Cardiac Protocol

Overview

Cardiac MR imaging has become the new gold standard for the evaluation of cardiac anatomy, function and for characterizing cardiac masses. Multi-plan imaging capability of MRI makes it well suited modality for evaluating the complex anatomy of the heart, complex congenital cardiac anomalies, and cardiac functions. Besides high quality morphological imaging, cardiac MRI also allows the evaluation of the myocardial wall motion, calculation of left & right ventricle volumes, mass, stroke volume, ejection fraction , and demonstration of myocardial perfusion of ischemic heart. The other advantage of cardiac MRI is the ability of obtaining blood flow measurements (flow volume and flow velocity) through the cardiac valves, aorta and pulmonary arteries, so that the regurgitation fractions, Qp /Qs and significance of diseases can be evaluated.  

Common Indications ICD9 Codes

745

Bulbus Cordis anomalies and anomalies of cardiac septal closure

 

745.0

Common truncus

 

745.1

Transposition of great vessels

 

745.2

Tetraogy of Fallot

 

745.3

Common ventricle

 

745.4

Ventricular septal defect

 

745.5

Ostium secundum type atrioseptal defect

 

745.6

Endocardial cushion defect

746

Other congenital anomalies of the heart

 

746.0

Anomalies of pulmonary valve

 

746.1

Tricuspid atresia and stenosis

 

746.2

Ebstein’s anomaly

 

746.3

Congenital stenosis of aortic valve

 

746.4

Congenital insufficiency of aortic valve

 

746.5

Congenital mitral stenosis

 

746.6

Congenital mitral insufficiency

 

746.7

Hypoplastic left heart syndrome

 

746.81

Subaortic stensis

 

746.82

Cor triatrium

 

746.83

Infundibular pulmonic stenosis

 

746.87

Malposition of heart and cardiac apex

 

746.89

Congenital cardiomegaly, pericardial defect, diverticulum

394

Diseases of mitral valve (rheumatic)

395

Diseases of aortic valve (rheumatic)

396

Diseases of aortic and mitral valves (rheumatic)

402

Hypertensive heart disease

410-414

Ischemic heart disease

414.1

Aneurysm and dissection of heart

421

Acute and subacute endocarditis

424.0

Mitral valve disorders (except rheumatic)

424.1

Aortic valve disorders (except rheumatic)

424.2

Tricuspid valve disorders (except rheumatic)

424.3

Pulmonary valve disorders (except rheumatic)

425

Cardiomyopathies

427.3

Atrial Fibrillation

428

Heart failure

420

Acute pericarditis

420.9

Acute pericardial effusion

421

Acute and subacute endocarditis

422

Acute myocarditis

423

Other diseases of pericardium

 

423.0

Hemopericardium

 

423.1

Adhesive pericarditis

 

423.2

Constructive pericarditis

 

423.9

Pericarditis with effusion

212.8

Benign neoplasm of heart

215.4

Benign neoplasm of great vessels

212.5

Benign neoplasm of mediastinum

164.9

Malign neoplasm of mediastinum

164.1

Malign neoplasm of the heart (endocardium, epicardium, myocardium, pericardium

198.89

Secondary malign neoplasm

212.7

Benign neoplasm

V42.1

Transplanted heart

V42.2

Transplanted valve

         

           

           

           

         

           

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 Scheduling Guidelines

 First Ask;    1- Why is the cardiac MRI being requested?

                    2- Do you have pacemaker, or cardiac defibrillator? Is it MR compatible?

3- Have you ever had cardiac surgery? If the answer is ‘yes’ ask ‘when’ and ‘why’.

4- Have you ever been diagnosed for ischemic or congenital heart disease?

  Patient Preparation

 ·        Contraindications include the presence of a cardiac pacemaker, cardiac defibrillator, and Swan-Ganz catheter. MR study is also recommended to be delayed for 6 to 8 weeks after an implant or coronary stent placement.

·        The cardiac MRI for functional evaluation alone does not require Gd injection. If the patient has a mass, ischemic heart disease or congenital heart disease, then he/she will require Gd injection. If necessary for the further evaluation of cardiopulmonary structures, start an iv line (20 or 22 gauge).

