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Reducing the concentration of contrast medium in dynamic computed tomography of the neck: consequences for image quality, side effects and cost.

OBJECTIVE
To determine the efficacy of two concentrations of nonionic contrast medium (320 and 240 mg iodine/mL; Optiray [ioversol], Mallinckrodt Medical) for enhanced dynamic computed tomography (CT) of the neck.


PATIENTS AND METHODS
Between March 1992 and August 1993, 50 patients undergoing dynamic CT of the neck were assigned randomly to receive either the higher-strength or the lower-strength contrast agent. The amount of opacification was measured objectively, and the quality of the scans was assessed subjectively by two radiologists without knowledge of which contrast agent had been administered. Both immediate and delayed side effects were recorded.


RESULTS
The higher-strength contrast medium gave greater opacification (p = 0.0006, t-test), but both concentrations yielded images of excellent quality (p = 0.125, chi 2 test). The number of patients affected by immediate minor complications was lower with Optiray 240 (11 [44%]) than with Optiray 320 (23 [92%]) (p < 0.001, chi 2 test). The number of patients affected by delayed side effects was similar in the two groups (7 [28%] with Optiray 240 and 9 [36%] with Optiray 320; p > 0.70, chi 2 test). No predictive relation between immediate and delayed complications was observed.


CONCLUSIONS
Because adequate contrast can be obtained with the lower-strength contrast medium, it can be used in dynamic CT of the neck as a means of reducing the cost and the side effects associated with such imaging.