Pressure injectors for radiologists: A review and what is new

Risk Factors for Contrast Media Extravasation in Intravenous Contrast-Enhanced Computed Tomography: An Observational Cohort Study

RATIONALE AND OBJECTIVES

To identify the risk factors for contrast media (CM) extravasation and provide effective guidance for reducing its incidence.

MATERIALS AND METHODS

We observed adult inpatients (n = 38 281) who underwent intravenous contrast-enhanced computed tomography between January 1, 2018, and December 31, 2022. Risk factors for CM extravasation were evaluated using univariate and multivariate logistic regression.

RESULTS

Among the 38 281 inpatients who underwent enhanced computed tomography angiography, 3885 received peripherally inserted central venous catheters (PICCs) and 34 396 received peripheral short catheters. In 3885 cases of PICCs, no CM extravasation occurred, but in five cases, ordinary PICCs that are unable to withstand high pressure were mistakenly used; three of those patients experienced catheter rupture, and eventually, all five patients underwent unplanned extubation. Among 34 396 cases of peripheral short catheters, 224 (0.65%) had CM extravasation. Female sex (odds ratio [OR]=1.541, 95% confidence interval [CI]: 1.111-2.137), diabetes (OR=2.265, 95% CI: 1.549-3.314), venous thrombosis (OR=2.157, 95% CI: 1.039-4.478), multi-site angiography (OR=9.757, CI: 6.803-13.994), and injection rate ≥ 3 mL/s (OR=6.073, 95% CI: 4.349-8.481) were independent risk factors for CM extravasation. Due to peripheral vascular protection measures in patients with malignant tumor, there was a low incidence of CM extravasation (OR=0.394, 95% CI: 0.272-0.570).

CONCLUSION

Main risk factors for CM extravasation are female, diabetes, venous thrombosis, multi-site angiography, and injection rate ≥ 3 mL/s. However, patients with malignant tumor have a low incidence of CM extravasation.

CLINICAL IMPACT

Analysis of these risk factors can help reduce the incidence of CM extravasation.

Hemodynamics of Saline Flushing in Endoscopic Imaging of Partially Occluded Coronary Arteries

PURPOSE

Intravascular endoscopy can aid in the diagnosis of coronary atherosclerosis by providing direct color images of coronary plaques. The procedure requires a blood-free optical path between the catheter and plaque, and achieving clearance safely remains an engineering challenge. In this study, we investigate the hemodynamics of saline flushing in partially occluded coronary arteries to advance the development of intravascular forward-imaging catheters that do not require balloon occlusion.

METHODS

In-vitro experiments and CFD simulations are used to quantify the influence of plaque size, catheter stand-off distance, saline injection flowrate, and injection orientation on the time required to achieve blood clearance.

RESULTS

Experiments and simulation of saline injection from a dual-lumen catheter demonstrated that flushing times increase both as injection flow rate (Reynolds number) decreases and as the catheter moves distally away from the plaque. CFD simulations demonstrated that successful flushing was achieved regardless of lumen axial orientation in a 95% occluded artery. Flushing time was also found to increase as plaque size decreases for a set injection flowrate, and a lower limit for injection flowrate was found to exist for each plaques size, below which clearance was not achieved. For the three occlusion sizes investigated (90, 95, 97% by area), successful occlusion was achieved in less than 1.2 s. Investigation of the pressure fields developed during injection, highlight that rapid clearance can be achieved while keeping the arterial overpressure to < 1 mmHg.

CONCLUSIONS

A dual lumen saline injection catheter was shown to produce clearance safely and effectively in models of partially occluded coronary arteries. Clearance was achieved across a range of engineering and clinical parameters without the use of a balloon occlusion, providing development guideposts for a fluid injection system in forward-imaging coronary endoscopes.

Infection prevention and control in computed tomography: creating a national survey

BACKGROUND

Infection prevention and control (IPC) is essential for quality healthcare, with healthcare associated infections (HAI) a known risk to patients requiring medical imaging (MI). To date, few papers have adopted a national approach to understanding or benchmarking the knowledge of, attitudes toward, and practice (KAP) of IPC in the context of MI and no validated surveys or scales are identified in the literature. The Computed Tomography (CT) suite is a unique MI environment where radiographers deliver prescription medicines to patients via intravenous (IV) means through an injector system. This paper describes the development of a survey that informs the use of IPC processes in the CT suite.

