Radiation dose and image quality of high-pitch emergency abdominal CT in obese patients using third-generation dual-source CT (DSCT).

In this third-generation dual-source CT (DSCT) study, we retrospectively investigated radiation dose and image quality of portal-venous high-pitch emergency CT in 60 patients (28 female, mean age 56 years) with a body mass index (BMI) ≥ 30 kg/m2. Patients were dichotomized in groups A (median BMI 31.5 kg/m2; n = 33) and B (36.8 kg/m2; n = 27). Volumetric CT dose index (CTDIvol), size-specific dose estimate (SSDE), dose length product (DLP) and effective dose (ED) were assessed. Contrast-to-noise ratio (CNR) and dose-independent figure-of-merit (FOM) CNR were calculated. Subjective image quality was assessed using a five-point scale. Mean values of CTDIvol, SSDE as well as normalized DLP and ED were 7.6 ± 1.8 mGy, 8.0 ± 1.8 mGy, 304 ± 74 mGy * cm and 5.2 ± 1.3 mSv for group A, and 12.6 ± 3.7 mGy, 11.0 ± 2.6 mGy, 521 ± 157 mGy * cm and 8.9 ± 2.7 mSv for group B (p < 0.001). CNR of the liver and spleen as well as each calculated FOM CNR were significantly higher in group A (p < 0.001). Subjective image quality was good in both groups. In conclusion, third-generation abdominal high-pitch emergency DSCT yields good image quality in obese patients. Radiation dose increases in patients with a BMI > 36.8 kg/m2.

Semi-automatic CT-angiography based evaluation of the aortic annulus in patients prior to TAVR: interchangeability with manual measurements.

To compare a semi-automatic software tool for the measurement of aortic annulus dimensions with manual measurements by expert readers and to analyze whether and to what extent interchangeability exists between semi-automatic and manual measurements. We retrospectively included 374 consecutive patients with high-grade aortic stenosis who had undergone CT-angiography of the heart prior to trans-catheter aortic valve replacement (TAVR). In independent analyses, two expert readers manually measured aortic annulus dimensions (long axis, short axis, circumference, area) as well as the distance of the coronary ostia from the annulus plane. A third independent reader performed annulus evaluation using a software tool for semi-automatic detection and measurement of the annulus plane. Intraclass correlation coefficients (ICC) and Bland-Altman analysis was used to compare both manual measurements as well as manual and semi-automatic measurements of annulus parameters. Using the respective measurements we simulated size selection for a Sapien XT transcatheter heart valve (THV). Interchangeability of methods was addressed by calculation of the estimated individual equivalence index γ. There was excellent agreement between both expert observers in manual measurements of the annulus with ICC's in the range 0.89-0.94 for all anatomic parameters. Similar high agreements were observed between semi-automatic and manual measurements, with ICC's in the range of 0.89-0.95. THV size recommendation based on manual versus semiautomatic measurements agreed in 80.7% of cases while agreement between both expert readers concerning THV size recommendation was 80.6%. Semi-automatic measurements of anatomic parameters of the aortic root show high agreement and interchangeability with manual measurements in CT-angiography prior to TAVR.

Intravoxel Incoherent Motion Magnetic Resonance Imaging in Partially Nephrectomized Kidneys.

OBJECTIVE: The aim of this study was to investigate the effects of partial nephrectomy (PN) in kidneys with solid renal masses on the apparent diffusion coefficient (ADC) and on intravoxel incoherent motion (IVIM)-based parameters using diffusion-weighted magnetic resonance imaging (DWI). METHODS: Fifteen patients with renal masses underwent DWI before and 1 week after PN on a clinical 3 T scanner using a single-shot echo planar imaging sequence with 10 diffusion weightings. Motion-corrected images were quantified using a monoexponential model fit to calculate ADCs and a segmented biexponential fit to calculate IVIM parameters f (perfusion fraction), Dslow and Dfast ("slow" and "fast" diffusion coefficients), as well as the pseudoflow (PF) Dfast × f. The median values derived from multislice (minimum of 3 slices) regions of interest encompassing the kidney cortex were used for statistical analysis. Estimated glomerular filtration rate values were calculated based on serum creatinine levels on each examination day using the Modification of Diet in Renal Disease formula. RESULTS: The follow-up measurement yielded significantly lower values in the partially nephrectomized kidneys compared with contralateral kidneys for the parameters ADC (P = 0.002), Dfast (P = 0.43), f (P = 0.001), and PF (P = 0.0008). Comparing baseline and follow-up, partially nephrectomized kidneys showed a significant decrease for ADC (P = 0.01), Dfast (P = 0.43), f (P = 0.002), and PF (P = 0.002). Nonnephrectomized kidneys expressed a significant increase for ADC (P = 0.01) and PF (P = 0.01). Follow-up Modification of Diet in Renal Disease showed positive correlations with all DWI parameters in the partially nephrectomized kidneys (ADC: r(2) = 0.63, P = 0.0004; Dfast: r(2) = 0.59, P = 0.0009; f: r(2) = 0.36, P = 0.018; PF: r(2) = 0.60, P = 0.00075) except for Dslow. CONCLUSIONS: Our study suggests that quantitative parameters derived from DWI are highly indicative of renal function. Apparent diffusion coefficients showed substantial differences in the renal cortex after PN, whereas an IVIM analysis delivered additional insight into kidney physiology. Quantitative DWI, particularly perfusion-related IVIM parameters, therefore demonstrated great potential as truly noninvasive biomarker to obtain information about single kidney function.