How to Learn MRI - MRprotocols.com

How to Learn MRI An Illustrated Workbook

Exercise 3: Scanning a Human Using a Protocol Teaching Points: • How to run a pre-programmed protocol. • How to scan the knee.

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Exercise 3: Scanning a Human using a Protocol You have mastered the art of scanning the phantom, now it is time to move on to a live person. The main goal of this exercise is to show you how to use a protocol to scan a patient. What’s a protocol? A protocol is a set of scans designed to image a specific anatomy. Protocols usually consist of scans that show different views and weightings. To begin this exercise, you need to first recruit an MRI compatible friend that has some knee pain and would like a free MR scan.

Exercise 3a—Patient Prep The following should be done every time you scan a volunteer/patient/research subject.

STEP 1: Have your Friend Sign the Appropriate Forms If you are scanning a patient for research you will have to have them sign a consent form to participate in the study as well as an IRB form. Here we are still scanning for QA though, so they do not have to sign the IRB forms this time. You should have them fill out the safety screening form and proceed on to step 2.

STEP 2: Safety Screen your Friend Begin safety screening your friend to see if they are MR compatible by reviewing their signed safety screening form (exercise 2b). It is important that you verbally review each item on the form with them to make sure that nothing was overlooked. Be sure that they have no metal in them (i.e. aneurysm clips, pacemakers, or any other metallic implanted device), that they do not have any scraps of metal in their eyes, and that they have removed all credit cards, cell phones, and metal, before entering the magnet room.

STEP 3: Have your Friend Change Clothes Although this is only needed if your friend is wearing clothes containing metal, it is a good habit to have them change because sometimes there is metal that you are not aware of. Give them a clean gown and direct them to a changing room. Also instruct them where they can safely leave their belongings during the scan, such as credit cards, cell phone, jewlery, etc. Gold and sliver wedding rings are ok to leave on beacuse they are nonmagnetic. Who wants to be responsible for loosing a friend’s wedding ring?

STEP 4: Prepare the Scanner for your Friend Place a clean disposable sheet down on the scanner bed. Also, put a new disposable pillowcase on the pillow and leave it on the scanner bed.

STEP 5: Enter Relevant Information in the Computer Go to the computer and create a new patient. Again, don’t worry about accession or patient number. Type in your friend’s name and relevant information. Be sure to include your friend’s weight . Weight is used to determine the maximum RF exposure and if weight is too low, FDA regulations may not allow sufficent RF to scan. For operator, type in your initials, and for exam description enter QA-Knee Exam.

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Exercise 3b—Scanning the Knee with a Protocol STEP 1: Prepare the Knee Coil in the Scanner Room

Fig 3.1 Knee coil positioning

Find the knee coil in the scanner room and place it on the table approximately where your friend’s knee will be when they are lying down. Be sure to orient it so that the knee coil is on the same side of the table as will be the knee you want to scan, with the patient going in feet first.

STEP 2: Place your Friend on the Scanner Table in the Home Position

Fig 3.2 Centering the patella

First, lower the table by using the down pedal as noted in exercise 2a. Now, have your friend get on the table and lay down with their ailing knee in the coil. The knee should be placed such that the foot is pointing slightly outward toward the wall of the room (figure 3.1). This is so that the cruciate ligaments will be under tension making them more visible in the image. Also, the inferior edge of the patella should be in the center of the coil, when the patient is laying down (figure 3.2). You will have to support the opposite knee using foam padding, and ensure that the knee in the coil will not move using foam shims (figure 3.3). Next, place a piece of foam under your friend’s feet to let them rest comfortably while in the coil. Once everything is set with the coil, ensure your patient’s comfort. Ask them if they want a blanket and if they want the fan and lights on in the scanner, and adjust accordingly. Be sure to give them ear plugs. Give them the squeeze-ball so they can let you know if they are in distress and want to come out of the scanner. Note: It is important during this step to get a sense of the patient’s comfort within the scanner. Try and see by their gestures and what they say, if they seem nervous. This may mean that they are claustrophobic and need more attention while in the scanner. Be comforting during this stage, and let them know that you will be close by.

