Computed Tomography Imaging in Patients with Congenital Heart Disease, Part 2: Technical Recommendations. An Expert Consensus Document of the Society of Cardiovascular Computed Tomography (SCCT): Endorsed by the Society of Pediatric Radiology (SPR) and the North American Society of Cardiac Imaging (NASCI)

Abstract

This is the second of two complementary documents commissioned by the SCCT to provide recommendations on the use and optimal performance of cardiac computed tomography (CT) in patients of all ages with congenital heart disease (CHD). The aim of the first document was to describe the current uses of cardiac CT in CHD, review the risks and limitations of current CT technology, provide lesion specific indications for appropriately selected patients, and outline a consensus opinion on the essential skills and knowledge needed to perform cardiac CT in patients with CHD.1Society of Cardiovascular Computed Tomography (SCCT) Computed Tomography Imaging in Patients with Congenital Heart Disease, Part I: Rationale and Utility. An Expert Consensus Document of the Society of Cardiovascular Computed Tomography (SCCT).2015Google Scholar An extensive literature review is included in the part 1 document. The aim of this second document is to provide recommendations on patient preparation and technical scan acquisition for the most commonly referred CHD lesions, and to provide a brief description of radiation dose reduction techniques specific to CT in CHD. The clinical use of cardiac CT in CHD is evolving rapidly and this document is based on the authors' experience, supported by literature when available. The population of adults with congenital heart disease is rapidly increasing as a result of improved outcomes of medical, surgical and catheter-based treatment strategies.2Warnes C.A. Williams R.G. Bashore T.M. et al.ACC/AHA 2008 guidelines for the management of adults with congenital heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to Develop Guidelines on the Management of Adults With Congenital Heart Disease). Developed in Collaboration With the American Society of Echocardiography, Heart Rhythm Society, International Society for Adult Congenital Heart Disease, Society for Cardiovascular Angiography and Interventions, and Society of Thoracic Surgeons.J Am Coll Cardiol. 2008; 52: e143-263Abstract Full Text Full Text PDF PubMed Scopus (540) Google Scholar, 3Khairy P. Van Hare G.F. Balaji S. et al.PACES/HRS Expert Consensus Statement on the Recognition and Management of Arrhythmias in Adult Congenital Heart Disease: Executive Summary.Heart Rhythm. 2014; 11: e81-e101Abstract Full Text Full Text PDF Scopus (25) Google Scholar, 4Bhatt A.B. Foster E. Kuehl K. et al.Congenital heart disease in the older adult: a scientific statement from the american heart association.Circulation. 2015; 131: 1884-1931Crossref PubMed Scopus (138) Google Scholar As patients live longer, there is a greater need for coronary imaging in addition to anatomic imaging, increased use of electrophysiology devices that are MRI unsafe, and higher prevalence of metallic implants that adversely affect MRI image quality. For these patients, CT is increasingly the preferred imaging modality when echocardiography is insufficient to answer the clinical question. This consensus document assumes competence in cardiac CT imaging, and will focus on tailoring the exam for the most commonly referred CHD lesions. The goal of this document is to provide guidance regarding:•Individualized patient preparation.•Acquisition protocols for the most commonly referred CHD lesions.•Brief overview of radiation dose reduction techniques. Patients with CHD have a large variety of anatomic variations. Most patients will come to the CT scanner with a known cardiac diagnosis based on prior imaging studies.5Dillman J.R. Hernandez R.J. Role of CT in the evaluation of congenital cardiovascular disease in children.AJR Am J Roentgenol. 2009; 192: 1219-1231Crossref PubMed Scopus (72) Google Scholar, 6Siegel M.J. Cardiac CTA: congenital heart disease.Pediatr Radiol. 2008; 38: S200-S204Crossref PubMed Scopus (8) Google Scholar, 7Achenbach S. Barkhausen J. Beer M. et al.Consensus recommendations of the German Radiology Society (DRG), the German Cardiac Society (DGK) and the German Society for Pediatric Cardiology (DGPK) on the use of cardiac imaging with computed tomography and magnetic resonance imaging.Rofo. 2012; 184: 345-368Crossref PubMed Scopus (73) Google Scholar, 8Nicol E.D. Gatzoulis M. Padley S.P. Rubens M. Assessment of adult congenital heart disease with multi-detector computed tomography: beyond coronary lumenography.Clin Radiol. 