Shu-Hang Ng

Choledochal cyst associated with acute acalculous cholecystitis

A 7-year-old girl underwent laparotomy for suspected acute appendicitis. Instead, bile peritonitis with hydrops of gallbladder and normal appendix were noted. Dilatation of the CBD was observed, and choledochal cyst was documented by intraoperative cholangiography. Cholecystectomy and T-tube placement were performed. Postoperative follow-up by ultrasound lasted for 9 months. The CBD remained the same size without clinical manifestation.

Role of Triphasic Computed Tomography during Arterial Portography in Distinguishing Pseudolesion and Hepatocellular Carcinoma

To retrospectively evaluate the clinical efficacy of triphasic computed tomography during arterial portography (CTAP) for a pretreatment survey of patients with suspected hepatocellular carcinoma (HCC) and to compare the dynamic image features of HCCs and pseudolesions during triphasic CTAP.Between May 2007 and September 2010, 129 patients with known or suspected HCC underwent triphasic helical computed tomography (THCT) and triphasic CTAP at our institution. The HCC image characteristics and pseudolesion dynamic changes in enhancement, size, shape, and location were reviewed. The sensitivity, positive predictive rate (PPV), and area under the receiver operating characteristic curve of triphasic CTAP were calculated and compared.Of 129 patients, 103 with 184 HCCs and 134 pseudolesions were enrolled. The PPVs for triphasic CTAP and monophasic CTAP were 90.2% and 53.9%, respectively (P＜0.05). During the precontrast phase of triphasic CTAP, low attenuation of HCCs and pseudolesions occurred in 96.3% and 3% of the cases, respectively (P＜0.05). After contrast administration, 133 (99.3%) low-attenuation pseudolesions that appeared during the first phase of CTAP, 66 (49.3%) during the second phase, and 121 (90.3%) during the third phase because iso-attenuated to normal liver parenchyma. The proportion of HCCs with low attenuation during the first, second, and third CTAP phases was 100%, 97.5%, and 97.5%, respectively. During the third phase of triphasic CTAP, low attenuation was more likely associated with HCC than pseudolesions (97.5% vs. 9.7%, P＜0.05).The PPV was significantly increased by triphasic CTAP compared to monophasic CTAP. The dynamic image features of triphasic CTAP are useful for distinguishing pseudolesions from HCC.

Feasibility of Low Tube Voltage for Comprehensive Cardiac Computed Tomography in Patients with a Normal Body Mass Index: Image Quality and Radiation Dose

The purpose of this study was to compare the image quality and radiation dose between cardiac computed tomography (CCT) protocols using low tube voltage (100 kV) and conventional tube voltage (120 kV) with a wide ECG modulation pulsing window in patients with a normal body-mass-index (BMT).Fifty-two patients with a normal BMI (18-24 kg/m(superscript 2)) and coronary calcium score＜400 Agatston units underwent retrospectively ECG-gated 64-slice CCT with an ECG pulsing window of 40-80% of the R-R interval. Twenty-six patients were assigned to the 100 kV group and the other twenty-six patients were assigned to the 120 kV group randomly, The image quality of the coronary arteries was assessed by a 4-point scale (I=non-diagnostic to 4=excel lent). The effective radiation dose, image noise, mean CT-attenuation values, contrast-to-noise (CNR) and signal-to-noise (SNR) ratios were also evaluated. The 100 kV group and 120 kV group showed no significant differences with respect to image quality scores, CNR and SNR. Even with an average of 38.2% dose reduction, the image quality scores were excellent in 89.6% and good in 10.4% of the coronary segments in the 100 kV group. Interobserver agreement in evaluating image quality (κ= 0.91) was good. The 100 kV group had a significantly lower effective radiation dose (mean ± SD, 7.6± 0.7 vs 12.3 ± 1.5 mSv), higher image noise levels and mean CT-attenuation values than those of the 120 kV group.Although the image noise level was higher than that in the 120 kV group, the 100 kV protocol significantly reduced the radiation dose of CCT in patients with a normal BMI while its image quality scores, CNR, SNR were not significantly affected.