Fig 3.3 Cushion support

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Fig 3.4 Protocol menu

STEP 3: Landmark the Knee

Patient Protocols

Now raise the table up to the scanner level and plug in the coil to the scanner. Turn the align-on lights and landmark the knee in the center of the coil at the inferior edge of the patella. Shut off the align on lights—this is especially important if you are using a scanner with laser alignment, since you don’t want your patient accidentally looking into the laser as they advance to scan. Then press advance to scan and leave the MRI room, shutting the door behind you.

Site

Head Neck/Cervical Chest Thoracic Upper Extremities Abodomen/Lumbar Pelvis LowerExtremities Other Protocol

STEP4: Choose Protocol Go back to the computer. For this exercise, we are going to be using a knee protocol. This is a series of scans that has already been setup for you. On the computer screen, choose Lower Extremity from the protocol menu (figure 3.4) . Choose the KNEE (ROUTINE) protocol from the popup menu (figure 3.5). A series of scans will appear in the Rx manager window (figure 3.6). Protocols are generally setup with the following basic structure. First, there is a three-plane localizer so you can see the anatomy in the three normal planes. Next, are the large FOV images, and finally the smaller FOV images. Also, usually the most important sequences are put first in the protocol, since patients usually tire as the scan wears on, and at any moment can demand to be taken out of the scanner. Be sure to shut off automatic scan sending to the central computer before scanning by clicking the Scan Modes on the Rx Manager and Turning off Auto Transfer. Patient Information

Patient Protocols

Patient Protocols

Site

Accession 0000 Number

Patient Position Supine Head

Patient ID 0000

Coil Chest Thoracic Upper Extremities

Auto Start

Rx Manager

Patient Entry Feet First

Neck/Cervical

Patient Name MR PLASTIC

HEAD

Series MY THIRD SCAN Description

Abodomen/Lumbar

Protocols L1-ANKLE (routine) 4.07 L2 - FOOT (routine) 4.07 L3 - FOOT ( ) 4.07 Full L4 - KNEE (routine) 4.07 Info L5 - MRV LEGS - DR.P 4.06 L6 - KNEE (ROUTINE) L7 - BOLUS CHASE 9.07 L8 - BOLUS CHASE 10.07 L9 - TRICKS

Series

Plane 3-PLANE

Pelvis

LowerExtremities

Protocol

Pulse Seq Gradient Echo

1.3 PLANE LOCImaging Seq, Fast Other Options 2. Calibration Psd Name 3. AXL PD 4. SAG PD FREQ A/P Protocol 5. SAG PD FSAT FREQ A/P 6. COR PD FSAT FREQ R/L 7. COR PD FREQ R/L

Mode 2D Grad Mode

HIS/RIS

Scan Modes

Gating Control

New Series

End Exam

State # Series Description

SCND 1 SCND 2 SCND 3 SCND 4 SCND 5 SCND 6 ACT 7

3 PLANE LOC Calibration AXL PD SAG PD FREQ SAG PD FSAT COR PD FSAT COR PD FREQ

Selection site/lower/KNEE(ROUTINE)/ View Edit

Accept

Backup

Download Save as Rx Protocol

Fig 3.5 Protocol Pop-up menu

Fig 3.6 Rx Manager window

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STEP 5: Three-Plane Localizer We will start with the 3-plane localizer. Before choosing the localizer, be sure that the current coil is the knee coil. If not change the coil to the currently connected coil and Apply All. Select the 3-plane from the RX manager and hit View Edit. Then Save Series, Download and Scan. During the exam, intermittently talk to your friend through the microphone to open up a line of contact with them. Note: You can adjust the volume on the speaker and the microphone, so you can hear the patient better. Just don’t turn this too low though, or else you won’t hear the patient. Also, sometimes during the scan, the RF noises come out very loud on the speaker. There is usually a small pad you can put over the speaker to muffle these noises. Before each scan, you should make a habit of telling the patient over the microphone, what the scan is, and what its duration will be. You have to wait for the three-plane to finish before you can go on to graphically prescribe the rest of the scans. 605270 left @ 256 2 185786 left @ 5122

