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Master Class ExamCards for pediatric cardiovascular MRI - RU Bochum

Best Practice
Dr. Beerbaum, Philipp Bad Oeynhausen, Heart and Diabetes Center Germany

In 2005, Philips asked clinicians at Ruhr-University Bochum's Clinic for Congenital Heart Disease, Heart and Diabetes Center (Bad Oeynhausen, Germany) to develop Master Class ExamCards that would cover 80% of pediatric heart scans encountered daily in cardiac imaging centers. A major European heart center, Ruhr-University Bochum is uniquely qualified to provide the most sophisticated and comprehensive pediatric cardiac scanning protocols. Converting this expertise into pre-packaged, Internet-downloadable ExamCards will enable other Philips MR users to improve their existing pediatric cardiac scanning programs or implement a new cardiac MR service. Ruhr-University Bochum plans to develop 25-30 ExamCards, spanning four different pediatric patient groups, according to pediatric cardiologist, Philipp Beerbaum, M.D.

 

Philipp Beerbaum, M.D.
Philipp Beerbaum, M.D.

 

Echocardiography maintains an exalted position among imaging modalities in cardiac scanning for infants, children and adults - providing non-invasive, useful depictions of heart structures and information on cardiac flow in color. At Ruhr-University Bochum, echocardiography is the sole imaging technique used in 60-70% of heart scans on infants, and for all other patients, echo still is considered the first line imaging modality provided an adequate acoustic window is available. In the planning of interventions, however, complex cases and the need for quantitative data demand capabilities that only MRI can offer.

 

"Echo approaches its limits in cases requiring great vessel anatomy or information on quantitative function, and in cases calling for exclusion of atypical coronary artery origins," says Philipp Beerbaum, M.D., pediatric cardiologist at Ruhr-University Bochum, which uses a Philips Intera 1.5T system. "In addition, older children who had undergone previous surgery for complex congenital heart defects may present with important post-repair residual problems, such as branch pulmonary artery stenoses or aortic arch coarctation, or residual valve problems, such as stenosis or regurgitation - all of which require high-resolution morphology as well as quantification to assess their severity and the urgency of treatment. To follow these patients I want a precise modality such as MRI."

The scope of pediatric cardiac MRI

Pediatric cardiology presents a wide spectrum of MRI scanning scenarios, due to the heterogeneous patient base (scaling from neonates to teenagers) and use or avoidance of sedation and general anesthetics, depending on the degree to which the patient is cooperative or uncooperative. Accordingly, Ruhr-University clinicians sort patients into four categories:

 

Group A: Newborns & infants up to 8 kg. General anesthetics.

Synergy Head Neck coil.

Group B: Smaller children over 8 kg up to 25-30 kg (i.e. < 6-7-years-old). General anesthetics. SENSE Cardiac coil.

Group C: Smaller children over 8 kg up to 25-30 kg (i.e. < 6-7-years-old). Sedation.

SENSE Cardiac coil.

Group D: Cooperative older children (usually > 6-7 years of age).

SENSE Cardiac coil.

 

Principally, each patient group is subject to one or more of six cardiac MRI applications: (1) planning, (2) cardiac morphology, (3) great vessels and airways, (4) angiography, (5) quantitative flow, and (6) ventricular function.

ExamCards reduce protocol selection complexity

 Beerbaum FS27
Beerbaum FS27

 

When Philips approached Dr. Beerbaum and his colleagues about converting Ruhr-University's pediatric cardiac MRI protocols into ExamCards, Dr. Beerbaum recommended developing the downloadable Philips protocols based on the foregoing patient-based classifications. "We agreed to provide ExamCards for each of the four patient groups for specific lesions that are very common in our clinical practice," he says. "An ExamCard for Group C, for example, would be a combination of two lesions - sinus venous atrial septal defect (View ExamCard below: Group C - ASD and PAPVR) and anomalous pulmonary venous return (See example 2). Sedation in experienced hands may do the job and time-effectively replace general anesthetics in a simple defect of this kind. This would be a perfect setup where we could provide free breathing ventricular function sequences, time-of-flight ("inflow") MR angiography, quantitative flow protocols and phase-contrast pulse sequences that are very useful for defining the location, size and shape of an ASD."


