Overview

Indications

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Patient Prep

Series Details

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RENAL ARTERY PROTOCOL

(for GS LX 1.5 Tesla Scanner at 8.45 Software)

Overview

This renal MRA protocol has been refined over 1000ís of cases to make it relatively easy and fast to acquire the data and yet still provide a comprehensive evaluation of the patients suspected of reno-vasculare hypertension. Start with a sagittal locator; spin echo provides high quality blackblood images. SSFSE is slightly faster yet still has acceptable quality. The axial T2 is important to evaluate any mass that might be present. In addition the axial T2 takes about 5 minutes, which provides sufficient time to set-up the 3D Gd MRA. The most important sequence is 3D Gd MRA acquired during the arterial phase of the injection of Gd. Finally 3D PC and cine PC help to evaluate the homodynamic significance of any stenosis identified.
The entire study can be obtained within 45 minutes. However, when first beginning of this exam, we recommended booking patient into 1 hour time slots.


Spin Echo Loc

SSFSE Loc

Axial T2

3D Gd:MRA

3D PC

Delayed (IVP)

Optional Cine PC

IMAGING PARAMETERS

Plane

Sagittal

Sagittal

Axial

Coronal

Axial

Coronal

Axial

Mode

2D

2D

2D

3D

3D

3D

Cine

Pulse Seq

Spin Echo

Spin Echo

Spin Echo

Vasc TOF SPGR

Vasc PC

Vasc TOF SPGR

Vasc PC

Imaging Options

RC, NPW

Fast, SS

Fast, FC

Fast, MPh, Zip2, Smartprep

FC

Fast, Zip2

--

SCAN TIMING

# of Echoes

1

1

1, ETL=8

1

1

1

1

TE

Min Full

180

102

Minimum

--

Minimum

--

TR

325

--

2920

--

18

6

18

Flip Angle

--

--

--

45

25

45

30

Bandwidth

--

31.25

--

31.25

--

31.25

--

ADDITIONAL PARAMETERS (see attached instructions)

SAT

None

None

S,I, FAT

None

None

None

None

ACQUISITION TIMING

Freq

256

256

256

256 (256-512)

256

256

256

Phase

192

256

256

160 (128-256)

192

160

160

NEX

2

--

3

1 (0.5 - 1)

1

1

1

Phase FOV

1

1

1

1

1

1

1

Locs Before Pause

--

0

0

1

--

--

--

Freq DIR

S/I

S/I

R/L

S/I

R/L

S/I

R/L

Auto Center Freq

Peak

Water

Water

Water

Water

Water

Water

Auto Shim

On

On

Off

On

Off

On

On

Contrast

--

--

--

30 (20-50) ml

30 (20-50) ml

30 (20-50) ml

30 (20-50) ml

SCANNING RANGE

FOV

40 (32-48)

40 (32-48)

32 (26-44)

34 (30-44)

28 (26-40)

32 (28-40)

32

Slice Thickness

8.0

9.0

8.0 (8-12)

2.6 (2-4)

2.5 (2-3)

3.0 (2-5)

3.0

Spacing

Interleave

0

2 (2-3)

--

0

0

0

Start - End

L90 - R90

L100-R100

See Graphic

See Graphic

See Graphic

See Graphic

 

# Slices

24

24

18

34 (28-44)

28 (28 - 60)

30 (20-40)

2

 

 

 

 

 

 

 

 

Scan Time (min:sec)

4:39

0:56

4:46

0:30 (0:15-0:58)

7:23

35

4:38

 

Common Indications:

  • Hypertension (especially if difficult to control on multiple meds)
  • Elevated serum creatinine
  • Pre-op mapping of renal artery anatomy
  • Post-op check

Scheduling Guidelines:

MRI & MRA of Abdomen with Gadolinium
45 minute slot any time nurse is available for injecting Gadolinium

First Ask
1) Hypertesion?  How many medications?
2) Renal infufficiency? What is the serum creatinine_________?
3) Prior abdominal surgery?

