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Gold Fiducial Markers for EBRT
Gold Fiducial Markers for EBRT
Gold Fiducial Markers
Gold Fiducial Markers
e.g. Prostate
e.g. Prostate
Intention
Intention
1. Approach to a solution
1. Approach to a solution
But the main question is: Where is the Prostate
But the main question is: Where is the Prostate
Where is the Prostate
Where is the Prostate
Field edge variability during several treatment sessions
Field edge variability during several treatment sessions
Motion of the prostate
Motion of the prostate
Approach to a solution: IGRT
Approach to a solution: IGRT
Approach to a Solution: Navigation aid = Marker
Approach to a Solution: Navigation aid = Marker
Why Gold
Why Gold
What is a gold marker and how does it look like
What is a gold marker and how does it look like
Marker Kit
Marker Kit
Positioning of the Marker
Positioning of the Marker
How many markers are needed
How many markers are needed
Where to place the markers
Where to place the markers
Images
Images
Images
Images
Images
Images
How will the Markers implanted
How will the Markers implanted
Procedure (one possible scenario)
Procedure (one possible scenario)
Procedure
Procedure
Procedure
Procedure
Procedure
Procedure
Conclusion
Conclusion
IGRT in pictures
IGRT in pictures
MRI and CT images with gold markers
MRI and CT images with gold markers

Презентация на тему: «Gold Fiducial Markers for EBRT». Автор: cvb. Файл: «Gold Fiducial Markers for EBRT.ppt». Размер zip-архива: 5374 КБ.

Gold Fiducial Markers for EBRT

содержание презентации «Gold Fiducial Markers for EBRT.ppt»
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1 Gold Fiducial Markers for EBRT

Gold Fiducial Markers for EBRT

2 Gold Fiducial Markers

Gold Fiducial Markers

Are used for soft tissue target volume localization and verification in external beam radiation treatment procedures like - IMRT 3D-confomal irradiation - CyberKnife or GammaKnive procedures - or even Brachytherapy It might be used in organs like - Prostate - Liver - Pancreas - Brain

3 e.g. Prostate

e.g. Prostate

EBRT nowadays is seen as one standard treatment for localized and advanced prostate cancer patients. Prostate cancer is a multifocal tumor which causes the whole organ to be treated. The organ will be irradiated with homogeneous fields in 3D conformal technique or with IMRT. Toxicity to bladder and rectum are limiting the dose to the organ to 72 Gray with regular irradiation procedures. This table shows that higher doses are giving more local control.

5 year survival rate w/o PSA rise depending on applied dose

5 year survival rate w/o PSA rise depending on applied dose

5 year survival rate w/o PSA rise depending on applied dose

5 year survival rate w/o PSA rise depending on applied dose

5 year survival rate w/o PSA rise depending on applied dose

5 year survival rate (%) w/o PSA rise

5 year survival rate (%) w/o PSA rise

5 year survival rate (%) w/o PSA rise

Dose

64.8 – 70.2 Gy

75.6 Gy

81 – 86.4 Gy

p

Risk Group

Low risk

65

86

96

< 0.01

Intermediate. risk

44

61

87

< 0.01

High risk

22

43

69

< 0.01

Source: Zelefski, Sloane Kettering CC, NY, NY

Risk factors: ? T2, Gleason Score ? 7, PSA ? 10ng/ml. Low Risk = no risk factor; intermediate. Risk = 1 risk factor; high risk = ? 2 risk factors.

Risk factors: ? T2, Gleason Score ? 7, PSA ? 10ng/ml. Low Risk = no risk factor; intermediate. Risk = 1 risk factor; high risk = ? 2 risk factors.

Risk factors: ? T2, Gleason Score ? 7, PSA ? 10ng/ml. Low Risk = no risk factor; intermediate. Risk = 1 risk factor; high risk = ? 2 risk factors.

Risk factors: ? T2, Gleason Score ? 7, PSA ? 10ng/ml. Low Risk = no risk factor; intermediate. Risk = 1 risk factor; high risk = ? 2 risk factors.

Risk factors: ? T2, Gleason Score ? 7, PSA ? 10ng/ml. Low Risk = no risk factor; intermediate. Risk = 1 risk factor; high risk = ? 2 risk factors.

4 Intention

Intention

Goal: High dose to the target volume, low toxicity to the organs at risk. But: The organs at risk are adjecent to the target volume.

5 1. Approach to a solution

1. Approach to a solution

The irradiated volume should be similar to the shape of the organ to be treated (conformal). 3D – conformal irradiation should be the standard. Better but more complex: IMRT Intensity Modulated Radiation Therapy

Fast moving leafs made from lead and controlled by a computer and shaping the beam from a LINAC. The so called Multi Leaf Collimator. Whit this system the contour of the beam can be shaped according to the shape of the organ at the respective angle of the radiation field.

Source: Prof. D. Aebersold, Bern

6 But the main question is: Where is the Prostate

But the main question is: Where is the Prostate

Motion of the prostate during a 17 days cycle

7 Where is the Prostate

Where is the Prostate

Organ motion and therefore geographic miss is a major problem when irradiating the prostate. Hence a bigger target volume has to be irradiated. But larger sections of the organs at risk will be irradiated as well. This might lead to increasing toxicity rates.

