Contrast Material Injection Rate Research Articles

CT Angiography in the Emergency Department: Maximizing Contrast Enhancement and Image Quality While Minimizing Radiation Dose and Contrast Material Volume: Vascular/Interventional Radiology.

CT angiographic image quality and radiation dose can be optimized for each patient by applying knowledge of the principles of intravenous contrast material flow and the factors that influence contrast enhancement.

CT of the Abdomen with Reduced Tube Voltage in Adults: A Practical Approach.

Recent innovations in computed tomographic (CT) hardware and software have allowed implementation of low tube voltage imaging into everyday CT scanning protocols in adults. CT at a low tube voltage setting has many benefits, including (a) radiation dose reduction, which is crucial in young patients and those with chronic medical conditions undergoing serial CT examinations for disease management; and (b) higher contrast enhancement. For the latter, increased attenuation of iodinated contrast material improves the evaluation of hypervascular lesions, vascular structures, intestinal mucosa in patients with bowel disease, and CT urographic images. Additionally, the higher contrast enhancement may provide diagnostic images in patients with renal dysfunction receiving a reduced contrast material load and in patients with suboptimal peripheral intravenous access who require a lower contrast material injection rate. One limitation is that noisier images affect image quality at a low tube voltage setting. The development of denoising algorithms such as iterative reconstruction has made it possible to perform CT at a low tube voltage setting without compromising diagnostic confidence. Other potential pitfalls of low tube voltage CT include (a) photon starvation artifact in larger patients, (b) accentuation of streak artifacts, and (c) alteration of the CT attenuation value, which may affect evaluation of lesions on the basis of conventional enhancement thresholds. CT of the abdomen with a low tube voltage setting is an excellent radiation reduction technique when properly applied to imaging of select patients in the appropriate clinical setting.

Effect of Injection Rate of Contrast Material on CT of Hepatocellular Carcinoma

The purpose of this study was to assess the effect of two injection rates of contrast material (3 mL/sec and 5 mL/sec) in hepatic arterial dominant phase MDCT for the detection of small (< 2 cm) hepatocellular carcinomas. The injection rates 3 mL/sec and 5 mL/sec were used prospectively in imaging examinations of patients with the suspected diagnosis of hepatocellular carcinoma. Each group consisted of 30 patients by chance. The group that received injections at 3 mL/sec had 35 hepatocellular carcinoma lesions, and the 5 mL/sec group had 41 lesions. In all patients the dose and concentration of contrast material were 100 mL and 350 mg/mL iodine (total dose of iodine, 35 g). In each patient a mini-test-bolus technique was used with an additional 15 mL of contrast material to determine optimal scan delay after administration of contrast material. Receiver operating characteristic analysis was used to assess diagnostic performance with the two injection rates of contrast material. There were no statistically significant differences between the two groups in regard to area under the curve and sensitivity. These values for the 3 mL/sec group were 0.97 and 28/35 (80%) and for the 5 mL/sec group were 0.96 and 36/41 (88%). However, the specificity and positive predictive values at 3 mL/sec (236/250 [95%] and 28/42 [67%]) were significantly higher than those at 5 mL/sec (227/265 [86%] and 36/73 [49%]) (p < 0.05). These results suggest there were more false-positive findings of contrast-enhanced lesions in cirrhotic livers on hepatic arterial dominant phase images obtained after injection of contrast material at 5 mL/sec than on images obtained after injection at 3 mL/sec. In the detection of small hypervascular hepatocellular carcinoma in cirrhotic liver, the risk of false-positive findings of lesions on hepatic arterial dominant phase images is significantly greater with the higher injection rate (5 mL/sec) than with the medium rate (3 mL/sec).

Effect of contrast injection protocol with dose tailored to patient weight and fixed injection duration on aortic and hepatic enhancement at multidetector-row helical CT.

The aim of this study was to investigate the effect of a contrast material injection protocol with dose and injection rate of contrast material tailored to patient weight (dose tailored to patient weight and fixed injection duration). Hepatic helical CT was performed in 92 patients with chronic liver damage with a dose of 1.4 ml (518 mgI) at a rate of 0.056 ml/s per kilogram body weight of Iopamidol 370. Attenuation values of liver and aorta were measured for calculation of maximum aortic and hepatic enhancement, time to maximum hepatic enhancement, and end of hepatic arterial phase. Correlation coefficients between the injection rate and the four parameters were r=0.008, 0.057, 0.167, and 0.036, and there were no statistically significant correlations between the injection rates and the four parameters. In our injection protocol, uniform temporal scan window may be achieved and the injection rate can be reduced in lighter patients without reducing the degree of enhancement in the aorta and the liver.

Hypervascular hepatocellular carcinoma: can double arterial phase imaging with multidetector CT improve tumor depiction in the cirrhotic liver?

We assessed the efficacy of double arterial phase CT with multidetector CT for the detection of hypervascular hepatocellular carcinoma in the cirrhotic liver. Double arterial phase images with multidetector CT were evaluated using quantitative, qualitative, and receiver operating characteristic analyses for 59 patients with 78 hepatocellular carcinomas. Early and late arterial phase (double arterial phase) CT scans were obtained at a fixed time of 25 and 40 sec, respectively, after administration of contrast material. Total dose and injection rate of contrast material were 100 mL and 3 mL/sec, respectively. On the basis of the receiver operating characteristic curves, the mean area under the curve values of the late (0.98) and combined arterial phase CT scans (0.98) were equivalent, and both were significantly greater than the mean of the early arterial phase CT scans (0.842) for detecting hepatocellular carcinoma (p < 0.05). The mean relative sensitivity values obtained with the late (69/78, 88%) and combined arterial phase CT scans (70/78, 90%) were also equivalent and were significantly greater than those obtained with the early arterial phase CT scans (52/78, 67%; p < 0.001). Double arterial phase CT with multidetector CT showed no significant improvement in effectiveness compared with single late arterial phase CT used alone for detecting hypervascular hepatocellular carcinoma in the cirrhotic liver.

