RENAL ARTERY PROTOCOL
(for GE 1.5 Tesla Scanner at 14 Software, 6/27/2008)
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IMAGING PARAMETERS |
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Plane |
3-Plane | Axial |
Coronal |
Axial |
Coronal |
Axial |
Oblique |
Sagittal |
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Mode |
2D |
Calib |
2D |
2D |
3D |
3D |
3D |
2D |
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Pulse Seq |
Fiesta | Gradient Echo |
Spin Echo |
Spin Echo |
Vasc TOF SPGR |
Vasc PC |
Vasc TOF SPGR |
Vasc PC |
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Imaging Options |
Seq, Fast |
Fast, Calib |
Fast, ZIP512, SS |
Fast, ZIP512, FC |
Fast, MPh, ZIP4, Smartprep, Asset |
FC |
Fast, ZIP512, ZIP2, Asset |
FC, Gat, Seq, Fast |
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SCAN TIMING |
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# of Echoes |
1 |
-- |
1 |
1 |
1 |
1 |
1 |
1 |
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TE |
Minimum |
-- |
180 |
90 |
Minimum |
-- |
Minimum |
Minimum |
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TR |
-- |
-- | Minimum |
Minimum |
-- |
18 |
-- |
-- |
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Flip Angle |
30 |
-- |
-- |
-- |
35 |
25 |
60 |
30 |
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Bandwidth |
100 |
-- |
31.25 |
31.25 |
62.50 |
15.63 |
62.50 |
31.25 |
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ADDITIONAL PARAMETERS (see attached instructions) |
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SAT |
None |
None |
None |
None |
None |
None |
None |
None |
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ACQUISITION TIMING |
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Freq |
256 |
-- | 384 |
256 |
512 |
256 |
512 |
256 |
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Phase |
160 |
-- |
256 |
256 |
192 (128 - 256) |
160 |
192 |
128 |
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NEX |
1 |
-- |
-- |
-- |
1 (0.5 - 1) |
1 |
1 |
1 |
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Phase FOV |
1 |
-- |
1 |
1 |
0.80 (0.5 - 1) |
1 |
1 |
1 |
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Acq/Locs Before Pause |
-- |
-- |
10 |
0 |
1 |
-- |
-- |
-- |
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Freq DIR |
Unswap |
R/L |
S/I |
R/L |
S/I |
R/L |
S/I |
S/I |
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Shim |
Auto |
Auto |
Auto |
Auto |
Auto |
Auto |
Auto |
Auto |
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Contrast |
-- |
-- |
-- |
-- |
20 (10-30) ml |
Yes |
Yes |
Yes |
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SCANNING RANGE |
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FOV |
48 |
48 |
44 (40-48) |
32 (26-44) |
38 (30 - 48) |
30 (20-36) |
38 (28-44) |
26 |
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Slice Thickness |
8.0 |
15 |
8.0 |
8.0 (8-12) |
2.4 (2-4) |
2.5 (2-3) |
3.0 (2-5) |
2.5 |
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Spacing |
2 | -- |
0 |
2 (2-3) |
-- |
0 |
0 |
0 |
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Start - End |
-- |
I300-S300 |
L70-A80 |
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# Slices |
10 |
41 |
20 |
30-50 |
40 (30-50) |
30 (28 - 40) |
40 (30-50) |
2 |
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Scan Time (min:sec) |
0:16 |
0:13 |
0:28 |
1 sec/slice |
19 sec/acq |
6:32 |
0:23 |
34 sec/slice |
MRI & MRA of Abdomen with Gadolinium Ask if there is renal infufficiency. What is the serum creatinine? If estimated GFR is less than 30 ml/minute we will first to a non-contrast MRA and if that is not diagnositic we will need to consent the patient for the risk of NSF before giving Gadolinium. Note that in our experience with 70,000 cases of single dose Gadolinium administration we have not had a single case of NSF so the risk at the dose we use is very low. |
Patient Preparation:
- Start intravenous line (20 or 22 gauge iv) and attach SmartSet 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. This has the advantage of relaxing the patient and reducing cardiac output so the Gadolinium bolus will be more concentrated and linger longer in the arteries for higher quality study. However the patient will need to be accompanied by someone who can ensure the patient gets home safely which the effect of sedation is wearing off.