Patient Preparation:

  • Start intravenous line (20 or 22 gauge iv) and attach SmartSet (TopSpins. Tel: 734-623-6400) before placing patient into the magnet. This avoids the problem of patient movement during iv placement causing the locator to be inaccurate.
  • Oxygen, 2-4 liters/min by nasal canula is essential if patient is short of breath.
  • Valium (5-10mg po) or Xanax (1-2 mg po) if patient is claustrophobic may be given.

Coil: With large patient (>200 lb), body coil is acceptable and easiest to use. It provides a large field-of-view (FOV) with homogeneous signal. Higher SNR is possible with the torso array coil although the signal reception is not as homogeneous because of hot spots near the coil. The torso coil is not useful in obese patients. When using the torso array, rotate 90 degrees for greater S/I coverage and less R/L wrap-around artifact. I have found that the higher SNR of the surface coils allows the standard gadolinium dose to be reduced from 40 to 30 ml in small and average size patients.

Patient Positioning: Supine, feet first.

Landmark: on lower anterior rib margin or just above iliac crest.

 

Series 1: Sagittal Locator

Spin Echo Locator

SSFSE Locator

  • For renal artery imaging sagittal plane is the best orientation for the locator. You may consider landmarking high and using a large FOV (48cm) to also cover the thoracic aorta in case the patient is suspected of coarctation, thoracic aneurysm or dissection.
  • When using the spin echo sequence with interleaved acquisition (as recommended) half of the images are reconstructed half way through the scan. These images can be used to set-up series 2 while you are waiting for series 1 to finish.
  • Breath-hold fast multiplanar spoiled gradient echo (FMPSPGR) is the fastest sequence but is not recommended because it does not show the abdominal aorta well especially if there is any trouble with breath holding.
  • Single shot fast spin echo (SSFSE) is also a good sequence but it will not show the thoracic component of the aorta and it is not available on all scanners. It can be performed without breath-holding although breath-holding is preferred. Use 8 skip 0, TE=180 and do not use fatsat.

Series 2: Axial T2 Fat Sat

This sequence helps to evaluate renal masses to determine if they are simple benign cysts or more suspicious for malignancy. It also keeps the scanner busy while you are setting up the 3D Gd MRA (series 3). If the patient has a regular respiratory rhythm, better image quality is possible with respiratory triggering. For respiratory triggering use:

  • RR intervals = 2-3;
  • trigger point = 20%;
  • trigger window =20%;
  • inter-sequence delay = minimum;

Scanning Range for Axial T2

T2 weighted image shows benign cysts

Series 3: Coronal 3D Gd:MRA

This is the main sequence for showing the aorto-iliac and renal artery anatomy. It is essential to have perfect gadolinium infusion timing so that central k-space data will be acquired during the arterial phase of the bolus. Use MR SmartPrep to ensure synchronization of central k-space with the contrast bolus peak.

  • ADDITIONAL PARAMETERS
    • Vascular Screen:
      • Projection Images: 0
      • Collapse: on
    • User CVs Screen:
      • Max Monitor Period&: 35 (30-60)
      • Image Acq. Delay: 6 (5-10)
      • SPECIAL: off
      • Eliptical Centric: on

Use longer Max Monitor Period and Image Acq. Delay in patients who have slow flow including patients older than 70, patients with congestive heart failure or patients with abdominal aortic aneurysm.

    • Multi Phase Screen:
      • Phases per Location: 2
      • Delay After Acq.: Minimum (?)

