Discovery MR750 3.0T System Service Methods
5690009-2EN Revision 4
Object ID: 00000018WIA3026DE20GYZ
Topic ID: id_13107156 Version: 3.3
Date: Apr 23, 2020 7:31:11 PM

HD T/R Quad Extremity Coil SNR Test

Prerequisites

Table 1. Personnel requirements
Required persons	Preliminary requirements	Procedure	Finalization
1	Not Applicable	15 minutes	Not Applicable

Table 2. Tools and test equipment
Item	Quantity	Effectivity	Part number	Manufacturer
T/R Quad Extremity Legacy Coil Phantom	1	Legacy Phantom Set	5147225-3	-
T/R Quad Extremity Coil Phantom Positioner	1	-	5147225-7	-
3.0T Large Cylindrical Unified Phantom	1	Unified Phantom Set	5342679-2	-

Table 3. Required conditions
Condition	Reference	Effectivity
The following must be present on the system: Coil: HD T/R Knee/Foot Coil by Invivo. Configuration: GE_HDX QUADKNEE.	-	-

About this task

Follow this process to prepare for the SNR test using the Invivo 3.0T HDT/R Quad Extremity Coil, M3335LP, curved base.

Topic ID: id_SL2735141-538530

Coil Imaging Performance Verification

About this task

The GE HD T/R Quad Extremity Coil has one coil name: HD T/R Knee/Foot Coil by Invivo, and can be used in the QUADANKLE, QUADFOOT or QUADKNEE mode. The image quality check uses two different protocols for signal and noise image acquisition:

Signal scan is an FSE sequence used to minimize susceptibility and B0 inhomogeneity effects. The signal scan must be run prior to the noise scan since the R1, R2, and TG values from the signal scan are used for the noise scan.
Noise scan is a GRE sequence that has a Control Variable (do_noise) to eliminate the Transmit RF completely during the scan.

The Data Sheet in the Finalization section at the end of this procedure explains the data required to calculate the individual element Signal-to-Noise Ration (SNR).

Topic ID: id_SL3530159-538530

Legacy Phantom Coil Setup

Procedure

Remove all other surface coils, and place the Quad Extremity Coil on the patient table without any pads. (The coil should be positioned such that its cables exit toward the magnet.) Set the phantom positioner into the coil as shown.

Figure 1. Placement of Posterior Section and Phantom Positioner
Center the coil within the baseplate, and place the phantom in the phantom positioner.

Figure 2. Phantom in Positioner
Attach the anterior portion of the coil.

Topic ID: id_SL2925190-538530

Unified Phantom Setup

Procedure

Place the baseplate of the coil on the patient table as shown.

Figure 3. Baseplate of Coil on Patient Table
Align the alignment mark on the coil to the zero position on the scale as shown.

Figure 4. Alignment Mark at Zero Position
Place the Phantom Positioner into the coil as shown.

Figure 5. Phantom Positioner Placement
Notice

Illustrations in this section show a phantom with green solution for 1.5T systems. Use phantoms with pink solution for 3.0T systems.
Place the large Cylindrical Unified Phantom in the phantom positioner.

Figure 6. Phantom Placed in Positioner
Attach the anterior portion of the coil to the baseplate, and lock the coil.

Figure 7. Anterior Portion of Coil Attached to Baseplate

Figure 8. Coil Lock

Topic ID: id_SL2925189-538530

Signal Scan

Procedure

From the Scan Desktop, start a new scan by selecting New Pt. For Patient ID, use geservice and 111 pounds for Patient Weight. Select Patient Position to open Protocols window.
At the magnet, press the Alignment Light button to turn on the light.
1. Move the table to align the coil to the alignment lights as shown using the alignment markings on the coil in front of the chimney.
2. Press the Landmark button to landmark the alignment.
  
  Figure 9. Coil Alignment
Move the coil to the scan position by pressing the Move to Scan button, ensuring the cable does not get snagged.

