Tipo de investigación, técnica y herramientas

General

0

To ensure a maximum output signal for the detector elements, the X-ray beam has to be centered precisely over the detector. The ZCheck procedure provides you with a quick check of the X-ray beam alignment.

The reference value of the tube diaphragm determined via ZAdjust is the starting point of the quick check. The diaphragm is then shifted symmetrically in both Z-directions. The measured detector element output has to follow symmetrical thresholds, as long as the Z-adjustment is still within tolerance. This procedure is automatically added to the cus- tomer "check-up" procedure at specific intervals.

If the result of the ZCheck is out of specification, please perform the ZAdjust procedure.

NOTE There is no need to perform the ZCheck procedure if you have just completed the ZAdjust.

Procedure

0

•

Select Tune-up.

•

Select Expert Mode.

•

Select ZCheck.

•

Select Go.

•

Press START.

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Focus alignment

3.8

General

0

The FocusAli procedure adjusts the electromagnetic focus deflection (flying focal spot) with respect to the parameters of different:

•

Rotation times

•

Integration times of the DMS

•

Focus size

To determine the electromagnetic behavior of the focus deflection circuit, the following adjustments are necessary:

•

Phase: This step determines the synchronization (delay) between the DMS and focus deflection.

•

Amplitude: Based on the neutral position, the amplitude of the focus deflection is determined in mm. With the phase specified, the amplitude is set so that the deflection equals half the width of one detector element.

•

Offset: With the phase and amplitude specified, the offset of the focus deflection is set so that the central beam is exactly in the center of the detector.

The procedure adjusts the settings for phase, amplitude, and offset for all combinations of these parameters.

NOTE To avoid that incorrect adjustment values are created during tune up, only phantoms delivered with the CT system may be used for system adjustments.

Also the water phantom has to have the same temperature as that in the examination room.

Procedure

0

•

Position the alignment phantom in the measurement field.

Fig. 3: Alignment phantom (10 mm al)

•

Select Expert Mode.

•

Select FocusAli.

•

Select Phase, Amplitude, Offset and Calibration.

•

Select Go.

•

The Alignment phantom is selected (default).

•

Select Go.

•

Press START.

•

Select Go (to save the results).

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Medical Solutions

Focus alignment check

3.9

General

0

The FocusAli procedure adjusts the electromagnetic focus deflection (flying focal spot). The CheckAli procedure allows you to check the focus alignment by testing it with freely selectable parameters. CheckAli accesses the last set of raw data generated.

Scan conditions:

•

Combi phantom with alignment phantom and phantom holder (see Focus Alignment).

•

Mode with complete rotation was used.

•

Measurement data was processed, including calibration, and stored.

•

Data was stored in raw data file.

The program checks whether the correct phantom was used in the scan. If not, the align- ment check procedure will be interrupted and an error message is displayed.

If the result of the CheckAli is out of specification, perform the FocusAli procedure.

Procedure

0

•

Select Tune-up.

•

Select Expert Mode.

•

Select CheckAli.

•

Select Fused.

•

Select the raw data file of the last measurement or any other file.

•

Select Go.

Generator adaptation

3.10 (The Plexiglas strip has to be installed.)

General

0

The objective of the generator adaptation procedure is to set the generator parameters (filament current, tube current, and dose) so that a specific noise value is guaranteed across the complete power (kW) range. For this reason, the noise value (sigma) is mea- sured in a 20 cm water phantom with different power (kW) steps.

The generator adaptation has to be performed for:

•

2 predefined kV-steps and

•

1 focal spot size

The procedure adapts the settings for all combinations of these parameters.

NOTE To avoid that incorrect adjustment values are created during tune up, only phantoms delivered with the CT system may be used for system adjustments.

Also the water phantom has to have the same temperature as that in the examination room.

Procedure

0

•

System phantom: Position the slice thickness phantom in the measurement field so that the light beam of the interior light markers is centered above the crossover point on the slice phantom.

Fig. 4: System phantom

Pos. 1 Crossover point

•

Select Tune-up.