March 4 7:23 PM

Disk 32% full The patient comfort level has returned to normal

Patient Information

Patient Protocols

Site

Accession 0000 Number

Patient Position

Patient ID 0000

Patient Entry

Head

HD TRknee PA

Coil Chest Thoracic

Series Description

Upper Extremities

Auto Start

3 PLANE LOC

Abodomen/Lumbar Plane

iLinq

Axial

LowerExtremities

Imaging Options

Protocol Sent: 4236/10 (DYNACAD61)

Rx Manager Scan Modes New Series

# of TE(s) per scan

Gating Control

TE2

Additional Parameters

TR


Max

1.0

2.0

1.0

Inv. Time TI2 Flip Angle

Graphic RX

1.5

6000.0

0

100000

50

4000

1

90

0.0

Freq DIR Unswap

256

Phase

126

Flow Comp Direction

NEX

1.00

Shim

Users CVs Screen

1.00

Contrast

View Edit Download Save as Rx Protocol Auto Scan

Auto Step

Save Series

# of Acqs.: 1

dB/dt: First Level SAR: First Level Research Operations...

Fig 3.7 Three plane localizer selection

ml

Amf Agent

Scanning Range

Slice Thickness:

250.0 250.0

24.0

Min.

Max

9

48

3.0

S/I

Max # of slices: 32

Rel. SNR(%): 100 (Drive FPS:< 1

P/A Center

0.0

170.0

A10.0

End

1.0

1.0

1.0

9

9

9

# of Slices:

Spacing

L/R Center

Start

Actual End Rx Scan Time 0:22

Auto

Phase Correct

Acqs Before Pause

FOV

Bandwidth2

Image Enhance

1.0

5.0

2.0

OFF

Aquisition Timing Freq

Phase FOV

Echo Train Length Bandwidth

HIS/RIS

Protocol KNEE (routine) 4.07/1

Min.

1.5

TE

End Exam

3 PLANE LOC AXL PD SAG PD FSAT SAG PD FREQ COR PD FSAT COR PD FREQ

1

Seq. Fast

Psd Name

Full Info

Scan Timing

2D

Grad Mode

Pulse Seq Gradient Echo

Other

Removed Series 4234/9

Mode

3-plane

Pelvis

4237/4/26 28/28

ACT NEW NEW NEW NEW NEW

Feet First

Neck/Cervical

Patient Name MY FRIEND

Idle

Supine

Est. SAR: 0.6 Peak SAR: 1.6

Table Delta

Reset Values

Total # slices: 32

Exam Series 0000, Series 1 - scanned Scan Time 0:22 dB/dt: 100%

0.00

dB/dt: First Level SAR: First Level

Scan Auto Prescan

Manual Prescan

Prep Scan

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Fig 3.8 Three plane localizer

STEP 6—Calibration Scan Some knee protocols have a calibration scan that is part of the routine exam. The purpose of this scan is twofold. One is to provide a homogenous image over all coils. Since one MR image is produced from the various coil images taken from the coil array, the final image is sensitive to the proximity of the coils to the anatomy they are scanning. Each coil contributes a coil image that has high intensity in locations closer to the coil and less intensity in locations further from the coil. When the coil images are assembled into the final image, these variations can carry through. The calibration helps to smooth out these variations over all coils to provide a more homogenous image. The second purpose of the calibration scan is to provide coil sensitivity maps that can be used for parallel imaging algorithms such as GE’s ASSET (which is an implementation of SENSE). To setup the calibration scan, highlight it in the RX manager and select View Edit. It should open in the graphic RX screen, but if it doesn’t click on the graphic RX button. The goal for this scan is to prescribe the slices to be far above and below the field of view. Do this by pulling down the slices, extending them, and then pushing them way up beyond the field of view. Do the same for the bottom part of the slices. You only need to do this in one plane—the others will adjust accordingly. Now click save series, download, and scan, begin the calibration scan.

