Takeshi Nakaura MD, Presenter: Nothing to Disclose

Yuji Iyama MD, Abstract Co-Author: Nothing to Disclose

Shinichi Tokuyasu RT, Abstract Co-Author: Employee, Koninklijke Philips NV

Masafumi Kidoh, Abstract Co-Author: Nothing to Disclose

Kazunori Harada, Abstract Co-Author: Nothing to Disclose

Yasuyuki Yamashita MD, Abstract Co-Author: Consultant, DAIICHI SANKYO Group

Naritsugu Sakaino, Abstract Co-Author: Nothing to Disclose

Seitaro Oda MD, Abstract Co-Author: Nothing to Disclose

Low kilo-voltage (kVp) CT is well suited for low contrast and low radiation dose cardiac CT; however, increased image noise is a problem. The recent introduced knowledge-based iterative model reconstruction (IMR) dramatically reduces the image noise. We evaluated the feasibility of a low contrast-, low radiation dose protocol for cardiac CT using 80 kVp and IMR.

This prospective study received institutional review board approval; prior informed consent to participate was obtained from all patients. Thirty patients underwent a low contrast-, low radiation dose protocol with 80 kVp, 923 mA and prospective ECG gating. A 40% reduced contrast dose (222 mgI/kg) was delivered during 12 sec. We also enrolled 30 patients who underwent our conventional protocol with 120kVp, 992 mA and prospective ECG gating. The 80-kVp images were reconstructed with FBP, hybrid iterative reconstruction (HIR) and IMR. We evaluated CT number, image noise and contrast to noise ratio (CNR) of ascending aorta between 120 kVp images and 80 kVp images reconstructed with FBP, HIR and IMR with the Dunnett test. We also compared noise reduction rate of HIR and IMR as compared with FBP reconstruction with the two tailed t-test. Two independent readers assessed image contrast, image noise, image sharpness, unfamiliar texture and overall image quality on a 4-point scale.

The estimated ED was 75% lower with the 80- than the 120 kVp protocol (1.3 mSv vs 5.3 mSv). The CT number of 80 kVp images was significantly higher than that of 120 kVp images (517.1 HU ± 64.8 vs 431.4 HU ± 51.6, p < 0.01).　The noise reduction rate was significantly higher with IMR (76.2% ± 4.6) than with HIR (50.0% ± 1.5) (FBP: 119.0 HU ± 39.9; HIR: 59.4 HU ± 19.6; IMR: 27.4 HU ± 7.3) (p < 0.01). The CNR of 80 kVp images with IMR was significantly higher than that of 120 kVp images (19.8 ± 3.9 vs 13.3 ± 2.5, p < 0.01). There was no significant difference in the score of unfamiliar texture between 80-kVp images with IMR and 120-kVp images (p > 0.05).

The 80 kVp scans with the IMR yields higher image quality for cardiac CT with 75% decreased radiation dose and 40% decreased contrast dose as compared with the 120 kVp protocol with FBP reconstruction.

The low tube voltage scan with IMR is well suited for a low contrast-, low radiation dose protocol for cardiac CT.

Nakaura, T, Iyama, Y, Tokuyasu, S, Kidoh, M, Harada, K, Yamashita, Y, Sakaino, N, Oda, S, Low Contrast- and Low Radiation Dose Protocol in Cardiac CT: Usefulness of Low Tube Voltage and Knowledge-based Iterative Model Reconstruction Algorism.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14045788.html