Topic ID: id_15271088
Version: 4.1
Date: Dec 6, 2019 3:11:40 PM

System gain calibration

Prerequisites

Table 1 Personnel requirements
Required persons	Preliminary requirements	Procedure	Finalization
1	5 minutes	Head and Body 20; Body 10; Head 10 minutes	Head and Body 2; Body 2; Head 2 minutes

Table 2 Tools and test equipment
Item	Quantity	Effectivity	Part number	Manufacturer
Body TLT sphere for 1.5T	1	-	2135650	-
Body TLT loader for 1.5T	1	-	2135652	-
Head TLT sphere for 1.5T	1	-	46-265826G6	-
Head TLT loader for 1.5T	1	-	46-287900G3	-
Head loader positioner	1	-	5110241	-

Table 3 Required conditions
Condition	Reference	Effectivity
No required conditions.	-	-

Overview

System gain calibration is performed to determine the standard head (transmit/receive coil) and body recon scale factors that will achieve a known level of image intensity when using the standard head coil or body coil with a known phantom solution and protocol. The goal is that when the same solution or tissue is scanned in either the standard head or body coil with the same protocol, those tissues will have approximately the same image intensity level on a given system and between systems of like type.

This calibration accounts for differences in standard head and body receive coil sensitivity, preamp gains, cable loss, receiver gain, and other factors. The calibration must be done on standard head and body at least once to calibrate those paths. The procedure can calibrate both standard head and body together, only head, or only body. System gain calibration consists of:

Head and body calibration section.
note: Although these calibrations can not be run simultaneously, they can both be selected at the same time to run serially. Otherwise, run individual modes as listed in the next two options.
Body calibration section
Head calibration section

Table 4 Typical body system gain values
Receive chain	Magnet field strength	System gain value
RRx	3.0T	10
	1.5T	2.5
DPP	3.0T	27
	1.5T	7.5
Note: The values in this table are meant to illustrate the typical system gain values that may be observed on site. System gain varies by receive chain and should be calibrated for each site.

Preliminary setup

Procedure

Position the head sphere in the head loader and fasten the strap. Position the head loader on top of the head loader positioner in the head coil so the loader's black center line lies directly below the head coil's superior/inferior center marker.

note: 3.0T spheres are pink. 1.5T spheres are light green.

Figure 1. Positioning head sphere loader

Figure 2. Landmark head sphere
1 Black line on loader

2 S/I center line on coil
Make sure the top section of the split-top coil is properly oriented. Align the arrows on the NOTICE labels for the correct orientation.
Properly position the head sphere and loader as previously noted.
Landmark on the center line of the head loader, but do not advance to scan.
Run the cradle in so the display reads 1135 mm.

Figure 3. Distance between head coil landmark and center mark on body loader
Turn on the alignment light, and then position the body loader on the cradle so that the alignment light is properly centered on the loader crosshair. Place wedges on both sides of the body loader to prevent movement.
Press Advance to Scan.
Start the System Gain Calibration tool:
1. (For non-proprietary service tools) From the Common Service Desktop, select Calibration > System Gain Calibration. Select Click here to start this tool.
The System Gain Calibration window appears.

1	Black line on loader
2	S/I center line on coil

Calibrations (in software versions prior to DV26)

Procedure

Head and Body Calibration
1. At the System Gain Calibration Test Modes menu, type 3 and press Enter to select Both Head and Body Mode. The calibration begins.
  
  Head gain is calibrated first. When head is complete, body is calibrated. The following two illustrations apply to both head and body.
  
  Figure 4. Starting system gain calibration tool (prior to DV26)
2. The calibration results display on the screen. If adjustments are required, the system asks, Do you want to save the recon scale factor? Type Y and press Enter to save the recon scale factor.
  
  note: There are (at least) two prompts: one for head and one for body.
  
  Figure 5. Calibration output (prior to DV26)
Body Calibration
1. note: The system is dependent on landmarking the head coil, even for body only scans.
  Type 2 and press Enter to select Body Mode, and the calibration begins. (See Figure 4.)
2. When the test is complete, the calibration results display on the screen. If adjustments are required, the system asks, Do you want to save the BODY recon scale factor? Type Y and press Enter to save the calibration file. (See Figure 5.)
3. Type 4 and press Enter to exit the tool. The calibration is complete.
Head Calibration
1. Type 1 and press Enter to begin Head Mode. (See Figure 4).
2. When the test is complete, the calibration results display on the screen. If adjustments are required, the system asks, Do you want to save the HEAD recon scale factor? Type Y and press Enter to save the calibration file. (See Figure 5.)
3. Type 4 and press Enter to exit the tool. The calibration is complete.

Calibrations (in software versions DV26 and for RRX receiver systems DV26 and later)

Procedure

Head and Body Calibration
1. In the System Gain Tool window, select Head & Body and then select START. Calibration begins.
  
  Head gain is calibrated first. When head is complete, body is calibrated. The illustrations below apply to both head and body.
  
  Figure 6. Starting system gain calibration tool (DV26 and later)
2. The calibration results show on the screen. If adjustments are required, the system asks, Do you want to save the recon scale factor? Click Yes to save the recon scale factor.
  
  note: There are (at least) two prompts: one for head and one for body.
  
  Figure 7. Calibration output (DV26 and later)
Body Calibration
1. note: The system is dependent on landmarking the head coil, even for body only scans.
  Select Body, and then click START. Calibration begins. (See Figure 6.)
2. When the test is complete, the calibration results show on the screen. If adjustments are required, the system asks, Do you want to save the BODY recon scale factor? Click Yes to save the calibration file. (See Figure 7.)
3. Click QUIT to exit the tool. The calibration is complete.
Head Calibration
1. Select Head, and then click START. Calibration begins. (See Figure 6.)
2. When the test is complete, the calibration results show on the screen. If adjustments are required, the system asks, Do you want to save the HEAD recon scale factor? Click Yes to save the calibration file. (See Figure 7.)
3. Click QUIT to exit the tool. The calibration is complete.

Calibrations (SW version 27 and later)

Procedure

For SW version 27 and later, system gain calibration is part of SPT.

Finalization

Procedure

Remove all phantoms and service tools from the patient table.
If you are doing this calibration during an installation, continue with the required calibrations. Otherwise, complete a SaveInfo to save the new ReconScale values.