Hybrid digital subtraction angiography: initial clinical experience.

Hybrid digital subtraction angiography was performed after modification of a DSA system. Alternate high voltage (110-120 kV) and low voltage (65-70 kV) were obtained within short time intervals of 60-70 ms with a high voltage switching generator. Experimental phantom studies revealed the exposure dose per single image of hybrid subtraction was approximately 30% of that of conventional DSA. The SNR of hybrid subtraction was improved by increasing the exposure dose and application of postprocessing programs. Clinical application of intraarterial and intravenous DSA revealed that soft tissue artifacts were removed surprisingly well, but image quality decreased because of lowered SNR. Frame integration and matched filtering improved image quality of hybrid subtraction.