Fig 3.9 Calibration scan

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Fig 3.10 Axial pd

STEP 7—Axial Proton Density Scan Once the calibration scan is done, you can then go to the Rx manager and View Edit the axial PD scan. Adjust the localizer to 3 slices in the graphic Rx window (fig 3.11) Once the slices are arranged for the axial scan on the planes in the screen, click Save series, Download, and Scan. Remember to tell your patient the length of the scan! Go on to Step 8 while the current scan is running.

Fig 3.11 Graphic Rx for axial pd X

Graphic Rx Erase Selected Erase All Reset Center

Fallback to SO

Loc Ref Lines

Report Cursor

Update All

Keep W/L

2 3 1

3 1

2

Display Normal 1.0 ZOOM

Copy Rx... Select Series Select image SAT

...

Scan Plane: Oblique

Graphic Rx

*

FOV: 14.0

Localized image - 2 , 5

Phase FOV Fat

Accel. Bar:

Slice

Water

Freq DIR: A/P Acqs Before

Shim FOV:

Pause:

Shime Vol

TR: 3325.0

Numbe of 1 Radial Slices CW CCW

Start:

R76.7

P5.8

I37.8

End:

R70.0

P9.4

S36.8

Rx Scan Time 3:13 # of Acqs.: 1


Minimum TR: 134.0

Hide Shim

Partial Radial 0 Spacing

Save Series

0.0

Spacing

SPECIAL

Radial Direction

3.0

Thickness:

Fat Classic

Max # of slices: 3

# of Slices

3


Total # slices: 3

Est. SAR: 0.0 Peak SAR: 2.8 Avg. Coil SAR: 1.1

dB/dt: First Level SAR: First Level Reset Values

Exam Series 0000, Series 1 - prescanning. Scan Time 5:36 dB/dt: 100%

Scan Auto Prescan

Manual Prescan

Prep Scan

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Number of Acquisitions and Why it Matters The number of acquisitions plays an important role in scan length—it can sometimes double or triple the scan time in trade for extra slices, if you are not careful. You can see the number of acquisitions at the bottom of the screen near the save series button (figure 3.12). To the right of the # of Acquisitions, you will see two other numbers: Max # of Slices and Total # of Slices. Max # of slices tells you how many slices you are allowed per acquisition with your current scan parameters. Total # of Slices tells you how many slices you currently have prescribed. The number of acquisitions is dependent upon the number of slices you are taking. Therefore, if Total # of Slices > Max # of slices, then you will have more than one acquisition. It can be very frustrating if you really want 30 slices, but only have a maximum number of 29 slices allowed. You don’t want to make your patient stay in the scanner for double the scan time, but it is essential to get that extra slice. What can you do to fix it? One quick way is to bump up the TR by a small amount, so that you don’t really change any of the weighting parameters, but you have a longer repetition time. Let’s look at this for a Spin Echo Sequence.

Fig 3.12 Number of acquisitions Rx Scan Time 3:13 Save Series

In a spin echo you have the following:

90 0 pulse

Echo

TE Where in the above, TE is time to echo and TR is time to repetition. During TR is when the slices are collected. Therefore, you can see that a longer TR will allow for more slices! So, if you need a few more slices, just bump up the TR by a tiny bit to keep your scan at one acquisition.

Total # slices: 26

Fig 3.13 Spin echo pulse sequence

TR

1800 pulse

# of Acqs.: 1

Max # of slices: 28

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STEP 8—Prepare the final four scans and auto-scan your friend. Time is of the essence when working on the MRI scanner both for your patient’s benefit and because of the busy hospital schedule. Therefore, normally when scanning a protocol, after getting through the first setup scans (i.e. 3-plane and calibration), while your first scan is running, you can prescribe the rest of the scans and then click auto-scan. Auto-scan will automatically and continuously run the rest of the scans, so there is no down time inbetween scans. We will setup for auto-scan while the axial-pd scan is running. Go to the RX manager and click on the sag PD freq. Click View Edit and go to the graphic rx. Prescribe the slices for the saggital orientation by moving the slices on the views to match those in figure 3.14. When you are all set, click Save series.

