RENAL ARTERY PROTOCOL
(for GS LX 1.5 Tesla Scanner at 8.45 Software)
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IMAGING PARAMETERS |
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Plane |
Sagittal |
Sagittal |
Axial |
Coronal |
Axial |
Coronal |
Axial |
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Mode |
2D |
2D |
2D |
3D |
3D |
3D |
Cine |
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Pulse Seq |
Spin Echo |
Spin Echo |
Spin Echo |
Vasc TOF SPGR |
Vasc PC |
Vasc TOF SPGR |
Vasc PC |
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Imaging Options |
RC, NPW |
Fast, SS |
Fast, FC |
Fast, MPh, Zip2, Smartprep |
FC |
Fast, Zip2 |
-- |
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SCAN TIMING |
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# of Echoes |
1 |
1 |
1, ETL=8 |
1 |
1 |
1 |
1 |
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TE |
Min Full |
180 |
102 |
Minimum |
-- |
Minimum |
-- |
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TR |
325 |
-- |
2920 |
-- |
18 |
6 |
18 |
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Flip Angle |
-- |
-- |
-- |
45 |
25 |
45 |
30 |
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Bandwidth |
-- |
31.25 |
-- |
31.25 |
-- |
31.25 |
-- |
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ADDITIONAL PARAMETERS (see attached instructions) |
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SAT |
None |
None |
S,I, FAT |
None |
None |
None |
None |
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ACQUISITION TIMING |
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Freq |
256 |
256 |
256 |
256 (256-512) |
256 |
256 |
256 |
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Phase |
192 |
256 |
256 |
160 (128-256) |
192 |
160 |
160 |
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NEX |
2 |
-- |
3 |
1 (0.5 - 1) |
1 |
1 |
1 |
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Phase FOV |
1 |
1 |
1 |
1 |
1 |
1 |
1 |
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Locs Before Pause |
-- |
0 |
0 |
1 |
-- |
-- |
-- |
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Freq DIR |
S/I |
S/I |
R/L |
S/I |
R/L |
S/I |
R/L |
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Peak |
Water |
Water |
Water |
Water |
Water |
Water |
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Auto Shim |
On |
On |
Off |
On |
Off |
On |
On |
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Contrast |
-- |
-- |
-- |
30 (20-50) ml |
30 (20-50) ml |
30 (20-50) ml |
30 (20-50) ml |
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SCANNING RANGE |
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FOV |
40 (32-48) |
40 (32-48) |
32 (26-44) |
34 (30-44) |
28 (26-40) |
32 (28-40) |
32 |
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Slice Thickness |
8.0 |
9.0 |
8.0 (8-12) |
2.6 (2-4) |
2.5 (2-3) |
3.0 (2-5) |
3.0 |
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Spacing |
Interleave |
0 |
2 (2-3) |
-- |
0 |
0 |
0 |
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Start - End |
L90 - R90 |
L100-R100 |
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# Slices |
24 |
24 |
18 |
34 (28-44) |
28 (28 - 60) |
30 (20-40) |
2 |
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Scan Time (min:sec) |
4:39 |
0:56 |
4:46 |
0:30 (0:15-0:58) |
7:23 |
35 |
4:38 |
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.
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Spin Echo Locator |
SSFSE Locator |
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- 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.
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;
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Scanning Range for Axial T2 |
T2 weighted image shows benign cysts |
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 (?)
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Positioning for Coronal Volume and Tracker |
Coronal 3D Gd MRA |
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- 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 patient’s 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.
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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 patient’s 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:
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.
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Re:
Exam:
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.
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Investigator |
Year |
Number of Patients |
Technique |
Sensitivity |
Specificity |
Degree of Stenosis |
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Prince |
1995 |
19 |
3D Gd |
100% |
93% |
75% |
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Grist |
1996 |
35 |
3D Gd |
89% |
95% |
>55% |
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1996 |
63 |
3D Gd |
100% |
100% |
>50% |
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Snidow |
1996 |
47 |
3D Gd |
100% |
89% |
NA |
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Steffens |
1997 |
50 |
3D Gd |
96% |
95% |
NA |
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Hany |
1997 |
39 |
|
93% |
98% |
>50% |
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De Cobelli |
1997 |
55 |
3D Gd |
100% |
97% |
>50% |
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Rieumont |
1997 |
30 |
3D Gd |
100% |
71% |
>50% |
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Hany |
1998 |
103 |
3D Gd |
93% |
90% |
NA |
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Bakker |
1998 |
50 |
3D Gd |
97% |
92% |
>50% |
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1999 |
62 |
3D Gd |
88% |
98% |
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Schoenberg |
1999 |
26 |
3D Gd |
94-100% |
96-100% |
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Miller |
1999 |
32 |
3D PC |
93% |
81% |
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1999 |
25 |
3D Gd + PC |
97% |
100% |
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1999 |
42 |
3D Gd |
100% |
98% |
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Ghantous |
1999 |
12 |
3D Gd |
--- |
100% |
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Marchand |
2000 |
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3D Gd |
88-100% |
71-100% |
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Shetty |
2000 |
51 |
3D Gd |
96% |
92% |
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Winterer |
2000 |
23 |
3D Gd |
100% |
98% |
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Weishaupt |
2000 |
20 |
blood pool 3D |
82% |
98% |
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Bongers |
2000 |
43 |
3D Gd |
100% |
94% |
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Volk |
2000 |
40 |
time resolved 3D Gd |
93% |
83% |
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Oberholzer |
2000 |
23 |
3D Gd at 1T |
96% |
97% |
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Korst |
2000 |
38 |
3D Gd |
100% |
85% |
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De Corbelli |
2000 |
45 |
3D Gd |
94% |
93% |
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Example