• Topic ID: id_13107156
  • Version: 3.2
  • Date: Jan 17, 2020 11:29:48 AM

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

 -
1.5T Large Cylindrical Unified Phantom 1 Unified Phantom Set

5342679

 -
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.

 - -

Follow this process to prepare for the SNR test using the Invivo 1.5T HDT/R Quad Extremity Coil, M3335ME, curved base.

Coil Imaging Performance Verification

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).

Legacy Phantom Coil Setup

Procedure

  1. 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

  2. Center the coil within the baseplate, and place the phantom in the phantom positioner.

    Figure 2. Phantom in Positioner

  3. Attach the anterior portion of the coil.

Unified Phantom Setup

Procedure

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

    Figure 3. Baseplate of Coil on Patient Table

  2. Align the alignment mark on the coil to the zero position on the scale as shown.

    Figure 4. Alignment Mark at Zero Position

  3. 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.
  4. Place the large Cylindrical Unified Phantom in the phantom positioner.

    Figure 6. Phantom Placed in Positioner

  5. 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

Signal Scan

Procedure

  1. 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.
  2. 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

  3. Move the coil to the scan position by pressing the Move to Scan button, ensuring the cable does not get snagged.
  4. 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
  5. Click Save Series to download the protocols.
  6. Run Auto Prescan. Record the R1, R2 and TG values.
  7. Run Scan.

Noise Scan

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

  1. Copy the signal scan series. Select Copy Series, right mouse click and Paste Series in Rx Manager.
  2. Click View Edit and set the protocols per the Noise column in Table 4.
  3. Select Save Series and Prepare to Scan.
  4. Open the Display CVs menu under Research Operations. Set the rhformat and do_noise CVs to 1.
  5. 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.
  6. Run Scan.

SNR Measurement

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.

Figure 10. Example ROIs

Procedure

  1. 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.)
  2. 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).

  3. 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

Finalization

Finalization

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