METHODS

Standard Precautions via current national guidelines formed the benchmark of the survey, with a KAP survey used as the framework to explore IPC. The questions and associated responses are developed based on the National Health and Medical Research Council (NHMRC) guidelines, industry/professional protocols and adapted to the equipment and practices commonly used in the CT suite of MI departments by radiographers and nurses.

RESULTS

Key survey development steps are described to include the justification of the benchmarking source, the survey framework and design. Detailed information is given to show the evolution of truth statements and sources, KAP question variations, and rationales for the methodology of question responses. National guidelines are mapped to survey questions and responses and pilot testing reflections are included.

CONCLUSION

This paper reports on the construction of a standardised KAP survey for IPC specific to the CT suite in the Australian healthcare setting. The survey is ready for dissemination amongst MI departments. Documented use will aid validation and reliability as a survey tool to measure and map IPC specifically in relation to IV contrast administration.

Performance of Centargo: A Novel Piston-Based Injection System for High Throughput in CE CT

Purpose

To compare an investigational device (MEDRAD^® Centargo CT Injection System, “Centargo”) to the currently available MEDRAD^® Stellant CT Injection System (“Stellant”), in terms of efficiency, injector performance, and user satisfaction.

Patients and Methods

A total of 425 patients at two sites were enrolled; 198 patients in phase one, a randomized study (98 Stellant and 100 Centargo). The second observational phase included 227 patients who were injected with Centargo. Phase one recorded times for setup, disassembly, and patient changeovers. Demographic data, subjective image quality, and injection parameters were collected. Phase two assessed usability via a questionnaire provided to all end-users of both systems (radiographers).

Results

Patient changeover times were statistically significantly faster with Centargo (15.4s ± 8.7s vs 53.7s ± 19.6s, p < 0.001). Centargo day-setup times were similar to Stellant (138.1s ± 92s vs 151.8s ± 30.6s, p = 0.33) and end-of-day-disassembly times were significantly slower (60.6s ± 27s vs 17.1s ± 12.9s, p < 0.001). Based on four different scenarios modelling patient throughput, the projected time savings with Centargo over Stellant was 40–63%, with the highest efficiency improvements for higher throughputs and the use of larger contrast medium bottles. Both Centargo and Stellant usability averaged between “Very Easy” and “Easy” in all responses to the questionnaire. There were no instances of interrupted injections due to communication loss or detected air and no insufficient images due to injector performance. No safety issues were identified.

Conclusion

Centargo was able to demonstrate improved efficiency as compared to Stellant while maintaining injector performance and high usability scores.

Venous air embolism in CT coronary angiography

INTRODUCTION

Venous air embolization (VAE) from IV lines is a risk with IV contrast administration. The incidence of VAE ranges from 7% to 23%. While life-threatening VAE is rare, there is the potential risk of serious cerebrovascular events from paradoxical systemic air embolization (SAE) in patients with congenital intracardiac shunts. CT coronary angiogram (CTCA) hypothetically carries a higher risk of VAE as it requires dual injections as compared to single bolus dose contrast used in CT chest (CTC). The aim of this study was to assess the risk of VAE using CTCA as compared to conventional CTC. The incidence of cardiac shunts and their association with paradoxical SAE were also investigated.

METHODS

A retrospective study was conducted at a tertiary hospital. Adult patients undergoing CTCA and CTC over a 6-month period in 2017 were included. Images were reviewed on PACS for the presence of VAE. Electronic medical records were interrogated for evidence of neurological sequelae or requiring neurological imaging (CTB/MRIB) within 1 month of the initial imaging.

RESULTS

508 patients were included, 408 underwent CTCA and 100 underwent CTC. The VAE incidence in CTCA was 24% (94 patients) and 10% in the CTC (10 patients). This was statistically significant. Among the CTCA group, 36% (108 patients) had an intracardiac shunt. No statistically significant difference in VAE incidence was identified in CTCA patients with shunts vs without shunts. There was no incidence of SAE in both groups.

CONCLUSION

VAE is more common with CTCA than conventional CTC. There were no cases of paradoxical SAE found.

