Both sodium phosphate and magnesium citrate provided excellent colon cleansing for CT colonography. Residual stool and fluid were similar in both groups, and fluid attenuation values were closer to optimal in the magnesium citrate group. Since bowel preparation provided by both cathartics was comparable, magnesium citrate should be considered for CT colonography, particularly in patients at risk for phosphate nephropathy.

Purpose Intra-procedural contrast-enhanced computed tomography (CECT) has been proposed to monitor the growth of ablation zone in order to evaluate the efficacy of microwave ablation more accurately than post-ablation image. However, the dilemma of keeping image quality or following dose regulation becomes a huge challenge to apply CECT in real-time monitoring. The purpose of this study is to evaluate the feasibility of applying local highly constrained backprojection reconstruction (HYPR-LR) on periodic CECT image to enhance visualization of ablation zone by statistical and pathological- radiological analysis. Methods Low-dose ( CTDIvol≤1.49 italicmGy), temporal CECT volumes were acquired during microwave ablation on normal porcine liver. HYPR processing was performed on each volume after image registration. Ablation signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were collected to evaluate the degree of enhancement of image quality and ablation zone visualization. Ablation zone was manually segmented on HYPR and non-HYPR images and compared the similarity to gross pathology by measuring Dice coefficient. The dimension of ablation zone was also compared to gross pathology by correlation and measurement difference. Results The SNR and CNR of ablation zone were increased after involving certain slices into HYPR processing. The manually segmented ablation zone was highly similar to gross pathology with DICE coefficient 0.81±0.03, while the low-dose CECT had smaller DICE coefficient with 0.72±0.05. Both HYPR image and low-dose CECT has high correlation coefficient to gross pathology with 0.99 and 0.94, but the variance of measurements were less on HYPR image than those on unprocessed images. The relative difference in area, length of long axis and short axis for HYPR image were 13.1±5.6%, 9.7±4.2% and 15.2±2.8 %, which were less than those for low-dose CECT with 37.5±6.0%, 17.7±2.8% and 28.9±5.4%. Conclusion HYPR processing applied to periodic CECT images can enhance ablation zone visualization. HYPR processing may potentially enable CECT in real-time ablation monitoring under strict regulation of radiation dose.