gms | German Medical Science

Objective: The major goal of imaging in patients with pituary tumors is to delineate tumor from normal pituitary tissue and to accurately assess cavernous sinus tumor invasion. Until now, MRI is considered as the gold standard. However, MRI is limited regarding sufficient information about the bony anatomy. Contrast enhanced dual-energy CT (DECT) enables the calculation images noise corrects so-called monoenergetic images, that can be calculated between 40-190 keV. Low keV images significantly increase contrast material and soft tissue. In this study we evaluate the sensitivity of histogram regions of interest (ROIs) at 40 and 50 keV to detect adenoma tissue vs. normal pituitary gland/infiltration vs. non-infiltrated cavernous sinus.

Methods: 24 patients with different pituitary gland lesions were prospectively enrolled. All patients underwent DECT imaging. Imaging data was calculated from 40-190 keV in 10 keV intervals. A standard 120 keV polyenergetic CT dataset was reconstructed as a standard CT reference. Objective image quality was evaluated by measuring pituary gland attenuation and image noise in a standardized ROI on all 17 available datasets. The signal to noise ratio was calculated for each dataset by dividing pituary gland attenuation and image noise. Subjective image quality was evaluated by an attending neurosurgeon and radiologist. Both were asked to select

1.

overall best diagnostic image dataset,

2.

datasets that allowed the best delineation of the cavernous sinus and,

3.

best dataset for the delineation of cystic tumor areas.

Results: The monoenergetic datasets of 50 keV and 40 keV showed a higher difference between tumor and sinus cavernosus attenuation (TSAD). The TSAD for the reference polyenergetic 120 keV protocol was 67 HU, for the 50 keV monoenergetic 106 HU and for the 40 keV monoenergetic 163 HU. The 40 and 50 keV monoenergetic images were preferred regarding overall best image quality by the neurosurgeon and radiologist to assess tumor vs. pituitary gland and to assess cavernous sinus infiltration.

Conclusion: Monoenergetic datasets at low keV between 40 + 50 keV significantly improve objective and subjective image quality. DECT may become the CT imaging technique of choice, beside the already known advantages. This could be of interest for intraoperative use or additional information for radiotherapy planning in the postoperative course of residual tumor.