x ray alignment

7/25/2019 X RAY Alignment

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GE MEDICAL SYSTEMS FUNCTIONAL CHECK/ADJUSTMENT

3-1

HiSpeed Dual, ProSpeed FII Series

SYSTEM

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SECTION 3 - X-RAY ALIGNMENT

3-1 GENERAL

This X-ray Alignment consists of the following check/adjustment procedures and must be performed in this order.

Order X-Ray Alignment Item Description

1 Detector Position Alignment Adjusts parallelism and detector Z-axis position to Gantry bear-ing surface

2 Aperture Position Alignment Adjusts the aperture parallelism and distance between the ap-erture and Gantry bearing surface

3 Plane Of Rotation(POR) Filmless POR:The tube warm-up scans are automatically per-formed until the case temperatrue becomes 30%, then the tubeposition in Z-axis direction is adjusted. The tube travel is calcu-lated from the count ratio A(A+B) of 150 channels (R50ch,C50ch, and L50ch).

4 Detector Beam-On-Window(BOW) Filmless BOW:The tube warm-up scans are automatically per-formed until the case temperatrue becomes 30%, then the De-tector position in Z-axis direction is adjusted. The tube travel iscalculated from the count ratio A(A+B) of 150 channels (R50ch,C50ch, and L50ch).

5 Qcal Channel Ratio Compensates sensitivity between A and B slices for Z-axisbeam tracking

Gravity SAG (G-SAG) Check procedure for the Gantry rotating mechanism (bend, vi-brations, etc.)

6 ISO Center Alignment Aligns the X-ray tube focus to the FOV center and the Detectorcenter channel.

7 Filter Center Alignment Aligns the filter to the X-ray tube and the Detector.

Note1: G-SAG is performed if considered necessary.

Note2: If you are sure that some procedures do not have to be performed, in this case, the possible allowed pro-cedure combination/order should be:

At site installation or X-ray tube replacement, perform 1 2 3 4 5 6 7.At detector replacement, perform 4 5 6 7.

Note3: Z-axis mis-alignment has serious effect on an image quality for the Twin Detector system, as compared

to the single detector system. Therefor, the Detector position alignment, aperture position alignment, andtube warm-up sequence at POR and BOW must be properly performed.


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3-1 GENERAL (CONTINUED)

Difference of POR Between Twin Detector and Single Detector

For POR of the Twin Detector system, the Xray beam location after adjustment is determined by the initial position

of the Aperture and Detector (the center between A and B slices).

Therefore, the Xray beam location adjusted by Filmless POR might be different from one by Film POR, but it is

no problem due to the fact that:

A slight tilt of Xray beam against Zaxis has little effect on an image quality.

The Aperture and Detector are installed using the special tools shipped with the system to ensure reli-

able position and parallelism. (The single Detector does NOT require the aperture alignment tool.)

During Filmless POR, the Xray tube temperature is controlled by software so that the Xray beam can

be exposed at a certain location of the detector. (The single Detector does NOT control the Xray tube

temperature.)


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WARNING

ROTATION HAZARD !IN THIS X-RAY ALIGNMENT, GANTRY COMPONENTS ARE ADJUSTED AND SCANS ARE

PERFORMED. ALWAYS SWITCH OFF THE ROTATE SWITCH BEFORE SERVICING OR

ADJUSTING THE GANTRY. ALSO VERIFY THAT NO PEOPLE ARE IN THE SCAN ROOM

WHENEVER A SCAN IS PERFORMED.

Requirements

The critical componentsfor X-ray Alignment are all mounted directly to the rotating Gantry; they are:

X-ray tube

Collimator (includes a bow-tie filter and an adjustable beam defining exit slit)

Detector

Tools and materials required for x-ray alignment:

Detector alignment tool (shipped with the system)

Aperture alignment tool (shipped with the system)

G-SAG pin (attached on the bottom of the collimator)


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Gantry Geometry

Gantry geometrical direction definitions:

Theta Tangent to Gantry rotation.

clockwise (+)

counterclockwise ().

Zero

degrees

(HOME)

6 oclock

ZAxis Parallel to the axis of Gantry rotation.

toward the Table ()

away from the Table (+).