Aortic enhancement during abdominal CT angiography: correlation with test injections, flow rates, and patient demographics.

The goal of our study was to determine the effect of contrast material injection rate and patient demographic variables on vascular enhancement for abdominal CT angiography and compare test injection results with actual patterns of vascular enhancement. One hundred twenty-five patients underwent abdominal CT angiography. For each patient, CT attenuation values (Hounsfield units) of the aorta were determined before and after IV contrast administration, every 3 sec between 21 and 60 sec. A peak aortic enhancement value and the time needed to reach peak and aortic enhancement thresholds of 150 and 200 H were determined. All patients received 150 ml of nonionic contrast material at 3 ml/sec in 25 patients and 4 ml/sec in 100 patients. A test injection of 15 ml was used to compute a scan delay in 46 patients. Patient age, sex, weight, injection rate, and test injection results were compared with vascular enhancement patterns. For the 125 patients, the mean aortic enhancement at each time point was greater than 150 H. Patient weight was inversely correlated (r2 = -.62) with aortic enhancement. The test injection did not accurately predict actual aortic enhancement peak value or time. Test injection delay time was significantly correlated with time to reach aortic enhancement thresholds of 150 and 200 H. The 4 ml/sec rate resulted in a higher peak aortic enhancement (320+/-58 H versus 281+/-49 H) (mean +/- SD, p < .01) that was reached quicker than with the 3 ml/sec injection rate (45+/-5 sec versus 52+/-5 sec) (p < .01). Injecting at 4 ml/sec resulted in greater aortic enhancement values at 24-45 sec, whereas 3 ml/sec produced significantly better aortic enhancement at 54-60 sec. The test injection correlated better with time to reach specific aortic enhancement thresholds than with time to peak aortic enhancement. For a given amount of contrast material, faster injection rates resulted in greater vascular enhancement that occurred earlier.

Imaging of the liver with helical CT: a survey of scanning techniques.

We conducted a survey of the members of the Society of Computed Body Tomography/Magnetic Resonance to assess current techniques in liver imaging using helical CT. The survey, which was designed to update earlier surveys from 1987 and 1993, included a questionnaire distributed to 77 members of the Society of Computed Body Tomography/Magnetic Resonance. Forty-nine members responded, representing 28 institutions. In 1993, 19% (5/26) of institutions used helical scanners, compared with 82% (23/28) in 1996. The group of institutions with helical CT served as the focus of this survey. In 1993, 58% of institutions used 1-cm collimation: in 1996, 78% (18/23) used thinner, 7- to 8-mm collimation. In 1987, 41% used power injectors compared with 85% in 1993 and 100% in 1996. In 1996, monophasic injections were used by 96% (22/23) of institutions. In 1993, most institutions used a contrast material injection rate of 1.5-2.0 ml/sec; in 1996, most used a 2.5-3.0 ml/sec injection rate. In 1993, 96% of institutions used 125-150 ml of contrast material; in 1996, 57% (13/23) of institutions used 125-150 ml and 30% of institutions used less than 125 ml of contrast material. A delay time of 21-45 see was used by 83% of institutions in 1993, whereas in 1996, 83% (19/23) of institutions used a longer delay time of 50-80 sec. In 1996, 13% of institutions used an individual scan delay technology and all institutions performed multiphasic scanning of hypervascular lesions. The availability of helical CT has changed radiologists' approach to liver imaging. The greatest effects of which are a more widespread use of power injectors, longer delay times, thinner collimation, increased contrast material injection rates, decreased contrast material volumes, and multiphasic scanning.

From the RSNA refresher courses. Challenges of pediatric spiral CT.

Spiral technology has expanded the usefulness of computed tomography (CT) in the evaluation of pediatric diseases. Even though spiral CT requires shorter total scanning times, image degradation by patient motion is still a problem in very young patients, and oral and intravenous sedatives are administered to minimize this problem. Optimal parenchymal enhancement depends on the amount and injection rate of contrast material and the timing of the onset of scanning. All these are more variable in studies of children than in adults, with the latter being the most complicated. Spiral CT of the pediatric chest is most useful for evaluating anastomotic dehiscence and stenosis in lung transplant recipients, pulmonary nodules in children with malignant disease likely to disseminate to the lung, and great vessel anomalies; for staging pulmonary tumors; and for dynamic imaging to identify various diseases that cause pulmonary dysfunction. Important applications of spiral CT of the pediatric abdomen and pelvis include evaluating the liver for acquired vascular abnormalities and vascular tumors, staging and preoperative assessment of renal tumors, and evaluating inflammatory pelvic lesions.

Detection of Liver Metastases: Usefulness of Dynamic Spiral CT during the Portal Phase with a Higher IV Injection Rate of Contrast Material

Detection of Liver Metastases: Usefulness of Dynamic Spiral CT during the Portal Phase with a Higher IV Injection Rate of Contrast Material