What’s the difference between PD Freq and PD FATSAT? These are different sequences that are used to highlight different portions of the anatomy. PD (Proton Density) is just as its name describes—a sequence that utilizes the ‘proton density’ of hydrogen atoms in tissues. Fluids have the highest Proton Density. PD FATSAT is a PD weighted sequence that suppresses the fat signal. This is done by giving a selective RF pulse to fat protons just before an imaging sequence. Therefore, the fat protons cannot recover to their normal magnetization and their signal is suppressed during the imaging scan. Fig 3.14 Graphic RX for saggital pd

X

Graphic Rx

3 1

Erase Selected Erase All Reset Center

Fallback to SO

Loc Ref Lines

Report Cursor

Update All

Keep W/L

Display Normal 1.0 2

ZOOM


Graphic Rx

Scan Plane: Oblique

*

FOV: 16.0


Phase FOV Fat

Accel. Bar:

Slice

Water

Freq DIR: A/P Acqs Before Pause: TR: 4825.0

Numbe of 1 Radial Slices

Minimum TR: 217.0

Hide Shim

Start:

R112.3

P7.4

S0.2

End:

R25.5

A22.7

I2.4


dB/dt: First Level SAR: First Level

Max # of slices: 3

# of Slices

2

CW CCW


Research Operations...

0.0

SPECIAL

Spacing

Shim FOV:

Save Series

4.0

Thickness:

Fat Classic

Shime Vol

Radial Direction

3 1

...

3


Total # slices: 3




Scan Auto Prescan

Manual Prescan

Prep Scan


That was simple enough, now lets move on to the sag PD fatsat. Click View Edit, and go to the graphic RX. In clinical scans, it is important that within the same view, you get the same slices for different scan types. To do this, you want the same slices that you already choose for the Sag PD Freq. Click on Copy Rx (figure 3.15) and choose the Sag PD Freq RX to copy. The slices will appear on the screen as you already prescribed them for the previous scan. Click save series.

3 PLANE LOC all of your Now,ACT you have prescribed NEW AXL PD scans. Click on the Auto Scan box at the NEW SAG PD FSAT bottom RXPD manager NEWof the SAG FREQ (figure 3.16). YourNEW scans will now continue to run until COR PD FSAT NEW COR PD FREQ they are finished. You do not have to press anything. Just continue to watch the patient and update them on the scan timing before each scan starts. Fig 3.16 Auto-scan button

View Edit

Now, let’s go on to prescribe the coronal freq, and coronal fatsat. You are going to do exactly what you did for the saggital views, only prescribe different slices on the first coronal scan, to match the coronal orientation (figure 3.15) and then copy those to the second coronal scan. When you prescribe each scan, remember to save the series.

Download Save as Rx Protocol Auto Scan

Auto Step

Fig 3.15 Graphic Rx for coronal pd X 2

Graphic Rx Erase Selected Erase All Reset Center

Fallback to SO

Loc Ref Lines

Report Cursor

Update All

Keep W/L

Display Normal 3 1

1.0 ZOOM


...

Graphic Rx

Scan Plane: Oblique

*

Phase FOV Fat

Accel. Bar:

Slice Spacing

Water

Freq DIR: R/L Acqs Before Pause: TR: 3325.0

Numbe of 1 Radial Slices

Minimum TR: 134.0

Hide Shim

2

CW CCW


Start:

R81.6

A44.2

0.0

End:

R64.9

P28.9

0.0



0.0

SPECIAL

Shim FOV:

Save Series

6.0

Thickness:

Fat Classic

Shime Vol

Radial Direction

3 1

FOV: 14.0


Max # of slices: 3

# of Slices

3


Total # slices: 3




Scan Auto Prescan

Manual Prescan

Prep Scan

9

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STEP 8—Take your friend out of the scanner After the last scan has finished, go into the MR room and press the home button on the scanner to bring your friend out of the magnet. Open the coil so they can take their knee out of it, unplug the coil, and lower the table so they can get down. Clean up the room and restore it back to its original state.