Adjustment possible for: X-ray Tube Collimator Detector

Adjustment possible for: X-ray Tube Detector

THETA THETA


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3-2 DETECTOR POSITION ALIGNMENT

This procedure keeps constant the distance between the Zaxis adjusting nut (left, center, and right) for the Detector

and Detector support plate so that the Detector can be installed parallel and at a predefine distance (12mm) with the

Gantry bearing surface.

Special Equipment

Detector Alignment Tool (Shipped with the system)

1. Preparation:

a. Set the Gantry to the 0Otilt position.

b. Switch OFF the Rotate, XG Power and Slip Ring115V switches at the rear Gantry base.

c. Remove the front, rear, and left maintenance covers from the Gantry.

2. Switch ON the service switch on the SUB board.

3. Rotate the Gantry until the DAS Assy reaches the 6 oclock position by hand.

4. Switch OFF the service switch on the SUB board.


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3-2 DETECTOR POSITION ALIGNMENT(CONTINUED)

5. Loosen the three Detector locking screws. (Do NOT remove them.)

Illustration 3-1 Detector Locking Screws


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3-2 DETECTOR POSITION ALIGNMENT(CONTINUED)

6. Using the Detector Adjustment Tool, set the distance between the Zaxis adjustment nut and detector support

plate to the so that it is the same one as the thickness of the tool.

Illustration 3-2 Detector Alignment Tool

7. Tighten the three detector locking screws securely.

8. Proceed to Section 3-3, Aperture Position Alignment.


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3-3 APERTURE POSITION ALIGNMENT

This procedure keeps constant the distance and parallelism between the aperture and Gantry bearing surface.

Special Equipment

Aperture Alignment Tool (Shipped with the system)

1. Preparation:

a. Set the Gantry to the 0o tilt position.

b. Switch OFF the Rotate, XG Power and Slip Ring115V switches at the rear Gantry base.

c. Remove the front, rear, and left maintenance covers from the Gantry.

2. Switch ON the service switch on the SUB board.

3. Rotate the Gantry until the Aperture Assy reaches the 6 oclock position by hand.

4. Switch OFF the service switch on the SUB board.


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3-3 APERTURE POSITION ALIGNMENT(CONTINUED)

5. Set the collimator to the initial position.

a. Switch ON all switches at the rear Gantry base.

b. Select Service > Offline Scan > T/G Control.

c. Set Collimator Control:

Auto Collimator: OFF, Position Change: ON, Move mode: Rel., Reset: ON

d. Click on OK. Verify that the aperture stepping motor rotates.


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6. Switch OFF the Rotate, XG Power and Slip Ring115V switches at the rear Gantry base.

7. Remove the two nuts and rear lead (Pb) plate from the aperture Assy.


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8. Loosen the following nuts and screws of the aperture Assy. (Do NOT remove them.)


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9. Set the Aperture alignment tool in between the Gantry bearing and aperture Assy.

10. While pressing the Aperture Assy against the aperture alignment tool, tighten the aperture nuts and screws

gradually in the order shown in the photograph below.

11. Remove the Aperture alignment tool.

Aperture Alignment Tool

PUSH

1

2

3

5

67

4


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12. Reinstall the rear lead (Pb) plate onto the Aperture Assy with the lead side facing to the front. Tighten the two

plate mounting nuts . (Torque: 37 kgf.cm)

13. Proceed to Section 3-4, Plane Of Rotation .


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3-4 PLANE OF ROTATION

This procedure checks and adjusts the plane of rotation of the x-ray fan beam until it is perpendicular to the axis of

Gantry rotation within 0.75 mm.

The Filmless POR is performed for the Twin system.

IMPORTANT NOTE: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Do not remove the bowtie filter during POR for the Twin System.

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1. Preparation:

a. Switch OFF the Rotate switch.

b. Remove the front, right side, and left maintenance covers.

2. Select Service > Automated Alignment > POR Alignment.

3. Click on OK to enter the POR program.

4. Click on Confirm to enter warm up scan sequence.

5. Click on Confirm in the Service Scan Window.

The warm up scans start, then air scans automatically start.

6. The tube travel appears on the screen. If the following message appears, you can complete the POR proce-

dures.

******************************* Displayed *******************************

Tube is Aligned within tolerance.

For Accuracy

Move Tube x.xxx mm (x.xxxx inch) FWD.