Optimal placement of the region of interest for bolus tracking on brain computed tomography angiography in Beagle dogs

This study aimed to determine the optimal placement of the region of interest (ROI) among four anatomical sites-pulmonary artery (PA), pulmonary vein (PV), aortic arch (AA), and carotid artery (CA)-in computed tomography (CT) brain angiography with automatic bolus tracking in healthy beagle dogs. Six beagles were included, and CT brain angiography was performed four times for each dog, to cover each ROI. The scan parameters, amount, and injection rate of the contrast medium were the same. The major intracranial arteries were selected for quantitative and qualitative evaluation: caudal cerebellar artery (CcA), basilar artery (BA), rostral cerebellar artery (RcA), caudal cerebral artery (CCA), middle cerebral artery (MCA), and rostral cerebral artery (RCA). Quantitative evaluation showed significantly higher CT attenuation values for the RcA, CCA, and MCA in the PA group and RcA and MCA in the PV group than in the CA group. Qualitative analysis revealed significantly higher scores for the BA, CCA, and MCA in the PA and PV groups than in the CA group. Venous contamination did not differ significantly among the ROIs, but the mean scores of the AA and CA groups were higher than those of the PA and PV groups. CT brain angiography using bolus tracking in the beagle dogs showed that the ROI should be placed at the PA or PV rather than at the CA for optimal images with strong contrast enhancement of the BA, RcA, CCA, and MCA and minimal venous contamination.

New infusion device for use in acquisition of images during endovascular procedures: an experimental model

Background

The contrast power injector (CPI) is the gold standard method for injecting contrast with the pressure and flow needed to generate a satisfactory images during endovascular procedures, but it is an expensive tool, narrowing its wide-scale applications. One alternative is the manual injection (MI) method, but this does not generate the pressure required for adequate visualization of anatomy. It is therefore imperative to create an alternative low-cost method that is capable of producing high quality images.

Objectives

To compare the injection parameters of a new mechanical device (Hand-Crank) created in a university hospital with the MI method and with the contrast power injector’s ideal values.

Methods

A circulation phantom was constructed to simulate the pressure in the aorto-iliac territory and the injection parameters of the two methods were compared in a laboratory setting. Student’s t test and the Mann-Whitney test were used for statistical analysis. Three vascular surgery residents (the authors) performed the injections (each performed 9 tests using conventional manual injection and 9 tests using the Hand-Crank, totaling 54 injections).

Results

There were statistical differences between the two methods (p<0.05) in total volume injected until maximum pressure was attained, pressure variation, maximum pressure, total injection time, and time to reach the maximum pressure.

Conclusions

The Hand-Crank can achieve higher maximum pressure, higher average flow, and lower injection time than the manual method. It is a simple, low-cost, and effective tool for enhancing injection parameters in an experimental setup. It could help to produce higher quality images in a clinical scenario.

Parameters of biliary hydrodynamic injection during endoscopic retrograde cholangio-pancreatography in pigs for applications in gene delivery

The biliary system is routinely accessed for clinical purposes via endoscopic retrograde cholangiopancreatography (ERCP). We previously pioneered ERCP-mediated hydrodynamic injection in large animal models as an innovative gene delivery approach for monogenic liver diseases. However, the procedure poses potential safety concerns related mainly to liver or biliary tree injury. Here, we sought to further define biliary hydrodynamic injection parameters that are well-tolerated in a human-sized animal model. ERCP was performed in pigs, and hydrodynamic injection carried out using a novel protocol to reduce duct wall stress. Each pig was subjected to multiple repeated injections to expedite testing and judge tolerability. Different injection parameters (volume, flow rate) and injection port diameters were tested. Vital signs were monitored throughout the procedure, and liver enzyme panels were collected pre- and post-procedure. Pigs tolerated repeated biliary hydrodynamic injections with only occasional, mild, isolated elevation in aspartate aminotransferase (AST), which returned to normal levels within one day post-injection. All other liver tests remained unchanged. No upper limit of volume tolerance was reached, which suggests the biliary tree can readily transmit fluid into the vascular space. Flow rates up to 10 mL/sec were also tolerated with minimal disturbance to vital signs and no anatomic rupture of bile ducts. Measured intrabiliary pressure was up to 150 mmHg, and fluid-filled vesicles were induced in liver histology at high flow rates, mimicking the changes in histology observed in mouse liver after hydrodynamic tail vein injection. Overall, our investigations in a human-sized pig liver using standard clinical equipment suggest that ERCP-guided hydrodynamic injection will be safely tolerated in patients. Future investigations will interrogate if higher flow rates and pressure mediate higher DNA delivery efficiencies.

