A comparison of DECT reconstructions, for optimal image quality for contouring lymph nodes in relation to breast cancer radiation treatment

Purpose: The purpose of this study is to examine at which kV, the optimal image quality for contouring lymph nodes often radiated in c. mamma patients can be obtained, utilizing a DECT scanner with virtual monoenergetic reconstructions.
Method: DECT scans of 5 head-neck patients were utilized, with scan lengths including relevant lymph node regions, typically contoured in c. mamma patients. Each patient was scanned with a Twin-Beam DECT protocol. The scans were reconstructed into five image sets of 50 kV, 70 kV, 90 kV, 110 kV and 130 kV. Two blinded VGA
studies were performed by five oncologists, to determine the best image quality to contour lymph nodes on. One VGA was presented with no contours, and the other with specific regional lymphatics contours (level 2, 3, 4 axilla, IMN and interpectoralis). SNR and CNR were measured in each reconstruction, and evaluated in relation to VGA scores. Kappa statistics were applied, to measure both inter- and intrarater reliability amongst the participating oncologists, and to reflect if the contours influenced their perception of good image quality.
Results: In both VGA studies, 70 kV was ranked the highest by the five oncologists, with 50 and 90 kV scoring marginally lower. CNR and SNR values peaked at 70 and 90 kV respectively.