***************************************************************************

7. Adjust the tube Z-Axis position:

a. Rotate the Gantry (Tube) to the 12 oclock (home) position.

b. Switch OFF the Rotate and XG Power switches.

c. Loosen the 4 mounting bolts. See Illustration 3-3.

d. Locate the Adjustment Nuts for Z-Axis; note that there are two Z-Axis nuts for adjustment.

e. Loosen the nut that faces the direction in which you want to shift the tube.

f. Adjust the x-ray tube position by turning the adjustment nut by the amount instructed on the CRT screen.

In this example, the tube should be shifted axially toward the Table to center the wide beam over the narrow

beam.

g. Tighten the nut previously loosened in step e.

h. Tighten the 4 mounting bolts. (Torque: 280 kg-cm)

i. Switch ON the Rotate and XG Power switches.

j. Return to step 2.

8. Proceed to Section 3-5,Detector Beam-on-Window.


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3-4 PLANE OF ROTATION(CONTINUED)

Illustration 3-3 X-ray Tube Positioning

Nut to be loosenedor Tightened

Direction to move

Front Rear Left Right

Nut A Tightened Loosened - -

Nut B Loosened Tightened - -

Nut C - - Tightened Loosened

Nut D - - Loosened Tightened

Mounting Bolts

Mounting BoltsAdjustment Nut for THETA

Adjustment Nut for Z-Axis

REARFRONTRIGHT

LEFT

NUT ANUT BNUT CNUT D

Note: When loosen respective adjustment nut, use two spanner. One spanner

holds one nut, the other one loosens another nut. This will avoid damaging the

adjustment screws when adjusting the position of the nut. Please refer to above photo.

Note:

One turn 9 1 mm shift.


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3-5 DETECTOR BEAM-ON-WINDOW

To ensure that the entire width of the x-ray beam falls within the Detector window, follow this procedure for a Z-Axis

position check/adjustment of the Detector.

For Detector Zaxis alignment of TWIN system, high accuracy is required for geometric position between Xraybeam and detector. Detector is aligned so that each detector channel (Ach and Bch) counts becoming same.

This Filmless Detector Z axis alignment require a scan to the user, and calculates ratio of counts between A side

and B side on 3 area, (left, center, right). The ratio is converted to tolerance of detector (mm) and displayed. The

user move detector and retry BOW.

IMPORTANT NOTE: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -Do not remove the bowtie filter during BOW for the Twin System.

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1. Preparation:

You do not have to perform the following, if you have just completed the Plane of Rotation procedure.


b. Remove the Gantry front, rear, right side, and left maintenance covers.

c. Switch ON the Rotate switch.

2. Select Service > Automated Alignment > BOW alignment.

3. Click on OK to enter the BOW program.

4. Click on Confirm to enter warm up scan sequence.

5. Click on Confirm in the Service Scan Window.

The warm up scans start, then air scans automatically start.

6. The detector travel appears on the screen. If the following message appears, you can complete the BOW pro-

cedures.

******************************* Displayed *******************************

Detector is Aligned within tolerance.

***************************************************************************

7. Adjust the Detector ZAxis position:

a. Check that the Gantry is at the home position.

b. Switch OFF the Rotate switch.

c. Remove the flexible cable cover. See Illustration 34

d. Loosen the three locking screws (Allen cap head).


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3-5 DETECTOR BEAM-ON-WINDOW (CONTINUED)

Illustration 3-4 Beam-on-Window Adjustment

e. Adjust the Detector position by turning the adjustment nut(s) by the amount instructed on the CRT screen.

Formula: x.xxxx mm / 0.75 = 1/xx turn of adjustment nut

Counterclockwise ;FWD, toward the Table

Clockwise ;BWD, away from the Table

Specification : Detector Left, less than 0.072 mm

Detector Center, less than 0.076 mm

Detector Right, less than 0.072 mm

f. Tighten the three locking screws.

g. Switch ON the Rotate switch.

h. Return to step 2.

8. Proceed to Qcal Channel Ratio .

Flexible Cable Cover Detector Z-Axis

Adjustment Nut

Locking Screw(Allen Head)

Detector

DetectorSupport Plate

Pin

DetectorSupport Plate

Z-AxisAdjustment Nut

Detector

Locking Screw(Allen Head)


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3-6 QCAL CHANNEL RATIO

This calibration must be performed just after completion of Filmless BOW.

