Comparison between bolus tracking and timing-bolus techniques for renal computed tomographic angiography in normal cats

Feasibility exploration of myocardial blood flow synthesis from a simulated static myocardial computed tomography perfusion via a deep neural network

BACKGROUND

 Myocardial blood flow (MBF) provides important diagnostic information for myocardial ischemia. However, dynamic computed tomography perfusion (CTP) needed for MBF involves multiple exposures, leading to high radiation doses.

OBJECTIVES

 This study investigated synthesizing MBF from simulated static myocardial CTP to explore dose reduction potential, bypassing the traditional dynamic input function.

METHODS

 The study included 253 subjects with intermediate-to-high pretest probabilities of obstructive coronary artery disease (CAD). MBF was reconstructed from dynamic myocardial CTP. A deep neural network (DNN) converted simulated static CTP into synthetic MBF. Beyond the usual image quality evaluation, the synthetic MBF was segmented and a clinical functional assessment was conducted, with quantitative analysis for consistency and correlation.

RESULTS

 Synthetic MBF closely matched the referenced MBF, with an average structure similarity (SSIM) of 0.87. ROC analysis of ischemic segments showed an area under curve (AUC) of 0.915 for synthetic MBF. This method can theoretically reduce the radiation dose for MBF significantly, provided satisfactory static CTP is obtained, reducing reliance on high time resolution of dynamic CTP.

CONCLUSIONS

 The proposed method is feasible, with satisfactory clinical functionality of synthetic MBF. Further investigation and validation are needed to confirm actual dose reduction in clinical settings.

Anatomical and Three-Dimensional Study of the Female Feline Abdominal and Pelvic Vascular System Using Dissections, Computed Tomography Angiography and Magnetic Resonance Angiography

This study describes the anatomical characteristics of the abdominal and pelvic vascular system of two healthy mature female cats via three-dimensional contrast enhanced computed tomography angiography, non-contrast enhanced magnetic resonance angiography and three-dimensional printing. Volume-rendering computed tomography angiography images were acquired from the ventral aspect using RadiAnt, Amira and OsiriX MD Dicom three-dimensional formats, and three-dimensional printing was obtained and compared with the corresponding computed tomography angiography images. Non-contrast enhanced magnetic resonance angiography was made using the time-of-flight imaging in ventral, oblique and lateral views. In addition, three cadavers with colored latex injection were dissected to facilitate the identification of the vascular structures. Three-dimensional computed tomography angiography showed the main vascular structures, whereas with the time-of-flight blood appeared with a high signal intensity compared with associated abdominal and pelvic tissues. Three-dimensional computed tomography angiography images and time-of-flight sequences provided adequate anatomical details of the main arteries and veins that could be used for future feline anatomical and clinical vascular studies of the abdomen and pelvis.

Image quality and radiation dose of different scanning protocols in DSCT cardiothoracic angiography for children with tetralogy of fallot

The aim of this study was to investigate the image quality and radiation dose of different scanning protocols in dual-source CT cardiothoracic angiography for children with tetralogy of Fallot (TOF). Seventy-five consecutive children with known or suspected TOF were enrolled to undergo prospective ECG-triggering sequential dual-source CT (DSCT) cardiothoracic angiography. According to the scanning protocols, these patients were randomly divided into 3 groups: fixed delay time (FDT, n = 25, group A), automatic bolus-tracking (ABT, n = 25, group B) and manual bolus-tracking (MBT, n = 25, group C). Subjective and objective image quality were evaluated. The radiation doses were recorded. The image quality scores of group C were significantly higher than those of group A and B. The absolute value of difference (D-value) on CT attenuation between left (CT_LV) and right ventricle (CT_RV) in group C was significantly lower than that in group A and B. The total effective dose of groups A, B and C were 0.39 ± 0.06 mSv, 0.40 ± 0.07 mSv and 0.40 ± 0.08 mSv, respectively. There was no significant difference among 3 groups (P = 0.722). Scanning protocol has significantly impacts on the image quality of cardiovascular structures for TOF patients. Compared with the conventional scanning protocols FDT and ABT, the MBT technique provides high image quality and achieves more homogenous attenuation among different patients with TOF.