Coil: Body phased array coil positioned to cover abdomen and pelvis
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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- Non-gated SSFP (FIESTA) is a great localizer because it shows the vessels with bright signal that is easy to see. It may however be degraded in situations where the field is not homogeneous (e.g. metal in the patient) which can easily happen over the large field of view.
- Single shot fast spin echo (SSFSE) is also a good localizer sequence which is not affected by field homogeneity issues. It can be performed without breath-holding although breath-holding is preferred. Use 8 skip 0, TE=180 and do not use fatsat.
- Make sure to cover from well above the 48 cm FOV of the coil to well below the 48cm FOV of the coil. Axial is the best plane for calibration scans
- If the calibration does not cover the entire FOV then some of the image data will not be able to be recontructed!
Series 3 and 4: Axial and Coronal T2
These sequences helps to evaluate renal masses to determine if they are simple benign cysts or more suspicious for malignancy. It also identifies hydronephrosis.
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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 or Fluoro-triggering to ensure synchronization of central k-space with the contrast bolus peak.
- ADDITIONAL PARAMETERS
- ASSET
- 1.75Ph
- Multi Phase Screen:
- Phases per Location: 2
- Delay After Acq.: Minimum
- Image Enhance
- None
- User CVs Screen:
- Max Monitor Period&: 40 (30-60)
- Image Acq. Delay: 5 (4-10)
- Turbo Mode: 2
- Reverse Elliptical Centric: 0
- Eliptical Centric: 2
- Centric:0
- Reverse Centric: 0
- Slice resolution: 100
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.
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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, to include aorta and kidneys as well as the proximal 2cm of celiac and SMA. It is better to miss the posterior kidney than to miss the aorta. However if there is a large abdominal aortic aneurysm, it is not necessary to completely image the entire aneurysm.
- For MR SmartPrep, place the tracker on the aorta at the level of the SMA. I prefer to place the tracker on a axial image of the aorta. Make the tracker 2-3 cm long and 30 mm wide and position on aorta at the level of Celiac and SMA.
- For fluoro-triggering (instead of smartprep) it is useful to allign the fluoro image on the aorta including lung bases so that you can watch Gd enter right heart, then pulmonary arteries, then left ventricle and finally aorta. Hit the "Go 3D" button when you see Gd in the abdominal aorta. If the flow is really slow (e.g. > 20 seconds to reach the abdominal aorta) then let the aorta fill out a little bit with Gd before "Go 3D".
- 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
- ASSET x 2
- 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
- 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."
- For smart prep start scan but 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 stops (bolus detected), signal the patient to Breath Hold by squeezing the patient's arm and yelling "breath in and hold your breath".
- 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 6: 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 Images: 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 coverage can be increased by increasing slice thickness to 3mm but if further coverage is needed, add more slices.
Series 7: Delayed 3D Gd Excretory Phase
Routinely, the 3D gadolinium images are processed on the computer workstation to obtain the following MIPs:
- each renal artery in the coronal plane (2-3 images)
- each renal artery in the axial plane (1 image)
- Sagittal celiac and SMA origins (2 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 (4 images)
- overall MIP of entire 3D volume with extraneous soft tissue removed (1 image)
- 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: MRI and MRA of the abdomen without and with contrast was obtained at 1.5 Tesla using a body array coil,
3-Plane SSFP (FIESTA) nongated localizer of abdomen and pelvis
Coronal and Axial SSFSE T2
Coronal 3D Gd:MRA of abdominal aorta, iliac and renal arteries
Axial 3D phase contrast MRA of renal arteries post-gadolinium
Coronal 3D spoiled gradient echo post Gd for excretory phase of Gd
3D MRA data was reconstructed on a computer workstation
The type of gadolinium was___________ and the dose was ____ml.
Findings:
Abdominal aorta:
Celiac axis:
SMA
IMA
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 ? .
There is symmetrical (assymetrical) excretion of Gd by the kidneys into the collecting systems and ureters and bladder.
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 |
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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