•

Select Expert Mode.

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Medical Solutions

•

Select voltage (kV): 80 kV, 130 kV

•

Only the large focus is used

•

Select Go.

•

Press START.

•

Select Go (to save the results).

Filament adaptation

3.11

General

0

The objective of the FilAdapt procedure is to adapt the filament current to changes in the filament due to evaporation. The filament current is adjusted to reach the X-ray dose val- ues determined via the GenAdapt procedure. The generator adaptation procedure opti- mizes the filament current, i.e. you do not have to perform the filament adaptation procedure after you have run a generator adaptation.

This procedure is automatically added to the customer "check-up" procedure at specific intervals.

NOTE There is no need to perform the filament adaptation procedure if you have just completed the generator adaptation.

Required tools and phantoms

0

n.a.

Procedure

0

•

Remove all absorbers from the measurement field.

•

Select Tune-up.

•

Select Expert Mode.

•

Select FilAdapt.

•

Select voltage (kV): 80 kV, 130 kV.

•

Only the large focus is used.

•

Select Go.

•

Press START.

•

Select Go (to save the results).

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Medical Solutions

Warm-up

3.12

(The Plexiglas strip has to be installed.)

General

0

The <WarmUp> procedure is used to ensure a certain minimum (X-ray tube) temperature during table generation procedures. The procedure:

•

is automatically skipped if the defined minimum temperature threshold has already been reached.

•

is performed automatically by all following table generation procedures if the defined minimum temperature threshold has not been reached.

Procedure

0

•

Remove all absorbers from the measurement field.

•

Select Tune-up.

•

Select Expert Mode.

•

Select Warm Up.

•

Select Go.

•

Press START.

Defective channel correction

3.13 (The Plexiglas strip has to be installed.)

General

0

NOTE After performing a “Defective channel correction” procedure, the tune-up steps “Channel Correction”, “Air Calibration”, and “Spac- ing” have to be performed.

Basically, defective channels are handled in two different ways:

Automatic defective channel detection:

Standard procedure recommended for service purposes.

NOTE The program “automatic defective channel detection” deletes the old automatic defective channel list and subsequently creates a new automatic defective channel list.

Channels requiring manual switch-off cannot be deleted via the automatic procedure.

The program “automatic defective channel detection” is also per- formed during the “checkup” procedure. However, the detected defective channels are valid only temporarily until the next “checkup” procedure is performed. No additional tune up steps are required after the “checkup” procedure.

Manual defective channel detection:

To switch off defective channels manually, special detector knowledge about multislice techniques is required.

Manual defective channel correction is performed only if the defective channel cannot be detected automatically (e.g. values are too rough or problem is sporadic).

NOTE Channels switched off manually can be reactivated only by using the same manual procedure.

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Medical Solutions

Examples: Screenshots defective channels

0

Fig. 5: Defective channels

Fig. 6: Defective channels (slice selection)

Automatic defective channel procedure

0

NOTE After performing a “Defective channel correction” procedure, the tune-up steps “Channel Correction”, “Air Calibration”, and “Spac- ing” have to be performed.

•

Remove all absorbers from the measurement field.

•

Select Tune-up.

•

Select Expert Mode.

•

Select Defective Channels.

•

Automatic Detection after Editing is enabled (default).

•

Select Go.

•

Press START.

Wait until the window is refreshed.

•

Select Go (to save the result).

Wait until the message "Procedure Defective Channels completed" appears.

Manual defective channel procedure

0

NOTE To switch off defective channels manually, special detector knowl- edge about (multi) slice techniques is required.

Manual defective channel correction is performed only if the defective channel cannot be detected automatically (e.g. values are too rough or problem is sporadic).

Channels that are switched off manually can be reactivated only by using the same manual procedure.

•

Remove all absorbers from the measurement field.

•

Select Tune-up.

•

Select Expert Mode.

•

Select Defective Channels.

•

Disable Automatic Detection after Editing.

•

Select Correction Tables > Tune-up. Select the affected Tune-up table.

