Evaluation of required saline volume in dynamic contrast-enhanced computed tomography using saline flush technique

Usefulness of contrast injection methods with the implanted port system during dynamic hepatic computed tomography scan

INTRODUCTION

To compare the contrast enhancement (CE) value, injection rate and contrast material (CM) volume with and without the implanted port system during dynamic hepatic computed tomography (CT) scan.

METHODS

In total, 169 patients who underwent dynamic hepatic CT scan were assigned to one of two protocols. In particular, 87 patients underwent scanning with the conventional CM injection protocol and 82 patients underwent scanning with the implanted port system and a 20 % reduction in the CM volume. The CE value in the aorta at the level of the celiac artery's origin at the arterial phase and the hepatic parenchyma at the portal vein phase, the injection rate and the CM volume during CT scan with and without the implanted port system were measured and compared.

RESULTS

The CE values in the aorta at the level of the celiac artery's origin were 272.5 ± 47.0 Hounsfield unit (HU) with the implanted port system and 275.9 ± 46.3 HU without the implanted port system. The CE values in the hepatic parenchyma were 45.5 ± 8.2 HU with the implanted port system and 47.7 ± 8.5 HU without the implanted port system. The injection rates and CM volumes were 2.7 mL/s and 83.7 mL with the implanted port system and 3.3 mL/s and 103.7 mL without the implanted port system, respectively.

CONCLUSION

The implanted port system was useful in reducing the injection rate and CM volume by approximately 20 % during dynamic hepatic CT scan without reducing the CE value.

IMPLICATIONS FOR PRACTICE

This study showed that the use of an implanted port system will attenuate the injection rate, consequently mitigating the perception of warmth and vascular discomfort. Consequently, this intervention can possibly alleviate the patient's burden.

Contrast Kinetics in CT Coronary Angiography

Computed tomography coronary angiography (CTCA) is a technically demanding radiological investigation that requires adequate opacification of coronary arteries at peak aortic enhancement phase, with minimal or no contrast in the superior vena cava and right-sided cardiac chambers to avoid streak artifacts of dense contrast. Therefore, it is prudent to know about contrast media, contrast kinetics, and contrast injection protocols. This article attempts to describe the essentials of various aspects of contrast media that should be considered for CTCA along with an in-depth analysis of contrast kinetics that every radiologist should know for obtaining adequate opacification of coronary arteries.

Effect of a saline flush technique for head and neck imaging in dual-energy CT: improvement of image quality and perivenous artefact reduction using virtual monochromatic imaging

AIM

To evaluate the effect of the saline flush (SF) technique on the depiction of lesions and the reduction of perivenous artefacts in the head and neck region using dual-energy computed tomography (CT) with virtual monochromatic imaging (VMI).

MATERIALS AND METHODS

Fifty patients with head and neck cancer were divided into two groups: group A, without a SF and group B, with a 30-ml SF. All images were acquired using fast kilovolt-switching CT (Revolution HD, GE Healthcare, Milwaukee, WI, USA). Contrast-to-noise ratios (CNRs) of the lesions were calculated at VMI energy levels ranging from 40 to 80 keV. Subjective analysis of overall image quality, delineation of lesions, and perivenous artefacts was conducted by two reviewers at both VMI energy level 40 keV and the optimal energy level (which showed optimal CNR by objective analysis).

RESULTS

Optimal energy level was 63 keV for group A and 61 keV for group B. At VMI energy levels ranging from 40 to 80 keV, the CNR was higher for group B. The highest subjective overall image quality was shown for group B at the optimal energy level (subjective image quality mean value, 3.40). Subjective delineation of lesions was comparable. The perivenous artefact score was significantly higher for group B (2.44 versus 2.74 [p<0.05] at 40 keV, 3.20 versus 3.46 [p<0.05] at the optimal energy level).

CONCLUSION

The SF technique results in an improvement of lesion CNR and a reduction of perivenous artefacts in VMI using duel-energy CT, especially at 40 keV.

