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Cardiovascular MR Imaging in Neonates and Infants with Congenital Heart Disease¹

¹ From the Department of Diagnostic Imaging (C.J.K.) and the Division of Paediatric Cardiology (E.R.V.B.), University Children’s Hospital, Stein-wiesstrasse 75, CH 8032 Zürich, Switzerland; and the Department of Diagnostic Imaging, Hospital for Sick Children, Toronto, Ontario, Canada (S.-J.Y.). Presented as an education exhibit at the 2005 RSNA Annual Meeting. Received March 16, 2006; revision requested May 22 and received July 14; accepted July 20. All authors have no financial relationships to disclose. Address correspondence to C.J.K. (e-mail: christian.kellenberger{at}kispi.unizh.ch).

	Abstract

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Imaging Technique Common Clinical Indications Conclusions References

 
Cardiovascular magnetic resonance (MR) imaging has become an important alternative to echocardiography and angiocardiography in the evaluation of patients with congenital heart disease (CHD). It is increasingly being used in neonates and infants for the initial investigation of CHD or as follow-up after surgery or catheter-guided intervention. Specific indications for cardiovascular MR imaging in neonates and infants include investigation of the thoracic vasculature, quantification of the ventricular volumes, and evaluation of primary cardiac tumors. To obtain good-quality MR images in neonates and infants, it is essential to adjust the technical parameters of the pulse sequences to the small size and fast heart rates of the patients. Various MR imaging techniques are available that are effective in demonstrating the complex morphologic features of the cardiovascular system and that provide additional functional and hemodynamic information. The information provided by cardiovascular MR imaging is useful for treatment planning and, in many cases, may obviate potentially harmful cardiac catheterization.

© RSNA, 2007

	LEARNING OBJECTIVES FOR TEST 1

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Imaging Technique Common Clinical Indications Conclusions References

 
After reading this article and taking the test, the reader will be able to:

• Discuss the challenges of cardiovascular MR imaging in neonates and infants.
  
• Describe the application of cardiovascular MR imaging techniques in neonates and infants.
  
• List the most common indications for cardiovascular MR imaging in these patients.
  

	Introduction

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Imaging Technique Common Clinical Indications Conclusions References

 
In neonates and infants with congenital heart disease (CHD), repeat imaging is required for delineation of the cardiac and vascular anatomy, for planning therapy, and as follow-up after interventions. In cases in which echocardiography does not provide sufficient information, cardiovascular magnetic resonance (MR) imaging is an established, less invasive alternative to angiocardiography that does not involve catheterization or ionizing radiation (1).

In this article, we discuss and illustrate the MR imaging techniques (including contrast material–enhanced MR angiography, cine imaging, and phase-contrast velocity mapping) and the technical adjustments necessary for imaging small babies with high heart rates. In addition, we discuss common indications for cardiovascular MR imaging in this patient population, including abnormalities of the aorta and pulmonary vasculature, complex CHD, borderline hypoplastic left heart syndrome, and tumors.

	Imaging Technique

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Imaging Technique Common Clinical Indications Conclusions References

 
Cardiovascular MR Imaging Sequences
With the advent of strong and fast gradient systems, various pulse sequences have become widely available that allow detailed anatomic and functional assessment of CHD (2–4). The following discussion is based on our experience using a 1.5-T Signa MR/i Twinspeed scanner (GE Medical Systems, Milwaukee, Wisc).

Every cardiovascular MR imaging study is started with the acquisition of coronal, axial, and sagittal nongated steady-state free precession images covering the entire chest for a quick overview of the situs and the cardiac and vascular anatomy. These bright-blood steady-state free precession images serve as localizers for subsequent imaging.

Cine imaging with electrocardiographically gated steady-state free precession or fast gradient-echo sequences provides bright-blood multiphase images that show cardiac or valvular motion in multiple frames over the entire cardiac cycle. For assessing cardiac function and measuring the ventricular volumes, short-axis cine images of the heart are obtained from the base to the apex. For a detailed study of the cardiac and valvular anatomy and function, cine imaging can be performed in any desired plane (eg, the vertical or horizontal long-axis plane or along the ventricular outflow tracts).

Velocity-encoded phase-contrast cine sequences allow measurement of blood flow velocity and volume. Differential blood flow to the lungs is assessed by measuring the flow in the right and left pulmonary arteries (4,5). Intra- or extracardiac shunts are quantified with the systemic-to-pulmonary flow ratio (Q_P/Q_S), which is calculated from flow measurements obtained in the pulmonary trunk and the ascending aorta. The pressure gradient (P) over a stenosis can be estimated by measuring the maximum poststenotic velocity (V_max) and using the simplified Bernoulli equation P = 4(V_max)².

Contrast-enhanced MR angiography is performed for a detailed study of the entire thoracic vasculature. Three-dimensional (3D) imaging data are acquired in continuous partitions with a 3D fast spoiled gradient-echo sequence after the intravenous administration of gadolinium-based contrast material. From the 3D data set, it is possible to display and measure the dimensions of a specific vessel in any oblique plane with subvolume maximum-intensity-projection (MIP) reformatted images. For illustration purposes, 3D volume-rendered (VR) MR angiographic images allow excellent visualization of the often complex vascular anatomy in patients with CHD.

