastname: Pedersen
authors.forename: Lone
authors.initials: L
authors.lastname: Dejbjerg
authors.forename: Ole
authors.initials: O
authors.lastname: Gøtzsche
authors.forename: Hans Erik
authors.initials: HE
authors.lastname: Bøtker
mesh_terms: D000368:Aged; D002114:Calcinosis / Q000000981:diagnostic imaging; D003287:Contrast Media; D017023:Coronary Angiography / Q000379:methods*; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging* / Q000378:metabolism; D003718:Denmark; D005355:Fibrosis; D006801:Humans; D007472:Iohexol; D008055:Lipids / Q000032:analysis; D008297:Male; D008875:Middle Aged; D058226:Plaque, Atherosclerotic / Q000737:chemistry / Q000000981:diagnostic imaging*; D011237:Predictive Value of Tests; D011379:Prognosis; D012720:Severity of Illness Index; D014057:Tomography, X-Ray Computed; D018084:Ultrasonography, Interventional
chemical_list: D003287:Contrast Media; D008055:Lipids; D007472:Iohexol
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