Positioning for Coronal Volume and Tracker

Coronal 3D Gd MRA

  • To determine where to position the 3D Volume, first find the celiac and SMA, the right and left kidneys.
  • Place the tracker on the aorta at the level of the SMA. I prefer to place the tracker on a sagittal image of the aorta (make the tracker 7-10 cm long and 30-40 mm wide and position on aorta completely below SMA). However it is sometimes difficult to find the aorta on a sagittal image and occasionally it is inadvertently placed on the IVC with disastrous results. Fot these reasons, some users find it easier to place the tracker using an axial image. For axial image placement, make the tracker 3-4 cm long by 30-40 cm wide and place on a slice of aorta well below renal arteries.
  • Position 3D volume with
    • top: 3-4 cm above celiac axis
    • posterior: border at posterior margin of kidneys or at least sufficently posterior to include >1/2 of each kidney
    • anterior: border anterior to aorta and anterior to SMA
    • Make sure the acquisition time is short enough so that the patient can suspend breathing for the entire scan. To make the scan time shorter consider
      • Decreasing matrix to 128
      • Decreasing number of slices and increase slice thickness
      • Covering only the essential anatomy
      • Decreasing NEX to 0.5 but be careful because 0.5 NEX produces more k-space artifact
    • Use "fallback" for optimal right-left alignment
    • Check "#of Locs Before Pause" to be sure it is set to 1.
    • Place the patientís arms over the head or on cushions to get them out from along side the patient where they will wrap around into the imaging volume.
    • Test the iv with saline and then fill the SmartSet with Gd contrast (about 5 ml).
    • Instruct the patient on when to suspend breathing: "This is the most important scan. You will need to hold your breath for 1/2 of the scan, the second half. You can tell when to hold your breath by the change in the sound. Just to be sure there is no confusion, I will squeeze your arm when the sound changes so that you will know exactly when to take in a deep breath and hold it."
    • Start scan: Do not begin injecting until the clock begins to count down: about 15 seconds after starting the scan.
    • When the clock begins counting down, start injecting at about 1-2 cc/sec ( as fast as you can, for a person of average strength using Gd: DTPA with a 20 gauge iv).
    • When the sound changes (bolus detected), signal the patient to Breath Hold by squeezing the patient's arm.
    • When Gd infusion is complete, flush with 20 cc normal saline.
    • At the end of the arterial phase scan, have the patient take 3-4 quick breaths and then scan again to catch the portal venous phase.

Series 4: Axial 3D Phase Contrast

This sequence provides another high resolution look at the renal arteries and helps in the evaluation of the hemodynamic significance of any renal artery lesions that are present.

Scanning Range for 3D PC

Axial 3D Phase Contrast

  • ADDITIONAL PARAMETERS
    • Vascular Screen:
      • Projection: 0
      • Flow Recon Type: Phase Diff
      • Velocity Encoding: 40
      • Acq. Flow: Direction ALL
      • Collapse: on
      • Flow Analysis: off
      • Additional Flow Images: none
  • Set the Venc = 40cm/sec as the default. Lower it to 30 cm/sec in patients who also have renal insufficiency with serum creatinine >2.0 mg/dl, in patients older than 70 years of age, patients with AAA or CHF. In patients with more than one of these factors or serum creatinine > 2.5 mg/dl reduce the Venc to 25 cm/sec. In young healthy hypertensive patients, raise the Venc to 50 cm/sec and in athletes raise it to 60 cm/sec to avoid aliasing.
  • When positioning the 3D volume, remember that the position of the kidneys will be lower during the breathhold in inspiration for the 3D Gd:MRA. Anticipate that the kidney will move 1-2 cm superiorly during free breathing for the 3D PC.
  • It is acceptable to have the FOV slightly smaller than the right-left dimension of the patientís thorax since phase is mapped A-P and frequency is R-L.
  • If there are accessory renal arteries, than instead of 28 slices that each 2.5 mm thick, change to 60 slices each 2.0 mm thick with 128 phase encoding steps in order to cover more S-I distance.

Series 5: Delayed 3D Gd Excretory Phase:

Series 6: Cine PC

Filming Instructions

Routinely, the 3D gadolinium images are processed on the computer workstation. A montage 12 on 1 sheet or two 6 on 1 sheets are created including:

  • The overall 3D view from the arterial phase (1 image)
  • each renal artery in the coronal plane (2-3 images)
  • each renal artery in the axial plane (1 image)
  • Sagittal celiac and SMA origins (1 image)
  • Length of each kidney from the sagittal locator or from the 3D Gd:MRA sequence (venous phase) (2 images)
  • 3D PC MIP of both renal arteries (1-2 images)
  • Oblique magnified MIPs of iliac arteries (2 images)
  • MIP of excretory phase
  • Any additional pertinent images to show pathology
  • The 3D PC images are printed from a SET BATCH-MOVIE LOOP option available on the computer workstation. From a coronal 3D image of the entire imaging volume, overlapping MIP images are created. The FOV is set to 18 cm.