Cardiac-gated spin-echo and fast spin-echo sequences are performed with T1 or T2 weighting prior to the intravenous administration of gadolinium-based contrast material and again with T1 weighting following contrast material administration to evaluate the extension and tissue characteristics of a tumor. Spin-echo or fast spin-echo sequences are also useful for delineating the anatomy of the airways.

Technical Considerations in Neonates and Infants
Neonates and infants need to be immobilized for an MR imaging study. We prefer anesthesia with intubation to sedation so that breath-hold sequences, which yield better-quality images, can be performed. To minimize the time of anesthesia, each study is tailored from the aforementioned sequences, so that the referral questions can be answered. In a simple case in which only the thoracic vasculature needs to be delineated, the study can be completed in less than 10 minutes. In a more complex case that also involves cine imaging in several planes and measurements of flow in multiple vessels, the average imaging time is 45 minutes. Because neonates are at risk for hypothermia during an MR imaging study, we place commercially available hotpacks (Tempress; Flawa AG, Flawil, Switzerland) that have been preheated to body temperature around the head, pelvis, and legs of the patient and cover him or her with a blanket. A constant body temperature is ensured by monitoring the skin temperature with a sensor and measuring the ear temperature before and after imaging.

The small size of the vessels and heart in a baby requires a high spatial resolution (in-plane resolution 1 mm²), which is achieved by using a relatively small (20–26-cm) field of view, a sufficiently large matrix, and thin sections. Spin-echo and cine imaging is performed with a section thickness of 3–5 mm. For accurate measurements of the ventricular volumes in small neonates, we prefer fast gradient-echo imaging to steady-state free precession cine imaging because it allows thinner sections. The 3D MR angiography is performed with a section thickness of 1.2–2.4 mm, a field of view of 220 mm, and a matrix of 256 x 160, resulting in a voxel size of 0.9 x 1.1 x 1.2–2.4 mm³ (reconstructed to 0.45 x 0.55 x 0.6–1.2 mm³ with zero interpolation).

To receive sufficient signal from such small voxels, it is necessary to use the smallest available coil that covers the entire chest of the baby and provides the highest signal-to-noise ratio. We achieve good results with a receive-transmit head coil, but a knee coil or a small phased-array surface coil can be used with other imagers. The best choice would be a multielement phased-array coil that fits the body of an infant and would allow parallel imaging for improving spatial resolution or shortening imaging time.

For MR angiography, we use a double or triple dose of gadolinium-based contrast material (0.2–0.3 mmol/kg body weight). Because of the small volumes of contrast material, we usually inject it manually through any available peripheral intravenous line. The contrast bolus is injected over 8–10 seconds, followed by an equivalent volume of saline solution. Exact timing of the MR angiographic image acquisition is crucial for obtaining images with a high signal-to-noise ratio. In our experience, the best results are achieved with an automated bolus detection method such as MR Smartprep (GE Medical Systems) (6) or MR fluoroscopic triggering (7) combined with elliptic-centric k-space filling. If no real-time triggering method is available, imaging can be performed with sequential k-space filling and started together with the contrast material injection. To ensure that all vessels including the systemic veins are enhanced, imaging is repeated twice. The need for bolus timing can be eliminated by using "time-resolved" MR angiography, which consists of a series of consecutive short 3D volume acquisitions (dynamics) (8). With parallel imaging or advanced k-space filling schemes, it has become possible to obtain one dynamic in less than 3–5 seconds. However, with current time-resolved MR angiographic techniques, improved temporal resolution is achieved only at the cost of a lower true spatial resolution (approximately 1.5 x 1.5 x 2–3 mm³) than is achievable with traditional MR angiographic techniques with a 10–20-second imaging time.

The fast heart rates in neonates and infants (100–150 bpm) require a high temporal resolution (20–60 msec) for accurate ventricular volume or flow measurements. If a segmented k-space technique is used, the number of lines or views per segment must be adjusted to the heart rate to achieve sufficient temporal resolution.

Table 1 shows typical selected technical parameters for a cardiovascular MR imaging study in neonates and infants at our institutions.

	Common Clinical Indications

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Imaging Technique Common Clinical Indications Conclusions References

In patients with abnormalities of the aorta, including interrupted aortic arch (Fig 1), coarctation (Figs 2, 3), and vascular rings, MR angiography can clearly depict the anatomy and size of the aortic arch, the branching pattern of the great arteries, and the patency of the ductus arteriosus (10,11).

View larger version (81K): [in this window] [in a new window] [Download PPT slide]   Figure 1a.  Interrupted aortic arch in a 3-day-old girl with transposition of the great arteries, ventricular septum defects (VSDs), and an atrial septum defect (ASD). Severe aortic coarctation and a hypoplastic right ventricle were suspected at echocardiography. (a) VR MR angiographic image demonstrates a type A interrupted aortic arch. Transposition of the great arteries, with the aorta (AO) arising from the right ventricle (RV) and the pulmonary trunk (MPA) from the left ventricle (LV), is clearly depicted. PDA = patent ductus arteriosus. (b) Horizontal long-axis cine image shows multiple VSDs and the ASD (arrows). LV = left ventricle, RV = right ventricle. (See also Movie 1 at radiographics.rsnajnls.org/cgi/content/full/27/1/5/DC1.) (c) Short-axis cine images with measurement of the end-diastolic volumes show equal-sized ventricles, thereby helping rule out right ventricular hypoplasia. BSA = body surface area, LV = left ventricle (outlined in red), RV = right ventricle (outlined in yellow). On the basis of the MR imaging findings and without further cardiac catheterization, surgical correction of the aortic arch and pulmonary banding were performed on day 4. Biventricular repair with an arterial switch procedure and closure of the VSDs and ASD were performed 3 weeks later.