•

Select the number of the Detector Slot.

(Detector slots containing defective channels are highlighted in red.)

•

Mark the defective channels/slices with “1”.

To activate the setting, click with the left mouse button anywhere in the defective chan- nel window. The defective channels are then highlighted in red.

•

Select Go.

•

Select Go (to save the result).

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Medical Solutions

Channel correction

3.14

(The Plexiglas strip has to be installed.)

General

0

The ChannelCorrection procedure compensates for the difference in attenuated signals from detector element to detector element. The correction has to be made for different scan parameters (e.g. kV, slice width, etc.) as well as the density of the absorbers and the path covered within an absorber. For this reason, head and body absorbers are used when determining the correction tables. The correction tables comprise linear and square root parts.

NOTE To avoid that incorrect adjustment values are created during tune up, only phantoms delivered with the CT system may be used for system adjustments.

Also the water phantom has to have the same temperature as that in the examination room.

Procedure

0

•

Select Tune-up.

•

Select Expert Mode.

•

Select Channel Correction.

•

Switch on check (a check measurement is performed).

•

Click select all (all modes are selected).

•

Select Go.

•

Insert the CCR body phantom according to the program instructions. Move the phan- tom into the slice plane so that the START mark on the phantom corresponds to the light beam of the interior light marker.

•

Select Go.

•

Press START.

•

After the CCR body correction has been made, insert the CCR head phantom accord- ing to the program instructions.

Fig. 8: Channel correction phantom (head)

•

Select Go.

•

Press START.

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Medical Solutions

Air calibration

3.15

(The Plexiglas strip has to be installed.)

General

0

The channels of the measurement system have different levels of sensitivity that are com- pensated for by Air Calibration. Air calibration consists of two major steps, base calibra- tion and difference calibration.

The objective of base calibration is to determine the changes in sensitivity caused by present environmental conditions. For this reason, base calibration has to be performed on a daily basis. This function is selected automatically when the system is switched on. In addition, the customer can run base calibration under “Setup > Calibration”, as required.

The objective of the difference calibration procedure is to determine the structural differ- ences in sensitivity for the various scan modes (kV, mA, slice width, rotation time, etc.). For this reason, difference calibration tables are generated during tune-up only.

Air calibration checks whether an absorber is in the X-ray beam. If the message indicates “There may be an object in the scan field...” although no absorber is in the X-ray beam, the reason could be contrast on the plexi strip, a defective channel, or the adjustment of the collimator box (ZAdjust).

With softwware version VB15, wait times between the KV steps are no longer required.

Procedure

0

•

Remove all absorbers from the measurement field.

•

Select Tune-up.

•

Select Expert Mode.

•

Select Air Calibration.

•

Click select all (all modes are selected)

•

Select Go.

•

Press START.

Spacing correction

3.16 (The Plexiglas strip has to be installed.)

General

0

This procedure is used to correct the equidistance (mechanical) behavior of the single detector elements. These so-called "spacing errors" can result in visible artifacts in tomo- grams.

The Spacing correction mathematically equalizes the different distances of the single detector elements. For this reason, a spacing correction table is created to compensate for spacing errors during image reconstruction.

NOTE To avoid that incorrect adjustment values are created during tune up, only phantoms delivered with the CT system may be used for system adjustments.

Also the water phantom has to have the same temperature as that in the examination room.

Procedure

0

•

Position the spacing phantom in the measurement field.

Fig. 9: Spacing phantom

•

Select Tune-up.

•

Select Expert Mode.

•

Select Spacing.

•

Click Select all.

•

Select Go.

•

Press START.

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Medical Solutions

Water Scaling

3.17

(The Plexiglas strip has to be installed.)

General

0

The density of water is defined as 0 HU on the Hounsfield scale. To ensure this condition, each measurement value is multiplied by a scaling factor during pre-processing. These scaling factors are determined via the WaterScaling procedure function. The scaling fac- tors have to be generated for each scan parameter (kV, slice width, etc.).