Billing:

  • MRI of Abdomen 74181
  • MRA of Abdomen 4185

ICD9 Codes:

441.00

Dissecting aneurysm of aorta, unspecified site

441.02

Dissecting of aorta (ruptured), abdominal

441.03

Disssecting aneurysm of aorta (ruptured), thoracoabdominal

441.4

Abdominal aneurysm, without mention of rupture

441.7

Thoracoabdominal aneurysm, without mention of rupture

441.9

Aortic aneurysm of unspecified site without mention of rupture

442.1

Otheraneurysm of renal artery

442.2

Other aneurysm of iliac artery

442.83

Aneurysm of splenic artery

442.84

Aneurysm of other visceral artery

444.0

Arterial embolism and thrombosis of abdominal aorta

444.81

Arterial embolism and thrombosis of iliac artery

Renal MRA Report Template

Re:

Exam: Renal MRA

Exam Date:

 

Clinical Statement:

 

Technique:

Sagittal T1 of abdomen and pelvis

Axial T2 of kidneys

Coronal 3D Gd:MRA of abdominal aorta and renal arteries

Axial 3D phase contrast MRA post-gadolinium

3D MRA data was reconstructed on a computer workstation

Findings:

Abdominal aorta:

Celiac axis:

Superior mesenteric A.

Inferior mesenteric A.

 

The right kidney measure ? cm in length. No right renal masses are identified.

There is a single right renal artery which is ? .

The left kidney measures ? cm in length. No left renal masses are identified.

There is a single left renal artery which is ? .

 

Right common iliac artery:

Right external iliac artery:

Right internal iliac artery:

 

Left common iliac artery:

left external iliac artery:

Left internal iliac artery:

 

No abdominal masses or retroperitoneal adenopathy is identified.

 

Impression:

 

Accuracy of 3D Gd:MRA for diagnosing Renal Artery for Stenosis.

Investigator

Year

Number of Patients

Technique

Sensitivity

Specificity

Degree of Stenosis

Prince

1995

19

3D Gd

100%

93%

75%

Grist

1996

35

3D Gd

89%

95%

>55%

Holland

1996

63

3D Gd

100%

100%

>50%

Snidow

1996

47

3D Gd

100%

89%

NA

Steffens

1997

50

3D Gd

96%

95%

NA

Hany

1997

39

 

93%

98%

>50%

De Cobelli

1997

55

3D Gd

100%

97%

>50%

Rieumont

1997

30

3D Gd

100%

71%

>50%

Hany

1998

103

3D Gd

93%

90%

NA

Bakker

1998

50

3D Gd

97%

92%

>50%

Thornton

1999

62

3D Gd

88%

98%

 

Schoenberg

1999

26

3D Gd

94-100%

96-100%

 

Miller

1999

32

3D PC

93%

81%

 

Cambria

1999

25

3D Gd + PC

97%

100%

 

Thornton

1999

42

3D Gd

100%

98%

 

Ghantous

1999

12

3D Gd

---

100%

 

Marchand

2000

 

3D Gd

88-100%

71-100%

 

Shetty

2000

51

3D Gd

96%

92%

 

Winterer

2000

23

3D Gd

100%

98%

 

Weishaupt

2000

20

blood pool 3D

82%

98%

 

Bongers

2000

43

3D Gd

100%

94%

 

Volk

2000

40

time resolved 3D Gd

93%

83%

 

Oberholzer

2000

23

3D Gd at 1T

96%

97%

 

Korst

2000

38

3D Gd

100%

85%

 

De Corbelli

2000

45

3D Gd

94%

93%

 

Example

Case 1

More examples