Example 2:

  Partial anomalous pulmonary venous return, Group C

  Free-breathing, axial multiphase inflow MRA depicts anomalies

  of pulmonary and systemic veins that can be difficult to assess

  with echo. ~40 slices at 3.5-4.5 mm slice thickness (0.5 mm

  overlap to enable 3D reformat) with 1.2 x 1.6 mm in-plane

  resolution and 4-5 phases can be acquired in ~4-5 minutes.

  A: Slab coronal reformat of axial 2D inflow slices (B) to display

  origin, course and drainage site of vertical vein collecting all

  pulmonary venous blood from left lung and draining to left

  innominate vein.

  B: Axial inflow MRA slice at level of pulmonary artery, displaying

  enlarged superior vena cava (SVC) and large anomalous

  "vertical" pulmonary vein ascending to the left innominate vein.


 

While questions of infant (Group A) cardiac morphology are typically resolved with echo, any additional great vessel pathology as well as need for quantitative ventricular function would be referred for an MRI exam, for which Ruhr-University has developed an ExamCard. "These are usually more complex lesions that we don't want to catheterize just for simple diagnostic purpose," Dr. Beerbaum says. "MRI can better depict the coronary anomalies and more subtle anatomic configurations such as the relation of a ventricular septal defect to the great arteries (e.g. double-outlet right ventricle), and any complex anomalies of the great vessels - pulmonary veins, systemic veins, pulmonary arteries and the aortic arch. MRI also is perfectly suited for such complex situations as the rare and hard-to-diagnose heterotaxy syndromes (Example 3). These are the types of applications for which we want to provide ExamCards."

 


Example 3:

  Complex congenital heart defects in infants, Group A

  Breath-hold  

  A: Coronal reformat from 20-sec. breath-hold multi-dynamic

  3D CE-MRA to delineate total anomalous pulmonary venous

  drainage (TAPVR) in 5-kg infant. Left upper lobe pulmonary

  vein (arrow) drains to left innominate vein; all other pulmonary

  veins (arrows) drain into collecting sinus (S) that connects to

  coronary sinus in this case.

  B: Similar  scan to delineate non-confluent pulmonary arteries

  in 4-kg newborn with bilateral persistent ductus arteriosus (arrows)

  to each lung (a = right aortic arch).


 

Additional ExamCards (e.g. "post-repair Tetralogy of Fallot & pulmonary atresia") focus on smaller children (Group B) whose known cardiac abnormality needs to be assessed on a functional level to determine when re-intervention is needed and to plan the procedure. In this situation, breath-hold scans such as multislice cine Balanced TFE for ventricular function and 3D contrast-enhanced MRA to depict possible pulmonary artery pathology are mandatory and request general anesthetics with muscle relaxation. An ExamCard such as "d-Transposition after arterial switch operation (ASO)" for cooperative older children and young adults (Group D) is useful as a follow-up study because a well-known complication of this type of corrective surgery performed to correct transposition of the great arteries is branch stenosis of the pulmonary arteries developing later in life (Example 4). This Exam- Card would also contain a whole-heart 3D isotropic SSFP scan to rule out proximal coronary stenosis after coronary reimplantation during ASO. For those patients with d-Transposition who had an atrial baffle surgical repair (e.g. Mustard operation), another ExamCard was designed to specifically cover complications such as baffle stenosis (Example 5) or leakage.

 


Example 4: 

  Supravalvular pulmonary stenoses and coronaries after

  arterial switch operation (ASO) in d- transposition of

  great arteries, Group D

  Mix of breath-hold (e.g. CE-MRA) and non-breath-hold scans

  used as needed.

  Left: Sagittal reformat of coronal 3D CE-MRA to image a supravalvular

  stenosis of main (PA) and left pulmonary artery (LPA, arrows) after

  ASO in d-Transposition.

  Right: Coronal reformat to delineate main pulmonary artery (PA)

  stenosis (arrow) and mild tubular stenosis of right pulmonary artery

  (RPA, arrow). RV = right ventricle, LV = left ventricle.

 

 


Example 5:

  Baffle stenosis after Mustard operation for d-Transposition

  of great arteries, Group D

 

  To assess possible complications, such as baffle stenosis or leakage.