View larger version (136K): [in this window] [in a new window] [Download PPT slide]   Figure 1b.  Interrupted aortic arch in a 3-day-old girl with transposition of the great arteries, ventricular septum defects (VSDs), and an atrial septum defect (ASD). Severe aortic coarctation and a hypoplastic right ventricle were suspected at echocardiography. (a) VR MR angiographic image demonstrates a type A interrupted aortic arch. Transposition of the great arteries, with the aorta (AO) arising from the right ventricle (RV) and the pulmonary trunk (MPA) from the left ventricle (LV), is clearly depicted. PDA = patent ductus arteriosus. (b) Horizontal long-axis cine image shows multiple VSDs and the ASD (arrows). LV = left ventricle, RV = right ventricle. (See also Movie 1 at radiographics.rsnajnls.org/cgi/content/full/27/1/5/DC1.) (c) Short-axis cine images with measurement of the end-diastolic volumes show equal-sized ventricles, thereby helping rule out right ventricular hypoplasia. BSA = body surface area, LV = left ventricle (outlined in red), RV = right ventricle (outlined in yellow). On the basis of the MR imaging findings and without further cardiac catheterization, surgical correction of the aortic arch and pulmonary banding were performed on day 4. Biventricular repair with an arterial switch procedure and closure of the VSDs and ASD were performed 3 weeks later.

View larger version (59K): [in this window] [in a new window] [Download PPT slide]   Figure 1c.  Interrupted aortic arch in a 3-day-old girl with transposition of the great arteries, ventricular septum defects (VSDs), and an atrial septum defect (ASD). Severe aortic coarctation and a hypoplastic right ventricle were suspected at echocardiography. (a) VR MR angiographic image demonstrates a type A interrupted aortic arch. Transposition of the great arteries, with the aorta (AO) arising from the right ventricle (RV) and the pulmonary trunk (MPA) from the left ventricle (LV), is clearly depicted. PDA = patent ductus arteriosus. (b) Horizontal long-axis cine image shows multiple VSDs and the ASD (arrows). LV = left ventricle, RV = right ventricle. (See also Movie 1 at radiographics.rsnajnls.org/cgi/content/full/27/1/5/DC1.) (c) Short-axis cine images with measurement of the end-diastolic volumes show equal-sized ventricles, thereby helping rule out right ventricular hypoplasia. BSA = body surface area, LV = left ventricle (outlined in red), RV = right ventricle (outlined in yellow). On the basis of the MR imaging findings and without further cardiac catheterization, surgical correction of the aortic arch and pulmonary banding were performed on day 4. Biventricular repair with an arterial switch procedure and closure of the VSDs and ASD were performed 3 weeks later.

View larger version (152K): [in this window] [in a new window] [Download PPT slide]   Figure 2a.  Aortic coarctation in a 6-day-old girl with hypoplastic left heart complex. MR imaging was requested to help decide whether to perform biventricular or univentricular repair. (a, b) Short-axis (a) and horizontal long-axis (b) cine images demonstrate a small left ventricle (LV), a small mitral valve annulus (**), and a muscular inlet VSD (*). LA = left atrium, RA = right atrium, RV = right ventricle. (c) Posterior VR MR angiographic image shows a patent ductus arteriosus, tubular hypoplasia of the aortic arch, and the coarctation (arrow). On the basis of the MR imaging measurements of the left ventricular end-diastolic volume (20 mL/m2 body surface area) and the mitral valve annulus area (2.8 cm2/m2 body surface area), the left ventricle was judged to be large enough for biventricular repair. The patient successfully underwent closure of the VSD and repair of the aortic arch.

View larger version (153K): [in this window] [in a new window] [Download PPT slide]   Figure 2b.  Aortic coarctation in a 6-day-old girl with hypoplastic left heart complex. MR imaging was requested to help decide whether to perform biventricular or univentricular repair. (a, b) Short-axis (a) and horizontal long-axis (b) cine images demonstrate a small left ventricle (LV), a small mitral valve annulus (**), and a muscular inlet VSD (*). LA = left atrium, RA = right atrium, RV = right ventricle. (c) Posterior VR MR angiographic image shows a patent ductus arteriosus, tubular hypoplasia of the aortic arch, and the coarctation (arrow). On the basis of the MR imaging measurements of the left ventricular end-diastolic volume (20 mL/m2 body surface area) and the mitral valve annulus area (2.8 cm2/m2 body surface area), the left ventricle was judged to be large enough for biventricular repair. The patient successfully underwent closure of the VSD and repair of the aortic arch.