·        ECG gating is essential for cardiac imaging. First, prepare the skin for lead placement. If necessary, shave the body hairs for maximum lead-skin contact and scrub the skin with an abrasive to create edema to improve electrical conductivity. Position the ECG electrodes (RA, LA, RL and LL) on the chest of the patient (in supine position, the most motionless area is the posterior chest). It is best to use MRI electrodes which have no metal (only carbon snaps) and a large surface area with abundant lubrication to minimize burns. Do not place leads over bony areas and avoid looping ECG leads which may result in superficial burns and can increase electrical interference from gradient activity. Leads should not be too far away from each other. Click ‘Gating control’ from the Rx manager area, turn on the advanced ECG gating. View R waves for at least 16 heart cycles while patient is lying down still. If there is a difficulty in detecting the R waves, or the R wave amplitude is low (<1mV) reposition the ECG leads. The detected vectors will be I, II, or III leads. Choose the one which has a clean trace. Whenever you change the lead, do not forget to update the R-peak amplitude. If some of the R waves are missing trigger marks, reduce ‘Cardiac Trigger Level’ to 50%.

·        Both fast breath-held and respiratory triggered sequences are used in cardiac studies. For respiratory gating and triggering, place the respiratory monitoring bellows around the patient’s abdomen or chest, so the operator will know if the patient is cooperating with breathing instructions.

·        Valium (5-10mg po) or Xanax (1-2 mg po) if patient is claustrophobic.

·        Provide ear plugs or music headphones. 

Coil: In adults 8 channel cardiac phased array coil, in infants knee coil or head coil.

Patient positioning: Supine, feet first. Placing the arms above the head decreases wrap around artifact. But most adults cannot tolerate arms overhead for extended periods and thus along the side or crossed over the chest is acceptable. Place comfortable pillows for head and arm support, and a cushion under the knees to relieve pressure on the lower back.

Landmark: Advance the table into the magnet bore, and landmark at mid-sternum (mid-chest). The upper edge of the posterior coil should be above the cranial edge of scapula. The upper edge of the anterior coil should be at the clavicle level. Do not let the anterior and posterior coil elements touch each other.

 

CARDIAC SEQUENCES

 

3-plane

Localizer

ASSET Calibration

Ax T1 DIR

Shim Fiesta

2C, 4C, SA Fiesta

Sag DIR

Sag TIR

Coronal 3D MRA

Aorta and MPA PC

IMAGING PARAMETERS

Plane

3-plane

Axial

Axial

Oblique

Oblique

Oblique

Oblique

Coronal

Oblique

Mode

2D

2D

2D

2D

2D

2D

2D

3D

2D

Pulse Sequence

Localizer

Fast GRE

FSE-XL

SE

Fiesta

FSE

FSE-IR

Fast TOF GRE

Fast 2D PC

Imaging Options

None

Fast,Calib

Gat,Seq,BSP,

ZIP512,Fast,Asset

None

Gat,Seq,

Asset,Fast

Gat,Seq,VBw

BSP,Fast

Gat,Seq,VBw

BSP,Fast

MPh,ZIP512,

ZIP2,Asset,Fast

Gat,Seq,FC,

Fast

SCAN TIMING

# of Echoes

1

1

1

1

1

1

1

1

1

TE

 

 

42

Min Full

Minimum

42

42

Minimum

Minimum

TR

 

 

 

300

 

 

 

 

 

Flip Angle

 

 

 

 

40

 

 

30

30

Bandwidth

 

 

62.50

15.63

125.00

62.50

62.50

62.50

31.25

ETL

 

 

32

 

 

32

32

 

 

BSP TI

 

 

Auto

 

 

Auto

Auto

 

 

Inv Time

 

 

 

 

 

 

150

 

 

ADDITIONAL PARAMETERS

SAT

 

 

 

 

 

1

 

 

 

Multiphase

 

 

 

 

 

 

 

3 phases/loc

 

ACQUISITION TIMING

Freq

256

 

256

256

256

256

256

512

256

Phase

128

 

256

256

192

256

256

256

256

NEX

1

 

