title: Image quality and feasibility of an ultralow-dose high-pitch helical triple-rule-out computed tomography angiography acquired in the caudocranial direction.
abstract: OBJECTIVE
  The aim of this study was to assess the feasibility and image quality of a low-dose triple-rule-out (TRO) computed tomography (CT) angiogram on a second-generation dual-source CT scanner using a high-pitch helical acquisition.
  
  
  METHODS
  Ten men (mean age 56.3 y, average body mass index 24.2) underwent TRO CT angiography using a high-pitch helical acquisition. Patients were imaged from the lung bases to the thoracic inlet in a caudocranial direction. A biphasic injection was administered at 6 mL/s. Study parameters including kVp, mAs, CT dose index volume, dose-length product, and effective dose were calculated. Image quality was independently assessed by 2 cardiothoracic radiologists using the following scale: 1-nondiagnostic; 2-moderately limited diagnostic ability; 3-mild limitation but diagnostic; 4-ideal. For each patient up to 23 structures were evaluated: 17 coronary segments, 3 pulmonary artery levels, 2 aortic sections, and the lung parenchyma. The unpaired t test and the Fisher exact test were used for comparison between patients scored at 80 and 100 kV.
  
  
  RESULTS
  The average CT dose index volume, dose-length product, and effective dose for the TRO scans was 2.65, 81.9, and 1.39 mSv, respectively. Readers 1 and 2 scored 171/203 (83%) and 173/203 (84%) of the evaluated regions as ideal and 26/203 (12.8%) and 24/203 (11.8%) as being mildly limited, respectively. Each reader graded 6/203 (3.9%) as being moderately limited. No areas were nondiagnostic. Patients scanned at 80 kV had a significantly higher number of limited segments for readers 1 (P=0.0012) and 2 (P=0.0027).
  
  
  CONCLUSIONS
  Low-dose, high-image quality TRO scans can be effectively performed using a high-pitch helical acquisition.
authors.affiliation: Department of Diagnostic Radiology and Nuclear Medicine, University of Maryland School of Medicine, Baltimore, MD.
authors.forename: Seth J
authors.initials: SJ
authors.lastname: Kligerman
authors.forename: Charles S
authors.initials: CS
authors.lastname: White
mesh_terms: D000328:Adult; D000368:Aged; D057791:Cardiac Imaging Techniques; D017023:Coronary Angiography / Q000379:methods*; D005240:Feasibility Studies; D006801:Humans; D007089:Image Enhancement; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods; D015900:Radiography, Dual-Energy Scanned Projection / Q000379:methods; D013902:Radiography, Thoracic / Q000379:methods; D012189:Retrospective Studies; D036542:Tomography, Spiral Computed / Q000295:instrumentation / Q000379:methods; D014057:Tomography, X-Ray Computed / Q000379:methods