2007; 62: 518-527Abstract Full Text Full Text PDF PubMed Scopus (35) Google Scholar The cardiac CT scan is usually ordered to answer a specific clinical question to help with the medical or interventional management of the patient. Each cardiac CT exam must be tailored to the patient to minimize risk and maximize diagnostic yield. Performing cardiac CT for CHD requires an in depth knowledge of the patient history, prior intervention(s), common hemodynamic sequelae, and the clinical question(s) to be answered by the study. The scan range, acquisition parameters, desired image quality, and the degree of radiation dose reduction will vary greatly depending on the patient and clinical indication. For instance, optimal imaging of the coronary arteries requires a breath hold, slow and regular heart rate, and the highest temporal and spatial resolution available on the scanner platform. For many indications in CHD, this level of image quality, spatial resolution, and/or temporal resolution is not required and aggressive radiation dose reduction techniques may be used.9Han B.K. Lindberg J. Grant K. Schwartz R.S. Lesser J.R. Accuracy and safety of high pitch computed tomography imaging in young children with complex congenital heart disease.Am J Cardiol. 2011; 107: 1541-1546Abstract Full Text Full Text PDF PubMed Scopus (55) Google Scholar, 10Huang M.P. Liang C.H. Zhao Z.J. et al.Evaluation of image quality and radiation dose at prospective ECG-triggered axial 256-slice multi-detector CT in infants with congenital heart disease.Pediatr Radiol. 2011; 41: 858-866Crossref PubMed Scopus (52) Google Scholar, 11Ben Saad M. Rohnean A. Sigal-Cinqualbre A. Adler G. Paul J.F. Evaluation of image quality and radiation dose of thoracic and coronary dual-source CT in 110 infants with congenital heart disease.Pediatr Radiol. 2009; 39: 668-676Crossref PubMed Scopus (101) Google Scholar, 12Al-Mousily F. Shifrin R.Y. Fricker F.J. Feranec N. Quinn N.S. Chandran A. Use of 320-detector computed tomographic angiography for infants and young children with congenital heart disease.Pediatr Cardiol. 2011; 32: 426-432Crossref PubMed Scopus (50) Google Scholar The principles below describe a general approach to the performance of cardiac CT in patients with CHD. The imaging physician needs to be actively involved in directing patient preparation and image acquisition for each cardiac CT performed for CHD. The interpretation and reporting of scans in patients with CHD is time-consuming and requires dedicated time and effort. Expertise in CHD CT imaging combines the skill sets and knowledge base of both cardiology and radiology. This Writing Group strongly advocates a collaborative approach to CHD CT imaging that includes pediatric and adult cardiologists, cardiac imagers and surgeons. Several questions should be asked prior to selection of CT as the imaging test of choice in CHD:1.Does the study indication justify the risks of CT (radiation and contrast exposure, anesthesia and/or medication for heart rate control when needed)?2.Does cardiac CT have the ability to best answer the clinical questions at the least risk to the patient when compared to alternate diagnostic modalities locally available?3.Will the results provide the information necessary to impact clinical management of the patient? The optimal CT imaging environment and core knowledge considered essential for high quality cardiac CTA in CHD is present in Table 1A, Table 1BB .1Society of Cardiovascular Computed Tomography (SCCT) Computed Tomography Imaging in Patients with Congenital Heart Disease, Part I: Rationale and Utility. An Expert Consensus Document of the Society of Cardiovascular Computed Tomography (SCCT).2015Google Scholar Situations where CT may be appropriate in patients with CHD is outlined in Table 1C.1Table 1AOptimal imaging environment for CHD imaging with cardiovascular CT.Alternate cardiac imaging modalities are available so that the test with the least risk can be performed for a specific clinical indicationClose collaboration & communication is present among surgeons, clinical cardiologists and imagersAll patient clinical information is accessible to allow understanding of the clinical indication and potential management options for the patientScan protocols can be designed and adjusted to extract maximum clinical information at minimum procedural riskTechnologists are experienced in cardiac CT and comfortable with varied cardiac scan modesEasy access to pacemaker programming to allow rate and mode adjustment when neededNursing support to facilitate administration of medication for heart rate control when necessary in patients with and without permanent pacemakers, and to provide appropriate monitoring for any side effectsAccess to all forms of prior imaging reports (echocardiography, angiography, nuclear, CMR) so that a targeted evaluation may be performed for an individual patientPost processing workstations capable of handling large multiphase data sets for advanced reconstructionsHigh-speed network to transfer large volume data sets from scanner to workstationImmediate availability of resuscitation equipment and resuscitation team appropriate for the size and age of the patient Open table in a new tab Table 1BRelevant knowledge for the performance of cardiovascular CT in CHD patients.Cardiac/CHD