View larger version (142K): [in this window] [in a new window] [Download PPT slide]   Figure 2c.  Aortic coarctation in a 6-day-old girl with hypoplastic left heart complex. MR imaging was requested to help decide whether to perform biventricular or univentricular repair. (a, b) Short-axis (a) and horizontal long-axis (b) cine images demonstrate a small left ventricle (LV), a small mitral valve annulus (**), and a muscular inlet VSD (*). LA = left atrium, RA = right atrium, RV = right ventricle. (c) Posterior VR MR angiographic image shows a patent ductus arteriosus, tubular hypoplasia of the aortic arch, and the coarctation (arrow). On the basis of the MR imaging measurements of the left ventricular end-diastolic volume (20 mL/m2 body surface area) and the mitral valve annulus area (2.8 cm2/m2 body surface area), the left ventricle was judged to be large enough for biventricular repair. The patient successfully underwent closure of the VSD and repair of the aortic arch.

View larger version (143K): [in this window] [in a new window] [Download PPT slide]   Figure 3a.  Aortic coarctation in a 3-week-old girl with an atrioventricular septum defect (AVSD). Pulmonary vein anomalies were suspected at echocardiography. (a) Horizontal long-axis cine image shows the AVSD (**). LV = left ventricle, RV = right ventricle. (b–d) Posterior VR (b, c) and anterior subvolume MIP (d) MR angiographic images show a patent ductus arteriosus, a hypoplastic aortic arch, and the coarctation (arrow in b). The pulmonary vein anatomy is clearly defined as a common orifice of the left pulmonary veins—which is also stenotic (arrow in c)—and an anomalous connection of the right upper pulmonary vein (* in c and d) to the superior vena cava. AO = aorta, LPA = left pulmonary artery, RA = right atrium, RPA = right pulmonary artery. On the basis of the MR imaging findings, the coarctation was first repaired, and 3 weeks later, at the time of the AVSD repair, the left pulmonary veins were augmented and the right upper pulmonary vein was reimplanted into the left atrium.

View larger version (165K): [in this window] [in a new window] [Download PPT slide]   Figure 3b.  Aortic coarctation in a 3-week-old girl with an atrioventricular septum defect (AVSD). Pulmonary vein anomalies were suspected at echocardiography. (a) Horizontal long-axis cine image shows the AVSD (**). LV = left ventricle, RV = right ventricle. (b–d) Posterior VR (b, c) and anterior subvolume MIP (d) MR angiographic images show a patent ductus arteriosus, a hypoplastic aortic arch, and the coarctation (arrow in b). The pulmonary vein anatomy is clearly defined as a common orifice of the left pulmonary veins—which is also stenotic (arrow in c)—and an anomalous connection of the right upper pulmonary vein (* in c and d) to the superior vena cava. AO = aorta, LPA = left pulmonary artery, RA = right atrium, RPA = right pulmonary artery. On the basis of the MR imaging findings, the coarctation was first repaired, and 3 weeks later, at the time of the AVSD repair, the left pulmonary veins were augmented and the right upper pulmonary vein was reimplanted into the left atrium.

View larger version (174K): [in this window] [in a new window] [Download PPT slide]   Figure 3c.  Aortic coarctation in a 3-week-old girl with an atrioventricular septum defect (AVSD). Pulmonary vein anomalies were suspected at echocardiography. (a) Horizontal long-axis cine image shows the AVSD (**). LV = left ventricle, RV = right ventricle. (b–d) Posterior VR (b, c) and anterior subvolume MIP (d) MR angiographic images show a patent ductus arteriosus, a hypoplastic aortic arch, and the coarctation (arrow in b). The pulmonary vein anatomy is clearly defined as a common orifice of the left pulmonary veins—which is also stenotic (arrow in c)—and an anomalous connection of the right upper pulmonary vein (* in c and d) to the superior vena cava. AO = aorta, LPA = left pulmonary artery, RA = right atrium, RPA = right pulmonary artery. On the basis of the MR imaging findings, the coarctation was first repaired, and 3 weeks later, at the time of the AVSD repair, the left pulmonary veins were augmented and the right upper pulmonary vein was reimplanted into the left atrium.

View larger version (130K): [in this window] [in a new window] [Download PPT slide]   Figure 3d.  Aortic coarctation in a 3-week-old girl with an atrioventricular septum defect (AVSD). Pulmonary vein anomalies were suspected at echocardiography. (a) Horizontal long-axis cine image shows the AVSD (**). LV = left ventricle, RV = right ventricle. (b–d) Posterior VR (b, c) and anterior subvolume MIP (d) MR angiographic images show a patent ductus arteriosus, a hypoplastic aortic arch, and the coarctation (arrow in b). The pulmonary vein anatomy is clearly defined as a common orifice of the left pulmonary veins—which is also stenotic (arrow in c)—and an anomalous connection of the right upper pulmonary vein (* in c and d) to the superior vena cava. AO = aorta, LPA = left pulmonary artery, RA = right atrium, RPA = right pulmonary artery. On the basis of the MR imaging findings, the coarctation was first repaired, and 3 weeks later, at the time of the AVSD repair, the left pulmonary veins were augmented and the right upper pulmonary vein was reimplanted into the left atrium.

View larger version (111K): [in this window] [in a new window] [Download PPT slide]   Figure 4a.  Pulmonary atresia with intact ventricular septum in a 1-day-old girl. (a) Horizontal long-axis cine image shows a dilated, noncontracting right ventricle (RV) and a dilated right atrium (RA). LA = left atrium, LV = left ventricle. (See also Movie 2 at radiographics.rsnajnls.org/cgi/content/full/27/1/5/DC1.) (b, c) Posterior VR (b) and coronal oblique subvolume MIP (c) MR angiographic images demonstrate that the pulmonary arteries (LPA, RPA) are hypoplastic, confluent, and supplied by a single collateral artery (CA) from the descending aorta (AO). LA = left atrium, * = pulmonary veins. A right ventricle–pulmonary artery conduit was planned, but the patient died before surgery could be performed.

