Optimal KVp for Image Quality and Noise in Iodine Contrast in Head CTA
L Johnson1*, M Yester1, G Barnes1,2, (1) University of Alabama, Birmingham, Birmingham, AL, (2) X-Ray Imaging Innovations, Birmingham, ALSU-E-I-53 Sunday 3:00:00 PM - 6:00:00 PM Room: Exhibit Hall
Purpose: For brain CT perfusion it is well established that 80 kVp is optimal. Although neuro-CT angiography is somewhat similar, emphasis is on the detection of aneurysms and related vascular pathologies throughout the brain. Thus it is necessary to visualize small and large blood vessels with contrast material, as well as form multi-planar views and 3D images, so image quality and noise in addition to contrast are important for thin slices. A study was initiated to determine the optimal kVp for neuro-CTA.
Methods: A customized version of a commercial head phantom (CIRS 007TE-27 medium adult head CT dose phantom) was purchased to facilitate quantitative measurements with iodinated contrast material, contrast for white and gray matter, and to maintain the ability to perform dosimetry. The customization consisted of adding four 25 mm holes, 35 mm from the center arranged at 45 degree angles from the center, with solid rods equivalent with brain, white, and gray matter, as well as four fillable vials were included for study of contrast agents. Dosimetry measurements were carried out with standard pencil chamber and with 0.6 cc ionization chamber. For study of the optimal kVp for a head CTA, the vials were filled with four different concentrations of contrast, approximating low to medium concentrations that would be expected in such a study. The standard CTA protocol was followed, 64 x 0.625, pitch 0.53, rotation speed 0.5 second, and CTDIvol was kept constant for each kVp.
Results: The best contrast was observed at 80 kVp; however, in order to achieve noise in CTA low enough to be clinically useful there may be issues with tube current capability for a clinical technique. Clinical investigation is underway.
Conclusions: The best balance of contrast and noise currently possible will be achieved at 100 kVp in a clinical scan.