Advanced Modeled Iterative Reconstruction in Low-Tube-Voltage Contrast-Enhanced Neck CT: Evaluation of Objective and Subjective Image Quality.

T.J Vogl,T Lehnert,M.H Albrecht,S.C Metzger,J.L Wichmann,B Bodelle,R.W Bauer,J.-E Scholtz,K Hüsers,M Kaup,J.M Kerl

doi:10.3174/ajnr.a4502

Abstract

Dose-saving techniques in neck CT cause increased image noise that can be counteracted by iterative reconstruction. Our aim was to evaluate the image quality of advanced modeled iterative reconstruction (ADMIRE) in contrast-enhanced low-tube-voltage neck CT. Sixty-one patients underwent 90-kV(peak) neck CT by using third-generation 192-section dual-source CT. Image series were reconstructed with standard filtered back-projection and ADMIRE strength levels 1, 3, and 5. Attenuation and noise of the sternocleidomastoid muscle, internal jugular vein, submandibular gland, tongue, subscapularis muscle, and cervical fat were measured. Signal-to-noise and contrast-to-noise ratios were calculated. Two radiologists assessed image noise, image contrast, delineation of smaller structures, and overall diagnostic acceptability. Interobserver agreement was calculated. Image noise was significantly reduced by using ADMIRE compared with filtered back-projection with the lowest noise observed in ADMIRE 5 (filtered back-projection, 9.4 ± 2.4 Hounsfield units [HU]; ADMIRE 1, 8.3 ± 2.8 HU; ADMIRE 3, 6.7 ± 2.0 HU; ADMIRE 5, 5.4 ± 1.7 HU; all, P < .001). Sternocleidomastoid SNR and internal jugular vein-sternocleidomastoid contrast-to-noise ratios were significantly higher for ADMIRE with the best results in ADMIRE 5 (all, P < .001). Subjective image quality and image contrast of ADMIRE 3 and 5 were consistently rated better than those for filtered back-projection and ADMIRE 1 (all, P < .001). Image noise was rated highest for ADMIRE 5 (all, P < .005). Delineation of smaller structures was voted higher in all ADMIRE strength levels compared with filtered back-projection (P < .001). Global interobserver agreement was good (0.75). Contrast-enhanced 90-kVp neck CT is feasible, and ADMIRE 5 shows superior objective image quality compared with filtered back-projection. ADMIRE 3 and 5 show the best subjective image quality.

Highlights

BACKGROUND AND PURPOSEDose-saving techniques in neck CT cause increased image noise that can be counteracted by iterative reconstruction
Image noise was significantly reduced by using advanced modeled iterative reconstruction (ADMIRE) compared with filtered back-projection with the lowest noise observed in ADMIRE 5
Delineation of smaller structures was voted higher in all ADMIRE strength levels compared with filtered back-projection (P Ͻ .001)

Summary

Methods

Sixty-one patients underwent 90-kV(peak) neck CT by using third-generation 192-section dual-source CT. Image series were reconstructed with standard filtered back-projection and ADMIRE strength levels 1, 3, and 5. Sixty-four patients (54.6 Ϯ 16.4 years of age; range, 24 – 82 years) underwent contrast-enhanced neck CT between November 2014 and February 2015. These time intervals were chosen due to a change in tube voltage to 90 kV in the standard the impact of image reconstruction, with very little ADMIRE contribution (level 1) and maximum ADMIRE influence (level 5), with the standard. Images were series reconstructed in clinical routine with an average reconstruction time of 0.5–1 minute for each parameter without differences in time required among the different ADMIRE levels. Indications for contrast-enhanced neck CT included detection or exclusion (n ϭ 26) or follow-up (n ϭ 10) of a tumor or lymphoma in the head and neck region or the visualization or exclusion of a clinically suspected inflammatory process (n ϭ 28)

Results

Discussion

Conclusion