View larger version (147K): [in this window] [in a new window] [Download PPT slide]   Figure 4b.  Pulmonary atresia with intact ventricular septum in a 1-day-old girl. (a) Horizontal long-axis cine image shows a dilated, noncontracting right ventricle (RV) and a dilated right atrium (RA). LA = left atrium, LV = left ventricle. (See also Movie 2 at radiographics.rsnajnls.org/cgi/content/full/27/1/5/DC1.) (b, c) Posterior VR (b) and coronal oblique subvolume MIP (c) MR angiographic images demonstrate that the pulmonary arteries (LPA, RPA) are hypoplastic, confluent, and supplied by a single collateral artery (CA) from the descending aorta (AO). LA = left atrium, * = pulmonary veins. A right ventricle–pulmonary artery conduit was planned, but the patient died before surgery could be performed.

View larger version (143K): [in this window] [in a new window] [Download PPT slide]   Figure 4c.  Pulmonary atresia with intact ventricular septum in a 1-day-old girl. (a) Horizontal long-axis cine image shows a dilated, noncontracting right ventricle (RV) and a dilated right atrium (RA). LA = left atrium, LV = left ventricle. (See also Movie 2 at radiographics.rsnajnls.org/cgi/content/full/27/1/5/DC1.) (b, c) Posterior VR (b) and coronal oblique subvolume MIP (c) MR angiographic images demonstrate that the pulmonary arteries (LPA, RPA) are hypoplastic, confluent, and supplied by a single collateral artery (CA) from the descending aorta (AO). LA = left atrium, * = pulmonary veins. A right ventricle–pulmonary artery conduit was planned, but the patient died before surgery could be performed.

View larger version (146K): [in this window] [in a new window] [Download PPT slide]   Figure 5a.  Total anomalous pulmonary venous drainage in a 9-month-old girl. (a) Frontal chest radiograph shows increased pulmonary vasculature in the right lung, a finding that suggests obstruction of the right pulmonary veins. Arrow indicates the dilated superior vena cava. (b, c) Anterior (b) and posterior (c) VR MR angiographic images help confirm the asymmetric caliber of the peripheral pulmonary vessels but help exclude intrinsic obstruction of the pulmonary veins. The individual pulmonary veins (*) join together in a retrocardial venous confluence (**), which drains unobstructed into the dilated superior vena cava (arrows). The azygos vein (az) is located more laterally. (d, e) Short-axis (d) and horizontal long-axis (e) cine images show that the right ventricle (RV) and right atrium (RA) are markedly dilated and that the venous confluence (**) does not communicate with the atria. The ASD is not shown on these images. LA = left atrium, LV = left ventricle. (See also Movies 3 and 4 at radiographics.rsnajnls.org/cgi/content/full/27/1/5/DC1.)

View larger version (123K): [in this window] [in a new window] [Download PPT slide]   Figure 5b.  Total anomalous pulmonary venous drainage in a 9-month-old girl. (a) Frontal chest radiograph shows increased pulmonary vasculature in the right lung, a finding that suggests obstruction of the right pulmonary veins. Arrow indicates the dilated superior vena cava. (b, c) Anterior (b) and posterior (c) VR MR angiographic images help confirm the asymmetric caliber of the peripheral pulmonary vessels but help exclude intrinsic obstruction of the pulmonary veins. The individual pulmonary veins (*) join together in a retrocardial venous confluence (**), which drains unobstructed into the dilated superior vena cava (arrows). The azygos vein (az) is located more laterally. (d, e) Short-axis (d) and horizontal long-axis (e) cine images show that the right ventricle (RV) and right atrium (RA) are markedly dilated and that the venous confluence (**) does not communicate with the atria. The ASD is not shown on these images. LA = left atrium, LV = left ventricle. (See also Movies 3 and 4 at radiographics.rsnajnls.org/cgi/content/full/27/1/5/DC1.)

View larger version (124K): [in this window] [in a new window] [Download PPT slide]   Figure 5c.  Total anomalous pulmonary venous drainage in a 9-month-old girl. (a) Frontal chest radiograph shows increased pulmonary vasculature in the right lung, a finding that suggests obstruction of the right pulmonary veins. Arrow indicates the dilated superior vena cava. (b, c) Anterior (b) and posterior (c) VR MR angiographic images help confirm the asymmetric caliber of the peripheral pulmonary vessels but help exclude intrinsic obstruction of the pulmonary veins. The individual pulmonary veins (*) join together in a retrocardial venous confluence (**), which drains unobstructed into the dilated superior vena cava (arrows). The azygos vein (az) is located more laterally. (d, e) Short-axis (d) and horizontal long-axis (e) cine images show that the right ventricle (RV) and right atrium (RA) are markedly dilated and that the venous confluence (**) does not communicate with the atria. The ASD is not shown on these images. LA = left atrium, LV = left ventricle. (See also Movies 3 and 4 at radiographics.rsnajnls.org/cgi/content/full/27/1/5/DC1.)

