title: Contrast-enhanced spiral CT of the head and neck: comparison of contrast material injection rates.
abstract: OBJECTIVE
  Contrast-enhanced spiral CT studies of the head and neck are performed frequently using contrast material volumes of approximately 30 g iodine and a scan delay of 30-45 seconds. Because little is known about the effects of contrast material injection rates on tissue enhancement, this was prospectively investigated in our study.
  
  
  METHODS
  Ninety-seven patients underwent spiral CT of the head and neck. Each patient was assigned randomly to one of four groups who received 100 mL of nonionic contrast material (300 mg I/mL) at different monophasic injection flow rates with 1.5, 2, 3, and 4 mL/s. Scanning started after a constant delay of 35 seconds. The attenuation of the carotid artery, jugular vein, and sternocleidomastoid muscle was measured over time and the attenuation of the submandibular and thyroid gland was evaluated. Vascular attenuation of at least 150 HU was considered to be sufficient.
  
  
  RESULTS
  The mean scan time was 33+/-5 seconds. The study, using an injection rate of 2 mL/s, showed the longest time of sufficient overall (arterial and venous) vessel attenuation (27+/-4 seconds, P< or =.008). The injection flow rate did not influence significantly muscular attenuation (mean enhancement during scan time: 9+/-7 HU). The 1.5 mL/s protocol showed the lowest attenuation values of the submandibular gland (81+/-12 HU) and the highest attenuation values of the thyroid gland (164+/-22 HU), but the attenuation of the thyroid gland was not statistically different from that revealed by the 2 mL/s protocol.
  
  
  CONCLUSIONS
  Using 100 mL of intravenous contrast material with 300 mg I/mL for spiral CT studies of the entire head and neck, the optimal injection flow is 2 mL/s, whereas lower flow rates resulted in insufficient venous enhancement.
authors.affiliation: Department of Radiology, University Hospital Graz, Austria.
authors.forename: R
authors.initials: R
authors.lastname: Groell
authors.forename: P
authors.initials: P
authors.lastname: Willfurth
authors.forename: G J
authors.initials: GJ
authors.lastname: Schaffler
authors.forename: R
authors.initials: R
authors.lastname: Mayer
authors.forename: F
authors.initials: F
authors.lastname: Schmidt
authors.forename: M M
authors.initials: MM
authors.lastname: Uggowitzer
authors.forename: M
authors.initials: M
authors.lastname: Tillich
authors.forename: B
authors.initials: B
authors.lastname: Genser
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media / Q000008:administration & dosage*; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D007275:Injections, Intravenous; D007472:Iohexol / Q000031:analogs & derivatives*; D007822:Laryngeal Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D009303:Nasopharyngeal Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D009367:Neoplasm Staging; D011856:Radiographic Image Enhancement; D011857:Radiographic Image Interpretation, Computer-Assisted; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed
chemical_list: D003287:Contrast Media; D007472:Iohexol; C038192:iopromide