Injection of contrast media using a large-bore angiography catheter with a guidewire in place: Physical factors influencing injection pressure in cerebral angiography

BACKGROUND

We have used a contrast injection scheme termed as "guided catheterization method (guided method)." By using a large-bore 5-Fr catheter and 0.032-in guidewire, a contrast medium could be injected without removing the guidewire. Using a neurovascular phantom, we studied the influence of leaving the guidewire on the contrast injection pressure. Image quality was compared with that obtained using a 4-Fr regular angiography catheter (conventional method).

METHODS

Actual contrast injection pressure, flow rate, flow volume, and several variables from the time-density curve (TDC) were obtained using the guided method and the conventional method. Catheterization parameters included flow rate, the viscosity of a contrast medium (CM), and catheter length. The pressure limit of a contrast injector was set as 1200 psi. Digital subtraction angiography (DSA) images on the neurovascular phantom were acquired. The DSA images were processed, and TDC on a specific region of interest was obtained. Variables from TDC were calculated and compared between the different catheters.

RESULTS

The ranges of actual contrast injection pressure with the conventional and the guided method were 138-299 psi and 184-451 psi, respectively. A minimal reduction of the actual flow rate was found under some conditions with the guided method. Comparable opacifications in DSA images were achieved in all conditions. Although peak intensity was different by flow rate or CM, all TDC variables did not differ based on the catheter. There were no significant harmful events during the 90 experiments.

CONCLUSIONS

With adjustment of the pressure limit, cerebral angiography using the 5-Fr, large-bore catheter without removal of the guidewire is feasible, safe, and expected to provide image quality comparable to that of the 4-Fr regular catheter.

Disparity of time-contrast curves generated by various types of power injectors used in magnetic resonance imaging

The profiles of time-contrast (TC) -curves from popular MRI injectors derived at the injection site of the attached tube-line system were compared. Variations of TC-profiles were previously reported to potentially influence image quality in time critical MRI measurements. TC-curves from five injectors obtained during commonly used injection protocols were assessed according to representative quality criteria: (1) correlation strength between a fitted boxcar function and the TC-curve (cBCF) and (2) difference between true and expected injection time (dBIT). Additionally, the impact from technical injector properties: pump type, line volume, maximum injection power and type of contrast medium (CM) on the TC-profiles was evaluated. Injectors using a piston-syrinx (PS) mechanism for CM-injection performed significantly better than those working with a peristaltic roller pump (RP) technique. Besides injection mechanism, line filling volume showed a strong influence on the final TC-curves, where larger filling volumes induced worse cBCF- and dBIT-results. Therefore, to achieve an optimal bolus in clinical MRI use of a PS-injector seems recommendable. Besides their pump mechanism, RP-injectors appeared additionally hampered by their high volume line systems, pointing out an unfavourable coinicidence of these technical features in RP-injectors. This should be considered, particularly, in comparative or time-critical MRI-studies.

Clinical evaluation of a novel multibolus contrast agent injection protocol for thoraco-abdominal CT angiography: Assessment of homogeneity of arterial contrast enhancement

PURPOSE

To evaluate the in vivo feasibility of a multibolus contrast agent (CA) injection protocol with a reduced CA volume for thoraco-abdominal CT angiography (CTA) and to compare it to a single-bolus CA injection protocol.

METHOD

63 patients who underwent CTA with the multibolus protocol (60 ml CA) were divided in two groups either without (group 1, n = 48) or with (group 2, n = 15) aortic dissection. The aortic contrast enhancement was measured in group 1 using manual ROI analysis (10 segments), as well as semi-automated linear attenuation profiles. A subgroup (n = 18) of group 1, who also underwent imaging with the single-bolus protocol (94 ml CA), was used to compare both protocols. In group 2, differences in attenuation of the true and the false lumen for both the single- and the multibolus protocol were assessed with ROI attenuation measurements in both lumina. Comparisons were made using Wilcoxon test.