8 Field edge variability during several treatment sessions

Field edge variability during several treatment sessions

Setup error of treatment sessions

9 Motion of the prostate

Motion of the prostate

Motion of the prostate might be induced by - Tension of the pelvis muscles, - Bowel and bladder filling - Breathing A cranial-caudal und ventral-dorsal misplacement of up to 2cm was observed. Therefore conventional treatment scemes aks for a 1 – 2 cm margin around the organ. Aside from that the prostate is shrinking during the treatment. Low margin ? low toxicity but at the risk not hitting the whole organ during each fraction ? local control ?? Big margin ? organ will be hit easily, but to save bladder and rectum the overall dose has to be reduced ? local control ??

10 Approach to a solution: IGRT

Approach to a solution: IGRT

IGRT Image Guided Radiation Therapy Radiation Therapy with image guidance in intended to localize and adjust the target volume. The image is obtained by an on board imaging system (OBI). Today this can be a flat panel sensor with MV or kV imaging, extra portal imaging or cone beam CT. BUT: The prostate itself is hardly seen on x-ray images. And bony structures might not be a reliable aid.

Motion of the prostate versus bony structures

11 Approach to a Solution: Navigation aid = Marker

Approach to a Solution: Navigation aid = Marker

The marker should provide a reliable and reproducible localization of the prostate. The marker should be easily seen with the OBI of the LINAC. The marker has to be of a radio opaque material. E.g. gold, tungsten, silver etc., sometimes carbon. It has to be biocompatible.

Flouro refrence

LINAC OBI

12 Why Gold

Why Gold

Gold does not react with the body. Gold is not causing any allergies. Gold provides a good visibility under x-ray and gamma-rays.

13 What is a gold marker and how does it look like

What is a gold marker and how does it look like

Generally gold markers are small cylinders or balls made of gold. Most commonly used sizes vary from 0,8 to 1,2 mm in diameter and 3 to 5 mm in lenght . Other dimensions might be used in special cases. Goldmarker also can be made of thin goldsprings or small beads on a suture.

14 Marker Kit

Marker Kit

The marker will be delivered sterile preloaded in a 20 cm needle blocked with bone wax or a synthetic spacer at the front end. It comes in sterile pouch ready for the implant.

15 Positioning of the Marker

Positioning of the Marker

To prevent the marker from migration or dislocation it has to be implanted in the organ. Skin marker or patient immobilisation are unsufficient means.

16 How many markers are needed

How many markers are needed

Usually three markers will be implanted In some special cases four markers might be neccessary. This adds extra confidence and might help in case of difficult bony conditions. Two markers are insufficient.

17 Where to place the markers

Where to place the markers

Three markers will be place like One at the Base one at the Apex and one most lateral in the middle of the gland. OR: One on the left side at the base, one on the right side of the base and one under the urethra at the apex. The markers have to be placed inside the gland 3 to 5 mm away from the capsule. The actual position of the markers is not as important as the positioning at the maximum distance from each other.

18 Images

Images

Base – Middle – Apex

19 Images

Images

4 Markers; Base – Base – Middle – Middle

20 Images

Images

Base – Base – Apex

21 How will the Markers implanted

How will the Markers implanted

In many places the implant is performed by the Urologist under Ultrasound conrol. Usually he uses the biopsy channel of the rectal ultrasound probe to insert and visualize the needle. The implant is done through the rectal wall. Some centers do have the equipment (stand, stepper, template grid) to perform a perineal insertion. This is more accurate but might cause a general anesthesia of the patient.

22 Procedure (one possible scenario)

Procedure (one possible scenario)

In collaboration with the Urologists there will be a ultrasound guided implant of the Markers one or two weeks before the treatment planning starts. With the localization of the Markers in the planning CT, the simulation and the daily treatment sessions the actual prostate position can be detected and the LINAC bed coordinates can be adjusted. This is the so called organ tracking. Before each treatment session a control image is obtained and is matched with the reference image. Prostate displacement will be compensated by moving the treatment bed according to the calculated geographic miss.

23 Procedure

Procedure

Implant of the marker by the Urologist in the urologists office or hospital. Reference image for treatment planning and aquisition of the marker position Postioning of the patient on the bed of the LINAC on the first treatment day.

24 Procedure

Procedure

Aquisition of the images, Each day in two orthogonal planes to detect the geographical miss. Modern LINACS offer a diagnsotic x-ray unit in a 90° angle to the LINAC. This gives the possibilty to create x-ray images or even CT scans before the treatment starts.

Digitally reconstructed x-ray image as reference for the marker position (A) calculation of the correction with a gold marker image from the LINAC.

25 Procedure

Procedure

Calculation of the mismatch Modern systems offer the possibility match the actual image with the reference image. The actual image will be aligned with the reference image on the computer monitor and the system generates the coordinates for the movement of the patients bed. Correction of the bed Modern systems do have a remote controlled bed. So compensation of the patient dislocation can be performed in an easy and fast way. Extra dose for imaging stays low. Irradiation Now the irradiation can start as usual. This localization and compensation procedure will be performed each day before each fraction.

Mismatch

Match

26 Conclusion

Conclusion

The prostate will be hit safely and reproducible during each treatment session. Therefore a preferably high dose can be applied to the target volume. Increase in local tumor control rate. Decrease in toxicity.Die Nebenwirkungsrate wird verringert. Or: With similar toxicity the local control can be increased.

27 IGRT in pictures

IGRT in pictures

Increased conformity and better dose distribution by means of IMRT. Excellent match of the 95% iso dose level (blue area) with the target volume (red line). The black arrows show the implanted gold markers.

Gold marker

Quelle: PIRUS GHADJAR, DANIEL M. AEBERSOLD

28 MRI and CT images with gold markers

MRI and CT images with gold markers

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