NOTE To avoid that incorrect adjustment values are created during tune up, only phantoms delivered with the CT system may be used for system adjustments.

Also the water phantom has to have the same temperature as that in the examination room.

Procedure

0

•

System phantom: Position the slice thickness phantom in the measurement field so that the light beam of the interior light markers is centered above the crossover point on the slice phantom.

Fig. 10: System phantom

Pos. 1 Crossover point

•

Select Tune-up.

•

Select Expert Mode.

•

Select Water Scaling.

•

Click select all (modes).

•

Select Go.

•

Press START.

Final work

3.18

Screen shot

0

Fig. 11: Final work

Quality assurance

0

•

Select Quality Assurance in the main menu of the Service Software.

•

Perform the Quality Constancy test.

Backup

0

•

Select Backup & Restore in the main menu of the Service Software.

•

From Command, select Backup.

•

From Drives, select a backup media or drive, e.g. [-R-] CD-R.

•

From Packages, select CT-Scanner and click Go.

•

Wait until "Ready" appears in the status line.

•

From Packages, select SW-Settings02 and click Go.

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Medical Solutions

4-

4Spirit / Spirit Power: Collimator adjustments

Mechanical adjustment of the slotted plate in the collimator box

0

Safety

0

NOTE Read and observe the safety information contained in the "Safety information" section of this document.(Safety Information / p. 8)

General

0

Procedure

0

•

Switch off the gantry and secure it against unintended switch-on.

•

Remove the gantry’s front covers and front funnel.

•

Move the tube into the 6 o’clock position.

•

Engage the mechanical rotation brake.

Fig. 12: Collimator adjustment tool

Remark:

To mechanically adjust the slotted plate in the collimator box, the collimator adjustment tool (part no. 38 12 604) is required.

(Additional information: The collimator adjustment tool is a part of the spare part collimator box).

Tube

A

1 2

₄

6

5

Fig. 13: Collimator box

Pos. 1 Pivot screw Pos. 2 Large wheel

Function description:

The slotted plate of the collimator box is adjusted in parallel to allow the slotted plate to be moved about the pivot screw (rotation point).

The slotted plate is pulled toward the front of the gantry by a spring inside the collimator box (the large wheel of the adjustment screw is turned counter- clockwise).

The slotted plate is pushed toward the back of the gantry by turning the large wheel clockwise.

Fig. 14: Attach the adjustment tool

•

Preparation: Turn the adjustment pin (1/Fig. 15 / p. 50) of the collimator adjustment tool back to a length where the pin does not touch the slotted plate of the collimator.

•

Attach the collimator adjustment tool with three screws on the right side of the collimator box (torque: 3 Nm, ±10%). Tube

A

1 2

₄

6

5

3

3

1 2 Tube

A

1 2

₄

6

5

3

3

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Medical Solutions

Fig. 15: Adjustment procedure (a)

Pos. 1 Adjustment pin Pos. 2 Large wheel Pos. 3 Small wheel

•

Turn the small adjustment wheel (Pos. 3) clockwise, until the adjust- ment pin contacts the slotted plate of the collimator and the friction clutch of the small wheel is activated (free run).

•

To tighten the adjustment pin to the collimator with the correct torque, turn the large wheel by 1 unit (= 10µm) clockwise (Pos.2).

Fig. 16: Adjustment procedure (b)

Pos. 1 Left screw Pos. 2 Pivot screw

•

Loosen the pivot screw (Pos. 2) by 1 turn.

•

Loosen the left screw (Pos.1, M3 hex-socket) by 1 turn. Tube

A

1 2

₄

6

5

3

3

1 2 3 Tube

A

1 2

₄

6

5

3

3

1 2

T

•

Tighten the three screws, (1/Fig. 16 / p. 50) and (1/Fig. 17 / p. 51), crosswise (torque: 1.3 Nm ±10%).

•

Tighten the pivot screw (torque: 0.62 Nm ±10%) (2/Fig. 16 / p. 50).