The Effect of Contrast Material on Radiation Dose at CT: Part I. Incorporation of Contrast Material Dynamics in Anthropomorphic Phantoms

Purpose To develop a method to incorporate the propagation of contrast material into computational anthropomorphic phantoms for estimation of organ dose at computed tomography (CT). Materials and Methods A patient-specific physiologically based pharmacokinetic (PBPK) model of the human cardiovascular system was incorporated into 58 extended cardiac-torso (XCAT) patient phantoms. The PBPK model comprised compartmental models of vessels and organs unique to each XCAT model. For typical injection protocols, the dynamics of the contrast material in the body were described according to a series of patient-specific iodine mass-balance differential equations, the solutions to which provided the contrast material concentration time curves for each compartment. Each organ was assigned to a corresponding time-varying iodinated contrast agent to create the contrast material-enhanced five-dimensional XCAT models, in which the fifth dimension represents the dynamics of contrast material. To validate the accuracy of the models, simulated aortic and hepatic contrast-enhancement results throughout the models were compared with previously published clinical data by using the percentage of discrepancy in the mean, time to 90% peak, peak value, and slope of enhancement in a paired t test at the 95% significance level. Results The PBPK model allowed effective prediction of the time-varying concentration curves of various contrast material administrations in each organ for different patient models. The contrast-enhancement results were in agreement with results of previously published clinical data, with mean percentage, time to 90% peak, peak value, and slope of less than 10% (P > .74), 4%, 7%, and 14% for uniphasic and 12% (P > .56), 4%, 12%, and 14% for biphasic injection protocols, respectively. The exception was hepatic enhancement results calculated for a uniphasic injection protocol for which the discrepancy was less than 25%. Conclusion A technique to model the propagation of contrast material in XCAT human models was developed. The models with added contrast material propagation can be applied to simulate contrast-enhanced CT examinations. ^© RSNA, 2017 Online supplemental material is available for this article.

[Effects of Mathematical Analysis of Test Injection on the CT Value Estimation of the Aorta]

The circulation time and the mechanical acceleration time (MA time) of an automatic injector were simulated using pharmacokinetic analysis. The addition method and transfer-function method, which are mathematical techniques used for analyzing the test bolus method in multi-detector computed tomography, were used to verify the accuracy of estimation of the time-enhancement curve (TEC) of the main bolus. The TEC estimated using the addition method, and the TEC of the main bolus matched completely only if the MA time of the automatic injector was set to 0 seconds. Moreover, the estimation accuracy of the TEC deteriorated when the MA time was set according to the TEC estimated by the addition method. In contrast, the TEC estimated using the transfer-function method, except when the MA time of the automatic injector was 0 seconds, had higher accuracy than the TEC estimated using the addition method. In this study, the addition method, a number of additions of TEC, and MA time of the automatic injector were found to have a negative effect on the estimation accuracy of the main bolus. The use of the transfer-function method for determining the TEC and the MA time has a positive effect on the estimation accuracy of the main bolus.

Contrast medium administration and image acquisition parameters in renal CT angiography: what radiologists need to know

Over the last decade, exponential advances in computed tomography (CT) technology have resulted in improved spatial and temporal resolution. Faster image acquisition enabled renal CT angiography to become a viable and effective noninvasive alternative in diagnosing renal vascular pathologies. However, with these advances, new challenges in contrast media administration have emerged. Poor synchronization between scanner and contrast media administration have reduced the consistency in image quality with poor spatial and contrast resolution. Comprehensive understanding of contrast media dynamics is essential in the design and implementation of contrast administration and image acquisition protocols. This review includes an overview of the parameters affecting renal artery opacification and current protocol strategies to achieve optimal image quality during renal CT angiography with iodinated contrast media, with current safety issues highlighted.

Automated contrast medium monitoring system for computed tomography--Intra-institutional audit

The aim of this study was to analyze the usage and the data recorded by a RIS-PACS-connected contrast medium (CM) monitoring system (Certegra(®), Bayer Healthcare, Leverkusen, Germany) over 19 months of CT activity. The system used was connected to two dual syringe power injectors (each associated with a 16-row and a high definition 64-row multidetector CT scanner, respectively), allowing to manage contrast medium injection parameters and to send and retrieve CT study-related information via RIS/PACS for any scheduled contrast-enhanced CT examination. The system can handle up to 64 variables and can be accessed via touchscreen by CT operators as well as via a web interface by registered users with three different hierarchy levels. Data related to CM injection parameters (i.e. iodine concentration, volume and flow rate of CM, iodine delivery rate and iodine dose, CM injection pressure, and volume and flow rate of saline), patient weight and height, and type of CT study over a testing period spanning from 1 June 2013 to 10 January 2015 were retrieved from the system. Technical alerts occurred for each injection event (such as system disarm due to technical failure, disarm due to operator's stop, incomplete filling of patient data fields, or excessively high injection pressure), as well as interoperability issues related to data sending and receiving to/from the RIS/PACS were also recorded. During the testing period, the CM monitoring system generated a total of 8609 reports, of which 7629 relative to successful injection events (88.6%). 331 alerts were generated, of which 40 resulted in injection interruption and 291 in CM flow rate limitation due to excessively high injection pressure (>325 psi). Average CM volume and flow rate were 93.73 ± 17.58 mL and 3.53 ± 0.89 mL/s, and contrast injection pressure ranged between 5 and 167 psi. A statistically significant correlation was found between iodine concentration and peak IDR (rs=0.2744, p<0.0001), as well as between iodine concentration and iodine dose (rs=0.3862, p<0.0001) for all CT studies. Automated contrast management systems can provide a full report of contrast use with the possibility to systematically compare different contrast injection protocols, minimize errors, and optimize organ-specific contrast enhancement for any given patient and clinical application. This can be useful to improve and harmonize the quality and consistency of contrast CT procedures within the same radiological department and across the hospital, as well as to monitor potential adverse events and overall costs.