View larger version (47K): [in this window] [in a new window] [Download PPT slide]   Figure 5d.  Total anomalous pulmonary venous drainage in a 9-month-old girl. (a) Frontal chest radiograph shows increased pulmonary vasculature in the right lung, a finding that suggests obstruction of the right pulmonary veins. Arrow indicates the dilated superior vena cava. (b, c) Anterior (b) and posterior (c) VR MR angiographic images help confirm the asymmetric caliber of the peripheral pulmonary vessels but help exclude intrinsic obstruction of the pulmonary veins. The individual pulmonary veins (*) join together in a retrocardial venous confluence (**), which drains unobstructed into the dilated superior vena cava (arrows). The azygos vein (az) is located more laterally. (d, e) Short-axis (d) and horizontal long-axis (e) cine images show that the right ventricle (RV) and right atrium (RA) are markedly dilated and that the venous confluence (**) does not communicate with the atria. The ASD is not shown on these images. LA = left atrium, LV = left ventricle. (See also Movies 3 and 4 at radiographics.rsnajnls.org/cgi/content/full/27/1/5/DC1.)

View larger version (117K): [in this window] [in a new window] [Download PPT slide]   Figure 5e.  Total anomalous pulmonary venous drainage in a 9-month-old girl. (a) Frontal chest radiograph shows increased pulmonary vasculature in the right lung, a finding that suggests obstruction of the right pulmonary veins. Arrow indicates the dilated superior vena cava. (b, c) Anterior (b) and posterior (c) VR MR angiographic images help confirm the asymmetric caliber of the peripheral pulmonary vessels but help exclude intrinsic obstruction of the pulmonary veins. The individual pulmonary veins (*) join together in a retrocardial venous confluence (**), which drains unobstructed into the dilated superior vena cava (arrows). The azygos vein (az) is located more laterally. (d, e) Short-axis (d) and horizontal long-axis (e) cine images show that the right ventricle (RV) and right atrium (RA) are markedly dilated and that the venous confluence (**) does not communicate with the atria. The ASD is not shown on these images. LA = left atrium, LV = left ventricle. (See also Movies 3 and 4 at radiographics.rsnajnls.org/cgi/content/full/27/1/5/DC1.)

In patients with hypoplastic left heart syndrome in whom left ventricular endocardial fibroelastosis is suspected at echocardiography, myocardial delayed-enhancement MR imaging may help determine the exact location of the fibrotic tissue and facilitate surgical resection (18).

Follow-up after Surgery or Catheter-guided Intervention
Surgical treatment of CHD involves either (a) complete correction in the neonatal period or (b) a staged approach consisting of several operations during infancy with various shunts and vascular anastomoses. Such vascular connections and the pulmonary arteries need to be regularly assessed for patency and possible stenosis. If echocardiography is inconclusive, MR angiography can reliably demonstrate the patency and caliber of a Blalock-Taussig or other systemic-to-pulmonary artery shunt, a cavopulmonary anastomosis (Fig 6), or a right ventricle–pulmonary artery conduit (9,19). Detection and treatment of pulmonary artery stenosis is important for ensuring sufficient growth of the peripheral pulmonary vasculature. Depending on the degree and hemodynamic consequences of a pulmonary artery stenosis, catheter-guided intervention or surgery may be necessary. MR imaging can provide both the morphologic and hemodynamic information required for decision making: MR angiography delineates the anatomy and degree of the stenosis, and flow measurements obtained in the pulmonary arteries reveal the resulting right-to-left flow distribution to the lungs (Figs 6, 7).

View larger version (69K): [in this window] [in a new window] [Download PPT slide]   Figure 6a.  Aortic stenosis in an 11-month-old boy with hypoplastic left heart syndrome. The patient had undergone a Norwood stage I procedure and bidirectional cavopulmonary anastomosis (Norwood stage II procedure). (a) Anterior (left) and posterior (middle, right) VR MR angiographic images demonstrate patency of the bidirectional cavopulmonary anastomosis, hypoplasia of the left pulmonary artery (LPA), and restenosis of the aortic isthmus (Coa). Lt IJV = left internal jugular vein, PAs = pulmonary arteries, RPA = right pulmonary artery, Rt IJV = right internal jugular vein, SVC = superior vena cava. (b) Anterior subvolume MIP MR angiographic image and graph illustrate how flow measurements obtained perpendicular to the superior vena cava (SVC) (red line) and left pulmonary artery (LPA) (yellow line) are used to calculate the right-to-left pulmonary flow ratio. In this case, the right-to-left flow ratio was 89%:11%, a finding that indicates significantly diminished flow to the left lung. (c) Horizontal long-axis cine image shows a hypoplastic left ventricle (LV) and thickening of the left pleura (arrows), findings that are indicative of a transpleural collateral blood supply to the left lung. LA = left atrium, RA = right atrium, RV = right ventricle. (See also Movie 5 at radiographics.rsnajnls.org/cgi/content/full/27/1/5/DC1.) On the basis of the MR imaging findings, catheter-guided dilation and stent placement in the aortic stenosis and left pulmonary artery were planned.