1

1

1

1

1

1

1

Phase FOV

1

 

0.75

1

1

0.75

0.75

1

1

#acq/locs Bef Pause

 

0

1

 

1

1

1

1

 

Freq DIR

 

R/L

R/L

Unswap

Unswap

S/I

S/I

S/I

Unswap

Auto Cent Freq

Water

Water

Water

Water

Water

Water

Water

Water

Water

Auto Shim

 

Yes

Yes

Yes 

 

Yes

Yes

Yes

Yes

Phase Correct

 

 

Yes

Yes

 

Yes

Yes

 

 

SCANNING RANGE

FOV

48

48

28

12

40

28

28

40

32

Slice Thickness

10

8

8

8

8

8

8

4

6

Spacing

10

 

0

0

0

0

0

 

10

Start – End

 

I240-S240

L15-L15.1

L43-L43

 

L84-R20

L84-R20

 

 

# Slices

9/plane

61

12

 

 

14

14

 

 

Cardiac Phases

 

 

 

 

20

 

 

 

 

Locs per slab

 

 

 

 

 

 

 

42

 

Scan Time

0:28

0:12

2:22

1:23

0:09

2:52

2:44

1:22

0:23

 

 

MYOCARDIAL VIABILITY AND PERFUSION

 

3-Plane Localizer

PC

TAGS Grid

Fast Cine

Non-gated Fiesta

TRICKS

Perfusion FGRE ET

Delayed

Enhancement

IMAGING PARAMETERS

Plane

3-plane

Oblique

Oblique

Oblique

Sagittal

Coronal

Oblique

Oblique

Mode

2D

2D

2D

2D

2D

3D

2D

2D

Pulse Sequence

Localizer

Vasc PC

Fast Card GRE

Fast Card SPGR

Fiesta

TRICKS

Fast GRE ET

Fast GRE

Imaging Options

None

FC,Gat,Seq,Fast

 

FC,Gat,Seq,Fast

FC,Gat,Seq,Fast

Seq,Fast

ZIP2,Fast

Fast,ET

Gat,IrP,Fast

SCAN TIMING

# of Echoes

1

1

1

1

1

1

1

1

TE

 

Min Full

Min Full

Min Full

Min Full

Minimum

Min Full

Min Full

TR

 

 

 

 

 

 

 

 

Flip Angle

 

20

20

20

45

25

20

20

Bandwidth

 

15.63

31.25

31.25

125.00

62.50

125.00

31.25

ETL

 

 

 

 

 

 

4

 

BSP TI

 

 

 

 

 

 

 

 

Prep Time

 

 

 

 

 

 

 

297

ADDITIONAL PARAMETERS (see attached instructions)

SAT

 

 

Sat TAG Grid

 

 

 

 

 

ACQUISITION TIMING

Freq

256

256

256

256

224

512

128

256

Phase

128

192

128

128

224

160

128

160

NEX

1

3

4

1

1

1

 

1

Phase FOV

1

0.75

0.75

0.75

0.75

1

0.75

0.75

#acq/locs Bef Pause

 

 

 

 

0

 

 

1

Freq DIR

 

Unswap

Unswap

Unswap

S/I

S/I

S/I

R/L

Auto Cent Freq

Water

Water

Water

Water

Water

Water

Water

Water

Auto Shim

No

Yes

Yes

Yes

Yes

Yes

Yes

Yes

Phase Correct

 

 

 

 

 

 

 

 

SCANNING RANGE

FOV

36

25

34

40

35

30

35

35

Slice Thickness

5

5

8

8

8

4

10

8

Spacing

2

0

TAG Spacing: 7

0

0

 

0

0

Start – End

L50

L36.7

L39-L39

 

L101.8-R58.2

 

L54.9-R9

L55-L10.7

# Slices

5/plane

 

 

 

21

 

10

10

# of Scan Locs

 

 

 

 

 

24

 

 

Scan Time

0:16

1:02

0:46

0:08

0:13

1:22 (0:21)

(Temp Resol: 0:05)

0:02

3.17

                        Calib: ASSET calibration     BSP: Blood suppression   Seq: Sequential   Gat: Cardiac gating

 

Series 1: 3-plane localizer

This is a quick localizer sequence obtained in 3 planes during single breath-hold. Images are used to confirm optimal patient positioning and to prescribe the further acquisitions.

