Improved edge delineation using a low-flow and delayed-phase contrast-enhanced protocol for computed tomography imaging of oral cavity and oropharyngeal malignancies.
OBJECTIVE
To determine whether contrast-enhanced computed tomography (CT) performed with a high flow rate and short delay protocol or a lower flow rate and longer delay protocol resulted in better enhancement of the oral cavity and oropharyngeal tumour and tumour edge delineation.


METHODS
Patients with squamous cell carcinomas of the upper aerodigestive tract (UAT) who underwent contrast-enhanced CT using 100 ml contrast material with 300 mg iodine/ml were selected for this comparison study. The protocols studied used a high flow rate and short scan delay (2 ml/s and 50 s) and a lower flow rate and longer delay (1 ml/s and 100 s). Contrast enhancement by radiodensity in Hounsfield units of the tumour site, poorest and clearest tumour boundaries and contralateral lateral pterygoid muscle were measured using a region of interest tool. A t-test statistical analysis was used to compare both protocols.


RESULTS
The lower flow and longer delay protocol maximized contrast differences at both the poorest and clearest definition boundaries of the tumour (p ≤ 0.01 and p ≤ 0.05, respectively) and the pterygoid muscle (p ≤ 0.01). There was no significant difference in contrast enhancement within the central homogeneous tumour site.


CONCLUSIONS
A lower flow and longer delay protocol (1 ml/s and 100 s) provided better enhancement of the delineation of the tumour edge and surrounding musculature than a high flow rate and short delay protocol (2 ml/s and 50 s). Both protocols achieved similar central tumour enhancement.
Department of Radiology, Guy's and St Thomas' Hospital, London, UK. luisa.disini@jpaget.nhs.uk
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D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging* / Q000473:pathology; D015331:Cohort Studies; D003287:Contrast Media / Q000008:administration & dosage; D006801:Humans; D007472:Iohexol / Q000008:administration & dosage; D008297:Male; D008875:Middle Aged; D009062:Mouth Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D009959:Oropharyngeal Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D011856:Radiographic Image Enhancement / Q000379:methods*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013997:Time Factors
D003287:Contrast Media; D007472:Iohexol