Optimization of scan delay for multi-phase computed tomography by using bolus tracking in normal canine kidney

This study was performed to optimize scan delays for canine kidney by using a bolus-tracking technique. In six beagle dogs, computed tomography (CT) of the kidney was performed three times in each dog with different scan delays after a bolus-tracking trigger of 100 Hounsfield units (HU) of aortic enhancement. Delays were 5, 20, 35, and 50 sec for the first scan, 10, 25, 40, and 55 sec for the second scan, and 15, 30, 45, and 60 sec for the third scan. The renal artery-to-vein contrast difference peaked at 5 sec, and the renal cortex-to-medulla contrast difference peaked at 10 sec. The renal cortex-to-medulla contrast difference approached zero at a scan delay of 30 sec after the bolus trigger. For the injection protocol used in this study, the optimal scan delay times for renal arterial, corticomedullary, and nephrographic phases were 5, 10, and 30 sec after triggering at 100 HU of aortic enhancement using the bolus-tracking technique. The bolus-tracking technique is useful in multi-phase renal CT study as it compensates for different transit times to the kidney among different animals, requires a small dose of contrast media, and does not require additional patient radiation exposure.

Estimation of time to peak contrast enhancement of the aorta and liver for dual-phase computed tomography on the basis of contrast medium arrival time, injection duration, and injection technique in dogs

OBJECTIVE To evaluate the accuracy of estimating time to peak enhancement (TPE) of the aorta and liver parenchyma on the basis of contrast medium arrival time in the aorta, injection duration, and injection technique in dogs. ANIMALS 18 dogs of specific body weight categories (≥ 2 dogs/category) with no liver abnormalities detected via CT. PROCEDURES Dogs were randomly assigned within weight categories to receive contrast medium IV at a fixed injection rate (5 mL/s) or fixed injection duration (20 seconds). Time-contrast attenuation curves were generated from dynamic CT scans acquired at the hepatic hilus. Data collected for contrast medium arrival time and injection duration were used to estimate TPEs of the aorta and liver, and results were compared with the observed TPEs for the aorta and liver. RESULTS Contrast medium arrival time, injection duration, and injection technique were significantly associated with observed values for aortic TPE and explained 96.1% of variation in TPE. For the fixed rate technique, the regression equation for estimating aortic TPE was 0.8 × (injection duration + contrast medium arrival time) + 1.6. For the fixed duration technique, the regression equation changed by only the constant (-2.6). However, the hepatic TPE estimated from the 3 predictor variables was not significantly different from the mean of observed TPEs. CONCLUSIONS AND CLINICAL RELEVANCE Aortic TPE could be accurately estimated from contrast medium arrival time, injection duration, and injection technique in dogs with apparently healthy livers. The regression equations derived from this relationship can be used to improve the efficiency of dual-phase CT of the liver in dogs.

EFFECTS OF TWO CONTRAST INJECTION PROTOCOLS ON FELINE AORTIC AND HEPATIC ENHANCEMENT USING DYNAMIC COMPUTED TOMOGRAPHY

This prospective study compared aortic and hepatic enhancement achieved using a contrast injection protocol with a fixed rate of 5 ml/s vs. that achieved using a protocol with fixed injection duration of 20 s in eight cats. Cats were assigned into two groups (Group 1, rate 5 ml/s; Group 2, duration 20 s). The dose of contrast was the same in both groups (740 mgI/kg). Regions of interest (ROI) were drawn in the aorta and liver for transverse scans acquired at the hepatic hilus. Time to peak aortic enhancement occurred significantly earlier in Group 1 (M = 11s, SD = 1.63) than in Group 2 (M = 25.5 s, SD = 2.51). Peak aortic enhancement was significantly higher in Group 1 (M = 1906.51 HU, SD = 368.64) than in Group 2 (M = 745.08 HU, SD = 201.84). Duration of aortic enhancement equal to or above 300 HU was statistically longer in Group 2 (M = 24.5 s, SD = 8.39) than in Group 1 (M = 10 s, SD = 1.63). There were no significant differences in time to peak liver enhancement, peak liver enhancement, or duration of hepatic arterial phase between groups. Findings supported the hypothesis that longer injection duration results in a broader bolus geometry with a longer time to peak and a lower peak aortic enhancement in cat. This strong influence of injection duration on timing of aortic enhancement may help future users optimize protocols for CT angiography of the aorta and multiphasic evaluation of the liver, pancreas, and small intestine.