Series 2: ASSET Calibration

Array spatial sensitivity encoding technique (ASSET) is a parallel imaging technique which uses independent signals from each of the coil elements to accelerate data acquisition. Prior to image acquisition with ASSET, a single breath hold low resolution reference scan (ASSET calibration) must be run to determine the sensitivity of all coils in the phased array coil. These sensitivity maps are needed to unwrap the aliasing in the ASSET scan. ASSET calibration FOV is set to 48 cm and should be prescribed from the top of the coil to the bottom of the coil.  

Series 3: Axial double-inversion recovery (DIR):

·        DIR provides fine details of the boundary between the lumen and the wall of the cardiac chambers and main vascular structures, pericardium, and mediastinal tissues.

·        DIR is a black blood T1 fast spin echo (FSE-XL) technique in which the signal from blood is suppressed. Blood suppression inversion time (BSP TI) is described as the duration between the initial inversion pulse and time point that longitudinal magnetization of blood reaches zero (null) point. Readout begins at BSP TI. At this point the blood in the imaging slice gives no signal (black blood).

·        BSP TI is around 650 ms with a 60 beat per minute heart rate at 1.5 T. When the “auto” option in the scanning parameters area used, computer calculates the BSP TI depending on the heart rate of the patient. The “auto” BSP TI selection assumes that there is no contrast in the blood, and calculates a high BSP TI for the selected parameters. BSP TI can be decreased by using a wider receive bandwidth, shorter echo train length (ETL) and/or narrow trigger window. Wide bandwidth also decreases the blurring caused by long ETLs at the expense of SNR.

·        If the flow is slow or in-plane, it is possible to fail in complete suppression of the signal from blood. In this case TE may be increased or the image plane is changed to obtain a better blood suppression.

·        DIR is single-slice (one image per acquisition) technique typically with breath holding. Multiple images are acquired with multiple breath-holds. By using ASSET, one can speed up the acquisition in order to obtain 2-3 images per breath-held or higher resolution images with more phase encode steps. The patient is instructed to hold his/her breath in expiration, so that the end diastolic volume in the cardiac chambers would be the same during entire scanning. If the patient has difficulty in breath holding in expiration, breath-holding in inspiration is also acceptable. If the patient is unable to hold his/her breathe at all, the number of acquisition can be increased to 3 or 4 NEX in order to average out respiratory motion.

·        Prescribe the axial series on coronal localizer, and cover all thoracic structures. 

 


 

Series 4: Optional Axial triple IR (TIR)

Triple IR uses an FSE-IR pulse sequence. An additional preparation pulse is applied to null the fat signal. The inversion time for nulling the fat at 1.5 T is approximately 150 ms. Using a TE of about 40 ms and nulling fat emphasizes the T2 property of the tissues. This sequence is especially useful when there is a suspicion for inflammation (e.g. vasculitis) or cardiac mass. ASSET shortens the imaging time.

Series 5: Shim FIESTA

·        FIESTA (fast imaging employing steady-state acquisition) is a variant of steady-state free precession pulse (SSFP) sequence and uses fast-ECG gated, segmented k-space acquisition. The image contrast is determined by T2/T1 ratio of the tissue. Blood has much higher T2/T1 ratio than the myocardium, thus FIESTA gives an excellent contrast between blood and myocardium. Visualization of valve leaflets, papillary muscles, and pericardium are also good with this technique. Cardiac functional analysis, aortic flow and valve assessment are most common indications for this sequence. 

·        Cardiac gating /triggering and sequential (acquires one slice at one time over multiple cardiac phases) are automatically selected and can not be turned off. Other than TE and flip angle, all parameters are determined automatically. Chose minimum for TE, and set a flip angle of 40 º to 45 º. The system sets the minimum TR which is allowed by SAR restriction.  Higher flip angle decreases flow artifacts and increases the image contrast with short TR. FIESTA is only useful if a very short TR (TR £ 4 ms) is used. For managing a short TR, system uses a default bandwidth=125 kHz. Since the images are acquired sequentially (no cross-talk), zero spacing is allowed.