[Assessment of the effects of administering a saline solution flush after contrast medium injection using different injection durations and flush methods]

The purpose of administering a saline solution flush after contrast medium injection is to more effectively utilize the contrast medium remaining in the vessels from the subclavian vein to the superior vena cava. In order to investigate the effects of administering a saline solution flush after a contrast medium injection, we evaluated the effects of various contrast medium injection durations and injection methods on the time-density curve (TDC) using a custom-made TDC measurement phantom. The TDC was found to have a biphasic appearance, showing a rapid increase after the arrival of contrast medium in the target region followed by a slower increase from an inflection point at 25 s after the start of contrast medium injection, reflecting the differences in circulatory dynamics for each duration. The results showed that the effect of saline solution flush was allowed the differences by contrast medium duration at the inflection point. Specifically, when the saline solution flush was administered before the inflection point, the CT number was increased, and when it was administered after the inflection point, contrast enhancement was prolonged. With regard to the method in which the saline solution flush is administered before the inflection point, it was found that injecting a mixture of contrast medium and saline solution before the saline solution flush reduced the degree of inflection of the TDC, resulting in a more stable TDC.

Cardiothoracic CT angiography: current contrast medium delivery strategies

OBJECTIVE

Over the last decade, rapid technologic evolution in CT has resulted in improved spatial and temporal resolution and acquisition speed, enabling cardiothoracic CT angiography to become a viable and effective noninvasive alternative in the diagnostic algorithm. These new technologic advances have imposed new challenges for the optimization of contrast medium delivery and image acquisition strategies.

CONCLUSION

Thorough understanding of contrast medium dynamics is essential for the design of effective acquisition and injection protocols. This article provides an overview of the fundamentals affecting contrast enhancement, emphasizing the modifications to contrast material delivery protocols required to optimize cardiothoracic CT angiography.

Current contrast media delivery strategies for cardiac and pulmonary multidetector-row computed tomography angiography

Recent advances in multidetector-row computed tomography (MDCT) have led to substantial improvements in coverage area, acquisition speed, and temporal/spatial resolution, which have strengthened the performance of thoracic and cardiac MDCT angiography but have also imposed new challenges for optimization of contrast medium enhancement and scan acquisition strategies. Understanding contrast media dynamics is fundamental for the design of scan acquisition and injection protocols. This article examines the fundamentals of the physiological and contrast delivery factors that determine the quality of contrast enhancement, emphasizing the modifications required in contrast delivery protocols for optimizing cardiothoracic MDCT angiography with modern-era MDCT scanners.

Intravenous contrast medium administration and scan timing at CT: considerations and approaches

The continuing advances in computed tomographic (CT) technology in the past decades have provided ongoing opportunities to improve CT image quality and clinical practice and discover new clinical CT imaging applications. New CT technology, however, has introduced new challenges in clinical radiology practice. One of the challenges is with intravenous contrast medium administration and scan timing. In this article, contrast medium pharmacokinetics and patient, contrast medium, and CT scanning factors associated with contrast enhancement and scan timing are presented and discussed. Published data from clinical studies of contrast medium and physiology are reviewed and interpreted. Computer simulation data are analyzed to provide an in-depth analysis of various factors associated with contrast enhancement and scan timing. On the basis of basic principles and analysis of the factors, clinical considerations and modifications to protocol design that are necessary to optimize contrast enhancement for common clinical CT applications are proposed.