STEP 9—Show your friend the images on the screen and burn them a CD Your friend was very generous to let you test out your MR skills on them for the first time. So it’s time to give them something in return. First, open up their scans in the browser window and walk them through their anatomy. Second burn them a CD so they can take the images home with them. To burn a CD, in the browser window click CD/DVD. Insert a blank CD into the CD drive of the computer. Go to select the series you want to add on the list of scans. You can only select one series at a time. After you select the series you want, open up the CD/DVD burner window, by clicking the CD/DVD button on the right panel of the browser. In the CD/DVD burner window, hit Add Series. Do this for all of the series that you want to add to the CD, and then click Copy. This will burn all of the images to the CD in a dicom format. The burner also automatically adds a dicom viewer to the disk so your friend can view the images on any computer. CD/DVD Composer Add Exam Selected Drive: _

Clear

Add Series DICOM CD 1

Ex: 0000 +

Se: 1

+

Se: 2 Se: 3

Application: Selection: Remove Sort: Network Archive: PPS Queue Utilities Services Messages +

Examinations : Exam

| Name

4238/MR55| | MR PLASTIC

| Date

Exam no 4238. Mar 04 09, MR PLASTIC

| Description | Mod| PPS | A |

| Mar 04 09 | QA

| MR | -

Ser

| Type 1 2

| N |

| Imgs

| PROSP | | PROSP |

| Description| Mod| PPS | Manf |

32 | MY FIRST S | MR | 32 | MY SECOND | MR | -

| GEMS | | GEMS |

Add/Sub CD/DVD CIET Clariview Data Export Edit Patient Film Composer

Functool

Used Space: 8.12 MB 173 examinations Series no 1 - PROSP MY FIRST SCAN Img 1 2 3 4 5 6 7 8 9 10 11 12

| | | | | | | | | | | | | |

Loc | Flip | Echo | TE | (mm)| | (deg)| | | | S100.0 | 60 | 1/1 | 1.528 | S 93.5 | 60 | 1/1 | 1.528 | S 87.0 | 60 | 1/1 | 1.528 | S 80.5 | 60 | 1/1 | 1.528 | S 74.0 | 60 | 1/1 | 1.528 | S 67.5 | 60 | 1/1 | 1.528 | S 61.0 | 60 | 1/1 | 1.528 | S 54.5 | 60 | 1/1 | 1.528 | S 48.0 | 60 | 1/1 | 1.528 | S 41.5 | 60 | 1/1 | 1.528 | S 35.0 | 60 | 1/1 | 1.528 | S 28.5 | 60 | 1/1 | 1.528 |

TI | | | | | | | | | | | | | |

TR (ms) 160 160 160 160 160 160 160 160 160 160 160 160

Copy TDEL

| | | | | | | | | | | | | |

(ms)

Stop

| | | | | | | | | | | | | |

Restore

Thck/Sp (mm) 5.0/ 1.5 5.0/ 1.5 5.0/ 1.5 5.0/ 1.5 5.0/ 1.5 5.0/ 1.5 5.0/ 1.5 5.0/ 1.5 5.0/ 1.5 5.0/ 1.5 5.0/ 1.5 5.0/ 1.5

| | | | | | | | | | | | | |

FOV (cm) 24x24 24x24 24x24 24x24 24x24 24x24 24x24 24x24 24x24 24x24 24x24 24x24

| | | | | | | | | | | | | |

2 series

Matrix | NEX | 128x128 | 1.00 128x128 | 1.00 128x128 | 1.00 128x128 | 1.00 128x128 | 1.00 128x128 | 1.00 128x128 | 1.00 128x128 | 1.00 128x128 | 1.00 128x128 | 1.00 128x128 | 1.00 128x128 | 1.00

Eject | Archive | | | | | | | | | | | | | |

No No No No No No No No No No No No

Options

Quit

IVI Mini Viewer PACC

| | | | | | | | | | | | |

ProtoCopy ProtoExchange

Reformat SR Viewer SWIFT Viewer 32 images

Fig 3.17 CD/DVD window

11

You’re done now! Congratulations on your first successful human scan! You are now ready for more interesting anatomies! Next we will go on to the brain!

Fig 3.17 Coronal Fatsat

Fig 3.18 Coronal freq

Fig 3.19 Saggital Fatsat

Fig 3.20 Saggital Fatsat