At the console, set the protocols per the Signal section from the table below.

Table 4. Signal and Noise Protocols
Protocol	Signal	Noise
Patient Exam Information:
Patient ID	geservice	geservice
Patient Name
Patient Weight	111 lb. (50 kg)	111 lb. (50 kg)
Patient Position:
Patient Position	Supine	Supine
Patient Entry	Feet First	Feet First
Coil	QUADKNEE	QUADKNEE
Series Description	Signal	Noise
Imaging Parameters:
Plane	Axial	Axial
Mode	2D	2D
Pulse Seq	FSE-XL	GRE
Imaging Options	Fast (or None)	None
PSD Name	Leave blank.	Leave blank.
Protocol	Leave blank.	Leave blank.
Scan Timing:
No. of Echoes	1	1
TE	17	Min. Full
TR	500	34
Echo Train Length	4	N/A
Bandwidth	15.63	15.63
Additional Parameters:
Flip Angle	N/A	1
Acquisition Timing:
Freq	256	256
Phase	256	256
NEX	1	1
Phase FOV	1	1
Freq DIR	R/L	R/L
Auto Center Freq	Peak	Peak
Autoshim	On	On
Phase Correct	On	N/A
Contrast	Off	Off
No. of Reps B4 Pause	0	N/A
Scanning Range:
FOV	20	20
Slice Thickness	3	3
Spacing	1.5	1.5
S/I Start	0	0
R/L Center	0	0
A/P Center	0	0
S/I End	0	0
No. of Slices	1	1
Table Delta	0	0

Click Save Series to download the protocols.
Run Auto Prescan. Record the R1, R2 and TG values.
Run Scan.

Topic ID: id_SL3530163-538530

Noise Scan

About this task

A signal scan must be run prior to the noise scan as the same R1, R2 and TG values must be used for both of these scans. Do not run an Auto Prescan prior to the noise scan as the values will be changed.

Procedure

Copy the signal scan series. Select Copy Series, right mouse click and Paste Series in Rx Manager.
Click View Edit and set the protocols per the Noise column in Table 4.
Select Save Series and Prepare to Scan.
Open the Display CVs menu under Research Operations. Set the rhformat and do_noise CVs to 1.
Run Manual Prescan, and do not make any changes. Verify that R1, R2, TG and Bandwidth did not change from the previously completed signal scan, and select Done.
Run Scan.

Topic ID: id_SL2735159-538530

SNR Measurement

About this task

A circular Region of Interest (ROI) should be used for the signal measurements, and a rectangular ROI should be used for the noise measurements. The actual ROIs should be similar in shape and size to those shown below.

Procedure

ROIs in both signal and noise images can be measured directly in the image browser. Click the MEASURE button, select the circular or rectangular shape, and adjust its size and orientation so that the ROI is similar to the illustration above. (Mean, standard deviation, and area of the ROI will display in the lower right corner of the image.)
For ROI measurements:
- For signal measure measurement: Choose a 10 cm diameter, circular ROI (approximately a 5,600 mm²).
- For the noise measurement: Choose a 19 cm rectangular ROI (approximately 34,000 mm²).
Calculate and record the values for mean signal, standard deviation of noise, and SNR in the Data Sheet found in the next section.

Note:
The SNR calculation uses the Mean of the signal image and Standard Deviation of the noise image.

Figure 11. SNR Calculation

The SNR measurements must be greater than or equal to the following specifications:

Table 5. SNR Specifications
SNR (1.5T) SNR (3.0T)
200 Legacy Phantom 410
Unified Phantom 207

Table 5. SNR Specifications
SNR (1.5T)	SNR (3.0T)
200	Legacy Phantom 410 Unified Phantom 207

Topic ID: id_14964593

Finalization

The Data Sheet to record the calculated SNR ratio data obtained in this procedure can be found in this file: 538814.pdf.