RESULTS

Average attenuation was above 200 HU for 98 % of cases using the multibolus protocol. There was superior contrast homogeneity for the multibolus protocol with a lower standard deviation of attenuation values along the length of the scan (p = 0.003), while average attenuation was higher for the single-bolus protocol (p = 0.002). Prolonged enhancement plateau lead to a more uniform opacification of the true and the false lumen in patients with aortic dissection using the multibolus protocol (p = 0.012).

CONCLUSIONS

The multibolus protocol in thoraco-abdominal CTA is feasible in patients. It shows consistently high arterial enhancement with superior contrast homogeneity compared to a single-bolus protocol in patients with and without aortic dissection.

Injection And Infusion Technology Disruption For Use In MRI

Introduction

Contrast media injections, infusions, or experiments that require a constant volume flow close to or within a very high magnetic field like in magnetic resonance imaging (MRI) require a liquid reservoir and a power unit to deliver the fluid. However, most power units are driven by motors that are either not MRI-compatible or require external connections that restrict mobility and usage. In this paper, the development of a highly portable, lightweight, and MRI-compatible pump system is explained.

Methods

The energy required to deliver the flow is generated using a pressurized bottle concept. The valve inside the bottle is opened to create a flow which should be maintained constant. In order to find the optimal flow resistance for a constant flow rate, we created multiple setups with different flow resistance.

Results

We measured the flow rates for different flow resistances by attaching a restring valve to the bottle. The results clearly show that high flow resistance results in lower and more constant flow rate.

Discussion

The optimal flow rate achieved using our current setup was significantly constant but not ideal. Consequently, such a pump system can be used in many medical applications like MRI-compatible contrast agent injectors.

Effect of catheter diameter and injection rate of flush solution on renal contrast-enhanced ultrasonography with perfluorobutane in dogs

OBJECTIVE

To assess effects of catheter diameter and injection rate of flush solution (saline [0.9% NaCl] solution) on renal contrast-enhanced ultrasonography (CEUS) with perfluorobutane in dogs.

ANIMALS

5 healthy Beagles.

PROCEDURES

CEUS of the kidneys was performed by IV injection of contrast medium (0.0125 mL/kg) followed by injection of 5 mL of saline solution at rates of 1, 3, and 5 mL/s through a 20-gauge or 24-gauge catheter; thus, CEUS was repeated 3 times for each catheter diameter. Time-intensity curves were created for regions of interest drawn in the renal cortex and medulla. Repeatability was determined by calculating the coefficient of variation (CV). Statistical analysis was used to assess whether perfusion variables or CV of the perfusion variables was associated with catheter diameter or injection rate.

RESULTS

Perfusion variables did not differ significantly between catheter diameters. Time to peak enhancement (TTP) in the renal cortex was affected by injection rate, and there were significantly lower values for TTP at higher injection rates. The CEUS variables with the lowest CVs among injection rates were TTP for the renal cortex; the CV for TTP of the renal cortex was the lowest at an injection rate of 5 mL/s.

CONCLUSIONS AND CLINICAL RELEVANCE

Use of a 24-gauge catheter did not alter CEUS with perfluorobutane; therefore, such catheters could be used for CEUS of the kidneys of small dogs. Moreover, a rate of 5 mL/s is recommended for injection of flush solution to obtain greater accuracy for renal CEUS in Beagles.

Contrast-to-Noise Ratio Optimization in Coronary Computed Tomography Angiography: Validation in a Swine Model

RATIONALE AND OBJECTIVES

The accuracy of coronary computed tomography (CT) angiography depends upon the degree of coronary enhancement as compared to the background noise. Unfortunately, coronary contrast-to-noise ratio (CNR) optimization is difficult on a patient-specific basis. Hence, the objective of this study was to validate a new combined diluted test bolus and CT angiography protocol for improved coronary enhancement and CNR.