specific knowledge requiredAnatomy & physiology of CHD – natural and repairedSurgical procedures used to palliate or repair CHDCatheter interventions used to palliate or repair CHDMaterial composition of the surgical materials or catheter devices used and the artifact produced with different imaging modalities (MRI and CT)Common residual hemodynamic lesions following initial CHD repairIndications for re-intervention (ACC/AHA/ESC/CCS guidelines)Normal coronary anatomyCongenital coronary anomalies and the indications for and methods of repairBasic EKG knowledge and arrhythmia recognition (and impact on imaging strategy)Pediatric and adult doses for heart rate lowering medications and sublingual nitroglycerin, and contraindications to these medicationsCT technique-specific knowledge requiredTraining and experience in congenital cardiac CT (there are no current educational standards for CHD CT)Scanning principles and scan modesContrast injection protocols adjusted for both patient size and cardiac pathologyProphylaxis against and treatment of minor and major contrast reactionsRadiation physics and basics of radiation dose measurementRadiation dose reduction strategies and individualized scan planningFamiliarity and competence with post-processing methods and softwareFamiliarity with standards for quantification and reporting in CHD Open table in a new tab Table 1CSituations in which cardiovascular CT may be considered in CHD.Presence of CMR incompatible implant or foreign body (retained pacing leads, non-MR compatible pacemaker/defibrillator, neurostimulator)Poor CMR image quality (known or expected) due to metallic artifactUnable to fit in MRI scanner due to obesity; or severe claustrophobiaNeonate or young patient requiring evaluation of complex anatomy, particularly if considered higher risk for adverse event with anesthesia required for CMR, and the CT scan can be performed with no or limited sedationCritically ill patient of any age that may not tolerate breath holding or length of CMR scanEvaluation of ventricular assist device or ECMO cannula positioningPatient requiring CT for evaluation of extra-cardiac anatomy in addition to CHD (e.g. lung parenchyma, airway, skeletal abnormality)Pre-operative patients with prior sternotomy considered high risk for vascular injury with sternal reentry due to an anterior coronary artery, conduit, or sternal adhesionsEvaluation of prosthetic valve function or structural integrity (calcification, stenosis, coaptation defect, leaflet immobility, paravalvular leak)Evaluation of calcification within vessels and surgical conduits prior to catheter-based intervention (e.g. balloon angioplasty, transcatheter valve replacement, stent placement)Coronary artery imaging in CHD:•Patient needing detailed pre-operative coronary artery evaluation in addition to assessment of complex anatomy•Patient with symptoms and signs suggestive of atherosclerotic coronary artery disease and a history of CHD, prior coronary intervention, or high risk Kawasaki disease• Young symptomatic patients with known or suspected coronary anomaly, particularly if CMR is unlikely to provide complete assessment or more likely to require anesthesia•Delineation of coronary anatomy prior to percutaneous pulmonary valve implantation•Evaluation of coronary artery after any surgery requiring reimplantation Open table in a new tab Non-invasive CT imaging of the coronary arteries (CCTA), complex CHD and valvular function requires isotropic data sets with high temporal and spatial resolution. Newer scanner technologies allow for imaging of the heart and coronary arteries in one or several heart beats, with significantly improved diagnostic performance over older CT technology. The major advantages of newer technology scanners for CCTA are a reduction in nondiagnostic scans or non-evaluable coronary segments and a substantial improvement in per-patient specificity and positive predictive value. There is also decreased systolic motion artifact of the proximal great vessels on newer generation technology that captures an image in a fraction of, or specific portion of, the cardiac cycle. For many non-coronary indications, older generation scanners are adequate for image acquisition. Non-invasive CT imaging of mediastinal vessels can be performed using 16 detector technology, although image quality will be improved using scanners with 64 detectors or greater. Older generation scanners acquire data during a larger portion of the cardiac cycle, or during both systole and diastole in a non ECG gated scan. In this case, systolic motion artifact may obscure the proximal ascending aorta in particular and can be misinterpreted as a Type A aortic dissection. The need for sedation or anesthesia may be increased in older generation MDCT scanners that acquire data over several seconds since there is increased potential for artifact from both breathing and patient motion. Newer generation MDCT scanners also offer the advantage of