  A: Coronal reformat of an isotropic 3D SSFP whole-heart sagittal data

  set to delineate marked stenosis (arrows) of baffle part, which directs

  blood from superior vena cava (SVC) to sub-pulmonary left ventricle.

  B: Left-anterior-oblique reformatted view from a coronal 3D CE-MRA

  data set, demonstrating bypass of SVC blood using azygos vein (AZ)

  down to inferior vena cava (IVC), secondary to superior baffle

  obstruction (arrow).

 


 

"ExamCards should guide clinicians to the appropriate set of pulse sequences to use for specific indications seen in everyday practice," Dr. Beerbaum observes. "But in every clinical situation, physicians may encounter difficult anatomy or variability in anatomy and pathology between patients that forces them to individualize their approach. For that reason, an ExamCard should be viewed as a comprehensive set of scans - a 'maximum' version - for a certain indication that allows sequences to be deleted or replaced. Only very rarely is there a completely standardized examination in a child with a congenital heart disease.

 

"Therefore, the idea of 'toolboxes' containing individual sequences that can be added to an ExamCard to modify it, is an attractive concept," he continues, "and one that we're recommending to Philips for pediatric cardiac MRI."

Toolbox approach designed to conform ExamCard to case

Because patient sizes vary more in pediatric MRI than in any other scanning area, a onesize- fits-all strategy in cardiac scanning could present difficulties, even with ExamCards organized into concrete groups, according to Dr. Beerbaum.

 

If I have an ExamCard for Pre-operative Fallot in a seven kilogram patient, then you might do very well with the ExamCard sequence we recommend for ┤cardiac morphology┤," he says. "However, there are other sequences you also could use - black blood, cine TFEs or Balanced FFE sequences - that you believe would yield better results for that particular patient or patient group."

 

In this respect, the previously noted six cardiac MRI applications for each patient group (Groups A-D): planning, cardiac morphology, airways and great vessels, angio, q-flow and ventricular function, become toolboxes containing a variety of sequences that clinicians could alternatively import into a given ExamCard if deemed necessary.

 

Arguably, Ruhr-University clinicians could assemble ExamCards for every conceivable pediatric cardiac application, he points out. However, utilizing clinicians' judgment on ExamCard selection and modification via the toolbox approach is a better alternative than the potential confusion that a multitude of ExamCards could create.

 

"We could produce one ExamCard for every lesion in every age group, but with that many ExamCards, many will sound similar and radiologists will find it very difficult to choose the right one and the differences are mainly adaptations to body size, anyway," Dr. Beerbaum says. "It's better to have ExamCards represent examples for demonstrating the underlying principles of an age group and respective examination setup. Still, each ExamCard would cover quite a lot of different aspects of cardiac MRI exams, so the user would certainly still be allowed and sometimes even advised to skip a few scans or refer to the corresponding toolbox for good alternatives."

3D sequences in research could simplify CMR acquisition

Dr. Beerbaum and his colleagues are working on developing 3D sequences to the point where they could be integrated into all ExamCards, as is 3D CE-MRA in Ruhr- University's proposed ExamCards. Acquiring 3D scans of the whole heart for example, using a 3D SSFP technique, could make the acquisition completely operator-independent1. Because the 3D image data have isotropic resolution, reformatting in any desired plane is possible during postprocessing, eliminating the time needed to set up a scan and the possibility for error.

 

"Single-phase 3D isotropic SSFP is clinical routine and will be part of the ExamCards we will suggest for cardiac morphology sequences," he says. "Other groups have started on multiphase 3D SSFP based on kt-BLAST2, so some of this is technically around the corner, with the exception of 3D flow at present. All approaches must however still confirm clinical usefulness, but we're confident ExamCards will become increasingly 3D in the future."

References

1. Sørensen TS, Körperich H, Greil GF, Eichhorn J, Barth P, Meyer H, Pedersen EM, Beerbaum P.

Operator-independent isotropic three-dimensional magnetic resonance imaging for morphology in congenital heart disease.

Circulation, 2004;110:163-169.

 

2. Kozerke S,Tsao J, Razavi R, Boesiger P.

Accelerating cardiac cine 3D imaging using kt-BLAST.

Magn Reson Med. 2004;5019-26.



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