MATERIALS AND METHODS

The combined diluted test bolus and CT angiography protocol was validated in six swine (28.9 ± 2.7 kg). Specifically, the aortic and coronary enhancement and CNR of a standard CT angiography protocol, and a new combined diluted test bolus and CT angiography protocol were compared to a reference retrospective CT angiography protocol. Comparisons for all data were made using box plots, t tests, regression, Bland-Altman, root-mean-square error and deviation, as well as Lin's concordance correlation.

RESULTS

The combined diluted test bolus and CT angiography protocol was found to improve aortic and coronary enhancement by 26% and 13%, respectively, as compared to the standard CT angiography protocol. More importantly, the combined protocol was found to improve aortic and coronary CNR by 29% and 20%, respectively, as compared to the standard protocol.

CONCLUSION

A new combined diluted test bolus and CT angiography protocol was shown to improve coronary enhancement and CNR as compared to an existing standard CT angiography protocol.

Peripherally inserted central catheters: dependency of radiation exposure from puncture site and level of training

Background Several interventional procedures show a dependency on fluoroscopy times (FT) and level of training. Furthermore, FT and dose area products (DAP) vary depending on access site and target vessel for chest port implantations, but not for other thoracic interventions such as percutaneous coronary interventions. Purpose To evaluate the influence of the combination of venous access site and level of training on FTs and DAPs during peripherally inserted central catheters (PICC) implantations in a large cohort of patients. Material and Methods In this retrospective study, PICC implantations of 681 consecutive patients (385 women, 296 men; mean age = 55.0 ± 16.7 years) were analyzed. Two groups of junior (< 50 interventions) and senior (≥ 50 implantations) radiologists were investigated in respect to FT and DAP during PICC placement procedures. Statistical analysis included the Mann-Whitney U test and the Kruskal-Wallis test. P values < 0.05 were considered significant. Results Senior radiologists required significantly less FT (senior = 0.43 s, junior = 0.53 s, P = 0.041), but there was no significant difference in DAPs (senior = 56.3 µGy*m², junior = 60.6 µGy*m², P = 0.151). PICC implantations through the left side resulted in a significant reduction of the median FT by 60.9% (left = 0.45 s, right = 1.15 s, P = 0.010). Conclusion Due to considerable dose reduction, the left-sided puncture, especially via the basilic and brachial veins, performed by well-trained interventional radiologists seem to be the preferable approach for PICCs.

“Extended subcutaneous route” technique: a quick subcutaneous tunnelling technique for PICC insertion

Purpose

To describe a quick tunnelling technique for peripherally inserted central catheter (PICC) insertion called the “extended subcutaneous route” technique.

Methods

The “extended subcutaneous route” technique is described step by step.

Results

In 18 consecutive PICCs, inserted with extended route technique in ASST Monza, no complications during insertion were registered. In 969 catheter days observed, we identified only one accidental dislodgement. No other mid-term complications were observed.

Conclusions

Extended subcutaneous route technique allows the creation of a subcutaneous tunnel <5 cm, without skin incision and additional manipulation. Extended subcutaneous route technique may be feasible and useful, particularly for patients with high risk of bleeding or infection.

Computed tomography and magnetic resonance imaging contrast media injectors: technical feature review - what is really needed?

There has been little technical innovation over the last few years for contrast media (CM) injectors that are used for diagnostic imaging (computed tomography [CT], magnetic resonance imaging [MRI], and hybrid imaging systems, such as positron emission tomography–CT or magnetic resonance–positron emission tomography) examinations. The medical need of CM for the enhancement of diagnostic images has been around for a long time, but the application of the CM into the blood stream comes with potential medical complications for the patient and requires a lot of operator experience and training. Most power injector systems that are currently used can do significantly more than what is typically required; this complexity however, adds error potential and cost. This paper focuses on the main features that CM injector systems should have and highlights the technical developments that are useful to have but which add complexity and cost, increase setup time, and require intensive training for safe use. CM injection protocols are very different between CT and MRI, with CT requiring many more variances, has a need for multiphase protocols, and requires a higher timing accuracy. A CM injector used in the MRI suite, on the other-hand, could only need a relatively time insensitive injection with a standard injection flow rate and a volume that is dependent on the patients’ weight. This would make easy and lightweight systems possible, which are able to safely and accurately perform the injection task, while allowing full MRI compatibility with relatively low cost investment and consumable costs.