submillimeter isotropic data sets, which improves image quality even without ECG gating. Important information about conduits, coronary arteries, baffles, thoracic arterial and venous vasculature anatomy can be assessed. The higher spatial and temporal resolution combined with rapid image acquisition will improve image quality based on both technical and patient factors in young patients. CT Technologists performing cardiac CT in CHD should have expertise in cardiac CT, including knowledge of ECG gating techniques, contrast injection and image acquisition protocols specific to CHD. Technologists must also have expertise in patient and indication specific radiation dose reduction techniques. For detailed coronary imaging in patients of all ages, breath holding is usually required during image acquisition to eliminate respiratory motion. For other anatomic imaging, the need for a breath hold is dependent on the acquisition time of the scan, the size of the structure to be visualized, and the image quality required. For newer generation scanners the time of image acquisition is less than a second or a single heartbeat. Techniques such as half-scan reconstruction, prospectively ECG triggered high pitch scan mode or volumetric target mode reduce both respiratory and cardiac motion. With this technology cardiac anatomy and proximal coronary course can be visualized without a breath hold.13Han B.K. Overman D.M. Grant K. et al.Non-sedated, free breathing cardiac CT for evaluation of complex congenital heart disease in neonates.J Cardiovasc Comput Tomogr. 2013; 7: 354-360Abstract Full Text Full Text PDF PubMed Scopus (40) Google Scholar, 14Lell M.M. May M. Deak P. et al.High-pitch spiral computed tomography: effect on image quality and radiation dose in pediatric chest computed tomography.Invest Radiol. 2011; 46: 116-123Crossref PubMed Scopus (137) Google Scholar, 15Crean A. Cardiovascular MR and CT in congenital heart disease.Heart. 2007; 93: 1637-1647Crossref PubMed Scopus (41) Google Scholar, 16Jadhav S.P. Golriz F. Atweh L.A. Zhang W. Krishnamurthy R. CT angiography of neonates and infants: comparison of radiation dose and image quality of target mode prospectively ECG-gated 320-MDCT and ungated helical 64-MDCT.AJR Am J Roentgenol. 2015; 204: W184-W191Crossref PubMed Scopus (39) Google Scholar For older generation scanners with images acquired over several seconds or multiple heart beats, breath holding may be required to reduce motion artifact, particularly when trying to image small cardiac structures. •Anatomy only (non-coronary):○Most infants can be swaddled and imaged without sedation. Use of oral 25% dextrose solution and a pacifier may help calm a baby when upset.○Patients 6 months to 3 years of age often require sedation to lie still in the scanner, but can usually be imaged free-breathing. Video distraction or immobilization devices are available for this age patient.○Most patients 4 years of age or older who are developmentally appropriate for age can cooperate with holding still in the scanner without sedation. The presence of a parent in the room or child-life services may be helpful.○Most patients 7 years of age or older who are developmentally appropriate for age can cooperate with a breath hold.○Use of scanners with volumetric acquisition or ultra-high pitch scanning modes should decrease the need for sedation in children of all ages due to the short acquisition time.•Coronary artery or functional imaging:○When only proximal coronary artery definition is requested to assist in surgical planning: There is relatively little systolic motion of the proximal coronary arteries, even at higher heart rates. As a result, diagnostic imaging of the proximal coronary arteries may be possible without sedation or breath hold if using prospectively ECG triggered high pitch or volumetric target scan mode.11Ben Saad M. Rohnean A. Sigal-Cinqualbre A. Adler G. Paul J.F. Evaluation of image quality and radiation dose of thoracic and coronary dual-source CT in 110 infants with congenital heart disease.Pediatr Radiol. 2009; 39: 668-676Crossref PubMed Scopus (101) Google Scholar, 17Vastel-Amzallag C. Le Bret E. Paul J.F. et al.Diagnostic accuracy of dual-source multislice computed tomographic analysis for the preoperative detection of coronary artery anomalies in 100 patients with tetralogy of Fallot.J Thorac Cardiovasc Surg. 2011; 142: 120-126Abstract Full Text Full Text PDF PubMed Scopus (33) Google Scholar○For these patients, the sedation requirements are similar to non-coronary applications above.