·        SSFP is susceptible to field inhomogenities and metal susceptibility artifacts which are especially severe at longer TRs. Shimming before FIESTA improves the homogeneity of the magnetic field, and suppresses artifacts. For optimal shimming, this shim FIESTA sequence is used to confine the shim to a small FOV (~ 12 cm) encompassing just the heart. This sequence must be pre-scanned but does not have to be scanned.

Series 6: 2 Chamber (vertical) Long Axis FIESTA

Long axis 2C views are prescribed from the axial localizer or DIR images at the level of mitral and tricuspid valves. Slices are centered approximately in middle of the mitral and tricuspid valves and angulated. Angulated left ventricle 2C slice should intersect with the left ventricular apex at a lower level. Right ventricle 2C slice is set parallel to the other slice.    

Series 7: 4 Chamber (axial) Long Axis FIESTA

Long axis 4C view is planned on the end-systolic 2C long axis image. The center of the slice is positioned at the lower 3rd of the mitral valve, and then angulated through the apex. For making sure that the left atrium is imaged properly the slice is checked on diastolic 2C long axis image.


Series 8: Short Axis FIESTA

Short axis is prescribed from the long axis 4C and 2C images in diastole, to make sure the entire ventricle is covered. A stack of 10 to 12 slices is positioned perpendicular to the long axis of left ventricle. In patients with dilated right ventricle, such as Tetralogy of Fallot, probably more than 12 slices are necessary.


 Series 9: Phase Contrast (PC)

·        Cine PC is a gradient echo pulse sequence in combination with ECG triggering or gating. This technique is used to assess flow volumes and velocity profiles across valves and shunts.  

·        By using the PC data, one is able to calculate mean spatial velocities; instantaneous flow per phase, flow per cardiac cycle and thus flow volumes in ml/min. This technique accurately assesses high velocities up to 600 cm/s if TE is reduced down to 8 ms. Velocity encoding value (VENC) chosen by the operator should be as close as possible to but still greater than the expected peak systolic velocity for obtaining reliable results. The VENC is described as the maximum velocity that will be properly encoded by the sequence. For patients less than 65 years of age with normal cardiac function, normal range is from 0.1 to 200 cm/s. Typical VENC for between 170 cm/s and 220 cm/s is recommended. For older patients with congestive heart failure, elevated serum creatinine, or aortic aneurismal disease, a VENC of < 100 cm /s is more appropriate. In case of vessel or valve stenosis, higher flow velocities up to 600 cm/s, due to turbulent jets, may be present. If the flow velocity is higher than chosen VENC such as jet flows caused by stenoses, flow direction will be miscoded as opposite to actual flow direction. This results in aliasing phase wraps), and leads to wrong quantification of flow speed and pressure gradients.

·        Mitral Valve PC Flow: Mitral valve flow acquisition is planned on the end-systolic 2C and 4C images. The center of the slice is placed in the middle of mitral valve and angulated parallel to the mitral valve.

·        Tricuspid Valve PC Flow: Tricuspid valve flow acquisition is prescribed on the right ventricle 2C long axis images. This is prescribed from 4C images. The centre of the slice is positioned in the middle of tricuspid valve and slice is angulated through the right ventricle apex. The slice should pass through the right ventricle apex on both end-systolic and end-diastolic 4C images. From 4C and right ventricle 2C images tricuspid valve flow acquisition is planned. The center of the slice is placed in the middle of tricuspid valve and angulated parallel to the tricuspid valve.

·        Pulmonary Arteries PC Flow: Imaging planes through the left pulmonary artery (LPA) and right pulmonary artery (RPA) should be perpendicular to the direction of flow and proximal to the first branching vessel. These planes in adults are usually located 1–1.5 cm distal to the main pulmonary artery (MPA) bifurcation.

·        Ascending Aorta PC Flow: The flow acquisition through the ascending aorta is prescribed from the coronal localizer. Flow measurement is performed perpendicular to the flow direction usually 1.5–2 cm above the aortic valve (pulmonary bifurcation level).