IMPORTANT NOTE: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Do not remove the bowtie filter during Qcal Channel Ratio.----------------------------------------------------------------------------------------------------------------------------------------

1. Preparation:

You do not have to perform the following, if you have just completed the BOW procedure.


b. Remove the Gantry front, rear, right side, and left maintenance covers.


2. Select Service > Automated Alignment > Qcal Channel Ratio.

3. Click on OK to enter the Qcal channel ratio program.4. Click on Confirm in the Service Scan Window.

The scans start, then calibration automatically starts.


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3-7 GRAVITY SAG

1. Preparation:

You do not have to perform the following, if you have just completed the Detector Beam-on-Window

procedure.a. Switch OFF the Rotate switch.

b. Remove the Gantry front and both side covers.

c. Remove the bow-tie filter from the collimator. (Refer to the Component Replacement manual)

d. Switch ON the Rotate switch.

2. Select Gravity SAG, refer to below:

Service Gravity SAG

3. Within the Gravity sag menu, click on Cofirmand press the button to perform air scans

automatically.

4. After completing air scans, install the G-SAG pin:


b. Set the Service switch to ON on the SUB Board.

c. Rotate the Gantry manually in the CW direction until the x-ray tube is positioned at the bottom.

d. Set the Service switch to OFF.

e. Move the G-SAG pin into the position shown in Illustration 3-5.

f. Switch ON the Rotate switch.

Illustration 3-5 Installing G-SAG Pin

SAG Pin

(Original Position) (Moved)

BOTTOM VIEW OF THE COLLIMATOR


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3-7 GRAVITY SAG (CONTINUED)

5. Click on Cofirmand press the button to perform G-SAG PIN scans automatically.

G-SAG calculation is automatically performed and its result is displayed.

Verify that the following is displayed.

******************************* Displayed *******************************Gravity sag is in tolerance

6. If the gravity SAG data is out of specifications, verify that the detector mounting bolts and x-ray tube mounting

bolts are correctly torqued, and then perform this Gravity SAG procedure again.

7. Replace the G-SAG pin:


b. Replace the G-SAG pin to the original position. See illustration 3-5.


8. Proceed to Section 3-8, Iso Center Alignment if you performed the Detector Beam-on-Window procedure

prior to this Gravity SAG procedure; or you do not perform Iso Center Alignment or Filter Center Alignment(Section 3-10), perform the following:


b. Installed the bow-tie filter.


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3-8 ISO CENTER ALIGNMENT

This ISO Center Alignment aligns the x-ray tube focus to the FOV center and the Detector center channel.

Illustration 3-6 ISO Center Adjustment

Note

Within the Automated Alignment menu (Service Automated Alignment), you don not have to

perform the following menus:Tube Rough ISO Alignment

Radial Alignment

These are performed at the GEHW factory only.

1. Preparation:

You do not have to perform the following, if you have just completed the Detector Beam-on-Window or Gravity

SAG procedure.





Focus

X-rayTube

Adjust

Center of FOV

Detector

CH1

Center Channel:342.75 +0.02 CH


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3-8 ISO CENTER ALIGNMENT (CONTINUED)

2. Select Tube ISO Alignment, refer to below:

Service Menu Automated Alignment Tube ISO Alignment

Perform air and pin scans, following the instructions displayed on the CRT screen.

Note

Attach a steel pin, approximately 6 mm in diameter, (ex. drill bit or phillips screw driver) to the

phantom holder at a position approximately 5 cm away from the scan axis center, as shown in

Illustration 3-7.