○When detailed coronary artery imaging or ventricular function is requested (including detailed ostial anatomy): Most scan sequences used for detailed coronary artery imaging at fast heart rates and functional imaging acquire data over several heart beats. Patients younger than 5–6 years of age will need general anesthesia for cooperation with breath holding when high resolution or detailed coronary anatomy or functional imaging is needed (generally one breath hold). For those able to cooperate, practicing the breath hold with the patient prior to imaging is often helpful to both assure cooperation and to assess the respiratory variability of the heart rate. A peripheral IV line is most commonly used for contrast injection for congenital cardiac CT scans, and is the preferred form of access for power injection with automated devices. PICC lines, central lines, and indwelling venous catheters have all been described for safe injection as well, although hand injection is commonly used with these access types. Umbilical catheters can be safely used but may result in suboptimal contrast enhancement due to reflux of contrast into the liver. Due to the high incidence of intra-cardiac shunting in patients with complex congenital heart disease, particular care to avoid any air bubbles in the injection is important, as it may result in a systemic arterial embolus. In general, the largest gauge IV cannula feasible for the patient body size is optimal for contrast injection. Most practitioners use a direct connection between the power injector and the hub of the peripheral IV. The IV gauge should be determined based on the maximum anticipated flow rate of contrast injection. Warming the contrast will decrease viscosity and allows for safer injection if the rate is at the higher limits of the catheter.18Davenport M.S. Wang C.L. Bashir M.R. Neville A.M. Paulson E.K. Rate of contrast material extravasations and allergic-like reactions: effect of extrinsic warming of low-osmolality iodinated CT contrast material to 37 degrees C.Radiology. 2012; 262: 475-484Crossref PubMed Scopus (40) Google Scholar Both the IV gauge and the IV site should be considered when determining flow rates. Slower rates may be preferred for small venous structures such as the hand or foot in a baby or small child. The following are general guidelines for flow rates and pounds per square inch (psi) based on IV gauge:24 gauge: 0.5–1.5 ml/s, maximum 50–100 psi22 gauge: 2–3.5 ml/s, maximum 100–300 psi20 gauge: 3–5 ml/s, maximum 300 psi18 gauge: 4–6.5 ml/s, maximum 300 psi The location for contrast injection should be determined in advance so that IV placement is appropriate for the study indication. The optimal location of a peripheral IV may vary by cardiac lesion. An upper extremity antecubital IV cannula is most commonly used and is generally preferred for most indications. Injections performed via the right upper extremity, rather than the left, may help minimize streak artifact in the arch vessels due to residual high density contrast in the left brachiocephalic vein. Injection via a lower extremity vein may be considered in neonates and infants to avoid residual high-density contrast in the SVC, particularly when pathology or anomalous drainage of the right pulmonary veins is suspected. For patients with anomalous systemic venous drainage such as an interrupted IVC, bilateral SVC, or suspected central venous occlusion, IV placement may need to be in a certain location to optimize opacification of the structure of interest. For example, if an interrupted IVC is suspected, contrast injection in the lower extremity will guarantee that the structure is opacified, rather than relying on venous recirculation. If a venous thrombotic occlusion is suspected, injection may result in cardiac opacification via collateral vessels, making timing of image acquisition difficult. Additionally, contrast swirling with unopacified blood during image acquisition can be difficult to differentiate from thrombus or venous occlusion (e.g. imaging a Fontan circuit). Beam hardening artifact may interfere with the assessment of a vessel or surrounding structures. When these possibilities are present, it may be best to visualize the structure during venous recirculation. At the low contrast injection rates used in the smallest patients, contrast arrival in the heart will vary based on IV location and transit time. This needs to be accounted for in scan monitoring and timing of image acquisition to avoid imaging too early or late for the contrast bolus. Power injectors can be safely used in pediatric patients with any IV ≥ 24 gauge, depending on patient size.19Amaral J.G. Traubici J. BenDavid G. Reintamm G. Daneman A. Safety of power injector use in children as measured by incidence of extravasation.AJR Am J Roentgenol. 2006; 187: 580-583Crossref PubMed Scopus (40) Google Scholar Standard power injection is performed with the power injector set at 50–300 psi. The rate of injection and psi should be adjusted for the IV gauge. A 22 gauge IV or larger is preferred, but safe injection through a 24 gauge has been reported for neonates at low flow rates of 0.5–1.5 ml/s.19Amaral J.G. Traubici J. BenDavid G. Reintamm G. Daneman A. Safety of power injector use in children as measured by incidence of extravasation.AJR Am J Roentgenol. 