View larger version (38K): [in this window] [in a new window] [Download PPT slide]   Figure 6b.  Aortic stenosis in an 11-month-old boy with hypoplastic left heart syndrome. The patient had undergone a Norwood stage I procedure and bidirectional cavopulmonary anastomosis (Norwood stage II procedure). (a) Anterior (left) and posterior (middle, right) VR MR angiographic images demonstrate patency of the bidirectional cavopulmonary anastomosis, hypoplasia of the left pulmonary artery (LPA), and restenosis of the aortic isthmus (Coa). Lt IJV = left internal jugular vein, PAs = pulmonary arteries, RPA = right pulmonary artery, Rt IJV = right internal jugular vein, SVC = superior vena cava. (b) Anterior subvolume MIP MR angiographic image and graph illustrate how flow measurements obtained perpendicular to the superior vena cava (SVC) (red line) and left pulmonary artery (LPA) (yellow line) are used to calculate the right-to-left pulmonary flow ratio. In this case, the right-to-left flow ratio was 89%:11%, a finding that indicates significantly diminished flow to the left lung. (c) Horizontal long-axis cine image shows a hypoplastic left ventricle (LV) and thickening of the left pleura (arrows), findings that are indicative of a transpleural collateral blood supply to the left lung. LA = left atrium, RA = right atrium, RV = right ventricle. (See also Movie 5 at radiographics.rsnajnls.org/cgi/content/full/27/1/5/DC1.) On the basis of the MR imaging findings, catheter-guided dilation and stent placement in the aortic stenosis and left pulmonary artery were planned.

View larger version (162K): [in this window] [in a new window] [Download PPT slide]   Figure 6c.  Aortic stenosis in an 11-month-old boy with hypoplastic left heart syndrome. The patient had undergone a Norwood stage I procedure and bidirectional cavopulmonary anastomosis (Norwood stage II procedure). (a) Anterior (left) and posterior (middle, right) VR MR angiographic images demonstrate patency of the bidirectional cavopulmonary anastomosis, hypoplasia of the left pulmonary artery (LPA), and restenosis of the aortic isthmus (Coa). Lt IJV = left internal jugular vein, PAs = pulmonary arteries, RPA = right pulmonary artery, Rt IJV = right internal jugular vein, SVC = superior vena cava. (b) Anterior subvolume MIP MR angiographic image and graph illustrate how flow measurements obtained perpendicular to the superior vena cava (SVC) (red line) and left pulmonary artery (LPA) (yellow line) are used to calculate the right-to-left pulmonary flow ratio. In this case, the right-to-left flow ratio was 89%:11%, a finding that indicates significantly diminished flow to the left lung. (c) Horizontal long-axis cine image shows a hypoplastic left ventricle (LV) and thickening of the left pleura (arrows), findings that are indicative of a transpleural collateral blood supply to the left lung. LA = left atrium, RA = right atrium, RV = right ventricle. (See also Movie 5 at radiographics.rsnajnls.org/cgi/content/full/27/1/5/DC1.) On the basis of the MR imaging findings, catheter-guided dilation and stent placement in the aortic stenosis and left pulmonary artery were planned.

View larger version (92K): [in this window] [in a new window] [Download PPT slide]   Figure 7a.  Pulmonary artery stenosis in a 9-month-old girl who had undergone repair of pulmonary atresia with VSD. MR imaging was performed for assessment of the pulmonary arteries. (a) Angulated anterior VR MR angiographic image shows severe stenosis of the left pulmonary artery (arrow). (b) Velocity-encoded phase-contrast magnitude and phase images and graph illustrate flow measurements obtained perpendicular to the pulmonary arteries (LPA [yellow], RPA [red]) showing diminished flow to the left lung and indicating that the LPA stenosis is hemodynamically significant. On the basis of the MR imaging findings, catheter-guided intervention was performed. (c, d) Cranially angulated anterior angiograms obtained before (c) and after (d) intervention help confirm the LPA stenosis (arrow in c) and demonstrate the results of dilation and stent placement.

View larger version (61K): [in this window] [in a new window] [Download PPT slide]   Figure 7b.  Pulmonary artery stenosis in a 9-month-old girl who had undergone repair of pulmonary atresia with VSD. MR imaging was performed for assessment of the pulmonary arteries. (a) Angulated anterior VR MR angiographic image shows severe stenosis of the left pulmonary artery (arrow). (b) Velocity-encoded phase-contrast magnitude and phase images and graph illustrate flow measurements obtained perpendicular to the pulmonary arteries (LPA [yellow], RPA [red]) showing diminished flow to the left lung and indicating that the LPA stenosis is hemodynamically significant. On the basis of the MR imaging findings, catheter-guided intervention was performed. (c, d) Cranially angulated anterior angiograms obtained before (c) and after (d) intervention help confirm the LPA stenosis (arrow in c) and demonstrate the results of dilation and stent placement.

View larger version (114K): [in this window] [in a new window] [Download PPT slide]   Figure 7c.  Pulmonary artery stenosis in a 9-month-old girl who had undergone repair of pulmonary atresia with VSD. MR imaging was performed for assessment of the pulmonary arteries. (a) Angulated anterior VR MR angiographic image shows severe stenosis of the left pulmonary artery (arrow). (b) Velocity-encoded phase-contrast magnitude and phase images and graph illustrate flow measurements obtained perpendicular to the pulmonary arteries (LPA [yellow], RPA [red]) showing diminished flow to the left lung and indicating that the LPA stenosis is hemodynamically significant. On the basis of the MR imaging findings, catheter-guided intervention was performed. (c, d) Cranially angulated anterior angiograms obtained before (c) and after (d) intervention help confirm the LPA stenosis (arrow in c) and demonstrate the results of dilation and stent placement.