Illustration 3-7 Pin Scan

Phantom Holder

Pin Position (X,Y)

Screw Driver

x

y

ISO Center

50mm


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3-8 ISO CENTER ALIGNMENT (CONTINUED)

3. Check that the calculated Iso Center Channel data is within a specification.

If the MEAN value is out of specification (342.75 0.02), perform the following step, then follow the instructions

displayed on the CRT screen.a. Adjust the x-ray tube Theta (tangential) position:

i. Rotate the Gantry (Tube) to the 12 oclock (home) position.

ii. Switch OFF the Rotate and XG Power switches.

iii. Loosen the 4 mounting bolts (see illustration 3-3).

iv. Locate the Adjustment Nuts for THETA; note that there are two THETA nuts for adjustment.

v. Loosen the nut that faces the direction in which you want to shift the tube.

vi. Adjust the x-ray tube position by turning the adjustment nut by the amount instructed on the CRT

screen.

vii. Tighten the nut previously loosened in step v.

viii. Tighten the 4 mounting bolts. (Torque: 280 kg-cm)

ix. Switch ON the Rotate and XG Power switches.

4. Proceed to Section 3-9, Filter Center Alignment.


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3-9 FILTER CENTER ALIGNMENT

Procedures

This Filter Center Alignment aligns the filter to the x-ray tube and the Detector.

Illustration 3-8 Filter Center Alignment

1. Preparation:

You do not have to perform the following, if you have just completed the Iso Center Alignment procedure.





Filter Center Ch.: 342.75 +0.3

Detector (Fixed)

VIEW FROM TABLE

Ch1

Filter

Adjust

Center of Filter

Focus

(Fixed)X-rayTube


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3-9 FILTER CENTER ALIGNMENT (CONTINUED)

2. Select Bowtie Filter Alignment, refer to below:

Service Menu Automated Alignment Bowtie Filter Alignment

Perform air and filter scans, following the instructions displayed on the CRT screen.

3. Check that the calculated Filter Center Channel data is within a specification:

If the AVERAGE value is out of specification (342.75 0.3), perform the following step, then follow the

instructions displayed on the CRT screen.

a. Adjust the filter Theta (tangential) position:

i. Rotate the Gantry (Tube) to the 12 oclock (home) position.

ii. Switch OFF the Rotate switch.

iii. Loosen the two bolts indicated in illustration 3-9.

iv. Rotate the adjustment screw to shift the filter for the amount instructed on the CRT screen.

One turn 1 mm filter shift.

v. Tighten the two bolts loosened in step iii.

4. Restore the Gantry to original configuration.

Illustration 3-9 Filter Center Adjustment

Loosen these BoltsAdjustmentScrew

Collimator with Front Cover Removed


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3-10 RADIAL ALIGNMENT

Note

The radial alignment is rarely performed. Only when loosening the detector locking screw (see

Illustration 3-12), this must be performed.

Prerequisite

Radial Alignment Tool : 2234059

1. Preparation:



c. Rotate the Gantry (Tube) to the 12 oclock (home) position.

d. Remove the bow-tie filter from the collimator. (Refer to the Component Replacement manual)

e. Remove the connector cover from the DAS assy.

f. Switch ON the Rotate switch.

2. Select Radial Alignment, refer to below:

Service Menu Automated Alignment Radial Alignment

Perform air and tool scans, following the instructions displayed on the CRT screen.

(Attachment of the Radial Alignment Tool is as shown in illustration 3-11 (A).)

Repeat the above scans for the other tool attachment to obtain calculated Radial Alignment data.

(Attachment of the Radial Alignment Tool is as shown in illustration 3-11 (A).)


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3-10 RADIAL ALIGNMENT (CONTINUED)

Illustration 3-10 Radial Alignment Tool

3. Check that an average of the 2 calculated Radial Alignment data is within a specification.

If not, perform the following steps:


b. Remove the Radial Alignment tool.

c. Install a Dial Indicator on the side of the Detector using an attachment tool.

d. Loosen the three (x2) mounting screws and a locking screw.

e. Refer to the average value, rotate the Detector in the specified distance and direction.

f. Tighten the mounting screws and the locking screw.

Locking Screw Torque:11 Nm (117 kgfcm)

g. Remove the Dial Indicator with attachment tool.

h. Switch ON the Rotate switch.

i. Repeat the Radial Alignment procedure, to verify the adjustment.

A

A'

Radial Alignment Tool


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3-10 RADIAL ALIGNMENT (CONTINUED)

Illustration 3-11 Locking Screw and Mounting Screws

4. Perform the following alignment:

ISO Center Alignment

Filter Center Alignment

5. Restore the Gantry to original configuration.

Dial Indicator

Attachment Tool

Detector

MountingScrews

MountingScrews

Locking Screw

x ray alignment

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