Improved image quality and micronodule detection in thyroid spectral computed tomography using modified swimmer's position.

Abstract

Background: Spectral computed tomography (CT) can be used as a valuable complement to ultrasound (US) in the detection of thyroid nodules. This study sought to investigate the effects of various arm positions during thyroid spectral CT scans in terms of radiation exposure, image quality, and micronodule detection (≤10 mm).

Methods: A total of 180 patients (mean age: 48 years; 136 females) who underwent thyroid spectral CT were assigned to the traditional position (TDN; n=60), swimmer's position (SWIM; n=60), and modified swimmer's position (M-SWIM; n=60) groups. Image quality in the plain, arterial, and venous phases was assessed using a 4-point grading scale, the signal-to-noise ratio (SNR), and the contrast-to-noise ratio (CNR). Radiation exposure was assessed using the volume computed tomography dose index (CTDI_vol), dose-length product (DLP), effective dose of the neck (ED_N), and effective dose of the thyroid (ED_T). The micronodule detection rates for spectral CT and US were compared using the pathology detection rate as a reference.

Results: The M-SWIM group had a significantly higher proportion of 4-point grading, SNR, and CNR than the TDN and SWIM groups (all P<0.001). The CTDI_vol, DLP, ED_N, and ED_T were similar among the three groups (all P>0.05). The micronodule detection rate was higher in the M-SWIM group than the TDN and SWIM groups (total: 90.6% vs. 70.1% vs. 46.8%; benign: 89.1% vs. 66.7% vs. 45.5%; malignant: 94.3% vs. 79.5% vs. 51.5%; all P<0.001), but comparable to that of the US group (total: 90.6% vs. 91.2%; benign: 89.1% vs. 90.6%; malignant: 94.3% vs. 92.5%; all P>0.05).

Conclusions: The proposed M-SWIM improved the image quality of thyroid spectral CT without increasing the radiation dose, and significantly enhanced the micronodule detection rate.