View larger version (122K): [in this window] [in a new window] [Download PPT slide]   Figure 7d.  Pulmonary artery stenosis in a 9-month-old girl who had undergone repair of pulmonary atresia with VSD. MR imaging was performed for assessment of the pulmonary arteries. (a) Angulated anterior VR MR angiographic image shows severe stenosis of the left pulmonary artery (arrow). (b) Velocity-encoded phase-contrast magnitude and phase images and graph illustrate flow measurements obtained perpendicular to the pulmonary arteries (LPA [yellow], RPA [red]) showing diminished flow to the left lung and indicating that the LPA stenosis is hemodynamically significant. On the basis of the MR imaging findings, catheter-guided intervention was performed. (c, d) Cranially angulated anterior angiograms obtained before (c) and after (d) intervention help confirm the LPA stenosis (arrow in c) and demonstrate the results of dilation and stent placement.

View larger version (127K): [in this window] [in a new window] [Download PPT slide]   Figure 8a.  Restenosis in a 4-month-old girl who, as a neonate, had undergone reconstruction of the aorta for hypoplasia and coarctation. (a, b) Left anterior oblique VR (a) and subvolume MIP (b) MR angiographic images reveal restenosis of the aortic arch, including the origin of the left subclavian artery (arrow). On the basis of the MR angiographic findings, it was decided to perform catheter-guided dilation of the aorta and subclavian artery. (c, d) Left anterior oblique angiograms help confirm the degree of stenosis seen at MR angiography and show a good result after dilation.

View larger version (153K): [in this window] [in a new window] [Download PPT slide]   Figure 8b.  Restenosis in a 4-month-old girl who, as a neonate, had undergone reconstruction of the aorta for hypoplasia and coarctation. (a, b) Left anterior oblique VR (a) and subvolume MIP (b) MR angiographic images reveal restenosis of the aortic arch, including the origin of the left subclavian artery (arrow). On the basis of the MR angiographic findings, it was decided to perform catheter-guided dilation of the aorta and subclavian artery. (c, d) Left anterior oblique angiograms help confirm the degree of stenosis seen at MR angiography and show a good result after dilation.

View larger version (142K): [in this window] [in a new window] [Download PPT slide]   Figure 8c.  Restenosis in a 4-month-old girl who, as a neonate, had undergone reconstruction of the aorta for hypoplasia and coarctation. (a, b) Left anterior oblique VR (a) and subvolume MIP (b) MR angiographic images reveal restenosis of the aortic arch, including the origin of the left subclavian artery (arrow). On the basis of the MR angiographic findings, it was decided to perform catheter-guided dilation of the aorta and subclavian artery. (c, d) Left anterior oblique angiograms help confirm the degree of stenosis seen at MR angiography and show a good result after dilation.

View larger version (143K): [in this window] [in a new window] [Download PPT slide]   Figure 8d.  Restenosis in a 4-month-old girl who, as a neonate, had undergone reconstruction of the aorta for hypoplasia and coarctation. (a, b) Left anterior oblique VR (a) and subvolume MIP (b) MR angiographic images reveal restenosis of the aortic arch, including the origin of the left subclavian artery (arrow). On the basis of the MR angiographic findings, it was decided to perform catheter-guided dilation of the aorta and subclavian artery. (c, d) Left anterior oblique angiograms help confirm the degree of stenosis seen at MR angiography and show a good result after dilation.

View larger version (176K): [in this window] [in a new window] [Download PPT slide]   Figure 9.  Rhabdomyomas. Horizontal long-axis spin-echo T1-weighted MR image shows isointense rhabdomyomas (white *) involving the ventricular septum and the posterior wall of the left ventricle (LV). The hyperintense lesion (black *) in the wall of the right atrium (RA) is probably a lipoma. LA = left atrium, RV = right ventricle.

View larger version (131K): [in this window] [in a new window] [Download PPT slide]   Figure 10a.  Fibroma. Coronal spin-echo T1-weighted MR images obtained before (a) and after (b) the intravenous administration of gadolinium-based contrast material show a large fibroma involving the free wall of the right ventricle (RV) and compressing the right ventricular cavity. Compared with normal myocardium, the tumor shows increased enhancement with relative sparing of its core, findings that are considered characteristic of a fibroma. e = pericardial effusion, LV = left ventricle.

View larger version (134K): [in this window] [in a new window] [Download PPT slide]   Figure 10b.  Fibroma. Coronal spin-echo T1-weighted MR images obtained before (a) and after (b) the intravenous administration of gadolinium-based contrast material show a large fibroma involving the free wall of the right ventricle (RV) and compressing the right ventricular cavity. Compared with normal myocardium, the tumor shows increased enhancement with relative sparing of its core, findings that are considered characteristic of a fibroma. e = pericardial effusion, LV = left ventricle.

	Conclusions

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Imaging Technique Common Clinical Indications Conclusions References

	Footnotes

 

Abbreviations: ASD = atrial septum defect, AVSD = atrioventricular septum defect, CHD = congenital heart disease, MIP = maximum-intensity-projection, 3D = three-dimensional, VR = volume-rendered, VSD = ventricular septum defect

	References

Top Abstract LEARNING OBJECTIVES FOR TEST... Introduction Imaging Technique Common Clinical Indications Conclusions References

 

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