·        MPA PC Flow: For planning the MPA flow acquisition, an additional imaging plan is necessary. This plan is prescribed from sagittal localizer. A few slices parallel to the MPA are obtained. Then, on these images, a slice perpendicular to the MPA is set for PC flow acquisition.

Series 10: Gd-enhanced 3D MRA

Please see instructions at “Thoracic Aorta MRA”

          Series 11: Fast Gradient Echo-Echo Planar Imaging (FGRE-ET)

·        Commonly used sequences for dynamic first-pass studies are interleaved fast gradient echo-echo planar (FGRE-ET) sequence (a gradient-echo pulse sequence that uses an abbreviated echo-planar readout of the signal) and inversion recovery prepared fast gradient echo sequence. This pulse sequence is IR-Prepared to suppress the myocardium, fat signal from pericardial fat pads and anterior chest wall.

·        FGRE-ET Multi-phase obtains myocardial images with high temporal resolution (acquires slices during 1-4 RR intervals at multiple locations). The sequence is repeated 30-60 times per location for observing the enhancement over the time. Number of phases per location is determined by number of heartbeat per minute (BPM). The formula is “BPM/2”. If the BPM is £60, use 30 phases. If the BPM is ³ 120, use 60 phases. The maximum number of slices per acquisition is 64, and maximum number of total images is 512.

·        Enter the typical TE; Min Full, flip angle; 25, ETL; 4, and Bandwidth; 125. TI is calculated by the computer. When 0.75 phase FOV is selected, TI is between 150-175 ms, which is excellent for fat suppression. When phase FOV is selected, TI is longer, which can not suppress the fat. A longer (³4 ms) ETL results in longer TR and cause blurring.

·        NEX is automatically set to 1. If a higher SNR is desired, the other parameters should be changed.

·        FGRE-ET pulse sequence is very susceptible to phase errors that result in ghosting artifacts. System compensates phase errors by using auto echo alignment which is performed for each slice location at the start of each acquisition. It is recommended to run a trial before FGRE-ET sequence. If the blurring is unacceptable, manual echo alignment should be used. 

·        First-pass imaging begins simultaneously with gadolinium injection. Gadolinium (0.1 mmol/kg) is administered by hand as a bolus at a rate of 5 ml/s (e.g. as fast as possible). A 20-ml saline flush followed the contrast injection at the same rate.

·        The data acquired with FGRE-ET pulse sequence can be used for myocardial perfusion reserve establishment by assessing the signal intensity–time curves. Ten minute delayed images are used for evaluating the myocardial viability (viable or irreversible damaged myocardium), and assessment of the infarction extension (subendocardial versus transmural infarction).

 

Billing Instructions

 

Examples of Cardiac MRI Dictation

1- ARVD

Clinical Statement:  Arrhythmia, r/o ARVD

Technique: 1.5 T, phased array coil, axial DIR, sagittal DIR, 2C, 4C, and short axis FIESTA, DIR with fat sat through any suspicious area of fatty infiltration, optional short axis perfusion and delayed enhancement.

Measurements: 

Ascending aorta at RPA:

Aortic Arch:

Descending aorta at RPA

MPA, RPA, LPA

Left Ventricle

EDV:

ESV:

                   Stroke Volume:

                   EF:

                    Mass:

           Right Ventricle

EDV:

                   ESV:

                   Stroke Volume:

                   EF:

                   Mass:

          Findings:

Cardiac size and morphology are normal with no evidence of thinning or fatty infiltration of the right ventricular free wall or septum. Cardiac contraction is normal with no wall motion abnormalities. Delayed enhancement shows no evidence of myocardial scarring. The pericardium has a normal thin appearance. No mediastinal mass or adenopathy.

Impression:

Normal cardiac MRI findings with no evidence of right ventricular dysplasia.

2- Pre-ablation Pulmonary Venous Anatomy

3- Tetralogy of Fallot follow-up

4- Pulmonary HTN

5- Cardiac Mass

6- Pericardial Diseases

7- Anomalous Coronary Artery

8- Ischemic Heart Diseases

 

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