•

Release the adjustment pin from the slotted plate. (Turn the large wheel of the adjust- ment tool approx. (2/Fig. 17 / p. 51) four turns counterclockwise).

•

Remove the collimator adjustment tool (Fig. 14 / p. 49) from the gantry.

•

Release the mechanical rotation brake.

•

Switch on the gantry.

•

Check the new adjustment of the slotted plate. (Note: The ZAdjust procedure is still running.) Select Go.

If the message:

“The adjustment of the tube collimator is out of range“ appears,

select Cancel and repeat the mechanical adjustment procedure again. If the message:

“Found tube collimator DISPLACEMENT ... (Tolerance ± 15µm)“ appears, select Start rotation in the window:

“The gantry covers are open. Are you sure nobody is inside?“ The Z-adjustment procedure continues.

•

After the Z-adjustment procedure has completed, select Go (to save the results).

(The message “Z-adjustment of tube collimator successfully completed“ appears.)

•

Secure the adjustment screws with Loctite #243 (Secure the adjustment screws with Loctite #243 / p. 52).

Fig. 17: Adjustment procedure (c)

Pos. 1 Right screws Pos. 2 Large wheel

•

Loosen the two right screws (Pos.1, M3 hex-socket) by 1 turn.

•

Now turn the large wheel of the adjustment tool (Pos. 2), according to the distance (micrometer) and the direction (clockwise or counterclock- wise) calculated with the Z-adjust program. Important! Please note: 10 micrometer = 1 unit (segment) on the collimator adjustment tool (Example: 40µm = 4 units). Tube

A

1 2

₄

6

5

3

3

2 1

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Medical Solutions

Secure the adjustment screws with Loctite #243

0

•

Switch off the gantry and secure it against unintended switch-on.

•

Move the tube into the 6 o’clock position.

•

Engage the mechanical rotation brake.

•

Secure the four screws of the slotted plate (including washers) with Loctite #243 (1, 2/Fig. 16 / p. 50) / (1/Fig. 17 / p. 51).

•

Release the mechanical rotation brake.

•

Wait 10 minutes for the Loctite to harden. (In the meantime, the front funnel and front covers of the gantry can be installed).

•

Switch on the gantry.

General

0

Safety

0

NOTE Read and observe the safety information contained in the "Safety information" section of this document. (Safety Information / p. 8)

Phantoms

0

NOTE Only the original phantoms (delivered with the system) can be used.

The vertical and horizontal positioning of the phantom is per- formed automatically at a predefined table height. For this reason, only the original phantom holder (delivered with the system) can be used.

Phantom holder for Emotion 6/16 (2007):

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Page 54 of 104

Medical Solutions

Sequence for complete system tune-up

5.1

For this sequence, an automated guided tour is available (partially).

•

Entry of system configuration

•

Select Tune-up.

•

Select Expert Mode.

•

Select RotSpeed.

•

Select GenOsc.

•

Select Getter.

•

Select ZAdjust.

•

Select FocusAli.

•

Insert plexi strip

•

Select GenAdapt.

•

Select Table Generation.

The following tune-up steps are selected automatically, one after the other: - Insert plexi strip (already inserted)

- Defective channels - Channel correction - Air Calibration - Spacing - Water Scaling

•

Quality test

•

Save tables

Sequence in case of poor image quality

5.2 For this sequence, an automated guided tour is available (partially).

•

Select Tune-up.

•

Select Expert Mode.

•

Select ZAdjust.

•

Select FocusAli.

•

Insert plexi strip

•

Select GenAdapt.

•

Select Table Generation.

The following tune-up steps are selected automatically, one after the other: - Insert plexi strip (already inserted)

- Defective channels - Channel correction - Air Calibration - Spacing - Water Scaling

•

Quality test

•

Save tables

Emotion (2007) / Spirit CT02-025.817.02.02.02 Siemens AG

06.07 SSME CS

Page 56 of 104

Medical Solutions

In document FACULTAD DE GEOGRAFÍA E HISTORIA (página 78-82)