2006; 187: 580-583Crossref PubMed Scopus (40) Google Scholar When using a power injector through a small gauge IV, a saline test injection with careful observation of the injection site and psi should be used prior to contrast injection to evaluate the integrity of both the injector connection to the IV and the IV itself. The psi achieved for a contrast injection will be higher than that for an equivalent amount of saline through the same IV. Power injection through central lines not specifically designed for power injection is not recommended by the FDA or central line manufacturers. Power injection through central lines can be safely performed if pressure-limited injection is employed.20Rigsby C.K. Gasber E. Seshadri R. Sullivan C. Wyers M. Ben-Ami T. Safety and efficacy of pressure-limited power injection of iodinated contrast medium through central lines in children.AJR Am J Roentgenol. 2007; 188: 726-732Crossref PubMed Scopus (45) Google Scholar The package insert regarding maximum allowed psi should be verified for each central line prior to use. If this information is not available, a hand injection should be considered. For pressure-limited injection, both the injection rate and maximum psi allowed for the catheter are set, and the injector will inject contrast at the allowed pressure to avoid catheter rupture. For the same set psi, the contrast injection rate will vary significantly based on catheter length and size, and may not allow for adequate injection rates except in neonates and young children.20Rigsby C.K. Gasber E. Seshadri R. Sullivan C. Wyers M. Ben-Ami T. Safety and efficacy of pressure-limited power injection of iodinated contrast medium through central lines in children.AJR Am J Roentgenol. 2007; 188: 726-732Crossref PubMed Scopus (45) Google Scholar, 21Plumb A.A. Murphy G. The use of central venous catheters for intravenous contrast injection for CT examinations.Br J Radiol. 2011; 84: 197-203Crossref PubMed Scopus (31) Google Scholar A pressure-limited injection to a maximum of 25 psi has been used safely in small central catheters with acceptable opacification in patients less than 30 kg. Many power injectors have a lower pressure limit of 50 psi, which is higher than recommended for most small gauge indwelling pediatric catheters.20Rigsby C.K. Gasber E. Seshadri R. Sullivan C. Wyers M. Ben-Ami T. Safety and efficacy of pressure-limited power injection of iodinated contrast medium through central lines in children.AJR Am J Roentgenol. 2007; 188: 726-732Crossref PubMed Scopus (45) Google Scholar The small bore of some catheters (3 Fr or less) may not allow for pressure limited injection. If hospital policy or clinical judgment prohibits power injection through 24g IV catheters or a central line, hand injection of contrast can be used. The total contrast volume used for pediatric CT angiography is typically 1–2 ml/kg until standard adult contrast volumes are achieved. The combined volume load of the contrast and saline flush is 2–3 ml/kg and is usually tolerated without hemodynamic consequence. The minimum time between scan initiation and image acquisition can be as long as 4 s with certain scan protocols. Mixing contrast and saline to lengthen the injection time increases the chance of optimal enhancement at the time of image acquisition for scans with very short image acquisition times, longer scan delays, or variable contrast transit times. A longer contrast injection may result in high density contrast in the venous inflow when the data is acquired, creating streak artifact that affects adjacent structures. If streak artifact is likely to affect the diagnostic quality of a scan, later image acquisition, a tighter contrast bolus with a saline flush, or an additional scan during venous recirculation may be considered if systemic venous anatomy is needed. The following are examples of common injection protocols. A Biphasic/dual phase injection protocol (contrast at a constant rate followed by a saline flush) is typically used to for pulmonary or systemic arterial angiography, with image acquisition timed to opacification of the vessel of interest. For patients with intra-cardiac mixing, a longer and slower contrast injection with image acquisition at the end of injection often allows venous and arterial opacification on the same scan without a separate initial bolus. This can be helpful in patients such as neonates with intra-cardiac mixing or a suspected combination of arterial and venous anomalies. An example is given for a normal sized adult, rates are adjusted to patient size (Table 2).Table 2Example biphasic/dual phase injection protocol (contrast + saline).Injection rate (ml/s)Volume (ml)Time of injection (s)Contrast6 ml/s100 ml17 sSaline4 ml/s50 ml12.5 s Open table in a new tab A biventricular injection protocol (also called a triphasic procotol: two phase contrast injection followed by a saline flush) is most commonly used for simultaneous pulmonary and aortic angiography. This method is useful in patients with tetralogy of Fallot or after the arter